Water ice-cooled MgB₂ coil made by wind and react process

Abstract

The wind and react (W&R) coil of inner diameter 53 mm has been made of multi-core MgB2/Nb/CuNi wire manufactured by internal magnesium diffusion (IMD) process. W&R coil is wound of not insulated rectangular wire of 1 mm2with only 5 µm thick stainless steel foil used for interlayer insulation. Transport current performance of the coil and short wire samples were measured in liquid He bath at external magnetic fields 4.5-8.5 T and also in self-field conditions inside the sub-cooled water ice at temperatures between 33 K and 38 K. The presented MgB2 coil exhibits stable behavior at water ice cooling and its high space factor allows to reach high current density of winding in comparison to the data of already published MgB2 coils. Presented results demonstrate that MgB2 windings can be used safely at He-free conditions inside the sub cooled water ice, and this technique can be further optimised and used for future MgB2 coils.

Influence of filament number and size on the basic properties of in situ made MgB2 wires

“…Comparable winding current density was measured for coils made by Kim et al [20] and by Kopera et al [18]. The present uninsulated W&R coil made from 0.64 × 0.80 mm SD18 square wire shows the same winding current densities (J w > 10 4 A cm −2 for B < 5.63 T) as the coil made by IMD process [19], and is attractive for future applications.…”

E–I characteristics and critical currents of small Bi-2223/Ag coil thermally stabilized by solid and liquid nitrogen compared to water ice

“…There are many detailed studies investigating the thermal properties of SN 2 at cryogenic temperatures [8][9][10]. Recently, the basic behaviour of MgB 2 coils inside the sub-cooled water ice was studied and no dry-out effect was observed [11,12]. Cooling of water from room temperature down to 12 K consumes some energy, but due to its favourable thermal properties, such as high sublimation pressure (∼10 −7 Pa @40 K) [8,13], relatively high thermal conductivity and capacity (k = 15 W m −1 K −1 and c p = 351 J Kg −1 K −1 @40 K) [14,15], the water ice still seems to be an inexpensive and safe cooling medium for superconducting windings and future He-free systems.…”

Transport measurement of MgB2 wire under the sub-cooled water ice compared to other cooling conditions

“…The system was filled by ∼60 kg liquid nitrogen (LN 2 ) and subsequently cooled to operating temperature of range 10 K-13 K. High thermal capacity of solid mass and relatively large thermal conductivity secured good thermal stability and humongous temperature around the magnets. Another candidate of suitable solid coolant is solid water ice, which is quite perspective for cooling of superconducting coils and magnets [19,20]. It was proved in [21] that H 2 O ice offer the mechanical support to compensate the Lorentz force, which can be crucial for superconducting magnet operation with the current pulses.…”

“…It was proved in [21] that H 2 O ice offer the mechanical support to compensate the Lorentz force, which can be crucial for superconducting magnet operation with the current pulses. The operation of superconducting MgB 2 coil cooled and stabilized by water ice bellow 36 K has been presented recently [20]. Presented W&R coil with high current densities of winding can be interesting for future He-free applications of MgB 2 cooled and stabilized by water ice.…”