Pulse-to-pulse Beam Modulation and Event-based Beam Feedback System at KEKB Linac

TL;DR

This paper describes a pulse-to-pulse beam modulation and independent event-based feedback system at KEKB Linac, enabling stable simultaneous injections of different beams with varying parameters.

Contribution

Introduction of a novel beam modulation and feedback system that manages multiple virtual accelerators with independent energy stabilization.

Findings

Successful simultaneous injection of three different beams.

Stable beam parameters achieved despite equipment instabilities.

Independent energy feedback for each virtual accelerator implemented.

Abstract

Beam injections to KEKB and Photon Factory are performed with pulse-to-pulse modulation at 50 Hz. Three very different beams are switched every 20 ms in order to inject those beams into KEKB HER, LER and Photon Factory (PF) simultaneously. Human operators work on one of those three virtual accelerators, which correspond to three-fold accelerator parameters. Beam charges for PF injection and the primary electron for positron generation are 50-times different, and beam energies for PF and HER injection are 3-times different. Thus, the beam stabilities are sensitive to operational parameters, and if any instability in accelerator equipment occurred, beam parameter adjustments for those virtual accelerators have to be performed. In order to cure such a situation, beam energy feedback system was installed that can respond to each of virtual accelerators independently.