Analysis of quench in the NHMFL REBCO prototype coils for the 32 T Magnet Project

Abstract

A 32 T all-superconductive magnet with high field REBCO inner coils is under development at the National High Magnetic Field Laboratory, Tallahassee, Florida, USA. As part of the development activity, two prototype coils with full scale radial dimensions and final design features, but with reduced axial length were constructed. The prototype coils consist of six dry-wound double pancakes modules with uninsulated conductor and insulated stainless steel cowind. Quench studies on one of the prototype coils at 4.2 K in self-field and in a background magnetic field of 15 T were performed by activating a set of quench protection heaters. In this paper, we present a numerical analysis of the experimental results of the quench tests of one of the prototype coils. The numerical analysis was carried out through a coupled electro-thermal FEM model developed at the University of Bologna. The model is based on the coupling with distributed contact resistances of the coil pancakes described as 2D elements. A homogenization procedure of the REBCO tape and other coil materials is presented, which allows reducing the number of degrees of freedom and the computational effort. The model is applied to the analysis of the current and voltage evolutions during the experimental quench tests on the prototype coil.

Quench Detection and Protection for High-Temperature Superconductor Accelerator Magnets

“…Since their initial discovery in 1986, high-temperature superconductors [1] have made a long way toward practical use in applications, such as record-field solenoids [2][3][4], energy storage [5], fault current limiters [6][7][8] and transmission lines [9,10]. More demanding applications, such as high-field magnets for particle accelerators, are presently on the horizon [11][12][13][14][15], where HTS conductors will operate close to their stress limits, and will have to satisfy necessary mechanical, electromagnetic and thermal stability criteria.…”

A Numerical Study of Quench in the NHMFL 32 T Magnet

“…The electromagnetic-thermal quasi-3 D FE quench model of the insert HTS coils is coupled with the magnet lumpedparameter electrical circuit model that also describes the inductive coupling between the dual coil insert and the multisection outsert. A detailed description of the model is provided in [5] [6].…”

“…The applied homogenization procedure enables one to determine the circumferential electrical conductivity in azimuthal direction. Based on the same approach, both circumferential and transversal thermal conductivities are computed [5], [6].…”

“…The code was validated first by analyzing the test results of the prototype coils. Particularly, the quench propagation was studied in the insert prototypes in self-field and in a background magnetic flux density of 15 T generated by a large bore resistive magnet of the NHMFL [5]. Then, the insert prototypes coupled with the actual LTS outsert were analyzed to determine the overall specific quench behavior of coupled HTS and LTS magnets [6].…”

Electromagnetic modelling using T‐A formulation for high‐temperature superconductor (RE)Ba 2 Cu 3 O x high field magnets

“…Therefore, REBCO conductor is also called high field superconductor [8,9]. Significant process has been achieved on HTS high field magnets in recent 5 years: 32 T field was achieved in 2017 by a LTS/HTS hybrid magnet with a 17 T REBCO insert and 15 T LTS outset in National High Magnetic Field Laboratory (NHMFL), USA [9][10][11]. A 24 T LTS/HTS hybrid magnet with 9 T insert HTS magnet was developed by the Chinese Academy of Sciences in 2015 [12][13][14][15][16].…”