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Final results on 54 Fe and 57 Fe(n, g ) Cross Sections measured at CERN n_TOF Giuseppe Giubrone

Final results on 54 Fe and 57 Fe(n, g ) Cross Sections measured at CERN n_TOF Giuseppe Giubrone Instituto de Fisica Corpuscular Valencia n_TOF meeting, Manchester, May 2013. OUTLINE. Experimental details Overview of the measurements 54 Fe and 57 Fe Analysis 54 Fe Capture Kernels

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Final results on 54 Fe and 57 Fe(n, g ) Cross Sections measured at CERN n_TOF Giuseppe Giubrone

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  1. Final results on 54Fe and 57Fe(n,g) Cross Sections measured at CERN n_TOF Giuseppe Giubrone Instituto de Fisica Corpuscular Valencia n_TOF meeting, Manchester, May 2013

  2. OUTLINE Experimental details Overview of the measurements 54Fe and 57Fe Analysis 54Fe Capture Kernels 57Fe Capture Kernels

  3. Experimental Details Samples Isotopic composition Experimental setup for 54Fe (2010 ) and 57Fe(2011) Borated water moderator

  4. Fe-54 anlysis: Overview ENDF n_TOF • When compared versus ENDF, most of the s-wave and p-wave resonances are clearly visible in the n_TOF data with good statistics up to high neutron energies of about 100 keV. • In the n_TOF data, additional resonances are visible, some are from sample impurities but also new resonances of Fe-54 not evaluated thus far.

  5. Fe-57 analysis: Overview ENDF ENDF n_TOF When compared versus ENDF, most of the s-wave and p-wave resonances are clearly visible in the n_TOF data with good statistics and additional resonances are visible, some are from sample impurities but also new resonances of Fe-57 not evaluated thus far.

  6. Fe-54: Summary of Capture Kernels Comparison n_TOFvs. GEEL vs. ORNL • In the n_TOF data, a total of 169 resonances are clearly visible in the energy range up to 500 keV. 102 out of them show a statistical deviation less than 50% with an average RMS of 22% (Group 1). • The statistics of the remaining 67 resonances are low thus yielding an average RMS of 92% (Group 2). However, these 67 resonances are clearly visible in the data, as it is shown in the example of the next slide. • In the R-Matrix fit typically the value of chi-square is between 0.9 and 1.4. • Compared versus the previous experiment at GEEL (Corvi et al.) the n_TOF kernels are -in average- (0.7± 1.6)% higher in the energy range from 1eV to 200 keV. (The analysis of the GEEL data ends at 200 keV). • Compared versus the previous experiment at ORNL (Allen et al.) the n_TOF kernels are -in average-(-12.3±1.6)% higher in the energy range from 1eV to 200 keV.

  7. In the n_TOF data, a total of 169 resonances are clearly visible in the energy range up to 500 keV. 102 out of them show a statistical deviation less than 50% with an average RMS of 22% (Group 1). • The statistics of the remaining 67 resonances are low thus yielding an average RMS of 92% (Group 2). However, these 67 resonances are clearly visible in the data, as it is shown in the example of the next slide. • In the R-Matrix fit typically the value of chi-square is between 0.9 and 1.4. • Compared versus the previous experiment at GEEL (Corvi et al.) the n_TOF kernels are -in average- (0.7± 1.6)% higher in the energy range from 1eV to 200 keV. (The analysis of the GEEL data ends at 200 keV). • Compared versus the previous experiment at ORNL (Allen et al.) the n_TOF kernels are -in average-(-12.3±1.6)% higher in the energy range from 1eV to 200 keV.

