Design and Tuning of a Fast Beam Energy Selection Control System for CYCIAE-230 Cyclotron Beamline

The preliminary beam test of the CYCIAE-230 cyclotron and its beam transportation system to the isocenter of the gantry was successfully conducted at the end of December 2023. During this, various beam transportation tests with different energies are carried out to verify the design of the energy selection system (ESS). The ESS consists of a pair of carbon wedge-shaped degraders, an apochromatic magnet system, and momentum-selecting slits. Once beam energy is selected, the rest of the beam transportation system is controlled to follow the ESS, including synchronization of the 51 beamline magnets in total. The CYCIAE-230 superconducting cyclotron extracts a fixed energy beam of 242.25 MeV. The double-wedge degrader and the beamline system can modulate and transport the beam with energy from 242.35 to 71.84 MeV. In an energy range from 232.12 to 71.84 MeV, it was experimentally verified to be capable of switching down an energy layer (2-mm water depth equivalent) in the order of magnitude of 50 ms. Unlike other degrader designs, the China Institute of Atomic Energy (CIAE) degrader has a significant moment of inertia, making it difficult to achieve fast control. A dedicated energy selection control system has been developed by CIAE, using the VxWorks real-time operating system and its multitask scheduling to control the degrader and synchronize the related magnets quickly. The reported control system also includes an interpolation algorithm to automatically calculate the setpoints for different beam energy to facilitate the beamline’s commissioning. A dedicated user interface is also included to facilitate the commissioning procedures. This article will introduce the control system from both hardware and software and analyze the tuning results.