On the possibility of using 235U(n,f) resonance reactions for localized pulsed neutrons beams monitoring in the epithermal energy region at the ISIS spallation source

Localized neutron beam monitors are very useful for applications related to the measurement of the so called single event effects (SEE) in electronic devices, especially at spallation neutron sources. Although the high-energy component of the spectrum typically represents a concern for SEE, nevertheless the measurement of the flux over the whole energy range is also desirable. Indeed, the possibility of measuring the spectral neutron fluence rate is instrumental for a reliable and complete assessment of the robustness of the irradiated devices to SEE induced by neutron fields that close resemble the atmospheric one, that extends up to 109 eV energy. In this paper, an approach to monitor the epithermal energy region of the pulsed neutrons beams available at the ISIS spallation neutron source is presented. It is based on the exploitation of the resonances of the 235U(n,f) reaction and the detection of the fission fragments by means of single crystal diamonds. These explorative tests are intended as complementary to the use of diamond detectors for localized fast neutron beams monitoring and the results obtained, while assessing this aspect, also show the possibility to measure the relative spectral neutron fluence rate at different energies in the electronvolt region.