CALCULATED RESPONSE OF AIR-WALL DOSIMETERS OR GEIGER-MUELLER TUBES TO MONOENERGETIC PHOTONS BETWEEN 1 AND 10 MEV
NAVAL RADIOLOGICAL DEFENSE LAB SAN FRANCISCO CA
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The question of registering dose from weapon and reactor photons of 2 to 10 MeV energy has led to a study of the capability of conventional dosimeters and GeigerMueller tubes to respond accurately to these energies. The cases are analyzed of 116-in. and 18-in. air wall dosimeters under bombardment with these high energy photons, and also under bombardment with these photons plus the electron flux density coming from an air absorber of sufficient thickness to ensure primary to secondary radiation equilibrium. Dosimeters of two different wall thicknesses, 2.5 and 5 grams-sq cm, are studied, the latter of which can reach primary-tosecondary equilibrium under 10 MeV photons and, of course, under all lower energies. The attenuation of the primary flux density is relatively small even at the larger thickness. The results given in tables and a graph show that the thin wall dosimeters will give a distorted indication of dose at higher energies. The chamber with 5 grams per square centimeter wall responds in constant ratio to the response of the ideal air wall chamber for photons from 1 to 10 MeV and can therefore be used under all conditions for a register of dose.
- Nuclear Instrumentation