The Fragment Mass Analyzer (FMA)and

The Study of Proton Emitters

Darek Seweryniak filling in for

Cary N. DavidsATLAS 25th Anniversary Celebration

October 22, 2010

What Can a Recoil Separator Do for Us?

• Separates reaction products from primary beam particles at 0º.

• Focuses and disperses the reaction products at the focal plane by M/Q (Mass/Charge). The M/Q groups are physically separated from one another.

• With achromatic optics, we can measure particle energy using time-of-flight, since, for a given energy, all paths are isochronous.

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Fragment Mass Analyzer (FMA)

• Solid Angle acceptance 8 msr

• Energy acceptance ± 20%

• M/q acceptance ± 7%

• M/q dispersion 0 → 20 mm/%

•Mass resolution 1/350

• Length 8.2 m

3

Ion Optics of the FMA

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The FMA at ATLAS

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FMA Focal Plane M/Q Spectrum

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Types of Experiments Performed at the FMA

• Fusion-evaporation reactions at 0º, e.g. 92Mo(78Kr,p2n)167Ir

• Transfer reactions, e.g. 2H(56Ni,p)57Ni, 4He(44Ti,p)47V.

• Radiative capture reactions, e.g. H(18F,γ)19Ne

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Chronology I

• Proposal prepared for DOE in 1986, based on Legnaro design having one quadrupole doublet at the entrance. Submitted to DOE June 1986.

• Competition with ORNL. Approval awarded to ANL in summer 1987.

• Immediately began design study with consultant Dan Larson. Tried symmetric quadrupole doublets, which showed performance vastly improved over just one.

• Prepared Request for Quotations, sent to vendors in the spring of 1988.

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Chronology II

• FMA Contract awarded to Bruker GmbH in Karlsruhe in summer of 1988. Includes 2 quadrupole doublets, 2 electric dipoles, 1 60 degree bending magnet, Hall probe magnetometer, all magnet power supplies. Expected delivery: 1 year.

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Chronology III• New addition to Target Room 3 ready in early

1989.

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Chronology IV

• Developed internal 300 kV power supplies for electric dipole. Shipped to Karlsruhe along with vacuum equipment in 1989 for factory tests on dipoles. Conditioned up to 255.5 kV on each plate (511 kV across gap). Assistance on various trips provided by Birger Back, Walter Kutschera, and Thomas Happ.

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Chronology V• FMA components delivered in the summer of

1990 (2 years). Immediately began assembly.

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Chronology VI

• A few months into assembly, a safety incident at ATLAS caused a shutdown of the accelerator (Tiger Teams descended on ATLAS). This benefited the FMA assembly because technical manpower was available whenever needed.

• FMA assembly was completed in the summer of 1991. Obtained the first mass spectrum in August, aided by Akunuri Ramayya, Birger Back, and Walter Kutschera.

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16

FMA statusas of 8am 10/22/2010

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Spontaneous Proton Emission one of the early experimental programs in collaboration with Univ. of Edinburgh

Analogous to α decay No pre-formation factorDecay rates sensitive to Ep and lpUnique laboratory to study

tunneling through a 3D barrierSource of information on nuclear

structure and masses far from stability

Γp important for (p,γ) cross sections in light p-rich nuclei in the path of the rp-process

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Proton Decay Observables

Ep, T1/2, bpA,Z(odd)

βα

Jπ

p p’

2+

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A-1,Z-1(even)

r

rucr pp

pp

p

ppp

jl

jl

Kjl

insideK

)()( ∑=ψ

22

pppp jlsph

jl Nkµτhh

==Γ

∑ Γ++

==Γpjpl

pp

p

pjplp

sphjl

Kppp

defK cIKRKj

IR 22

012

)12(2τh

0+

Proton emitter landscape

15 new isotopes!

