Douglas Bett

JACoW : Intra-Train Position and Angle Stabilisation at ATF Based on Sub-Micron Resolution Stripline Beam Position Monitors

A low-latency, sub-micron resolution stripline beam position monitoring (BPM) system has been developed and tested with beam at the KEK Accelerator Test Facility (ATF2), where it has been used to drive a beam stabilisation system. The fast analogue front-end signal processor is based on a single-stage radio-frequency down-mixer, with a measured latency of 16 ns and a demonstrated single-pass beam position resolution of below 300 nm using a beam with a bunch charge of approximately 1 nC. The BPM position data are digitised on a digital feedback board which is used to drive a pair of kickers local to the BPMs and nominally orthogonal in phase in closed-loop feedback mode, thus achieving both beam position and angle stabilisation. We report the reduction in jitter as measured at a witness stripline BPM located 30 metres downstream of the feedback system and its propagation to the ATF interaction point.

Development of a Low-latency, Micrometre-level Precision, Intra-train Beam Feedback System based on Cavity Beam Position Monitors

A low-latency, intra-train, beam feedback system utilising a cavity beam position monitor (BPM) has been developed and tested at the final focus of the Accelerator Test Facility (ATF2) at KEK. A low-Q cavity BPM was utilised with custom signal processing electronics, designed for low latency and optimal position resolution, to provide an input beam position signal to the feedback system. A custom stripline kicker and power amplifier, and a digital feedback board, were used to provide beam correction and feedback control, respectively. The system was deployed in single-pass, multi-bunch mode with the aim of demonstrating intra-train beam stabilisation on electron bunches of charge ~1 nC separated in time by c. 220 ns. The system has been used to demonstrate beam stabilisation to below the 75 nm level. Results of the latest beam tests, aimed at even higher performance, will be presented.