reactions with fast radioactive beams – lecture i · 2011. 9. 5. · spin-orbit splitting reduced...

+

Reactions with fast radioactive beams – lecture I Thomas Nilsson Chalmers University of Technology

EUROSCHOOL lectures 2011-08-24-25

+Lectures planning

n  The “whys” and “hows” of fast radioactive beams n  “Fast?” – focus on relativistic RIBs!

n  Structured after reaction mechanisms n  What physics do we address? n  What do we need to detect? n  What are the challenges and the next steps?

n  “Home-blind” with respect to GSI and the path towards FAIR n  … but most things valid also for other in-flight facilities

n  What the lectures not will cover exhaustively: n  Reaction theory n  High-resolution spectroscopy with fast beams(e.g. PRESPEC/HISPEC with AGATA) n  Intermediate-energy reactions n  EOS physics n  …


+Some hot topics to be addressed with RIBs


+ Central Topics for NuSTAR at FAIR


  Quest for the limits of existence

  Halos, Open Quantum Systems, Few Body Correlations

  Changing shell structure far away from stability

  Skins, new collective modes, nuclear matter, neutron stars

  Phases and symmetries of the nuclear many body system

  Origin of the elements

è unified theory (ab-initio, density functional, shell model)

… a “shopping-list” also valid for RIBF, FRIB, SPIRAL-2, HIE-ISOLDE, ISAC-2,…!

Neutron halos, skins – collective modes


132Sn

Soft mode discovered at GSI

Neutron Skins Neutron stars Pygmy Resonance

EOS

Halos

Shell quenching and reordering: Transition from SO gaps (50,82,126) to HO gaps (40,70,112)

Softening of the nuclear potential: High-l pushed upward and Spin-Orbit splitting reduced N~Z

N>>Z

Drastic Changes in Shell Structure far from stability


N=16

A. Ozawa et al. PRL 84 (2000) 5493

T. Otsuka et al., PRL 87(2001)082502 R. Kanungo et al, PRL 102 (2009) 152501; R. V. F. Janssens, Nature 459 (2009) 1069

EUROSCHOOL lectures 2011-08-24-25 H. Simon ● Limits of existence of Light Nuclei

19,20,22C @ 40 MeV/u 10 counts/h

è rms matter radius: 5.4 ± 0.9 fm

10 keV

420 keV

S2n:

PRL 104 (2010) 062701

Nuclear Astrophysics at FAIR


rp-, p-process:   masses at & beyond the proton drip-line   (p,γ), (γ,p) rates

è Combine accurate nuclear physics with precision astronomy to constrain astrophysical scenarios

r-process:   masses, half-lives   β-delayed neutron emission   (γ,n), (n,γ) rates   shell structure

FAIR will provide unique access to many nuclei relevant in explosive nucleosynthesis

+

Spins momenta

Beta-decay

Momentum distributions, cross sections

Invariant mass

Unbound nuclei

Masses

Transfer reactions

Experimental tools Elastic

scattering


+Fast radioactive beams – why? n  Production by the in-flight

technique (vs ISOL) n  Chemical blindness

n  Shortest half-lives

n  Experimental issues n  Doppler boosted

n  Kinematical focusing

n  Resolution

n  Small energy loss

n  Possible to use thick targets

n  Ions, particles are hard to stop

n  Can use many detectors – ion-by-ion tracking


Ranges in silicon

p 40Ar 238U

10 MeV/u (ISOL + post-acc.)

700 µm 127 µm 107 µm

500 MeV/u (Relativistic in-flight)

63 cm 7.6 cm 1.8 cm

+Fast radioactive beams – where?

n  GSI since SIS (early 90’s)

n  Intermediate-energy RIBs (tens of MeV/u) since many years at GANIL, MSU, RIKEN

n  Future (and current) facilities n  RIBF@RIKEN

n  FRIB@MSU

n  FAIR-NuSTAR-R3B

EUROSCHOOL lectures 2011-08-24-25 LISE-3@GANIL

+

Bending Magnet Superconducting Large B L (7Tm) Large pole gap (80cm) Weight ~ 600 ton

