anasen - array for nuclear astrophysics studies with exotic nuclei
DESCRIPTION
ANASEN - Array for Nuclear Astrophysics Studies with Exotic Nuclei. Jeff Blackmon (LSU), Grigory Rogachev (FSU), Ingo Wiedenhoever (FSU) and Ed Zganjar (LSU). - PowerPoint PPT PresentationTRANSCRIPT
ANASEN - Array for Nuclear Astrophysics Studies with Exotic Nuclei
Silicon-strip detector array backed with 2-cm-thick CsIGas proportional counter for proton-tracking capabilitySupported by NSF MRI Program
Here: 1) Nuclear Structure studies of light nuclei 2) Nuclear Astrophysics measurements
To improve understanding of light rare isotopes and (p,) and (,p) rates that are important in the p/rp processes
Flexible, large-area charged-particle detector array targeting (,p) reactions, proton scattering, and transfer reactions using the ReA3 facility at the NSCL and RESOLUT at FSU Active Target
Jeff Blackmon (LSU), Grigory Rogachev (FSU),
Ingo Wiedenhoever (FSU) and Ed Zganjar (LSU)
ANASEN
3 Rings of 12 Super-X3 silicon-strip detectors backed w/ 2cm thick CsI
Annular silicon-strip array
RIB
Anode wires of cylindrical gas proportional counter
Silicon Strip Detectors
X3 detectors constructed for ORRUBA by Micron Semiconductor4 resistive strips (10mm X 75mm) S.D. Pain et al., NIMB261 (2007) 1122.
Ep
Forward angle detectors currently under design18cm outer diameter in 4 quadrants (6” Si)Minimal (~1mm) PC board on outer radiusPin out and mounting along radial direction8cm ID design for use with PC
x < 1 mmE < 100 keV
“Super-X3” version40x19 mm Ohmic segmentation
First 12 detectors ordered
1 mm thick detectors
MicronQQQ2 design
Proton-Resonant Scattering with ANASEN
Thick, active target allows simultaneous measurement of multiple resonances
Proton-depth tracking allows distinction between elastic and inelastic excitations
Same depth,different Ep ?
Beam slows downin target gas, scans over Resonanceenergies
p
Beam View
Structure of 8B
P. Navratil et al., PRC 73, 065801 (2006)
http://cosmo.volya.netD. Morris & A. Volya
Study of light exotic nuclei through resonance reactions with RNB’sRNB8, 2009
Structure of 8B
G.V. Rogachev et al., Phys. Rev. C64 (2001) 061601(R)
3+
2-
7Be+p
Dominant configuration for the “missing” states is 7Be*(1/2-)+p. Should be observed in inelastic scattering.D. Halderson, PRC 69, 014609 (2004)
Study of light exotic nuclei through resonance reactions with RNB’sRNB8, 2009
RF-Resonator
Magnetic Spectrograph
Target Position
RF-Resonator
Magnetic SpectrographSolenoid 2
Solenoid 1
Mass selectionslits Production
target
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
Hybrid (thick/thin) target technique
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.
7Be
p
7Be
CH2
E1 E3
RESOLUT beam composition: 75% of 7Be, 25% of 7Li
Study of light exotic nuclei through resonance reactions with RNB’sRNB8, 2009
7Li(p,n)7Be
I7Be=2x105 pps
Study of light exotic nuclei through resonance reactions with RNB’sRNB8, 2009
Excitation function of inelastic p+7Be scattering compared to R-matrix calculations with no new states in 8B.Elastic
Inelastic
Inelastic
140o
U. Greife, et al., NIM B 261 (2007) 1089
Study of light exotic nuclei through resonance reactions with RNB’sRNB8, 2009
7Be(p,p) 148o
7Be(p,p) 140o
7Be(p,p) 132o
7Be(p,p’)7Be* 146o
7Be(p,p’)7Be* 138o
7Be(p,p’)7Be* 130o
Red curve is an R-matrix fit with the following resonances:
1+ - 0.77 MeV; known [1]0+ - 1.8 MeV; new3+ - 2.32 MeV; known [1]2+ - 2.4 MeV; new2- - 3.5 MeV; known [2,3]1+ - ~3.5 MeV; new
(,p) with ANASEN as active target
Top View
+HV
p
p
Beam View
Chamber filled with ~ 200-400 Torr He gas Beam enters through ~ 2m Ti foil
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
Example: 36 MeV 18Ne22 MeV 18Ne after window (4 MeVcm)
Elab~0.68 MeV/cm in 200 Torr
Ecm~120 keV/cm
(,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
o More difficult for forward/backward angles
o Dependent on emittance of beam
o Thickness required of PC for accurate position reconstuction?
o Leakage of charge from high ionization region of beam into PC
Proton scattering and (p,) with ANASEN
Our understanding of (p,) and (,p) reactions can be improved by studying nuclear structure via• proton elastic scattering• proton inelastic scattering• (p,) reactions
p-process
Red = Most interesting cases
Neutron-Detector Development: 6Li-Glass Sandwich
(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.)
25Al p25Al
n
15 cm
26Si
CD2