Beam Dynamics Design of a Multi-Ion RFQ for Medical Application

Particle radiotherapy based on the medical accelerator is emerging as a major treatment for cancer. To enhance the clinical flexibility of particle radiotherapy and further promote the use of medical accelerators, the Shanghai Institute of Applied Physics (SINAP) has presented a new linear accelerator plan for medical application. The new plan utilizes a 200 MHz Radio Frequency Quadrupole (RFQ) as the injector. The RFQ is designed to accelerate ions with charge-to-mass ratios of 1/3 to 1/2 from 8 keV/u to 750 keV/u. For the beam dynamics design, a new design strategy is presented to enhance the suppression of space charge effects and improve beam capture efficiency by optimizing the modulation, synchronous phase, and focusing strength. The simulation results demonstrate that the multi-ion RFQ can operate at a maximum beam current of 3.2 mA while maintaining a transmission efficiency above 95% with a compact length of 2.5 m. Multi-particle simulations confirm the high reliability of the design. Additionally, input and mechanical error analyses evaluate the RFQ’s tolerance and stability. The research results demonstrate the feasibility of a compact, high-efficiency RFQ for multi-ion acceleration in medical applications, contributing to the advancement of particle therapy.