Design and Performance of the ARIEL X-Ray FLASH Irradiation Platform at TRIUMF
N Esplen1*, L Egoriti2, B Paley3, T Planche3, C Hoehr3, A Gottberg3, M Bazalova-Carter1, (1) University of Victoria, Victoria, BC (2) University Of British Columbia, Vancouver, BC (3) TRIUMF, Vancouver, BC
Presentations
MO-EF-TRACK 4-1 (Monday, 7/26/2021) 3:30 PM - 5:30 PM [Eastern Time (GMT-4)]
Purpose: To optimize, build and commission a novel Bremsstrahlung target and megavoltage irradiation platform for delivering ultrahigh dose-rate radiation to small-animals in an exploration of X-ray FLASH radiotherapy at TRIUMF.
Methods: The design of a tantalum-aluminum (Ta-Al) explosion-bonded conversion target has been optimized using Monte Carlo (MC) and Finite Element Analysis (FEA) simulation methods. The water-cooled Ta-Al target facilitates conversion of a 10MeV, 1kW electron beam at the ARIEL e-linac into an ultrahigh dose-rate (>40Gy/s) x-ray source with <1s pulse-lengths and 0.05%-100% Duty Factor (FLASH mode) while preserving routine beam-dump capabilities in a lower power steady-state. Dose rates in water-phantoms were calculated in slab and CAD geometries using EGSnrc and TOPAS MC codes, respectively, to inform the design of the Ta-target, Al-flange and W-shield thicknesses and geometry. Thermo-mechanical FEA simulations in ANSYS subsequently informed the stress-strain conditions and fatigue life of the target assembly under prescribed conditions resulting in the re-design, and thus revised dose-rate capabilities, of the final prototype. Erosion tests and commissioning will be followed by dosimetric characterization ahead of FLASH treatment planning in small-animal models.
Results: Simulated water-phantom irradiations demonstrate that surface dose-rates of 128Gy/s may be achieved for a 1x1cm² field size and 7.5cm source-to-surface distance using the treatment-beam configuration (E=10MeV,2σ=5mm,P=1kW). Dose rates >40Gy/s are maintained to a depth of 5cm in water. Modular collimation and SSD flexibility allows for >200Gy/s to be achieved at larger field sizes. Assembly temperatures are maintained below the Ta, Al and cooling-water thresholds of 2000, 300 and 100°C, respectively, while the Al strain behavior remains everywhere elastic.
Conclusion: The ARIEL x-ray FLASH experimental platform achieves ultra-high dose-rates within the thermo-mechanical constraints of the system. Target cooling, mechanical robustness and failure mitigation have culminated in a design intended for FLASH and steady-state applications with installation and commissioning planned for May 2021.
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 Chair program and the New Frontiers in Research Fund (NFRFE)
Handouts
Keywords
X-ray Production, Simulation, Linear Accelerator
Taxonomy
TH- External Beam- Photons: Development (new technology and techniques)
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