PJ Woods

University of Edinburgh

N

A personal view of the shape of things to come in Explosive Nuclear Astrophysics

Elemental abundances in novae ejecta

J. José, M. Hernanz, C. Iliadis. Nucl Phys A, 777, (2006), 550-578

1.35 MSun ONe nova

Presolar grains

Andrew M Davis. University of Chicago

o Grains of nova origin are thought to have a large 30Si/28Si ratio.

o Abundance of 30Si is determined by the competition between the 30P β+ decay and the 30P(p,γ)31S reaction rate.

Novae Nucleosynthesis

30S

26Si 27Si

27P 28P

28Si

29P 31P

29Si 30Si

31S 32S

32Cl 33Cl(p,γ)

β+

2.498m

30P

31Cl

33S

34Cl

(γ,p)

30P(p,γ)31S reaction rate using new resonance data

However, key resonance strengths, ωγ , based on systematic values for proton spectroscopic factors

use transfer reactions to estimate Гp for (p,γ) reactions

where resonance has Гp<< Гγ , ωγ is proportional to Гp.

Гp α Pl (barrier penetration factor) X S(spectroscopic factor)

21

T1 )1J2)(1J2(

1J2

σtransfer = σDWBA X S

New technique for (d,n) studies of (p,γ) resonance strengths with GRETINA γ-array and S800 spectrometer

PJW, H Schatz et al., NSCL, April 2013

~106 30P 30 MeV/u ions on CD2 target

Measure σ(d,n)INT Гp forstrong resonances

31S gamma spectrum

6327 keV

5143 keV

CD2

CH2

Analysis - A Kankainen

Astrophysically relevant levels in 31S

613861596259628363276357637763936394

65836542

6636

Sp=6130.9(4) keV

31S

3/2-

6833

30P + p

1+

T=0.2 GK

T=0.4 GK

T=0.6 GK

T=0.1 GK

5/2+

Reaction calculations of Γp from data being performed by F Nunes

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

INTEGRAL satellite telescope - 2.8(8) Msun of 26Al in our galaxy [R. Diehl, Nature 439 45(2006)]

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

MD1

ED1

Direct measurement of 26gAl(p,γ)27Si reaction on 188 keV resonance, PRL 96 252501(2006)

lower energy resonances may play dominant role for destruction of 26Al burning in W-R stars?

0 increasing excitation energyAstrophysicall

y Important

Region

150 MeV 26gAl (CD2)n targetIbeam~ 5*108 pps

proton

High resolution d(26gAl,p)27Al study of analog states of 27Si resonances using Edinburgh TUDA Si array @ Triumf

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

+

Exotic reaction since Jπ = 5+ for 26gAl!

Key analog states

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

Future 26mAI(3He,d)27Si study on TSR storage ring@ISOLDE

isomer can be excited incore collapse supernovae-influences ‘extinct’ 26Alobserved in meteorites asexcess 26Mg

In-ring DSSD System for ultra-high resolution (d,p), (p,d) and (3He,d) transfer studies of astrophysical resonances

ISOL-SRS project

For ultra high resolution mode resolution should be entirely limited

by transverse beam emittance

resolutions approaching 10 keV FWHM attainable T Davinson

TSR@ISOLDE – Injection of RIBs into ring at MeV/u energies

entire issue of EPJ 207 1-117 (2012)

Spokesperson K Blaum (MPIK)

18

ISOLDE site (west) side

Proposed layout to fit the TSR at the west side:- Installation above the CERN infrastructure-tunnel

24.6m23.3m

3m

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

The Hot CNO Cycles

12C

13N

14O

18Ne

14N

17F 18F

15O

15N

19Ne

13C

16O

(p, )(, )

(, p)

+(p, )

Hot CNO cycle

rp-process

Key unknown - α-decay probability from excited state at

4.03 MeV in 19

Ne compared to γ-decay, predicted to be ~ 10-4

108 20Ne ions@ 50 MeV/u

1013 H2/cm2 gas target

Electron cooler

ESR

8 m

Study of the p(20Ne,2H)19Ne transfer reaction on the ESR@GSIPJW, Y Litvinov et al.

