Quench Protection System Research Articles

Experimental Study and Simulation of Quench in MgB2 Coils for Wind Generators

In the frame of the European Union funded SUPRAPOWER Project, MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> conduction-cooled coils are foreseen to be used in the rotor of synchronous wind turbine generators. As a result, a conceptual design of a 10 MW superconducting (SC) generator will be made and a Rotating Magnetic Validator (RMV) will be constructed and tested, with two rotating SC coils. The main dimensions and working conditions will be kept in the RMV and in the 10 MW generator. The RMV has been conceived is such a way that it can be transformed in a generator. Numerical quench simulations have to be performed in order to design a suitable quench protection system. Due to the uncertainty of some material properties and its importance for the machine operation, an experimental validation must be performed in order to resolve discrepancies. Under this premises, a full size MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> double pancake coil has been manufactured and instrumented to trigger a controlled quench.

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

Author(s): Ravaioli, E; Bajas, H; Datskov, VI; Desbiolles, V; Feuvrier, J; Kirby, G; Maciejewski, M; Ten Kate, HHJ; Verweij, AP; Willering, G | Abstract: The coupling-loss induced quench system (CLIQ) is an innovative method for the protection of high-field superconducting magnets. With respect to the conventional method based on quench heaters, it offers significant advantages in terms of electrical robustness and energy-deposition velocity. Its effective intrawire heating mechanism targets a fast and homogeneous transition to the normal state of the winding pack, hence assuring a quick magnet discharge and avoiding overheating of the coil's hot spot. Furthermore, it is possible to implement CLIQ as a time- and cost-effective repair solution for the protection of existing magnets with broken quench heaters. After being successfully tested on model magnets of different geometries and made of different types of superconductor, CLIQ is now applied for the first time for the protection of a full-scale quadrupole magnet at the CERN magnet test facility. One aperture of a 3.4-m-long LHC matching quadrupole magnet is equipped with dedicated terminals to allow the connection of a CLIQ system. Experimental results convincingly show that CLIQ can protect this coil over the entire range of operating conditions. The complex electrothermal transients during a CLIQ discharge are successfully reproduced by means of a 2-D model. The test is part of the RD program of CLIQ quench protection systems, which has convincingly demonstrated the maturity of this technology and its effectiveness also for large-scale magnet systems. The proposed CLIQ-based solution for the quench protection of the LHC matching quadrupole magnet is now ready to be implemented in the LHC machine if needed.

Development of radiation tolerant components for the Quench Protection System at CERN

This paper describes the results of irradiation campaigns with the high resolution Analog to Digital Converter (ADC) ADS1281. This ADC will be used as part of a revised quench detection circuit for the 600 A corrector magnets at the CERN Large Hadron Collider (LHC) . To verify the radiation tolerance of the ADC an irradiation campaign using a proton beam, applying doses up to 3,4 kGy was conducted. The resulting data and an analysis of the found failure modes is discussed in this paper. Several mitigation measures are described that allow to reduce the error rate to levels acceptable for operation as part of the LHC QPS.

Analyses of the impact of connections’ layout on the coil transient voltage at the Quench Protection Circuit intervention in JT-60SA

The transient overvoltages associated to the interruption of high direct currents with high current derivative, at the base of the operation of a Quench Protection System for Superconducting Coils, have been studied, with particular reference to the JT-60SA project, which adopt edge technology solutions for current interruption: a Hybrid mechanical-static Circuit Breaker as main circuit breaker in series with a PyroBreaker as backup protection. The paper reports in particular on the analyses of the intervention of the backup circuit breaker in the final circuital conditions, considering the actual power connections that will be implemented on Site. The key elements which influence the peak value of the voltage and the relation existing among the different stray impedances of the circuit are identified, thus giving general guidelines for the design of the layout of the power connections. The specific case of JT-60SA is considered, but general criteria can be derived.

Accelerator-Quality HTS Dipole Magnet Demonstrator Designs for the EuCARD-2 5-T 40-mm Clear Aperture Magnet

Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The Enhanced European Coordination for Accelerator Research and Development (EuCARD-2) Work Package 10 is a collaborative push to take high-temperature superconductor (HTS) materials into an accelerator-quality demonstrator magnet. The demonstrator will produce 5 T stand alone and between 17 and 20 T when inserted into the 100-mm aperture of a Fresca-2 high-field outsert magnet. The HTS magnet will demonstrate the field strength and the field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using a multistrand Roebel cable that develops a stand-alone field of 5 T in a 40-mm clear aperture and discusses the challenges associated with a good field quality using this type of material. A selection of magnet designs is presented as the result of the first phase of development.

