ORRUBA Gammasphere

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ORRUBA Gammasphere
Steven D. Pain University of the West of Scotland

• Motivation (mine)
• Experimental considerations

ATLAS User Workshop, ANL, August 2009
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ORRUBA and Gammasphere
Different (e.g. noble gas) beams at CARIBU
ORRUBA
CHICO chamber
Gammasphere 10 efficiency _at_ 1.33 MeV
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ORRUBA Gammasphere CARIBU Beams
Different (e.g. noble gas) beams at CARIBU Higher
energy range (10 MeV/A)
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Oak Ridge Rutgers University Barrel Array

• ORRUBA gives 80 f coverage over the range 45
  ?135

• 2 rings q lt 90 12 telescopes (1000mm R
  65mm NR)
• q gt 90 12 detectors (500mm R)
• 324 channels total (288 front side, 36 back side)

• HI beam
• Deuterated plastic targets

(C,C)
(d,d)
(d,p)
(p,p)
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ORRUBA Particle Identification
Single strip
deuterons
protons
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Low Level Density - 132Sn(d,p)133Sn
Fitting to known energy levels for the g.s., p3/2
and f5/2 gives an energy of 1305 keV 86 keV
for the (presumed) p1/2 state.
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132Sn(d,p)133Sn
Fitting to known energy levels for the g.s., p3/2
and f5/2 gives an energy of 1305 keV 86 keV
for the (presumed) p1/2 state.
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Higher Level Density - 134Te(d,p)135Te
ORRUBA standalones
ORRUBA telescopes
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Higher Level Density - 134Te(d,p)135Te
PRELIMINARY
1 MeV (p1/2)
0.66 MeV (p3/2)
1.8 MeV (f5/2 ?)
g.s. (f7/2)
Counts
Shell model calculations (Covello et al.) predict
significant fragmentation
Q value (MeV)
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N83 Systematics
135Te Tentative spin assignments from b-decay
measurement Hoff et al., Z. Phys. A 332 (1989)
407
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130Sn(d,p)131Sn
PRELIMINARY
4679(41) 4018(28) 3417(23) 2680(23)
131Sn (keV)
Energies from 4-6 detectors Calibrations
2H(132Sn,p)133Sn 2H(130Te,p)131Te Statistical
errors in ( ). Systematic error lt50 keV
Counts
(g.s.)
Q (keV)
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More precise determination of level energies
131Sn levels previously unknown No g.s.
population (Similar case for 133Te
states) Absolute energies difficult (systematic
uncertainties) 130Sn(9Be,8Be)131Sn reaction
using CLARION HyBall ( i13/2 state)
Measuring (d,pg) simultaneously addresses these
issues
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Complimentary Devices
Improved resolution with g rays Additional
information (eg g-g) Stronger beams (gt105 pps)
Improved particle resolution (especially for
lighter beams) High efficiency Weak beams (esp.
early CARIBU)
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TIARA Setup
Barrel Si 36? lt ?lab lt 144 ?
Target Changing Mechanism
Beam
VAMOS
Target position
Forward Annular Si (S1S2) 5.6? lt ?lab lt 28 ?
Backward Annular Si 144? lt ?lab lt 168.5 ?
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TIARA Performance 24Ne(d,p)25Ne
2x105 pps 24Ne 1 mg/cm2 CD2 target 2mm beam spot
size
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TIARA Performance
Due to hardware issue, actual efficiency was only
10 of this ie 1.5 _at_ 1.33 MeV
g
p
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TIARA Performance
Only core signals from EXOGAM clovers, limiting
Doppler correction to 65 keV broadening
g
p
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TIARA Performance
Only core signals from EXOGAM clovers, limiting
Doppler correction to 65keV broadening
g
p
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ORRUBA Gammasphere
105 pps on 200mg/cm2 CD2 for 1 week ? 2000
counts/state (singles) (200 proton-g
coincidences)
Improved particle resolution compared to TIARA
larger barrel, thinner targets
Recoil tagging, if necessary FMA (degraded
energy) Heavy recoils in lt 1 degree cone
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Calculation of 132Sn(d,p) _at_ 10 MeV/A
ORRUBA
End Cap
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Simulation of 132Sn(d,p) _at_ 10 MeV/A ORRUBA
response
CoM resolution 185 keV FWHM
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Gamma-ray efficiency and resolution
-2 rings, 0 cm/ns 41 Geo 9.7 Total
-2 rings, 4.13 cm/ns 41 Geometric 40 Geometric
(Lorentz-boosted) 9.4 Total
(Lorentz-boosted)
25 keV for 1 MeV _at_ 90
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ORRUBA Gammasphere chamber concept
214mm
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145mm
175mm
Feed-throughs
BGO
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Possible reactions
Calculated maximum beam intensities for a 1 Ci
252Cf fission source using expected efficiencies.
Isotope Half-life (s) Low-Energy Beam Yield (s-1) Accelerated Beam Yield (s-1)
104Zr 1.2 6.0x105 2.1x104
143Ba 14.3 1.2x107 4.3x105
145Ba 4.0 5.5x106 2.0x105
130Sn 222 9.8x105 3.6x104
132Sn 40 3.7x105 1.4x104
138Xe 846 9.8x106 7.2x105
110Mo 2.8 6.2x104 2.3x103
111Mo 0.5 3.3x103 1.2x102
Potential factor of 20 increase in beams (x10
from ATLAS upgrade up to 2 Ci source)
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(d,pg) as statistical neutron-capture surrogate
Proton kinematic curves
6 keV (FWHM)
Doppler-corrected ?-rays

