Лаборатория нейтронной физики им. И.М. Франка

Отделение ядерной физики

Руководитель – Е.В. Лычагин

Дата и время: среда, 6 ноября 2019 г., в 10:00

Место: Конференц-зал (3й этаж), Лаборатория нейтронной физики им. И.М. Франка

Тема семинара: «Neutron-induced cross-section measurements by activation technique and gamma-ray spectrometry in the energy range up to 20 MeV. Compilation of experimental nuclear reaction data in EXFOR database»

Докладчик: Валентина Семкова (Институт ядерных исследований и ядерной энергетики БАН, София, Болгария)

Аннотация:

Neutron-induced activation cross-section measurements on Ni, Co, Zr, Mo, Pb, W and 241Am isotopes in the energy range from the threshold up to 20 MeV will be presented. The irradiations were carried out at the Van de Graaff accelerator, Joint Research Centre-Geel, Belgium; CV28 compact cyclotron at Physikalisch-Technische Bundesanstalt, Braunschweig, Germany; and MCG-20E cyclotron at ATOMKI, Debrecen, Hungary. Neutrons with quasi-monoenergetic and broad energy distributions were produced via the 2H(d,n)3He, 3H(d,n)4He, 3H(p,n)4He, and 9Be(d,n)10B reactions. The neutron flux energy distributions were characterized by time-of-flight method, PHR spectrometer and spectral index method based on activation reactions with different thresholds. Samples with different isotopic compositions were used to determine the cross sections for reactions leading to the same reaction product. The radioactivity of the reaction products in the samples were determined by gamma-ray spectrometry using HPGe detector. Both analytical and Monte Carlo methods were applied to determine the detectors’ efficiencies using standard sources calibration measurements. An important consideration for the fitting procedures is that correlations between efficiencies at different energies are introduced and needs to be taken into account in uncertainty analysis. Calculation of the detector efficiency variance-covariance matrix will be presented. Special attention was paid to the calculation and uncertainty propagation of true coincidence summing correction applied in gamma spectrometry at closed geometry. Results from the measurements with different sample geometries and isotopic compositions; incident neutron spectrum; reaction product half-live (from few seconds to several years), total and isomeric level cross-sections etc. will be presented.
The EXFOR library is a global repository of experimental nuclear reaction data and associated information that has been systematically collected expanded and developed as a product of the international collaboration of Nuclear Reaction Data Centres (NRDC). The EXFOR database presently contains integral, differential and partial cross-sections including angular distributions, secondary particle spectra, polarization data, resonance parameters, nu-bar, fission product yields, reaction rates etc. for reactions induced by neutrons, charged-particles, and photons with incident energies up to 1 GeV. In addition to the EXFOR general purpose library data related to specific applications provided by IAEA Nuclear Data Section will be presented as well.