title: Cavity ionisation theory applied to the design of a maximum permissible fluence instrument.
abstract: The maximun permissible fluence is proposed as a practical concept in radiological monitoring of photon fields. It is virtually this concept that is used for monitoring neutron fields. The practicability of designing instruments with a required response function over a large energy range is examined. Cavity isonisation theory is employed to examine the effect of gas filling, wall material, chamber size and wall thickness on response function and the optimum parameters for the design of an ionisation chamber are thus identified. An experimental chamber of parameters close to the optimum has been constructed and its response compared with the response calculated from cavity ionisation theory. It is concluded that it is possible to design an instrument, the energy response of which follows the maximum permissible fluence. The approach and data in this paper will facilitate any necessary design changes which would arise in the event of national regulation being modified.
mesh_terms: D004601:Elementary Particles; D008433:Mathematics; D011834:Radiation Monitoring / Q000295:instrumentation*