A High Performance Detector Based on HPHT-Diamond for Dosimetry of Ultra-High Dose-Rate Electron Beams

Accurate measurement of the dose delivered during FLASH radiotherapy remains a challenging task for assessing the so-called FLASH effect in preclinical studies. Electron beams generated by linear accelerators (LINACs) used in FLASH radiotherapy consist of microsecond pulses and are therefore characterized by instantaneous dose rates on the order of MGy/s. Diamond represents one of the most promising materials for fabricating reliable dosimeters for FLASH radiotherapy. So far, excellent results have been achieved using detectors based on high-quality single-crystal CVD diamond samples. Conversely, literature lacks solid evidence demonstrating the effectiveness of lower-quality high-pressure high-temperature (HPHT) diamonds in this context. Here, we demonstrate for the first time that a suitable acquisition technique for the pulse signal generated by an HPHT type IIa diamond detector under ultra-high dose rate irradiation enables the development of an effective system for accurately measuring the dose delivered by a FLASH LINAC. The detection prototype exhibits a linear response to both the dose and dose rate of the incident radiation, demonstrating that the implemented measurement technique effectively mitigates spurious trap-related signals that typically compromise accuracy. Our research, therefore, opens the way for the development of a new generation of diamond dosimeters based on low-cost type IIa diamonds, potentially broadening the application of diamond-based dosimetry in both FLASH and conventional radiotherapy.