Preliminary results on a novel Si(Li) gamma ray detector stack for future Mars missions

The authors present Monte Carlo analysis and preliminary experimental data on a novel lithium-drifted silicon detector stack for gamma-ray spectroscopy instrumentation in future Mars surface landers and other planetary missions. The Monte Carlo analysis shows full energy photopeaks even in the range of approximately 100 keV to 2 MeV where, in Si, Compton scattering dominates the absorption processes. Laboratory data are shown for an experimental detector stack of four planar Si(Li) devices each 5 mm thick with an active area 2 cm in diameter. All the experimental data were collected with maximum temperature of the stack 175 K. Background reduction is achieved by utilizing the detector of the stack closest to the source in anticoincidence. The authors present a comparison of experimental data from the stack with the Monte Carlo model for /sup 137/Cs (662 keV). Experimental stack data are shown for multiple peaks at 511 keV (/sup 22/Na) and 662 keV (/sup 137/Cs). The peaks are clearly resolved (FWHM approximately 10 keV), and are compared with the resolution obtained using NaI device (FWHM approximately 50 keV).<>