Abstract: A radiation detector, comprising a sensitive volume filled with a counter gas; an anode and a cathode each in communication with the counter gas; a voltage supply for maintaining a potential difference between the anode and the cathode, said potential difference being less than required to cause gas discharge in the counter gas. The radiation detector further comprises a photoemissive material in communication with the sensitive volume. The photoemissive material may be provided as a coating on the cathode. The radiation detector may further comprise a controllable light source for supplying photons of a known wavelength to the photoemissive material. Electrons may be emitted by the photoemissive material in response to the provision of said photons, said electrons causing avalanche breakdown of the counter gas, indicating satisfactory operation of the radiation detector.

Abstract: A personal radiation dosemeter comprising a radiation detector means coupled to an electronic measurement circuit arranged in combination therewith to generate signals representative of an amount of radiation detected by the radiation detector. The radiation detector means is arranged to be screened from ambient light and is further provided with a light source optically coupled to the radiation detector and arranged to operate under control of a test control circuit to generate light of a wavelength which may be detected by said radiation detector. This arrangement provides, in combination with said electronic measurement circuit an integrity test for said radiation detector means.

Abstract: A personal radiation dosemeter comprising a radiation detector means coupled to an electronic measurement circuit arranged in combination therewith to generate signals representative of an amount of radiation detected by the radiation detector. The radiation detector means is arranged to be screened from ambient light and is further provided with a light source optically coupled to the radiation detector and arranged to operate under control of a test control circuit to generate light of a wavelength which may be detected by said radiation detector. This arrangement provides, in combination with said electronic measurement circuit an integrity test for said radiation detector means.