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In the context of the Gamma-Flash program, whose objective is to investigate the emission of high-energy gamma rays and neutrons during thunderstorms, a neutron detection system, based on scintillators coupled to photomultiplier tubes (PMTs), has been developed. The neutrons emitted are generated by photoproduction reactions in the atmosphere, and they have a wide range of energies, from MeV down to meV. In this work, the effects of neutron irradiation on PMTs and their power supply are investigated to assess and quantify the effects of irradiation on dark-count rate and during data acquisition. The detection system was irradiated at the ChipIr beamline at ISIS Neutron and Muon Source, Didcot, U.K. During the irradiation of power supplies, an increase in dark-count rate has been observed, whose magnitude depends on the output voltages and the experimental parameters. In the specific case of our experiment, the dark-count rate went from an average value of 0 to 40 and 120 counts per second (counts/s) at the operating voltage of 1800 and 1900 V, respectively. Even more evident are the effects during the irradiation of the PMTs; in this case, the dark-count rate reaches about 4000 counts/s, high enough to hamper the measurements. These effects, despite their relevance to data acquisition and detector performance, do not produce long-term consequences on the electronic components. Beyond the Gamma-Flash program, this research is relevant, because the use of PMTs is common in many areas of scientific research and radiation detection applications. Our results highlight the need for great care in the interpretation of results in applications where PMTs and their power supplies may be exposed to high radiation fluxes. A proper design of the experiment or shielding strategies could prevent such unwanted behavior in data acquisition.

This paper presents a Python-based algorithm, named INSCorNorm, to correct the inelastic neutron scattering (INS) spectra for both sample and container self-shielding and to normalize the experimental spectral intensity to an absolute physical scale (barn/energy unit) facilitating the comparison with computer simulations and interpretation. The algorithm is benchmarked against INS measurements of ZrH2performed on the TOSCA spectrometer at the ISIS Facility. We also apply the algorithm to the INS spectra from l-lysine, a system of broad interest in biology and medicine, and we discuss how corrected INS data provide an experimental benchmark for theoretical calculations of nuclear anisotropic displacement parameters in molecular systems. The total neutron sample cross section to use for the self-shielding corrections is discussed, as well as the best approach to derive experimentally the cross section at the VESUVIO spectrometer, together with the experimental value of the hydrogen nuclear mean kinetic energy, ⟨Ek⟩. The algorithm is made available to the neutron user community within the MANTID software.