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Nuclear Physics Institute, Academy of Sciences of the Czech Republic

Nuclear Physics Institute, Academy of Sciences of the Czech Republic Dzelepov Laboratory of Nuclear Problems , Joint Institute for Nuclear Research , Russia Department of Nuclear Reactors, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague.

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Nuclear Physics Institute, Academy of Sciences of the Czech Republic

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  1. Nuclear Physics Institute, Academy of Sciences of the Czech Republic Dzelepov Laboratory of Nuclear Problems, Joint Institute for Nuclear Research, Russia Department of Nuclear Reactors, Faculty of Nuclear Sciences andPhysical Engineering, Czech Technical University in Prague Studies of neutron cross-sections by activation method in Nuclear Physics Institute Řež and in The Svedberg Laboratory Uppsala and experimental determination of neutron production in spallation reactions Varna, Bulgaria16.-22.9.2013 J. Vrzalová, O. Svoboda, A. Kugler, M. Suchopár, V. Wagner collaboration Energy and Transmutation of Radioactive Waste vrzalova@ujf.cas.cz

  2. Introduction • - Motivation • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • The collaboration Energy and Transmutation of Radioactive Waste use different setups consisting of lead, natural uranium and graphite irradiated by relativistic protons and deuterons to study transmutation of radioactive materials by produced neutrons. • Activation samples are used to determine production of neutron flux in different places of experimental set-ups. • Unfortunately, the cross-sections of many reactions important for our activation detectors are missing. • To improve situation, we studied the neutron cross-sectionsusing different quasi-monoenergetic neutron sources based on proton reaction on 7Li target in NPI Řež and in The Svedberg Laboratory Uppsala.

  3. 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

  4. Motivation we would like to find! • - Motivation • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion Solving a Fredholm equation we can find Φ(E): evaluated from the experiment poor knowledge, we want to measure • the spatial distribution of neutron field inside ADS-setup can be determined with the help of Fredholm equation • due to poor knowledge for us imported neutron cross-section we carried out series of experiments devoted to their determination • we measured threshold reactions onAu, Al, Bi, In,Ta, Ti, Y commonly used for such purposes and we also studied other materials: Cu, Fe, I, Mg, Ni, Zn.

  5. Evaluation process • Motivation • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion BACKGROUND SUBTRACTION

  6. Spectroscopiccorrections • - Motivation • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion Self-absorption Detector efficiency Correction for real coincidences Square-emitter corection Dead time correction Decay during cooling Decay during irradiation Unstable irradiation • Uncertainty caused by the corrections was estimated to be less than 1% in total, except the uncertaintyfrom efficiency calibration of the detector, which is below 3 %.

  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 • 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 • 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

  9. Neutron sources • - Motivation • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, Uppsala • - Conclusion NPI ASCR Řež: Energy range 14 –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 Neutron spectra comparison

  10. Background subtraction • - Motivation • 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 1.4) we calculated ratio between production in neutron peak and total productionand with this ratio we multiplied the yields to subtract background production

  11. Uncertainty analysis • - Motivation • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • 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: 10% • uncertainty of background subtraction: 10% in the worst case (big background, big model influence)

  12. Experiments in NPI • - Motivation • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • four measurements • proton beam energies 20, 25, 32.5 and 37 MeV • 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 – from 11 cm to 16 cm

  13. Experiments in TSL • proton beam energies 50, 62, 70, 80, and 92 and 97 MeV • - Motivation • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • irradiation time about • 8 h

  14. NPI and TSL results • Motivation • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • Comparison • NPI, TSL • - Conclusion Comparison of cross-sections (n,xn) reactions on natural indium with TALYS

  15. Comparison of cross-sections (n,xn) reactions on iodine and tantalum with EXFOR, TALYS and libraries of evaluated data • - Motivation • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  16. Comparison of cross-sections (n,x) reactions on aluminium and yttrium with TALYS, EXFOR and libraries of evaluated data • - Motivation • Evaluation • Corrections • - Cross - section • measurements • - Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  17. Also with the help of our measured cross-section we can analyze neutron flux in different places of experimental set-ups consisting of lead, natural uranium and graphite irradiated by relativistic protons and deuterons(for example QUINTA – more about this setup in the talk of Mr. Furman or Mr. Wagner). - neutron flux determined with the help of method “effective cross-sections” (experiment at phasotron in JINR Dubna – 660MeV protons, massive lead target, threshold detectors were situated on the target surface). • - Motivation • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion

  18. Conclusion • - Motivation • Evaluation • Corrections • - Cross - section • measurements • -Neutron sources • - Background • subtraction • - NPI Řež • - TSL Uppsala • - Comparison • NPI, TSL • - Conclusion • ten cross-section measurements were carried out in NPI Řež and in TSL Uppsala • energy region from 17 MeV to 94 MeV was covered • we studied various materials in the form of thin foils and observed good agreement with the data in EXFOR database and also with the cross- sections calculated in deterministic code TALYS. • with the help of neutron cross-section we can analyze • neutron flux in different places of experimental set-ups • all our observed reactions you can find in journal: Nuclear Instruments • andMethods in Physics Research - Vol.726, (2013) 84-90 • some of our results are already included in EFXOR

  19. Thank you! supervisor in NPI Řež: RNDr. Vladimír Wagner, CSc. supervisor in JINR Dubna: prom. fyz. Jindřich Adam, CSc. wagner@ujf.cas.cz iadam@jinr.ru

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