Towards Accessible Proton Radiotherapy: Beam Optics Design for a Compact Medical Proton Accelerator
CM Lund1*, PM Jung2, MJ Maher1, J Bancheri1, T Planche2, R Baartman2, J Seuntjens3, (1) McGill University, Montreal, QC, CA, (2) TRIUMF, Vancouver, BC, CA, (3) University Health Network, Toronto, ON, CA
Presentations
WE-C930-IePD-F7-6 (Wednesday, 7/13/2022) 9:30 AM - 10:00 AM [Eastern Time (GMT-4)]
Exhibit Hall | Forum 7
Purpose: To develop a new approach for proton bunch formation and to demonstrate a mechanism for maintaining these bunches during acceleration in a dielectric wall accelerator (DWA)-based compact medical proton accelerator.
Methods: A linear optics model of the DWA was developed and implemented in the open-source envelope code TRANSOPTR. Using this model, a DWA-based beamline was developed as follows. A linear time gradient was imposed on the accelerating fields to produce a longitudinal focusing effect. A short 1.5 MeV DWA segment was placed before a 90 degree magnetic bend section that directed the particles through a collimator. In this way, any unbunched particles would be removed from the beam. The particles then passed through a larger 200 MeV DWA segment before being focused towards the isocentre (100 cm).
Results: Longitudinal control was demonstrated in the 1.5 MeV DWA segment using a linear time gradient of 48.6 MeV/m/ns. This control was maintained throughout the acceleration process by a linear time gradient of 20.8 MeV/m/ns in the 200 MeV DWA segment. Transverse control was also demonstrated, indicating that the defocusing effect of the bunching process can be sufficiently compensated for by external magnets. Particle bunches exited the main accelerator with an average energy of 201.6 MeV and reached the isocentre with a radially symmetric spot size with diameter less than 5 mm. Dispersion was shown to be sufficiently compensated for within the collimated bend section.
Conclusion: These findings indicate that longitudinal control in a DWA-based accelerator is possible when the accelerating fields are allowed to increase linearly in time. A proof-of-concept of a novel DWA-based bunching component is demonstrated within the context of a dispersion-free medical beamline. Work is ongoing to characterize the efficiency of the collimator and to study the transitions between low and high field regions.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by NSERC (RGPIN-2019-06746).
Keywords
Protons, Radiation Therapy, Modeling
Taxonomy
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