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Session: FLASH – Platforms and Instrumentation [Return to Session]

Design and Optimization of 18 MeV Accelerator for X-Ray FLASH Radiotherapy Demonstration System

S Kutsaev1, R Agustsson1, S Boucher1, A Li2, M Ruelas1, K Sheng2, A Smirnov1*, (1) Radiabeam, Santa Monica, CA (2) UCLA School of Medicine, Los Angeles, CA


WE-D-BRA-5 (Wednesday, 7/13/2022) 10:15 AM - 11:15 AM [Eastern Time (GMT-4)]

Ballroom A

Purpose: Emerging evidence indicates that the therapeutic window of radiotherapy can be significantly increased using ultra-high dose rate dose delivery (FLASH), by which the normal tissue injury is reduced without compromising tumor cell killing. In this study, we optimize the design of an 18 MeV electron linac to reach the dose rates for FLASH.

Methods: For a given amount of RF power, typical for conventional clinical electron linacs, it is possible to either maximize beam energy, which scales quadratically, or a beam current that scales linearly. At the same time the dose yield scales cubically with then energy but linearly with the current. As a result of analytical estimation, 18 MeV and 480 uA were selected. Next, the accelerator design was to maximize the utilization of the RF power, which is defined as the shunt impedance of the structure. Finally, a compromise between linac size (length), power utilization and electrodynamics stability also exists and was found via computer simulations in Parmela and CST Microwave Studio.

Results: The optimal dose of RF linac, fed by S-band 5 MW klystron was achieved for 18 MeV electron beam energy. Such accelerator consists of two standing wave sections based 24 on-axis coupled biperiodic cells with an 87 MΩ/m shunt impedance. The first section also includes a 3-cell integrated bunching section, which improves beam transmission from the DC electron gun to 52.5%. The expected X-ray dose of such accelerators 17.5±2.5 Gy/s.m, depending on the X-ray target.

Conclusion: This study determined the optimal design of electron linac, required for producing the high dose rates necessary for the demonstration FLASH effect. The accelerator is based on state-of-the-art technologies and can be fabricated with low risks and reasonable costs, which is essential for demonstration. The full system development is ongoing and the pilot beam is planned for 2023.


Linear Accelerator, Simulation


TH- External Beam- Photons: Development (new technology and techniques)

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