Numerical simulation of screening current distribution in HTS tape of high field magnet

An increasing number of magnetic resonance imaging (MRI) systems using high temperature superconductors (HTS) magnets have been designed and constructed, with detailed results of their performance now available. Features of REBCO and BSCCO conductors are described as they pertain to use in high homogeneity magnets, with emphasis placed on the practical use of these conductors in magnets. Methods of coil winding are discussed, in particular the differences between pancake and layer winding techniques. Design considerations for HTS magnets are presented in light of the difficulties presented by quench in these magnets, but also in terms of the features of HTS magnets afforded by their high operating temperatures, namely robust cryogen free operation and the potential to use unshielded gradient coils. Drawing on two example MRI systems, namely a 3 T BSCCO brain imaging magnet developed in Japan and a 1.5 T REBCO orthopaedic imaging system developed in New Zealand, the report details real-world stability and homogeneity of HTS-MRI systems, in particular with regards to the screening current effects observed in these systems. It is concluded that, apart from conductor cost, there are currently no technical obstacles to use of HTS-MRI systems.

Section: 24mentioning

confidence: 99%

Design considerations and experimental results for MRI systems using HTS magnets

Parkinson

2016

“…A key aspect in magnetic design are screening current effects, which degrade the magnetic field quality and stability [10], produce AC loss [21], and increase hoop and other mechanical stresses [22], which could cause delamination. Although the effect of screening currents has been widely studied in insulated HTS windings, both by two-dimensional (2D) cross-sectional models [21][22][23][24][25][26][27][28][29][30][31][32] and 3D models [33][34][35][36], there are few studies for NI or MI magnets. A highly remarkable work about screening currents in HTS inserts is the 3D modelling of [37].…”

Section: Introductionmentioning

confidence: 99%

Fast and accurate electromagnetic modeling of non-insulated and metal-insulated REBCO magnets

Pardo,

Fazilleau

2024

REBCO high-temperature superconductors are promising for all-superconducting high-field magnets, including ultra-high field magnets. Non-insulated (NI) and metal-insulated (MI) windings are a good solution for protection against electro-thermal quench. Design and optimization requires numerical modelling of REBCO inserts for high-field magnets. Here, we detail a fast and accurate two-dimensional (2D) cross-sectional model for the electromagnetic response of NI and MI coils, which is based on the Minimum Electro Magnetic Entropy Production (MEMEP). Benchmarking with an $A-V$ formulation method on a double pancake coil shows good agreement. We also analyse a fully superconducting 32 T magnet with a REBCO insert and a low-temperature superconducing (LTS) outsert. In particular, we analyze the current density, the screening curren induced field (SCIF), and the AC loss. We have shown that metal-insulated coils enable transfer of angular current in the radial direction, and hence magnet protection, while keeping the same screening currents and AC loss of insulated coils, even at relatively high ramp rates of 1 A/s. Surprisingly, soldered coils with low resistance between turns present relatively low AC loss for over-current configuration, which might enable higher generated magnetic fields. The numerical method presented here can be applied to optimize high-field magnets regarding SCIF in MI or NI magnets. It also serves as the basis for future electro-thermal modelling and multi-physics modeling that also includes mechanical properties.

“…To protect high-field HTS magnet from excessive stress concentration, the screening current behaviors have been discussed [22]. So far, a few screening current simulation methods have been proposed, which include: (a) an axisymmetric finite element method (Axi-FEM) [23,24]; (b) a finite element method with a thin film approximation technique (FEM + TFA) [15,[25][26][27][28]; (c) a simple equivalent circuit (SEC) model [29]; and (d) an advanced partial element equivalent circuit (A-PEEC) model which is shown for an SC simulation in this paper.…”

Section: Introductionmentioning

confidence: 99%

A newly developed screening current simulation method for REBCO pancake coils based on extension of PEEC model

Noguchi¹,

Hahn²

2022

Self Cite

Since the screening current (SC) in rare earth-barium-copper-oxide (REBCO) coated conductor (CC) generates an undesired magnetic ﬁeld, it must be accurately estimated, especially for magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR). Moreover, in recent years, it was pointed out that the screening current enhanced the stress/strain in REBCO CC, when an REBCO magnet was operated as an insert under an ultrahigh magnetic ﬁeld. The previously reported SC simulation methods may be roughly categorized into ﬁnite element method (FEM) and equivalent circuit method. The FEM-based method often adopted an axisymmetric model or a thin ﬁlm approximation model, while the circuit-based are the simple equivalent circuit model and the network equivalent circuit model, so-called the partial element equivalent circuit model. The latter is newly proposed in this paper. Features of those SC simulation models are brieﬂy compared to each other in this paper. Each SC simulation models have pros & cons. We have to adequately chose an SC simulation model depending on a purpose. In addition, we propose a new developed SC simulation model, named the advanced partial element equivalent circuit (A-PEEC) model. It is extendable to an SC simulation of no-insulation REBCO pancake coils. To simulate the SC of a simple coil model and the LBC3 magnet, we investigated the screening current distribution maps, and the simulated screening current-induced ﬁelds were compared with the measurements. We have conﬁrmed the validity of the newly proposed A-PEEC model.