~20 mass units away from the line of stability

Often less exotic neighbors not known

new subfield in nuclear structure emerged and even triggered a series of conferences on proton emitting nuclei

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167Ir – 1st new proton emitter observed at ATLASJune 1994

Experiment to search for 171Ag78Kr+96Ru->171Ag+p2n

Instead found:167Ir+αp2n

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Deformed proton emitters at ANL

First deformed proton emittersAnomalous decay rates explained by introducing deformation

First fine structure

Spherical

Axially deformed

Odd-odd axially deformed

Coupling to vibrations

Non-axial deformation

Theory by C.N. DavidsandH. Esbensen

A. Sonzogni et al., PRL 83 (1999)1116C.N. Davids et al., PRL C55 (1997)2255

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Rotational bands in the deformed proton emitter 141Ho

7/2-[523] ½+[411]

Unexpectedly large

signature splittingindicates

triaxial shape!

β=0.25(4) from Harrisformula

σ = 300 nb out of 500 mb

D. Seweryniak et al., PRL C86(2001)1458

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121Pr proton emitterrecent developments

non-adiabatic quasi-particle calculations withCoriolis interaction

adiabatic calculations

Partial rotational alignmentσ = 300 pb

A. Robinson et al., PRL 95, (2005) 032502 M.C. Lopes et al., Phys. Lett. B 673 (2009) 15

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To be continued …

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Highlights of Research with the FMAand

Future Perspectives

Darek Seweryniakfor FMA “collaboration”

ATLAS 25th Anniversary Celebration October 22, 2010

Research with the Fragment Mass Analyzer

γ ray emission from resonances in rp-process nuclei

Proton emitters

Transfermium nuclei

56Ni(d,p), 44Ti(α,p), 18F(p,γ)

100Sn

Ab-initio life times

mirror nuclei

Shape coexistence at Z=82

48Ca

N=82

N=Z nuclei around A=80

Sub-barrier fusion

26 Phys. Rev. Lett11 Phys. Lett.104 Phys. Rev., Z. Phys., Nucl. Phys., Eur. J. Phys.

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Experiments with the Fragment Mass Analyzer

From 10Be to 257RfMostly proton- but also neutron-rich nucleiStable and radioactive beamsStable and radioactive targetsRadiative capture, transfer, fusion-evaporation and everything in betweenIn-beam spectroscopy at the target positionDecay spectroscopy at the focal planeNuclear structure, reactions, astrophysics, …

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Selected results obtained with the FMA

101Sn

56Ni

254No

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CD2 foil

Au attenuator

beam integrator

Si detector array (25% of 4π)

56Ni beam

proton

57Ni

d(56Ni,p)57Ni

Fragment Mass Analyzer

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31

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56Ni(p,γ) reaction rate higher than previously assumed. More material can pass through the 56Ni bottleneck towards heavier nuclei

Reaction rate:

r=NpNNi ∫ vσ(v)f(v)dv

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GAMMASPHERE+FMA

GAMMASPHERE and FMA with its auxiliary detectors is a unique combination of a large γ-ray efficiency and high reaction channel selectivity.

Implementation of a novel technique Recoil-Decay Tagging resulted in observation of many exotic nuclei across the nuclidic chart.

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Recoil-Decay Tagging

Two orders of magnitude more sensitive than any previously

used methods!

Clover Ge

HPGeX-array

GAMMASPHERE

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Prompt γ rays RecoilsImplants Spatial and time

correlationsin the DSSD

γFragment Mass Analyzerγ PPAC

p

B

EEβBeam

Q Q QQ M/QRecoils80X80 DSSD

Ep,T1/2

characteristic decays or chains of decays:

