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

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’

Elemental abundances in novae ejecta 1.35 MSun ONe nova J. José, M. Hernanz, C. Iliadis. Nucl Phys A, 777, (2006), 550-578 3

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

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

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

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

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

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+

Particle identification: 31S

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

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

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)]

Supernova Cycle

Stellar Life

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

Direct measurement of 26gAl(p,γ)27Si reaction on MD1 ED1 Direct measurement of 26gAl(p,γ)27Si reaction on 189 keV resonance, PRL 96 252501(2006)  lower energy resonances may dominate destruction of 26Al burning in massive stars?

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 array @ 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

Energy Resolution in lab frame ~ 40 keV (FWHM)

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

26Al(p,γ)27Si reaction rate  Conclude 9/2+ 127 keV resonance in 27Si dominates burning of 26Al in Wolf Rayet and AGB stellar environments See also independent study by Pain et al. PRL 114,212501 (2015)

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

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

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

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 207 1-117 (2012)

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

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

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 system@RIBF and FAIR and neutron-induced reactions eg new EAR_2 line@CERN

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