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