AN INVESTIGATION OF THE RESPONSE OF A SIMPLE DESIGN OF PLANE-PARALLELCHAMBER

This paper reports the experimental investigation of a simple design o f plane-parallel electron chamber, which has very thin layers of coppe r (0.018 or 0.035 mm) as conducting material. Measurements comparing t he prototype chambers with other ionization chambers (PTW/Markus, NACP ) have been carried out, both in a Co-60 gamma-ray beam and in high-en ergy electron beams. The results show that the C-e factors (proportion al to the product of water/air stopping-power ratio and perturbation f actor) for converting the in-phantom air-kerma-calibrated chamber read ing to the absorbed dose to water are nearly constant for incident ele ctron 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 0.03 5 mm thick copper layers. Other aspects concerning these prototype cha mbers, such as polarity effect, cable effect, collecting efficiency an d angular response, have also been studied and the results are present ed in this paper.