An investigation of the response of a simple design of plane-parallel chamber

This paper reports the experimental investigation of a simple design of plane-parallel electron chamber, which has very thin layers of copper (0.018 or 0.035 mm) as conducting material. Measurements comparing the prototype chambers with other ionization chambers (PTW/Markus, NACP) have been carried out, both in a 60Co gamma-ray beam and in high-energy electron beams. The results show that the Ce factors (proportional to the product of water/air stopping-power ratio and perturbation factor) for converting the in-phantom air-kerma-calibrated chamber reading to the absorbed dose to water are nearly constant for incident electron energies between 4 and 11 MeV for prototype chambers with 0.018 mm thick copper layers and between 4 and 15 MeV for chambers with 0.035 mm thick copper layers. Other aspects concerning these prototype chambers, such as polarity effect, cable effect, collecting efficiency and angular response, have also been studied and the results are presented in this paper.