Instrument Performance of the Lunar-VISE Gamma Ray Neutron Spectrometer

The Lunar Vulkan Imaging and Spectroscopy Explorer (Lunar-VISE) mission consists of a suite of instruments to explore the Gruithuisen Domes located in the northern lunar hemisphere. One of instruments to be mounted on a rover is a gamma ray and neutron spectrometer. The spectrometer uses a $\mathrm{Li}-6$ enriched $\mathrm{Cs}_{2}{ }^{6} \mathrm{LiYCl}_{6}$ (CLYC) scintillator to detect both gamma rays and neutrons. The design of the instrument balances mass, power and performance to obtain high-quality gamma ray spectroscopy with a $6.4-\mathrm{cm}$ diameter CLYC crystal encased in a gadolinium shell to veto thermal neutrons. To obtain a measure of the thermal neutron albedo to assess the concentration of local neutron moderating materials, a $5.0-\mathrm{cm}$ diameter CLYC without a gadolinium shell is used to measure the full spectral neutron flux. To minimize power, the system design utilizes a multi-channel configuration to provide pulse shape analysis and spectroscopy using a single readout channel. The instrument design is completed, and the sensor heads are being assembled and tested to meet the design requirements.