Modeling of Interfilament Coupling Currents and Their Effect on Magnet Quench Protection

Ambrosio

Bajas

et al. 2018

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Abstract-CERN and US LARP (LHC Accelerator Research Program) are jointly developing Nb3Sn quadrupole magnets to be installed in the LHC for its upgrade to higher luminosity. These magnets' quench protection system will include a combination of quench heaters attached to the coil surfaces and CLIQ units electrically connected to the magnets. Different protection elements have been characterized separately and simultaneously by implementing them on two 1.2 meter long model quadrupole magnets, tested at FNAL and CERN, and one 4.0 meter long mirror magnet tested at BNL. After analyzing the test data, their performances have been positively evaluated. Furthermore, the electro-thermal transients occurring after a quench have been simulated with the LEDET software and the results compared to experimental results. The preferred quench protection system configuration relies both on heaters and CLIQ. This solution is based on electrically robust components, achieves an effective reduction of the coils hot-spot temperature after a quench, and offers increased redundancy against component failures.

Section: B Simulation Resultsmentioning

confidence: 99%

“…Magnet discharges reproducing LHC relevant conditions were performed and compared to simulation results obtained with the LEDET (Lumped-Element Dynamic Electro-Thermal) program [14], [32], [33].…”

Section: Parametermentioning

confidence: 99%

Quench Protection Performance Measurements in the First MQXF Magnet Models

Ambrosio

Bajas

et al. 2018

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“…However, the presence of inter-filament coupling currents significantly influences the electro-magnetic and thermal transient [9]. First, the magnet differential inductance is reduced due to the coupling currents generated in the wires.…”

Section: A Effect Of Coupling Currents On Energy-extraction Dischargementioning

confidence: 99%

“…The alternative protection system based on CLIQ [5]- [7] is investigated for the sextupole magnet protection. The analysis is performed with the LEDET (Lumped-Element Dynamic Electro-Thermal) program [5], [8], [9], which includes non-linear effects such as inter-filament coupling loss, quench-back, and reduction of the differential inductance due to coupling currents.…”

Section: Introductionmentioning

confidence: 99%

Quench Protection of a Nb$_3$Sn Superconducting Magnet System for a 45-GHz ECR Ion Source

Hafalia

Juchno

et al. 2018

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Abstract-Lawrence Berkeley National Laboratory (LBNL) in collaboration with the Institute of Modern Physics (IMP) has developed a Nb3Sn-based superconducting magnet system for a fourth-generation Electron Cyclotron Resonance (ECR) source, with a goal of achieving the magnetic field required for operating at the microwave frequency of 45 GHz. The magnet system is composed of one sextupole magnet inside three solenoids of different sizes manufactured from Nb3Sn round wire. Given the high stored energy density and relatively low wire copper fraction, the coils are not self-protected in the case of a quench. The study of the transient following a quench is carried out by means of the LEDET (Lumped-Element Dynamic Electro-Thermal) program, which includes a detailed simulation of the inter-filament coupling losses developing in the wire. Non-linear effects occurring in the magnet, such as coupling loss and differential inductance reduction, have a significant impact on protecting these magnets. The resulting baseline quench protection strategy based on four independent energy extraction systems protecting the four magnets meets the quench protection requirements. Furthermore, in order to enhance the redundancy of the quench protection system and reduce the peak voltages to ground, the implementation of a CLIQ (Coupling-Loss Induced Quench) system is considered.

“…The magnet current and voltages across the coils measured during the training quenches are presented. Furthermore, the experimental results are compared to simulations performed with the LEDET (Lumped-Element Dynamic Electro-Thermal) program [14], [30], [31], which is part of the STEAM framework developed at CERN [32]. During the magnet test campaign, a short circuit developed between one coil and a heater strip, which caused the interruption of the tests [33], [34].…”

mentioning

confidence: 99%

Quench Protection of the First 4-m-Long Prototype of the HL-LHC Nb<inline-formula> <tex-math notation="LaTeX">$_3$</tex-math> </inline-formula>Sn Quadrupole Magnet

Ambrosio

Bortot

et al. 2019

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The quadrupole magnets for the LHC upgrade to higher luminosity are jointly developed by CERN and US-LARP (LHC Accelerator Research Program). These Nb3Sn magnets will be protected against overheating after a quench by a combination of heaters bonded to the coil outer surface and CLIQ (Coupling-Loss Induced Quench) units. The first 4 meter long prototype magnet, called MQXFAP1, was tested at the Brookhaven National Laboratory in stand-alone configuration. The magnet training campaign, consisting of 18 quenches, was interrupted due to the development of a short circuit between one heater strip and the coil. During the campaign, different quench protection schemes were implemented, including heaters attached to outer and inner layers, one CLIQ unit, and the energy-extraction system. The configuration including outer-layer heaters and CLIQ achieved the fastest current discharge, hence the lowest hot-spot temperature. The electro-magnetic and thermal transients after a quench were simulated with the program STEAM-LEDET and found in good agreement.