Signal Processing Architecture for the HL-LHC Interaction Region BPMs
100
D.R. Bett
JAI, Oxford, United Kingdom
A. Boccardi, I. Degl’Innocenti, M. Krupa
CERN, Geneva, Switzerland
In the HL-LHC era, the Interaction Regions around the ATLAS and CMS experiments will be equipped with 24 new Beam Position Monitors (BPM) measuring both counter-propagating beams in a common vacuum chamber. Numerical simulations proved that, despite using new high-directivity stripline BPMs, the required measurement accuracy cannot be guaranteed without bunch-by-bunch disentanglement of the signals induced by both beams. This contribution presents the proposed signal processing architecture, based on direct digitisation of RF waveforms, which optimises the necessary computing resources without a significant reduction of the measurement accuracy. To minimise the number of operations performed on a bunch-by-bunch basis in the FPGA, some of the processing takes place in the CPU using averaged data.
High-Resolution, Low-Latency, Bunch-by-Bunch Feedback Systems for Nanobeam Production and Stabilization
458
P. Burrows, D.R. Bett, N. Blaskovic Kraljevic, T. Bromwich, G.B. Christian, C. Perry, R.L. Ramjiawan
JAI, Oxford, United Kingdom
High-precision intra-bunch-train beam orbit feedback correction systems have been developed and tested in the ATF2 beamline of the Accelerator Test Facility at the High Energy Accelerator Research Organization in Japan. Two systems are presented: 1) The vertical position of the bunch measured at two beam stripline position monitors (BPMs) is used 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. This system was optimized so as to stabilize the beam offset at the feedback BPMs to better than 350 nm, yielding a local trajectory angle correction to within 250 nrad. Measurements with a beam size monitor at the focal point (IP) demonstrate that reducing the trajectory jitter of the beam by a factor of 4 also reduces the observed wakefield-induced increase in the measured beam size as a function of beam charge by a factor of c. 1.6. 2) High-resolution cavity BPMs were used to provide local beam stabilization in the IP region. The BPMs were demonstrated to achieve an operational resolution of ~20 nm. With the application of single-BPM and two-BPM feedback, beam stabilization of below 50 nm and 41 nm respectively has been achieved with a closed-loop latency of 232 ns.
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