Metal-as-insulation variant of no-insulation HTS winding technique: pancake tests under high background magnetic field and high current at 4.2 K

Lécrevisse, Thibault; Badel, Arnaud; Benkel, Tara; Chaud, X.; Fazilleau, Philippe; Tixador, Pascal

doi:10.1088/1361-6668/aab4ec

Cited by 60 publications

(26 citation statements)

References 24 publications

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“…Furthermore, there are more and more concerns about the mechanical damage of HTS magnets [30][31][32][33][34]. The delamination has been observed in superconductor tapes after the quench of the magnet [35]. Moreover, large hoop stress is generated by the prestress and strong electromagnetic force in a high magnetic field, which may affect the critical current of the coils [36,37].…”

Section: Introductionmentioning

confidence: 99%

Ramping loss and mechanical response in a no-insulation high-temperature superconducting layer-wound coil and intra-layers no-insulation coil

Liu

Yong

2021

Sci. China Technol. Sci.

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The layer-wound coil has a great potential in nuclear magnetic resonance and magnetic resonance imaging owing to the better spatial homogeneity of the magnetic field. However, high-temperature superconducting (HTS) coil wound by no-insulation (NI) layer-wound technique has been verified with a long field delay time. A new method named the intra-layer no-insulation (LNI) winding technique has been proposed to reduce the charging delay time of the coil. This paper is mainly to study and compare the ramping loss and mechanical characteristics of the layer-wound coil and LNI coil. The results indicate that the total ramping loss can be significantly reduced by using the LNI winding method. The effects of the ramping rate of power supply current and the contact resistivity on the ramping loss are also discussed in the paper. Furthermore, the stress distributions in the layer-wound coil and LNI coil are compared, where the cooling process and Lorentz force are both considered. It can be found that the copper sheet of the LNI coil experiences relatively higher stress than its (RE)Ba 2 Cu 3 O x (REBCO) conductor layer. Meanwhile, the magnitude of stress generated in the REBCO conductor of the LNI coil is slightly different from that of the layer-wound coil.

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Section: Introductionmentioning

confidence: 99%

Ramping loss and mechanical response in a no-insulation high-temperature superconducting layer-wound coil and intra-layers no-insulation coil

Liu

Yong

2021

Sci. China Technol. Sci.

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“…Park et al constructed and tested a nested configuration of NI rare earth barium copper oxide (REBCO) for GHz class NMR [10]. 'Metal as insulation' variant of no-insulation winding, also known as 'stainless steel clad' magnets, have also been constructed and tested [11,12], reducing charging delay. Suetomi et al tested a no-insulation layer wound version of the winding method [13] which could prove promising in the future.…”

Section: Introductionmentioning

confidence: 99%

Understanding quench in no-insulation (NI) REBCO magnets through experiments and simulations

Bhattarai

Kim

Radcliff

et al. 2020

Supercond. Sci. Technol.

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Present research on no-insulation (NI) rare earth barium copper oxide (REBCO) magnets have demonstrated their ability to produce high fields due to their compact nature. NI magnets have often been demonstrated to be self-protecting. However, evidence of mechanical damage in recent high field magnets, suggests that there are some issues about quench that must be resolved for this otherwise promising technology. This article attempts to explain multi-physics phenomena occurring during the quench of an NI magnet that can be used to elucidate quench behavior through experiments and simulations. A lumped circuit model is used for the circuit analysis where each coil is modeled as a single inductor with variable quench resistance in series and characteristic contact resistance in parallel. Three case studies have been analyzed: (1) a 3 double pancake (DP) standalone magnet, (2) a 2 DP coil in 31 T background, and (3) a high temperature superconductor/low temperature superconductor (HTS/LTS) hybrid user magnet that consists of a 13 T HTS insert and a 6 T LTS background magnet. Lessons learned from these analyses include: (1) characteristic resistance of NI coil rises during quench with the temperature rise; (2) influence of Hall effect exists on the voltage rise during quench; (3) over-current during quench can over-stress the coil; and (4) quench propagation from one end of the magnet generates significant unbalanced forces. This approach is expected to be used in the preliminary design of an ultra high field (>40 T) user magnet currently under design at the National High Magnetic Field Laboratory.

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“…The no-insulation (NI) REBCO magnet has advantages of self-quench-protection and high engineering current density over its insulated counterpart [1][2][3][4]. But it also has a few significant drawbacks, such as long charging/discharging delays and high ramp losses, which limit its applications in user magnet systems where frequent field ramps are required.…”

Section: Introductionmentioning

confidence: 99%

“…Another method to control  c in a NI magnet is to control the surface oxides on co-wind tapes. Since high field REBCO magnets often require co-wind tapes for mechanical reinforcement [4,23], it is convenient to control the surface of co-wind tapes instead of that of the REBCO tapes. This way, the potential damage to the REBCO tapes during handling and the oxidation process is avoid.…”

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confidence: 99%

Contact resistivity due to oxide layers between two REBCO tapes

Lü

Xin

Lochner

et al. 2020

Supercond. Sci. Technol.

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In a no-insulation (NI) REBCO magnet, the turn-to-turn contact resistivity ( c ) determines its quench selfprotection capability, charging delay time and the energy loss during field ramps. Therefore it is critically important to be able to control a range of  c values suitable for various NI magnet coils. We used a commercial oxidizing agent Ebonol  C to treat the copper surface of REBCO tapes. The copper oxide layer was characterized by cross-sectional transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The oxide layer formed in Ebonol  C at 98 °C for 1 min is Cu 2 O of about 0.5 m. The  c between two oxidized REBCO is in the order of 35 m-cm 2 at 4.2 K which decreases slowly with contact pressure cycles. The  c increases but only slightly at 77 K. We also investigated the effect of oxidation of stainless steel co-wind tape on  c . The native oxides on 316 stainless steel tape as well as those heated in air at 200 -600 °C were examined by TEM and XPS. The native oxides layer is about 3 nm thick. After heating at 300 °C for 8 min and 600 °C for 1 min, its thickness increases to about 10 and 30 nm respectively.For the stainless steel tapes with about 10 nm surface oxides, pressure cycling for 30,000 cycles decreases  c by almost 4 orders of magnitude. Whereas at 77 K, it only changes slightly. For a surface with 30 nm oxide, the  c decreases moderately with load cycles. The results suggest that for an oxidized stainless steel to achieve stable  c over large number of load cycles a relatively thick oxide film is needed.

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Metal-as-insulation variant of no-insulation HTS winding technique: pancake tests under high background magnetic field and high current at 4.2 K

Cited by 60 publications

References 24 publications

Ramping loss and mechanical response in a no-insulation high-temperature superconducting layer-wound coil and intra-layers no-insulation coil

Ramping loss and mechanical response in a no-insulation high-temperature superconducting layer-wound coil and intra-layers no-insulation coil

Understanding quench in no-insulation (NI) REBCO magnets through experiments and simulations

Contact resistivity due to oxide layers between two REBCO tapes

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