| 摘要 |
PURPOSE:To inhibit an eddy-current loss by a method wherein plates forming an inner vessel are distinguished into three layers of a low-emissivity layer, a low-electrical resistance layer and a high-electrical resistance layer from the side of the outer surface toward the inner side. CONSTITUTION:An inner vessel 14 has a high-electrical resistance layer 15, such as a stainless plate of a thickness having a sufficient strength to an electromagnetic force, which is generated when a superconducting coil 5 is excited. A low-electrical resistance layer 16, which consists of a niobium-titanium alloy, a niobium-tin alloy or the like and is reduced its electrical resistance to zero in the state of a low temperature, is formed outside of this high-electrical resistance layer 15. The thickness of the layer 16 is formed at a mean value of 100mum or thicker. Moreover, a low-emissivity layer 17, which consists of gold, silver, platinum or the like and has a metallic luster, is formed on the surface on the outside of the layer 16. The thickness of the layer 17 is formed at a mean value of 50mum or thinner. Thereby, an overcurrent loss is significantly reduced to prevent an increase in the amount of evaporation of a liquid helium refrigerant due to an increase in the heat load of the inner vessel and a stable superconducting magnet can be obtained. |
