Wide Energy Range Gamma-Ray Calibration Facility

A number of radiation-related applications in space such as gamma-ray detection demands a flexible and wide-range gamma-ray source which can serve as calibrating and testing facility for gamma-ray detectors and gamma-ray sensitive devices. A dedicated wide energy range gamma-ray facility with adjustable and modular segments designed for gamma-ray detector calibration and testing was built. Gamma rays are obtained from thermal neutron capture, which is the most suitable and cost efficient way how to provide discrete gamma rays with energy above 3 MeV and of reasonable intensity. With appropriate and interchangeable targets the facility can generate gamma rays with energy up to 10 MeV. Target materials of elements with high thermal neutron capture cross-section such as chrome, iron, chlorine, nickel and titanium provide suitable spectra. As neutron source Cf-252 or Am-241-Be radionuclide sources with emission rate around 10(6) neutrons/s are used. The emitted fast neutrons are moderated by a modular interchangeable system of elements containing light materials such as graphite, water, heavy water or paraffin. Different geometries and moderator-target combinations have been tested and optimized; the best of them are presented. The facility is optimized with respect to space applications and needs by the European Space Agency (ESA). Performance of the facility is demonstrated by calibration spectra measured by HPGe and scintillator detectors (LaBr3, NaI(Tl)).