Abstract: Film badges and pocket chambers are now regarded as two essential dosime-ters with which one can estimate the amount of irradiation he has received. Strictly speaking ionization chambers are to be placed in higher rank so far as the principle of measurement of X- or γ-rays is concerned but for practical purpose film badges are preferable in cost and technique when we have a proper badge analyser.
In this paper there is reported a research on a new convenient film badge analyser based on a polarisation photometer using a half-shadow method and giving direct reading of dose in milli.roentgen units. Through some preliminary tests on polaroids it is found that “Dichrome” invented by Prof. Y. Hoshino is the only one satisfying conditions required for the present purpose.
Designs on the double polaroid and constructions of the instrument can be found in Sect. 4 and in Figs. 3, 4 and 11. The fundamental equation relating true optical density
S of a badge film and the balancing angle θ through which an analyser is to be rotated so as to get uniform brightness of the field, is given by
_??_
where
m is a parameter depending only upon the cutting direction of a polaroid plate.
Definitions of two badge scales-Soft and Hard scale (cf. Fig. 16)-are givan in Sect. 8 (1) and (2), and a quality factor a connecting these scales in Sect. 8 (4). An example of badge scales calibrated with Victoreen Survey Meter is sketched in Fig. 17.
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