Results on 62,63 Ni(n,  )

Results on 62,63Ni(n,) Claudia Lederer Goethe University Frankfurt

Outline 63Ni(n,) • measurement • resonances • MACS and astrophysical impact 62Ni(n,) • 62Ni Resonances • 62Ni MACS

63Ni measurement • samples measured (protons for filter runs in brackets): * dedicated pulses, extracted by TTOFsort

63Ni Capture Yield

63Ni Resonances • 12 Resonances identified and fitted up to 55 keV • from 10 keV unresolved cross section with larger energy bins • Yield cross section: neglects MS, Oxygen cross section (NiO sample), other impurities

63Ni Resonances

MACS • Combination of RRR (< 10 keV) and URR (>10 keV)

MACS • Combination of RRR (< 10 keV) and URR (>10 keV) =20-22% almost accepted by PRL

Stellar rates • At high temperatures neutron capture may also happen on excited states • 63Ni levels: 87.15 keV, 155.55 keV, 517.55 keV • for kT=90 keV only 30-40% of neutron captures on ground state • Stellar rate combination of measurement and theory • see papers by T. Rauscher (Int. J. Mod. Phys. 20, 1071 (2011), ApJ 738, 143 (2011), ApJS 201, 26 (2012)) 

Astrophysical implications Two burning stages in massive stars: • He Core burning: kT~26 keV, Nn~106 cm-3 • Carbon shell burning: kT~90 keV, Nn~1011 cm-3 64Zn 65Zn 244 d 66Zn 67Zn 68Zn 62Cu 9.7 m 63Cu 64Cu 12.7 h 65Cu 66Cu 5 m 60Ni 61Ni 62Ni 63Ni 102 a 64Ni 65Ni 2.5 h 58Co 70 d 59Co 60Co 5.3 a 61Co 1.7 h 62Co 14 m 63Co 28 s 56Fe 57Fe 58Fe 59Fe 45 d 60Fe 106 a 61Fe 6 m

Astrophysical implications Rel. to Kadonis: 63Cu/65Cu smaller Link to observed Cu abundances difficult due to explosive nucleosynthesis during SN explosion. 

62Ni(n,): Resonances • Resonances fitted up to 200 keV • New resonances: 2128 eV, 12.2, 20.6, 29.96, 57.6, 67.9, 70.9, 81.5, 97.6, 147, 149, 170, 181 keV • Total 42 resonances fitted for 2009 and 2011 data

62Ni(n,): Resonances • 62Ni too thick to fit that resonance -> use 63Ni yield • Fit of  using previous measurements of n 2g 62Ni sample

62Ni(n,): Resonances • Results from fit: • n=2075 eV: ER=4621 eV, =2.687 eV (l=0) • n=1822 eV: ER=4607 eV, =2.401 eV (l=0) • Thermal xs: • 16.4 b • 12.9 b • 14.2 b • 62Ni too thick to fit that resonance -> use 63Ni yield • Fit of Gg using previous measurements of Gn

62Ni(n,): Capture Kernels • 62Ni too thick to fit that resonance -> use 63Ni yield • Fit of Gg using previous measurements of Gn

Uncertainties of MACS • WFs: 2% • Normalization: 1% • Flux: 5% (since region between 8-80 keV is most important) • BIF(En): 0.5% • 4.6 keV Res: 4%-1% (5keV – 90 keV) • Statistics: 0.7%-5.9% (5keV-90keV) • Total: 6.9%-8.1% •  Most accurate measurement so far + covering the widest energy range!

MACS RPs up to 200 keV (n_TOF), then JENDL

MACS

Level Density • fit: #(levels)=a*Energy+b • a= 0.000321, b=0.7 • 190 keV -> 61 levels expected, observed 42

THE END

63Ni Pointwise Cross Section

63Ni Pointwise Cross Section XS at 0.025 eV ~35 b XS resonances ~ 20 b Exp. Values: 15-30b

MACS statistical uncertaintiy • Fit result from capture measurement: Kernel Ag=gn/(n+) Area of the resonance 

MACS statistical uncertaintiy • Fit result from capture measurement Kernel Ag=gn/(n+) Area of the resonance • Statistical error with W=ERexp(-ER/kT) is: 

Uncertainties of Kernels and MACS • 2 datasets: 2009 and 2011 • 2 sets of resonance parameters • Final capture kernel is weighted mean value of 2009 and 2011 kernel • Uncertainty of Kernel is the max. of propagated uncertainty of fit and standard deviation • MACS: 4 sets of MACS (2009, 2011, two different fits of 4.6 keV resonance): • Step 1: mean value of 2009 and 2011 for the 2 different versions with statistical uncertainty derived from averaged capture kernels • Step 2: average for the 2 different fits at 4.6 keV where the standard deviation enters into the systematic uncertainty of the MACS

Results on 62,63 Ni(n,  )