A double multi-turn injection scheme for generating mixed helium and carbon ion beams at medical synchrotron facilities

TL;DR

This paper presents the first successful implementation of a double multi-turn injection scheme to generate a mixed helium and carbon ion beam at a medical synchrotron, enabling potential online range verification in hadron therapy.

Contribution

It introduces a novel injection scheme for creating mixed ion beams, demonstrated at the MedAustron facility with detailed simulations and experimental validation.

Findings

Successful generation and extraction of mixed helium and carbon beams.

Effective online range verification potential during therapy.

Implementation details and experimental results at MedAustron.

Abstract

The low relative charge-to-mass ratio offset of 0.065% between fully ionized helium-4 and carbon-12 ions enables simultaneous acceleration in hadron therapy synchrotrons. At the same energy per mass, helium ions exhibit a stopping range approximately three times greater than carbon ions. They can therefore be exploited for online range verification downstream of the patient during carbon ion beam irradiation. One possibility for creating this mixed beam is accelerating the two ion species sequentially through the LINAC and subsequently "mixing" them at injection energy in the synchrotron with a double multi-turn injection scheme. This work reports the first successful generation, acceleration, and extraction of a mixed helium and carbon ion beam using this double multi-turn injection scheme, which was achieved at the MedAustron therapy accelerator in Austria. A description of the double multi-turn injection scheme, particle tracking simulations, and details on the implementation at the MedAustron accelerator facility are presented and discussed. Finally, measurements of the mixed beam at delivery in the irradiation room using a radiochromic film and a low-gain avalanche diode (LGAD) detector are presented.