Measurement of the $^{236}$U$(n,f)$ Cross Section with the MicroMegas Detector

Abstract

The ISOLDE radioactive beam facility is the dedicated CERN installation for the production and acceleration of radioactive nuclei. Exotic nuclei of most chemical elements are available for the study of nuclear structure, nuclear astrophysics, fundamental symmetries and atomic physics, as well as for applications in condensed matter and life sciences. In order to broaden the scientific opportunities beyond the reach of the present facility, the ongoing HIE-ISOLDE (High Intensity and Energy) project provides major improvements in energy range, beam intensity and beam quality. A major element of the project is the increase of the final energy of the post-accelerated beams to 10 MeV/u throughout the periodic table. Physics with post-accelerated beams at 4 MeV/u has started this autumn. The increase in energy up to 10 MeV/u is fully funded and it will be implemented at the rate of one cryo-module per year reaching 10 MeV/u for A/q = 4.5 at the start of 2018. In this contribution, a description of the ISOLDE facility including some highlights will be discussed. The present status of the HIE-ISOLDE project will be described as well as the first experiment realised this year.

Measurement of the 236U(n,f) cross-section between 4 and 10 MeV with Micromegas detectors

“…Finally, a 235 U target was used, as a very sensitive tool to low energy neutron background. The experimental setup is described in more detail in [8], while a photo of the target assembly can be seen in Fig. 1.…”

“…An additional correction required to the FF counts, is a correction for the FF which are lost under the alpha peak and need to be taken into account. This correction ( f amp.cut ) is estimated by FLUKA [11,12] simulations using the GEF code [13] as fission event generator [8]. Typ-ically the f amp.cut values deduced for the different targets were of the order of 5%.…”

“…The quasi-monoenergetic neutron beams were produced via the 2 H(d,n) 3 He reaction at several neutron energies in the energy range 4 -10 MeV. A first exploratory experiment was previously performed [8], in order to establish the analysis methodology and new measurements were performed in this energy range.…”