Design and operation of a prototype interaction point beam collision feedback system for the International Linear Collider

Abstract

A high-resolution, intra-train position feedback system has been developed to achieve and maintain collisions at the proposed future electron-positron International Linear Collider (ILC). A prototype has been commissioned and tested with beam in the extraction line of the Accelerator Test Facility at the High Energy Accelerator Research Organization (KEK) in Japan. It consists of a stripline beam position monitor (BPM) with analogue signal-processing electronics, a custom digital board to perform the feedback calculation and a stripline kicker driven by a high-current amplifier. The closed-loop feedback latency is 148 ns. For a three-bunch train with 154 ns bunch spacing, the feedback system has been used to stabilize the third bunch to 450 nm. The kicker response is linear, and the feedback performance is maintained, over a correction range of over ±60 µm. The propagation of the correction has been confirmed by using an independent stripline BPM located downstream of the feedback system. The system has been demonstrated to meet the BPM resolution, beam kick and latency requirements for the ILC.

A sub-micron resolution, bunch-by-bunch beam trajectory feedback system and its application to reducing wakefield effects in single-pass beamlines

“…2016 measurements with the system demonstrated a position resolution of 157 ± 8 nm for a beam charge of 1.3 nC (0.82 × 10 10 electrons/bunch) [8]. The processed BPM signals are input to a custom-made digital feedback ('FONT5') board [5,7]. The FONT5 board design features a Field-Programmable Gate Array (FPGA) along with nine analogue-to-digital converters and a pair of digital-to-analogue converters.…”

“…The ATF is capable of generating multi-bunch trains by accumulating bunches in the damping ring over the course of several pulses and then extracting them in a single pulse. The Feedback On Nanosecond Timescales (FONT) group at the University of Oxford developed a low-latency (∼150 ns) single-phase beam feedback system [5] as a prototype of the intra-train beam stabilisation system required for the interaction point of the ILC. Here, we report the results of a feedback system based on this technology to stabilize both the beam position and the trajectory angle in the ATF2.…”

A high-resolution, low-latency, bunch-by-bunch feedback system for nano-beam stabilization

“…This system incorporates five cavity BPMs similar to those reported in [13], but with a much lower 'quality factor'. The downmixed BPM signals are digitized using a custom FPGAbased feedback controller, the 'FONT5A' board [10,14], and the feedback calculation is performed on an FPGA mounted on the board. An analogue correction signal is output from the board, amplified using a custom power amplifier with a fast rise-time (35 ns) [15], and used to drive a stripline kicker, IPK.…”

“…group [8] has developed several generations of prototype bunch-by-bunch beam-stabilization feedback systems which have been tested at the ATF. A feedback system was deployed in the upstream section of the ATF2 extraction line, using high-resolution bunchposition measurements from stripline beam-position monitors (BPMs) [9], to demonstrate [10] the resolution, correction-range and latency requirements for the ILC IP beam collision feedback system [11]. An extended feedback system based on this hardware was recently used to stabilize the beam trajectory before its entrance to the final-focus region, and yielded a significant reduction in the impact of 'wakefields' on the beam-size growth [12].…”

Closed orbit feedback system for the fast ramping hadron synchrotrons

“…corrector magnets and power converters. COFB system has been an integral part of the synchrotrons and storage rings of light sources as well as of hadron machines for stable beam operations [1][2][3][4][5][6][7][8]. Orbit correction relies on the measurement of transverse beam position at discrete locations in the synchrotron and applying the appropriate kicks to the beam with dedicated dipole magnets located at other discrete locations to counteract the existing field errors in the synchrotron.…”