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6th Workshop on Nuclear Fission and Spectroscopy of Neutron-Rich Nuclei

ABSTRACTS

Workshop sponsored by:


Programme

Abstracts (oral: by sessions, posters: in alphabetical order of presenting authors)

List of contributions

List of participants

Organizers

Aurelien Blanc, Michael Jentschel, Ulli Köster, Caterina Michelagnoli, Paolo Mutti, ILL

Andrei Andreyev, University of York / JAEA

Olivier Serot, CEA Cadarache

Gilbert Belier, CEA Bruyères-le-Châtel

Grégoire Kessedjian, LPSC Grenoble

Assistants

Valérie Duchasténier & Laurence Tellier (Institut Laue-Langevin, Grenoble, France)

Programme

Monday 20 March Speaker* eligible for young scientist award

9:00-12:00 Visits of ILL experimental hall $ eligible for poster award

12:00 Lunch

Session 1 - Chair Friedrich Goennenwein13:30 Welcome and introduction of ILL Helmut Schober13:50 The LOHENGRIN spectrometer & V4 Ulli Köster14:05 The GAMS high resolution gamma ray spectrometer Michael Jentschel14:20 Ultracold neutrons (UCNs) at the ILL Peter Geltenbort14:30 High energy gamma rays from fission measured at PF1b Katsuo Nishio14:45 The EXILL setup Aurelien Blanc15:00 Overview of the EXILL campaign Silvia Leoni

15:20 Coffee break

15:35 The ultrafast timing method and the EXILL-FATIMA campaign Jean-Marc Regis

15:55 Lifetime measurements close to phase transition in neutron rich A~100 nuclei Saba Ansari*16:10 The FIPPS instrument Caterina Michelagnoli16:25 Organisational information

16:35 Departure of first bus to Chamrousse

16:30-17:30 Visits of ILL experimental hall

17:30 Departure of second bus to Chamrousse

17:30 Arrival of first bus in Chamrousse, check-in at hotel18:30 Arrival of second bus in Chamrousse, check-in at hotel

19:00 Dinner at Restaurant Le Bachat


Tuesday 21 March Speaker

* eligible for young scientist award8:00-8:30 Breakfast at Restaurant Le Bachat

Session 2A - Chair Herbert Faust08:30 Opening of workshop08:40 Shells, Anti-shells and Modes in Nuclear Fission Friedrich Goennenwein09:10 High-precision measurement of isotopic yields in the fission of 236U* Laurent Audoin

09:25Fission in the neutron-deficient lead region: the synergy of beta-delayed, Coulex-induced and fusion-fission methods Andrei Andreyev

09:50 Fission Dynamics: is nuclear viscosity dependent on the temperature? Emanuele Vardaci10:05 Direct Observation of slow fission from width of K x-ray line Amlan Ray

10:20-10:50 Coffee break

Session 2B - Chair Katsuhisa Nishio10:50 Infuence of scission neutrons on fission observables Olivier Serot11:10 Neutron emission anisotropy in fission Louise Stuttgé

11:25 Prompt fission neutron multiplicities and their excitation-energy dependence Ali Al-Adili

11:40Measurements of the Prompt Fission Neutron Spectrum at LANSCE: The Chi-Nu Experiment Keegan Kelly*

11:55 Impact of nuclear inertia momenta on fission observables Pierre Tamagno*12:10 Impact of FIFRELIN input parameters on fission observables Abdelaziz Chebboubi*12:25 End of session

Lunch break and free afternoon


Session 3 - Chair Diane Doré

17:00 Independent fission product yields from 235U(nth,f) measured with SPIDER Fredrik Tovesson

17:25Measuring correlated fission observables in Cf-252 with the VERDI spectrometer Kaj Jansson*

17:40 Recent developments of the FALSTAFF experimental setup Andreina Chietera*

17:55Total Kinetic Energy and Fragment Mass Distributions from Fission of Th-232 and U-233 Daniel Higgins

18:10Isotopic distribution and dependency to fission product kinetic energy for 241Pu thermal neutron-induced fission Sylvain Julien-Laferriere*

18:25Application of Calorimetric Low-Temperature Detectors for the Investigation of Z-yield Distributions of Fission Fragments Santwana Dubey*

18:40 Can low-energy fission produce three heavy fragments? Ulli Köster18:55 End of session



Wednesday 22 March Speaker

* eligible for young scientist award8:00-8:30 Breakfast at Restaurant Le Bachat $ eligible for poster award

Session 4A - Chair Matthew Devlin08:30 Fission study using multi-nucleon transfer reaction at JAEA tandem Nishio Katsuhisa

08:55First simultaneous measurement of fission and gamma probabilities of 237U, 238Np and 239Np via surrogate reactions Paola Marini

09:15Use of active scintillating targets in nuclear physics experiments - measurement of spontaneous fission Gilbert Belier

09:30First Results on 238U(n,f) Prompt Fission Neutron Spectra from 1 to 800 MeV incident neutron energy Paola Marini$

09:35 Tests of ionisation chambers for photofission experiments Marius Peck$

09:40Characterization of a Coaxial Ionization Chamber with a ToF Section for Fission Fragment Spectroscopy at Lohengrin Nikolay Sosnin$

09:45 Refractory Beams at ISOLDE – A concept for a fission recoil target Jochen Ballof$

09:50Summation calculation of delayed neutron yields for U235, U238 and Pu239, based on various fission yield and neutron emission probability database Daniela Foligno$

09:55Gamma-ray cascade study in Kr and Ba fission fragments with the EXILL experiment Michal Rapala$

10:00Fast-timing measurements in neutron-rich odd-mass zirconium isotopes using LaBr3:Ce detectors coupled with Gammasphere Eugenio Gamba$

10:05-10:40 Coffee break with poster session

Session 4B - Chair Andrei Andreyev10:40 Discovery of Elements 113 - 118 Roman Sagaidak11:10 Physics avenue with S3 Herve Savajols11:30 Charting Terra Incognita at Alto and S3 Serge Franchoo

11:45 Recent progress on the study of nuclear fission using laser spectroscopy Kieran Flanagan12:10 Prompt fission gamma rays and their angular distributions Andreas Oberstedt12:25 End of session

Lunch break and free afternoon


Session 5 - Chair Silvia Leoni17:00 Nuclear Structure of SHN – State of the Art and Perspectives at S3 Dieter Ackermann

17:30The gamma-ray spectroscopy studies of low-spin structures in 210Bi and 206Tl using cold neutron capture reactions Natalia Cieplicka-Orynczak*

17:45Application of BEGe detectors and LN2 cooled Si(Li) detectors for studies of isotopes with large density of excited states at low energy Martin Venhart

18:00 Preparation of radioactive lanthanide targets for nuclear physics experiments Stephan Heinitz

18:15Measuring neutron capture rates on ILL-produced unstable isotopes (79Se, 147Pm, 163Ho, 171Tm, 204Tl) for nucleosynthesis studies Jorge Lerendegui Marco*

18:30 Nuclear Structure with radioactive muonic atoms Elisa Rapisarda18:50 Delayed gamma spectroscopy of identified fission fragments Laurent Gaudefroy19:05 End of session



Thursday 23-mars-17

8:00-8:30 Breakfast at Restaurant Le Bachat

Session 6A - Chair Bogdan Fornal

08:30 Lifetime measurements in neutron-rich Xe isotopes

08:50 Study of parity-doublet structure in the 147La nucleus.

09:05 The first signs of collectivity in the nuclei above 132Sn core

09:20 New nuclear structure data after fission

09:35 Neutron-rich isotopes from 238U(n,f) and 232Th(n,f) studied with the nu-ball γ-ray spectrometer coupled to the LICORNE neutron source

09:50 Coulomb excitation of refractory fission fragment beams

10:15 End of session

10:15-10:45 Coffee break with poster session

Session 6B - Chair Thorsten Kroell

10:45 Decay of neutron-rich Cd and In studied with GRIFFIN at TRIUMF-ISAC

11:10 Beta-delayed neutron spectroscopy of 132Cd

11:25 High-precision mass measurements of neutron-rich nuclei

11:40 γ-ray spectroscopy of neutron rich Ag isotopes: πg9/2 n × νh11/2 m structure and triaxiality

11:55 Low-energy quadrupole and dipole strengths in 116,118,120Sn deduced from neutron capture reactions

12:10 QRPA with the Gogny force: a unique formalism to describe low and high energy spectroscopy and beta decay of fission fragments


Lunch break

Session 7 - Chair Wolfram Korten

13:45 Fast timing results from EXILL&FATIMA in the neutron rich region below Z=40

14:05 Nuclear structure across neutron-rich N=60 using Coulomb excitation of radioactive ion beams

14:20 Spectroscopy of neutron-rich 94,96Y isotopes produced in fission induced by cold neutrons

14:35 Shape coexistence in 96,98Sr

14:50 Spin-alignment in abrasion-fission reaction - g-factor measurement of isomeric states

15:05 Identification of Excited States and Collectivity of 88Se

15:20 Collectivity in the vicinity of 78Ni: Coulomb excitation of neutron-rich Zn at HIE-ISOLDE

15:35 Shell-model study of Gamow-Teller and first–forbidden β decay in the N=28 region

15:55 Valence particle – core excitations couplings: new experimental investigations and a novel theoretical approach


16:30 Start of snowshoe walk to Croix de Chamrousse (alternatively by bus and cable car)

19:30 Conference dinner at La Croix de Chamrousse

6th Workshop on Nuclear Fission

and Spectroscopy of Neutron-Rich Nuclei

Friday 24 March Speaker

8:00-8:30 Checkout appartments8:30-9:00 Breakfast at Restaurant Le Bachat

Session 8A - Chair Peter Egelhof

09:00High-statistics reactor antineutrino experiments for fission and beta-decay studies Alain Letourneau

09:20Precisely Measured Electron Spectra from Fission Products, the Missing Piece in the Reactor Antineutrino Puzzle Alejandro Sonzogni

09:40Modular Total Absorption Spectrometer the powerful array to study the beta-strength and anti-neutrino properties Marzena Wolinska-Cichocka

10:00 Fission studies at VAMOS Fanny Farget


Session 8B - Chair Fanny Farget

10:50Fission study project in RIKEN RIBF: towards the “complete” measurement of fission observables Masaki Sasano

11:10 Gamma-beam photofission experiments at ELI-NP: The future is emerging Dimiter Balabanski11:30 Closing of workshop


12:00Departure of first bus (connects in Grenoble to 13:30 airport busses to Lyon and Geneva)

16:45 Departure of second bus (connects in Grenoble to 18:00 airport bus to Lyon)


Oral contributions

Tuesday, March 21, 2017

Shells, Anti-Shells and Modes in Nuclear Fission

F. Gönnenwein University of Tübingen, Tübingen, Germany [email protected] Abstract: A tour d`horizon to phenomena in fission is proposed where fragment properties play a decisive role. Beyond Liquid Drop the most relevant property of fragments in this context are nuclear shell effects. They influence on fragment mass and charge yields, deformabilities, fragment kinetic and excitation energies. Most often shell effects are discussed as stabilizing nuclei compared to the Liquid Drop model. Thereby it is forgotten that shell effects can in contrast have a destabilizing effect. To help avoid mistakes it is for the present discussion suggested to distinguish between shell and anti-shell effects in the two cases. Fragment shells and anti-shells lead to fission modes. Historically the Turkevich-Niday modes were introduced to distinguish between symmetric and asymmetric fission. It is established that these modes bifurcate in the 2nd minimum of the double-humped fission barrier and pass over saddle points differing in height. In asymmetric fission of actinides the fine structures of fragment mass and energy distributions are further interpreted in terms of Brosa modes, and in fission of pre-actinides as Itkis modes. For heavy actinides mass asymmetry in the actinides switches to symmetric fission. Again a fine structure appears addressed as Hulet modes. The question where these fine structure modes are formed is still at issue. In the present survey of experimental evidences it is shown that surprisingly the comparison of fragment angular distributions in above-barrier and sub-barrier fission may help to solve the issue. The conclusion is reached that the fine structure modes are formed beyond the saddle point of fission in the descent towards scission. This was already suggested by Brosa as an option.

High-precision measurement of isotopic yields in the fission of 236

U*

Laurent Audouin

1) Université Paris-Sud, France

audouin@ipno,in2p3,fr

The isotopic yields of 236

U*, obtained after identification in mass and charge of both fission

fragments, have been measured with unprecedented resolution at GSI using the SOFIA2 setup

and the inverse kinematic method. Prompt neutron yields and total kinetic energies have also

been obtained. After an overview of the experimental method and of the fission-triggering

method, we will discuss the results and compare them to nuclear databases and to other

experimental data. In particular, the combination of these results with the previous SOFIA1

data obtained on 234,235,238

U* allows for a detailed description of the influence of the neutron

numbers on the fragments distributions.

Fission in the neutron-deficient lead region: the synergy of beta-delayed, Coulex-induced and fusion-fission methods

A.N. Andreyev1,2 On behalf of York-Bordeaux-Bratislava-Leuven-Mol-Tokai Collaboration

1) Department of Physics, University of York, York, United Kingdom, YO105DD 2) Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan [email protected] Abstract: In the last two decades, through technological, experimental and theoretical advances, the situation in experimental low-energy fission studies has changed dramatically. With the use of advanced production and detection techniques, much more detailed fission information can be obtained for traditional regions of fission research and, very importantly, new regions of nuclei have become accessible for fission studies. This contribution will review the recent fission experiments in very neutron-deficient nuclei in the lead region, spanning from Pt to Bi isotopes. Three complementary methods of fission studies in this region will be discussed: low-energy beta-delayed fission [1,2,3] and Coulex-induced fission [4], and higher-energy fusion-fission reactions induced by charged particles [5,6,7]. Recent theoretical efforts in respect of low-energy fission calculations in this region of nuclei will also be reviewed. 1. A. N. Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010) 2. L. Ghys et al., Phys. Rev. C90, 041301(R) (2014) 3. A.N. Andreyev, M. Huyse, P. Van Duppen, Rev.Mod. Phys., 85, 1541 (2013) 4. J.-F. Martin et al, Eur. Phys. J. A51, 174 (2015) 5. K. Nishio et al. Phys. Lett. B, 748, 89 (2015) 6. E. Prasad et al., Phys. Rev. C 91, 064605 (2015) 7.R. Tripathi et al., Phys. Rev. C 92, 024610 (2015)

Fission Dynamics: is nuclear viscosity dependent on the temperature?

E.Vardaci1, A. Di Nitto2, P. Nadtochy3 ,G. La Rana1, M. Cinausero4, G. Prete4, N. Gelli5, E.M. Kozulin6 ,G.N. Knyazheva6, I.M. Itkis6

1) Dipartimento di Fisica “E. Pancini”, Università di Napoli “Federico II”, Napoli, Italy 2) Johannes Gutenberg-Universität Mainz, Mainz, Germany 3) Omsk State Technical University, 644050 pr. Mira 11, Omsk, Russia 4) Laboratori Nazionali di Legnaro, INFN, Legnaro, Italy 5) Istituto Nazionale di Fisica Nucleare, Sesto Fiorentino (Firenze), Italy 6) Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia Email: [email protected] Abstract: It is well known that nuclear viscosity plays a fundamental role in the fission process [1]. Experimental evidence that fission is driven by nuclear viscosity has come from the observation of prescission multiplicities of neutrons, charged

particles and -rays significantly larger than those predicted by the statistical model. Much experimental and theoretical work has been devoted to this subject but nevertheless many questions still remain open. They are mainly related to the precise determination of the fission time scale as well as to the nature of the dissipation and its dependence on the nuclear shape and temperature.

On the experimental ground we have stressed out the importance of measuring a wide set of observables in order to effectively constraint the parameters of the various models. This has been accomplished by extending the study to

systems of intermediate fissility (A150) [2,3]. On the theoretical ground, our collaboration has greatly improved the implementation of a dynamical model based on the 3D Langevin approach by including into the code an event-by-event treatment of the light charge particle evaporated during the deexcitation processes of the compound nucleus. The 3D model uses two prescriptions for the nuclear dissipation: one-body and two-body dissipation [4,5]. The dependence of nuclear dissipation on the deformation has been found in agreement with one-body dissipation model [4].

In this contribution we will propose a journey within the open questions about the current use of a temperature dependent nuclear viscosity in nuclear fission and we will discuss recent experimental results. [1] K. T. R. Davies et al., Phys Rev. C 13, 2385 (1976). [2] E. Vardaci et al, Eur. Phys. J. A 43, 127 (2010). [3] A. Di Nitto et al, Eur. Phys. J. A 47, 83 (2011). [4] E.Vardaci et al, Phys.Rev. C92, 034610 (2015). [5] P.N. Nadtochy et al, Physics Letters B 685, 258 (2010)

http://www.nndc.bnl.gov/nsr/fastsrch_act2.jsp?aname=A.Di+Nitto

http://www.nndc.bnl.gov/nsr/fastsrch_act2.jsp?aname=E.Vardaci

Direct Observation of Slow Fission From Width of K x-ray Line

A. K.Sikdar1, A. Ray1*, Deepak Pandit1, A. De2 and A. Chatterjee3

1) Variable Energy Cyclotron Centre, Kolkata, India

2) Raniganj Girls’ College, Raniganj, Bardhaman, India

3) Inter University Accelerator Centre, New Delhi, India *Email.of.corresponding.author: [email protected] Abstract: The timescale of nuclear fission of highly excited fissile nuclei is a basic characteristic of the underlying fission dynamics. We have used a novel atomic technique based on the measurement of intrinsic width of K x-ray lines of the element produced by fusion to directly measure their average fission time from the quantum uncertainty principle. Highly excited plutonium nuclei were produced by the fusion of 4He+238U at E(4He)Lab=60 MeV. Solar cell detectors subtending solid angle of 1.3 sr

were used to detect fission fragments and a LEPS subtending 28 msr solid angle

was used to detect -ray and x-ray photons. Fig. 1(a) shows prompt gated LEPS

spectrum after background and random coincidence subtraction. Fission fragment -rays appear as broad double humped peaks and the corresponding GEANT3 simulations have been shown by dash blue curves. A narrow Gaussian peak (red

curve) is seen around 103 keV, indicating presence of plutonium K1 line based on

spectral shape. Fig. 1 (b) is a plot of photon multiplicity in different fission fragment energy bins having the same fission fragment cross-section. All regions of the fission fragment spectrum contribute equally to photon multiplicity around 103 keV, whereas only specific regions of fission fragment spectrum contribute to photon multiplicity around 60 keV and 90 keV, thus identifying the narrow peak around 103 keV as

plutonium K1 line. The widths of plutonium K x-ray lines give fission time > 1x 10-18

sec from the quantum uncertainty principle and the fluorescence yield per fission

event shows that most of the fission events are slow (mean fission time 10-18 sec).

