Patent ID: 7764153

Claim:
A magnetic field generator comprising: a high-temperature superconductor, which generates a superconducting magnetic field; a refrigerant vessel for storing a solid nitrogen; a vacuum container, which accommodates therein the high-temperature superconductor and the refrigerant vessel; and a refrigerator having a cooling head for cooling the refrigerant vessel, wherein the superconductor is arranged along a wall of the vacuum container, the cooling head of the refrigerator and the refrigerant vessel are in thermal contact with each other, and the refrigerant vessel and the superconductor are in thermal contact with each other, and wherein the vacuum container is provided with position regulation means comprising a bellows provided between upper and lower portions of the vacuum container and a position regulation device, so that a distance between an upper surface and a bottom surface of the vacuum container is varied by expanding/contracting the bellows by means of the position regulation device, whereby a clearance between a bottom surface of the superconductor and the bottom surface of the vacuum container is varied.