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ANASEN - Array for Nuclear Astrophysics Studies with Exotic Nuclei

ANASEN - Array for Nuclear Astrophysics Studies with Exotic Nuclei. Jeff Blackmon (LSU), Grigory Rogachev (FSU), Ingo Wiedenhoever (FSU) and Ed Zganjar (LSU).

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ANASEN - Array for Nuclear Astrophysics Studies with Exotic Nuclei

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  1. ANASEN - Array for Nuclear Astrophysics Studies with Exotic Nuclei Jeff Blackmon (LSU), Grigory Rogachev (FSU), Ingo Wiedenhoever (FSU) and Ed Zganjar (LSU) Flexible, large-area charged-particle detector array targeting (,p) reactions, proton scattering, and transfer reactions using the ReA3facility at the NSCL and RESOLUT at FSU Active Target To improve understanding of light rare isotopes and (p,) and (,p) rates that are important in the p/rp processes Silicon-strip detector array backed with 2-cm-thick CsI Gas proportional counter for proton-tracking capability Supported by NSF MRI Program Here: 1) Nuclear Structure studies of light nuclei 2) Nuclear Astrophysics measurements

  2. ANASEN Annular silicon-strip array RIB 3 Rings of 12 Super-X3 silicon-strip detectors backed w/ 2cm thick CsI Anode wires of cylindrical gas proportional counter

  3. Silicon Strip Detectors X3 detectors constructed for ORRUBA by Micron Semiconductor 4 resistive strips (10mm X 75mm) S.D. Pain et al., NIMB261 (2007) 1122. 1 mm thick detectors x < 1 mm E < 100 keV “Super-X3” version 40x19 mm Ohmic segmentation First 12 detectors ordered Forward angle detectors currently under design 18cm outer diameter in 4 quadrants (6” Si) Minimal (~1mm) PC board on outer radius Pin out and mounting along radial direction 8cm ID design for use with PC Micron QQQ2 design Ep

  4. Proton-Resonant Scattering with ANASEN • Thick, active target allows simultaneous measurement of multiple resonances • Proton-depth tracking allows distinction between elastic and inelastic excitations Beam View p Beam slows downin target gas, scans over Resonanceenergies Same depth,different Ep ?

  5. Study of light exotic nuclei through resonance reactions with RNB’s RNB8, 2009 Structure of 8B http://cosmo.volya.net D. Morris & A. Volya P. Navratil et al., PRC 73, 065801 (2006)

  6. Study of light exotic nuclei through resonance reactions with RNB’s RNB8, 2009 Structure of 8B 7Be+p 3+ 2- Dominant configuration for the “missing” states is 7Be*(1/2-)+p. Should be observed in inelastic scattering. D. Halderson, PRC 69, 014609 (2004) G.V. Rogachev et al., Phys. Rev. C64 (2001) 061601(R)

  7. In-flight production of radioactive beams in inverse kinematics Combination of Superconducting RF-Resonator with high acceptance magnetic Spectrograph to create mass spectrometer RESOLUT: a new radioactive beam facility at John D. Fox Superconducting Accelerator Lab. at Florida State University Solenoid 1 Magnetic Spectrograph Target Position Solenoid 2 RF-Resonator RF-Resonator Magnetic Spectrograph Mass selectionslits Production target

  8. Study of light exotic nuclei through resonance reactions with RNB’s RNB8, 2009 Hybrid (thick/thin) target technique E1 E3 CH RESOLUT beam composition: 75% of 7Be, 25% of 7Li 2 p 7Be 7Li(p,n)7Be I7Be=2x105 pps 7Be • Target is thick enough for 7Be to lose significant fraction of it’s energy. • But thin enough for 7Be recoils to make it out of the target.

  9. Study of light exotic nuclei through resonance reactions with RNB’s RNB8, 2009 140o Excitation function of inelastic p+7Be scattering compared to R-matrix calculations with no new states in 8B. Elastic U. Greife, et al., NIM B 261 (2007) 1089 Inelastic Inelastic

  10. Study of light exotic nuclei through resonance reactions with RNB’s RNB8, 2009 7Be(p,p) 148o 7Be(p,p’)7Be* 146o Red curve is an R-matrix fit with the following resonances: 1+ - 0.77 MeV; known [1] 0+ - 1.8 MeV; new 3+ - 2.32 MeV; known [1] 2+ - 2.4 MeV; new 2- - 3.5 MeV; known [2,3] 1+ - ~3.5 MeV; new 7Be(p,p’)7Be* 138o 7Be(p,p) 140o 7Be(p,p) 132o 7Be(p,p’)7Be* 130o

  11. (,p) with ANASEN as active target • Example: 36 MeV 18Ne • 22 MeV 18Ne after window (4 MeVcm) • Elab~0.68 MeV/cm in 200 Torr • Ecm~120 keV/cm • Chamber filled with ~ 200-400 Torr He gas • Beam enters through ~ 2m Ti foil Top View Beam View p p +HV • Protons produced with energies from few ~20 MeV in extreme cases • 4He(18Ne,p): Ep~3-11 MeV • For 10 MeV protons, E ~ 5 keV in PC region  105 e • Resistive wire  good determination of position in PC

  12. (,p) - count rates, resolution, issues • Entire excitation function measured with 1 bombarding energy • Should be able to measure (a,p) cross section over a significant fraction of the Gamow window - though more difficult for heavier Z • Ecm can be reconstructed with good (<100 keVcm) resolution, but • More difficult for forward/backward angles • Dependent on emittance of beam • Thickness required of PC for accurate position reconstuction? • Leakage of charge from high ionization region of beam into PC

  13. Proton scattering and (p,) with ANASEN p-process Red = Most interesting cases • Our understanding of (p,) and (,p) reactions can be improved by studying nuclear structure via • proton elastic scattering • proton inelastic scattering • (p,) reactions

  14. Neutron-Detector Development: 6Li-Glass Sandwich 15 cm n p 25Al 25Al 26Si CD2 • (d,n) in inverse kinematics:Detect low-energy, 30-100 keV neutrons in “backward” directions γ-p branching ratios and angular distributions • Plan: use 6Li-glass scintillator-stack (5 cm depth=10% efficient.)

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