Neutron

Proton

H I

TPC

(not shown

Spectroscopy of Unbound States e.g. (γ,n)

(p,2p) Missing Mass Nucl. Astrophys. (p,γ) Deuteron expts for 3NF Nucl. Matter

d setup

(not shown in picture)

15M$ covers

SC-Magnet 9M$ Detectors

neutron counter electronics, software

STQ for BT

S U Spect o ete obayas et a 0

versatile spectrometer with a large superconducting magnet


FRIB – to be constructed at MSU

+


RIPS GARIS

60~100 MeV/nucleon ~5 MeV/nucleon

350-400 MeV/nucleon

Old facility

New facility

RIKEN RI Beam Factory (RIBF)

BigRIPS

SRC

RILAC

AVF

RRC fRC

IRC

Experiment facility

Accelerator

SHARAQ (CNS)

SAMURAI

ZeroDegree

SLOWRI

SCRIT

RI-ring

SHE

(eg. Z=113)

Intense (80 kW max.) H.I. beams (up to U) of 345AMeV at SRC Fast RI beams by projectile fragmentation and U-fission at BigRIPS Operation since 2007

To be funded

In phase II

<10 MeV/nucleon

CRIB (CNS)

J 2010 S i l2 Poster by Simon Boissinot

+ Radioactive beams – production and separation


1 GeV

1 MeV

1 keV

1 eV

fragmentation (FRS)

deceleration cooling(storage rings)

post-acceleration

isotope separationon-line (ISOL)

E/A

target-ion source

+ FRS@GSI Bρ - ΔE – Bρ separation Method


+Identification of incoming ions


ββγγρρB

ZA

cme

u

==

Bρ – from position at middle focal plane of the FRS

β – from TOF

Z – from ΔE

Poster by Ana Henriques

+Nuclear STructure, Astrophysics and Reactions – RIBs@FAIR


+Super-FRS – radioactive beams at FAIR


 Energy (0 – 1.5 GeV/u)

 Halflives (µs è s)

82

82

50

50

28

20

8

28

20

N

Z

+ Production of exotic nuclei at relativistic energies


Sn isotope production

+ Production of exotic nuclei at relativistic energies


+ The Super-FRS


Central instrument for the NuSTAR programme

Z

Super-FRS

FRS30X

10X

Two-stage separation yields isotopic nuclear beams

Fission

Fragmentation

I II

I II

  High acceptance for projectile fragments and fission products

  Two-stage separation absolutely needed for clean beams

  More than one order of magnitude transmission gain relative to FRS

+Super-FRS - Technical Challenges


SC Multiplets Remote Handling

Target & Beam Catcher

SC Dipoles

Cryogenics

Radiation Resistant Magnets

+Fast radioactive beams – why?

n  Reaction mechanisms n  Knock-out

n  Inner shells

n  “Clean” process

n  QFS

n  Coulomb dissociation

n  Spallation

n  Fission

n  Multifragmentation

n  ASY-EOS


+Fast radioactive beams – how?

n  Fixed-target experiments n  Complete kinematics measure everything with

n  100% efficiency n  4π solid angle n  Perfect resolution n  … ;)

n  Specialised set-ups n  Active targets n  …

n  Ring experiments n  Cooled beams n  Low-q experiments n  Precision measurements


+R3B reaction types


+ One-nucleon Removal Reaction in Inverse Kinematics

EUROSCHOOL lectures 2011-08-24-25 Needs: Fragment ID and spectroscopy (+gamma rays)

Measure momentum distribution of knocked-out nucleon through momentum of core:

pnucleon = −p A−1X( )

- l-value from momentum distribution of core - tag excited core states with γ-rays

Example : 9Be(17C,16C+γγ)X

V. Maddalena et al., Phys. Rev. C 63 (2001) 024613. EUROSCHOOL lectures 2011-08-24-25

+


Bending Magnet Superconducting Large B L (7Tm) Large pole gap (80cm) Weight ~ 600 ton

Neutron

Proton

Heavy Ion

TPC


Spectroscopy of Unbound States e.g. (γ,n)

