H/He burning reactions on unstable nuclei for Nuclear Astrophysics PJ Woods University of Edinburgh H T O F E E U D N I I N V E B R U S I R T Y H G
Explosive H/He burning in Binary Stars Isaac Newton, Principia Mathematica (1666): from this fresh supply of new fuel those old stars, acquiring new splendour, may pass for new stars
J. José, M. Hernanz, C. Iliadis. Nucl Phys A, 777, (2006), 550-578 Elemental abundances in novae ejecta 1.35 M Sun ONe nova
Presolar grains o Grains of nova origin are thought to have a large 30 Si/ 28 Si ratio. o Abundance of 30 Si is determined by the competition between the 30 P β + decay and the 30 P(p,γ) 31 S reaction rate. Andrew M Davis. University of Chicago
Novae Nucleosynthesis (p,γ) 31 Cl 32 Cl 33 Cl 34 Cl β + (γ,p) 30 S 31 S 32 S 33 S 27 P 28 P 29 P 31 P 30 P 26 Si 27 Si 28 Si 29 Si 30 Si
Sensitivity to uncertainty in 30 P(p,γ) 31 S reaction rate Relative change in abundance 30 P(p,γ) 31 S Mass number C. Iliadis, A. Champagne, J José et al., Astrophys. J. Suppl. Ser. 142, 105 (2002)
H/He burning reactions at stellar energies Maxwell-Boltzmann distribution exp(-e/kt) tunnelling through Coulomb barrier exp ' ( k / E ) relative probability Gamow peak ΔE 0 kt E 0 energy Reaction rate often dominated by a few resonances in Gamow burning window
Known 31 S level scheme o States populated by 20 Ne( 12 C,n) 31 S 31 S proton threshold D.G. Jenkins et al, Phys. Rev. C. 72. (2005)
4 He + 28 Si à 31 S + n fusion reaction
Pairing of new levels with analog states in mirror nucleus
30 P(p,γ) 31 S reaction rate using new resonance data However, key resonance strengths, ω γ, based on systematic values for proton spectroscopic factors
ωγ = (2J 1 2J R + 1 + 1)(2J 2 + 1) Γ p Γ Γ tot γ use transfer reactions to estimate Г p for (p,γ) reactions where resonance has Г p << Г γ, ω γ is proportional to Г p. Г p α P l (barrier penetration factor) X S(spectroscopic factor) σ transfer = σ DWBA X S
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 30 P ions GRETINA Target CD2 ~ 10 mg/cm 2 CH2 (background) Be ~1900 mg/cm 2 Al 450/600 mg/cm 2 Primary beam: 150 MeV/u 36 Ar 18+
Particle identification: 31 S 30P 31 S
31 S γ-ray energy spectrum 5143 kev CD2 CH2 6327 kev
Levels above the proton threshold energy in 31 S 6833 6636 T=0.6 GK 1+ 30 P + p 5/2 + 3/2-6583 6542 6394 6393 6377 6357 6327 6283 6259 6159 6138 T=0.4 GK T=0.2 GK T=0.1 GK Sp=6130.9(4) kev 31 S Calculations of extracted Γ p values from cross-section data being performed by F Nunes (MSU)
Galactic abundance distribution of the cosmic γ-ray emitter 26 Al INTEGRAL satellite telescope - 2.8(8) M sun of 26 Al in our galaxy [R. Diehl, Nature 439 45(2006)]
Supernova Cycle
Stellar Life
Mg-Al Cycle 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
MD1 ED1 Direct measurement of 26g Al(p,γ) 27 Si reaction on 189 kev resonance, PRL 96 252501(2006) à lower energy resonances may dominate destruction of 26 Al burning in massive stars?
Factor ~ 10 4 reduction in uncertainties in estimated 26g Al(p,γ )27 Si reaction rate 10 8 K However, resonance strengths for critical low T 26 Al burning regime in Wolf-Rayet stars still need to be determined
High resolution d( 26g Al,p) 27 Al study of analog states of 27 Si resonances using Edinburgh TUDA Si array @ Triumf 150 MeV 26g Al à (CD 2 ) n target I beam ~ 5*10 8 pps proton 0 à increasing excitation energy Astrophysically Important Region
7175 9/2 + 7292 13/2 + 7402 11/2 + 7444 13/2 + Key analog states 7664 9/2 + 7806 9/2 + 7948 11/2 + 8043 9/2 9/2 + 8097 5/2 + à Lower energy resonance strength much higher than expected?
The 15 O(α,γ) 19 Ne reaction: the nuclear trigger of X-ray bursts Reaction regulates flow between the hot CNO cycles and rp process à critical for explanation of amplitude and periodicity of bursts
The Hot CNO Cycles
15 O(α,γ) 19 Ne reaction rate predicted to be dominated by a single resonance at a CoM energy of 504 kev Key unknown - α-decay probability from excited state at 4.03 MeV in 19 Ne compared to γ-decay, predicted to be ~ 10-4
p( 21 Ne, 3 H) 19 Ne* Background produced by reactions of 21 Ne beam with 12 C in target <4.3 10-4
Study of the p( 20 Ne, 2 H) 19 Ne transfer reacuon on the ESR heavy ion storage ring @GSI, PJW, Y Litvinov et al. 8 m 10 8 20 Ne ions @ 50 MeV/u ESR Electron cooler 10 13 H 2 /cm 2 gas target
Detector Pocket Si telescope 2 x ~1mm W - type detectors 16x16 strips
Particle ID plot for DSSD ΔE1 d fast α s p E1 + E2
DT Doherty, PhD Thesis (2014) A few hours of data from test run on ESR
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 Proposed layout to fit the TSR at the west side: - Installation above the CERN infrastructure-tunnel 3m 35
Future 26m AI(d,p) 27 Al study on TSR storage ring@isolde In-ring target chamber & heavy-ion recoil detection system in UHV isomer can be excited in core collapse supernovae - influences extinct 26 Al observed in meteorites as excess 26 Mg
In-ring DSSD System for ultra-high resolution (d,p), (p,d) and ( 3 He,d) transfer studies of astrophysical resonances à Newly funded UK ISOL-SRS project (Spokesperson PJW) For ultra high resolution mode resolution should be entirely limited by transverse beam emittance à resolutions approaching 10 kev FWHM attainable
Pioneering new technique on ESR (Heil, Reifarth) heavy recoils detected with double-sided silicon strip detector (Edinburgh) Particle detectors Position distribution of recoiling ions measured by DSSD Gas jet σ 96Ru(p,γ)= 3.6(5) mb @ ~10 MeV/u New DSSD system developed (Edinburgh/GSI/Frankfurt) for p-process capture reactions in Gamow burning window à CRYRING@GSI
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
Summary 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.