Measurement of the ²³⁶U(n,f) cross section at fast neutron energies with Micromegas Detectors

Abstract

In the present work, the measurement of the 236U(n,f) cross section was performed, with reference to the 238U(n,f) reaction. The measurements took place at the neutron beam facility of the National Centre for Scientific Research "Demokritos" (Greece) and the quasi-monoenergetic neutron beams were produced via the 2H(d,n)3He reaction in the energy range 4–10 MeV. Five actinide targets (two 236U, two 238U and one 235U) and the corresponding Micromegas detectors for the detection of the fission fragments were used. Detailed Monte Carlo simulations were performed, on one hand for the study of the neutron flux and energy distribution at the position of each target, and on the other hand for the study of the energy deposition of the fission fragments in the active volume of the detector. The mass and homogeneity of the actinide targets were experimentally determined via alpha spectroscopy and the Rutherford Backscattering Spectrometry, respectively. The experimental procedure, the analysis, the methodology implemented to correct for the presence of parasitic neutrons and the cross section results will be presented and discussed.

Measurement of the $$^{232}$$Th(n,f) cross section with quasi-monoenergetic neutron beams in the energy range 2–18 MeV

“…The scattering of the main neutron beam in the experimental area is not included in the simulations. This scattering is expected to slightly increase the low energy part of the simulations [33]. Even a low parasitic flux at low energies can cause a huge effect in the 235 U sample (due to the high cross section at low energies), leaving at the same time the corrections for the 232 Th and 238 U samples unaltered.…”

Measurement of the $^{236}$U fission cross section and angular distributions of fragments from fission of $^{235}$U and $^{236}$U in neutron energy range of 0.3-500 MeV

“…The data available in the literature on the neutroninduced fission cross section of the 236 U were obtained both using beams of quasi-monoenergetic neutrons formed at Van de Graaf accelerators [2][3][4][5][6][7] and neutron sources with a continuous spectrum using the timeof-flight method [8][9][10][11][12]. Most of these data relate to neutrons with energies below 40 MeV, and only in two works [9,11] the incident neutron energy range was expanded to 400 MeV and 200 MeV, respectively.…”

“…In [7], measurements were carried out using Micromegas detectors, whereas in the rest of these studies, the registration of fission fragments was carried out by multi-section ionization chambers. At the same time, the remark of authors in ref.…”