Measurements of cross-sections of neutron threshold reactions and their usage in high energy neutron measurements Ondřej Svoboda 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

Outline Motivation - Energy plus Transmutation projectMotivation - Energy plus Transmutation project Cross-section measurementsCross-section measurements TSL Uppsala experimentTSL Uppsala experiment Experiments on Cyclotron in ŘežExperiments on Cyclotron in Řež ConclusionConclusion - Motivation:E+T project - Cross - section measurements - TSL Uppsala - Cyclotron Řež - Conclusion

Motivation - Energy plus Transmutation Main aim of the E+T - study of transmutation of FP and HA by spallation neutronsMain aim of the E+T - study of transmutation of FP and HA by spallation neutrons We are involved in the project for 10 yearsWe are involved in the project for 10 years Our tasks:Our tasks:  study of neutron production in thick, heavy target with fissionable blanket irradiated by light ions in GeV range  perform relevant Monte-Carlo simulations  make comparisons between experimental data and simulations - Motivation:E+T project Introduction Setup Detection of neutrons Evaluation Yield to neutron flux - Cross - section measurements - TSL Uppsala - Cyclotron Řež - Conclusion

Energy plus Transmutation - setup - Motivation:E+T project Introduction Setup Detection of neutrons Evaluation Yield to neutron flux - Cross - section measurements - TSL Uppsala - Cyclotron Řež - Conclusion

Detection of high energy neutrons AlAuBiCoIn Ta Reaction E thresh [MeV] Half-life 197 Au (n,2n) 196 Au d 197 Au (n,3n) 195 Au d d 197 Au (n,4n) 194 Au h 197 Au (n,5n) 193 Au h 197 Au (n,6n) 192 Au h 197 Au (n,7n) 191 Au h - Motivation:E+T project Introduction Setup Detection of neutrons Evaluation Yield to neutron flux - Cross - section measurements - TSL Uppsala - Cyclotron Řež - Conclusion

Activation-detector evaluation - decay during cooling, irradiation - unequable irradiation - coincidences - non point-like emitters - detector dead time - detector efficiency - self-absorption - Motivation:E+T project Introduction Setup Detection of neutrons Evaluation Yield to neutron flux - Cross - section measurements - TSL Uppsala - Cyclotron Řež - Conclusion

Yield to neutron flux problem To find the Φ(E) a Fredholm equation must be solved:To find the Φ(E) a Fredholm equation must be solved: - Motivation:E+T project Introduction Setup Detection of neutrons Evaluation Yield to neutron flux - Cross - section measurements - TSL Uppsala - Cyclotron Řež - Conclusion We would like to know! (Up to know only MCNPX simulation) Not known for most of the observed isotopes! Measured

Requirements for  -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 –  and X-rays detectors - knowledge about the corrections on beam, self-absorption, non-point like emitters… Cross-section measurements - Motivation:E+T project - Cross - section measurements Requirements - TSL Uppsala - Cyclotron Řež - Conclusion Then we can calculate N yield and finally : Evaluation process is the same as shown before: Irradiation HPGe Deimos Corrections Yield Cross-sections

TSL Uppsala - Motivation:E+T project - Cross - section measurements - TSL Uppsala Introduction Experiment - Cyclotron Řež - Conclusion - Protons on Li target or spallation source - Neutrons with energies MeV - Well known beam and neutr. spectrum June 2008, supported by EFNUDAT program

TSL Uppsala experiments – June Motivation:E+T project - Cross - section measurements - TSL Uppsala Introduction Experiment - Cyclotron Řež - Conclusion - 3 irradiations on the Li target – 25, 50, and 100 MeV p+ - one irradiation on the ANITA spallation target – 180 MeV p+ - 8 hours each, than always one day of spectroscopic measurements Au, Al, Bi, In, Ta, I samples Finished yields evaluation, waiting on the beam data...completed after summer break

Cyclotron Řež - Motivation:E+T project - Cross - section measurements - TSL Uppsala - Cyclotron Řež Introduction Experiments - Conclusion -Up to now 2 experiments: 20 and 25 MeV - Au, Al, Bi, In, Ta, I, Ni, Fe, Mg, Zn -next irradiations planed on October Protons on Li target -Neutrons with energies MeV - Good intensities - Well equipped spectroscopy laboratory (NSD-NPI)

Cyclotron Řež experiments - Motivation:E+T project - Cross - section measurements - TSL Uppsala - Cyclotron Řež Introduction Experiments - Conclusion Tentative data! Evaluation not yet ready… Number of neutrons in peak

Conclusion –Uppsala and Řež cross-section measurements covered wide spectrum of energies –Preliminary results shows we are close to known cross-section values –Near future – next measurements at Řež –Farther future – next measurements at Uppsala – application of the results on the E+T experiments – application of the results on the E+T experiments – publish the measured cross-sections with respect to be involved in the EXFOR library if possible – publish the measured cross-sections with respect to be involved in the EXFOR library if possible Thank you for your attention.. - Motivation:E+T project - Cross - section measurements - TSL Uppsala - Cyclotron Řež - Conclusion