  We have experimentally characterized the light-output response of a
deuterated trans-stilbene (stilbene-d12) crystal to quasi-monoenergetic
neutrons in the 0.8 to 4.4 MeV energy range. These data allowed us to perform
neutron spectroscopy measurements of a DT 14.1 MeV source and a PuBe-239 source
by unfolding the impinging neutron spectrum from the measured light-output
response. The stilbene-d12 outperforms a H1-stilbene of similar size when
comparing the shape of the unfolded spectra and the reference ones. These
results confirm the viability of non-hygroscopic stilbene-d12 crystal for
direct neutron spectroscopy without need for time-of-flight measurements. This
capability makes stilbene-d12 a well suited detector for fast-neutron
spectroscopy in many applications including nuclear reaction studies, radiation
protection, nuclear non-proliferation, and space travel.