HTS Quadrupole for FRIB—Design, Construction and Test Results

This paper presents the outcome of significant magnet R&D that was started over a decade ago towards solving one of the most critical issues in the design of the Facility for Rare Isotope Beams (FRIB) and resulted in the successful demonstration of a full size prototype HTS quadrupole for the fragment separator region. This magnet will be subjected to unprecedented radiation and heat loads. An HTS quadrupole, with more than a 12 K margin over the nominal 38 K operating temperature, provides a unique solution. After briefly presenting the design and construction, the test results will be discussed in more detail. An advanced quench protection system was able to protect the magnet against an accident which caused thermal run away (or quench) is also discussed. The magnet uses a significant amount of HTS from two leading manufacturers. The successful demonstration should encourage the use of HTS magnets where one must deal with a large amount of radiation and/or energy deposition.

Voltage Characteristics of Diodes Used for Passive Quench Protection of Low-Current Magnets

Cold diodes and resistors in parallel with the coils are keys components in the passive quench protection system of low-current (high inductance) superconducting magnets. The diodes prevent current from flowing in the circuits that are in parallel with sections of the superconducting coil when the magnet is being charged or discharged. The use of diodes and resistors in parallel with the superconducting coil sections reduce the peak voltages to ground and, in some cases, the hot-spot temperature in the magnet during a quench. This paper presents measurements of the onset (low current) forward voltage of several power diodes as a function of temperature and magnetic field.

Study on No-Insulation HTS Pancake Coils With Iron Core for Superconducting DC Induction Heaters

This paper focuses on no-insulation (NI) HTS pancake coils with iron core for superconducting dc induction heaters. A superconducting coil without turn-to-turn insulation and its conventional counterpart with insulation are wound with YBCO-coated tapes. An iron core is built for a laboratory-scale dc induction heater. The electromagnetic characteristics of the two coils with the iron core are studied focusing on the charging and sudden-discharging processes at 77 K. Three variables are measured, i.e., current, terminal voltage, and magnetic field induced. The results show that NI coil with the iron core incurs a significant delay in the charging and discharging process due to the influence of the iron core. A terminal voltage pulse is observed at the beginning of the sudden-discharging process, which is more than five times of its normal value. A circuit-field coupled method is proposed to analyze the electromagnetic characteristics of the NI coil with an iron core. The results from experiment and simulation exhibits good agreement. The research shows that it is possible to use the NI technique to build a HTS iron core magnet for a dc induction heater, which can simplify the quench protection system.

Design of an asymmetric superconducting magnet for a Penning trap**Supported by National Natural Science Foundation of China (11302225)

A new 7.0 T asymmetric active shield superconducting magnet for Penning traps is proposed in this work. The magnet has two field regions whose homogeneity is better than 0.5 ppm. Linear and nonlinear methods are used for the asymmetric electromagnetic optimization. Stress analysis, mechanical design and a quench protection system design are also introduced in this paper.

Towards an Optimized Coupling-loss Induced Quench Protection System (CLIQ) for Quadrupole Magnets

The recently developed Coupling-Loss-Induced Quench (CLIQ) protection system is a new method for initiating a fast and voluminous transition to the normal state for protecting high energy density superconducting magnets. Its simple and robust electrical design, its lower failure rate, and its more efficient energy deposition mechanism make CLIQ often preferable to other conventional quench protection methods. The system is now implemented for the protection of a two meter long superconducting quadrupole model magnet and as such fully characterized in the CERN magnet test facility. Test results convincingly show that CLIQ allows for a more global quench initiation and thus a faster discharge of the magnet energy than conventional quench heaters. Nevertheless, the CLIQ performance is strongly affected by the length of the magnet to protect, hence an optimization is required for effective application to full-size magnets. A series of measures for the optimization of a quench protection system for a quadrupole magnet based on CLIQ is outlined here. The impact of various key parameters on CLIQ's performance, the most efficient CLIQ configuration, and the advantage of installing multiple CLIQ units are assessed.

