Deep inelastic and multinucleon reactions with discrete gamma ray spectroscopy a brief review
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Paddy Regan Dept. of Physics University of Surrey, UK E-mail: p.regan@surrey.ac.uk PowerPoint PPT Presentation


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Deep-Inelastic and Multinucleon Reactions with Discrete Gamma - ray Spectroscopy: A Brief Review. Paddy Regan Dept. of Physics University of Surrey, UK E-mail: p.regan@surrey.ac.uk. Physics of neutron-rich nuclei is the evolution of shell structure related

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Deep-Inelastic and Multinucleon Reactions with Discrete Gamma-ray Spectroscopy: A Brief Review

Paddy Regan

Dept. of Physics

University of Surrey, UK

E-mail: p.regan@surrey.ac.uk


  • Physics of neutron-rich nuclei is the evolution of shell structure related

  • to large energy gaps in the nuclear single-particle spectrum.

  • Reasons to study neutron-rich nuclei include:

  • Evolution of collective modes (vibrations, rotations, superdef ?)

  • from spherical states by altering position in (N, Z, Ip, Ex) space.

  • Identification of specific orbitals, e.g. via isomers; g-factors;

  • B(E2:I->I-2); shell model, seniority, Nilsson schemes etc.

  • 3) Identifying new nuclear ‘exotica’, e.g., b-/proton/a-decaying states;

  • new symmetries (e.g., a32), shell closures, shape changes..etc.


  • (Some) DIC basics.

    • Thick or thin targets ? (Ip , Ex,N, Z) ; isomer gating etc.

  • Thin target multi-nucleon transfer reactions:

    • Neutron-rich C nuclei (Berlin BRS).

    • N~20, Island of Inversion.

    • N=32,34 (sub)-shell closures, Se (Z=34, N=50).

    • 48Ca magic number(s).

    • N=50 robustness and shell closure.

    • Rotation/vibration evolution in A~100.

    • 132Sn region

      • Seniority Ip=10+ isomers, h11/2 neutron hole migration ?

      • Surface diffuseness, weakening of N=82 shell ?

    • A~170-190 K-isomerism and nuclear shape symmetry.

    • 208Pb at high spins; octupole collective vibrations etc.

    • U, Th octupole states, (very) high-j intruders (k17/2 etc.)

    • DIC with RIBs (24Ne beam at GANIL)

    • TIARA (d,p) etc. in inverse kinematics….


Courtesy,

Bogdan

Fornal


Courtesy,

Bogdan

Fornal


R.Broda et al., Phys. Rev. C49 (1994)


208Pb

64Ni

W. Krolas et al., Nucl. Phys. A724,289 (2003).


Advantages and limitations of g-ray thick target measurements with DIC

LIMITATIONS

Gamma spectra very complicated

(hundreds of sources)

Gamma rays from the short lived

states smeared out by the Doppler

effect (emitted before a product is stopped)

Difficulties of identifications without

a starting point.

Angular distribution of g rays almost isotropic

ADVANTAGES

Gamma rays from all reaction products

Gamma rays from the stopped nuclei –

narrow lines – easy analysis ofg-g

coincidences

Detection of cross-coincidences – some

potential for identification


Deep-inelastic reactions

For K-Isomers with

238U beams

3.5 MeV, >3 ms, 16+

186W

  • 238U at 1600 MeV

  • 186W (16 mg cm-2)

  • μs →ms beam pulsing

  • Argonne/Notre-Dame

  • array of 12 Ge dets.

1.5 MeV, 18 μs, 7–

Off-beam singles, 7h

Out-of-beam condition

yields only lines from

the new isomers.

Total singles, 15 min.

Without an off-beam

timing condition, only

Coulomb excitation

lines are seen.

Courtesy, Carl Wheldon


z

x

q1

q2

f1

f2

y


Ge

TLF

beam

qtlf,ftlf

qblf,fblf

BLF

M . Simon et al., Nucl. Inst. Meth. A452, 205 (2000)

Rochester Group

TOF ~5-10 ns.

ns-ms isomers can

de-excite in be

stopped byCHICO

position detector. Delayed

gs can still be viewed

by GAMMASPHERE.


100Mo + 136Xe @ 700 MeV GAMMASPHERE + CHICO

PHR, A.D. Yamamoto et al., AIP Conf. Proc. 701 (2004) p329


PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313

Can see clearly to spins of 20ħ using thin-target technique.


nano to microsecond isomer tagging ?


Isomer gating very useful in DIC experiments.

PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313


A.D.Yamamoto,

Surrey PhD thesis (2004)

Wilczynski (‘Q-value loss) Plot


Can we use the data from the CHICO+Gammasphere expt.

to understand the ‘DIC’ reaction mechanism ?

A wide range of spins & nuclei are observed.


What about the spin input ?


R. Bock et al.,

Nukleonika

22 (1977) 529


Fold distributions highlight different reaction mechanisms

+2p

-2n

+2n

PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313


BLFs

TLFs

elastics

PHR, A.D.Yamamoto et al., Phys. Rev. C68 (2003) 044313


Emission angle of TLFs can give information/selection

on reaction mechanism (and spin input).


198Pt +136Xe, 850 MeV

J.J. Valiente-Dobon, PHR,

C.Wheldon et al., Phys. Rev.

