Development of fast micron-resolution beam position monitors for linear collider beam-based feedback systems

We present the design of prototype fast beam position monitor (BPM) signal processors for use in inter-bunch beam-based feedbacks for linear colliders and electron linacs. We describe the FONT4 intra-train beam-based digital position feedback system prototype deployed at the Accelerator test facility (ATF) extraction line at KEK, Japan. The system incorporates a fast analogue beam position monitor front-end signal processor, a digital feedback board, and a fast kicker-driver amplifier. The total feedback system latency is less than 150ns, of which less than 10ns is used for the BPM processor. We report preliminary results of beam tests using electron bunches separated by c. 150ns. Position resolution of order 1 micron obtained.

I. Introduction

The international linear collider (ILC) requires a fast interaction point (IP) feedback system [1], operating on a bunch by bunch level, to maximize luminosity at the point of collision. This system is required to reduce bunch to bunch jitter, caused by external influences, therefore ensuring alignment of the incoming electron and positron bunches for collision. Fig. 1.

Representation of an IP intra-train feedback system for an interaction region with a crossing angle [2]. The position of the outgoing beam is measured using a BPM and a correcting kick applied to the incoming opposing beam.