One of the technical issues in the application of High Temperature Superconducting (HTS) tapes is the need to wind long tape sections with uniform electric properties along their length. In recent years, the No-Insulation (NI) winding technique for HTS coils is emerging as a valid alternative to conventional insulated coils, as it allows a more effective current redistribution from the most...
No-insulation (NI) technique has been proved to be an available approach for improving the thermal stability as well as the highest operating current of the high-temperature superconducting (HTS) coil. Nevertheless, the NI HTS coil suffers from a non-negligible charging delay inevitably. To address this issue, the parallel co-wound technique is a possible way. For investigating the performance...
The use of high temperature superconducting (HTS) materials is promising for both DC and AC power applications and for high field magnets. However, HTS coils must be carefully protected against quench, since the formation of hot spots can damage the materials even more severely than in the case of low temperature superconducting coils. A possible solution to this issue is offered by the use of...
High-temperature superconducting (HTS) magnets have been widely studied for practical applications of NMR, MRI, and medical accelerators. 2nd-generation HTS, REBCO (Rare-Earth Barium Copper Oxide), coated conductors (CC) have a high critical field and excellent electrical properties, compared to other superconducting conductors. REBCO pancake coils using the no-insulation winding technique can...
As the so-called no-insulation (NI) HTS winding technique or its variations have expanded their applications beyond laboratory magnets, technical concerns on lifecycle such as lifetime, fatigue, long-term performance variation have become an important and timely imperative issue for the actual application of an HTS magnet to real-world systems. This paper reports long-term time-varying...
We have been studying the No-insulation coil (NI coil) for applications to medical cyclotrons for cancer therapy and high-magnetic-field whole-body MRIs. Since the layers in NI coil winding are not electrically insulated from each other, the current can be bypassing the adjacent layers when a local defect or normal transition occurs in the coil. Therefore, NI coil is expected to realize both...
We are developing large diameter (m-class) no-insulation (NI) REBCO coil systems for applications such as cyclotrons for cancer treatment and high-magnetic-field whole-body MRI. NI coil technology is expected achieving both high thermal stability and high current density, which are essentially tradeoff relationships. Conventionally, superconducting coils have been required to quickly dissipate...
We have been developing the No-insulation (NI) REBCO coil for applications to medical cyclotrons for cancer therapy and high-magnetic-field whole-body MRIs. NI-REBCO pancake coil is expected that can realize both high current density and high thermal stability, which are essentially trade-off relationship. Since in an NI coil, electrical insulation is eliminated, the operating current can...
We fabricated a conduction-cooled 3 T REBCO MRI magnet equipped with electrically conductive epoxy resin. The magnet is composed of 100 single pancakes and the total inductance is 91 H. When the operating current is 145 A, the central magnetic field is 3 T and the stored energy is 1 MJ. A quench protection test was carried out by raising the coil temperature using the heater. After the coil...
The no-insulation HTS coils can be excited above their critical current without burning out. The saturation of the magnetic field can be observed in the overcurrent excitation test, however, as the power supply further increases, there is still a risk of burning out of the NI HTS coil. This report uses a distributed circuit model validated by overcurrent experiments to study the overcurrent...
Due to excellent thermal stability and high-power density in steady state, no-insulation (NI) winding technology is widely used in the application of superconducting magnets. However, current ripple and background magnetic field fluctuations caused by relative devices result repetitive turn-to-turn current of the NI interpolated coil, which will impose a great impact on the thermal stability...
