Measurement of neutron and proton-induced background in germanium gamma-ray spectrometers for use in a space environment

Particle-induced background in germanium spectrometers used for astrophysical and remote sensing measurement in a space environment provides an important limitation to the ultimate instrument sensitivity. To aid future experimental design and interpretation, laboratory exposure of typical sensors to known fluences of slow and fast neutrons and energetic protons is carried out to predict the line and continuum background components. Fast neutron elastic scatter is found to be the chief source of background below 100 keV for an unshielded detector inside a heavy spacecraft. At higher energies, comparable contributions are identified from neutron inelastic scattering and neutron- and proton-induced radioactivity. Radiation damage to an n-type high purity Ge detector caused broadening in resolution by a factor of 1.8 after subjection to 1.2*1010 protons of 600 MeV.