Technical and Practical Information on the Surface Resistance Measurement Bench Using the Shielded Pair Method: Application to the LHC Beam Screen

The shielded pair resonator technique is used to measure the surface resistance of the copper coated LHC beam screen both at room temperature and at cryogenic temperature with a strong magnetic field up to several Teslas, like in the LHC superconducting magnets. From its concept, the RF-based measurements principle appears to be straight forward, but it turns out in practice to be very sensitive to a large number of parameters which are being described in the present report. Some practical hints are proposed to overcome these technical hitches and optimize the geometry as well. An estimate of the thermal load of the LHC beam screen is given, standing in the range 200-250 mW/m for two circulating beams.