Vacuum Insulation for a Cryostat.

In the structure of any cryogenic system, thermal isolation of the low temperature environment must be achieved effectively. Fundamental thermal insulation techniques and heat transfer mech anisms are shown in the framework of cryostat design described below. Heat leaks onto a low temperature environment through the thermal insulation of the cryostat can be devided into three different mechanisms. (1) Gas conduction in void spaces contained between the insulation mate rials. (2) Radiation across these void spaces and through the components of the insulation. (3) Solids conduction through the insulation materials and contact heat transfer between individual components of the insulation. The type of vacuum insulation, such as evacuated powder insula tion, plain vacuum insulation, and multilayer insulation (MLI), must be chosen suitably for a given cryogenic application. The selection must be aided by a study of the heat transfer in the particular vacuum insulation. 1.