Beam Position Detection of a Short Electron Bunch in Presence of a Longer and More Intense Proton Bunch for the AWAKE Experiment
75
E. Senes, R. Corsini, W. Farabolini, A. Gilardi, M. Krupa, T. Lefèvre, S. Mazzoni, M. Wendt
CERN, Meyrin, Switzerland
P. Burrows, C. Pakuza
JAI, Oxford, United Kingdom
P. Burrows, C. Pakuza
Oxford University, Physics Department, Oxford, Oxon, United Kingdom
W. Farabolini
CEA-DRF-IRFU, France
The AWAKE experiment studies the acceleration of electrons to multi-GeV levels driven by the plasma wakefield generated by an ultra-relativistic and high intensity proton bunch. The proton beam, being considerably more intense than the co-propagating electron bunch, perturbs the measurement of the electron beam position achieved via standard techniques. This contribution shows that the electrons position monitoring is possible by frequency discrimination, exploiting the large bunch length difference between the electron and proton beams. Simulations and a beam measurement hint, the measurement has to be carried out in a frequency regime of a few tens of GHz, which is far beyond the spectrum produced by the 1ns long (4 σ Gaussian) proton bunch. As operating a conventional Beam Position Monitor (BPM) in this frequency range is problematic, an innovative approach based on the emission of coherent Cherenkov Diffraction Radiation (ChDR) in dielectrics is being studied. After describing the monitor concept and design, we will report about the results achieved with a prototype system at the CERN electron facility CLEAR.
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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