Construction and test result of an all-REBCO conduction-cooled 23.5 T magnet prototype towards a benchtop 1 GHz NMR spectroscopy

The REBCO high-temperature superconducting tape has a pronounced electromagnetic anisotropy. The critical current is strongly dependent on the value of the magnetic field, the magnetic field direction, the temperature, and the stress, and has a significant nonlinear relationship. It is also important to note that screening current effects in superconducting magnets at elevated temperatures lead to a non-uniform distribution of current densities, and thus the inductance of superconducting magnets at high-temperatures is calculated differently from that of normal magnets. This is essential for the design of superconducting energy storage magnets at high-temperatures, especially for the accurate evaluation of the inductance values. To further analyze the variation of the inductance value due to the REBCO screening current, the T-A formulation combined with the magnetic energy density is considered to evaluate the energy storage and inductance values during the excitation of the superconducting coil. The effect of excitation rate, operating temperature, and excitation current on the inductance value is analyzed based on the design of a 5T insulating superconducting coil. The mathematical relation between excitation voltage, contact resistance, and inductance in the magnetic excitation experiment is presented, and the accuracy of the calculated method is verified by comparison with simulation results.

Section: Calculation Of Superconducting Magnets Inductance Valuementioning

confidence: 99%

Section: Effect Of Temperature On Superconducting Inductancementioning

confidence: 99%

A method to evaluate the inductance properties of REBCO excitation process based on magnetic energy density and T–A formula

Hong

et al. 2023

“…To construct a dry-wound NI dipole magnet, it is necessary to consider the material and structure of the bobbin, considering the thermal contraction and cooling efficiency, and a supporting structure that prevents deformation of the straight part may be required. Additionally, the effect of nonuniform current density can be mitigated by techniques such as current sweep reversal [63] or temperature-controlled charging sequence [64] and the passive shimming method [65] can also be effective to correct the field inhomogeneity.…”

Section: Effect Of Current Distribution and Shape Deformation On Magn...mentioning

confidence: 99%

Investigation on nonuniform current density and shape deformation affecting the magnetic field performance of a saddle-shaped no-insulation HTS cosine–theta dipole magnet

Kim

Park

Bang

et al. 2023

In particle accelerators, high magnetic fields are desirable for discovering new particles. Dipole magnets using superconductors have played a key role in creating required field intensity and uniformity. In contrast, high temperature superconductor (HTS) dipole magnets have recently been spotlighted because of their ability to generate higher magnetic fields compared to their low temperature superconductor counterpart. Similar needs have emerged in other fields using magnets, and no-insulation (NI) technology is considered a feasible option to reach high magnetic fields by overcoming the disadvantages of HTS magnets. However, research has rarely been carried out on the utilization of NI HTS magnet technology for dipole magnets in high-field accelerators. Here we show the design, fabrication, and test results of an NI HTS dipole magnet with numerical analysis results. This paper aims to investigate the effect of nonuniform current density and undesirable shape deformation on the magnetic field distribution of a saddle-shaped NI HTS dipole magnet. The magnet is designed and constructed considering the 'constant perimeter winding' technique and tested in liquid nitrogen. The field mapping process is also performed along a designated mapping trajectory to obtain a magnetic field distribution. T-A formulation-based simulation model, named 'sequential simulation model,' is suggested to reproduce measurements and employed considering current distribution and shape deformation. As a result of quantitative analysis of the transverse direction measurement results, the magnetic field error decreased by 0.02 percent point (pp) when the nonuniform current density is considered. It decreased by 0.13 pp when the shape deformation is considered. Moreover, the critical current calculated through additional numerical analysis shows an error of up to 10%. In conclusion, the saddle-shaped NI HTS dipole magnet can produce a sufficient magnetic field level for particle accelerator research, even though the field distribution shows a uniformity of 0.37% within this study.

“…89]. A small solder-impregnated NI pancake stack tested by TE in 2019 achieved stable quench-safe operation above 24 T peak field on coil at 21 K, with an average J wp over 700 A mm −2 [90]. It is believed that this technology can be scaled up using a novel turn-turn insulation combining high thermal conductivity with the ability to choose the resistance between turns, thus retaining a high J wp without compromising quench protection.…”

Section: Current and Future Challengesmentioning

confidence: 99%

Superconductors for fusion: a roadmap

Mitchell

Zheng

Vorpahl³

et al. 2021

110

With the first tokamak designed for full nuclear operation now well into final assembly (ITER), and a major new research tokamak starting commissioning (JT60SA), nuclear fusion is becoming a mainstream potential energy source for the future. A critical part of the viability of magnetic confinement for fusion is superconductor technology. The experience gained and lessons learned in the application of this technology to ITER and JT60SA, together with new and improved superconducting materials, is opening multiple routes to commercial fusion reactors. The objective of this roadmap is, through a series of short articles, to outline some of these routes and the materials/technologies that go with them.