Measurement of radiation-induced current through a SiC Schottky barrier diode in a clinical carbon beam cancer therapy field

Real-time physical dose evaluation was performed using radiation-tolerant SiC Schottky barrier diodes (SBDs). The radiation-induced current (RIC) generated in the SBD was measured under clinical carbon beam irradiation. A SiC SBD semiconductor detector (epitaxial layer, 69 mu m thick; impurity concentration, 9.1 x 1014 cm-3; electrodes, 1 mm2) was used. The SiC SBD was irradiated with carbon ions having energy of 290 MeV/n at a maximum flux of therapeutic intensity (1 x 109 particles per second) at the Gunma University Heavy Ion Medical Center. The transition of the RIC value at any depth point in the Bragg curve was evaluated by changing the thickness of a water tank placed in front of the SiC SBD. The RIC from the SiC SBD was obtained with an applied voltage of up to 100 V for each moderator thickness. The physical dose distribution was also measured using a commercial ionization chamber. The Bragg peak was determined from the RIC distribution, and the transition was similar to that observed using the commercial ionization chamber.