A few hours of datafrom test run on ESR

DT Doherty, PhD Thesis (2014)

Nucleosynthesis above Fe

Fe

Ni

Zn

Ge

Se

r-proce

ss

p, νp, rp

-process

?

s-process: <n

~50%

>n

~ 50%

~1%

Puzzle of the origin of heavy ‘p-nuclei’ – abundant

proton-rich isotopes eg 92

Mo and 96

Ru

Supernova shock

passing through

O-Ne layers of

progenitor star

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

Predicted p-process abundances compared to observed abundances

Fully stripped 96

Ru44+

ions

ions injected

@ 100 MeV/u

Reduced to

~10MeV/u

Gas Stripper

Carbon Foil

Stripper

Study of 96

Ru(p,γ)97

Rh reaction with decelerated beams

using the ESR storage ring at GSI

Gas jet

Particle detectors

Pioneering new technique on ESR (Heil, Reifarth) – heavy recoils

detected with double-sided silicon strip detector (Edinburgh)

Position distribution of recoiling ions

measured by DSSD

σ(p,γ)= 3.6(5) mb ~10 MeV/u

New DSSD system being developed (Edinburgh/GSI/Frankfurt)

for use in UHV on ESR to measure p-process capture reactions

in Gamow burning energy region – test run Autumn 2014.

Observations of Elemental Abundances in old metal poor stars:

Evidence for robust r-process mechanisms

(C. Sneden, J.J. Cowan, et al.)

However, for elements below Z ~50 eg Yttrium evidence of need for a

second astrophysical mechanism/site

Sites of the r-process

r-process related to environments with high-neutron

density and high temperature.

Type II supernovae prime suspects…

Neutron star mergers and accretion disks in -ray

bursts promising alternatives.

Not enough is known at

present about the physics

to create realistic models

First direct evidence for neutron star merger - kilonova Hubble space telescope images of afterglow of a

gamma-ray burst, Berger et al. arXiv:1306

Accessing the r-process path @ RIKEN and FAIR

Masses (Sn)

(location of the path)

-decay half-lives

(progenitor abundances,

process speed)

-delayed n-emission

branchings

(final abundances)

Advanced Implantation Detector Array (AIDA) will be used for decay studies of r-process nuclei at RIBF and FAIR

Compact high density ASIC electronics instrumentation for multi-channel Double-sided

Silicon Strip Detectors (DSSD)

238U fission fragments from BIG

RIPs @ RIKEN

N

AIDA Test at RIKEN May 1st for 10 days

First full use of AIDA system will be in conjunction with EURICA gamma-ray array on BIG RIPs separator@RIKEN

Accepted proposal, PI Alfredo Estrade

to measure simultaneously masses, half-lives and

spectroscopy of nuclei in N~56 region of r-process

Are nuclear shell effects responsible for anomalous

abundances of light r-process elements in metal poor stars?

Double shell closure at 90Se56 ?

BRIKEN collaboration formed for proposed campaign of β-n measurements on Big RIPS separator@RIKEN

Also plans to couple to Total Absorption Spectroscopy system GT – strength function measurements

Direct and indirect neutron induced reaction studies

• Direct studies with small radioactive target samples will benefit from the new EAR-2 n_ToF facility @ CERN and the high intensity FRANZ facility@Frankfurt

• New ideas should be explored for ‘neutron targets’ for RIBs eg Reifarth/Litvinov storage ring/reactor idea PR ST- accelerators and beams 17, 014701 (2014).

• Indirect/surrogate methods eg Coulex ( eg R3B@FAIR), transfer reactions (eg TSR@ISOLDE) need to be explored in much greater depth for reproducing (n,γ) reactions with radioactive species.

Summary

• variety of techniques and facilities needed to address key reactions and properties of unstable nuclei for explosive nuclear astrophysics

• need world class ISOL and fragmentation facilities in Europe to lead this burgeoning area of science