Roman Pot Insertions in High-Intensity Beams for the CT-PPS Project at LHC

The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) at the LHC IP5 aims at exploring diffractive physics at high luminosity in standard LHC fills. It is based on 14 Roman Pots (RPs), designed to host tracking and time-of-flight detectors for measuring the kinematics of leading protons. To reach the physics goals, the RPs will finally have to approach the beams to distances of 15 beam σs (i.e. ~1.5 mm) or closer. After problems with showers and impedance heating in first high-luminosity RP insertions in 2012, the LS1 of LHC was used for upgrades in view of impedance minimisation and for adding new collimators to intercept RP-induced showers. In 2015 the effectiveness of these improvements was shown by successfully inserting the RPs in all LHC beam intensity steps to a first-phase distance of ~25 σs. This contribution reviews the measurements of debris showers and impedance effects, i.e. the data from Beam Loss Monitors, beam vacuum gauges and temperature sensors. The dependences of the observables on the luminosity are shown. Extrapolations to L=10³⁴ cm⁻² s⁻¹ and smaller distances to the beam do not indicate any fundamental problems. The plans for 2016 are outlined.