Preparation and Execution of the Electrical Quality Assurance Program On the LHC Superconducting Circuits During the Second Long Shutdown

Abstract

The electrical quality assurance (ELQA) of the superconducting circuits of CERN's Large Hadron Collider (LHC) during its second Long Shutdown (LS2) requires the execution of vast measurement campaigns. Each of 1658 electrical circuits as well as the instrumentation of each of the 1746 individual cryo-assemblies housing magnets, bus-bars and other components of the superconducting circuits, has to undergo a series of tests. At the beginning of the shutdown the tests are performed before and after the warmup from cryogenic temperatures. The same tests are repeated at the end of the shutdown, this time before and after the cool-down. As part of the dipole bypass diode insulation consolidation project and due to the replacement of a few non-conform magnets, additional electrical tests and measurements had to be performed throughout the shutdown period. With each measurement, electrical parameters like resistance, complex impedance, and the quality of the insulation are verified and stored for future reference. Due to the many thousands of measurements to be performed, multiple automated mobile test benches had to be developed for the different test types along with dedicated database and analysis software applications for the documentation and follow-up of the test results and the non-conformities observed. In this contribution we describe the collaborative effort between CERN and the Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences in Krakow during the three yearlong preparation process and experiences related to the execution of the ELQA activities during LS2 of the LHC.

New Measurement Techniques Used for the Electrical Quality Assurance of HL-LHC Superconducting Magnets

“…Additionally, measurement of complex impedance proves to be a useful tool to assess the health of the superconducting magnet or the entire superconducting circuit including busbars, current leads, and instrumentation. Those standard tests were described in depth in [1]- [7]. Some of the effects observed in new Nb3Sn based dipole magnets required the following additional tests and measurements:…”