Surface Resistance Measurements for the LHC Beam Screen

A critical review of resistive losses in the LHC beam screen, taking into account anomalous skin effect and surface roughness, has triggered a programme of surface resistance measurements at different temperatures, frequencies and magnetic field intensities. The aim is to establish a realistic heating budget for the LHC cryogenic system and to optimize the fabrication process for the copper coating of the beam screen. Preliminary results at cryogenic temperatures (without magnetic field) indicate a surface resistance about a factor two larger than previously estimated: an absolute measurement precision of a few per cent is reached by comparing the quality factors of even and odd TEM modes in a cylindrical structure with two inner conductors.