arXiv subjects

Tara Benkel

Publications and source records attributed to Tara Benkel.

4 recordsLinked to original sources

arXiv2026

A fully coupled electromagnetic-thermal-mechanical model for metal-insulated HTS high field magnets

Ultra high field REBCO magnets operate under strongly coupled electromagnetic, thermal and mechanical conditions, where screening currents, localized heating, thermal expansion and Lorentz forces can modify both the structural state and the critical current density of the conductor. In this work, a coupled electromagnetic, thermal and mechanical model is developed for a metal-insulated nested REBCO insert designed for a 40 T class SuperEMFL magnet. The existing electromagnetic formulation resolves the non-uniform screening currents in the REBCO tapes. The thermal model is extended from an explicit Finite Difference Method (FDM) to an implicit Backward Euler scheme with Picard iteration, while a new axisymmetric mechanical FDM solver based on BiCGSTAB is introduced to calculate displacements, strains and stresses in the coil windings and G10 spacer regions. Thermal expansion and Lorentz force contributions are included, and the calculated longitudinal mechanical strain is coupled back to the electromagnetic model through a strain dependent critical current density, which also depends on temperature, magnetic field, and its orientation. A literature-informed Parabolic-Weibull model is used to model reversible and irreversible strain degradation of the REBCO conductor. The numerical methods are benchmarked, and the resulting framework provides a computationally efficient approach for investigating temperature gradients, thermo-mechanical stresses, strain-dependent critical current degradation and quench behaviour in full scale nested high field REBCO magnets.

physics.app-ph↗

arXiv2025

Modelling of a large-scale non-insulated non-planar HTS stellarator coil using Quanscient Allsolve

Stellarators present features such as steady-state operation and intrinsic stability that make them more attractive than tokamaks in their scaling to fusion power plants. By leveraging more possible configurations, stellarators can be optimized for better engineering feasibility, e.g., resilience to manufacturing tolerances, reduced mechanical load on conductor, material optimization, cost of fabrication. Finite Element Analyses are crucial for the design and optimization of High-Temperature Superconducting (HTS) REBCO non-planar coils. However, accurate simulation of large-scale magnetostatic, mechanical, and quench models can take days or even weeks to compute. In this work, we present a model of a real-size, HTS, non-insulated, non-planar stellarator coil and perform in Quanscient Allsolve, a transient simulation study including modelling quench, using the $H-φ$ formulation. It is shown that transient model benefits heavily from the built-in Domain Decomposition Method (DDM), which allows reaching reasonable computation times. Such models become then invaluable in predicting and understanding the complex behavior of non-insulated large-scale REBCO magnets, including their intrinsic energy imbalance.

physics.plasm-ph↗

arXiv2020

Electromagnetic Modeling of Superconductors with Commercial Software: Possibilities with Two Vector Potential-Based Formulations

In recent years, the $H$ formulation of Maxwell's equation has become the de facto standard for simulating the time-dependent electromagnetic behavior of superconducting applications with commercial software. However, there are cases where other formulations are desirable, for example for modeling superconducting turns in electrical machines or situations where the superconductor is better described by the critical state than by a power-law resistivity. In order to accurately and efficiently handle those situations, here we consider two published approaches based on the magnetic vector potential: the $T$-$A$ formulation of Maxwell's equations (with power-law resistivity) and Campbell's implementation of the critical state model. In this contribution, we extend the $T$-$A$ formulation to thick conductors so that large coils with different coupling scenarios between the turns can be considered. We also revise Campbell's model and discuss it in terms of its ability to calculate AC losses: in particular, we investigate the dependence of the calculated AC losses on the frequency of the AC excitation and the possibility of using quick one-step (instead of full cycle) simulations to calculate the AC losses.

cond-mat.supr-con↗

arXiv2019

T-A Formulation to Model Electrical Machines with HTS Coated Conductor Coils

Modelling high temperature superconductor (HTS) motors remains challenging mainly due to the high aspect ratio of these conductors but also because of the properties of the magnetic materials. This paper presents a 2D time dependent model to assess the AC losses of superconducting motors based on the new T-A formulation, which by using Finite Element Methods (FEM), allows its implementation in commercial software. The T-A formulation computes the magnetic flux density with different Maxwell's equations depending on the areas of the motor and makes it possible to use the thin strip approximation i.e. the HTS tapes are modelled as infinitely thin lines. The model is then expected to tackle the high aspect ratio of the HTS as well as decreasing both the mesh complexity and the computing time. The first objective of the paper is to validate the method in 2D by evaluating the AC losses of a specific synchronous motor called SUTOR; the computed results are compared with good agreements to those assessed with the MEMEP method, already validated. In a second part, the same losses are computed, taking into account the anisotropy of Jc with the implementation of a data set based on experimentally measured Ic at 65 K and 77 K.

cond-mat.supr-con↗