Degradation Characteristics of a 20 T REBCO Insert Magnet After a 4.2 K Standalone Test

“…35 T [4]. The 20 T all-REBCO magnet, which included a 15 T noinsulation REBCO insert and a 5 T metal insulation REBCO coil, was developed and tested in 2023 [5].…”

Section: Lt01)mentioning

confidence: 99%

mentioning

confidence: 99%

Successful development of an iron-based coated conductor magnet

Zhang

2024

“…The weak point can be located at REBCO turns [24,25] or the current terminals [26]. Once the operation current at the weak point reaches the critical level, the risk of thermal runaway rapidly increases, leading to a quench accident and causing severe damage to REBCO magnets [22,27,28].…”

Section: Introductionmentioning

confidence: 99%

Experimental study on screening-current induced strain in REBCO insert coils: under critical current control and operation current cycles

Shao,

Zhang,

Xin

et al. 2024

Self Cite

The screening-current effect is an inhomogeneous distribution of current density inside the REBCO conductors. The additional strain induced by the screening current, known as screening-current induced strain (SCS), is considered to affect the structural integrity of REBCO windings, especially when operating high-field REBCO insert magnets. In this work, we wound and tested a series of 50-turn REBCO coils inside a 10 T LTS external to investigate the influencing mechanism of multiple electromagnetic factors on SCS. We varied the critical current in different coils by different heat treatment procedures. Each coil was tested individually, experiencing a external field cycle and multiple operation current cycles at constant external fields. The extreme scenario for each coil was being energized to 400 A while the external field was 10 T. We adapted the discrete-coupled model to estimate the hoop strain distribution, monitored the experimental results by multiple strain gauges at the outermost turn. Test coil with a lower critical current endured a lower maximum hoop strain. When we were energizing the test coils, hoop strain increased at the edge of REBCO tapes while remaining nearly constant in the middle region. Additionally, the maximum hoop strain at the outermost turn decreased after each excitation cycle. This work could be an experimental reference for optimizing the electromagnetic design and the excitation scheme during the development of high-field REBCO magnets.

“…The radial current path can help reduce Joule heat in the spiral normal zone to avoid the local overheating phenomenon and burnout accidents. Owing to this self-protecting nature, the NI technique has attracted considerable attention from superconducting magnet designers and many NI magnet projects have been accomplished [1][2][3][4][5][6][7] or in progress [8,9]. Other variants of no-insulation magnets including 'metal as insulation (MI)' [10,11] and 'intra-layer noinsulation (LNI)' [12,13] have also been constructed.…”

Section: Introductionmentioning

confidence: 99%

Quench analysis of a no-insulation REBCO magnet based on the ADI method considering the coupling effect of the cryostat

Zheng,

Liu,

Song

et al. 2023

A no-insulation (NI) REBCO superconducting magnet is under development at Wuhan National High Magnetic Field Center, China. The magnet with the liquid helium cryostat system has a compact structure to reduce the space required for operation. During a quench, the fast-changing spatial magnetic field around the NI magnet may induce a strong eddy current in the conductive parts of the cryostat. The eddy current and its associated Lorentz force will generate mechanical stress on the cryostat, especially on the thermal shield (TS). The mechanical strength of the cryostat needs verification in the preliminary design. Furthermore, the degree to which the electromagnetic coupling between the cryostat and NI magnet might impact the quench behaviors of the NI magnet remains uncertain. In this paper, a multi-physics quench model is newly developed for the NI REBCO magnet, and the alternating direction implicit method is employed for the solver of the thermal model to improve computational efficiency. This simulation model can consider the electromagnetic coupling effect between the NI magnet and cryostat by constructing a partial element equivalent circuit. A quench analysis has been performed and we found that: (1) The cryostat can function as a secondary shorted circuit to the NI magnet and slow down the quench speed to a certain extent. (2) During the rather fast inductive quench phase, the cryostat will experience an attraction force towards the quench propagation frontier. (3) A quench propagation from one end of the magnet can cause a significant z-axis unbalanced force on the TS. (4) Cryostat materials with drastically changed electrical conductivity can significantly affect their mechanical responses during a quench. However, the eddy current density and maximum Von Mises stress on the TS are barely affected by the thickness of the TS and the contact resistance of the NI REBCO magnet.