(p,2p) Missing Mass Nucl. Astrophys. (p,γ) Deuteron expts for 3NF Nucl. Matter

d setup


15M$ covers

SC-Magnet 9M$ Detectors

neutron counter electronics, software

STQ for BT

SAMURAI Spectrometer Kobayashi et al 2011-

versatile spectrometer with a large superconducting magnet

Jan2010 Spiral2

Determine:   (x,y) è αdef   ∆E è Z   ∆t è β

è (A,Z), P

+Large-area hodoscopes – time and energy


t1, e1

t2, e2

tl, el

tr, er

tu, eu

td, ed

P T

L

E

time

d1d2

t1

t2

e1e2

H.T. Johansson thesis 2010

e1 = E exp

(

−d1

λ

)

e2 = E exp

(

−d2

λ

)

E =

√

e1e2 exp

(

d1

λ+

d2

λ

)

= expL

2λ·√

e1e2,

P =d2 − d1

2=

λ ln Ee2− λ ln E

e1

2= λ

ln e1 − ln e2

2.

t1 = T +1

vd1

t2 = T +1

vd2

T =t1 + t2

2−

d1 + d2

2v=

t1 + t22

−L

2v

P =

(

d2 − L2

)

+(

L2− d1

)

2=

d2 − d1

2=

v(t1 − T ) − v(t2 − T )

2= v

t1 − t22(

+ A-selectivity requires better position resolution, e.g. scintillating fiber detector

Position resolution ~ 1mm Complemented by hodoscopes


+ Gain matching (phase1_gfi) Before After


+R3B fragment ID

 RPCs promising technology for TOF walls


Large Area ToF-wall for heavy ions: iToF

Design and construction of RPCs prototypes and front-end

ü  Requirements:

àConceptual design àRPC technology

Results with prototypes tested with relativistic heavy ions

pulse-shape analysis Ø  adapted to heavy ions Ø  time resolution: <50 ps(sigma)

Ø  surface ~1.5x1.5 m2

Ø  position resolution: <5mm Ø  multi-hit capabilities

G10 (2mm)

Cu tape

nylon (0,3mm)

soda-lime glass (1mm)

HV Q=2-6 & 28

Q=1

ü  study of efficiency of ions detection

good efficiency for heavy ions !!!!

E. Casarejos, Santiago de Compostela

CheckBox1

S277 experimentP.Maierbeck et al.

MUSIC1�

MUSIC2�

TPC3,4� TPC5,6�

Primary beam�40Ar @ 700MeV/u�

~1010 part/spill��

Production target�9Be 4g/cm2�

TOF1�

TPC1,2�

TOF2�S4

S2

S0 MINIBALL�

9Be 1720 mg/cm2�

Knockout target�

FRS used as a spectrometer


C.Rodríguez-Tajes et al, Phys. Rev. C82(2010)024305 and Phys. Rev. C83(2011) 064313

R. Kanungo et al, PRL 102 (2009) 152501; R. V. F. Janssens, Nature 459 (2009) 1069

+One-neutron removal from 22N

(MeV/c)z

p−200 0 200

(arb

. u

nit

s)z

/dp

σd

N22


- structure and role of N=14 subshell

C. Rodrìguez-Tajes et al, Phys. Rev. C, 83(6), 06 2011

(MeV/c)z

p

(arb

. u

nit

s)z

/d

pσ

d

−200 0 200

N18

−200 0 200

N19

−200 0 200

N20

−200 0 200

N21

Strong 1s1/2 component – halo signature

+R3B reaction types


…also a production method for “tertiary beams” – e.g. unbound systems!