  8. Example of a resonance in Group 1: Example of a resonance in Group 2: Kernel statistical uncertainty 3% Kernel statistical uncertainty 121%

  9. Average deviation of capture kernels n_TOF vs Corvi et al.(GEEL) • The average deviation (weighted by error bars) is of (0.76 ± 1.6)%

  10. Average deviation of capture kernels n_TOF vs Allen et al.(ORNL) • The average deviation (weighted by error bars) is of (-12.3 ± 1.6)%

  11. Fe-57: Summary of Capture Kernels Comparison n_TOF vs. GEELvs. ORNL • A total of 115 resonances are clearly visible in the n_TOF data. • 68 of them show an statistical error (one stanard deviation) less than 50% with an average RMS of 22%. • In the R-Matrix fit typically the value of chi-square is between 0.9 and 1.6. • The remaining 47 resonances have an average RMS of 91%. • Compared versus the previous experiment at GEEL (Rohr et al.) the n_TOF kernels are -in average- (-17± 1.6)% higher in the energy range from 1eV to 130 keV. • Compared versus the previous experiment at ORNL (Allen et al.) the n_TOF kernels are -in average-(-2.5±1.5)% higher in the energy range from 1eV to 130 keV.

  12. A total of 115 resonances are clearly visible in the n_TOF data. • 68 of them show an statistical error (one stanard deviation) less than 50% with an average RMS of 22%. • In the R-Matrix fit typically the value of chi-square is between 0.9 and 1.6. • The remaining 47 resonances have an average RMS of 91%. • Compared versus the previous experiment at GEEL (Rohr et al.) the n_TOF kernels are -in average- (-17± 1.6)% higher in the energy range from 1eV to 130 keV. • Compared versus the previous experiment at ORNL (Allen et al.) the n_TOF kernels are -in average-(-2.5±1.5)% higher in the energy range from 1eV to 130 keV.

  13. Average deviation of capture kernels n_TOF vs Rohr et al.(GELINA) • The average deviation (weighted by error bars) is of (-18 ± 1.6)% • This difference is visible in the next slide were a comparison between the final yield and the yield given by GEEL data is made.

  14. GEEL

  15. Average deviation of capture kernels n_TOF vs Allen et al.(ORNL) • The average deviation (weighted by error bars) is of (-2.5 ± 1.5)%

  16. Summary & Outlook of 54,57Fe(n,g) analysis • A total of 169 resonances were analyzed in 54Fe. • In the n_TOF 54Fe (n, g) data 4 new resonances appear, not reported in the previous experiment. • 102 out of the 169 analyzed resonances show an average standard deviation of 22%. • The average deviation with respect to the GEEL data is of (0.7± 1.6)%. • The average deviation with respect to the ORNL data is of (-12.3 ± 1.5)%. • A total of 115 resonances for 57Fe were analyzed. • In the n_TOF 57Fe (n, g) 6 resonances not tabulated in the previous experiment were analyzed. • 68 of these resonances show a standard deviation of less than 50% with an average standard deviation of 21%. • For 57Fe the average deviation between n_TOF and GEEL is of (-18 ± 1.63) % in the energy range up 130 keV. • The average deviation between n_TOF and ORNL is of (-2.5 ± 1.5) % in the energy range up 130 keV.

  17. BACKUP SLIDES

  18. Beam interception factor • The beam intercaption factor was calculated for different setups as reported in the • next slide. • An example of the fit obtained with Sammy for the Gold sample, to obtain the beam • intercaption factor is shown below.

  19. Fe-54 and Fe-57analysis Threshold Correction

  20. Fe-54 and Fe-57analysis As the cross section are measured with respect to a reference sample(Gold in our case), is convenient to simulate a large number of cascade for the 4.9eV resonance for 197Au, and for all spin groups and parity for the 54Fe and 57Fe resonance. Considering a 250keV threshold , the correction to apply at the experimental yield is: Ftot=Ft(54,57Fe)/Ft(198Au) For both detectors and isotopes Ftot is 0.94(±0.05%). Therefore , a correction of 6% is applied to the fitted 54,57Fe Kernels. Next slides show a comparison between the simulated and measured (Bicron) detector response, for the 4.9eV Au resonance and for all the spin-groups in 54,57Fe.

  21. Fe-54 and Fe-57analysis Comparison between simulated and measured deposited energy 198Au

  22. Fe-54 and Fe-57analysis Simulated response for different spin groups for 54Fe

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