Fig. 1: (a) Background corrected photon spectrum in coincidence with fission fragments. (b) Plot of photon multiplicities in different fission fragment energy bins.

Influence of scission neutrons on fission observables

O. Serot1, O. Litaize1, A. Chebboubi1 1) CEA, DEN, DER, SPRC, F-13108 Saint-Paul-Lez-Durance, France [email protected] Abstract: Recently, the ‘three sources’ model proposed initially by Kornilov has been revisited in order to describe more accurately the Prompt Fission Neutron Spectrum (PFNS). In this model, neutrons that may arise during the sudden rupture of the neck (the so-called scission neutrons) are taken into account. Prompt neutrons are then assumed to be emitted from different sources and the total PFNS is described by three different components:

First component: when no scission neutron is emitted, prompt neutrons are evaporated from fission fragments with average excitation energies noted <E*L> and <E*H>, for the light (L) and the heavy (H) fragment respectively;

Second component: in the case where one scission neutron is emitted, due the energy required for its emission (noted Esc), prompt neutrons are also evaporated from fission fragments but with less available excitation energy;

Third component: This last component corresponds to the scission neutrons. The two first components are simulated with the FIFRELIN Monte Carlo code (developed at CEA-Cadarache), while scission neutrons are assumed to have a Gaussian type energy distribution. In this work, all calculations were performed in the case of the 252Cf spontaneous fission, under the constraint to reproduce both the

well-known total prompt neutron multiplicity (<>=3.76) and the average total excitation energy (<TXE>=34.2 MeV). A very nice agreement between our calculated PFNS and the Mannhart’s reference evaluation was achieved by introducing a scission neutron component of about 2%. The impact of this scission neutron component on other fission observables will be also presented: the prompt neutron multiplicity as a function of primary fission

fragment mass <>(A) and total kinetic energy <>(TKE), the prompt neutron

emission probability P() and lastly the prompt gamma characteristics.

Neutron emission anisotropy in fission L. Stuttgé1,2, A. Chietera3, F. Gönnenwein4, Yu. Kopatch5, A. Gagarski6, I. Guseva6,

M. Mutterer7, E. Chernysheva8, O. Dorvaux1, F.-J. Hambsch9, F. Hanappe10, Z. Mezentsevah5, S. Telezhnikov5

1) IPHC, Université de Strasbourg, Strasbourg, France 2) CNRS, UMR7178, 67037 Strasbourg, France 3) Irfu, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France 4) Physikalisches Institut, Universität Tübingen, 72076 Tübingen, Germany 5) Frank Laboratory of Neutron Physics, JINR, 141980 Dubna, Russia 6) Petersburg PNPI, Gatchina, Russia 7) GSI Helmhotzzentrum für Schwerioneforschung, 64291 Darmsatdt, Germany 8) Flerov Laboratory of Nuclear Reactions, JINR, 141980 Dubna, Russia 9) EC-JRC-Institute for Reference Materials and Measurements, 2440 Geel, Belgium 10) PNTPM, Université Libre de Bruxelles, 1050 Brussels, Belgium [email protected]

Abstract: Neutron experimental distributions are investigated in the spontaneous fission of 252Cf. It is well known that during the fission process the bulk of prompt neutrons is evaporated by the fully accelerated fragments. Neutron evaporation theory states that this emission is isotropic in the centre of mass of each moving fragments (C.M.), but if one compares experimental angular distributions with a pure isotropic evaporation, discrepancies appear in many different works. To understand the origin of these deviations a contribution was introduced to neutron angular distributions due to neutrons ejected at an early stage of the fission process, at the scission point. But even by adding these scission neutrons and taking into account the anisotropy effect due to the kinematic focusing, an excess of neutrons remains. So it was assumed that an anisotropy effect appears also in the C.M. of each fragment and this effect reinforces the kinematic anisotropy in the laboratory system. There are theoretical arguments and calculations that claim that this anisotropy exists, but there isn't any direct observation, because the contribution to the kinematic focusing due to the C.M. anisotropy is very weak. To show this effect a new method has been developed by our collaboration. The CORA experiment was performed for this purpose. It consists in the measurement of triple coincidences between the coincidence of the two fission fragments and two ejected neutrons. With this trick we can disentangle in the laboratory system the contribution to the anisotropy due to the kinematic focusing and the effect of the predicted C.M. anisotropy. The experiment, which gives access for the first time to both processes simultaneously, scission neutron emission and dynamical anisotropy, is described and the new analysis method and the results are presented.

Prompt fission neutron multiplicities and their excitation-energy dependence

A. Al-Adili 1, D. Tarrío 1, F.-J. Hambsch 2, A. Göök 2, K. Jansson 1, A. Solders 1, V. Rakopoulos 1, C. Gustavsson 1, M. Lantz 1, A. Mattera 1, S. Oberstedt 2, A. V. Prokofiev 1, E. A. Sundén 1, M. Vidali 2, M. Österlund 1, S. Pomp 1 1. Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden 2. European Commission, Directorate for Nuclear Security and Safety, JRC-Geel, Belgium

[email protected] Abstract: Correlation studies between fission observables are important for a successful development of nuclear fission models. Presently, nuclear data libraries lack data, especially on the evolution of fission observables as a function of incident neutron energy (En). The variation of the prompt-neutron multiplicity, ν (A), as a function of En is one of many open questions, particularly whether the additional excitation energy manifests in an increase of ν (A) for all fragments or for the heavy ones only. The few existing experimental data supports the latter, but more data are required to draw any definite conclusions. Different fission model codes follow the one or the other assumption. Also experimental data are analyzed under different assumptions on the energy-dependence of ν (A) leading to different derived mass yields. The Uppsala nuclear reactions group is working together with the JRC-GEEL on measuring ν (A) as a function of En. We aim at investigating fission of different compound systems systematically using both the 2E and the 2E-2v techniques. In the first method, prompt-fission neutrons and fission fragments are measured in coincidence by using liquid scintillators in conjunction with a twin Frisch-grid ionization chamber. The second method uses the VERDI double-energy, double-velocity (2E-2v) spectrometer of the JRC GEEL. In this presentation we discuss the experiments performed using the 2E method. The proof-of-principle has been achieved on 252Cf(sf) and 235U(nth,f) respectively. Further measurements (using 2E, on 235U(n,f) at En = 5.5 MeV) are planned at the new JRC Tandem facility, MONNET. Simulations have been performed to design proper neutron shielding and they will be benchmarked against measurements with dedicated shielding configurations. Status and perspectives of the work will be discussed.

Measurements of the Prompt Fission Neutron Spectrum at LANSCE: The Chi-Nu Experiment

LA-UR-17-XXXXX

K.J. Kelly1, M. Devlin1, J.A. Gomez1, R.C. Haight1, H.Y. Lee1, T.N. Taddeucci1, S.M. Mosby1, J.M. O'Donnell1, N. Fotiades1, D. Neudecker1, P. Talou1,

M.E. Rising1, M.C. White1, C.J. Solomon 1, C.Y. Wu2, B. Bucher2, M.Q. Buckner2, R.A. Henderson2

1) Los Alamos National Laboratory, Los Alamos, NM, 87545, U.S.A. 2) Livermore National Laboratory, Livermore, CA, 94551, U.S.A. [email protected] Abstract: The prompt fission neutron spectra (PFNS) from the neutron-induced fission of major play an important

role in criticality measurements, global security, and nuclear reactor design and also provides stringent tests of

nuclear physics models. Research on any of these topics relies on nuclear data evaluations that are, in turn,

based on experimental data. Despite the importance of the PFNS from major actinides, there are not many

measurements over the entire incident neutron energy range of interest. Furthermore, many of the measurements

that do exist do not agree with each other within the quoted 1-sigma uncertainties, thereby complicating nuclear

data evaluations. High-precision measurements of the PFNS are needed to improve and validate nuclear data

evaluations and to progress the above-mentioned fields.

The Chi-Nu experiment at the Los Alamos Neutron Science Center (LANSCE) has recently taken high-

statistics data on the PFNS from 235

U and 239

Pu. Results will be presented for the 235

U PFNS as well as

preliminary results for the 239

Pu PFNS. Time permitting, details of data analysis including a discussion of

analysis methods and uncertainty quantification will be provided.

Impact of nuclear inertia momenta on fission observables

P. Tamagno1, O. Litaize1

1) CEA, DEN, DER, SPRC, Cadarache, 13108 Saint-Paul-lez-Durance, France

[email protected]

Abstract: Fission is probably the nuclear process the less accurately described with current models, as it involves dynamics of nuclear matter with strongly coupled many-body interactions. It is thus difficult to find models that are strongly rooted in good physics; accurate enough to reproduce target observables and that can describe many of the nuclear fission observables in a consistent way. One of the most comprehensive current modeling of the fission process relies on the fission sampling and Monte-Carlo de-excitation of the fission fragments. This model exists for instance implemented in the FIFRELIN code. In this model fission fragments and their state are first sampled from pre-neutron fission yields, angular momentum distribution and excitation energy repartition law then the decay of both initial fragments is simulated. This modeling provides many observables: prompt neutron and gamma fission spectra, multiplicities also fine decomposition: number of neutrons emitted as a function of the fragment mass, spectra per fragments etc. This model relies on nuclear structure database several basic nuclear models describing for instance gamma strength functions or level densities. Additionally some free parameters are still to be determined, namely two parameters describing the excitation energy repartition law, the spin cutoff of the heavy and light fragments and a rescaling parameter for the rotational inertia momentum of the fragments with respect of the rigid-body model. In the present work we investigate the impact of this latter parameter. For this we mainly substitute the corrected rigid-body model by a quantity obtained from a microscopic description of the fission fragment. The independent-particle model recently implemented in the CONRAD code has been used to provide nucleonic wave functions that can be used to compute inertia momenta with an Inglis-Belyaev model. The impact of this substitution is analyzed on the various fission observables provided by the FIFRELIN code.

Impact of FIFRELIN input parameters on fission observables

A. Chebboubi1, O. Litaize1, O. Serot1 1) CEA, DEN, DER, SPRC, F-13108 Saint-Paul-Lez-Durance, France [email protected] Abstract: Fission yields are essential for nuclear reactor studies and are also the main observable to describe the fission process. In order to significantly improve the precision of nuclear data, more and more fundamental fission models are used in the evaluation processing. Therefore, tests of fission models become a central issue. In this framework, FIFRELIN (FIssion Fragments Evaporation Leading to an Investigation of Nuclear data) which is a Monte Carlo code, was developed in order to modelize fission fragments de-excitation through the emission of gamma rays and neutrons. To be performed a FIFRELIN calculation relies on several models such as gamma strength function and nuclear level density and of more empirical hypothesis such as total excitation energy repartition or angular momentum given by the fission reaction. Moreover, pre-emission mass yield and kinetic energy distribution per mass are necessary to process the simulation. Finally, FIFRELIN has five free parameters. A set of these parameters are chosen in order to reproduce a target observable. Often this observable corresponds to the mean neutron multiplicity for heavy and light fragment. In this work, the impact of the set of parameters over different output observables (neutron emission probability, neutron multiplicity as function of the fission fragment mass) is investigated. In the same way, the influence of input data over output observables is performed. Then, sensibility studies should give us insight about the more important parameters and drive the future work on FIFRELIN validation.

Independent fission product yields from 235U(nth,f) measured with SPIDER

F. Tovesson1, D. Mayorov1, K. Meierbachtol1, D. Shields1,2

1) Los Alamos National Laboratory, Los Alamos, NM, USA 2) Colorado School of Mines, Golden, CO, USA

Corresponding author: [email protected] Abstract: Fission product yields in thermal neutron-induced fission of 235U has been studied with the SPIDER instrument at the Los Alamos Neutron Science Center (LANSCE). The SPIDER instrument is a 2v-2E spectrometer for fission studies, and employs micro-channel plate detectors and ionization chambers for high resolution velocity and kinetic energy measurements of fission products. We will present mass yields from 235U, as well as correlations between total kinetic energy and fragment mass. Future plans for the project and the current status of the MegaSPIDER instrument construction will be presented as well.

Measuring correlated fission observables in Cf-252 with theVERDI spectrometer

K. Jansson1, A. Al-Adili1, M. O. Frégeau2, A. Göök3, C. Gustavsson1, F.-J. Hambsch3,S. Oberstedt3, S. Pomp1

1) Uppsala University, Uppsala, Sweden2) GANIL CEA/DRF-CNRS/IN2P, Caen, France3) JRC-Geel, Geel, Belgium

Corresponding author: [email protected]

Abstract: VERDI (VElocity foR Direct particle Identification) is a double energy - double velocity (2E-2v) spectrometer under development at JRC-Geel. Both the physical setup and the analysis have been improved upon since it first became operational in 2015. Currently, the spectrometer is being steadily improved using a Cf-252(sf) source.

Measuring the velocities allows computation of the pre-neutron masses and together with the kinetic energy measurements, also the post-neutron masses can be obtained. Knowing both pre- and post-neutron masses allow calculating the average neutron multiplicity as a function of fragment mass. Contrary to the 2E method, the 2E-2v method does not need prior information regarding prompt neutron emission. Therefore, VERDI presents an independent means to assess neutron multiplicity data correlated with other fission observables, helping to understand how the excitation energy is shared between nascent fragments as well as benchmarking nuclear de-excitation models.

To date our results indicate a superior pre-neutron mass resolution compared to 2E data obtained, e.g., using ionisation chambers. By implementing a new energy calibration method, based on the commonly used parametrisation proposed by Schmitt et al., we have improved the overall agreement with previous Cf-252 data. In consequence new and lower values for the set of Schmitt parameters were obtained.

As the overall agreement is convincingly good, still VERDI show some discrepancies,e.g., the pre-neutron mass yields are higher for several high yield nuclei. The pronounced structures are possibly due to the higher pre-neutron mass resolution reached with VERDI. However, at present stage the post-mass resolution remains a critical feature to improve upon, which will be one focus in our future work.

We will present the successful proof-of-principle that does not only show the feasibility of the VERDI setup but also the benefits to obtain correlated fission-yield data independent from previous measurements.

Recent developments of the FALSTAFF experimental setup

A. Chieteraa, L. Thullieza, E. Berthoumieuxa, D. Dorea, A. Letourneaua,P. Legoua, M. Kebbiria, Y. Pireta, J.P. Molsa, M. Combeta, M. Riallota,

A. Marcela, J. Pancinb, M.O. Fregeaub, X. Ledouxb, F.R. Lecolleyc,J. Perronnelc and D. Goupillerec

a Irfu, CEA, Universite Paris-Saclay, F-91191 Gif-sur-Yvette, Franceb GANIL, F-14050 Caen, Francec LPC, F-14076 Caen, France

The study of nuclear fission is encountering renewed interest with the developmentof GEN-IV reactor concepts, mostly working in the neutron fast energy domain. Tosupport the fast reactor technologies, new high quality nuclear data are needed. For thisreason, the future Neutrons For Sciences (NFS) installation, built in the framework ofthe SPIRAL2 project and producing high intensity neutron beams from hundreds of keVup to 40 MeV, will open new opportunities to characterise the actinide fission fragments.To perform these measurements, the development of an experimental setup called FAL-STAFF has been undertaken. This novel apparatus is meant to provide a simultaneouscharacterisation of the complementary fragments in terms of mass, kinetic energy and toevaluate the average neutron multiplicity.To reach this goal the spectrometer must present a very good time, energy and spaceresolutions. The coupling of the Secondary Electron Detectors (SeD) detectors with anionisation axial chamber seems fulfill these conditions.The fission fragment velocities are measured employing two time-of-flight (SeD), sepa-rated by a distance of 50 cm. Those detectors combine a Mylar foil and a MWPC (multiwire proportional counter) to measure the arrival time and the position of the incomingparticle. The fragment energies are measured by an axial ionisation chamber, CALIBER,placed after the SeD Stop detector. Moreover, the axial configuration of the chambergives access to the energy loss profile, which could be used to identify the light fragmentnuclear charge.The FALSTAFF setup and the upgrade of the first arm prototype with the new ionisa-tion chamber CALIBER will be presented. New tests are performed at CEA-Saclay andthe combined measurement obtained from the SeD and the ionisation chamber will beshown. The performances of the experimental apparatus in terms of energy and massresolution will be discussed.

(1)

Total Kinetic Energy and Fragment Mass Distributions fromFission of Th-232 and U-233

D. Higgins1,2, F. Tovesson1, U. Greife2 , S. Mosby1

1) Los Alamos National Laboratory, Los Alamos, New Mexico, USA2) Colorado School of Mines, Golden, Colorado, USA

[email protected]

Abstract: Properties of fission in Th-232 and U-233 were studied at the Los Alamos Neutron Science Center (LANSCE) at incident neutron energies from sub-thermal to 40 MeV. Fission fragments are observed in coincidence using a twin ionization chamber with Frisch grids. The average total kinetic energy released from fission andfragment mass distributions are calculated from observations of energy deposited and conservation of mass and momentum. Accurate experimental measurements of these parameters are necessary to better understand the fission process in isotopes relevant to the thorium fuel cycle, in which Th-232 is used as a fertile material to generate the fissile isotope of U-233. This process mirrors the uranium breeder process used to produce Pu-239 with several potential advantages including the comparative greater abundance of thorium, inherent nuclear weapons proliferation resistance, and reduced actinide production. For these reasons, there is increased interest in the thorium fuel cycle to meet future energy demands and improve safety and security while increasing profitability for the nuclear power industry. This research is ongoing and preliminary results are presented.

Isotopic distribution and dependency to fission product kinetic energy for

241Pu thermal neutron-induced fission

S. Julien-Laferrière1, A. Chebboubi1, G. Kessedjian2, O. Serot1, D. Bernard1, A. Blanc3, U. Koester3, O. Litaize1, T. Materna4, O. Meplan2, M. Rapala4, C. Sage2

1) CEA, DEN, DER, SPRC, F-13108 Saint-Paul-Lez-Durance, France 2) LPSC, F-38026 Grenoble, France 3) ILL, F-38042 Grenoble, France 4) CEA, DSM, IRFU, SPhN, F-91191 Gif-sur-Yvette, France [email protected] Abstract:

Nuclear fission yields are key parameters to evaluate reactor physics quantities, such as decay heat, criticality or spent fuel radiotoxicity, and for understanding fission process. Despite a significant effort allocated to measure fission yields during the last decades, the recent evaluated libraries (JEFF-3.1.1, ENDF/B-VII.1, JENDL-4.0 …) still need improvements in particular in the reduction of the uncertainties. Additionally, some discrepancies between these libraries must be explained. A common effort by the CEA, the LPSC and the ILL aim at tackling these issues by providing precise evaluation of isotopic and isobaric fission yields with the related variance-covariance matrices. Measurements for thermal neutron induced fission of 241Pu have been carried out at the ILL in Grenoble, using the LOHENGRIN mass spectrometer. This instrument allows a selection regarding the A/q and Ek/q ratios, supplying a beam of fission products of mass A, kinetic energy Ek and of ionic charge q. Coupled to Ge detectors, one can identify the fission product nuclear charge, Z, and measure its count rate to eventually determine the isotopic yield Y(A,Z) for the main isotopes of mass A for a specific Ek.

