High Frequency Electro-Optic Beam Position Monitors for Intra-Bunch Diagnostics at the LHC

Stephen Gibson, Alberto Arteche, Alessio Bosco, P. Y. Darmedru, Thibaut Lefevre, Tom Levens

Research output: Chapter in Book/Report/Conference proceedingConference contribution


At the HL-LHC, proton bunches will be rotated by crab-cavities close to the interaction regions to maximize the luminosity. A method to rapidly monitor the transverse position of particles within each 1 ns bunch is required. A novel, compact beam diagnostic to measure the bunch rotation is under development, based on electro-optic crystals, which have sufficient time resolution (< 50ps) to monitor intra-bunch perturbations. The electro-optic beam position monitor uses two pairs of crystals, mounted on opposite sides of the beam pipe, whose birefringence is modified by the electric field of the passing charged particle beam. The change of birefringence depends on the electric field which itself depends on the beam position, and is measured using polarized laser beams. The electro-optic response of the crystal to the passing bunch has been simulated for HL-LHC bunch scenarios. An electro-optical test stand including a high voltage modulator has been developed to characterize LiTaO3 and LiNiO3 crystals. Tests to validate the different optical configurations will be reviewed. The opto-mechanical design of an electro-optic prototype that will be installed in the CERN SPS will be presented.
Original languageEnglish
Title of host publication4th International Beam Instrumentation Conference
Subtitle of host publicationIBIC2015, Melbourne, Australia
PublisherJACoW Publishing
ChapterBPMs and Beam Stability
Number of pages5
ISBN (Electronic)978-3-95450-176-2
Publication statusPublished - Jan 2016

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