1. Nuclear Reaction Studies for Explosive Nuclear Astrophysics
PJ Woods
University of Edinburgh

2. Explosive H burning in Novae
Isaac Newton, Principia Mathematica (1666): ‘from this fresh supply of new fuel those old stars, acquiring new splendour, may pass for new stars’

3. Elemental abundances in novae ejecta
1.35 MSun ONe nova
J. José, M. Hernanz, C. Iliadis. Nucl Phys A, 777, (2006), 3

4. Presolar grains
Grains of nova origin are thought to have a large 30Si/28Si ratio.
Abundance of 30Si is determined by the competition between the 30P β+ decay and the 30P(p,γ)31S reaction rate.
Andrew M Davis. University of Chicago

5. Novae Nucleosynthesis
(p,γ) β+
(γ,p)
30S
31S
32S
33S
27P
28P
29P
30P
31P
2.498m
26Si
27Si
28Si
29Si
30Si

6. H burning reactions at stellar energies
Gamow peak
tunnelling through
Coulomb barrier
Maxwell-Boltzmann
distribution
 exp(-E/kT)
relative probability
energy kT E0
E0
Reaction rate can be dominated by a few
resonances in Gamow burning window

7. However, key resonance strengths, ωγ, unknown
Identified using
4He + 28Si  31S + n reaction
with Gammasphere Ge-array
However, key resonance strengths, ωγ, unknown

8.  where resonance has Гp<< Гγ , ωγ is proportional to Гp
 use transfer reactions to estimate Гp for (p,γ) reactions

9. secondary 30 MeV/u 30P ions GRETINA Target Al 450/600 mg/cm2
P.J. Woods, A Kankainen, H. Schatz, et al. (d,n) transfer reaction cross-section measurements as a surrogate for (p,γ)
secondary
30 MeV/u 30P ions
GRETINA
Target
CD2 ~ 10 mg/cm2
CH2 (background)
Al 450/600 mg/cm2
Be ~1900 mg/cm2
Primary beam:
150 MeV/u 36Ar18+

10. Particle identification: 31S

11. 31S γ-ray energy spectrum
CD2
CH2
5143 keV
6327 keV

12. Levels above the proton threshold energy in 31S
6833
6636
6583
6542
T=0.4 GK
6394
6393
6377
5/2+
6357
T=0.2 GK
3/2-
6327
6283
T=0.1 GK
6259 1+
6159
6138
Sp=6130.9(4) keV
30P + p
31S
Extracted Γp values from cross-section indicate reaction rate is entirely dominated by a single strong resonance at 196 keV

13. 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 (2006)]

14. Supernova Cycle

15. Stellar Life

16. Hydrogen burning in Mg – Al Cycle26 27 28 Si Si Si 25 26 27 Al Al Al 6s
1Myr 24 25 26 Mg Mg Mg
1.809 MeV

17. Direct measurement of 26gAl(p,γ)27Si reaction on
MD1
ED1
Direct measurement of 26gAl(p,γ)27Si reaction on
189 keV resonance, PRL (2006)
 lower energy resonances may dominate destruction of 26Al burning in massive stars?

18. 150 MeV 26gAl beam bombarding 50 μg.cm-2 (CD2)n target
High resolution d(26gAl,p)27Al study of analog states of 27Si resonances using Edinburgh TUDA Si ISAC II Triumf
150 MeV 26gAl beam bombarding 50 μg.cm-2 (CD2)n target
Ibeam~ 5*108 pps
target
proton
26gAl beam
Silicon detectors placed at backward angles, corresponding to forward angle transfer in CoM

19. Energy Resolution in lab frame ~ 40 keV (FWHM)

20. Analogue states to key astrophysical resonances
Continuous background due to protons from fusion
reactions with Carbon atoms in target

22. 26Al(p,γ)27Si reaction rate
 Conclude 9/ keV resonance in 27Si dominates burning of 26Al in Wolf Rayet and AGB stellar environments
See also independent study by Pain et al. PRL 114, (2015)

23. Study of the p(20Ne,2H)19Ne transfer reaction on the ESR heavy ion storage PJW, Y Litvinov et al.
108 20Ne ions
@ 50 MeV/u
8 m
ESR
Electron
cooler
1013 H2/cm2
gas target

24. Detector Pocket
Si –telescope
2 x ~1mm ‘W’-type detectors
16x16 strips

25. DT Doherty, PhD Thesis (2014)
A few hours of data
from test run on ESR
DT Doherty, PhD Thesis (2014)

26. TSR@ISOLDE – Injection of RIBs into ring at MeV/u energies
Spokesperson: K Blaum (Heidelberg)
Deputies: R Raabe(Leuven), PJW (Edinburgh)
entire issue of EPJ (2012)

27. ISOLDE site (west) side
23.3m
24.6m 3m
Proposed layout to fit the TSR at the west side:
Installation above the CERN infrastructure-tunnel
Currently in CERN’s Medium Term Plan (MTP) 27

28. For ultra high resolution mode resolution should be entirely limited
In-ring DSSD System for ultra-high resolution (d,p), (p,d) and (3He,d) transfer studies of astrophysical resonances  Newly funded UK ISOL-SRS project (Spokesperson PJW)
For ultra high resolution mode resolution should be entirely limited
by transverse beam emittance
 resolutions approaching 10 keV FWHM attainable

29. Summary and future
We are entering an exciting phase of development combining a variety of different experimental approaches to determine key H/He burning reaction rates for explosive astrophysical scenarios such as Novae, Supernovae and X-ray bursts. Also important will be studies of static properties of very neutron-rich nuclei eg using AIDA and FAIR and neutron-induced reactions eg new EAR_2

30. New measurement of 26Al(n,p) reaction for Core Collapse Supernovae
C Lederer, T. Davinson, A. Estrade, J. Heyse, C Paradella, P. Schillebeeckxs, PJ Woods
E-detector
10B
Worlds most enriched radioactive 26Al target owned by IRMM Geel
Neutron beam
26Al
dE-E-detectors
Energy
TOF