By this method, several masses have been measured in order to investigate local odd-even effects. In particular, by looking at the fission yields evolution according to the fission product kinetic energy, the sharing of the total available excitation energy at scission between deformation energy and intrinsic energy is aimed to be better understood. The main isotopic yields for the masses 130, 132, 136, 137, 138, 139, 140 and 141 will be presented. In addition, preliminary results for the masses 92, 138 and 139 showing a clear evolution of isotopic yields over Ek will be discussed.

Application of Calorimetric Low-Temperature Detectors for the Investigation of Z-yield Distributions of Fission Frag-

ments S. Dubey1,2, A. Echler1,2, S.Bishop5, A.Blanc4, P.Egelhof1,2, F.Goennenwein6,

J.Gomez5, P.Grabitz1,2, U.Koester4, S.Kraft-Bermuth3, W.Lauterfeld2, M.Mutterer1, P.Scholz3, S.Stolte2

1) GSI, Darmstadt, Germany 2) Johannes Gutenberg University, Mainz, Germany 3) Justus Liebig University, Giessen, Germany 4) ILL, Grenoble, France 5) Technical University, München, Germany 6) Eberhard Karls University, Tübingen, Germany [email protected]

Abstract: Precise data on fission fragment yields play an important role in our under-

standing of the fission process and in applied fields, e.g. for calculating accumulation and inventory of fission products at various stages of the nuclear fuel cycle in a reac-tor. Up to now, the high-resolution fragment mass spectrometer Lohengrin, installed at the ILL Grenoble, has contributed more complete data sets on mass, nuclear-charge and energy distributions than any other method. With the aim of further de-veloping nuclear-charge yield measurements at Lohengrin, we recently have applied the technique of Calorimetric Low-Temperature Detectors (CLTDs) for measuring residual energies of the fragments after spectrometer separation and passage through a stack of SiN membranes as a novel type of degrader material. The concept of CLTDs which is based on sensing the temperature rise in the low-temperature de-tector medium by the energy of the absorbed particle provides fundamental ad-vantage over conventional ionization-mediated detectors, in particular for heavier particle masses at low energies. In the experiment, a cryostat containing an array of 25 detector modules (total active area of 15x15mm2) was coupled to the Lohengrin. Variation of absorber thickness was achieved by a remotely controlled sample changer operated inside the cryostat, close to the CLTD array.

Using fissile targets of 235U, 239Pu and 241Pu, the quality of nuclear-charge separation was studied for selected masses in the region 82 ≤ A ≤ 139 as a function of degrader thickness and fission-fragment kinetic energies. For the light fragment group, the Z resolution attained matches historically best values achieved with Parylene-C absorbers and ionization chambers. We have gained first Lohengrin data on the isotopic yields in the light-mass group of 241Pu fission. Towards mass sym-metry, known Z-yield data were supplemented in the range A = 110 to 112 for 241Pu, and A = 111 to 113 for 239Pu. Extended data sets were cumulated for the masses A = 92 and 96 in 235U (and 241Pu) because of a recent request from studies on the reactor anti-neutrino spectrum. Furthermore, an attempt was made to extend isotopic yield measurements up to the heavy-mass region, hardly accessible until now. Preliminary data will be presented for the various parts of the investigation.

Can low-energy fission produce three heavy fragments?

P. Holmvall1,2, U. Köster2, A. Heinz1, T. Nilsson1

1) Chalmers University of Technology, Gothenburg, Sweden2) Institut Laue-Langevin, Grenoble, France

[email protected]

Abstract: Over seven decades of nuclear fission research have consistently shown that low-energy fission of the lighter actinides usually results in two fragments with dissimilar masses. In comparison, fission into fragments with similar masses or three fragments (ternary fission) is a very rare process, although such mass splits would often exhibit higher Q values andlower minima in the potential energy surfaces. For ternary fission the yields drop rapidly with increasing mass and nuclear charge of the third fragment. Although energetically more favourable, such events are strongly suppressed due to high fission barriers.

Early claims of fission into three fragments of comparable masses (true ternary fission) were later disputed with different experimental techniques.In recent years true ternary fission has found a renewed interest due to claims of a new mode of nuclear fission, dubbed collinear cluster tri-partition (CCT), based on indirect experimental observation by the FOBOS collaboration. The suggestion is that three heavy fission fragments are emitted with perfect alignment along the same fission axis with a fission yield of about 0.5% in several fissioning systems. According to the FOBOS collaboration this high yield is due to high Q values and low potential energy surface minima, and furthermore that a special asymmetric double-arm spectrometer is required to observe CCT.

We use simple arguments based on energy and momentum conservation to highlight problems with these arguments. If CCT in fact exists it would be observable with any single- or double arm spectrometer. Furthermore, we show that the proposed CCT is either not consistent with the uncertainty principle, or would have given rise to additional strong signatures contradicting with data from previous experiments. In light of this, and given the surprising high yields, it is important that the nuclear physics and radiochemistry community analyse this extraordinary new mode of nuclear fission, and verify or refute it experimentally. We discuss and suggest various ways of achieving this, and present the upper and lower limits of the possible kinetic energies that such fragments are allowed to have according to energy and momentum conservation. These energies can be measured with many existing fission-fragment spectrometers.

Wednesday, March 22, 2017

Fission study using multi-nucleon transfer reaction at JAEA tandem

K. Nishio1, K. Hirose1, M. Vermeulen1, H. Makii1, R. Orlandi1, K. Tsukada1, M. Asai1,

A. Toyoshima1, T.K. Sato1, S. Chiba2, Y. Aritomo3, S. Tanaka3, T. Ohtsuki4, I. Tsekhanovich5, C.M. Petrache6, A.N. Andreyev7,1

1) Advanced Science Research Centre, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan 2) Laboratory of Advanced Nuclear Energy, Tokyo Institute of Technology, Tokyo 152-8550, Japan 3) Faculty of Science and Engineering, Kindai University, Higashi-Osaka 577-8502, Japan 4) Research Reactor Institute, Kyoto University, Kumatori-cho, Osaka 590-0494, Japan 5) University of Bordeaux, 351 Cours de la Libration, 33405 Talence Cedex, France 6) Center de Sciences Nucléaire et des Science de la Matière, Université Paris-Saclay, CNRS/IN2P3, 91406, Orsay, France 7) Department of Physics, University of York, Heslington, Yorkm YO10 5DD, York, Unide Kingdom [email protected] Abstract:

This talk will discuss the use of multi-nucleon transfer (MNT) reactions to study fission properties of multitude exotic nuclei in the neutron-rich actinide region. Most of these nuclei cannot be accessed by the traditional method of complete-fusion reactions. The MNT transfer channels of the 18O+232Th reaction were used to study fission of fourteen nuclei 231,232,233,234Th, 232,233,234,235,236Pa, and 234,235,236,237,238U [1]. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions (FFMDs) are measured for each transfer channel. In particular, the FFMDs of 234Th and 234,235,236Pa were measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. By using the same method, the measurements with 238U, 237Np, 248Cm, and 249Cf targets were recently performed.

The obtained FFMDs are compared with a calculation based on the fluctuation-dissipation model [2], where effect of multi-chance fission (neutron evaporation prior to fission) was considered. It was found that multi-chance fission has significant role on the shape of FFMD, particularly at the high-excitation energies. We also discuss the fission fragment angular distributions relative to the recoil direction as an indication of spins brought to the system in the MNT reaction. Furthermore a campaign to measure prompt neutrons correlated with fission fragments has started. Reference [1] R. Leguillon et al., Phys. Lett. B 761, 125 (2016). [2] Y. Aritomo and S. Chiba, Phys. Rev. C 88, 044614 (2013).

First simultaneous measurement of fission and gamma probabilities of

237U,

238Np and

239Np via surrogate reactions

P. Marini1,2,Q. Ducasse2,3,B. Jurado1, M. Aiche1, L. Mathieu1, G. Barreau1, S. Czajkowski1, I. Tsekhanovich1, O. Bouland3, F. Giacoppo5, A. Gorgen5, Tornyi5, L.

Audouin6, L. Tassan-Got6, J. N. Wilson6, F. Gunsing7, M. Guttormsen5, A. C. Larsen5, M. Lebois6, T. Renstrom5, S. Rose5, S. Siem5, G. M. Tveten5, M.

Wiedeking8, O. Serot3, G. Boutoux2, V. Meot2, B. Morillon2, D. Denis-Petit2, O. Roig2, S. Oberstedt9, A. Oberstedt9

1) CENBG, Chemin du Solarium B.P. 120, 33175 Gradignan, France 2) CEA, DAM, DIF, F-91297 Arpajon, France 3) CEA-Cadarache, DEN/DER/SPRC/LEPh, 13108 Saint Paul lez Durance, France 5) University of Oslo, Department of Physics, P.O. Box 1048, Blindern 0316 Oslo, Norway 6) IPN Orsay, 15 rue G. Clemenceau, 91406 Orsay cedex, France 7) CEA Saclay, DSM/Irfu, 91191 Gif-sur-Yvette cedex, France 8) iThemba LABS, P.O. Box 722, 7129 Somerset West, South Africa 9) EC-JRC, Geel, Belgium [email protected] Abstract: The surrogate-reaction method is an indirect method for determining neutron-induced cross sections of short lived nuclei, which are key quantities both in astrophysics and nuclear data applications. Fission and gamma decay probabilities of 237U, 238Np and 239Np have been measured, for the first time simultaneously in dedicated experiments, via the surrogate reactions 238U(3He,4He), 238U(3He,t) and 238U(3He,d), respectively. While a good agreement between our data and neutron-induced data is found for fission probabilities, gamma decay probabilities are several times higher than the corresponding neutron-induced data for the studied 237U and 238Np nuclei. We study the role of the different spin distributions populated in the surrogate and neutron-induced reactions. Our results indicate a strong sensitivity of the gamma probability to the compound nucleus angular momentum distribution and, contrary to statistical model predictions, a much weaker sensitivity of the fission probability. Preliminary results from a Hauser-Feshbach calculation, coupled with a DWBA-deduced spin and parity distribution for the 238U(3He,4He) reaction, well reproduce, for the very first time, both measured fission and decay probabilities, helping to gain an insight into the origin of the weaker sensibility of the fission probability to the angular momentum. This finding is highly relevant because it implies that the Hauser-Feshbach calculation, tuned on decay probabilities measured in surrogate reactions, can provide reliable predictions for neutron-induced cross sections of short-lived nuclei that cannot be directly measured.

In the contribution we will present the mentioned results and possible future developments.

Use of active scintillating targets in nuclear physics experiments - measurement of spontaneous fission

Gilbert Bélier1) , Jean Aupiais1), G. Sibbens2), A. Moens2), D. Vanleueuw2) 1) CEA, DAM, DIF, DPTA Centre du Grand rue, 91297 Arpajon, France 2) Europan Commission, Joint Research Centre, IRMM, Retieseweg 111, 2440 Geel, Belgium [email protected] Abstract: The Liquid Scintillation Spectrometry technique has advantages that can be used in nuclear physics experiments. Compared to ionization chambers for example, liquid scintillation provides very high detection efficiencies. In the context of studies on the nuclei fission process this is a definitive advantage where count losses have to be known very precisely. We will present the general features of a scintillating target used in nuclear physics experiments, and the special developments that were performed. Particularly the response of a few homemade and commercial scintillators to fission events will be presented. We will detail simulations that were performed, in order to precisely determine the detection

efficiency to fission events and also to decays . Finally we will present preliminary results obtained in the measurement of the spontaneous fission (SF) of 240Pu and 242Pu. It will be shown that a precise count of SF and alpha decay events can be made, together with a precise count of pile-up events. It will be shown that very

precise ratio of the SF over -decay half-lives can be made, and that the main limitation is due to the sample impurities knowledge.

mailto:[email protected]

First Results on 238

U(n,f) Prompt Fission Neutron Spectra from 1 to 800 MeV incident neutron energy

P. Marini1, B. Laurent1, G. Belier1, T. Bonnet1, A. Chatillon1, J. Taieb1, D. Etasse2, M.

Devlin3, R. Haight3 1) CEA, DAM, DIF, F-91297 Arpajon, France 2) LPC Caen, ENSICAEN, Universite' de Caen, CNRS/IN2P3, Caen, France 3) P-27, Los Alamos National Laboratory, Los Alamos, NM-87544, USA [email protected] Abstract: A new 238U(n,f) prompt fission neutron spectra (PFNS) measurement has been recently performed at the WNR facility of the Los Alamos National Laboratory. The measurement allows one to explore the dependence of the prompt fission neutron energy spectra on the incident neutron energy, which covers the range from 1 to 800MeV. The experimental setup couples the 54 ChiNu scintillator cells array to a newly developed fission chamber, characterized by an improved alpha-fission discrimination and time resolution, a reduced amount of matter in the neutron beam and a higher actinide mass. The dedicated setup and the high statistics collected allows us to obtain a good precision on the measured fission neutron energy, as well as to explore the low energy region, down to 500keV, and the high energy region, above 5 MeV, of the emitted neutron spectrum. These are indeed the regions where discrepancies in the evaluated PFNS data are found. In this contribution we will present the first results of the experiment, with a particular focus on the dependence of the mean kinetic energy of the emitted neutrons as a function of the incident neutron energy.

Tests of ionisation chambers for photofission experiments

M. Peck1, J. Enders1, M. Freudenberger1, A. Göök2, A. Oberstedt3, S. Oberstedt2, 1) Institute for nuclear physics, TU Darmstadt, Germany 2) European Commission, JRC-IRMM, Geel, Belgium 3) ELI-NP, Măgurele, Romania [email protected] Abstract: Photofission in the barrier region suffers from relatively low cross sections.

Hence, besides using intense bremsstrahlung (S-DALINAC) or

monochromatic gamma ray beams (ELI-NP), significant amounts of target

material needs to be placed in the beam to reach sufficient luminosity.

We set up and tested a multi-stack Frisch-grid ionisation chamber and

obtained angular and mass distributions as well as total kinetic energy

of fission fragments in neutron-induced fission of 232

Th and 238

U.

For the measurement of the azimuthal angular distribution segmented

anodes have been used.

Characterization of a Coaxial Ionization Chamber with aTime-of-Flight Section for Fission Fragment

Spectroscopy at Lohengrin, ILL

N.V. Sosnin1, A.G. Smith1, T. Wright1, P.J. Davies1, U. Koester2, A. Blanc2

1) The University of Manchester, Manchester, UK2) Institut Laue-Langevin, Grenoble, France

[email protected]

Abstract: A coaxial ionization chamber was built at the University of Manchester forfission fragment spectroscopy and was subsequently tested on the Lohengrin massspectrometer at the Institut Laue-Langevin (ILL) in 2011. The ionization chamberfeatured a timing detector to signal the entry of a fragment into the chamber. In therecent experiment (2016), another timing detector has been added to thespectrometer to form one meter long time-of-flight section. The resulting one-energyone-velocity fission fragment spectrometer was taken to ILL for characterization. Thiswas performed using 235U fission fragments produced in the ILL high-flux reactor andseparated into known mass, energy and charge states in Lohengrin. Resultant dataare currently undergoing analysis at the University of Manchester.

The goal of the analysis is to apply digital sub-Bragg peak spectroscopic techniquesto the data to extract fragment energies, charge states and masses. Theseparameters will then provide insights into the characteristics of the ionizationchamber and the time-of-flight section. Additionally, during the data analysisextraction of any information on charge exchange processes inside Lohengrin will beattempted. Furthermore, the results can be applied to SpecTrometer for ExoticFission Fragments (STEFF) data. STEFF is a two-energy two-velocity fissionfragment spectrometer built at the University of Manchester. It features four arms,two of which are similarly designed to the ionization chamber used at Lohengrin.STEFF was used to perform measurements of the fission process in 235U at anexperiment in June 2016 at the n_ToF facility at CERN. Analysis of the data collectedat that experiment will make use of the ionization chamber characteristics.

Refractory Beams at ISOLDE – A concept for a fission recoil target

J. Ballof1,2, C. Seiffert1, Ch. E. Düllmann2,3,4, T. Stora1, A. Yakushev3,4 1) CERN, ISOLDE, Geneva, Switzerland 2) Johannes Gutenberg-Universität Mainz, 55122 Mainz, Germany 3) GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany 4) Helmholtz-Institut Mainz, Mainz, Germany [email protected] Despite the manifold new developments introduced to ISOL target units within the last 60 years, the beam extraction of elements with very high boiling points (refractory elements) remains still among the most challenging topics. Due to their vanishingly low volatility, the radionuclides generated by the driver beam are captured within the target and suffer from hampered release [1]. Recently however exotic boron beams could be newly produced as BFx

+ molecular ions [2]. We propose here an advanced target design for ISOL facilities, in which diffusion through condensed matter can be fully avoided. Instead of diffusion, we make use of the recoil momentum, which allows fission fragments to propagate through and emerge from thin uranium foils. The recoils are thermalized in a reactive gas and form volatile compounds in-situ. Subsequently, the reactive gas is removed by cryogenic gas separation [2], as shown in Fig. 3. The system is evacuated while the carbonyl compounds are retained on a cooling trap. After removal of the excess gas, the volatile compounds are fed into the ion source by warming up the cooling trap. A compound class that appears well suited for in-situ volatilization is that of metal carbonyl complexes.

Figure1‐PeriodicSystemofelementsshowingavailablebeamsatISOLDE(green),Non‐availableElements,whichformtransitionmetalcarbonyls(redbackground)andcarbonylchalcogenides(redframe).

Already in 1970, the extraction using carbonyl complexes was proposed [3] and recently, it was shown that volatile carbonyl complexes form readily at ambient temperature and pressure by thermalizing fission fragments of suitable elements in a carbon monoxide-containing atmosphere [4]. The ISOLDE Periodic System of Elements shown in Figure 1 demonstrates the potential of the “carbonyl method”. Nine out of fifteen transition metals, which are not yet available, form volatile carbonyl compounds.

