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The Phoswich Wall – features, applications, performance

The Phoswich Wall – features, applications, performance. Walter Reviol and Demetrios Sarantites (Washington University) ATLAS User Workshop, ANL, May 2014. Plastic – CsI(Tl) phoswich Angle range: 9º ≤ θ ≤ 72º 4 PMT’s, 64 pixels each Sub-pixel positioning resolution: Δ x ≈ 1 mm

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The Phoswich Wall – features, applications, performance

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  1. The Phoswich Wall – features, applications, performance Walter Reviol and Demetrios Sarantites (Washington University) ATLAS User Workshop, ANL, May 2014 Plastic – CsI(Tl) phoswich Angle range: 9º ≤ θ≤ 72º 4 PMT’s, 64 pixels each Sub-pixel positioning resolution: Δx ≈ 1 mm Tailored to run with a 4πγ-ray array Coincidence measurement: particleTLF – γPLF 5/15/14 WR 5/15/14 WR 5/15/14 WR 5/15/14 WR 1 1 1 1 1 1

  2. Some one-neutron transfer studies near 132Sn 134Te + 13C, Elab = 565 MeV, I= 3·105 s-1 (Holifield)Channel of interest: 135Te83Hyball + CLARION detector combination particleTLF −γPLF coincidences gate 929 gate 1180 gate 533 (narrow) 136Xe + 13C, Elab = 560 MeV (ATLAS)Channel of interest: 137Xe83Microball + Gammasphere gate 1220 Allmond et al., PRC 86 (2012); Radford et al., EPJA 15 (2002) [principle of experiment] 5/15/14 WR 5/15/14 WR 2 2 2 2 2

  3. Transfer reaction vs. spontaneous fission Vast amount of information Selectivity (can dial state of interest) 248Cm SF Daly et al. PRC 59, 3066 (1999) 136Xe + 13C  137Xe + 12C Allmond et al., PRC 86, 031307(R) (2012) 137Xe 5/15/14 WR 3 3 3

  4. Lessons learned so far • Using comparatively heavy targets (13C, 9Be) is a good way of studying high-j, high-ℓ states; complementary to (d,p), (α,3He) • Combining HPGe array and Phoswich Wall (Microball) is beneficial for studying heavy nuclei; here the density of states is high • Using the selectivity of transfer reactions allows to improve level schemes previously studied via SF, fusion-evaporation, or deep-inelastic collisions; for example, the transition intensity helps to determine the state’s parity New tasks • Extract nucleon-transfer spectroscopic factors from dσ/dΩCoM,PLF; based on TLF angular-distribution data • Explore the potential of cluster transfer, e.g., 142Ce(7Li,α)145Pr; suppress incomplete-fusion channels, get a handle on 3H spectroscopic factors 5/15/14 WR 5/15/14 WR 5/15/14 WR 4 4 4 4 4 4

  5. 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 θLab,TLF , we then calculate ΘCoM,PLF(since we are dealing with a binary reaction). If only PLF is excited,ΘCoM,PLF(θTLF) and ELab,TLF(θLab,TLF) are single curves. (If TLF is excited too, two curves are obtained, and the one corresponding to the higher ELab,TLF is picked.) The derived quantity is dσ/dΩCoM,PLF (θLab,TLF). (What angle ranges can be covered?) 5/15/14 WR 5/15/14 WR 5/15/14 WR 5 5 5 5 5 5 5

  6. Example: study of one-proton transfer in heavy rare-earth nuclei Ground-state to ground-state Q value in MeV Nitride target CARIBU beam Red Case of interest: location of πh11/2 , occupancy of πg7/2 vs. N Experimental issue: separate C from N and O (20 MeV < ELab,TLF < 150 MeV) ~ ~ 5/15/14 WR 5/15/14 WR 5/15/14 WR 6 6 6 6 6 6

