Radiation stability of high pressure xenon gamma-ray spectrometers

Spectrometric characteristics of High Pressure Xenon (HPXe) gamma-ray spectrometer “Ksenia” was studied during operation of this instrument onboard the orbital station “MIR”. The energy resolution of this spectrometer is 3.5±0.5% at E_γ=511 keV and stable during period from May 1990 till May 1997. The position of 511 keV gamma line is also stable (±1 channel or ±4 keV). The total number of trapped in radiation belt particles passing through the detector is 5·10⁹. The number of neutrons of atmospheric albino is 2·10¹⁰. No activated gamma-lines were found during the flight. After intensive activation (fluence of about 1.5·10¹⁰ neutrons) of a cylindrical HPXe spectrometer with a volume of Xe of about 6 liters few activated gamma-lines were registrated: E_γ=164 keV, T _½=11.92 from ¹³¹Xe_m; Eγ=236 keV, T_½=8.89 days from ¹²⁹Xe, and Eγ=847 keV, T_½=2.56 hours from ⁵⁶Mn. The intensity of these lines is not large so it is possible to operate HPXe spectrometers even after intense irradiation