Figure2‐Designofthemodeltarget

While carbonyl compounds open up new perspectives in the development of refractory beams, they are delicate compounds. Decomposition on hot surfaces, by electron beams, plasmas and UV-light is expected, which needs to be considered not only in the target design, but also in the choice of the ion source.

Figure3‐Gasseparationconcept

Within this work, simulations have been conducted aiming at the estimation of attainable yields. Several different ion sources were tested, including a FEBIAD-type VADIS source and cold plasma RF ion sources. Finally, the laser-induced break-up of carbonyl complexes as essential preparatory step to resonant laser ionization was also experimentally addressed. As next steps we plan to conduct on-line experiments to investigate the carbonyl-based beam production at ISOLDE as well as further ionization tests with a mono charge ECR ion source.

References [1] U. Köster et al., (Im-)possible ISOL beams, Eur. Phys. J. Special Topics 150,

285-291 (2007). [2] C. Seiffert, Production of radioactive molecular beams for CERN-ISOLDE,

Doctoral dissertation, Technische Universität Darmstadt (2014) [3] K. Katagiri et al., Rev. Sci. Instr. 86, 123303 (2015). [4] K. Baechmann, Chemical Problems of the On-Line Separation of short-lived

Nuclides, Proceedings of the international conference on electromagnetic isotope separators and the techniques of their applications, BMBW-FBK--70-28 (1970).

[5] J. Even et al., In-situ formation, thermal decomposition, and adsorption studies of

transition metal carbonyl complexes with short-lived radioisotopes, Radiochimica Acta 102, 1093-1110 (2014).

Summation calculations of delayed neutron yields for 235

U, 238

U and 239

Pu, based on various fission yield and neutron emission probability databases

D. Foligno1, P. Leconte1, O. Serot1, O. Litaize1, A. Chebboubi1 1) CEA Cadarache, St. Paul-lez-Durance, France [email protected] Abstract: Nuclear data libraries have different origins and do not always agree with one another. This work is focused on the calculation of the delayed neutron yield (𝜈𝑑) by summation method. The quantities of interest are therefore the fission yields (FY) and the delayed neutron emission probabilities (Pn). The objective was to evaluate the reliability of nuclear data libraries on the mentioned quantities:

FY evaluations (JEFF-3.1.1, ENDF/B-VII.0) and calculations (FIFRELIN, GEF)

Pn (JEFF-3.1.1, ENDF/B-VII.0, JENDL-FPDD2000, NNDC, Audi, Pfeiffer and Krats, RIPL-3, RIPL-3-2015)

Summation calculation has been performed for the thermal fission of 235U and 239Pu as well as for the fast fission of 235U, 238U and 239Pu. The results have been compared with the recommended values found in the literature. Furthermore, the 20 major delayed neutron precursors have been identified, their FY and Pn compared and their importance assessed. The conclusions of the work are:

RIPL-3-2015 is more complete than RIPL-3, the last one having the Pn of some important precursors set to zero

Cumulative Yields (CY) give higher 𝜈𝑑 than the respective Independent Yields (IY)

ENDF/B-VII.0 library contains an unphysical CY for 86As (in case of thermal fission of 235U)

FIFRELIN’s IYs are overestimated

JEFF-3.1.1’s Pn-library always underestimates the 𝜈𝑑 due to an excessively small Pn for 85As

ENDF/B-VII.0 CY-library gives larger 𝜈𝑑 values than JEFF-3.1.1 in case of thermal fission (especially of 235U, due to the larger CY of 86As and 96Rb). On the other hand, it gives smaller values than JEFF-3.1.1 in the case of fast fission (235U, 238U, 239Pu)

While the 𝜈𝑑 should not vary with energy, in the calculations it decreases using ENDF/B-VII.0’s CY, and increases if using JEFF-3.1.1’s

The precursors’ importance highly depends on the fissioning system

Fast-timing measurements in neutron-rich odd-mass zirconium isotopes using LaBr3:Ce detectors coupled with

Gammasphere. E. R. Gamba1, S. Lalkovski2, M. Rudigier2, A. M. Bruce1, S. Bottoni3, M. P. Carpenter3, S. Zhu3,

A. D. Ayangeakaa3, J. T. Anderson3, P. Copp4, J. P. Greene3, D. J. Hartley5,

R. V. F. Janssens3, F. G. Kondev6, G. J. Lane7, T. Lauritsen3, M. Reed7, J. Rohrer3, J. Sethi3, D. Seweryniak3 and the NUSTAR-FATIMA collaboration. 1) School of Computing, Engineering and Mathematics, University of Brighton, UK 2) Department of Physics, University of Surrey, Guildford, UK 3) Physics Division, Argonne National Laboratory, Illinois 60439, USA 4) Department of Physics and Applied Physics, University of Massachusetts Lowell, USA. 5) Department of Physics, U.S. Naval Academy, Annapolis, Maryland 21402, USA 6) Nuclear Engineering Division, Argonne National Laboratory, Illinois 60439, USA 7) Department of Nuclear Physics, R.S.P.E., Australian National University, Australia [email protected] Abstract: A fast-timing experiment was performed at the Argonne National Laboratory between December 2015 and January 2016, with the purpose of measuring the lifetimes of the lowest lying states of nuclei belonging to the deformed regions around mass number A≈110 and A≈150. The lifetimes of the first excited states are the basic ingredients for quadrupole moment calculations, which give information about the structural evolution that occurs in the deformed areas of the nuclear chart. The nuclei of interest were populated in the spontaneous fission of 252Cf since the maxima of the fragment mass distribution lie approximately in the centre of the regions of interest. The 252Cf source was placed at the focus of the Gammasphere array (51 HPGe) which was coupled with a fast timing array, comprising 25 LaBr3:Ce scintillator detectors. Each sub-array covered ≈2π of the solid angle. Quadruple events (two gamma rays from Gammasphere and two from the LaBr3:Ce array) were collected for a period of 30 days. LaBr3:Ce scintillator detectors have been extensively used in the past to perform fast-timing measurements thanks to their capability to access the sub-nanosecond regime. The high energy resolution of HPGe detectors together with the excellent time resolution of LaBr3:Ce detectors, conferred to this hybrid array the right features to perform both fast-timing and spectroscopy measurements. This was the first time that the Gammasphere array was successfully coupled with an array containing such a large number of LaBr3:Ce detectors. Details of the setup and the digital acquisition system will be given, focusing on the signal processing and the coincidence mechanism. Some preliminary results obtained from 152Eu and 166Ho sources will be shown in order to prove the effectiveness of this arrangement. The status of the analysis for the nuclei 103,105Zr, lying in the first peak of the 252Cf fragment mass distribution, will be presented. Work at ANL is funded by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under Contract Number DE-AC02-06CH11357. This research used resources of Argonne National Laboratory's ATLAS facility, which is a DOE Office of Science User Facility.


Discovery of Elements 113 - 118 R. N. Sagaidak1, V. K. Utyonkov1, Yu. Ts. Oganessian1, S. N. Dmitriev1, M. G. Itkis1,

K. J. Moody2, M. A. Stoyer2, D. A. Shaughnessy2, J. B. Roberto3, K. P. Rykaczewski4, J. H. Hamilton5 for the collaboration1,2,3,4,5,6,7

1Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, RU-141980 Dubna, Russian Federation

2Nuclear and Chemical Sciences Division, Lawrence Livermore National Laboratory, Livermore, California 94551, USA

3Science and Technology Partnerships Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

4Physics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

5Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235, USA

6Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA

7Research Institute of Atomic Reactors, RU-433510 Dimitrovgrad, Russian Federation

Email.of.corresponding.author: [email protected] Abstract: Discovery and investigation of the “Island of stability” of superheavy nuclei (SHN) at the separator DGFRS in the 238U-249Cf+48Ca reactions is reviewed. The results are compared with the data obtained at the separators SHIP, BGS, TASCA and GARIS, and in chemistry experiments. The data on reactions of synthesis of SHN, their alpha decay and spontaneous fission properties, as well as methods of their identification are discussed. The increased role of shell effects in the stability of SHN with a rise of their neutron number and approaching the magic number of N=184 is demonstrated by comparison of the experimental results with empirical systematics and theoretical data.

PHYSICS AVENUE WITH THE SUPER SEPARATOR SPECTROMETER (S3) AT

THE SPIRAL2 FACILITY

H. Savajols

1, A. Drouart

2, J.A. Nolen

3, spokespersons for the S

3 collaboration

1 GANIL, Caen, France

2 CEA Saclay, DSM/Irfu/SPhN, Gif/Yvette, France

3 Argonne National Laboratory, Argonne, IL, USA

email : [email protected] The LINAG accelerator of the SPIRAL2 project in GANIL will produce not only proton and

deuteron beams, but also stable heavy ion beams with very high currents, with energies from

0,75 to 14MeV/u. These stable ion beams will enable us to study rare events in the fields of

nuclear physics and atomic physics:

- Synthesis and decay spectroscopy of fusion evaporation products, notably super heavy

elements and nuclei at the proton drip line,

- Multi-nucleonic transfer and deep inelastic reactions,

- Study of production mechanisms and reaction products distributions,

- Study of ground state and isomeric properties of rare nuclei,

- Electron capture/ionisation in beam-beam interactions. S3 (Super Separator Spectrometer [1], Figure 1) is a facility designed to handle these high beam currents, combining a high selectivity of the reaction products with a high transmission of the nuclei of interest. It includes:

- A rotating target, able to sustain high beam powers, - A separator with two main functions:

- Reject the beam ions to prevent them from reaching the detection place,

- Select the mass of the different reaction products,

- A detection setup at the final focal plane, adapted to the running experiment:

- The SIRIUS [2] spectroscopy station to study alpha, electron and gamma decays

of the nuclei of interest,

- The REGLIS3 [3] low energy branch that stops the products in a gas cell for in-

gas-jet laser ionisation and spectroscopy and, if required, transmission to other

detection systems.

S3 is a two-step separator, with a primary selection stage with momentum selection and a

secondary mass selection stage combining and electric and a magnetic dipole. It has wide

angular, momentum and charge state acceptances, in order to have a large transmission for

low energy reaction products. In the present paper, we will present the latest progresses in the

construction of the spectrometer and detection setups, and notably full simulations of the

transmission and the mass resolution of the device. We will describe some highlight physics

cases from the letters of intent and fission spectroscopy in the trans-actinides region.

Figure 1: Sketch of S with its gas catcher and low energy branch. The beam comes from the upper left

end.

[1] F. Déchery & al. Eur. Phys. J. A 51 (2015) 56.

[2] J. Piot and the S3

collaboration, Acta Phys. Pol. B 43 (2012) 285.

[3] R. Ferrer & al. Nucl. Inst. and Meth. B, Volume 317 (2013) 570.

Charting Terra Incognita at Alto and S3

S Franchoo

IPN, 91406 Orsay, France

[email protected]

Abstract:

Charting Terra Incognita1 brings together the IPN Orsay, CSNSM Orsay and Irfu Saclay laboratories around the common development of know-how, equipment and techniques for the low-energy branches Desir and S3 at Spiral-2 at Ganil, while initiating a corresponding physics programme at Alto.

The first half of the project is based at the Ato faciltiy, which is an infrastructure that comprises an on-line isotope-separation facility based on the photofission of uranium next to a stable ion beam facility based on a 14.5-MV tandem accelerator. The isotope-separation on-line section is dedicated to the production of neutron-rich radioactive ion beams (RIB) from the interaction of the gamma flux induced by a 50-MeV 10-µA electron beam in a uranium carbide target. It is dimensioned for 1011 fissions per second. Its laser ion source has so far delivered radioactive beams of gallium and zinc isotopes, while indium and tin have been ionised off-line. After mass separation, the RIBs are presently sent to an experimental beam line dedicated to beta decay, whereas the construction of three set-ups for low-temperature nuclear orientation, collinear laser spectroscopy and a double Penning trap for mass measurements takes place under the aegis of Charting Terra Incognita.

Next to setting the pace for an precurser physics programme at Alto for the future Desir facility at Ganil, Charting Terra Incognita includes efforts for the commissioning of the new S3 spectrometer at Ganil as well as the development of acquisition algorithms for decay studies of very heavy elements by means of the Sirius silicon detector array. Meanwhile also the Reglis set-up for intrajet laser spectroscopy is entering its final phase of construction, which equipped with a MR-Tof mass spectrometer will aim at measuring the ground-state properties and decay modes of those transactinides that will be produced at S3.

1 Selected "Projet emblématique" of Labex P2IO

Recent progress on the study of nuclear fission using laser spectroscopy

Kieran Flanagan

CERN, CH-1211 Geneve 23 Email.of.corresponding.author: [email protected] Abstract: High-resolution optical measurements of unstable atoms provides some of the most fundamental nuclear properties: spin, nuclear moments, mean-square charge radii. Furthermore the simple fact that an observation of an optical resonance has been made, confirms the existence of a new nuclide or long-lived nuclear state. By performing systematic measurements across isotope chains it is possible to elucidate structural changes and the onset of new phenomena. These measurements are compelling since they do not rely on the assumptions of any particular nuclear model and rather provide a rigorous test of existing models. This is a particularly exciting time as recent advances in nuclear theory have extended the limits of ab initio calculations to the 100Sn region representing a stepping stone to 132Sn and studying fission fragments. There has been considerable attention focused onto the heaviest nuclei in the last 10 years, with many exciting new measurements made at the very limits of stability. Providing key structural information on the starting point for the fission process. The ability for laser techniques to select isomeric states also opens up the ability to carefully study the process of spontaneous fission and beta-delayed fission at different excitation energies, spins and shapes within the same nucleus. This talk will present a summary of the latest achievements and future developments of laser spectroscopy relevant to nuclear fission.

Prompt fission gamma rays and their angular distributions

A. Oberstedt1, R. Billnert2,3, A. Gatera2, A. Göök2, S. Oberstedt2 1) Extreme Light Infrastructure – Nuclear Physics / Horia Hulubei National Institute

for Physics and Nuclear Engineering, Bucharest-Magurele, Romania 2) European Commission, DG JRC, Directorate G – Nuclear Safety and Security, G.2

SN3S, Geel, Belgium 3) Present address: Studsvik Nuclear AB, Nyköping, Sweden [email protected] Abstract: Nuclear fission is a complex process, which – after almost 80 years since its discovery – is still not fully understood. One field of research is for instance studies of the de-excitation of fission fragments, which in the early stages, i.e. within a few nanoseconds after scission, takes place through the successive emission of prompt neutrons and gamma rays. For nuclear applications, information about the prompt neutrons is crucial for calculating the reactivity in reactors, while precise knowledge about the prompt gamma rays is important for the assessment of the decay heat released in the reactor core. Concerning the latter we have contributed in the past years with a number of precise measurements of prompt gamma ray spectra characteristics from the spontaneous as well as thermal and fast neutron-induced fission of various compound systems. In this work we report on recent measurements of prompt fission gamma rays, present the results and infer what can be learned from the observed angular distribution.

Nuclear Structure of SHN – State of the Art and Perspectives at S

3

D. Ackermann1 1) Grand Accélérateur National d’Ions Lourds – GANIL, 14076 Caen, France [email protected] Abstract: The new separator-spectrometer combination S3, presently under construction at the new SPIRAL2 facility of GANIL, Caen, France, together with the high intensity beams of SPIRAL 2’s SC LINAC, will offer exciting perspectives for a wide spectrum of nuclear and atomic physics topics. Among the mayor features to be studied, apart from nuclei in the N=Z region, nuclei of astrophysical relevance and some atomic physics issues, are the properties of the heaviest nuclei (superheavy nuclei – SHN). The installation is designed to employ nuclear physics methods like decay spectroscopy after separation or atomic physics methods like laser spectroscopy and mass measurements. The nuclear physics studies will include particle and photon correlation studies, attacking the open questions in the field, which have been revealed in earlier studies at facilities like e.g. GSI with the velocity filter SHIP and the gas-filled separator TASCA, Jyväskylä with RITU and its numerous auxiliary detection set-ups, the DGFRS and VASSILISSA/SHELS separators at FLNR/JINR in Dubna etc. The research subjects include K-isomers, isotopic and isotonic trends of low lying nuclear

excitations and -electron- and -electron-fission coincidences. The detection array SUIRIUS at the focal plane of S3, presently being developed for this purpose, is also an ideal tool to study delayed processes like isomeric states and β-delayed fission. A low energy set-up including a gas stopping cell, laser spectroscopy instrumentation and a multi-reflection time-of-flight spectrometer, will be used to study nuclei in the N=Z region as well as the heaviest nuclear species. In a farer future the synthesis and investigation of, also so far unknown, highest-Z systems is envisaged, for which the earlier experiments will produce the basis. The state of the art of the SHN spectroscopy will be presented and an outline for the physics program at S3 will be given in this presentation.

The -ray spectroscopy studies of low-spin structures in 210

Bi and 206

Tl using cold neutron capture reactions N.Cieplicka-Oryńczak1, S.Leoni2, B.Fornal1, D.Bazzacco3, A.Blanc4, S.Bottoni2, A.Bracco2, F.Crespi2, G. de France5, Ł.Iskra1, M.Jentschel4, U. Köster4, C.Michelagnoli4, P. Mutti4, G.Simpson6, T.Soldner4, C.Ur7, and W.Urban8. 1) Institute of Nuclear Physics PAN, Kraków, Poland 2) INFN Sezione di Milano and Universita di Milano, Milano, Italy 3) Dipartimento di Fisica e Astronomia dell’Universit`a and INFN Sezione di Padova, Padova, Italy 4) Institut Laue-Langevin, Grenoble, France 5) GANIL, Caen, France 6) LPSC, Universite Joseph Fourier, CNRS/IN2P3, Institut National Polytechnique de Grenoble, Grenoble, France 7) ELI–NP Bucharest-Magurele, Romania 8) Faculty of Physics, University of Warsaw, Warszawa, Poland

[email protected]

Abstract: Nuclei around doubly-closed shells play a crucial role in studying both a) the couplings between valence nucleons which provide information on the effective nucleon-nucleon interaction and, b) couplings of the valence nucleons with core excitations, which may be used as a unique test of various effective interactions used in mean-field based models, like Skyrme, Gogny etc. From a broader perspective, understanding the coupling of a single particle to vibrational motion in nuclei is of primary importance, as this coupling is responsible for the quenching of spectroscopic factors [1]; it is also the key process at the origin of the damping of giant resonances [2]. The vibrational phonons are best known from the spectroscopic studies of doubly-magic nuclei in which they appear, in general, as the lowest excited states. For example, in 208Pb, the lowest excitation (at 2615 keV) is the 3– octupole vibration with a large E3 transition strength of 34 W.u.

