Measurement of the 6Li(n,α)t neutron standard cross-section at the GELINA facility

Abstract

The 6Li(n,α)t reaction cross-section is an established standard due to its relatively high cross-section as well as its high Q-value. However, it is only considered a neutron standard up to 1 MeV, because in the neutron energy region 1–3 MeV there exist discrepancies of several per cents between recent measurements [1, 2] and evaluated data files [3]. It has been speculated [4] that neglecting of the particle leaking effect might be part of the explanation why there is a disagreement in this region. Based on R-matrix calculations, in the region around 2 MeV, one also expects three excitation levels of 7Li to significantly influence the cross section [5]. In order to resolve these discrepancies, we perform measurements at the GELINA facility at JRC-Geel with two Frisch-gridded ionisation chambers. The 6Li(n,α)t cross section is measured relative to the 235U(n,f) standard. In order to solve previous encountered problems [6], the setup has been modified and moved to a new flight path station. In this proceeding we show that several problems have been eliminated and discuss possible solutions to newly arisen problems, due to the changed experimental conditions. Preliminary results from new data taken during 2016 with the updated setup are presented.