| 摘要 |
PURPOSE:To suppress the increase of a leakage magnetic field by a method wherein a current is quickly attenuated by forcibly generating transition of normal conductivity on all coils when transition of normal conductivity is generated on one of coils with which main and cancel coils are constituted. CONSTITUTION:When transition of normal conductivity is generated on a superconducting main coil 1aA, a current is allowed to flow quickly on a coil protective element 7aA and the main coil is protected, and at the same time, coils 1bA to 1eA and 2aA to 2eA are heated up, and transition of normal conductivity is forcibly caused. As protective elements 7bA to 7eA and 8aA to 8eA are parallel-connected to the coils 1bA to 1eA and 2aA to 2eA respectively, and also they are wound on all coils 1aA to 1eA and 2aA to 2eA, each coil is protected and a heating state is continued. Accordingly, the voltage on both ends of the coils, showing transition of normal conductivity, is boosted, the sensitivity of detection is improved, and the current decrease time constant is reduced. As the current flowing on all coils attenutes quickly, the leakage magnetic field, which is the difference of generated magnetic field of coil, is also attenuated quickly. |