Development of a Prototype Hybrid DC Circuit Breaker for Superconducting Magnets Quench Protection

A quench protection system for superconducting magnets mainly involves a mechanical dc circuit breaker (CB) and a dump resistor where the entire energy of the inductive magnet is dumped during quench. During the current commutation to the dump resistor, these mechanical CB experiences arcing at their contacts, which causes degradation in the performance as well as life expectancy of the CB, affecting the reliability of the entire quench protection system and appears as threat to the expensive and critical superconductor magnets also. A combination of mechanical and static breakers, which is termed a hybrid dc CB, presents a novel technique for arcless current commutation into the dump resistor. Furthermore, the current commutation time can also be reduced by adopting real-time switching schemes. A series of experiments has been done at the Magnet Technology Development Division Laboratory, Institute for Plasma Research, Gandhinagar, India, for testing the hybrid CB operation and operation at various current levels up to 800 A using a mechanical contactor as the mechanical CB and an insulated gate bipolar transistor as the static switch. A significant improvement in the voltage profile across the dump resistor has been observed using the hybrid CB exhibiting arcless current commutation into the dump resistor. Furthermore, an overall reduction in the current interruption time between a mechanical CB operation and a hybrid CB has been observed. The time for current commutation into the dump resistor with the conventional mechanical breaker is 48 ms, whereas that with the hybrid CB is observed to be 18 ms.

Protection Heater Delay Time Optimization for High-Field &lt;formula formulatype="inline"&gt; &lt;tex Notation="TeX"&gt;$\hbox{Nb}_{3}\hbox{Sn}$&lt;/tex&gt;&lt;/formula&gt; Accelerator Magnets

The US LARP collaboration has been pursuing the development of Nb3Sn technology for the interaction region low-beta quadrupole magnets for the future LHC luminosity upgrade. A key component for safe operation of these high-field magnets is the quench protection system. Due to the high stored energy density and the low stabilizer fraction in the conductor, quench propagation in the windings needs to be accelerated to limit the hot spot temperature and coil internal voltages during a quench. For this purpose, quench protection heaters are used to introduce multiple quenches across the windings. Heater delay, i.e. the time delay between heater activation and normal zone initiation under the heater, is a critical design parameter. We present an analysis of the heater delays characteristics for Nb3Sn coil windings based on our recently developed Code for Heater Delay Analysis (CoHDA), and compare with experimental results for various operational currents and temperatures in the LARP HQ and LQ magnets. We demonstrate applicability of our simulation model for heater design optimization of the LHC type low-beta quadrupole coils.

Fast Cycled Magnet Demonstrator Program at CERN: Instrumentation and Measurement Campaign

In an effort to develop economical magnets for an upgrade of the LHC injector complex, CERN started an R&D program on superconducting Fast Cycled Magnets (FCM) in 2009. One of the challenges in this program was to develop a test station, which started working in summer 2012 when the FCM dipole demonstrator was tested. The magnet contains several important features, like forced-flow cooling of supercritical He and it has a protection scheme based direct voltage measurement with co-wound voltage tap wires. In this paper we report on the cryogenic and powering requirements and operation, the quench protection system, the temperature and mechanical measurements. The functioning of the test station and instrumentation are evaluated and we will discuss the measurements on a detailed level.

New, Coupling Loss Induced, Quench Protection System for Superconducting Accelerator Magnets

A new and promising method for the protection of superconducting high-field magnets is developed and tested on the so-called MQXC quadrupole magnet at the CERN magnet test facility. The method relies on a capacitive discharge system inducing, during a few periods, an oscillation of the transport current in the superconducting cable of the coil. The corresponding fast change of the local magnetic field introduces a high coupling-current loss, which, in turn, causes a fast quench of a large fraction of the coil due to enhanced temperature. Results of measured discharges at various levels of transport current are presented and compared to discharges by quenching the coils using conventional quench heaters and an energy extraction system. The hot-spot temperature in the quenching coil is deduced from the coil voltage and current. The results are compared to simulations carried out using a lumped-element dynamic electro-thermal model of the so-called MQXC magnet developed with Cadence PSpice. The calculated voltages and currents are in good agreement with the measured data. Simulation and test results show that this new protection system, called coupling-loss induced quench, is a feasible method to reduce the hot-spot temperature in high-field superconducting magnets, even more when used in combination with conventional quench heaters.

