An analytical model for coupling losses in large conductors for magnetic fusion

Duchateau, J.L.; Turck, B.; Torre, A.; Zani, L.

doi:10.1016/j.cryogenics.2021.103374

Cited by 10 publications

(5 citation statements)

References 19 publications

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“…Without wrapping (that is our case), the inter-petal transverse resistance is of the same order of magnitude as the intra-petal transverse resistance, so that the last cabling stage dominates the loss behaviour, because coupling currents with large loops flow through neighbouring petals. In particular, the coupling time constants are dominated by the twist pitches of the last cabling stages [39,40], which have similar values for the two legs.…”

Section: Ac Lossesmentioning

confidence: 99%

DTT toroidal field conductor samples test in Sultan: DC and AC characterization

Fiamozzi Zignani,

De Marzi,

Scarantino

et al. 2024

Supercond. Sci. Technol.

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The superconducting magnet system of the Divertor Tokamak Test (DTT) facility, composed of 18 Toroidal Field (TF) coils, 6 Poloidal Field (PF) coils and a Central Solenoid (CS), has been designed and many procurements have been launched. Some manufacturing aspects and some conductor features require characterization under relevant close-to-operative conditions. To confirm the design choices in all details, cryogenic tests in qualified facilities have been foreseen. In this work, the results of the TF samples characterization at the SULTAN facility at the Swiss Plasma Centre (SPC, EPFL) are presented. The 3 weeks test campaign started on July the 8th, 2022. The DTT TF SULTAN sample was made of two Nb3Sn Cable-in-Conduit conductor “legs”, namely “TF-A” and “TF-B”, made with wires produced by Kiswire Advanced Technology (KAT), differing for the cabling twist pitch sequence only, and designed to work in DTT at 42.5 kA at 11.9 T peak field.The extensive characterization comprised 3000 Electro-Magnetic (EM) cycles and two Warm-Up-Cool-Down (WUCD) steps, and in detail it included: AC measurements on the virgin conductors, on cyclic loaded conductors and after WUCDs; DC tests at 10.85 T / 42.5 kA with intermediate electro-magnetic (EM) cycles at 10.85 T / 45 kA before and after WUCDs; DC tests using partial Lorentz force loads, and Minimum Quench Energy (MQE) tests at 9 T / 42.5 kA after cycles and WUCDs. The results of the DC measurements analysis verified the design, in terms of current sharing temperature (Tcs) and critical current (Ic), as both samples are over the minimum acceptance values. In particular, the “TF-A” sample, characterized by a so-called “long twist pitch” cabling sequence, showed higher performance without any degradation with loading and WUCD cycles, whereas sample “TF-B” presented an initial Tcs reduction that afterwards substantially remained unchanged. In terms of strain acting at the Nb3Sn filaments level, this result can be described by a lower effective strain in the “TF-A” sample. AC losses were measured with a calorimetric method as a function of frequency for each series of AC sinusoidal pulsing measurements, and the characteristic coupling time constants were determined.

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Section: Ac Lossesmentioning

confidence: 99%

DTT toroidal field conductor samples test in Sultan: DC and AC characterization

Fiamozzi Zignani,

De Marzi,

Scarantino

et al. 2024

Supercond. Sci. Technol.

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“…The AC losses in the CICCs in operation are often computed through analytical models in which the coupling loss power density per-unit-volume depends on single or multiple time constants of the different coupling loops (see [17,37]). A detailed description of the model and of the time constants associated to AC losses in the CS conductors can be found in [38] and [39].…”

Section: Ac Lossesmentioning

confidence: 99%

Performance tests of ITER CS conductor samples from series production

Breschi

Devred

Macioce

et al. 2023

Supercond. Sci. Technol.

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The ITER magnet system is one of the most sophisticated superconducting magnet systems ever designed, with a stored energy of 51 GJ. The coils are wound from Cable-in-Conduit Conductors (CICCs) made of superconducting and copper strands assembled into a multistage rope-type cable, inserted into a conduit of austenitic steel tubes. The ITER Central Solenoid (CS) works in pulsed mode, reaching a peak field of 13 T, thus allowing the induction of a high intensity current in the plasma of the ITER tokamak. This magnet consists of a stack of six modules which include around 125 t of Nb3Sn strands. The production of all CS conductors has been completed and module manufacturing is well underway; throughout the production phase, samples were cut at the extremities of the conductor unit lengths to undergo quality control tests. About 25% of the conductor short samples were tested in current and field at cryogenic conditions at the SULTAN facility in Villigen, Switzerland. This work reports the comparative analysis of the short samples set of test results.

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“…They are set equal to 3 × 10 8 𝑆/𝑚 for both stage and for any (𝛾 1 , 𝛾 2 ) combination. In this paper, the cable is compacted due to the effective geometrical parameters, thus, we adapted the inter-stage conductances to obtain magnetic coefficients values (∑ 𝑛𝜅 𝑖 𝜏 𝑖 ) in line with data from bibliography [4].…”

Section: B Tomographic Data As Model Inputsmentioning

confidence: 99%

“…In this paper, we consider the coupling losses for a 2-stage configuration with the two highest stages of the cable. In a similar way as in MPAS [3]- [4], each stage is defined by two magnetic coefficients: a shielding coefficient, 𝑛𝜅 and a time constant, 𝜏. We present the method used to determine effective geometrical parameters (cabling radii and twist pitches) of the cable.…”

Section: Introductionmentioning

confidence: 99%