studying the a p-process at atlas catherine m. deibel
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Studying the p-process at ATLAS
Catherine M. Deibel
Joint Institute for Nuclear Astrophysics
Michigan State University
Physics Division
Argonne National Laboratory
2
p-process in Explosive Stellar Environments
Supernovae– Type II: (,p) reactions during the -rich freeze out
• e.g. Radioactive 44Ti destruction and its influence on -ray surveys– Type Ia: due to He accreting CO white dwarfs
Classical novae – lower mass nucleosynthesis
X-ray bursts – Breakout of the CNO cycle– Beginning of the rp-process
3
p-process in X-Ray Bursts
The early rp-process a series of (p,), () and (,p) reactions
Stalls where (p,) and (,p) reactions come into equilibrium and must wait for + decay
(,p) reactions can break out if they are faster than the + decay
May be responsible for double-peaked luminosity profiles
Sensitivity studies have shown many of these reactions have significant effects on final abundances and energy output
4
p-process in X-Ray Bursts
The early rp-process a series of (p,), () and (,p) reactions
Stalls where (p,) and (,p) reactions come into equilibrium and must wait for + decay
(,p) reactions can break out if they are faster than the + decay
May be responsible for double-peaked luminosity profiles
Sensitivity studies have shown many of these reactions have significant effects on final abundances and energy output
5
p-process in X-Ray Bursts
The early rp-process a series of (p,), () and (,p) reactions
Stalls where (p,) and (,p) reactions come into equilibrium and must wait for + decay
(,p) reactions can break out if they are faster than the + decay
May be responsible for double-peaked luminosity profiles
Sensitivity studies have shown many of these reactions have significant effects on final abundances and energy output
6
p-process in X-Ray Bursts
The early rp-process a series of (p,), () and (,p) reactions
Stalls where (p,) and (,p) reactions come into equilibrium and must wait for + decay
(,p) reactions can break out if they are faster than the + decay
May be responsible for double-peaked luminosity profiles
Sensitivity studies have shown many of these reactions have significant effects on final abundances and energy output
7
p-process in X-Ray Bursts
The early rp-process a series of (p,), () and (,p) reactions
Stalls where (p,) and (,p) reactions come into equilibrium and must wait for + decay
(,p) reactions can break out if they are faster than the + decay
May be responsible for double-peaked luminosity profiles
Sensitivity studies have shown many of these reactions have significant effects on final abundances and energy output
8
Radioactive Beams: The In-Flight Method
Stable beam impinges on gas target and produces radioactive nuclei via (p,n), (d,n), (d,p), (p,d), (p,t), and (3He,n) reactions
Intensities of up to 3 x 106 particles/s achieved
Radioactive beams produced: 6He, 7Be, 8Li, 8B, 12B, 10C, 11C, 14O, 15O, 16N, 17F, 20,21Na, 25Al, 33Cl, and 37K (plans to produce heavier radioactive beams in the near future)
9
(,p) Studies in Inverse Kinematics with Short-lived Nuclei
Thick (extended) target method: 4He(14O,p)17F[C. Fu et al., Phys. Rev. C 76, 0216603 (2007)]
Thin (localized) 4He target with FMA: 4He(44Ti,47V)p[A.A. Sonzogni et al., Phys. Rev. Lett. 84, 1651 (2000)]
Time-inverse studies (e.g. CH2 target): p(33Cl,30S)4He[C.M. Deibel et al., in preparation (2009)]
10
Limitations of Previous (,p) Studies
Lack of radioactive beams or low intensity radioactive beams
Thick target method
– Acceptance
– Resolution of reaction products
– Identification of products from process of interest
Thin (localized) target method
– Small acceptance (≤ 2.5°)
– Particle identification of light recoils
Time-inverse reactions
– Separation of primary and secondary beams
– Particle identification in Si detectors
– Heavy recoil identification
11
12
PrototypeSi arraySi array
Recoil Detector
Target fan
Beam
HELIOSHELIcal Orbit Spectrometer
Consists of a target fan, Si strip detector array (to detect light recoils) and 0° detector (to detect heavier recoils) housed in a 3 T solenoid
Magnetic field allows unique particle identification based on particle’s cyclotron frequency:
Tc=2m/(qB)
Energy resolution in laboratory is equal to that of the center-of-mass system
13
11B(d,p)12B
12B(d,p)13B
11B(d,p)12B
12B(d,p)13B
“Conventional” HELIOS Preliminary
Improved Resolution of HELIOS
14
p-process studies with HELIOS
Target fan
Recoil detector
Prototype Si Array
Beam
Original design– Solid targets– Detection of backward light recoils– Detection of heavy recoils at 0°
15
p-process studies with HELIOS
Prototype Si Array
Gas target
Recoil detector
Original design– Solid targets– Detection of backward light recoils– Detection of heavy recoils at 0°
Additions:– Gas target: allows 3,4He targets
Beam
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HELIOS Gas Target
Gas targets currently used in the SplitPole Spectrograph and CPT areas
– LN2 cooled
– effective thickness of 80 g/cm2
Modified design will allow for use in HELIOS for– direct (,p) reaction studies– other indirect studies via transfer reactions
such as (3He,d), (3He,t), (4He, 3He), (4He,t), etc.
