A lightweight shield-detector combination for use in hard X-ray telescopes

Abstract

By coupling a simple, passive shield of tin with a thin NaI (Tl) detector the atmospheric background counting rate in the energy range 15–95 keV can be attenuated by a factor of approximately 12.5. Including the weight of the collimator, a telescope built with this combination would have a total surface density of only ∼ 3 g cm −2, allowing a sensitive area of ∼ 30 m 2 to be constructed within the normal restrictions of weight on a balloon experiment. To measure the of effectiveness of different types of shielding, the atmospheric gamma radiation was simulated using a tank of water containing radioactive sources.