Author: Robert Berry, John Buatti, Nathan Burger, Ryan T. Flynn, Greg Johns, Maksim Kravchenko, Sergey Kutsaev, Yen-Po Lee, Marcos Ruelas, Joel J. St-Aubin, Timothy J. Waldron 👨🔬
Affiliation: RadiaBeam Technologies, University of Iowa 🌍
Purpose: To report the factory acceptance tests of a preclinical linear accelerator, the FLEX-9 electron FLASH linac from RadiaBeam Technologies.
Methods: The FLEX-9 FLASH electron linac is designed to deliver a 9.5 MeV electron FLASH beam with various pulse lengths and up to 300 Hz repetition rates. The factory acceptance tests of the FLEX-9 were performed using Ashland HD-V2 and EBT-XD Gafchromic films to measure the beam percent depth dose (PDD), field size, and dose rate in acrylic slabs. Dose rate validation was performed using TLD-400. PDD, field size, and dose rate were measured at 30 cm source-surface distance (SSD) and PDD and field size were measured at 100 cm SSD.
Results: The FLEX-9 FLASH linac energy was measured to be 9.29 ± 0.15 MeV at 30 cm SSD and 9.24 ± 0.15 MeV at 100 cm SSD based on the practical range extracted from the PDD. The field size full width at half maximum is 2.67 x 2.68 cm2 in the cross-plane and in-plane directions respectively at 30 cm SSD and 11.01 x 11.03 cm2 in the cross-plane and in-plane directions respectively at 100 cm. The dose-per 5 µs pulse was 199.1 ± 7.96 Gy/pulse, and 204.0 ± 8.16 Gy/pulse for the TLD-400 and HD-V2 film measurements, respectively. The dose per 6 µs pulse is up to 221 Gy/pulse at 30 cm SSD, corresponding to 66,391 Gy/s at a repetition rate of 300 Hz.
Conclusion: This work indicates that the preclinical FLEX-9 linear accelerator is a robust system that can deliver a 9.5 MeV electron FLASH beam with 221 Gy per 6 µs pulse at 30 cm SSD. These data are the first measurements made on the FLEX-9 FLASH electron linac at a dose rate of 200 Gy/pulse.