Abstract
The plastic dewar is suited to the use of the large pulse magaet and SQUID by means of its properties as the electrical insulator and non-magbetism. These are three problems which should be solved, i.e. 1) permeability of helium gas through the plastic wall, 2) cracking by means of thermal stress between room and liquid helium temperature, and 3) mechanical properties of gluing at liquid helium temperature.
These problems are discussed in this paper. Consequently, it is found that the plastic materials made by the methods of “filament winding” or “vacuum injection” for the liquid helium dewar are effective. The toughness of gluing part is sufficient at cryogenic temperature. The evaporation rate of liquid helium in the plastic dewar made on an experimental basis is measured, and it is found that its evaporation rate is equivalent to that of the metal dewar.