• Neutron capture cant be done in regular
• kinematics for radioactive nuclei.
• Need branching ratio to gamma versus proton above
  separation energy (compound nucleus).
• Tight geometry leads to good statistics.
• Proton singles data has a lot of carbon fusion
  with proton evaporation.
• Current goals aim to eliminate carbon
  contamination and explore analysis options for
  even-even nuclei.

August 8, 2009
ANL
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Summary

• Complimentary device to HELIOS
• Push transfer experiments to nuclei with higher
  level densities
• Improve on excitation energy measurements
  (particularly for nuclei where single-particle
  states not previously observed)
• Tool for using surrogate methods for informing
  statistical (n,g) cross sections
• Comparatively minor cost (chamber, mount, preamp
  boxes)
• Experiments feasible with beams of 105 pps
• Other uses? (an invitation to collaboration)
• Name? (Gammasphere Orruba Detector)

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Motivation

• single particle energies constitute an important
  constraint on shell model calculations

r-process abundances (elemental, but also
isotopic)
Shell quenching in heavy nuclei
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The r-process
A
Chiba et al, PRC 77, 015809 (2008)
The r-process is made up mostly of reactions on
unstable neutron-rich nuclei (unmeasured) Extreme
conditions lead to (n,?)(?,n) equilibrium and
b-decay Large excursions at shell
closures Structure important during
freeze-out Rely on nuclear models - Study
single-neutron structure using neutron transfer
reactions (yields Ex, l, spectroscopic
information)
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r-process sensitivity
b decay
(n,g) (g,n)
n-capture b decay
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r-process sensitivity
J. Beun, et al. arXiv 0806.3895vq nucl-th
130Sn Rate x 10
132Sn Rate x 10

1. 140 180

1. 140 180

A
A

• Simulations show huge global sensitivity to the
  130Sn(n,?) rate, in contrast to the 132Sn(n,?)
  rate
• Why?
• Long b-decay lifetime
• High neutron separation energy (in 131Sn)

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r-process sensitivity
R. Surman, et al. Phys. Rev. C 79 (2009) 045809
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Astrophysical Nucleosynthesis
charged particle induced reactions e.g. (p,g) ,
(p,a) (a,g)

• Probe single particle states with the (d,p)
  reaction
• Preferentially selects low angular momentum
  states

neutron induced reactions e.g. (n,g)
A1
A1
A
A
Indirect reaction
Direct reaction
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Requirements of ORRUBA
Proton Energy-Angle Systematics
132Sn(d,p) _at_ 4.5 MeV/A

