Nuclear Astrophysics with

the TSR@ISOLDEPJ Woods, University of Edinburgh

N

Puzzle of the origin of heavy ‘p-nuclei’ – abundant proton-rich isotopes eg 92Mo and 96Ru

Supernova shock passing throughO-Ne layers of progenitor star

Predicted p-process abundances

relative to observed abundances

Arnould & Goriely Phys. Rep. 384,1 (2003)

Study of 96Ru(p,γ)97Nb reaction with decelerated beams on ESR using DSSD system for recoil detection

(GSI, Frankfurt,Edinburgh)

Reaction peak

observed!

σ(p,γ)= 3.6(5) mb

Measurements of (p,) or (α,) rates in Gamow window for the astrophysicalp-process using inverse kinematics .

Advantages of ring approach:

• Applicable to radioactive nuclei• Detection of ions via in-ring particle

detectors (low background, high efficiency)

• Measurements of (p,n) reactions also possible

Gas jet

Particle detectors

New DSSD system being jointly developed by EdinburghGSI and Frankfurt for use in UHV for measuring reactions

in centre of Gamow burning energy region.

Application of p-process method to TSR@ISOLDE

Advantages:

RIBs can be injected into TSR at appropriate energy and do not needtime consuming deceleration phase loss of beam intensity due to radiaoctive decay

RIBs when injected from HIE-ISOLDE will already have good beamquality characteristics less cooling time required in ring

Challenge:

To produce fully stripped ions of relatively high Z(>30-70<) High electron capture stripping reaction cross-section will swamp recoil

detector and reduce beam lifetime

Galactic abundance distribution of the cosmic γ-ray emitter 26Al

INTEGRAL Measured abundance 2.8(8) Solar Masses[R. Diehl, Nature 439, 45(2006)]

Presolar grains

Andrew M Davis. University of Chicago

o Grains are found to have a high 26Mg/24Mg abundance ratio thought to reflect injection of 26Al material which subsequently β-decays

Supernova Cycle

Mg-Al Cycle

MgMg MgMg MgMg

AlAl AlAl AlAl

SiSi SiSi SiSi

2424 2525 2626

2525 2727

2626

2626

2727 2828

1.809 MeV

1.809 MeV

1Myr

6s

Hydrogen burning in Mg – Al Cycle

Next stage to estimate resonance strengths

21

T1 )1J2)(1J2(

1J2

Use transfer reactions to determine Гp for (p,γ) reactions

New high resolution study performed of the d(26gAl,p)27Al analogue reaction using the Edinburgh group’s TUDA silicon strip detector array on the ISAC II facility at Triumf (June 2012)

NB exotic reaction since 26gAl has Jπ = 5+!

d(26gAl,p)27Al study using TUDA@ISAC G. Lotay, PJW et al.

0 increasing excitation energy

Astrophysically

ImportantRegion

717

5

9/2

+

729

2

13/2

+

740

2

11/2

+

744

4

13/2

+

766

4

9/2

+

780

6

9/2

+

794

8

11/2

+

804

3

9/2

−

809

7

5/2

+

In-ring target chamber & heavy-ion recoil detection system in UHV

Indirect Studies of Key Astrophysical Resonances

e.g. d(26mAl, p)27Aldestruction of 26Al incore collapse supernovae- meteoritic abundances

Transfer reaction studies of astrophysical resonances on the TSR@ISOLDE

• High resolution studies possible with high quality RIBs vital for resolution of key resonance in regions of high level density, Ex ~ 6-8 MeV • Ions injected at perfect energy for transfer ~6 MeV/u

• Most important reactions have relatively low Z ions, relatively close to stability

intense fully stripped RIBs with long lifetimes

• use of isomeric beams eg 26mAl

• no background from reactions on target impurities eg Carbon from (CH2)n

The 15O(,)19Ne reaction: the nuclear trigger of X-ray bursts

Reaction regulates flow between the hot CNO cycles and rp process critical for explanation of amplitude and periodicity of bursts

12C

13N

14O

18Ne

14N

17F 18F

15O

15N

19Ne

13C

16O

(p, )(, )

(, p)

+(p, )

CNOcycle

Hot CNO cycle

Γα /Γ ≈

Rate dominated by a single 3/2+ resonance at 504 keV

Key experimental uncertainty, alpha branching ratio

First transfer reaction measurement at the ESR

• data evaluation under way

P. Woods et al.

AP

2.795 MeV 1/2-state in 19Ne 4.033 MeV 3/2+

state in 19Ne

Experiment: 08-14 October 201220Ne(p,d)19Ne

reaction

108 20Ne ions@ 50 MeV/u

1013 H2/cm2 gas target

Electron cooler

ESR

Online data

Summary and Forward Look

• Exciting new developments in explosive nuclear astrophysics will be opened up by TSR@ISOLDE

• Transfer reaction studies of nuclear astrophysical resonances will require development of high resolution, high efficiency silicon strip detector system(s) operating in UHV conditions around target.

• p-process radiative capture studies will require development of fully stripped high Z ions, and forward angle heavy ion recoil detector system in region of 1st TSR dipole.

• Thought will need to be given to the transfer of expertise for development of thick gas jet targets ~1013-14

atoms/cm2

Beam parameters