Uniformity Control of Scanned Beam in 300 MeV Proton and Heavy Ion Accelerator Complex at SESRI

In recent years, heavy ion accelerator technology has been rapidly developing worldwide and widely applied in the fields of space radiation simulation and particle therapy. Usually, a very high uniformity in the irradiation area is required for the extracted ion beams, which is crucial because it directly affects the experimental precision and therapeutic effect. Specifically, ultra-large-area and high-uniformity scanning are crucial requirements for spacecraft radiation effects assessment and serve as core specification for beamline terminal design. In the 300 MeV proton and heavy ion accelerator complex at the Space Environment Simulation and Research Infrastructure (SESRI), proton and heavy ion beams will be accelerated and ultimately delivered to three irradiation terminals. In order to achieve the required large irradiation area of 320 mm×320 mm, horizontal and vertical scanning magnets are used in the extraction beam line. However, considering the various requirements for beam species and energies, the tracking accuracy of power supplies (PSs), the eddy current effect of scanning magnets, and the fluctuation of ion bunch structure will reduce the irradiation uniformity. To mitigate these effects, a beam uniformity optimization method based on the measured beam distribution was proposed and applied in the accelerator complex at SESRI. In the experiment, the uniformity is successfully optimized from 75% to over 90% after five iterations of adjustment to the PS waveforms. In this paper, the method and experimental results were introduced.