  Previous work showed that the 3He(n,tp) reaction in a cell of 3He at
atmospheric pressure generated tens of far-ultraviolet photons per reacted
neutron. Here we report amplification of that signal by factors of 1000 and
more when noble gases are added to the cell. Calibrated filter-detector
measurements show that this large signal is due to noble-gas excimer emissions,
and that the nuclear reaction energy is converted to far-ultraviolet radiation
with efficiencies of up to 30%. The results have been placed on an absolute
scale through calibrations at the NIST SURF III synchrotron. They suggest
possibilities for high-efficiency neutron detectors as an alternative to
existing proportional counters.
