A study of the dependence on wall material of the ionization produced within a cavity by high voltage radiations and an investigation of a possible method of measuring the radiation quality

Abstract

The object of this work was first to investigate, by the ionization method the dependence on the wall material of the ionization produced within chambers by high voltage-radiations of wave lengths from 0.013 A.U. to 0.5 A.U. The ionization chambers were pressed from mixtures of bakelite powder and graphite powder either with vanadium or cerium oxide. Secondly to investigate the possibility of measuring the quality of radiation by means of the ratio of ionizations in two chambers one of them is air walled and the other of higher atomic number. A study was also made of the validity of Gray's theory for calculating the ratio of ionization in such small chambers. The results of these investigations have shown that: I- Chambers moulded from the above mentioned mixtures are satisfactory electrical conductors and behave consistently in their interactions with the radiations used. The method may be useful in examining the quality of the scattered radiations from harder beams of X-rays generated at say between 400 and 1000 KV. The ratio of ionisation calculated according to Gray's theory agrees with the experimental one up to a wave length of 0.08A.U. The effective wave lengths of the X-ray beams were obtained from the complete spectral distribution of the energy and from measurement of the half value layers of the beams. It was found that in most cases it is sufficiently accurate, when considering the calculation of the ratio of ionizations in two chambers, to regard the beam as having that effective wave length corresponding to its half value layer.