A novel Beam Halo Monitor for the CMS experiment at the LHC

S. Orfanelli, A. E. Dabrowski, M. Giunta, R. Loos, M. J. Ambrose, Jeremiah M Mans, Roger W Rusack, K. Stifter, D. Stickland, F. Fabbri, A. Manna, A. Montanari, N. Tosi, V. Calvelli

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


A novel Beam Halo Monitor (BHM) has been designed and built for the CMS experiment at the LHC. It will provide an online, bunch-by-bunch measurement of background particles created by interactions of the proton beam with residual gas molecules in the vacuum chamber or with collimator material upstream of CMS. The BHM consists of two arrays of twenty detectors that are mounted around the outer forward shielding of the CMS experiment. Each detector is comprised of a cylindrical quartz radiator, optically coupled to a fast ultraviolet-sensitive photomultiplier tube from one end and painted black at the opposite end. Particles moving towards the photomultiplier tube will be detected with time resolution of a few nanoseconds, allowing to measure the flux of background particles produced upstream of CMS and suppress signals from collision-induced products. Monte Carlo simulations were performed to optimise the detector design. Prior to installation, the performance of the prototype detectors was measured in test beams quantifying the detector's direction-sensitive response and time resolution. The BHM was installed during the first LHC long shutdown (LS1) and is currently being commissioned. Design considerations, results from the test-beams supporting the design and the installation of the BHM in the CMS are presented.

Original languageEnglish (US)
Article numberP11011
JournalJournal of Instrumentation
Issue number11
StatePublished - Nov 24 2015

Bibliographical note

Publisher Copyright:
© CERN 2015.


  • Beam-line instrumentation (beam position and profile monitors
  • Cherenkov and transition radiation
  • Detector modelling and simulations I (interaction of radiation with matter, interaction of photons with matter, interaction of hadrons with matter, etc)
  • Instrumentation for particle accelerators and storage rings - high energy (linear accelerators, synchrotrons)
  • beamintensity monitors
  • bunch length monitors)


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