Steady state heat transfer experimental studies of LHC superconducting cables operating in cryogenic environment of superfluid helium

The heat management is a basic and fundamental aspect of the superconducting magnets used in the CERN Large Hadron Collider. Indeed, the coil temperature must be kept below the critical value, despite the heat which can be generated or deposited in the magnet during the normal operations. Therefore, this thesis work aims at determining the heating power which can be extracted from the superconducting cables of the LHC, specially through their electrical insulation which represents the main thermal barrier. An experimental measurement campaign in superfluid helium bath was performed on several samples reproducting the main LHC magnets. The heating power was generated in the sample by Joule heating and the temperature increase was measured by means of Cernox bare chip and thermocouples. An innovative instrumentation technique which also includes the in-situ calibration of the thermocouples was developed. A thorough uncertainty analysis on the overall measurement chain concluded the experimental setup. The present study allowed to thermally characterize the main LHC magnets: Main Bending, Main Quadrupole and MQXA. The results show the thermal magnets behaviour as a function of bath temperature, heating configuration of the sample, sensor position and the hydrostatic helium pressure effect.