  A novel composite, scintillating material intended for neutron detection and
composed of small (1.5 mm) cubes of KG2-type lithium glass embedded in a matrix
of scintillating plastic has been developed in the form of a 2.2 in.-diameter,
3.1 in.-tall cylindrical prototype loaded with $\left( 5.82 \pm 0.02 \right)\%$
lithium glass by mass. The response of the material when exposed to
${}^{252}$Cf fission neutrons and various $\gamma$-ray sources has been
studied; using the charge-integration method for pulse shape discrimination,
good separation between neutron and $\gamma$-ray events is observed and
intrinsic efficiencies of $\left( 1.15 \pm 0.16 \right)\times 10^{-2}$ and
$\left( 2.28 \pm 0.21 \right)\times 10^{-4}$ for ${}^{252}$Cf fission neutrons
and ${}^{60}$Co $\gamma$ rays are obtained; an upper limit for the sensitivity
to ${}^{137}$Cs $\gamma$ rays is determined to be $< 3.70 \times 10^{-8}$. The
neutron/$\gamma$ discrimination capabilities are improved in circumstances when
a neutron capture signal in the lithium glass can be detected in coincidence
with a preceding elastic scattering event in the plastic scintillator; with
this coincidence requirement, the intrinsic efficiency of the prototype
detector for ${}^{60}$Co $\gamma$ rays is $\left( 2.42 \pm 0.61 \right)\times
10^{-6}$ while its intrinsic efficiency for unmoderated ${}^{252}$Cf fission
neutrons is $\left( 4.31 \pm 0.59 \right)\times 10^{-3}$. Through use of
subregion-integration ratios in addition to the coincidence requirement, the
efficiency for $\gamma$ rays from ${}^{60}$Co is reduced to $\left( 7.15 \pm
4.10 \right) \times 10^{-7}$ while the ${}^{252}$Cf fission neutron efficiency
becomes $\left( 2.78 \pm 0.38 \right) \times 10^{-3}$.
