A customized parallel plate radiation sensor for evaluation of ionization collection efficiency

Radiation sensors play an important role in radiation therapy. In this paper, a customized parallel plate radiation sensor with thick and large-area electrodes was designed and made as a precursor to investigating novel materials as a substitute for conventional metallic conducting plates. Measurements by varying the bias voltages, electrode separations, doses and angles of the incident beam were carried out to characterize the sensor. Saturation characteristic of the sensor with different electrode separations and doses was investigated using the Varian Clinac 21 EX medical linear accelerator. Our prototype sensor displayed excellent linear response to dose up to 600 monitor units (MU) and showed an accurate response to the oblique incident beam with a small field size of 1 /spl times/ 1 cm/sup 2/. The sensor was tested to be suitable in the study on the ionization collection efficiencies for different materials.