Dosimetric Characterization of the ARIEL 10 MV X-Ray Ultrahigh Dose-Rate (FLASH) Irradiation Platform at TRIUMF
N Esplen1*, L Egoriti2, T Planche3, A Hart1, B Paley3, C Hoehr3, A Gottberg3, M Bazalova-Carter1, (1) University of Victoria, Victoria, BC, CA, (2) University Of British Columbia, Vancouver, BC, CA, (3) TRIUMF, Vancouver, BC, CA
Presentations
WE-G-206-4 (Wednesday, 7/13/2022) 2:45 PM - 3:45 PM [Eastern Time (GMT-4)]
Room 206
Purpose: To characterize the beam delivery capabilities and dose rates achievable on the new ultrahigh dose-rate (UHDR) 10MV x-ray irradiation platform at TRIUMF.
Methods: At the TRIUMF Advanced Rare Isotope Laboratory (ARIEL) e-linac, the recently installed x-ray FLASH irradiation platform is being characterized ahead of planned FLASH radiobiological experiments. The UHDR x-ray source comprises a water-cooled electron-to-photon conversion target designed to provide dose rates >40Gy/s. To verify the UHDR capabilities of the system, the absolute dose delivered over a prescribed pulse length (<1s) has been evaluated using radiochromic films while a lead-doped fiber-optic scintillator provided online measurements of relative beam output and irradiation time. Films were irradiated at the surface, and depths of 9mm and 18mm in a solid-water phantom placed on a vertical motion stage within a 1x1cm2 collimated beam to simulate delivery to a small animal. In all cases, a 10MeV, 1kW (0.1mA) continuous electron beam was delivered to the converter using pulse lengths of up to 400ms.
Results: Film doses and temporal information from the scintillator together allowed for calculating the delivered dose rate. Radiochromic films irradiated in the phantom located at an 8.5cm source-to-surface distance in the single (FLASH) pulsed mode yielded doses of 11.6 and 13.8 and 9.5Gy at water-equivalent depths of 0, 0.9 and 1.8-cm, respectively, for a 5mm square ROI. Scintillator measurements verified a 165ms pulse length, from which the corresponding dose-rates were calculated to be 70.3, 83.6 and 57.6Gy/s. Improved beam spot centering on the target will be necessary to improve beam profile symmetry. Field flattening using 3D-printed compensators may be applied to improve dose homogeneity.
Conclusion: Beam commissioning and dosimetry have been conducted on the ARIEL x-ray FLASH irradiation platform. Measured dose rates support that the 10MV x-ray beam may be used as a UHDR source compatible with FLASH radiobiological experiments.
Funding Support, Disclosures, and Conflict of Interest: This work was partially funded by the National Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant, Canada Research Chairs program and the New Frontiers in Research Fund (NFRF)
Keywords
X-ray Production, Radiochromic Film, Scintillators
Taxonomy
TH- External Beam- Photons: Development (new technology and techniques)
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