A detector for X-rays and low-energy gamma rays, consisting of a chamber filled with a noble (i.e. unreactive) gas such as argon or xenon. Ionization of the gas by an X-ray or gamma-ray photon in an electrical field produces an avalanche of electrons. Since the size of the electrical pulse is proportional to the energy of the photon, the detector is able to give spectral information. The instrument can also be used as an imaging device when a wire grid arrangement is incorporated into the construction.
Subjects: Astronomy and Astrophysics.