We investigated the low-spin structures of 210Bi and 206Tl up to their neutron-

capture states at 4.6 and 6.5 MeV, respectively, by using 209Bi(n,)210Bi and 205Tl(n,)206Tl reactions induced by cold neutrons at ILL Grenoble.

The 210Bi nucleus (one proton and one neutron above the 208Pb core) was populated in the experiment performed at the PF1B and cold-neutron facility in which

- coincidences were measured with the EXILL array consisting of 16 Ge detectors.

It is the first time when such large array was employed for 209Bi(n,)210Bi reactions studies so the decay scheme could be revised and significantly extended. The

analysis of the angular correlations of rays provided information about transitions multipolarities and helped with the spin-parity assignments. The structure arising from the excitations of valence proton and neutron was compared to the shell-model calculations. Some of the observed states must come from the coupling of the valence particles excitations with the first excited state in 208Pb, that is 3– octupole vibration.

The 206Tl nucleus was populated in the first (commissioning) experiment of

FIPPS facility at ILL Grenoble. The rays from the capture state at 6.5 MeV were measured by the array of 8 Ge clovers. We want to present the preliminary results of

the -coincidence analysis which will allow to significantly extend the experimental information on the energy levels in 206Tl. The 206Tl nucleus, having just one proton-hole and one neutron-hole with respect to the best known doubly magic core 208Pb, is an ideal system for testing old and developing new shell model interactions in the south-west quadrant of the nuclear chart with respect to 208Pb. REFERENCES [1] A. Bohr, B.R. Mottelson, Nuclear Structure, vols. I and II, W.A. Benjamin, 1975. [2] P.F. Bortignon, A. Bracco, R.A. Broglia, Giant Resonances: Nuclear Structure at

Finite Temperature, Harwood Academic Publishers, New York (1998).

Application of Broad Energy Germanium detectors LN2 cooled Si(Li) detectors for

studies of isotopes with large density of excited states at low energy

Martin Venhart

Institute of Physics, Slovak Academy of Sciences

[email protected]

183Hg -> 183Au decay was studied using the TATRA system at ISOLDE facility.

Conversion electrons were detected with the LN2 cooled windowless Si(Li) detector.

The tape system was operated at 8E-8 mbar, therefore no deposition of mist on the

surface of cold detector was observed during the run. The FWHM of 1.2 keV for

conversion electrons above 150 keV was achieved, which is almost comparable with

previous measurement, which employed magnetic spectrometer. Simultaneously, the

gamma rays were detected with array of coaxial and novel Broad Energy germanium

(BEGe) detectors. Very good energy resolution of BEGe detector was used to

construct the level scheme of 183Au, which has large density of excited states at low

energy. In the talk, fundaments of the shape coexistence in odd-Au isotopes,

technical details of system for detection of conversion electrons and level scheme of 183Au will be presented. Technique of level scheme costruction developed in the

present study has large potential for studies of isotopes with high level density and

can be with success applied to neutron-rich isotopes.

Preparation of radioactive lanthanide targets for nuclear physics experiments

S. Heinitz1, E.A. Maugeri1, R. Dressler1, D. Schumann1 1) Paul Scherrer Institute, 5232 Villigen PSI, Switzerland Corresponding author: [email protected] Abstract: Nuclear astrophysics requires accurate knowledge on cross section data for isotopes involved in stellar nucleosynthesis. For the s-process occurring during star evolution, so-called branching point isotopes are especially significant, since here neutron capture and β-decay competes. The measurement of cross section data for these radioactive isotopes is a challenging task due to the limited availability and high activity of the radioisotopes involved. We will report on the production of such branching point isotopes at the high flux reactor at ILL, Grenoble, France, and the following isotope separation performed at our institute. We were successful in separating 140 GBq 171Tm and 2.5 GBq 147Pm from hundreds of milligrams of irradiated, enriched lanthanide seed materials. Two suitable targets containing the separated radioisotopes were prepared by molecular plating and provided to the CERN n_TOF facility for neutron capture cross-section measurements. We will briefly report on the production of targets for these isotopes and give preliminary results of their cross section measurements. This work will also report on the production, separation and characterization of weighable amounts of the 163Ho isotope, which is of substantial interest in the physics community aiming to measure the neutrino mass. Approximately 2 mg of 163Ho have been successfully separated from hundreds of mg of irradiated 162Er. This isotope is also foreseen for neutron cross-section measurements at CERN n_TOF in the near future.

Measuring neutron capture rates on ILL-produced unstableisotopes (79Se, 147Pm, 163Ho, 171Tm and 204Tl) for

nucleosynthesis studies

J. Lerendegui-Marco1, C. Guerrero1, C. Domingo-Pardo2, A. Casanovas3, S. Halfon4,S. Heinitz6, N. Kivel6 , U. Köster7, M. Paul5, R. Dressler6 , D. Schumann6 , M. Tessler5

and The n_TOF Collaboration8

1) Universidad de Sevilla, Sevilla, Spain2) Instituto de Física Corpuscular, Paterna, Spain3) Universitat Politècnica de Catalunya, Barcelona, Spain4) Soreq NRC, Yavne, Israel5) Racah Institute of Physics, Hebrew University, Jerusalem, Israel6) Paul Scherrer Institut, Villigen, Switzerland7) Institut Laue-Langevin, Grenoble, France8) European Center for Nuclear Research (CERN), Geneva, Switzerland

[email protected]

Abstract: Neutron capture cross sections are among the main inputs fornucleosynthesis network calculations. Although well known for the majority of thestable isotopes, this quantity is still unknown for most of the unstable isotopes ofinterest. A recent collaboration between ILL, PSI, U. Sevilla and IFIC aims atproducing the isotopes of interest at ILL, preparing suitable targets at PSI, andmeasuring their capture cross sections at facilities such as n_TOF/CERN and LiLiT.Preliminary results for 147Pm, 171Tm and 204Tl are discussed, along with the currentplans for 79Se and 163Ho.

Nuclear Structure with radioactive muonic atoms

A. Antognini1,2, N. Berger3, D. vom Bruch3, T. Cocolios4, R. Dressler1, A.Eggenberger2, R. Eichler1, P. Indelicato5, K. Jungmann6, K. Kirch1,2, A. Knecht1,

A.Papa1, R. Pohl3, M. Pospelov7,8, E. Rapisarda1, N. Ritjoho1,2, S. Roccia9, N.Severijns4, A. Skawran1,2, F. Wauters3, and L. Willmann6

1) Paul Scherrer Institut, Villigen, Switzerland 2) ETH Zürich, Switzerland 3) University of Mainz, Germany 4) KU Leuven, Belgium 5) LKB Paris, France 6) University of Groningen, The Netherlands 7) University of Victoria, Canada 8) Perimeter Institute, Waterloo, Canada 9) CSNSM/IN2P3, Orsay, France [email protected] Abstract: Muonic atoms as laboratories for fundamental physics provide crucial input to quantum electrodynamics, the weak interaction and the strong interaction. Many studies of muonic atoms have relied on the detection of X-ray from the muonic cascades. Most stable and a few unstable isotopes have been investigated with muonic atom spectroscopy techniques. In particular, muonic atoms have been used to extract the most accurate nuclear charge radii. After the muonic cascade, the capture of the muon by the nucleus produces “one step more neutron-rich nuclei” at high excitation energies offering the possibility to gain structural information on neutron-rich nuclei which can be compared with other standard nuclear reactions for obtaining similar information. Till now, experiments with muonic atoms have been limited by low muon rates, poor beam quality and large muon stop volumes, but also by available detector technology for this environment. While beam intensities and quality have been improved in recent years, still no higher multiplicity spectroscopy of muonic cascades and muonic capture has been performed. A new research project recently started at the Paul Scherrer Institut aims to exploit the potential of high-resolution muonic atom spectroscopy for the precise determination of nuclear charge radii of radioactive isotopes and other nuclear structure properties. The challenge to combine the high energy muon beam with small stopping volumes is being addressed by developing the concept of stopping the muon in a high density, a high pressure hydrogen cell and subsequent transfer of the muon to the element of interest. Status and perspectives of the project will be presented.

Delayed gamma spectroscopy of identified fission fragments

L. Gaudefroy1 1) CEA, DAM, DIF, 91297 Arpajon, France [email protected] Abstract: The delayed gamma spectroscopy of fragments produced via spontaneous fission of 252Cf is studied. A thin 252Cf sample is loaded in a twin ionization chamber allowing performing 2E measurements for each fission events. An excellent mass-resolution of 0.4 amu (FWHM) is achieved for neutron-less fission events making it possible to unambiguously determine the mass of the fragments for these rare events. Ten HPGE detectors surround the chamber in order to study the delayed gamma rays emitted up to 10us after fission. In this talk, after presenting the setup and the general procedure for extracting the mass of the fission fragments I will discuss a first new result on N=100 nuclei interpreted with QRPA calculations.

Thursday, March 23, 2017

Lifetime measurements in neutron-rich Xe isotopes Th. Kröll1, S. Ilieva1, G. Fernández Martínez1, A.-L. Hartig1, C. Henrich1, A. Ignatov1

for the FATIMA&EXILL and FATIMA&GammaSphere collaborations 1) Institut für Kernphysik, TU Darmstadt, Germany [email protected] Abstract: The neutron-rich Xe isotopes (Z=54) are located north-east of the doubly magic shell closures at Z=50 and N=82. In this region of the nuclear chart, the onset of octupole collectivity towards the “magic” octupole numbers Z=56 and N=88 is expected too. The data presented here originate from two experimental campaigns performed at the Institut Laue-Langevin (ILL) in 2013 and the Argonne National Laboratory (ANL) at the turn of the year 2015/2016. The investigated nuclei were populated by neutron-induced fission of 235U and 241Pu (ILL) or spontaneous fission of 252Cf (ANL). Prompt gamma-ray spectroscopy of the fission fragments was performed with combined arrays of high-resolution HPGe detectors and fast LaBr3(Ce) detectors. The Xe isotopes of interest were tagged by gating in the HPGe detectors on one or more of its characteristic transitions. The lifetimes of excited states in the ps regime were determined from the LaBr3(Ce) detectors applying the “Generalized Centroid Difference” (GCD) method [1]. At ILL, the set-up consisted of 8 CLOVER detectors of EXILL combined with 16 LaBr3(Ce) detectors from the FATIMA collaboration [2]. Several lifetimes in the yrast bands of 138,140,142Xe were determined, most of them for the first time [3]. For the first time and more challenging, also two lifetimes in the odd isotopes 139,141Xe were measured. At ANL, the set-up consisted of half of GammaSphere (51 HPGe detectors) and 25 LaBr3(Ce) detectors from the NuSTAR-FATIMA collaboration [4]. The status of the ongoing analyses and selected results will be presented.

[1] J.-M- Régis et al., NIM A 726, 191 (2013)

[2] J.-M- Régis et al., NIM A 763, 210 (2014) [3] S. Ilieva et al., Phys. Rev. C 94, 034302 (2016) [4] E. Gamba et al., contribution to this workshop This work is supported by the German BMBF under grant no. 05P12RDNUP (NuPNET), ILL, the EXILL and FATIMA collaborations, the TU Darmstadt - GSI cooperation contract and HIC for FAIR; the work at ANL is funded by the U.S. DOE contract n. DE-AC02-06CH11357 and used resources of the DOE’s ATLAS facility.

Study of parity-doublet structure in the 147La nucleus.

J. Wi±niewski,1 W. Urban,1 T. Rz�aca-Urban,1

A. G. Smith,2 J. F. Smith,2 G. S. Simpson,3 J. P. Greene,4 and I. Ahmad4

1Faculty of Physics, University of Warsaw, ul. Pasteura 5, PL-00-681 Warsaw, Poland2Department of Physics and Astronomy, The University of Manchester, M13 9PL Manchester, UK

3LPSC, Université Joseph Fourier Grenoble 1, CNRS/IN2P3,Institut National Polytechnique de Grenoble, F-38026 Grenoble Cedex, France

4Argonne National Laboratory, Argonne, IL 60439, USA

email: [email protected]

Only a small percentage of know nuclei has spherical symmetry, most of them are deformed.The problem of nuclear deformation was �rst investigated in 1952 by the A.A. Bohr [1] whosuggested that atomic nuclei can acquire shapes other than spherical through a process calledspontaneous symmetry breaking (SSB). Because shapes of atomic nuclei largely depend on theinteractions between nucleons, nuclear-deformation studies can provide valuable information onnuclear forces, including the so-called residual interactions, responsible for nuclear deformation.In case of octupole deformation, studied in this work, residual interactions correlate nucleonsmoving on orbits which di�er by three units of angular momentum (` = 3), and have di�erentparities. If the Fermi level of a nucleus is located between such levels octupole deformation mayoccur. This happens for aparticular numbers of protons and neutrons, called �octupole magicnumbers� (N,Z = 34, 56, 88, 134). Because the wave functions describing octupole-deformednuclei do not have well-de�ned parity in the intrinsic frame, in the laboratory frame one ob-serves speci�c pattern of excited states, called parity doublet.

The aim of the present study was to reinvestigate the presence of octupole deformation inthe 147La nucleus. The 147La nuclei were produced in spontaneous �ssion of 252Cf and measuredusing the GAMMASPHERE array of Ge detectors. Taking as a starting point schemes proposedin previous works ([2] and [3]), a new scheme of excited states has been proposed for 147La,in which levels and transitions were arranged into a parity-doublet structure, thanks to newlyobserved transitions with energies 558.8, 436.5, 421.4 and 414.25 keV. In order to determinespins and parities of levels, angular correlation were analysed. Intensities of transitions allowedthe determination of dipole moments and gyromagnetic coe�cients. The properties of excitedlevels in 147La, which are consistent with analogous properties observed in octupole-deformednuclei around 147La, support octupole deformation in 147La.

References

[1] A. Bohr, Mat. Fys. Medd. Dan. Vid. Selsk. 26, (1952).

[2] W. Urban et al., �Octupole correlations in the neutron-rich, odd-A lanthanum nuclei�,Phys. Rev. C 54, 945 (1996).

[3] S. J. Zhu et al., �Octupole correlations in the neutron-rich 145,147La nuclei: Coriolis-limit-couplingbands with aligned h11/2 proton�, Phys. Rev. C 59, 1316 (1999).

The first signs of collectivity in the nuclei above 132Sn core.

Houda Naıdja1,2

1 Universite de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France2 LPMPS, Constantine 1 University, 25000 Constantine, Algeria

Contact e-mail: [email protected]

The study of neutron rich nuclei in the vicinity of 132Sn closed core represents currently a greatsubject for nuclear structure research. The advances of new facilities of radioactive ion beamsmade the spectroscopic studies of this region accessible. At the same time the progress in thedevelopment of the effective interactions open up new era of successful theoretical approachesto explore and gain more information from this heavy mass area.

In our previous shell-model works [1, 2, 3] the energy levels, the isomeric transitions and themasses of 134,136,138,140Sn are successfully calculated compared to the observations at RIKEN [1].New progress in our investigation of this region are realized by describing the low-lying spectra,E2 and M1 transition strengths of even-even chain of nuclei with 52 ≤ Z ≤ 60 and 82 ≤ N ≤ 86[4] using an effective interaction based on N3LO portential (named N3LOP). Special attentionis focused to the presence of the collectivity in this mass region, where investigations of thequadrupole properties and the deformation parameters β and γ of N=86 isotones exhibit theoccurance of triaxial γ bands.

1. G. S. Simpson and al., Phys. Rev. Lett 66, 054313 (2013).2. H. Naıdja, F. Nowacki and K. Sieja, Journal of Phys: Conf Series 580, 012030 (2015).3. H. Naıdja, F. Nowacki and K. Sieja, Acta. Phys. Pol. B 46, 669 (2015)4. H. Naıdja and F. Nowacki, accepted in Acta. Phys. Pol. B (2017).

New nuclear structure data after fission on nuclei beyond

132Sn

R. Lozeva1 1) CSNSM, CNRS/IN3P3 and the University Paris-Sud, Orsay, France [email protected] Abstract: Exotic nuclei beyond the 132Sn double-shell closure are influenced by both the Sn superfluidity and the evolving collectivity only few nucleons away. Toward even more neutron-rich nuclei, especially at intermediate mass number, interplay between single-particle and collective particle-hole excitations compete. In some cases with the extreme addition of neutrons also other effects as the formation of neutron skin [1], stabilization as sub-shell gaps [2], and/or orbital crossings [3] may be expected. The knowledge of nuclear ingredients is especially interesting beyond 132Sn and little is known on how the excitations modes develop with the addition of both protons and neutrons [4-7] and for example systematic prompt and decay lifetime studies can be a very sensitive probe. Recently, we have approached this region of nuclei in several measurements following fission as 238U on 9Be target, within the EURICA project [8-9], n-induced fission on 235U/241Pu targets using prompt-decay spectroscopy within the EXILL/FATIMA campaigns [10-11], as well as in decay spectroscopy at LOHENGRIN. Examples from these studies on several nuclei in the region will be presented together with the possible interpretation of the new data. References: [1] B.A. Brown et al, Phys. Rev. Lett. 85, 5296 (2000) [2] S. Sarkar et al, Phys. Rev. C 81, 064328 (2010) [3] M.-G. Porquet et al, Eur. Phys. J. A 25, 319 (2005) [4] P. Bhattacharyya et al, Eur. Phys. Journ. A 3, 109 (1998) [5] S.H. Liu et al, Phys. Rev. C 81, 014316 (2010) [6] R. Kshetri et al, Phys. Rev. C 74, 034314 (2006) [7] T. Rzaca-Urban et al, Eur. Phys. Journ. A 32, 5 (2007) [8] S. Nishimura et al, Prog. Theor. Exp. Phys. 2012, 03C006 (2012) [9] P.-A. Söderström et al, Nucl. Instrum. Meth. Phys. Res. B 317, 649 (2013) [10] P. Mutti et al, ANIMMA (2013), doi:10.1109/animma.2013.6728050 [11] J-M. Regis et al, Nucl. Instr. Meth. Phys. Res. A 763, 210 (2014)

Neutron-rich isotopes from the 238

U(n,f) and 232

Th(n,f) reactions studied with the nu-ball γ-ray spectrometer coupled to the LICORNE neutron source

J.N. Wilson1, M. Lebois1, L. Qi1 1) IPN Orsay, Orsay, France [email protected] Abstract: We have recently successfully demonstrated a new technique for production and study of many of the most exotic neutron-rich nuclei at moderate spins. LICORNE, a newly developed directional inverse-kinematic fast neutron source at the IPN Orsay, was coupled to the Miniball γ-ray spectrometer to study very neutron rich nuclei using the 238U(n,f) reaction. This reaction and 232Th(n,f), are the most neutron-rich fission production mechanisms achievable and can be used to simultaneously populate hundreds of neutron-rich nuclei up to spins of ~16h. High selectivity in the experiment was achieved via triple γ-ray coincidences and the use of a 400ns period pulsed neutron beam, a technique which is unavailable to other reaction mechanisms such as spontaneous fission. The pulsing allows time correlations to be exploited to separate delayed γ rays from isomeric states and supresses unwanted γ-rays from beta decay. New physics results will be presented on neutron induced fission yield anomalies and on the spectroscopy of the neutron-rich 138Te, 100Sr and 96Kr nuclei. In Autumn 2017, the nu-ball array will be operational at the IPN. This high efficiency hybrid Ge-LaBr3 spectrometer based around 24 clover detectors will help to further refine the technique and achieve a large increase in the current observational limit.

