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

16

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