Quench Voltage Analysis for a Long Superconducting Solenoids Group

A solid understanding and accurate analysis of the voltage transients in the quench process of superconducting magnets is the basis for verifying quench protection system design. This paper presents an analysis of the voltage spike that triggered a quench in a serially connected set of superconducting solenoid magnets, which are protected by a stack of cold diodes and dump resistors. The voltage development associated with the normal zone growth is analyzed. The magnets were trained close to the full design current and all the terminal voltages of the coils were captured by a specialized quench detection system. In the analyses described in this paper, the different stages of the voltage transient development will be detailed. Comparisons of simulations and the training results are provided to substantiate the mechanism of the quench voltage behavior in this passive protection scheme.

Quench Studies of YBCO Insulated and Noninsulated Pancake Coils

As a result of extremely high upper critical fields Bc2, high temperature superconductors (HTSs) have the potential to be used as high field insert coils in magnet systems where the background field is provided by low temperature superconductors (LTS). However, due to low quench propagation velocity in HTS as compared to LTS, the issue of developing a fast and reliable quench detection and protection scheme for such magnet systems remains a serious challenge. In order to provide a stable operation for HTS inserts, quench studies on YBCO coils were performed. Three single pancake coils were wound with 1.5 m of YBCO coated conductor provided by Superpower. They were equipped with quench initiation heaters and instrumented with type K thermocouples and voltage taps to monitor the development of the quench. Two of the coils were additionally insulated with a thin layer of polyimide film laid on top of YBCO CC. The heat propagation with no transport current was studied at 77 K and 4.2 K without an external magnetic field. Further tests included quench propagation at 77 K. The measurements involved voltages developed around the quenched region, hot spot temperature, and determining the threshold voltage to ensure the successful operation of the quench protection system.

Construction and test of a non-insulated insert coil using coated conductor tape

A small coated conductor coil (central field 1 T at 200 A) was constructed and tested in order to evaluate the benefit and the possible disadvantages of non insulated, double pancake construction, in particular regarding quench protection. The insert coil consists of three double pancakes without turn to turn insulation, and it was impregnated with beeswax. The coil was equipped with voltage taps on each pancake, thermocouples and a quench heater. Quench tests were carried out because quench protection is one of the main issues in developing coil technology for coated conductors. Quenches were induced either by a heater or by exceeding the coil critical current; in all cases the quench protection system was able to detect the quench.

Multi-Field Coupling Simulation on Quench Process in Superconducting Magnet

Quench protection system is a necessary part in superconducting magnets design. Rational design of quench protection system requires understanding of heat transfer and electromagnetic process in the magnet during quench process. A multi-field coupling model was developed to study quench process. This model sequentially solves two different physics environments, one is thermal physics environment, and the other one is electromagnetic physics environment. This model was applied to simulate one solenoid magnet in practical engineering. The main parameters results during quench process were presented. This research enriches the theory of numerical simulation on quench process of superconducting magnet, and provides theoretical guidance for the design of quench protection system.

Challenges and Design of the Transport Solenoid for the Mu2e Experiment at Fermilab

The Fermilab Mu2e experiment seeks to measure the rare process of direct muon to electron conversion in the field of a nucleus. The magnet system for this experiment is made of three warm-bore solenoids: the Production Solenoid (PS), the Transport Solenoid (TS), and the Detector Solenoid (DS). The TS is an “S-shaped” solenoid set between the other bigger solenoids. The Transport Solenoid has a warm-bore aperture of 0.5 m and field between 2.5 and 2.0 T. The PS and DS have, respectively warm-bore aperture of 1.5 m and 1.9 m, and peak field of 4.6 T and 2 T. In order to meet the field specifications, the TS starts inside the PS and ends inside the DS. The strong coupling with the adjacent solenoids poses several challenges to the design and operation of the Transport Solenoid. The coil layout has to compensate for the fringe field of the adjacent solenoids. The quench protection system should handle all possible quench and failure scenarios in all three solenoids. The support system has to be able to withstand very different forces depending on the powering status of the adjacent solenoids. In this paper, the conceptual design of the Transport Solenoid is presented and discussed focusing on these coupling issues and the proposed solutions.

Experimental Study for the Quench Protection System of the 9.4-T Whole-Body MRI Superconducting Magnet

The quench protection system with the circuit subdivision and heater network for a whole-body magnetic resonance imaging superconducting magnet has been designed. A test magnet with the similar quench protection design was built. Quench experiments for the test magnet have been conducted to verify a quench simulation code that is used to optimize the quench protection design. The fabrication of the test magnet has been demonstrated. The experimental results have been analyzed. The comparison between the experimental data and the calculated results has been discussed. The quench protection method with the heater network proves to work well, and the quench simulation code is proved to be reliable.