Coulomb excitation of refractory fission fragments beam at CARIBU

W. Kortena, D. T. Dohertya, J. M. Allmondb, R. V. F. Janssensc, S. Zhuc, M. Zielinskaa, D. C. Radfordb, A. D.Ayangeakaac, B. Bucherd, J. C. Batcheldere, C. W. Beausangf, C. Campbelld, M. P. Carpenterc, D. Clineg, H. L.Crawfordh, H. M. Davidc, J. P. Delarochei, C. Dickersonc, P. Fallonj, A. Galindo-Uribarri1, F. G. Kondevc, J. L.

Harkerk,c, A. B. Hayesl, M. Hendricksc, P. Humbyf, M. Girodi, C. J. Grossb, M. Klintefjord1, K. Kolosm, G. J. Lanen,T. Lauritsenc, J. Liberti, A. O. Macchiavellij, P. J. Napiorkowskio, E. Padilla-Rodalp, R. C. Pardoc, W. Reviolq, D. G.Sarantitesq, G. Savardc, D. Seweryniakc, J. Srebrnyo, R. Varnerb, R. Vondrasekc, A. Wiensj, E. Wilsonf, J. L. Woodr,

C. Y. Wud

aIrfu, CEA, Universite Paris-Saclay, F-91191 Gif-sur-Yvette, FrancebPhysics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USAcPhysics Division, Argonne National Laboratory, Argonne, Illinois 60439, USA

dLawrence Livermore National Laboratory, Livermore, CA 94550, USAeDepartment of Nuclear Engineering, University of California, Berkeley, Berkeley CA 94702, USA

fDepartment of Physics, University of Richmond, Richmond, VA 23173, USA.gDepartment of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA

hOhio University, Athens, OH 45701, USAiCEA, DAM, DIF, F-91297 Arpajon, France

jNuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USAkDepartment of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA

lDepartment of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USAmDepartment of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA

nDepartment of Nuclear Physics, Research School of Physical Science and Engineering, Australian National University, Canberra, ACT0200, Australia

oHeavy Ion Laboratory, University of Warsaw, Warsaw, PolandpInstituto de Ciencias Nucleares, UNAM, AP 70-543, 04510 Mexico, D.F., MexicoqDepartment of Chemistry, Washington University, St. Louis, Missouri 63130, USA

rSchool of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA

Abstract

We report on the result of several multi-step Coulomb excitation measurement on refractory fission fragments fromthe CARIBU facility at ANL, USA. The experiments were performed with the GRETINA γ-ray and CHICO2 particledetector arrays. A highlight are the the results on 110Ru where we obtained reduced transition probabilities for severallevels near the ground state as well as the quadrupole moment of the first excited 2+ state. These data provide strongevidence for a triaxial shape; a conclusion confirmed by comparisons with the results of beyond-mean-field and triaxialrotor model calculations.

Email address: [email protected] (W. Korten)

Preprint submitted to Elsevier January 6, 2017

Decay of neutron-rich Cd and In studied with GRIFFIN at TRIUMF-ISAC

Paul E. Garrett1

1) Department of Physics, University of Guelph, Guelph, Canada [email protected] Abstract:

-decay half-lives of of nuclei near the r-process path are critical information required for abundance calculations, expecially those near neutron number N=82.

Specifically, the nuclei below doubly-magic 132

Sn are key, and play an important role in the formation and shape of the second r-process abundance peak. Since many of the half lives along the r-process path are yet to be determined experimentally, theoretical calculations are performed to provide the missing data. Large-scale shell model calculations of half lives near N=82 have been benchmarked by adjusting the

quenching of the GT transitions to reproduce the half life of 130

Cd that was reported in Ref. [1]. The resulting half-lives for other nuclei in the region for which measurements are available were known to be systematically too long. Recently, a

shorter half-life was measured for 130

Cd by the EURICA collaboration [2] that would largely resolve this discrepancy by scaling the GT quenching by a constant factor for all of the nuclei in the region. Distinguishing between these discrepant half-life

measurements for 130

Cd was thus of critical importance. The half-lives in this region are challenging to measure due to the significant

-delayed neutron decay branches and the population of isomeric states with half-lives comparable to the ground-states. However, by measuring the time distribution of

-rays rather than that of the particles, these complications can be eliminated. This

requires, however, a very efficient -ray spectrometer. The new GRIFFIN array at TRIUMF-ISAC provides the high efficiency required for these measurements. We

have measured the half-lives of 128–130

Cd to be 246.2(21) ms for 128

Cd, 157(8) ms

and 147(3) ms for the 3/2+ and 11/2- states of 129

Cd and 126(4) ms for 130

Cd [3].

These results improve the precision of the 128,129

Cd half-lives and confirm the

shorter half-life of 130

Cd reported in Ref. [2]. However, the reduced quenching of the GT operator implied by the result leads to a reduction in the calculated half-lives of the other N=82 waiting point nuclei and results in a large discrepancy with the

reported half-life for the decay of 131

In [2], prompting us to remeasure its value.

In addition to the new half lives, the high efficiency of the GRIFFIN spectrometer has enabled us to considerably expand the decay schemes of the

daughter nuclei, and for example in 128

In, the analysis to date has resulted in 23

new -ray transitions and 15 new levels to be identified. [1] M. Hannawald et al., Nucl. Phys. A 688, 578 (2001). [2] G. Lorusso et al., Phys. Rev. Lett. 114, 192501 (2015). [3] R. Dunlop et al., Phys. Rev. C 93, 062801(R) (2016).

Beta-delayed Neutron Spectroscopy of 132

Cd

M. Madurga1, for the VANDLE and IDS collaborations 1) Joint Institute for Nuclear Physics and Applications, Oak Ridge, TN 37831-6374, USA. [email protected] Abstract: The beta decay properties of Z<50, N>82 nuclei have recently attracted considerable experimental and theoretical interest. Efforts have concentrated in the decay of even-even species, as the decay half-life is determined by the energy of the first 1+ state in the odd-odd daughter. This simplicity makes their decay a clean probe of the microscopic nuclear structure in the region. Interestingly, a recent measurement of many new decay half-lives in the region showed large discrepancies with predictions using global models [1]. In order to investigate the origin of this discrepancy, we measured the beta decay of even-even 132Cd. Cadmium ions were produced at the ISOLDE facility (CERN), mass separated and delivered to the ISOLDE decay station. Previous attempts to measure the decay of 132Cd were hampered by the lack of observed gamma transitions, hinting at a neutron branching ratio close to 100% [2]. The VANDLE neutron time-of-flight detector array has allowed us to identify the dominant beta-decay transition to the first 1+ state in 132In for the first time. The resulting spectrum indicates that the 1+ energy is lower than predicted by global models [3]. Shell model calculations in the region indicate lower-than-expected 1+ energies are common in odd-odd nuclei in the region, providing an explanation for the half-lives discrepancy. [1] G. Lorusso et al., Phys. Rev. Lett. 114, 192501 (2015). [2] J. Taprogge et al., Phys. Rev. Lett. 112, 132501 (2014). [3] I. N. Borzov, Phys. Rev. C 67, 025802 (2003).

High-precision mass measurements of neutron-rich nuclei

D. Atanasov1, N. Althubiti2, P. Ascher3, K. Blaum4, M. Breitenfeldt5, R. B. Cakirli4,6, T. Cocolios7, S. Eliseev4, S. George4, F. Herfurth8, J. Karthein4, M. Kowalska5,

S. Kreim4, Yu. A. Litvinov8, D. Lunney9, V. Manea5, M. Mougeot9, D. Neidherr8, M. Rosenbusch10, A. de Roubin4, L. Schweikhard10,

A. Welker1,5, F. Wienholtz5, R. Wolf4, K. Zuber1 1) Institut fur Kern- und Teilchenphysik, Technische Universitat Dresden, Germany 2) University of Manchester, United Kingdom 3) CEN Bordeaux-Gradignan, Gradignan Cedex, France 4) Max-Planck-Institut fur Kernphysik, Heidelberg, Germany 5) CERN, Geneva, Switzerland 6) Department of Physics, University of Istanbul, Turkey 7) IKS, KU Leuven, Leuven, Belgium 8) GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt, Germany 9) CSNSM-IN2P3-CNRS, Orsay, France 10) Ernst-Moritz-Arndt-Universitat, Institut fur Physik, Greifswald, Germany [email protected] Abstract: The mass spectrometer ISOLTRAP [1], situated at ISOLDE/CERN, is a dedicated experimental setup for high-precision mass measurements of short-lived radioactive nuclei. The experiment has developed a combination of state-of-the-art techniques for ion-beam preparation, purification and mass measurement by using ion traps. The multi-reflection, time-of-flight mass spectrometer (MR-TOF MS) [2], now an integral part of the experimental setup, allows identifying both nuclide of interest and contaminants, as well as optimizing on-line the production parameters of the desired radioactive species. Very recently the Phase-Imaging Ion-Cyclotron-Resonance method, developed by SHIPTRAP [3], was successfully commissioned at ISOLTRAP, allowing for high-precision Q-value measurements and fast separation of low-lying isomeric states. The present contribution will give an overview of the mass spectrometry techniques and highlight measurements, important for nuclear structure and astrophysics.

[1] Mukherjee et al., Eur. Phys. J. A 35, 1-29 (2008).

[2] R. Wolf, F. Wienholtz et al., Int. J. Mass. Spectrom. 349-350, 123-133 (2013).

[3] S. Eliseev et al., Phys. Rev. Lett. 110, 082501 (2013).

γ-ray spectroscopy of neutron rich Ag isotopes:

πg9/2 n × νh11/2

m structure and triaxiality

Y. H. Kim1, S. Biswas2, M. Rejmund1, A. Navin1, A. Lemasson1, M. Caamaño3, E.

Clément1, O. Delaune1, F. Farget1, G. de France1, B. Jacquot1 1) GANIL, CEA/DSM - CNRS/IN2P3, Bd Henri Becquerel, BP 55027, F-14076 Caen Cedex 5, France

2) DNAP, Tata Institute of Fundamental Research, Mumbai 400005, India 3) USC, Universidad de Santiago de Compostela, E-15706 Santiago de Compostela, Spain [email protected]

Abstract: The fission process produces neutron-rich nuclides far from stability with

comparable excitation energy and relatively high angular momentum. Therefore it is

used as an important tool to study the variety of different nuclear structures [1]. The

collective band around neutron-rich Ag isotopes have configuration of two intruder

orbitals πg9/2n ×νh11/2

m which presents triaxiality [2, 3]. The interpretations of these

nuclei towards the mid-shell were usually carried out by the deformed basis collective

shell models as- suming deformation in the core and few quasi particles. The view

from large-scale shell model with spherical basis could bring new perspective in this

region, such as unexpected breaking of natural seniority in In arising from proton

neutron interaction [4].

The 113-121Ag isotopes which lie at the borderline of spherical and deformed

basis shell model calculations were studied by exploiting the prompt γ-ray

spectroscopy of the isotopically identified fission fragments using the VAMOS++

spectrometer and the EXOGAM Ge-array at GANIL [5]. Low-lying high-spin states of

neutron-rich 113,118-121Ag have been established for the first time [6]. The excited

states of both odd-A and even-A isotopes followed the smooth systematics of those

in Cd core. A large signature splitting in odd-A isotopes and a signature inversion in

even-A isotopes, which is often used as a finger print of triaxial deformation, through

out long chain of isotopes in 50 < N < 82 region, is striking. The large-scale shell-

model calculations reproduce the experimental spectra and the signature splitting,

revealing their microscopic nature. The natural seniority ordering was broken more

severely than In isotopes [4] inducing strong mixed wave functions.

The main features of signature splitting are reproduced by crude shell model

including only πg9/2 and νh11/2, indicating the yrast band in the Ag isotopes can be

essentially understood based on πg9/2n×νh11/2

m multiplet, without any particular

assumption about the deformation. This simplicity behind the complex structures in

the wave function could be owing to the strong contribution from both proton and

neutron intruder orbitals with unique parity, which makes the configuration of the

band fairly pure. Perspectives of the recent experiment with VAMOS++ and AGATA

γ-ray tracking detectors will be discussed. [1] A. Navin et al., Phys. Lett. B 728, 136 (2014) [2] Y. X. Luo et al., Nucl. Phys. A 919, 67 (2013) [3] P. Möller et al., At. Data and Nucl. Data Tables 98 (2012) 149 [4] M. Rejmund et al., Phys. Lett. B 753, 86 (2016) [5] A. Navin and M. Rejmund, McGrawHill Yearbook of Science & Technology, 137 (2013) [6] Y. H. Kim et al.,(to be published)

QRPA with the Gogny force: a unique formalism to describe low and high energy spectroscopy and beta

decay of fission fragments

S. Péru2, I. Deloncle2, M. Martini3 1) CEA, DAM, DIF, Arpajon, France 2) CSNSM, Orsay, France 3) CEA, ESNT, Saclay, France [email protected] Abstract: We propose a review of several works using the finite range Gogny interaction within QRPA approach: a unique formalism to describe high and low energy spectroscopy as well as collective and individual excitations with or without charge exchange. First, comparison of the low energy spectrum obtained within QRPA and 5DCH (a GCM-like method, including rotational degrees of freedom) is performed for 2+ states in N=16 isotones, Nickel and Tin isotopes [1]. For the first time the different static and dynamic factors involved in the generation of the 2+ states in the Nickel isotopic chain, from drip line to drip line, can be analyzed in only one set of coherent approaches, free of adjustable parameters, using the same interaction and the resulting HFB mean field. After the description of giant resonances in doubly magic exotic nuclei [2], the role of the intrinsic deformation in giant resonances is presented [3]. The appearance of low energy dipole resonances in light nuclei is also discussed. In particular, the isoscalar or isovector nature of Pygmy states is debated [4]. Then, the first fully coherent microscopic description of the multipole spectrum of heavy deformed nucleus 238U is presented [5] as well as results of large-scale calculations undertaken to reproduce dipole responses, both electric and magnetic, for all nuclei for which data exist [6,7]. Strategy for application to odd-A and odd-odd nuclei will be discussed and some examples will be shown. Finally, we present the generalization of QRPA to the charge-exchange nuclear excitations (pnQRPA) [8] namely the Isobaric Analog and Gamow-Teller resonances which play a crucial role in several fields of physics (nuclear physics, astrophysics and particle physics). A comparison of the results with existing experimental data on Fermi and Gamow-Teller strength distributions is presented and the role of nuclear deformation analyzed. A special attention is paid to the calculation of -decay half-lives for which experimental data exist as well as for the specific N = 82 isotonic chain relevant for the r-process nucleosynthesis [9]. For these charge exchange modes some extensions to odd systems will presented to. [1] S. Péru and M. Martini, Eur. Phys. J. A (2014) 50: 88;

[2] S. Péru, JF. Berger, PF. Bortignon, Eur. Phys. J. A 26, 25-32, (2005);

[3] S. Péru, H. Goutte, Phys. Rev. C 77, 044313, (2008);

[4] M. Martini, S. Péru and M. Dupuis, Phys. Rev. C 83, 034309 (2011);

[5] S. Péru, G. Gosselin, M. Martini, M. Dupuis, S. Hilaire and J. -C. Devaux, Phys. Rev. C 83, 014314 (2011);

[6] M. Martini, S. Péru, S. Hilaire, S. Goriely, F. Lechaftois, Phys. Rev ; C 94, 014304 (2016);

[7] S. Goriely, S. Hilaire, S. Péru, M. Martini, I. Deloncle, and F. Lechaftois, Phys. Rev. C 94, 044306 (2016);

[8] M. Martini, Péru and S. Goriely, PRC89, 044306 (2014);

[9] M. Arnould, S. Goriely and T. Takahashi, Phys. Rep. 450, 97 (2007).

Fast timing results from EXILL&FATIMA in the neutron rich region below Z=40

J. Jolie, 1 J.-M. Régis,1 N. Saed-Samii, 1 N. Warr, 1 M. Pfeifer, 1 A. Blanc,2 M. Jentschel, 2 U. Köster, 2 P. Mutti, 2 T. Soldner, 2 G.S. Simpson, 3 F. Drouet, 3 A. Vancraeyenest, 3 G. de France, 4 E. Clément, 4 O. Stezowski, 5 C.A. Ur, 6 W. Urban, 7 P.H. Regan, 8,9 Zs. Podolyák, 8 C. Larijani, 8,9 C. Townsley, 8 R. Carroll, 8 E. Wilson, 8 L.M. Fraile, 10 H. Mach, 10,11 V. Paziy,10 B. Olaizola, 10 V. Vedia, 10 A.M. Bruce, 12 O.J. Roberts, 12 J.F. Smith, 13 M. Scheck, 13 T. Kröll, 14 A.-L. Hartig, 14 A. Ignatov, 14 S. Ilieva, 14 S. Lalkovski, 8,15 W. Korten, 16 N. Marginean, 17 1) Institut für Kernphysik, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany 2) Institut Laue-Langevin, CS 20156, 38042 Grenoble Cedex 9, France 3) LPSC, 53 rue des Martyrs, 38026 Grenoble Cedex, France 4) GANIL, BP 55027, 14076 Caen Cedex 5, France 5) IPN de Lyon, 4, Rue Enrico Fermi, 69622 Villeurbanne Cedex, France 6) INFN, via Marzolo 8, 35131 Padova, Italy 7) Faculty of Physics, University of Warsaw, ul. Hoza 69, PL-00-681 Warsaw, Poland 8) Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom 9) National Physical Laboratory, Teddington, Middlesex, TW11 0LW, United Kingdom 10) Grupo de Fisica Nuclear, FAMN, Universidad Complutense, 28040 Madrid, Spain 11) National Centre for Nuclear Research, ul. Hoza 69, Warsaw, Poland 12) SCEM, University of Brighton, Lewes Road, Brighton, BN2 4GJ, United Kingdom 13) School of Engineering, University of the West of Scotland, Paisley, PA1 2BE, United Kingdom 14) Institut für Kernphysik, TU Darmstadt, Schlossgartenstr. 9, 64289 Darmstadt, Germany 15) Faculty of Physics, University of Sofia, 1164 Sofia, Bulgaria 16) CEA de Saclay, IRFU, 91191 Gif-sur-Yvette, France 17) Horia Hulubei NIPNE, 77125 Bucharest, Romania [email protected] Abstract: Several lifetimes or lifetime limits were measured in the even-even 90Kr, 94Sr, 96Sr and 98Sr isotopes using the EXILL&FATIMA array to perform fast electronic timing on fission products produced after cold neutron capture in 235U. Absolute values and limits for the lifetimes of the lowest yrast states could be determined. The results are compared to state-of-the-art Monte Carlo Shell Model calculations and confirm the Type II phase coexistence observed in this mass region for the Sr isotopes. A comparison with several Energy Density Functional calculations is also presented.

