Effect of Local Defects on HTS Fusion Magnets Performance

Zappatore, Andrea; Bonifetto, Roberto; Zanino, Roberto; Sarasola, Xabier

doi:10.1109/tasc.2022.3169718

Cited by 7 publications

(2 citation statements)

References 19 publications

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“…Different discretization strategies have been adopted for the HTS and LTS layers. A similar setup was already presented and used for quench analysis in [27].…”

Section: A Th Model Equations Setup and Parametersmentioning

confidence: 99%

Impact of Hysteresis Losses in Hybrid (HTS-LTS) Coils for Fusion Applications

Zappatore,

De Marzi,

Uglietti

2023

IEEE Access

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Several conductor designs featuring High Temperature Superconducting (HTS) stacked tapes for fusion coils are being proposed. These conductors are planned to operate in time-varying magnetic field and current; thus, the estimation of AC losses is fundamental for the conductor design and the accurate analysis of its performance in operation. The case study of an HTS conductor proposed for the hybrid (HTS-LTS) Central Solenoid coil for the EU DEMO tokamak is considered in this work. Here, a numerical model based on the finite element method (FEM) and the H-formulation is used, in order to estimate the hysteresis losses. The FEM model is first benchmarked against available analytical formulae as well as available literature data. Then it is applied to the real case operational scenario. It is shown that for the conductor design analyzed, the coupling losses are orders of magnitude lower than the hysteresis ones. The impact of the hysteresis+coupling losses on the temperature margin of the coil is assessed with a thermalhydraulic model. It is shown that the heat generated in the HTS layers is partially transferred to the LTS layers, leading these layers to quench. An alternative conductor concept is also analyzed, showing that, however, in the top and bottom modules of the CS coil, due to the bending of the magnetic field, a too large heat deposition is present.

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“…Different discretization strategies have been adopted for the HTS and LTS layers. A similar setup was already presented and used for quench analysis in [27].…”

Section: A Th Model Equations Setup and Parametersmentioning

confidence: 99%

Impact of Hysteresis Losses in Hybrid (HTS-LTS) Coils for Fusion Applications

Zappatore,

De Marzi,

Uglietti

2023

IEEE Access

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“…Quench considerations on HTS fusion conductors have mostly focused on the development of numerical models (see [33][34][35]). The case of graded EU DEMO CS was also analyzed recently in [36]. Although the predicted quench performance is often found to be acceptable, the analyses are inevitably prone to certain modeling assumptions such as lumped-element geometry, fixing the thermal coupling parameters, voltage-current transition metrics and quench detection characteristics.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of stability, quench propagation and detection methods on 15 kA sub-scale HTS fusion conductors in SULTAN

Bykovskiy

Bajas

Dicuonzo

et al. 2023

Supercond. Sci. Technol.

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High-temperature superconductors (HTS) enable exclusive operating conditions for fusion magnets, boosting their performance up to 20 T generated magnetic fields, in the temperature range from 4 K to 20 K. One of the main technological issues of the HTS conductors is focused on their protection in the case of a thermal runaway (quench). In spite of extremely high thermal stability of HTS materials, quench is still possible due to local defects along the conductor length or insufficient cooling. In such cases, the high stability results in slow propagation of a resistive zone. Thereby, risky hot-spot temperature (>200 K) can be reached, if applying conventional quench detection methods at the voltage threshold of 0.1 – 0.5 V, typical for fusion magnets. Aiming at experimental study of the phenomenon, a series of sub-scale 15 kA 3.6 m long conductors based on stack of tapes soldered in copper profiles are manufactured at Swiss Plasma Center, including twisted ReBCO and BiSCCO triplets, non-twisted and solder-filled ReBCO triplets, as well as indirectly cooled non-twisted ReBCO single strand. Applying either increasing helium inlet temperature, overcurrent operation or energy deposited by embedded cartridge heaters, critical values of the electric field and temperature are evaluated for a given operating current (up to 15 kA) and background magnetic field (up to 10.9 T). Once quench is actually triggered, the quench propagation is studied by distributed voltage taps and temperature sensors able to monitor the external temperature of the jacket and internal one of the conductor (helium or copper). Thanks to the recent upgrade of the SULTAN test facility, quench propagation in the conductors is measured up to the total voltage of 2 V and peak temperature of 320 K. Furthermore, novel quench detection methods based on superconducting insulated wires and fiber optics are also instrumented and studied. Summary of the test samples, their instrumentation and corresponding test results is presented in this work.

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