Title :
AC loss and thermal runaway of 1 T cryocooler-cooled oxide superconducting pulsed coil
Author :
Miyazaki, H. ; Iwamoto, A. ; Iwakuma, M. ; Funaki, K. ; Hayashi, H. ; Tomioka, A.
Author_Institution :
Graduate Sch. of Inf. Sci. & Electr. Eng., Kyushu Univ., Fukuoka, Japan
fDate :
6/1/2004 12:00:00 AM
Abstract :
We fabricated a 1 T cryocooler-cooled oxide superconducting pulsed coil. It is a 16-layer solenoidal coil wound with an interlayer-transposed 4-strand parallel conductor composed of Bi-2223 multifilamentary flat wires. The insulated strands were transposed only between layers to make all strands inductively equivalent. To suppress the temperature rise due to the AC loss, the aluminum nitride (AlN) plates were arranged between layers as heat drains. The pulsed coil was cooled down to 30 K by a single stage cryocooler. It can be operated continuously at 40 K in the 1 T triangular wave operation at 1 Hz. First we studied the temperature dependence of thermal runaway current of the coil under the application of direct transport current. The runaway current was higher than the critical current, which was defined as the current where the electric field of 10minus;4 V/m was generated on average over the whole length of the conductor. Next we studied the temperature variation of the coil in a sinusoidal operation of 1 Hz. The temperature increment was much more gradual than that in the DC operation. In this paper, we discuss the thermal properties of the cryocooler-cooled oxide superconducting pulsed coil, taking into account the heat generation of AC loss and flux-flow loss and the cooling capacity of a cryocooler.
Keywords :
aluminium compounds; bismuth compounds; calcium compounds; cryogenics; electric fields; high-temperature superconductors; losses; multifilamentary superconductors; solenoids; strontium compounds; superconducting coils; thermal analysis; 1 Hz; 1 T; 16-layer solenoidal coil wound; 30 K; 40 K; AC loss; AlN; Bi-2223 multifilamentary flat wires; Bi2Sr2Ca2Cu3O; DC operation; HTS pulsed coil; cooling capacity; critical current; cryocooler-cooled oxide superconducting pulsed coil; direct transport current; electric field; flux-flow loss; heat generation; insulated strands; interlayer-transposed 4-strand parallel conductor; oxide-superconductor; single stage cryocooler; sinusoidal operation; temperature dependence; thermal runaway current; triangular wave operation; Aluminum nitride; Conductors; Critical current; Insulation; Multifilamentary superconductors; Superconducting coils; Superconducting epitaxial layers; Superconducting filaments and wires; Temperature dependence; Wounds; Ac loss; HTS pulsed coil; flux-flow loss; oxide-superconductor; thermal runaway;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2004.830106