First Observation of the LHC Beam Halo Using a Synchrotron Radiation Coronagraph

Abstract

A test coronagraph for the observation of beam halo has been installed in the Synchrotron radiation monitor line LHCB2 in 2015. This coronagraph is commissioned with LHC operation at 450GeV (injection energy). After some optical testing of the coronagraph with visible Synchrotron radiation in B2, we try to observe artificially-made beam halo. The beam halo of 10⁻³ order of magnitude against the beam core is excited by the kicker of the transverse damper. We have succeeded to observe a diffraction noise free image of beam halo. The effect of beam collimator is also observed. Reduction of beam halo intensity was found nicely proportional to the simultaneously-recorded beam loss