  Tl$_2$LiYCl$_6$:Ce (TLYC) is a new dual-detection elpasolite scintillator
that can detect and distinguish between gamma rays and neutrons using
pulse-shape discrimination (PSD). It has a higher density and Z-number than the
more mature and well-known elpasolite Cs$_2$LiYCl$_6$:Ce (CLYC), causing it to
have a significantly better gamma-ray stopping power. These properties make
TLYC an attractive alternative to CLYC for resource-constrained applications
where size and weight are important, such as space or national security
applications. Such applications may be subjected to a wide range of
temperatures, and therefore TLYC's performance was characterized for the first
time over a temperature range of -20$^{\circ}$C to +50$^{\circ}$C in
10$^{\circ}$C increments. TLYC's thermal response effects on light-output
linearity with energy, gamma-ray photopeak energy resolution, detected neutron
energy, pulse shapes, and figure of merit is analyzed and reported. The light
output of TLYC was found to be linear with energy over the tested temperature
range and was observed to decrease with increasing temperature. The decay time
of the scintillation light output was observed to decrease with decreasing
temperature at short times, leading to a decreasing PSD figure of merit. The
gamma-ray photopeak energy resolution was also observed to degrade with
decreasing temperature, due to an asymmetric broadening of the photopeak at low
temperatures.
