Structural Modeling of HTS Cable-in-Conduit Conductor With Helically Slotted Aluminum Core for High-Field Magnet Applications

The benefits of operating fusion devices, such as tokamaks and stellarators, at high fields make high-temperature superconducting magnets necessary to realize a compact fusion power system. Superconducting stellarators, such as W7-X, have used standard low-temperature superconductor technology (NbTi). ARPA-E has recently funded a 2-year project led by the startup Type One Energy and involving the Fusion Technology Institute at the University of Wisconsin–Madison, the Plasma Science to design and fabricat the first non-planar HTS (REBCO) coil for a high-field stellarator based on the SPARC tokamak’s VIPER cable concept. The design consists of a 1.5-turn non-planar REBCO coil supported by a pair of 3D printed stainless steel radial plates. The ultimate goals of the project are to determine if commercial REBCO tapes and additive manufacturing can be used to fabricate high field (≥ 10 T) non-planar coils with tight bending radii (≃ 100 mm) and with a degradation of the critical current smaller than 20 % with respect to the expected performance. In this work we present numerical analysis for non-planar coils (critical current, magnetic fieldmap, Lorentz forces and quench aspects) at the operating conditions of 77 K and 20 K and the fabrication and testing in liquid nitrogen (77 K) of the first two non-planar demonstrators for stellarators based on a VIPER cable. The first demonstrator is a short NOn-planar VIPER cabLe (cable demonstrator at which we will refer to as (NOVEL) equipped with 100 HTS REBCO tapes and with a critical current of 5700 A at 77 K (self-field); the second is a MultIple turns (1.5-turns) NOn-plANar coil (coil demonstrator at which we will refer to as MINOAN) equipped with 30 HTS tapes and with a critical current of 2100 A at 77 K (self-field). Both demonstrators were tested at 77 K (liquid nitrogen bath) and the results showed that - even after being bent into non-planar shapes with bend radii ≃ 100 mm - the degradation of the critical current Ic was within 15 %, meeting the expected goals of the project.

Section: Magnetic Field and Structural Supportsupporting

confidence: 91%

Section: Magnetic Field and Structural Supportmentioning

confidence: 99%

Section: Magnetic Field and Structural Supportmentioning

confidence: 99%

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Development of the first non-planar REBCO stellarator coil using VIPER cable

Riva,

Granetz,

Vieira

et al. 2023

“…This sample has been analysed in two configurations with one and with two HTS stacks, each comprised of 20 tapes (see details in table 1). Since this sample was not jacketed, the electric contact between adjacent tapes is expected to be characterized by a higher resistance than the usual condition in jacketed cables ranging in between 0.36 and 2 µΩ m [50][51][52][53][54]. The samples self-field I c values have been evaluated in both configurations (one and two HTS stacks) by recording the V-I curves in LN2 bath.…”

Section: Samples and Experimental Detailsmentioning

confidence: 99%

Experimental and numerical studies on current distribution in stacks of HTS tapes for cable-in-conduit-conductors

Marzi¹,

Celentano²,

Augieri³

et al. 2021

Self Cite

Cable-in-conduit conductors comprised of twisted stacks of high-temperature superconducting (HTS) tapes constitute a very promising technology by virtue of their easy manufacturing process, flexibility capabilities, and high current densities. In a cable, the current distribution among tapes is one of the key parameters affecting the cable performances. The distribution of current is affected mainly by the self-field configuration (ultimately related to the cable layout) and the termination resistances. In this paper we present a 2D finite element (FE) model, based on the T-A formulation, which computes the magnetic field and current distribution in stacked tapes. This model has been used to describe the experimental V–I results obtained in cables in which different current distributions among tapes are expected. The first case refers to V–I curves of stacks of HTS tapes inserted into ducts formed in the extruded aluminium cylindrical core for a straight cable. The excellent agreement between the experimental findings and the simulation results can be explained in terms of uniform current distribution within the tapes stack, up to the superconducting to normal transition. The second sample, an Al-slotted core Cable-In-Conduit-Conductor, has been bent down to a radius of 0.15 m, and from the measured V–I characteristic of each individual tape, a different tape degradation depending on the tape position within the stack was recorded. The model is able to reconstruct the V–I of the stacks from the characteristic curves of the individual tapes with a satisfactory agreement. The finite element analysis reveals non-uniform current distribution among the tapes, which could expose the cable to a potentially irreversible damage during operation. The proposed FE model constitutes a useful tool for the analysis and predictions of HTS CIC conductor performances and represents a suitable basis for the implementation of more complex models aimed at the design of specific and large applications of this conductor in the next future.

“…The electromechanical properties of the tapes were tested at 77 K in a self-field under a bending load, showing that the I c starts to decrease at a strain of about 0.4%-0.7% [14]. In order to explain the effect of mechanical deformation on the current-carrying capacity of REBCO tapes, several theoretical and numerical studies have been carried out to obtain the strain on the REBCO layer at different bending radii [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Bending characteristics of stacked REBCO cable under different stacking modes

Yuan

Dai

et al. 2023

High-temperature superconducting (HTS) tapes provide new materials for various high-current applications. The stacked tape cable (STC) is one of the promissing structure, which is based on the idea to stack single REBCO tapes. However, stacking the tapes increases the thickness of the cable and reduces its bending performance. In order to study the bending behavior of stacked tapes, bending tests of single tape was first made to analyze the strain of the REBCO layer at different bending radii, and the strain-current curves were obtained by empirical equations. The cables were stacked in both back-to-back and face-to-face modes. The strains of the REBCO layers in the tapes are calculated, and the critical currents of the cables are experimentally measured at various bending radii. The bending characteristics of the cable are analyzed using the fitted equation, and the experimental results demonstrate good agreement with the calculated results. The results indicate that the REBCO layer exhibits improved bending performance under compression, and thinner cables perform better. Therefore, we added copper tape to adjust the position of the neutral axis to optimize the bending performance. The results show that this method can effectively reduce the bending radius of the stacked cable.