To improve the degree of vacuum between layers simply, and sharply reduce invading heat flux by arranging a sheet material having multiple clearance whose hole diameter is a specified value and less, between at least layers of a multiple layer adiabatic material enclosed a low temperature machinery.

A radiation sealed for a low temperature machinery arranged inside a casing improved the vacuum degree of an inside, is arranged on an outer periphery of a cylindrical body 1 enclosed a low temperature machinery, and is constituted by a multiple layer adiabatic material 2 which consists of a thin plate material formed by coating aluminum with polyester film, aluminum foil, and the like, and a sheet material 3 having multiple clearance whose diameter of hole arranged at least between layers of the multiple layer adiabatic material 2 is several μm and less, more preferably, 4 to 7μm. As a sheet material 3, a material is employed, which is formed by weaving a fiber shaped raw material which consists of, for example, copper, nickel, and the like, and which is formed by coating aluminum with a surface so as to constitute a mesh structure whose one side of a frame is several μm and less, more preferably, 3 to 5μm.