C69 (2004) 024316


Temporal separation can clearly identify ‘prompts’ and isomer decays

136Xe + 198Pt

J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316


J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316

67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85

84

83

82

81

80

79

78

77

nano and microsecond isomers

on gated 198Pt+136Xe with

GAMMASPHERE+CHICO

DIC

110 111 112 113 114 115 116 117 118 119 120 121 122 123 124

76

75

74

73

59

58

57

56

55

54

53

52

51

50

N/Z compound


J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313

136Xe+198Pt Target-like fragment isomers

184W

195Os

192Pt

185Re

191Os

198Pt

193Au

192Os


g-g information and lifetime determination of 195Os isomer decay


Dobon, Wheldon, Regan et al.,

New isomer in 195Os identified in GSI projectile fragmentation

confirmed ‘in-beam’ CHICO+GAMMASPHERE g-g data.

M.Caamano, P.M.Walker, PHR et al., Eur. Phys. J. A (2005)


136Xe+198Pt reaction beam-like fragment isomers.

132Xe

128Te

130Te

136Xe

138Ba

131I

137La

133I

J.J.Valiente-Dobon, PHR, C.Wheldon et al., PRC69 (2004) 024313


J.J. Valiente-Dobon, PHR, C.Wheldon et al., Phys. Rev. C69 (2004) 024316

10+

N=80

isotone


N=80 isotonic chain, 10+ isomers, (nh11/2)-2I=10+

Q. Why does Ex(10+) increase while

E(2+) decreases ?

91(2) ns


Energy of N=80

Ip=10+ isomers

correlates with

energy increase

of 11/2- single

neutron hole in

N=81 isotones.

Increase in 10+

energy, plus

expansion of

proton valence

space means

8+ yrast state

now (mostly)

NOT (nh11/2)-2

for Z>54

Ex, Ip=11/2 -

N=81

Ex, Ip=10

N=80

Valiente-Dobon, PHR, Wheldon et al., PR C69 (2004) 024313


Pair Truncated Shell Model

Calculations (by Yoshinaga,

Higashiyama et al. Saitama)

predict yrast 8+ in 136Ba

no longer mostly (nh11/2)-2

but rather, (pd5/2)2(pg7/2)2


BRS+EUROBALL

  • 18O at 90 MeV on 9Be (98 μg.cm-2)

  • BRS: q = ±12.5° → ±45.5°

  • Euroball: 15 clusters, 26 clovers (209 crystals)

  • Unique-Z id., position to 1 mm, energy of recoil

  • Particle-γ, particle-γ-γ and particle-particle-γ-γ

  • coincidences

Doppler correction from energy in BRS

Add-back included

Z

Carbon gate

Energy

Courtesy, Tzany Kokolova


CLARA

S. Lunardi, Acta. Phys. Pol. B36 (2005) 1301


S. Lunardi, Acta. Phys. Pol. B36 (2005) 1301

A. Gadea et al., J. Phys. G (2005) in press


S. Lunardi, Acta. Phys. Pol.

B36 (2005) 1301


Mg

Na

Ne

24Ne

F

O

N

C

B

Be

Li

He

H

Report of the E421S experiment (spokeperson F.Azaiez):

aim of the experiment

DIC with RIBs!

A new era ?

Deep Inelastic Collision reaction with light exotic beam

Population of exotic Ne-F-O isotopes

  • cross section measurements

  • g spectroscopy Ne-O-F

courtesy, Giovanna Benzoni


Report of the E421S experiment:

Experimental details

  • reaction: 24Ne @ 7.923 MeV/A + 208Pb (10.9 mg/cm2)

  • 24Ne5+ , Ibeam ~ 1.5 . 105 pps

  • beam on target for 7 days

  • setup: Vamos + EXOGAM

  • Vamos @ 45°

  • EXOGAM 11 detectors

  • (2 without Compton shield)

  • Typical count rates:

  • Ions: 30/min  Total Ion counts: 7*24*60*30 = 302400

  •  cross section determination is feasible

  • Ion-gamma coincidence 70/h

    • Total Ion-gamma coinc. 7*24*70 = 11760

      • only spectroscopy of inelastic ch.

courtesy, Giovanna Benzoni


ID-plot

E

E (a.u.)

F

Ne

O

Na

DE (a.u)

Report of the E421S experiment:

very preliminary spectra

3 days of statistics (~ 1/2)

Working on mass separation

courtesy,

Giovanna Benzoni

Analysis in progress

  • Conditions:

  • Si-gamma coincidence

  • Prompt gamma peaks

  • calculated v/c

Ne (inelastic)


23F ~ 20 mb

(1p removal)

24Ne ~ 500 mb

26Ne ~ 80 mb

(2n pick up)

F

Ne

Beam intensity required to study weaker channels

  • to get to more exotic Ne isotopes  ~ 106

  • to get to F  5.106

  • to get to O  ~ 107

Report of the E421S experiment:

future

courtesy,

Giovanna Benzoni


TIARA

courtesy, Wilton Catford


TIARA

Experimental Results for 24Ne(d,p)25Ne Transfer with TIARA

10 MeV/u

(d,p)

25Ne

Courtesy, Wilton Catford


  • DIC physics….

    • Neutron-rich C nuclei (Berlin BRS).

    • N~20, Island of Inversion.

    • N=32,34 (sub)-shell closures, Se (Z=34, N=50).

    • 48Ca magic number(s).

    • N=50 robustness and shell closure.

    • Rotation/vibration evolution in A~100.

    • 132Sn region

      • Seniority Ip=10+ isomers, h11/2 neutron hole migration ?

      • Surface diffuseness, weakening of N=82 shell ?

    • A~170-190 K-isomerism and nuclear shape symmetry.

    • 208Pb at high spins; octupole collective vibrations etc.

    • U, Th octupole states, (very) high-j intruders (k17/2 etc.)

    • DIC with RIBs (24Ne beam at GANIL)

    • TIARA (d,p) etc. in inverse kinematics….


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