• High Solid Angular Coverage

• Good energy and angular resolution

• Large dynamic range

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ORRUBA Detector Design
8 strip non-resistive detectors
4 strip resistive detectors
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Experimental Setup for (d,p) Measurements
75-100mg/cm2 CD2 target (45-60 deg)
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132Sn(d,p)133Sn
(11/2-)
3700
(d,p) to ground state
(5/2-)
2004.6
(1/2-)
1655.7
1560.9
(9/2-)
853.7
(3/2-)
(7/2-)
0.0 1.45s
(d,p) to 2 MeV state
(d,p) to 1st ex state
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132Sn(d,p)133Sn
Fitting to known energy levels for the g.s., p3/2
and f5/2 gives an energy of 1305 keV 86 keV
for the (presumed) p1/2 state.
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Transfer measurements around 132Sn
Double shell closure Z50, N82
132Sn(d,p)133Sn, 130Sn(d,p)131Sn and
134Te(d,p)135Te measurements completed
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130Sn(d,p)131Sn
PRELIMINARY
133Sn Ex (keV) J? 2005 (5/2-) 1390
(1/2-) 854 (3/2-) 0
(7/2-)
130Snn (5247 keV)
132Snn (2417 keV)
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130Sn Rate x 10
132Sn Rate x 10
(1/2,3/2)
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131Sn Ex (MeV)


3
2
Strongest in (d,p)

1. 140 180

1. 140 180

(5/2)
A
A
If 1/2- and 3/2- assignments hold, could have
significant impact on DC calculations
1
(1/2)
(11/2-)
0
(3/2)
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Transfer measurements around 132Sn
Double shell closure Z50, N82
132Sn(d,p)133Sn, 130Sn(d,p)131Sn and
134Te(d,p)135Te measurements completed
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134Te(d,p) Motivation
Pre-solar diamond grains

• Overabundance of light and heavy Xe isotopes
• Heavy isotope anomaly relative excesses of
  134Xe and 136Xe do not correspond to average
  r-process abundances

U. Ott, Planetary and Space Science 49 (2001) 763

• Suggested explanations
• Formation in intermediate neutron flux
  environment (between s r process)
• Rapid separation of Xe from its precursors (Te
  and I) in supernova ejecta
• Low entropy r-process

Effect of structure around N82 shell closure
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N83 Systematics
Preliminary evidence for observation of p1/2
state in better agreement with systematics
f5/2 state does not fit with systematics
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Future measurements

• Measured
• 132Sn(d,p)133Sn
• 130Sn(d,p)131Sn
• 134Te(d,p)135Te

• Approved
• 126Sn(d,p)127Sn
• 128Sn(d,p)129Sn
• 132Te(d,p)133Te
• 132Sn(d,t)131Sn

124Sn
130Te
131Sn
135Te
Te
Sb
Z 50
Sn
In
Stable
Doubly magic
N 82
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(No Transcript)
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Collaborators
J.A. Cizewski, R. Hatarik, P.D. OMalley, M.
Sikora Rutgers University M.S. Johnson, C.
Matei Oak Ridge Associated Universities D.W.
Bardayan, J.C. Blackmon, C.D. Nesaraja, M.S.
Smith, D. Shapira, F. Liang Oak Ridge National
Laboratory R.L. Kozub, J.F. Shriner,
S.Paulauskas, J.Howard, D.Sissom Tennessee Tech.
University K.A. Chipps, J. James, R.J.
Livesay Colorado School of Mines K.Y. Chae, K.L.
Jones, R. Kapler, B.H. Moazen University of
Tennessee W.N. Catford, C. Harlin, N. Patterson,
T.P. Swan, J.S. Thomas, G.L. Wilson University of
Surrey
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Expected Levels Populated in (d,p)
Should be strongest in (d,p) (?1 and ?3)
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134Te(d,p) Data Q-value spectrum
PRELIMINARY
CoM resolution 250keV (FWHM)
Single strip
See talk by J.A. Cizewski (Friday 945) for more
details
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r-process nucleosynthesis
N126
N82
N50
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ORRUBA Gammasphere for transfer reactions
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ORRUBA Gammasphere for transfer reactions
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ORRUBA Gammasphere for transfer reactions
Full, 0 cm/ns 45 Geo 45 Boosted 10.6 Total
Boosted
-1 ring, 0 cm/ns 43 Geo 43 Boosted 10.2 Total
Boosted
-2 rings, 0 cm/ns 41 Geo 41 Boosted 9.7 Total
Boosted
-2 rings, 4.13 cm/ns 41 Geo 40 Boosted 9.4
Total Boosted
-1 ring, 4.13 cm/ns 43 Geo 42 Boosted 10.0
Total Boosted
Full, 4.13 cm/ns 45 Geo 45 Boosted 10.6 Total
Boosted
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ORRUBA Gammasphere for transfer reactions
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ORRUBA Gammasphere for transfer reactions