Protecting a Full-Scale <inline-formula> <tex-math notation="TeX">$\hbox{Nb}_{3}\hbox{Sn}$</tex-math></inline-formula> Magnet With CLIQ, the New Coupling-Loss-Induced Quench System

Abstract

A new protection system for superconducting magnets called coupling-loss induced quench system (CLIQ) has been recently developed at CERN. Recent tests on Nb-Ti coils have shown that CLIQ is a valid, efficient, and promising method for the protection of high-magnetic-field superconducting magnets. However, the protection of new-generation Nb 3 Sn accelerator magnets is even more challenging due to the much higher stored energy per unit volume and to the significantly larger enthalpy needed to initiate and propagate a normal zone in such coils. Now, the CLIQ system is tested for the first time on a Nb 3 Sn magnet in the CERN magnet test facility in order to investigate its performance in practice, thereby validating the method for this type of superconducting magnets as well. Furthermore, we successfully reproduced the electrothermal transients during a CLIQ discharge. Finally, the implementation of various CLIQ-based protection schemes for the full-scale Nb 3 Sn quadrupole magnet for the LHC high luminosity upgrade is discussed. The impact of key system parameters on CLIQ performance and the advantages and drawbacks of using multiple CLIQ units on a single magnet are discussed.

Lumped-Element Dynamic Electro-Thermal model of a superconducting magnet

“…The simulation results have been routinely validated against experimental results [1,13,14,15,16,17,18,19,20,21,22]. …”

First Implementation of the CLIQ Quench Protection System on a Full-Scale Accelerator Quadrupole Magnet

“…In fact, the choice of the current changes to introduce in the various coil sections allows an effective magnetic-field superposition and an optimized distribution of the coupling loss generated in the strands [1], [5], [6]. In future magnets, the order of the poles or layers can be optimized, but in the case of existing magnets the available configurations are limited to those obtained by connecting additional terminals in coil positions which are easily reachable.…”

“…Note the presence of multiple regions where opposite current changes are introduced in physically adjacent sections. This feature improves the CLIQ performance due to the tighter magnetic coupling between the two CLIQ branches A and B, which highly reduces the impedance of the CLIQ discharge circuit and allows an effective superposition of the magnetic-field changes introduced by A and B [1], [5], [6].…”

CLIQ : a new quench protection technology for superconducting magnets

“…In figure 2.2 the results of a typical CLIQ discharge are presented [89]. One 28.2 mF, 500 V CLIQ unit is connected to the midpoint of a 120 mm aperture Nb 3 Sn quadrupole model magnet developed by the US LARP collaboration for the high luminosity LHC [79,[90][91][92][93][94].…”

“…The high and fast energy deposition required for protecting full-size accelerator magnets without increasing the charging voltage beyond acceptable limits makes the Multi-CLIQ solution very promising [89]. Note that an N C -CLIQ system can achieve a peak power deposition N 2 C times higher than a 1-CLIQ system due to the reduction of the circuit impedance.…”