Nuclear structure across neutron-rich N=60 using Coulomb excitation of radioactive ion beams

G. Georgiev

CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91405 Orsay, France [email protected] Abstract: The region of nuclear deformation around neutron-rich A~100 has attracted considerable attention since its prediction [1] and especially after its first experimental confirmation [2]. It witnesses one of the most impressive onset of deformation throughout the nuclear chart right across N=60. Nuclear ground-state deformation in the region was experimentally observed between Rb (Z=37) and Mo (Z=42). In addition, the shape coexistence right below (N ≤ 59) is not readily explained in the standard interpretation [3]. The experimental studies in the region have been facilitated due to the possibility to populate those nuclei as fission products of heavy elements. Some important recent contribution to those experimental investigations have come for the Kr isotopes through mass measurements [4] and Coulomb-esxcitation [5] studies. Those both reveal that the ground-state deformation in the krypton‘s develops only gradually. In an attempt to shed light on the underlying single-particle structure, responsible for the peculiarity of the region, we performed a Coulomb excitation study of a chain of rubidium isotopes at REX-ISOLDE. The nuclei of interest, 93,95,97,99Rb, were produced using an UCx target and were post-accelerated to about 2.8 MeV/u. They were further sent to a secondary

target in the centre of the Miniball array, which was used for the detection of the -rays, in coincidence with the beam particles, detected by a position-sensitive Si strip detector. Prior to the present study information on excited states was only available for 93Rb. In our measurement, the previously known low-energy level scheme of 93Rb was confirmed. Very similar single-particle like pattern was observed as well for 95Rb. The sudden change in the structure appears at 97Rb, as could be anticipated from previous nuclear moments and charge-radii measurements [6]. This was experimentally observed through the identification of rotational bands, built on the ground states of 97Rb and 99Rb, from multi-step Coulomb excitation. The B(E2) transition probabilities between a number of excited states in these isotopes were determined as well. The results from the present study [7] suggest that a fine balance between a spherical shell gap at Z=38, for N≤58, and a deformed one, at N=60 and above, might be one of the main reasons for the sudden onset of the deformation. The practical absence of any mixing between these well-defined spherical and deformed structures allows for the appearance of this most-sudden onset of deformation throughout the nuclear chart and defines 97Rb as the corner stone of the region of deformation around A~100. [1] D. Arseniev, et al., Nucl. Phys. A139, 269 (1969). [2] E. Cheifetz , et al., Phys. Rev. Lett. 25, 38 (1970). [3] K. Heyde and J.L. Wood, Rev. Mod. Phys. 83, 1467 (2011). [4] S. Naimi, et al., Phys. Rev. Lett. 105, 032502 (2010). [5] M. Albers, et al., Phys. Rev. Lett. 108, 062701 (2012). [6] C. Thibault, et al., Phys. Rev. C 23, 2720 (1981). [7] C. Sotty, et al., Phys. Rev. Lett. 115, 172501 (2015).

SPECTROSCOPY OF NEUTRON-RICH 94,96Y ISOTOPE PRODUCED IN FISSION

INDUCED BY COLD NEUTRONS

Łukasz W. Iskra, Institute of Nuclear Physics PAN, Krakow, Poland

Ł. W. Iskra1, B. Fornal1, S. Leoni2,3, G. Bocchi2,3, A. Blanc4,S. Bottoni2,3,N. Cieplicka-Oryńczak1, M. Jentschel4,

U. Köster4, C. Michelagnoli4,5, P. Mutti4, T. Soldner4, G. de France5, G. S. Simpson6, C. A. Ur7, W. Urban8

1 Institute of Nuclear Physics, PAN, 31-342 Krakow, Poland

2 Dipartimento di Fisica, Universit_a degli Studi di Milano, I-20133 Milano, Italy

3 INFN sezione di Milano via Celoria 16, 20133, Milano, Italy

4 ILL, 71 Avenue des Martyrs, 38042 Grenoble CEDEX 9, France

5 GANIL, BP 55027, 14076 Caen CEDEX 5, France

6 LPSC, 53 Avenue des Martyrs, F-38026 Grenoble, France

7 INFN Sezione di Padova, Padova, Italy

8 Faculty of Physics, Warsaw Univ., ul. Pasteura 5, PL-02-093 Warsaw, Poland

The onset of the deformation in neutron-rich nuclei around A = 100 mass region has for many years remained

one of the most interesting subjects for nuclear spectroscopy study. For the neutron number N = 60, a sudden onset

of the deformation has been observed at the ground state, which is manifested by the presence of rotational bands

(e.g. [1]). On the other hand the occurrence of shape coexistence in nuclei with N = 58 and 59, in this region (e.g.

[2]), suggests that the evolution of the deformation is a more gradual process. In the yttrium isotopic chain, a

rotational band above the 4-, 496-keV isomer has been observed in the N = 59, 98Y nucleus, while there was no

evidence of the deformed structure in the Y isotopes with neutron number less than N = 59. Our goal was to

investigate N = 57, 96Y isotope where only a few states were known from beta decay study of 96Sr [3] as well as the

long 9.6-s (1140-keV) isomer [4]. Additionally, we decided to investigate whether deformed structures are still

present in the 94Y nucleus which lies 5 neutrons away from the N=60 boundary. So far, very little spectroscopic

information has been gathered on 94Y – what regards higher spin yrast excitations established was only the presence

of the 1.35-μs, (5+) isomer at 1202 keV excitation energy [5]. This isomer could be used as a starting point for the

identification of structures on top of it.

The yttrium-94 and 96 isotopes have been produced by fission of 235U and 241Pu targets induced by cold

neutron from the reactor at Institut Laue-Langevin. The level scheme up to excitation energies in excess of 5 MeV

has been established based on multi-fold gamma-ray coincidence relationships measured with the EXILL

spectrometer [6] which consists of up to 46 HPGe detectors. By exploiting delayed- and cross-coincidence

techniques, extensive structure has been delineated. During the analysis, over 50 new gamma transitions which feed

previously known low-spin states as well as the long 9.6-s, 8+ isomer in 96Y isotope have been identified. Moreover,

a new isomeric state at 1655-keV excitation energy has been located with half-life of 201 ns. Angular correlation

analysis allows to define spin-parity assignment for most of the identified levels, in particular (6+) for new isomer.

By using the delayed-coincidence method it was possible to identify above the 201-ns state a few weak transitions,

which seem to form a rotational band, in analogy to the structure above the 4- isomer in the 98Y isotope. In the case

of 94Y isotope over 11 new gamma transitions, which feed the previously known (5+) isomer, have been identified.

Angular correlation analysis supported by shell-model consideration allowed to propose spin-parity assignments

for some of the new levels.

The existence of the new isomeric state and the possible deformed band built on that isomer in the N = 57, 96Y

isotope shed new light on the study of the onset of deformation in neutron-rich nuclei around N = 60. It shows that

the deformed structures appear just after the subshell closure at N = 56 and evolve smoothly when passing through

N = 57-59 isotopes, to became a ground state structure in the 99Y isotope, i.e., at N = 60. The findings are in line

with the 94Y results where only spherical structures are present at low excitation energy.

REFERENCES

[1] E. Chiefetz, R.C. Jared, S.G. Thompson, J.B. Wilhelmy, Phys. Rev. Lett. 25 (1970) 38.

[2] W. Urban et al., Nucl. Phys A 689, 605 (2001).

[3] G. Jung et al., Nucl. Phys. A 352, 1 (1981).

[4] R. Stippler et al., Z. Phys. A 284, 95 (1978).

[5] J. Genevey et al., Phys. Rev. C 59, 82 (1999).

[6] M. Jentschel et al., EXILL technical paper, JINST (subm. 2015).

Shape coexistence in 96,98Sr

E. Clément1, M. Zielińska2*, A. Görgen3, W. Korten2, S. Péru4, H. Goutte1,2, S. Hilaire4, D.T. Doherty2,5,

and the IS451 collaboration 1) GANIL, Caen, France 2) IRFU/SPhN, CEA, Université Paris-Saclay, Gif-sur-Yvette, France 3) University of Oslo, Norway 4) CEA DAM, DIF, Arpajon, France 5) University of Surrey, Guildford, UK *[email protected] Abstract: The structure of neutron-rich 96,98Sr isotopes was investigated by low-energy Coulomb excitation of radioactive beams at the REX-ISOLDE facility. Reduced transition probabilities and spectroscopic quadrupole moments were extracted from the differential Coulomb excitation cross sections. These results allow for the first time to draw definite conclusions about the shape coexistence of highly deformed prolate and spherical configurations. In particular, a very small mixing between the coexisting states is observed, contrary to other mass regions where strong mixing is the rule. The experimental data suggest a significant contribution of the triaxial degree of freedom in the ground state of both isotopes. In addition, experimental information on low-lying states in 98Rb has been obtained.

Spin-alignment in abrasion-fission reaction – g-factor measurement of isomeric states

J.M. Daugas1,2, F. Boulay1,2,3, G.S. Simpson4, Y. Ichikawa2, A.Takamine2, D.S. Ahn2,

K.Asahi2,5, H.Baba2, D.L. Balabanski2,6, T. Egami7, T. Fujita2,8, N. Fukuda2, C. Funayama5, T. Furukawa9, G. Georgiev10, A. Gladkov2,11, M. Hass12,

K. Imamura2,13, N. Inabe2, Y. Ishibashi2,14, T. Kawaguchi7, T. Kawamura8, W. Kim11, Y. Kobayashi15, S. Kojima5, A. Kusoglu10,16, S. Momiyama17, I. Mukul12, M. Niikura17,

H. Nishibata8, T. Nishizaka7, A. Odahara8, Y. Ohtomo2,5, D. Ralet10, T. Sato5, Y. Shimizu2, T. Shimoda8, T. Sumikama2, H. Suzuki2, H. Takeda2, L.C. Tao2,18,

Y. Togano5, D. Tominaga7, H. Ueno2, H. Yamazaki2, X.F. Yang19 1) CEA, DAM, DIF, Arpajon, France; 2) RIKEN Nishina Center, Wako, Japan; 3) GANIL, Caen, France; 4) LPSC, Grenoble, France; 5) Tokyo Institute of Technology, Japan; 6) ELI-NP, Magurele, Romania; 7) Hosei University, Japan; 8) Osaka University, Japan; 9) Tokyo Metropolitan University, Japan; 10) CSNSM, Orsay, France; 11) Kyungpook National University, Daegu, Korea; 12) Weizmann Institute, Rehovot, Israel; 13) Meiji University, Tokyo, Japan; 14) University of Tsukuba, Japan; 15) University of Electro Communications, Tokyo, Japan; 16) Istanbul University, Turkey; 17) University of Tokyo, Japan; 18) Peking University, China; 19) KU Leuven, Belgium [email protected] Abstract: The spin-alignment of fragments produced in spontaneous and neutron-induced fission reactions is found to be up to 40%. This amount of spin-alignment

allows the measurement of gyromagnetic factors of s isomeric states using the well known TDPAD method. This observable is a very sensitive probe of the single-particle structure of nuclear states and frequently allows one to determine the valence nucleon configuration. Isomers produced by spontaneous fission are difficult to measure due to their low production rates and the ones produced by neutron-induced fission and selected in a spectrometer could not be measured because one needs to have fully stripped isotopes to preserve the spin-alignment in the vacuum. The measurement performed at the RIKEN Nishina Center accelerator using the abrasion-fission reaction of a 238U80+ beam at 345 MeV/u energy on the N=59 99mZr and 98mY will be presented. The obtained results show the opportunity to

perform gyromagnetic factors measurement of neutron-rich s-isomers produced by the abrasion-fission reaction.

Collectivity in the vicinity of 78

Ni:

Coulomb excitation of neutron-rich Zn at HIE-ISOLDE

A. Illana1, M. Zielinska2, P. van Duppen1, M. Huyse1 and IS557 collaboration 1) KU Leuven, Leuven, Belgium 2) CEA Saclay, Gif-sur-Yvette, France [email protected] Abstract: Nuclei in the vicinity of 78Ni have recently been in focus of many experimental and theoretical investigations. In particular, the neutron-rich Zn isotopes, only two protons above the Ni isotopic chain, are ideally suited to study the evolution of the Z = 28 proton shell gap, and the stability of the N = 50 neutron shell gap. In the last decade, several experiments were performed to study the collectivity in the even-even Zn isotopes between N = 40 and N = 50 [1-4], but their results are not consistent; consequently, the evolution of nuclear structure in the neutron-rich Zn nuclei is not fully understood. The ISOLDE facility finished in 2016 the first phase of a major upgrade in terms of the energy of post-accelerated exotic beams bringing it up from 3 MeV/u to 5.5 MeV/u. The increased beam energy strongly enhances the probability of multi-step Coulomb excitation, giving experimental access to new excited states and bringing in-depth information on their structure. The very first HIE-ISOLDE beam experiment in October 2015 and its continuation in 2016 have been dedicated to the study of the evolution of the nuclear structure along the zinc isotopic chain. The preliminary results discriminate between the two experimental values of B(E2; 4+ → 2+) in 74Zn, and yield for the first time a B(E2; 4+ → 2+) value in 78Zn. [1] J. Van de Walle, et al. Phys. Rev. Lett. 99 14501 (2007). [2] J. Van de Walle, et al. Phys. Rev. C, 79:014309 (2009). [3] M. Niikura et al., Phys. Rev. C 85 054321 (2012). [4] C. Louchart, et al. Phys. Rev. C, 87:054302 (2013).

Shell-model study of Gamow-Teller and first–forbidden β decay in the N=28 region

Y. Utsuno1,2, S. Yoshida3, N. Shimizu2, T. Otsuka3, T. Togashi2, M. Honma4, T. Suzuki5

1) Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Japan 2) Center for Nuclear Study, University of Tokyo, Tokyo, Japan 3) Department of Physics, University of Tokyo, Tokyo, Japan 4) Center for Mathematical Sciences, Aizu Univeristy, Aizu-Wakamatsu, Japan 5) Department of Physics, Nihon University, Tokyo, Japan [email protected] Abstract: Neutron-rich nuclei around 48Ca have recently attracted much theoretical and experimental interest from the viewpoint of the appearance of a new magic number, N=34, and the disappearance of the N=28 magic number around 42Si. These properties are well described by large-scale shell-model calculations with the SDPF-MU interaction [1], where shell evolution due to the tensor force plays a crucial role. In this contribution, we present our recent shell-model results for β-decay properties in this region. First, we have carried out systematic shell-model calculations of β-decay half-lives and neutron emission probabilities for 78 nuclei with 13≤Z≤18 and 22≤N≤34, including odd-A and odd-odd nuclei, by calculating their Gamow-Teller distributions. β-decay half-lives are one of the most easily accessible observables by experiment, and existing data covers very neutron-rich nuclei. Neutron emission probabilities are sensitive to low-lying nuclear structure. The present calculation gives an excellent agreement with experimental half-lives and β-decayed neutron emission probabilities. The calculation shows that a sort of “pygmy” Gamow-Teller resonance develops for the decays of even-even (0+) to odd-odd (1+) nuclei and dominates observed half-lives and neutron emission probabilities. It is most likely that proton-neutron pairing make a significant contribution to this property. Second, we have calculated first-forbidden β-decay half-lives of neutron-rich K isotopes to probe nuclear structure of neutron-rich Ca isotopes beyond N=28. We have succeeded in reproducing experimental logft values for the decays of 50-53K, and have obtained useful information on shell evolution from the comparison to the data. In particular, we have identified energy levels associated with neutron excitation across the N=28 gap in 50,51Ca and a level dominated by neutron excitation across the N=32 gap in 53Ca. [1] Y. Utsuno et al., Phys. Rev. C 86, 051301(R) (2012); Phys. Rev. Lett. 114,

032501 (2015)

Valence particle – core excitations couplings: new experimental investigations and a novel theoretical approach

S. Bottoni1,2,*, G. Bocchi1,2, N. Cieplicka-Oryńcza3, S. Leoni1,2, B. Fornal3, G. Coló1,2, P.F. Bortignon1,2 and the EXILL collaboration

1) Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy 2) Istituto Nazionale di Fisica Nucleare Sezione di Milano, Via Celoria 16, 20133 Milano, Italy 3) Institute of Nuclear Physics, Polish Academy of Sciences, PL-31342 Kraków, Poland *[email protected]

Abstract: We present a new microscopic model [1,2] aimed at describing the structure of nuclei with one- to few-valence nucleons with respect to a doubly-magic core, in the medium-heavy mass regions. The model accounts for both collective and non-collective excitations, including couplings between particles and phonon excitations of the core, in a self-consistent way. The core excitations are calculated with Hartree-Fock (HF) and Random Phase Approximation (RPA) approaches, using the Skyrme effective interaction. The theoretical outcomes will be discussed and compared with experimental results obtained for nuclei located around the doubly magic 132Sn and 40,48Ca cores and produced in neutron-induced fission and neutron-capture reactions, during the EXILL experimental campaign at the Laue-Langevin Institute in Grenoble. The agreement between theory and experiment will be outlined along with possible future developments. [1] G. Colò et al., to be published. [2] S. Bocchi et al., Phys. Lett. B 760, 273 (2016).

