Assessment of MQXF Quench Heater Insulation Strength and Test of Modified Design

The HL-LHC interaction region magnet triplets (Q1, Q2, and Q3) will be composed of superconducting Nb
₃
Sn quadrupoles. The MQXF quadrupole protection system is based on CLIQ (Coupling-Loss Induced Quench system) and outer layer quench heaters. This paper reports a summary of quench heaters to coil high voltage tests performed on MQXF short and long coils in air after fabrication, and in air and He gas after magnet training. Breakdown voltage values demonstrate good margin with respect to the Electrical design criteria for the HL-LHC inner triplet magnets. A modification in the quench heater installation- with an extra layer of fiber glass between the coil and the quench heater trace- has been proposed and tested in a mirror magnet to further increase electrical margins. Results demonstrated improvements of high voltage margin at the expense of a clear increase of hot spot temperature. The baseline heater to coil insulation was assessed to be able to guarantee safe operation for the Nb
₃
Sn quadrupole magnets for the interaction regions of HL-LHC.