Dynamic intensity control system with RF-knockout slow-extraction in the HIMAC synchrotron

We have developed a dynamic beam intensity control system intended for use in three-dimensional pencil-beam scanning irradiation. In this system, which controls the spill structure and intensities of the beams extracted from the synchrotron, the amplitude of the RF-knockout is controlled using a 10 kHz response. Its amplitude modulation function is generated based on an analytical one-dimensional model of the RF-knockout slow-extraction. Using feedback control of the proportional and integral controls, this system allows us to control the beam current dynamically in response to the request, as was experimentally verified in the HIMAC synchrotron. In this paper, we describe the system for controlling the amplitude modulation through the inclusion of feedback, and we provide some experimental results.