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Cross-section s of Neutron Threshold Reactions Studied by Activation Method

Nuclear Physics Institute, Academy of Sciences of Czech Republic Department of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague. Cross-section s of Neutron Threshold Reactions Studied by Activation Method.

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Cross-section s of Neutron Threshold Reactions Studied by Activation Method

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  1. Nuclear Physics Institute, Academy of Sciences of Czech Republic Department of Nuclear Reactors, Faculty of Nuclear Sciences andPhysical Engineering, Czech Technical University in Prague Cross-sections of Neutron Threshold Reactions Studied by Activation Method NEMEA-6, Krakow, 25.-28.10.2010 J. Vrzalová, O. Svoboda, A. Krása, M. Majerle, A. Kugler, A. Laredo, M. Suchopár, V. Wagner

  2. Outline • - Motivation • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • Motivation • Cross-section measurements • Neutron sources in NPI and TSL • Background subtraction • Experiments on Cyclotron in Řež • TSL Uppsala experiments • Comparison • Conclusion

  3. Motivation • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • measurement of spatial distribution of neutrons is important part of studies by means of set-upsbased on spallation neutron source • the activation detectors are very useful tool for neutron field determination in this case • for neutron detection are used threshold reactions on Au, Al, Bi, In, Ta, Co, Y • almost no experimental cross-section data for most of observed threshold reactions are available for higher neutron energies (E>30MeV)→it is necessary to perform new cross-section measurements

  4. Ta Al Au Bi Co In Detection of neutrons • Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  5. Evaluation - DEIMOS • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  6. Spectroscopiccorrections Real γ-γ cascade coincidences Self-absorption • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion Detector efficiency decay during cooling decay during irradiation unstable irradiation non-point like emitters detector dead time

  7. Dead time correction Decay during cooling and measurement Peak area Self-absorption correction Beam correction γline intensity Decay during irradiation Weight normalization Detector efficiency Correction for coincidences Square-emitter correction Evaluation - total yield • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  8. Cross-sectionmeasurements • Requirements for s-measurements by activation method: • high energy neutron source with good intensity • monoenergetic (quasi-monoenergetic) neutrons or well known spectrum • pure monoisotopic samples • good spectroscopic equipment – g and X-rays detectors • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion foil size relative mass Then we can calculate Nyield and finally : Number of neutrons in peak Avogadro´s number Evaluation process: Irradiation→HPGe→Deimos→Yield →Corrections→Cross-section

  9. Neutron sources • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, Uppsala • - Conclusion Graphitestopper Beam-line Samples Li-target Blue Hall, Uppsala Quasi-monoenergetic neutron source Neutron source on cyclotron U-120M NPI ASCR Řež: Energy range 10 –37 MeV,neutron intensity ~ 108 n.cm-2.s-1 TSL Uppsala: Energy range 20 – 180 MeV, neutron intensity ~ 105 n.cm-2. s-1

  10. Neutron spectra from p/Li source in NPI • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, Uppsala • - Conclusion uncertainty in spectrum determination - 10% proton beams of energies 20, 25, 32.5, 37 MeV were used

  11. Background subraction • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion background contribution was determined by folding of the neutron source spectrum and calculated cross-sections (TALYS 1.0) we calculated ratio between production in neutron peak and total productionand with this ration we multiplied the yields to subtract background production

  12. TALYS 1.0 – nuclear models • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion ld1 - Fermi model ld2 – backshifted Fermi model ld3 - superfluid model ld4 - Goriely table ld5 - Hilairey table models with different nuclear level density change the shape of cross-section dependency on neutron energy

  13. TALYS 1.0 – nuclear models Difference between cross-sections models with different nuclear level density and default Fermi model, reaction 209Bi(n,3n)207Bi • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion it is necessary to analyze influence of this faktor on determination of radioactive nuclei number in the future

  14. Uncertainty analysis • HPGe detector calibration uncertainty: less than 3% • Gauss-fit of the gamma peaks: >1% (usually less • than 10%) • spectroscopic corrections uncertainty: less than 1% • neutron spectra determination: 10% • neutron beam intensity determination: 5% at NPI, 10%at TSL • uncertainty of background subtraction- will be analyzedin the future • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  15. Experiments in NPI • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • four measurements in years 2008-2009 • proton beam energies 20, 25 MeV (August 2008), 32.5 (April 2009) and 37 MeV (Mai 2009) • irradiation time about 20 h.,irradiated foils: Ni, Zn, Bi, Cu, In, Al, Au, Ta, Fe and I • the sample distances from the lithium target – 11 to 16 cm

  16. Experiments in TSL • proton beam energies 25, 50, 100 MeV (June 2008); 62, 70, 80, and 93 MeV(February 2010) • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • irradiation time about • 8 h.,irradiated foils: • Au, Bi, In, Al, Ta, Co, • Y and I

  17. NPI and TSL results Comparison of cross-section reaction (n,2n) 197Au with EXFOR and TALYS • Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • Comparison • NPI, TSL • - Conclusion

  18. NPI and TSL results Comparison of cross-section reaction (n,4n) 194Au with EXFOR and TALYS • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  19. NPI and TSL results Comparison of cross-section reaction (n,6n) 192Au with EXFOR and TALYS • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  20. NPI and TSL results Comparison of cross-section reaction (n,4n) 206Bi with EXFOR and TALYS • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  21. Conclusion • eleven cross-section measurements were performed in years 2008-2010 • energy region from 17 MeV to 94 MeV was covered • good agreement between our data and other experimental data and code TALYS was observed in many cases • previous measurements in NPI and TSL are now completely processed and were published at scientific workshop EFNUDAT – Slow and Resonance neutrons in 2009 in Budapest and at International Conference on Nuclear Data for Science and Technology in April 2010 in South Korea • only preliminary cross-section data from the last measurement are presented • by the means of this new measurement we covered energy range 59-89 MeV, where no data were available so far • - Motivation • Detection of • neutrons • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion Thanks for attention

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