  7. Phoswich Wall in-beam performance (Notre Dame FN Tandem) Scattering experiments: • α’s, heavy ions off 197Au (5 – 6 energies) • 197Au(α,p)202Hg (27 MeV) • consider energy deposited in CsI(Tl) • gating A: Fast, B: Early, C: Late Findings: Ions are well separated down to low energies (14N: Edep= 8.46 MeV) Some may be mass-identifiable at higher energies (7Li vs. 6Li) 5/15/14 WR 5/15/14 WR 5/15/14 WR 7 7 7 7

  8. Phoswich Wall 252Cf tests: the position algorithm Used square masks of different sizes The algorithm is pulse-height independent Applying the algorithmgives uniform distributions 4.8 x 4.8 mm2 mask 5/15/14 WR 8 8 8

  9. Summary and Outlook The Phoswich Wall was designed for strongly inverse kinematics binary reactions near the Coulomb barrier. It is not a “stand-alone” device. The new device is, in a sense, the successor for Microball/Hyball. Starter experiments are: 7Li breakup/transfer and single-nucleon transfer studies, the latter with comparatively heavy targets. Projectile Coulomb excitation will be performed simultaneously, large angles θLab,TLF favor safe Coulex (not discussed). The PID among the particles of interest is as good as expected. The fast-plastic and CsI(Tl) components are calibrated. The device is ready for production runs. The readout is VME based and can be easily coupled to the Myriad system of DGS and to Gretina (not discussed). High-quality stable and CARIBU reaccelerated beams from ATLAS are crucial (timing, beam spot). 5/15/14 WR 5/15/14 WR 9 9 9 9 9 9 9

  10. Acknowledgement Very valuable discussions with J.M. Allmond and D.C. Radford are gratefully acknowledged. Thanks for your attention! 10 10 10 10 10

  11. Backup Slides 11

  12. Additional thoughts on studying odd-Z nuclei: 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) 5/15/14 WR 12 12 12 12

  13. no extra angular momentum (that would influence the phase of the distorted wave) 1, 2: initial, final bound state Franley & Phillips, NPA 324, 193 (1979) 1p1/2 8 14N cross sections to j> states are higher (like 16O) 1p3/2 6 11B cross sections to j< states are higher (like 12C) 1s1/2 2 5/15/14 WR 13 13 13 13 13 13

  14. Q-value considerations for studying odd-Z nuclei in the rare-earth region Q value in MeV Also considered as incomplete-fusion channel Odd-N nucleus, for comparsion only Red: suggested cases for a simultaneous study 5/15/14 WR 14 14 14 14

  15. 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°) 15 15

  16. Phoswich Wall Tilted “Gobbi” geometry Average target­­­-detector distance: 55 mm Angle range: 9º ≤ θ≤ 72º Multi-anode PMT (H8500): • # pixels: 64 • active fraction of surface: 0.89 • pixel size: 6.02 × 6.02 mm2 Phoswich: 12 μm fast plastic, 2.2 mm CsI(Tl) Optical cross talk: sub-pixel positioning Expect: Δθ ≈ 1° , Δφ(θ) ≈ 4°­ - 1° Microball: Δθ ≈ 18° 5/15/14 WR 5/15/14 WR 5/15/14 WR 5/15/14 WR 16 16 16 16 16 16

  17. Phoswich Wall 252Cf tests: particle identification (PID) gating Gates: Fast (A) , Early (B) , Late (C) Pixel neighbor pulse heights are added in ASIC chip readout (so-called PSD chip) Early (B) Late (C) (A) Early (B) 5/15/14 WR 17 17 17

  18. 142Ce + 14N → 137Xe + 13C, Elab= 560 MeV Good separation at the smaller angles ΔE* = 3.089 MeV (13C: 1/2+) ΔELab,TLF ≈ 5.5 MeV ε≈ 0.85 2π 5/15/14 WR 18

  19. 142Ce + 14N → 137Xe + 13C, Elab= 560 MeV ΔθLab ≈ 1° ↔ ΔθCoM ≈ 2° 5/15/14 WR 5/15/14 WR 19 19

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