1. Status on 62,63 Ni(n, ) Claudia Lederer Goethe University Frankfurt Cristian Massimi INFN Bologna

2. Introduction 62 Ni(n, ) measurement 2009 and 2011 63 Ni(n, ) measurement 2011 Detector calibration: Weighting functions: Normalization: Background subtraction: Resonance analysis:

3. Introduction 62 Ni(n, ) measurement 2009 and 2011 63 Ni(n, ) measurement 2011 Detector calibration: DONE Weighting functions: DONE Normalization: DONE Background subtraction: EMPTY+AMBIENT (filter dips match to empty + filters) Resonance analysis: This talk

4. 62 Ni(n, ) 2009 vs. 2011 Agreement at low energy side <5%

5. 62 Ni(n, ) 2009 vs. 2011 Agreement at low energy side <5% Agreement individual resonances: to be investigated This talk: only data of 2011 used

6. 62 Ni(n, ) known resonances

8. Resonance analysis: SAMMY Reich Moore Approximation, RPI phase I, simulated BIF Systematic uncertainties: 5.5% total (Flux, WFs, Normalization,..) propagated

9. Resonance analysis: SAMMY Reich Moore Approximation, RPI phase I, simulated BIF Systematic uncertainties: 5.5% total (Flux, WFs, Normalization,..) propagated Problems: Fit results sometimes worse than initial parameters Uncertainties given sometimes ridiculously small Choice of correct fudge factor

10. 62 Ni(n, ) fit of known resonances 8-90 keV n = 35±0.3 meV = 1000±10 meV E R = 8439 eV J=0.5 - l=1 n = 581±6 meV = 1014±10 meV E R = 9540 eV J=0.5 - l=1

11. 62 Ni(n, ) fit of known resonances 8-90 keV n = 197±2 meV = 1004±10 meV E R = 17793 eV J=0.5 - l=1 n = 265±3 meV = 1221±12 meV E R = 24625 eV J=0.5 - l=1

12. 62 Ni(n, ) fit of known resonances 8-90 keV n = 562±6 meV = 1088±11 meV E R = 28430 eV J=0.5 - l=1 n = 1350±13 meV = 997±10 meV E R = 29508 eV J=0.5 - l=1

13. 62 Ni(n, ) fit of known resonances 8-90 keV n = 544±5 meV = 1004±11 meV E R = 34484 eV J=0.5 - l=1 n = 1829±18 meV = 2000±20 meV E R = 38281 eV J=0.5 - l=1 ?

14. 62 Ni(n, ) fit of known resonances 8-90 keV n = 307±3 meV = 945±9 meV E R = 40550 eV J=0.5 - l=1 n = 308±3 meV = 1016±10 meV E R = 41246 eV J=0.5 - l=1 n = (3.5±0.3)e5 meV = 700±7 meV E R 43000 eV J=0.5 + l=0

15. 62 Ni(n, ) fit of known resonances 8-90 keV n = 1020±10 meV = 970±10 meV E R = 45139 eV J=0.5 - l=1 n = 318±3 meV = 987±10 meV E R = 53399 eV J=0.5 - l=1 n = 14699±146 meV = 281 ±3 meV E R = 57011 eV J=0.5 - l=1

16. 62 Ni(n, ) fit of known resonances 8-90 keV n = 345±4 meV = 1002±10 meV E R = 63449 eV J=0.5 - l=1 n =2158±21 meV = 1093±11 meV E R = 74433 eV J=0.5 - l=1

17. 62 Ni(n, ) fit of known resonances 8-90 keV n = 345±4 meV = 1002±10 meV E R = 63449 eV J=0.5 - l=1 n =449±4 meV = 3057±30 meV E R =77498 eV J=0.5 + l=0

18. 62 Ni(n, ) fit of known resonances 8-90 keV n = 345±4 meV = 1002±10 meV E R = 63449 eV J=0.5 - l=1 n =20825±207 meV =538±53 meV E R =78505 eV J=0.5 + l=0

19. The unfittable resonance at 4.6 keV Previous data:

20. The unfittable resonance at 4.6 keV Case 1: keep n =1.822 keV constant Litvinskiy et al. Fit from 3-8 keV E R =4.641±0.003 eV =2.895±0.003 eV

21. The unfittable resonance at 4.6 keV Case 2: start with n =2.026 keV and =2.376 eV (=JENDL) and vary everything Fit from 3-8 keV E R =4.617 keV =3.037 eV n =2.042 eV

22. The unfittable resonance at 4.6 keV Case 2: start with n =2.026 keV and =2.376 eV (=JENDL) and vary everything Fit from 3-8 keV E R =4.617 keV =3.037 eV n =2.042 eV ??????

23. Problem with multiple scattering corrections? SAMMY input: Multiple, finite slab

24. Multiple Scattering for 62 Ni in 63 Ni sample

25. 62 Ni in 63 Ni sample n fixed to 1.8 keV: ~2.4 eV Fitting both: n =2.2 keV: =3.2 eV Including first fit of 59 Ni and 63 Ni resonances (p wave assignment) better agreement at thermal neutron energies

26. 62 Ni in 63 Ni sample n fixed to 1.8 keV: ~2.4 eV Fitting both: n =2.2 keV: =3.2 eV Thermal cross sections: 62 Ni: 15 b (prev. 13-15 b) 63 Ni: 25 b (prev. 20-26 b) Including first fit of 59 Ni and 63 Ni resonances (p wave assignment) better agreement at thermal neutron energies

27. Conclusions: good progress on 63 Ni data, sample composition known to about 1% accuracy (mass ratios 63/62, 59/62 etc...) 62 Ni sample is too thick to fit the 4.6 keV resonance since multiple scattering corrections are much larger than the 0- scattering capture yield extraction of 62 Ni RP for that resonance is problematic (powder sample, characterization...) is it worth to remeasure that resonance with a thinner sample?