ProtonsAlphasβ-delayed particlesIsomersβ decay

Spectroscopy of Trans-Fermium Nuclei

neutron number

111

112

113

114

117

115

118

116

160 162

164 166 168 170 172 174

176 178 180 182 184

152 158156154

Mt 266

Db 262 Db 263

Sg 266

Db 258Db 256 Db 260Db 257

Rf 260 Rf 261 Rf 262 Rf 263Rf 259Rf 256Rf 255 Rf 258

Bh 261 Bh 262

Rf 257

Db 261

Sg 260 Sg 261 Sg 263Sg 259

Bh 264

Bh

Hs

Ds

Sg 258

Lr 259

No 258

Lr 260

No 259

Lr 261 Lr 262

No 262No 260

Lr 258

No 257

Lr 255

No 254

Lr 254

No 253

Lr 257

No 256

Lr 256

No 255

Md 257

Fm 256

Md 258

Fm 257

Md 259 Md 260

Fm 258 Fm 259

Md 256

Fm 255

Md 253

Fm 252

Md 252

Fm 251

Md 255

Fm 254

Md 254

Fm 253

Es 255 Es 256Es 254Es 251Es 250 Es 253Es 252

Cf 255 Cf 256Cf 253Cf 250Cf 249 Cf 251 Cf 252 Cf 254

110/273110/271

111/272

CHART OF THE NUCLIDES

No

Md

Fm

Es

Cf

prot

on n

umbe

r

150

Db

Rf

Lr

No

Md

Fm

Es

Cf

Z = 114

108Hs 267Hs 265Hs 264

a

a

a

a

a

a

110/270

Hs 266

Sg 262

112/285

9.1539 s

Z/A

T1/2

E (MeV)α

110/269

Mt 268

α

EC

β-

SF

112/277

110/267

MtHs 269 Hs 270

Sg 265

Sg

a

aa

a

a

a

a

a

a

a

a

a

a

a

a a

a

aa

aa

108/275

110/279

106/271

112/284112/282

114/286 114/287

10.01

114/288

9.95

116/290

115/288115/287

113/284113/283

111/280

109/276

107/272

111/279

109/2 57

116/291

10.85 10.74

112/285

110/281

114/289

9.82

9.169.54

9.30

8.53

10.00

10.4610.59

10.12

9.75

9.71

9.02

10.37

10.33

105/268

15 ms

32 ms 87 m s

6.3 m s

0.1 s

0.15 s

0.17 s

0.72 s

9.8 s

16 h

9.7 m s

0.48 s

0.1 s0.5 m s

3.6 s

0.18 s

2.4 m in

9.6 s

34 s

0.56 s 0.63 s 2.7 s0.16 s10.20

112/2834.0 s

a

116/292

10.6616 ms

107/2 17

116/29353 ms

1.8 ms118/294

11.65

105/267

1.2 h

10.53

9.70

104/268104/2672.3 h

48 238 249Ca + U.... Cf

208 50 70Pb + Ti.... Zn

Chart courtesy of Y. Oganessian

Cold fusion with208Pb, 209Bi targets

GSI, Riken

Hot fusion with 48Ca beamsDubna, LLNL

K-isomers, α-decay fine structure, in-beam

ANL, Dubna, GSI, JYFL

254No

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254No – first in-beam spectrum in a Transfermium nucleus

gs rotational band: β=0.27254No survives up to 14hbar

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254No - Entry point distribution 215 MeV 219 MeV

Maximum spin 22 hbarShell-correction persists at high spinFission barrier > 5MeV

2010 experiment – G. Henning et al.

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254No – K-isomers

Stringent test of spe including the states relevant for the shell gaps in super-heavy nuclei

Conversion electrons

γ rays

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Where are the magic gaps? Macroscopic/Microscopic (MM), Skyrme (SHF) & Relativistic (RMF) mean field.

X

X

?

Proton gap (~2.2 MeV) at 114 – if WS continues to apply for Z>102.

