Improved Methods of Testing Cryogenic Insulation Materials

Two improved methods have been developed for testing continuously rolled blankets and blanketlike thermal-insulation materials typically used in cryogenic vacuum systems. Both methods, and their corresponding apparatuses, are based on the cryogen boiloff calorimeter method according to which the amount of heat that passes through an insulation specimen to a cryogenic fluid in a vessel is proportional to the rate of boiloff from that vessel. The boiloff rate is then directly related to the insulating performance of the specimen. The main challenges in the execution of this technique are to (1) eliminate (or minimize) heat leak from the ends by use of thermal guards and (2) obtain stability of the cryogen inside the measurement vessel coincident with stability of the boundary conditions in the vacuum space.