Statistical Model Analysis of (n, α) Cross Sections for 4.0-6.5 MeV Neutrons

The statistical model based on the Weisskopf-Ewing theory and constant nuclear temperature approximation is used for systematical analysis of the 4.0-6.5 MeV neutron induced (n, α) reaction cross sections. The α-clusterization effect was considered in the (n, α) cross sections. A certain dependence of the (n, α) cross sections on the relative neutron excess parameter of the target nuclei was observed. The systematic regularity of the (n, α) cross sections behaviour is useful to estimate the same reaction cross sections for unstable isotopes. The results of our analysis can be used for nuclear astrophysical calculations such as helium burning and possible branching in the s-process

Statistical Model Analysis of (

The statistical model based on the Weisskopf-Ewing theory and constant nuclear temperature approximation is used for systematical analysis of the 4.0-6.5 MeV neutron induced (n, α) reaction cross sections. The α-clusterization effect was considered in the (n, α) cross sections. A certain dependence of the (n, α) cross sections on the relative neutron excess parameter of the target nuclei was observed. The systematic regularity of the (n, α) cross sections behaviour is useful to estimate the same reaction cross sections for unstable isotopes. The results of our analysis can be used for nuclear astrophysical calculations such as helium burning and possible branching in the s-process

Detection of fast neutrons with the pixel detector Timepix3

We examined the response of the pixel detector Timepix3 with silicon sensor to well-defined fast neutron fields. Part of the pixel detector silicon sensor was additionally equipped with a neutron mask of distinct converter regions. The mask consists of separate thermal and fast neutron regions using 6LiF and hydrogen (plastic) converters, respectively. Measurements were performed with mono-energetic fast neutrons produced at D-D and D-T sources from a Van de Graaff accelerator and a neutron generator, respectively. Data were collected with low background including measurements with moderator material to provide a thermalized neutron component. All the signals produced in the detector were analyzed and decomposed in terms of the spectral -tracking response of the pixel detector. The effect of the fast and thermal components of the neutron converter were determined and compared with direct interactions in the silicon sensor which are significant and can be dominant for fast neutrons. We identify and classify the neutron-induced tracks in terms of the broad-type particle-event track classes. A partial overlap is unavoidable with tracks from direct detection of other radiations in particular protons and low-energy light ions as well as X rays. This will limit the neutron-event discrimination in mixed-radiation fields. The detection response according sensor-mask region was examined and calibrated for the investigated neutron fields. The neutron detection efficiency is selectively derived for the detector particle-event classes. This approach enables to enhance the neutron-discrimination and suppress background and unwanted events. This work enables to extend the response matrix of the detector for broad-type radiations to include neutrons both fast and thermal. The results serve to enhance the sensitivity and determine the neutron component in unknown and mixed-radiation fields such as outer space and particle radiotherapy environments.Web of Science181art. no. P0100

Cross section of the

Accurate cross section of the 232Th(n, f) reaction are demanded in the design of advanced nuclear systems and in the development of fission theory. However, the existing measurement data are relatively sparse comparing with those of the 238U(n, f) reaction, with big uncertainties and obvious discrepancies. Furthermore, analysis shows that systematic deviations exist between the results measured with mono-energetic neutron sources and white neutron sources, which is the main reason for the differences among different evaluation libraries. This work is dedicated to the clarification of this discrepancy. Based on mono-energetic d-d neutron sources and using back-to-back Th/238U samples, cross section of the 232Th(n, f) reaction were measured at 12 energies in the 4.2–11.5 MeV region. Elaborated measures were taken in the measurement procedure including the exchange of the forward and the backward direction of the samples, as well as in the data processing containing the correction of interference fission counts from low-energy neutrons and the detailed Monte Carlo simulations for the determination of detection efficiencies for fission events. In addition, theoretical analysis was also performed using TALYS-1.9 and UNF codes. The present results agree with existing measurement data using white neutron sources, showing that previous cross section of the 232Th(n, f) reaction measured using mono-energetic neutron sources are systematically overestimated on average. The present results are in accordance with the latest measurement data of Michalopoulou et al., which is helpful in the improvement of nuclear data evaluations of the 232Th(n, f) reaction