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100Sn physics

Self-conjugate

Z

GT β-decay

super allowedα-decay

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spe

p decay

100Sn

rp processend point

Doubly-magic

n-n interactions

Nβp

100Sn region experimental status

101Sn 102Sn 103Sn

102In101In99In 100In98In

101Cd

99Ag 100Ag

99Pd

104Sb

105Te

103Sb

99Cd 100Cd98Cd97Cd96Cd

95Ag94Ag 96Ag 97Ag 98Ag

94Pd 95Pd 96Pd 97Pd 98Pd93Pd92Pd

106Te

108I

109Xe

112Cs

114Ba

113Cs

109I

105Sb

107Te 108Te

110Xe 111Xe 112Xe

104Sn

115Ba 116Ba

100Sn

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Z=50Excited statesFusion-evaporation

Decay propertiesFusion-evaporation

Decay propertiesExistenceFragmentation

CN

CN

CN

CN

CN

103InCN

CN

99Sn

95Cd

N=50

97In

93Ag

100Cd

101Ag

100Pd

β-delayed protonswith sizeable branchObserved/expected

101Sn prompt γ rays

(keV)γE50 100 150 200 250 300

Co

un

ts/2

keV

0

1

2

3

4

5

6172

(keV)γE50 100 150 200 250 300

Co

un

ts/2

keV

0

2

4

6

8

10

12

14

(keV)γE50 100 150 200 250 300

Co

un

ts/1

keV

1000

2000

3000

4000

5000

6000

7000310×

174

248

Total γ spectrum

101Ag

Random β

Ep=1-5 MeVtp<5s

γ rays

1 out of ~108 γ rays emitted!Ep=1.5-5 MeVT1/2=1.9(3)sbβp~15%σ=70 nb

101Sn

100Cd

γβp

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101Sn

γ

νg7/2

νd5/2

172 keV

N=51 isotones

5/2+ 5/2+5/2+ 5/2+

101Sn 99Cd 97Pd 95Ru 93Mo

7/2+

9/2+ 7/2+

9/2+

172

942

441

1363

7/2+

6867/2+

9/2+

9/2+

νg7/2

νd5/2

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FMA upgradespreparation for intense beams after energy and intensity upgrade

Beam dumpHigh-granularity DSSD

Digital GAMMASPHERE

GRETINA Digital electronicsX-array

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GRETINA at the FMA

Closer to FMAHigher rates

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AGFA – Argonne Gas Filled AnalyzerFMA little brother

Large efficiency, no mass resolution Optics by D. Potterveld

Target distance 40 cm – θx=55 mrad / θy=155 mradTarget distance 80 cm – θx~45 mrad / θy=100 mradsmall focal planeIn-beam and decay spectroscopy

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Possible experiments

Proton decay, 2p decaySuper-allowed alpha decay chain 108Xe-104Te-100SnExcited states in 100SnSecondary fusion-evaporation reactions with in-flight radioactive beamsZ>102 nuclei…

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I. AhmadB. BackM.P. CarpenterC.N. DavidsS. FischerC.L. JiangR.V.F. JanssensT.L. KhooF.G. KondevT. LauritsenC.J. ListerE. RehmJ. SchifferD. SeweryniakS. ZhuANLP.J. WoodsT. DavinsonUniversity of EdinburghW.B. WaltersUniversity of MarylandP. ChowdhuryLowell…

PostdocsD. AckermannD. BlumenthalS.J. FreemanA. HeinzD. HofmannG. MukherjeeV. NanalG.L. PoliP. ReiterA. RobinsonA. SonzogniI. StefanescuS. TandelJ. UusitaloI. WiedenhoeverCh. ChiaraL. McCutchanC. HoffmanA. Rogers…

StudentsG. HenningN. HotelingR.J. IrvineG. LotayH. MahmudP. MunroJ.J. ResslerJ. ShergurS. Siem…

Technical supportB. DiGiovineJ. FaloutJ. GreeneJ. JoswickD. HendersonB. NardiT. PenningtonB. SchumardJ. RohrerP. Wilt…

Without dedicatedATLAS crew

none of these experiments would be possible.

Thank you and Happy Anniversary!

Thank you for your attention!

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