Roman Pot insertions in high-intensity beams for the CT-PPS project at LHC

Abstract

In 2015 the Roman Pots (RPs) of the CMS-TOTEM Precision Proton Spectrometer in the LHC Interaction Region 5 successfully approached the 6.5 TeV beam in regular fills (β∗ = 0.8 m) to distances of 25 beam width sigmas at all intensity steps reached during that running season, i.e. up to 2244 bunches producing a luminosity of 4.8 × 1033 cm-2s-1. Given that earlier insertion tests at low β∗ before the Long Shutdown 1 (LS1) had suffered from impedance heating at the RPs, this first-time achievement proves the effectiveness of the impedance mitigation actions undertaken in LS1 and represents an important milestone towards physics production at distances as small as 15 sigmas. This contribution reviews the diagnostic measurements assessing debris showers and beam impedance effects, i.e. the data from Beam Loss Monitors, beam vacuum gauges and temperature sensors. The dependences of the observables on luminosity or beam current are shown. Extrapolations to higher luminosities and smaller distances to the beam do not indicate any fundamental problems. Finally the plans for 2016 are outlined.