S1643
Physics - Detectors, dose measurement and phantoms
ESTRO 2026
do not agree with TPS. However, at 5 mm depth, film and TPS agree, and dose at this depth is therefore accurately accounted for in plan optimization. A large cohort in vivo dosimetry measurement study would be needed to further refine the subtle differences between energies. Keywords: surface dose, ring gantry, breast
Proffered Paper 1825
A superconducting accelerator irradiation system with 1–30 MeV energy and widely tunable dose rates, for FLASH-RT biological and pre-clinical reserach Jianhan Sun 1 , Mengyi Tai 1 , Juntao Liu 1 , Jianfeng Lv 1 , Jiadong Wang 1 , Yingsong Dai 1 , Shuai Liu 1 , Deyang Wang 1 , Chenyang Wang 1 , Yuhao Wang 1 , Hang Xu 1 , Lin Lin 1 , Yibao Zhang 2 , Senlin Huang 1 1 State Key Laboratory of Nuclear Physics and Technology and Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing, China. 2 Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China Purpose/Objective: Research and clinical translation of FLASH radiotherapy （ FLASH-RT ） are limited by the restricted parameter flexibility of current irradiation systems, which prevents systematic investigation of energy, dose rate, and pulse structure effects within a single device. This study aims to develop an accelerator-based system with broadly tunable energy and dose rate to support comprehensive biological and pre-clinical FLASH-RT research. Material/Methods: An accelerator irradiation system was constructed, comprising a DC-SRF photocathode gun, a 2×9-cell superconducting linac, and integrated beam transport, control, and diagnostics. Electrons are generated via the photoelectric effect and accelerated using direct- current (DC) and radio-frequency (RF) fields, enabling precise and wide-range tuning of beam energy and charge, through phase and amplitude control of drive laser and RF. Dosimetry was performed with Faraday cups, scintillator screens, fast current transformers (FCT) and radiochromic films (RCF) across multiple beam modes. Dose and dose rate were modulated by varying pulse structure and bunch charge. Experimental terminals for cell and small-animal studies were also established.
Figure 1. (a) Schematic of the accelerator-based irradiation system. (b) Experimental station for cell and (c) mouse irradiation. (d) Three temporal structures of electron beam. Results: The system delivered stable electron energies from 1 to 30 MeV, with the electron gun providing 1–3 MeV beams and the 2×9-cell linac boosting energy up to 30 MeV. Three time structures—single pulse, macro pulse, and continuous wave (CW)—were available, with freely adjustable duty cycle, pulse width, and bunch charge. As a result, dose rates were tunable from conventional (<0.1 Gy/s) to ultra-high dose rate (UHDR, >10,000 Gy/s) levels with considerable stability and reproducibility. The electron gun achieved CW mode for over 8 hours at 0.1 mA current (≈7000 Gy/s average dose rate). Accurate dose control was achieved across dose-rate ranges, and RCF measurements showed reliable consistency.
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