17
p-process studies with HELIOS
Prototype Si Array
Gas target
Recoil detector
Original design– Solid targets– Detection of backward light recoils– Detection of heavy recoils at 0°
Additions:– Gas target: allows 3,4He targets
Beam
18
p-process studies with HELIOS
Si Array
Gas target
Recoil detector
Original design– Solid targets– Detection of backward light recoils– Detection of heavy recoils at 0°
Additions:– Gas target: allows 3,4He targets– Full Si array allows almost 4
acceptance
Beam
19
4He(34Ar,p)37K gs
4He(34Ar,p)37K 3 MeV
p-process studies with HELIOS
Particle p 3He d,4He t
TOF(ns) 21.9 32.8 43.7 65.6
(deg)
Ep (
Me
V)
20
p-process studies with HELIOS
Si Array
Gas target
Recoil detector
Original design– Solid targets– Detection of backward light recoils– Detection of heavy recoils at 0°
Additions:– Gas target: allows 3,4He targets– Full Si array allows almost 4
acceptance
Beam
21
p-process studies with HELIOS
Si Array
Gas target
PPAC and IC
Original design– Solid targets– Detection of backward light recoils– Detection of heavy recoils at 0°
Additions:– Gas target: allows 3,4He targets– Full Si array allows almost 4
acceptance– PPAC and IC allows for more
robust particle identification of heavier recoils, beam, and beam contaminants
Beam
22
Conclusions
The (,p)-process has far ranging effects for XRBs and other sites of explosive nucleosynthesis
The production of new and heavier radioactive beams will enable new (,p) studies
HELIOS is already a powerful tool for reaction studies in inverse kinematics
With proposed upgrades it will be uniquely suited for direct (,p) studies by overcoming the limitations of recoil separation, poor resolution, low acceptance, and other problems encountered in previous (,p) studies
23
Thank you!
HELIOS CollaborationB. B. Back
N. Antler
S. Baker
J. Clark
C. M. Deibel
B. J. DiGiovine
S. J. Freeman
N. J. Goodman
Z. Grelewicz
J. Rohrer
J. P. Schiffer
J. Snyder
M. Syrion
J. C. Lighthall
A. Vann
J. R. Winkelbauer
A. H. Wuosmaa
S. Heimsath
C. Hoffman
B. P. Kay
H. Y. Lee
C. J. Lister
S. T. Marley
P. Mueller
R. C. Pardo
K. E. Rehm
24
Thick target method (14O,p)17F
Experimental set up and excitation energy spectrum[C. Fu et al., Phys. Rev. C 76, 0216603 (2007)]
25
Thin target method: (44Ti,47V)p
FMA acceptance (table), spectra of FMA focal plane without and with 4He in gas target (upper right), and Si spectrum of beam and contaminants (lower right)
[A.A. Sonzogni et al., Phys. Rev. Lett. 84, 1651 (2000)]
4He(44Ti,47V)p 2.2o
4He(34Ar,37K)p 3.6o
4He(30S,33Cl)p 4.2o
4He(30P,33S)p 4.0o
4He(22Mg,25Al)p 6.1o
4He(18Ne,21Na)p 7.0o
4He(14O,17F)p 8.1o
←FMA acceptance (2.5o)
26
Time-inverse method: p(33Cl,30S)
Experimental set-up and preliminary spectrum
[C.M. Deibel et al, in preparation (2009)]
Experimental Set-up
’s
CH2 target
E-E detector
33Cl
Preliminary Results- kinematic curve highlighted
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