Reactions resulting in 7He

From

D.H. Denby et al., PR C78 (2008) 044303


+

n

2H 1H 3H 12.3 y

5H unbound

7H unbound

3He 4He 5He unbound

6He 808 ms

7He unbound

8He 119 ms

9He unbound

10He unbound

6Li 7Li 8Li 840 ms

9Li 179 ms

10Li unbound

11Li 8.5 ms

7Be 8Be unbound

9Be 10Be 1.6 106 y

11Be 13.8 s

12Be 23.6 ms

13Be unbound

14Be 4.35 ms

12Li unbound

13Li unbound

Beams: 8He – 240 MeV/u 11Li – 287 MeV/u 14Be – 304 MeV/u

S245@GSI - Unbound Light Nuclei


+ S245 Experimental Setup


Complete kinematics

Target

+Reactions with Relativistic Radioactive Beams@GSI 1992

n  S034 - First complete-kinematics experiment using RIBs at GSI (SIS+FRS) – 11Be, 11Li, 8He@~270 MeV/u

n  First use of knock-out reactions to study unbound systems – 10Li from 11Li/11Be


M. Zinser, F. Humbert, T.N. et al Phys. Rev. Lett. 75 (1995)1719

+

Yu. Aksyutina et al. PLB 666(2008)430

Proton knockout from 304 MeV/u 14Be

n  S245@GSI


Needs:   Fragment ID and momentum spectroscopy   Neutron spectroscopy   (+gamma rays)

Large Area Neutron Detector

Resolution: σTof ~ 200 ps σp ~ 5 - 10 MeV/c σIVM ~ 0.1 - 1. MeV

1

Neutron Energy (MeV) Nucl. Instr. Meth. A314 (1992) 136 Hadronic shower producing charged particles

200 paddles, active volume 2x2x1 m3

+


Observables

,02

∑∑ −⎟⎠

⎞⎜⎝

⎛=

ii

iiCxn mPE

Relative energy: => positions, widths of resonances

where − four-momentum, − rest masses of reaction products.

iP0im

(x,y,z) → (θ,φ) four-momentum => correlations ToF → velocity

+

ε  =1.47(19)MeV

S2n = 1.26(13) MeV

1H(14Be,2pn)12Li

E fn = P f +

P n − M f −mn


Going beyond the dripline…


as = −13.7(1.6) fm

What resolution is needed?

+ 1H(14Be,2n)13Li

n  … and even further


… and even further

2/722

22

2 )21.2( nfn

nf

nf ESE

dEd

+=

σ

Er = 1.47(31) MeV

C. Forssén et al. NPA 673 (2008) 143


+ Relative-energy spectrum of 1H(11Li,2p)10He


Yu. Aksyutina

0+

2+

H.T. Johansson et al, Nucl. Phys. A847(2010)66-88, doi:10.1016/j.nuclphysa.2010.07.002

11Li* Fit

Neutron detector NeuLAND Working group coordinator: K. Boretzky (GSI)

NeuLAND :

20 XY-Planes

2000 Paddles

4000 Photomultiplier

Weight: ca. 19000 kg

G. Ickert - Juni 2011

Existing LAND detector:   σt< 250 ps   σx,y,z ≈ 3 cm   Size: 2 x 2 x 1 m3

  Plastic scintillator / Fe converter sandwich structure

Improvement of multi-n recognition, minimised non-active volume

+R3B reaction types


Electromagnetic excitation at high energies

High velocities v/c≈0.6-0.9 ⇒ High-frequency Fourier components

Eγ,max ≈ 25 MeV (@ 1 GeV/u)

b>RP+RT Pb

Absorption of

‘virtual Photons’

σelm ~ Z2

Semi-classical theory:

dσelm / dE = Nγ(E) σγ(E)

Determination of ‘photon energy’ (excitation energy) via a kinematically complete

measurement of the momenta of all outgoing particles (invariant mass) T. Aumann

Experimental Approach: Production of (fission-)fragment beams

ββγγρρB

ZA

cme

u

==

Bρ – from position at middle focal plane of the FRS

β – from TOF

Z – from ΔE LAND

Ø  Primary: 3*108 238U/spill @550MeV/u Ø  Secondary (mixed): 50 ions 132Sn/spill (~10/sec @500 MeV/u)

132Sn

Experimental Approach II: The LAND reaction setup @GSI

Excitation energy E* from kinematically complete measurement of all outgoing particles:

Neutrons

ToF, ΔE

LAND tracking → Bρ ∼ A/Qβγ

Charged fragments

Photons ALADIN large-acceptance dipole

ToF, x, y, z

Crystal Ball and Target

projectile tracking

~12 m

Mixed beam

Needs:   Fragment ID and momentum spectroscopy   Neutron spectroscopy   Gamma rays – sum energy

The collective response of the nucleus: Giant Resonances

Isovector Isoscalar

Monopole (GMR)

Dipole (GDR)

Quadrupole (GQR) Be

rman

and

Ful

z, R

ev. M

od. P

hys.