Friday, March 24, 2017

High-statistics reactor antineutrinos for fission and beta-decay studies

A. Letourneau1 1) Irfu, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France [email protected] Abstract: With the availability of high-statistics and high-resolution reactor antineutrino experiments dedicated to neutrino oscillation measurements (Daya-Bay, Double-Chooz, Reno, Stereo, …..) we can now envisage to use these measurements as integral experiments to constrain fission and beta-decay models and nuclear decay-data libraries. Weak interaction occurs in neutron-rich nuclei by transmuting a neutron into a proton. This transition connects two states: one in the neutron-shell and one in the proton-shell, with features that influence the energy spectrum of the beta-emitted (electron and antineutrino) particles. Measuring the characteristics (shape and end-point) of these particles should give insight on the structure of the beta-emitter nuclei. Measuring the electron-energy spectra for selected nuclei is the easiest and most convenient way. Unfortunately it faces two major problems. The first one is that it requires a high-resolution electron spectrometer, as the BILL spectrometer running at ILL in the 80’s, with large dynamic to cover the full energy range of very neutron-rich nuclei (up to 8 MeV). The second one is that the electron-energy spectrum suffers from corrections due to electromagnetic perturbations in the nucleus, the atom and the target. Another approach would be to use the antineutrino-energy spectra measured in reactor antineutrino experiments. This method is less selective as the emitted antineutrino energy spectrum results from the combination of several components but offers the advantage of an integral measurement with an electromagnetically-unperturbed probe. In this presentation I will review the ingredients for a reactor antineutrino-energy spectra modelling, their current limitations and knowledge, review the already existing measurements with their related questions, and I will discuss the quantities we could extract from the measured antineutrino energy spectra and with which new data they could be completed.

Precisely Measured Electron Spectra from Fission Products, the Missing Piece in the Reactor Antineutrino

Puzzle

A. A. Sonzogni1, E. A. McCutchan1 1) National Nuclear Data Center, Brookhaven National Laboratory, Upton, NY 11777, USA [email protected] Abstract: The Daya Bay collaboration has recently published a precise measurement of the inverse beta decay cross section folded antineutrino spectrum, revealing a 5.4% antineutrino deficit beyond the three-flavor neutrino oscillation as well as a spectral distortion. This deficit is compatible with earlier nuclear reactor antineutrino experiments as analyzed by Mention et al, who showed a systematic deficit of antineutrinos at short distances, an effect referred to as the ‘reactor neutrino anomaly’. The obvious question is whether this deficit is due to the presence of one (or more) sterile neutrinos, or simply an unknown component in the underlying nuclear physics used in the predictions. In this work, we explore three possibilities in the latter group. First, we study the feasibility of the 238U contribution and the effective Z used in the conversion method as possible sources of the disagreement by adjusting them to match the measured Daya Bay spectrum. Both scenarios are considered unlikely: the adjusted 238U antineutrino spectrum has an unphysical shape and smaller integral than expected from systematic trends, while the fitted Z effective would correspond to fission products with negligible fission yield. Motivated by the fact that 75% of a reactor antineutrino spectrum in the region relevant to the anomaly is accounted for by the decay of fewer than 50 nuclides, it is then possible that individual shape corrections arising from first forbidden transitions or second order terms such as weak magnetism may not cancel out, which led us to explore the sensitivity of the Daya Bay spectrum to experimental shape factor corrections. We find that using a linear term equal to +6%/MeV in the conversion method results in a much closer agreement with the Daya Bay spectrum. Unlike the two previous cases, this scenario cannot be ruled out as there is currently an absence of precisely measured electron spectra from the relevant fission products. Previously, it was noted how important beta intensities and fission yields are for the summation method. This sensitivity analysis highlights the importance of experimental shape factors for both conversion and summation calculations. One possible way forward to confirm the existence of the anomaly, or even quantify it, would be to precisely measure the electron spectra for the relevant nuclides, incorporate these data in summation calculations to understand their effect, and finally, through an average procedure, include them in a conversion calculation.

Work at Brookhaven National Laboratory was sponsored by the Office of Nuclear Physics, Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-98CH10886.

Modular Total Absorption Spectrometer the powerful array to study the beta-strength

and anti-neutrino properties

M.Wolińska-Cichocka 1;2;3, B.C. Rasco 2;3;4, K.P. Rykaczewski 2, R. Grzywacz 2;3;4, D.W. Stracener 2, N.T. Brewer 2;3;4, A. Fijałkowska 4,5, M. Karny 5, T. King 4,

and E.F. Zganjar 6 1) Heavy Ion Laboratory, Univ. of Warsaw, Warsaw, Poland 2) Physics Division, Oak Ridge National Laboratory, Oak Ridge, USA 3) Joint Institute for Nuclear Physics and Applications, Oak Ridge, USA 4) Department of Physics and Astronomy, Univ. of Tennessee, Knoxville, USA 5) Faculty of Physics, Univ. of Warsaw, PL 02-093 Warsaw, Poland 6) Louisiana State Univ., Baton Rouge, USA [email protected] (M.Wolińska-Cichocka) Abstract: The Modular Total Absorption Spectrometer (MTAS) [1-3] has been designed, constructed and commissioned at Oak Ridge National Laboratory. MTAS consists of ~1000 kg of NaI(Tl) detector material divided into 19 hexagonal modules

and is surrounded by over 5000 kg of mostly lead shielding. The MTAS -ray efficiency for full single gamma energy absorption is about 82% at 500 keV and 72% at 5 MeV [3]. The total gamma absorption spectroscopy is necessary to obtain the

true β-decay strength pattern and for following determination of β- and -energy released from fission products [4]. At ORNL, were have measured over 70 decays of 238U fission products. It includes 22 decays of high priority for decay heat analysis [4]. The 142Cs → 142Ba→ 142La → 142Ce was among the studied chains. The 142Cs activity is the third most important contributor to the high energy ῡ spectra in nuclear reactors [5,6,7]. The decays, of 142Ba and 142La are good test cases, since these decays were studied previously with total absorption spectrometer [8] and using high energy resolution techniques. MTAS spectra show a good agreement with known data for 142Ba → 142La → 142Ce chain. The β-decay for 142Cs → 142Ba was substantially corrected [7]. The conclusions on decay heat and anti-neutrino properties will be presented. This work was supported by the US DOE, Office of Nuclear Physics. [1] M. Wolińska-Cichocka et al., NDS 120, 22, 2014 [2] B. C. Rasco et al., NIM A788, 137, 2015 [3] M. Karny et al., NIM A836, 83 2016 [4] “Assessment of fission product decay data for decay heat calculations”, OECD NEA No 6284, 2007, vol. 25, ISBN 978-92-64-99034-0 [5] A.A. Sonzogni et al., PR C 91, 011301, 2015 [6] D.A. Dwyer et al., PRL 114, 012502, 2015 [7] B. C. Rasco et al., PRL 117, 092501, 2016 [8] R.C. Greenwood et al., NIM A390, 95, 1997


Fission studies at VAMOS

F. Farget1, M. Caamaño2, D. Ramos2, C. Rodríguez-Tájes1,2, K.-H. Schmidt1, L.

Audouin3, J. Benlliure2, E. Casarejos4, E. Clément1, D. Cortina2, O. Delaune1, X.

Derkx1, A. Dijon1, D. Doré5, B. Fernández-Domínguez2, L. Gaudefroy6, C. Golabek1,d,

A. Heinz7, B. Jurado8, A. Lemasson1, C. Paradela2, T. Roger1, M.D. Salsac5, and C.

Schmitt1

1) GANIL, CEA/DRF-CNRS/IN2P3, F-14076 Caen, France 2) Universidade de Santiago de Compostela, E-15706 Santiago de Compostela, Spain 3) CNRS/IN2P3, Université Paris-Sud 11, Institut de Physique Nucléaire, F-91406, Orsay, France 4) Universidade de Vigo, E-36310 Vigo, Spain 5) CEA, Irfu, Centre de Saclay, F-91191 Gif-sur-Yvette, France 6) CEA DAM Île-de-France, BP 12, 91680 Bruyères-le-Châtel, France 7) Fundamental Fysik, Chalmers Tekniska Högskola, SE-41296 Göteborg, Sweden 8) CENBG, UMR 5797 CNRS/IN2P3, Universit é Bordeaux, F-33175 Gradignan, France [email protected] . Abstract: Inverse kinematics is a new tool to study nuclear fission. Its main advantage is

the possibility to measure with an unmatched resolution the atomic number of fission

fragments, leading to new observables in the properties of fission-fragment

distributions. In addition to the resolution improvement, the study of fission based on

nuclear collisions in inverse kinematics beneficiates from a larger view with respect to

the neutron-induced fission, as in a single experiment the number of fissioning

systems and the excitation energy range are widden. With the use of spectrometers,

mass and kinetic-energy distributions may now be investigated as a function of the

proton and neutron number sharing. The production of fissioning nuclei in transfer

reactions allows studying the isotopic yields of fission fragments as a function of the

excitation energy. With the access of kinematics properties, the charge polarisation of

fragments at scission is now revealed with high precision, and it is shown that it

cannot be neglected, even at higher excitation energies. Results on fissioning systems 238

U, 239

Np, 240

Pu, 244

Cm, obtained in transfer reactions are presented, together with

the fusion reaction leading to the compound nucleus 250Cf at an excitation energy of

45MeV.

Fission study project in RIKEN RIBF

~ towards the “complete” measurement of fission observables ~

M. Sasano1, A. Andreyev5,6, T. Aumann2, M. Bohmer3, M. Dozono, R. Gernhauser3, W. Henning4, K. Hirose5, T. Kobayashi7, Y. Matsuda7, S. Mitsuoka5, T. Motobayashi1, D. Mucher, I. Nishinaka5, K. Nishio5, R. Orlandi5, H. Otsu1, V. Panin1, S. Reichert3, M. Sako1, H. Sato1, Y. Shimizu1, L. Stuhl9, E. Takada10, T. Nakamura11, Y. Kondo11, Y. Kubota1, T. Kubo1, N. Inabe1, H. Suzuki1, N. Fukuda1, D. Kameda1, H. Takeda1, T. Uesaka1, L. Werner3, J. Yasuda12, J. Zenihiro1 1RIKEN Nishina Center, Japan 2TU Darmstadt, Germany 3TU Munchen, Germany 4ANL, USA 5ASRC JAEA, Japan 6University of York, UK 7Tohoku University, Japan 8Kyoto University, Japan 9CNS University of Tokyo, Japan 10HIMAC at NIRS, Japan 11Tokyo Institute of Technology 12Kyushu University [email protected] Abstract: In RIKEN RIBF, we are working on the experimental project to measure the fission barrier height and fission fragment distributions on unstable nuclei using intense RI beams. The (p,2p) direct reaction will be used as a clean reaction to populate the hole state in heavy unstable nuclei of interest. Experimentally, we will measure the excitation energy of the state and simultaneously will provide the information on whether fission occurs or not as well as what kinds of fission fragments are emitted with what momentum vectors. As a big advantage of the inverse kinematics, this set of the information would be given even by event as a set of correlated observables, which will, for the first time, lead to a “complete set” of fission observables and enables a completely new approach to analyse this phenomenon. For example, combining the information of the excitation energy with the information on whether fission occurs or not, one could know the fission “threshold” energy, which roughly speaking corresponds to the fission barrier height defined as the highest point of the potential energy surface. Around this point, we will be able to measure the fission fragment distributions as a function of the mass and charge number of both fragments. This will enhance the shell effect on the fission fragment pattern through the removal of the washout effect based on this excitation energy selection around the fission barrier height. The experimental programs are aiming to perform these measurements in neutron-rich / proton-rich sides of stable U isotopes, covering the transient region where the asymmetric fission pattern changes to symmetric ones. That will provide strong constraints on the nuclear models which can be used for predicting the role of fission recycling along the r-process path and the ending point of the path. The actual experiments have not yet still be done. In this talk, we will present the development of the new (p,2p) setup required for this project.

Gamma-beam photofission experiments at ELI-NP: The future is emerging*

D. L. Balabanski1 1) ELI-NP, IFIN-HH, Bucharest-Magurele, Romania [email protected] Abstract: The Extreme Light Infrastructure (ELI) Pan-European facility initiative represents a major step forward in quest for extreme electromagnetic fields. Extreme Light Infrastructure – Nuclear Physics (ELI-NP), which is under construction in Magurele, Romania, is one of the three pilars of the ELI, and aims at utilization of extreme electromagnetic fields for nuclear physics and quantum electrodynamics research and applications. It is one of the three Pan-European nuclear physics laboratories, which are at present under construction in the EU under the ESFRI scheme. At ELI-NP, high-power laser systems together with brilliant gamma beams are the main research tools. The status of the construction of the facility will be reported. The emerging experimental program with brilliant gamma beams at ELI-NP will be presented with emphasis on the prepared day-one photofission experiments. The physics cases of the flagship experiments at ELI-NP will be discussed, as well as the related instruments which are under construction for their realization. *This work is supported by Extreme Light Infrastructure – Nuclear Physics (ELI-NP) – Phase II, a project co-financed by the European Union through the European Regional Development Fund through the Competitiveness Operational Programme “Investing in Sustainable Development”


NAME FIRST NAME AFFILIATION E-MAIL

Ackermann Dieter GANIL [email protected]

Al-Adili Ali Uppsala University [email protected]

Andreev Andrey University of York [email protected]

Ansari saba Irfu, CEA, Université Paris-Saclay, France [email protected]

Atanasov Dinko Technische Universitaet Dresden [email protected]

Audouin Laurent Université Paris-Sud audouin@ipno,in2p3,fr

Balabanski Dimiter ELI-NP, IFIN-HH dimiter,balabanski@eli-np,ro

Ballof Jochen CERN ISOLDE / Uni Mainz jochen,ballof@cern,ch

Belier Gilbert CEA/DAM/DIF gilbert,belier@cea,fr

Blanc Aurelien ILL blanc@ill,fr

Bottoni Simone Università degli Studi di Milano and INFN simone,bottoni@mi,infn,it

Chebboubi Abdelaziz CEA abdelaziz,chebboubi@gmail,com

Chietera Andreina Irfu Cea/Saclay andreina,chietera@cea,fr

Cieplicka-Orynczak Natalia Institute of Nuclear Physics PAN [email protected]

Daugas Jean-Michel CEA, DAM, DIF [email protected]

Devlin Matthew Los Alamos National Lab [email protected]

Doré Diane CEA/Saclay [email protected]

Dubey Santwana Johannes Gutenberg University, Mainz [email protected]

Egelhof Peter GSI Darmstadt [email protected]

Farget Fanny IN2P3 [email protected]

Faust Herbert Institut Laue-Langevin [email protected]

Fernández Martínez Guillermo Technische Universität Darmstadt [email protected]

Flanagan Kieran University of Manchester [email protected]

Foligno Daniela CEA [email protected]

Fornal Bogdan IFJ PAN Krakow [email protected]

Franchoo Serge IPN Orsay [email protected]

Gamba Eugenio University of Brighton [email protected]

Garrett Paul University of Guelph [email protected]

Gaudefroy Laurent CEA [email protected]

Georgiev Georgi CSNSM [email protected]

Goennenwein Friedrich Physikalisches Institut [email protected]

Heinitz Stephan Paul Scherrer Institut [email protected]

Higgins Daniel LANL [email protected]

Illana Sison Andres KU Leuven [email protected]

Iskra Lukasz Institute of Nuclear Physics [email protected]

Jansson Kaj Uppsala University [email protected]

Jentschel Michael ILL [email protected]

Jolie Jan Institut für Kernphysik, Universität zu Köln [email protected]

Julien-Laferriere Sylvain CEA Cadarache DEN/DER/SPRC/LEPH [email protected]

Kelly Keegan Los Alamos National Laboratory [email protected]

Kessedjian Gregoire LPSC [email protected]

Kiggins Courtney US Air Force SMC [email protected]

Kim Yung Hee GANIL [email protected]

Koester Ulli ILL [email protected]

Korten Wolfram CEA Saclay [email protected]

Kroell Thorsten TU Darmstadt [email protected]

Leoni Silvia University of Milano and INFN [email protected]

Lerendegui Marco Jorge Universidad de Sevilla [email protected]

Letourneau Alain CEA-Saclay [email protected]

Lozeva Radomira CNRS [email protected]

Madurga Flores Miguel Joint Institute for Nuclear Physics and Applications - UTK [email protected]

Marini Paola CEA [email protected]

Materna Thomas IRFU - CEA Saclay [email protected]

Meplan Olivier LPSC meplan@lpsc,in2p3,fr

Michelagnoli Caterina ILL [email protected]

Mutti Paolo Institut Laue-Langevin [email protected]

Naidja Houda IPHC and université Constantine1 houda,naidja@iphc,cnrs,fr

Nishio Katsuhisa Advanced Science Research Center, Japan Atomic Energy [email protected]

Oberstedt Andreas ELI-NP [email protected]

Peck Marius Technical University of Darmstadt, Institute for nuclear [email protected]

Peru Sophie CEA [email protected]

Petrache Costel University Paris Sud and CNRS/IN2P3 [email protected]

Rapala Michal SPhN - CEA Saclay [email protected]

Rapisarda Elisa Paul Scherrer Institute [email protected]

Ray Amlan Variable Energy Cyclotron Center, Kolkata, India [email protected]

Regis Jean-Marc Institute of Nuclear Physics [email protected]

Sagaidak Roman Flerov Laboratory of Nuclear Reactions, Joint Institute for sagaidak@jinr,ru

Sage Christophe LPSC/CNRS [email protected]

Sasano Masaki RIKEN Nishina Center [email protected]





mailto:meplan@lpsc,in2p3,fr



Savajols herve GANIL-CNRS [email protected]

Serot Olivier CEA-Cadarache [email protected]

Simpson Gary LPSC [email protected]

Sonzogni Alejandro National Nuclear Data Center [email protected]

Sosnin Nikolay The University of Manchester [email protected]

Stuttgé Louise IPHC-CNRS [email protected]

Tamagno Pierre CEA [email protected]

Tovesson Fredrik Los Alamos National Laboratory [email protected]

Utsuno Yutaka Japan Atomic Energy Agency [email protected]

Vardaci EMANUELE UNIV. OF NAPLES AND INFN [email protected]

Venhart Martin Institute of Physics, Slovak Academy of Sciences [email protected]

Wilson Jonathan IPN Orsay [email protected]

Wisniewski Jakub Faculty of Physics, University of Warsaw [email protected]

Wolinska-Cichocka Marzena Heavy Ion Laboratory University of Warsaw [email protected]

Zielinska Magda CEA Saclay [email protected]



· pdf file6th workshop on nuclear fission and spectroscopy of neutron-rich nuclei programme...

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