LABORATORI NAZIONALI DI LEGNARO
A new MicroMegas detector [1], based on the innovative Microbulk technology, especially developed at CERN [2], was used for the first time for fission cross section measurements. In the present work, the case of the 237Np(n,f) cross section with reference to the standard 238U(n,f) reaction will be presented. The incident monoenergetic neutron beams with energies in the range 4-6 MeV were produced via the 2H(d,n) reaction at the neutron beam facility of the Institute of Nuclear Physics at the NCSR ``Demokritos''. Four actinide targets (237Np, two 238U and 235U) and the corresponding MicroMegas detectors were assembled in an especially made chamber full of Ar/CO2 at a proportion 80/20 and around atmospheric pressure. Monte-Carlo simulations were performed with the code MCNP5 [3] implementing the neutron beam setup and the MicroMegas assembly in order to determine the neutron flux at the position of each target. Additional simulations with FLUKA [4] were performed, studying the energy deposition of the fission fragments in the active area of the detector, in order to accurately estimate the efficiency. Good discrimination of the heavy and light mass peaks of the fission fragments was achieved. The cross section results are in agreement with previous data and will be presented and discussed.

DATA: 04-10-2013