47 (1

975)

47

208Pb

120Sn

65Cu

Photo-neutron cross sections

Electric giant resonances

The collective response of the nucleus: Giant Resonances

Isovector Isoscalar

Monopole (GMR)

Dipole (GDR)

Quadrupole (GQR)

Photo-neutron cross sections

Electric giant resonances new collective soft dipole mode

(Pygmy resonance)

Prediction: RMF (N. Paar et al.)

132Sn

?

Dipole-strength distributions in neutron-rich Sn isotopes

Electromagnetic-excitation cross section

Photo-neutron cross section

P. Adrich et al., PRL 95 (2005) 132501

stable

radioactive

PDR   located at 10 MeV   exhausts a few % TRK sum rule   in agreement with theory

GDR   no deviation from systematics

P. Ring et al.

Poster by Mark-Christoph Spieker

Low-lying dipole strength in the 132Sn mass neighborhood

odd nuclei allow extending (γ,n) measurements to lower excitation energies

→ comparison to (γ,γ') data for stable isotopes

Data for stable nuclei from: A.Zilges et al., PLB 542,43 (2003) S.Volz et al., NPA 779, 1 (2006) N. Ryezayeva et al., PRL 89 (2002) K. Govaert et al., PRC 57,2229 (1998)

5 MeV < E* < 9 MeV

A. Klimkiewicz et al., PRC 76 (2007) 051603(R)

►136Xe D. Savran et al.,

PRL 100, 232501 (2008) S-DALINAC data

RQRPA – DD-ME N. Paar et al.

Result (averaged 130,132Sn) :

a4 = 32.0 ± 1.8 MeV

po = 2.3 ± 0.8 MeV/fm3

PDR strength versus a4, po

S(ρρ) : moderate stiffness

Neutron skin thickness

δr Rn-Rp

Rn – Rp : 130Sn: 0.23 ± 0.04 fm 132Sn: 0.24 ± 0.04 fm

LAND

Sn isotopes

A.Krasznahorkay et al. PRL 82(1999)3216

A. Klimkiewicz, N. Paar, et al,

submitted to PRL

Can we learn something on neutron (-rich) matter from experiments with radioactive beams ?

The nuclear equation of state: dependence on n-p asymmetry and density

symmetry energy and its density dependence close to saturation density → properties of n-rich nuclei ? (neutron skin, dipole response, ...)

symmetry energy at higher densities → reactions with n-rich nuclei ?

symmetry energy at low density → multifragmentation ?

compressibility → Giant Monopole Resonance

Neutron Star

+Gamma rays


Crystal Ball   4π gamma detector (*1980 - ?)   162 NaI(Tl) crystals of 20 cm

length

+Doppler boost – gamma rays

1 MeV@500 AMeV 1 MeV@1000 AMeV


CALIFA/R3B R&D

Beam

~130 ~40

~20

BARREL ✓

FORWARD

ENDCAP – major challenge! LaBr/LaCl Phoswich? CSIC+Chalmers

General design of the detector based on kinematical considerations

 “Egg” shape  Highly segmented  Thick detection volume  Scintillation based  Performant photo-sensors

13 cm

Crystal and photosensors Barrel àCsI+APD

Real shape, 1MeV γ

◊ ΔΕ/Ε ∼ 5 %

1cm3 and 662 keV γ

WG Coordinator: Dolores Cortina-Gil, Univ. Santiago de Compostela

Engineering design and Mechanical structure à based on carbon fiber

CALIFA/R3B R&D status

+That’s all for today!


n  Tomorrow: n  Quasi-elastic scattering

n  Elastic scattering - ring experiments

n  Data analysis/reconstruction

n  …

n  Outlook

reactions with fast radioactive beams – lecture i · 2011. 9. 5. · spin-orbit splitting reduced...

Documents