An investigation of the effects of x-radiation on the electrical properties of mica
MacGregor, Joel Edward
Money, Lloyd J.
Master of Science
The purpose of this investigation was to determine experimentally any changes in the dielectric constant and conductivity of mica during and after exposure to X-rays. Several high Quality mica condensers were used for test purposes. Measurements of capacitance and conductance of the test condensers were obtained by use of a capacity bridge. These measurements were made before, during, and after exposure of each test condenser to X-rays. Change in capacitance and change in conductance of each test condenser were plotted against time. Experiments were also conducted to determine the change in capacitance and conductance due solely to the increase in temperature of the test condenser during radiation. The net change due to the effects of X-radiation alone was determined by subtracting that change caused by temperature increase from the gross change observed in the radiation tests. Additional measurements were made to determine the effect of variation of X-ray tube voltage and current on the observed changes in capacitance and conductance. The results of these experiments indicate that there is a definite measurable increase in the dielectric constant and the conductivity of mica which Is subjected to X-radiation. Part of this change is due to temperature increase, but a sizable part of the gross change can be attributed to X-ray effects other than heating. After cessation of radiation, both capacitance and conductance were found to decrease at a relatively slow rate toward their original values. lo permanent change in either the dielectric constant or the conductivity resulted from X-radiation of the test condensers. For X-ray tube voltage of 50 kv and tube current of 15 ma, the maximum observed changes in capacitance due solely to the effect of the X-rays averaged about 0.4 mmf and the maximum observed changes in conductance due solely to X-radiation averaged about 100 x 10 -11 mhos. This corresponded to a change iii bioelectric constant of 0.08 per cent and a change in conductivity of 10 per cent. Change in capacitance and conductance of the test condensers was found to depend on both X-ray tube voltage and current; however, the amount of data taken was insufficient to definitely determine the relative influence of tube voltage and tube current on the magnitudes of change encountered.