A new set-up for the simultaneous measurement of neutron-induced capture and fission reactions

The measurement of the capture cross section of fissile elements, of upmost importance for the design of innovative nuclear reactors and the management of nuclear waste, involves particular difficulties related to the γ-ray background produced in the fission reactions. These difficulties are the reason why five out of the six actinide σ(n,γ) measurements in the NEA High Request Priority List are fissile isotopes. At n_TOF we have combined the Total Absorption Calorimeter capture detector with a set of three ²³⁵U loaded MicroMegas fission detectors for measuring simultaneously the two reactions: capture and fission. In a first test measurement we have succeeded in measuring simultaneously with high efficiency the ²³⁵U capture and fission cross sections, disentangling accurately the two types of reactions.