Performance tests of Bi-2212 pancake coils fabricated by a lamination method
✍ Scribed by H Kumakura; H Kitaguchi; K Togano; T Hasegawa; Y Hikichi
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 172 KB
- Volume
- 38
- Category
- Article
- ISSN
- 0011-2275
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✦ Synopsis
Bi-2212 pancake coils made by a lamination method were tested at various temperatures and magnetic fields. A small coil with 45 mm diameter was set at the center of a superconducting magnet system and tested at 4.2 K in various magnetic fields. E-J curves of the coils were well fitted with E = kJ n at all magnetic fields. n value of the E-J curve decreased with magnetic field, but was almost constant in fields above 10 T. Typical n-values were 17 at 0 T and 11 at 18 T. Estimation from the n-values indicates that a persistent current mode operation required for a NMR magnet is possible at high fields if the operating current density is kept less than about 30% of the critical current density J c . A coil with 128 mm diameter was tested at temperatures up to 70 K with GM cryocooler. In order to investigate the stability of the coil, voltage of the coil was measured as a function of time at a fixed operating current. Below ෂ30 K, a maximum operating current density for which the coil was stably operated was almost equal to J c defined with 10 -13 ⍀m. At 20 K J c was 4.6 × 10 4 A/cm 2 which was about 70% of that at 4.2 K, suggesting that the Bi-2212/Ag tape was promising as a conductor of cryogen free magnet.