  (α,p) rates are very important for X-ray bursts:
• Burst light curve
• Ash composition
X-ray flux (cts/s)
(α,p) measurements at FRIB
6000
4000
2000
0
500
600
at ReA3
R. Cyburt, K. Smith et al., in prep.
700
800
Time (s)
900
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
(α,p) reactions, proton scattering, and transfer reactions using
the ReA3 facility at the NSCL and RESOLUT at FSU
To improve understanding of light rare isotopes and (p,γ)
and (α,p) rates that are important in the αp/rp processes
Silicon-strip detector array backed with 2-cm-thick CsI
Gas proportional counter for proton-tracking capability
Supported by NSF MRI Program
5 Letters of Intent submitted to NSCL PAC33 (positive)
We welcome new ideas, suggestions, collaborations …
ANASEN
RIB
3 Rings of 12 Super-X3
silicon-strip detectors
backed w/ 2cm thick CsI
Annular silicon-strip array
Anode wires of
cylindrical gas
proportional counter
What is possible at ReA3?
 We will only be able to measure (α,p) cross section over the top half of the
Gamow window with ReA3 intensities.
 Measurement of (α,p) cross sections at low energies is very important part
of the scientific program at FRIB.
 Is ANASEN sufficient?
 Is use of window problematic (straggling in window and gas)?
 Better to use lower pressures
 Higher stopping powers – range is very compressed
 Problem for gas counter (lower signal size)?
 Need to gain operational experience – explore windowless option
Proton scattering and (p,α) with ANASEN
αp-process
Red = Most interesting cases
  Our understanding of (p,γ) and (α,p) reactions can be improved
by studying nuclear structure via
•  proton elastic scattering
•  proton inelastic scattering
•  (p,α) reactions
Measurements with Tz=+1/2 beams
Reaction
18
Ne( ,p)21Na
22
Mg( ,p)25Al
26
Si( ,p)29P
30
S( ,p)33Cl
34
Ar( ,p)37K
Compound
nucleus
22
Mg
26
Si
30
S
34
Ar
38
Ca
Q [MeV]
8.141
9.173
9.343
6.740
6.106
Following
reaction
21
Na(p, )22Mg
25
Al(p, )26Si
29
P(p, )30S
33
Cl(p, )34Ar
37
K(p, )38Ca
Qp [MeV]
5.5018
5.5178
4.399
4.6628
4.548
Beam
21
Na
Al
29
P
33
Cl
37
K
25
Yield
[pps]
1e5
2e5
4e5
4e5
4e5
  Measure proton elastic, inelastic and (p,α) reactions
  Measurements at θlab<45°
•  Higher energy protons
33Cl(p,p)
  Annular detector array preferred
•  Efficiency > 90%
•  Good θ resolution with low channel count
  33Cl+p
•  Only 2 candidate resonances within 2 MeV of the
proton threshold in 34Ar
•  Mirrors to 34S states unknown
33Cl(p,α)30S
Ebeam
(MeV)
208
192
175
157
33
Ecm (p+ Cl)
(MeV)
5.9
5.4
4.9
4.4
Count rate estimate
Ecm ( +30S)
(MeV)
3.8
3.3
2.8
2.3
< >
( b)
~100
~40
~6
~0.3
Count rate
(events/day)
~300
~100
~15
<1
# days
1
2
4
-
Jπ=1+
Sp=0.1
Ex=6.0