Inverse-kinematic studies with Gretina and Phoswich Wall

1. 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 1 1

2. Some one-neutron transfer studies near 132Sn 134Te + 13C, Elab = 565 MeV, I= 3·105 s-1 (Holifield)Channel of interest: 135Te83CLARION + Hyball detector combination γPLF− particleTLF coincidences gate 929 gate 1180 gate 533 (narrow) 136Xe + 13C, Elab = 560 MeV (ATLAS)Channel of interest: 137Xe83Gammasphere + Microball gate 1220 Allmond et al., PRC 86 (2012); Radford et al., EPJA 15 (2002) [principle of experiment] 2 2

3. Next: 139Xe85 − level confirmation and spectroscopic factor No theory yet, but this argument can be made: The N = 83, 85 nuclei are cases for the emergence of collectivity just above 132Sn. A phenomenological model (coupling i13/2 states to quadrupole and octupole vibrations) was used. The lowest 13/2+ states ought to be rather pure (little admixture of 3−,f7/2). Hence S-factor data help to improve shell model calculations for 132Sn and neighboring nuclei. ? Heyde et al., PLB 57, 429 (1975) Data for Xe are, in general, sparse compared to heavier isotones. 3 3

4. Re-accelerated CARIBU beams, some nuclei of interest, and related parameters:single-particle transfer and both safe and unsafe Coulex Beam intensity in 105 s-1 (Cf252-upgrade-proposal-final-Rev4.pdf) Q values and energies in MeV Red: for 13/2+ in 139Xe,  = 17 mb (Ptolemy DWBA code) Large TLF angles = safe, small TLF angles = unsafe Coulex 4 4

5. B(E2;0+→21+) values in Sn region around N = 82 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 new measurement. “Standard” SM calculations aren’t able to reproduce small 136Te B(E2). 5

6. Acknowledgement Very valuable discussions with J.M. Allmond and D.C. Radford are gratefully acknowledged. Thanks for your attention! 6 6 6 6

7. 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). 7 7 7 7

8. Backup Slides

9. Franley et al., NPA 324, 193 (1979) 1p1/2 8 13C (cross sections to j> states are higher) 1p3/2 6 9Be (cross sections to j< states are higher) 1s1/2 2 9

10. 248Cm source experiment • 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.

11. Additional thoughts: 11B(140Xe,141Cs)10Be or 14N(140Xe,141Cs)13C , one-proton transfer 10Be - 9Be distinction: by ΔE (except at large θ), γ rays. Negative-parity states in the isotopic chain on both sides of the N = 82 “mark” πh11/2 Faller et al., PRC 38, 905 (1988) 11 11

12. Comment on Coulomb excitation 134,136Te + natC, Elab = 396 MeV, I= 105 s-1 (A=136) 12C-γ coincidences with CLARION + Hyball (Hyball rings 1 – 3; 4° ≤ θC ≤ 44°) 12

13. Some one-neutron transfer studies near 132Sn - continued TLF-γ angular correlations 134Te + 13C, CLARION + Hyball Use Hyball rings 3, 4: 28° ≤ θC ≤ 60° 12 detectors/ring, same set of angles ɸC For each event: reaction plane w/ angle ɸC Use the CLARION ring with θγ = 90° 5 detectors with different angles ɸγ Construct angular correlations: Δɸ= ɸγ −ɸC , 5 · 12 = 60 data points Allmond et al., PRC 86 (2012) 13

14. 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 orbitals A = 137 (N = 83): Isospin dependent modification of residual interaction A ≥ 139 (N ≥ 83): Shape evolution with N 13/2+: only one state not seen in SF. But the decay intensity is very different (compared to SF). 143Xe: levels seen in SF experiment. But no assignments made. Onset of collectivity. 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 14 14

15. 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? 15 15 15

16. Ordinate: Degree or MeV ε≈0.85 2π 16

17. 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. 17 17 17