STUDIES ON THE POCKET DOSIMETER FOR PREVENTION OF RADIATION INJURIES : 2. FILMBADGE DOSIMETRY AND PHOTOGRAPHIC ACTION OF X-RAYS

For prevention of radiation injuries it is important that the operator is constantly and accurately aware of the radiation dose to which he is exposed. In order to measure the radiation dose he is receiving it is most advantageous for the operator to carry the measuring instrument on himself. Pocket dosimeter and film badge, were made for this purpose and are being quiteextensively used. From the nature of its mechanism for radiation test its wavelength dependence is unavoidable, as we have already reported in the previous paper. In the present report we havew discussed the wavelength dependence of film emulsion and described a part of the experiments performed. In blackening of the photographic emulsion of film the action of secondary electorons such as Compton electron, photoelectron, classical scattering ( Thomson sattering ) augment that of the incident ray. The yield of secondary electrons depends moreover on hardness of the incident radiation, thus, the optical density dose not correspond with the roentgen unit which is based on the energy absorption by the air even the hardness of radiation quality and optical density vary on the linear part of sensitivity of the film. According to our experiments with constant exposure ( under 0.5r irradiation ) the film blackening degree was 0.87 at 80kVp, and 0.63at 160kVp, whereas the radiation quantity necessary to te optical density of 0.7 at 80kVp was found to be 0.40r, and at 160kVp it was 0.64r (Sakura film under certain developing conditions ). The authors are hoping to make improvements on the accuracy with which the radiation quantity received by the operator is mesured, as determined by the film blackening method.