External Coil Coupled Loss Induced Quench (E-CLIQ) System for the Protection of LTS Magnets

Abstract

The next generation of Nb3Sn accelerator magnets are pushed to higher magnetic fields, higher stored energy and higher energy density. This brings additional challenges when it comes to quench protection. At CERN, a fast quench protection system is under development that introduces normal zones directly in the coil's conductor by inductive heating. This system is called External coil Coupled Loss Induced Quench (E-CLIQ). The E-CLIQ device comprises many small copper coils that are strategically placed near the main coils. Once a quench is detected, a capacitor is discharged in to the E-CLIQ coils, resulting in the characteristic damped oscillating current of an RLC circuit. This results in a large, but local applied dB/dt on the conductor of the main magnet system, which locally heats it by induced interfilament and interstrand coupling loss. Such a system has the advantage of being fast by introducing normal zones in potentially less than 10 ms, it doesn't rely on heat flow through the insulation layers of the coil, as is the case with traditional quench heaters, and it is not electrically connected to the main circuit.In this paper, the E-CLIQ system is introduced, several first demonstrator coils are presented and the results of a first proofof-concept test are shown.

Coupled axial and transverse currents method for finite element modelling of periodic superconductors

“…As a second verification step, we consider the 54-filament strand geometry defined in table 1, with p = 19 mm, but now with realistic field-dependent material properties for both the Nb-Ti filaments and the copper matrix 5 . We fix the 5 A version of GetDP compiled with these material functions can be found online at https://cern.ch/cerngetdp. temperature to 1.9 K. The resistivity of the Nb-Ti filaments is described by the power law [43]:…”

“…As the magnetic field and stored energy density increase, the quench protection transients become generally shorter with much higher current and field change rates. In addition, there is an increased interest in and application of quench protection methods that rely on inducing a high current and/or field change rate in a magnet to quickly transition a large part of it to a normal state [4][5][6].…”