epithermal neutron

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ep·i·ther·mal neu·tron

a neutron having an energy in the range immediately above the thermal range, that is, having an energy between a few hundredths and approximately 100 ev.
References in periodicals archive ?
p] for epithermal neutron capture in medium-to-heavy nuclei.
Sensors and instruments on the surface platform will also be used to study the subsurface water distribution at the landing site, to investigate the exchange of volatiles between the atmosphere and the surface, to monitor the radiation environment and compare it with measurements made with the radiation dosimeter on the FREND [Fine Resolution Epithermal Neutron Detector] instrument (on the ExoMars 2016 Trace Gas Orbiter), and to carry out geophysical investigations of the planet's internal structure.
A drop in the count of epithermal neutrons and an increase in the number of cool neutrons would indicate the presence of hydrogen in the lunar "soil" (regolith).