Thermal Conduction Characteristics of Bi- and Y-system Tape ConductorsAiming at Conduction-cooled Magnet

Abstract

This paper reports thermal diffusivities of Bi-system and Y-system tape conductors. First, we measure temperature traces of the bundled conductors for the heater disturbance at conduction cooling conditions. Obtained results are modeled and analyzed using one-dimensional as well as two-dimensional heat balance equations. We show that the analysis results can successfully reproduce the experimental results for a wide temperature range from 20 to 77 K. On the basis of such results, we also clarify that the thermal diffusivity, in the perpendicular direction to the tape surface, of the Y-system conductors are five orders of magnitude lower than that of the Bi-system ones. Our results indicate that the consideration of such low thermal diffusivity is important for the conduction-cooled magnet design.

Experimental and numerical investigation of screening currents induced in a Bi-2223/Ag double pancake coil for space applications

“…As a scaled-down model for space applications, a double pancake coil was fabricated with a Bi-2223/Ag tape of 200 m length and was set at the second coldstage in a conduction-cooled experimental system [10], as depicted in figure 1. The specifications of the coil are shown in table 1, and current, Iop, versus voltage, V, for the coil are shown in figure 2; we obtained these values in a previous study [10]. The minimum critical current, I cmin , of the coil at 50 K was about 200 A (maximum electric field, Emax, in the coil was 1 μV/cm at 200 A in self-field).…”

“…For HTS coils, great care is needed to avoid coil quench in space. To that end, we previously developed a thermoelectromagnetic field analysis method [10] that can evaluate the thermal stability of the HTS coil. The analysis is based on the so-called percolation depinning model [11], which can quantitatively express the current density versus electric field in HTS tapes as a function of temperature and magnetic field vector.…”

“…In this study, we investigated a Bi-2223/Ag coil, which is a candidate for magnetic sail spacecraft [10]. It has been reported that multi-filamentary Bi-2223/Ag tapes have superconducting connections (bridging) between neighbouring filaments [16][17][18][19][20][21].…”

Coupled-analysis of current transport performance and thermal behaviour of conduction-cooled Bi-2223/Ag double-pancake coil for magnetic sail spacecraft

“…11, the smaller electric field, coil voltage, and heat generation cause the coil to be quenched at the lower coil temperature. This result comes from the fact that, because the heat capacity of the Bi-2223/Ag tape decreases with the lower temperature [5], the temperature rises in the coil increases and the thermal stability of the coil decreases at the lower coil temperature. Note that, at less than 30 K, the electric fields which are more than one order of magnitude smaller than the common electric field criterion, 1.0 ×10 −4 Vm −1 , bring about the coil quenches.…”

“…Although YBCO coated conductors (CCs) possess high performance with respect to the critical current in high magnetic fields, Bi-2223/Ag tapes are adopted in this study. This is because the cooling characteristics of the YBCO CCs are inferior to those of the Bi-2223/Ag tapes [5] and, in addition, long length tapes with high homogeneity in the local critical currents along the length of the conductors are difficult to be available in the case of the YBCO CCs.…”