PURPOSE: To lessen magnetic noises inside a shielding case by a method wherein the shielding case is formed of Ni of high magnetic permeability, the inner surface of the case is covered with an oxide superconductor, and the outer surface of the shielding case is covered with a laminated film composed of thin films of high conductivity.
CONSTITUTION: A shielding case 2 is formed of Mumetal of Ni alloy, a buffer layer 6 of Pt is formed 10μm thick on the inner surface of the case 2 through sputtering, and a Y superconductive thin film is successively formed 3μm in thickness as an oxide superconductor 1 thereon. At this point, the case 2 is made to rotate. Then, five insulating films 4 of SiO2 and five high conductive film 3 of Cu are alternately laminated to serve as an electric shielding layer. The case 2 is 1mm thick, and the films 3 and 4 are formed 30Onm in thickness. By this setup, when all this case is dipped into liquid nitrogen to put superconductor in a superconductive state, a magnetic field inside the shielding case can be reduced to almost zero in intensity.
TONO HIDETAKA
SETSUNE KENTARO
