RF Measurements of the New TOTEM Roman Pot

Abstract

The TOTEM experiment has been designed to measure the total proton-proton cross section and to study the elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots, movable beam pipe insertions, hosting silicon detectors. In the first period of LHC operation no relevant problems were detected with Roman Pots retracted or inserted during special runs. However, when operating the LHC with high intensity beams, impedance induced heating has been observed during the Roman Pots insertion. In order to be compatible with the higher LHC beam current foreseen after the LS1, a new version of the Roman Pot has been proposed and optimized with respect to the beam coupling impedance. In this work we present the bench impedance measurements carried out on the new Roman Pot prototype. Single and double wire measurements, as well as probe measurements, were performed in order to detect possible harmful resonant modes. The laboratory setup has been as well simulated with the help of CST Particle Studio in order to benchmark the measurement results. Measurements and simulations are in close agreement confirming the equipment compatibility with the LHC requirements for safe operation.