Inverse-kinematic studies with Gretina and Phoswich Wall. Walter Reviol and Demetrios Sarantites (Washington University) Gretina Workshop, ANL, March 2013. Plastic-CsI(Tl) phoswich Angle range: 8º ≤ θ ≤ 74º 4 PMT’s, 64 pixels each Pixel size: 6 x 6 mm Sub-pixel positioning resolution. - PowerPoint PPT Presentation
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3/1/13 WR, DGS 111
Inverse-kinematic studies with Gretina and Phoswich WallInverse-kinematic studies with Gretina and Phoswich Wall
Walter Reviol and Demetrios Sarantites (Washington University)
Large TLF angles = safe, small TLF angles = unsafe Coulex
Red: for 13/2+ in 139Xe, = 17 mb (Ptolemy DWBA code)
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Symbols
Open: Raman et al., ADNDT 78 (2001)
Full: recent RIB Coulex experiments
Sn and Te: Radford et al. (Holifield)
Xe: Kröll et al. (REX-ISOLDE) AIP Conf. Proc. 1012, 84 (2008)
“N > 82 Anomaly” (Radford et al.)
Large error for 138Xe suggests newmeasurement.
“Standard” SM calculations aren’t able to reproduce small 136Te B(E2).
B(E2;0+→21+) values in Sn region around N = 82
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Acknowledgement
Very valuable discussions with J.M. Allmond and
D.C. Radford are gratefully acknowledged.
Thanks for your attention!
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Summary
The Phoswich Wall is, in a sense, the successor for Microball/Hyball. The experiments discussed are logic continuations of the inverse-kinematic radioactive-beam experiments pioneered by the group at ORNL-HRIBF.
The starter experiment would be neutron-transfer (and simultaneous Coulex) studies using a 138Xe beam from CARIBU and a 13C target. As for the transfer, the focus is on i13/2 physics.
For the very asymmetric “inverse” reactions the coverage, 8º ≤ θ ≤ 74º, of the Phoswich Wall can probably not be met by any other detector.
The Phoswich Wall will be keeping up with future high-intensity radioactive-beam experiments (and stable-beam experiments).
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Backup Slides
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1p1/2
1p3/2
1s1/22
6
8 13C
9Be
(cross sections to j> states are higher)
(cross sections to j< states are higher)
Fra
nle
y et
al.,
NP
A 3
24, 1
93 (
1979
)
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Observations• Assignment for 13/2+ (1512.2 keV) uses in part systematics.• Distinction between 13/2+ and 13/2-
(1085.8 keV) is not firm.
Issues• Populate preferably 13/2+.• Spin assignment by γ−particle angular correlations.• Fragmentation of i13/2 strength.
248Cm source experiment
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Faller et al.,PRC 38,905 (1988)
11B(140Xe,141Cs)10Be or 14N(140Xe,141Cs)13C , one-proton transfer
πh11/2Negative-parity statesin the isotopic chainon both sides of theN = 82 “mark”
Additional thoughts:
10Be - 9Be distinction: by ΔE (except at large θ), γ rays.
High-l states are strongly populated in inverse-kinematics reactions w/ C or Be targets. Let’s focus on the i13/2 and f7/2 orbitalsA = 137 (N = 83): Isospin dependent modification of residual interactionA ≥ 139 (N ≥ 83): Shape evolution with N
A focus in studies of A ≥ 139 Xe’s is the angular distribution of candidate 13/2 →11/2 transitions and, perhaps, their linear polarization
13/2+: only one state not seen inSF. But the decay intensity isvery different (compared to SF).
143Xe: levels seen inSF experiment. But no assignments made.
Onset of collectivity.
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What can be determined and how?
• For every excited state of the PLF, the Q value is obtained from the level energy and the calculated Qgg value (Q = Qgg – Elev).
• From θTLF,Lab , we then calculate θPLF,CoM (since we are dealing with a
binary reaction).
• If only PLF is excited, θPLF,CoM (θTLF,Lab) and ETLF,Lab(θTLF,Lab) are single
curves (if TLF is excited too, two curves are obtained, and the one
corresponding to the lower EPLF,CoM is picked).
What angle ranges can be covered?
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Ordinate:Degree or MeV
ε ≈ 0.85 2π
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Design requirements for the Phoswich Wall
The main application is in reverse-kinematics binary reactions.
An example: 13C(140Xe,141Xe)12C (CARIBU).
Details:• The observables are TLF particles and coincident PLF γ rays (12C − 141Xe γγ).
• The important derived quantity is dσ/dΩPLF,CoM(θ) → spectroscopic factors/ANC’s.
• Δθ ~ 1º and Δφ(θ) = 4º to 1º.
• Microball/Hyball segmentation (Δθ = 18º on average) is inadequate.
• High rate capability due to high “pixilation”.
• Z-identification of TLF’s, hence use phoswich detectors.
• No 4π coverage (e.g. 12C θgraz,lab = 40.3° for 465 MeV 140Xe + 13C).
• Optimal Doppler correction of PLF γ rays comes for free.