CERN Accelerating science

Article
Title	A Sub-Micron Resolution, Bunch-by-Bunch Beam Trajectory Feedback System and Its Application to Reducing Wakefield Effects in Single-Pass Beamlines
Related title	A SUB-MICRON RESOLUTION, BUNCH-BY-BUNCH BEAM TRAJECTORY FEEDBACK SYSTEM AND ITS APPLICATION TO REDUCING WAKEFIELD EFFECTS IN SINGLE-PASS BEAMLINES
Author(s)	Bett, Douglas R (Oxford U.) ; Burrows, Philip N (Oxford U.) ; Kubo, Kiyoshi (KEK, Tsukuba) ; Okugi, Toshiyuki (KEK, Tsukuba) ; Perry, Colin (Oxford U.) ; Ramjiawan, Rebecca (Oxford U.) ; Terunuma, Nobuhiro (KEK, Tsukuba)
Publication	Geneva : JACoW, 2021
Number of pages	4
In:	JACoW IPAC 2021 (2021) 1382-1385
In:	12th International Particle Accelerator Conference (IPAC 2021), Online, 24 - 28 May 2021, pp.1382-1385
DOI	10.18429/JACoW-IPAC2021-TUPAB020 (publication)
Subject category	Accelerators and Storage Rings
Abstract	A high-precision intra-bunch-train beam orbit feedback correction system has been developed and tested at the KEK Accelerator Test Facility, ATF2. The system uses the vertical position of the bunch measured at two beam position monitors to calculate a pair of kicks which are applied to the next bunch using two upstream kickers, thereby correcting both the vertical position and trajectory angle. Using trains of two electron bunches separated in time by 187.6ns, the system was optimised so as to stabilize the beam offset at the feedback BPMs to better than 350nm, yielding a local trajectory angle correction to within 250nrad. The quality of the correction was verified using three downstream witness BPMs and the results were found to be in agreement with the predictions of a linear lattice model used to propagate the beam trajectory from the feedback region. This same model predicts a corrected be am jitter of c.1nm at the focal point of the accelerator. Measurements with a beam size monitor at this location demonstrate that reducing the trajectory jitter of the beam by a factor of 4 also reduces the increase in the measured beam size as a function of beam charge by a factor of  1.6.
Copyright/License	publication: © 2021 (License: CC-BY-3.0)

Corresponding record in: Inspire