Current and Future Instrument Designs for Monitoring Photon Radiations in Terms of Ambient and Directional Dose Equivalent

Abstract

The photon response characteristics of a wide range of currently used energy compensated Geiger-Müller detectors and ion chamber radiological protection instruments have been investigated in terms of the quantities ambient and directional dose equivalent. This investigation showed that many of the older designs of energy compensated Geiger-Müller detectors have better characteristics for the measurement of the quantity ambient dose equivalent than for that of the original design quantity of exposure. More recent detectors, which have been designed to give a better measurement of exposure, are correspondingly less suited to the measurement of ambient dose equivalent. The polar responses of the detectors tested were on the whole satisfactory in that the respose for photon energies greater than 60 keV was approximately isotropic. The ion chamber instruments, which normally have better exposure characteristics for the measurements of exposure than the energy compensated Geiger-Müller detectors, were also investigated. Data are presented for both the original responses and responses after modification of the Eberline RO2 ionisation chamber survey instrument.