Silicon carbide detectors for dosimetry and monitoring of ultra-high dose rate beams

FLASH radiotherapy, which employs ultra-high dose rate (UHDR) beams with a mean dose rate > 40 Gy/s and a total irradiation time < 200 ms to treat tumors, exhibits remarkable ability to spare healthy tissue while maintaining the same efficiency in treating tumors. However, UHDR presents challenges in dosimetry and beam monitoring, as the dosimeters recommended for conventional radiotherapy, i.e. the ionization chambers, show saturation at such high dose rates and dose delivered per pulse and hence cannot be employed for accurate dosimetry in the future clinical transition of FLASH radiotherapy. This implies the need to develop alternative techniques and dosimeters able to sustain the peculiar conditions of the UHDR beams. This study investigates the feasibility of using a new generation of Silicon Carbide (SiC) detectors for the measurement of the instantaneous dose rate of UHDR electron beams. An experimental investigation was conducted with the ElectronFLASH linac developed by the SIT Sordina company and able to accelerate 7 and 9 MeV electron pulsed beams at FLASH regimes. The signals produced in the SiC detectors were acquired and compared with the signals detected by the monitoring system currently mounted along the LINAC, i.e. two AC current transformers supplied by the Bergoz company. The main purpose of the experiment was to demonstrate the capability of the developed SiC detector to measure the single pulse duration and waveform with high time resolution and accuracy. The test was performed by using both 7 and 9 MeV electron beams and has shown promising results.