Precision Experiment on the Study of Helium Isotopes Cryosorption in Terrestrial Conditions and at Lower Gravity

Characteristic features of gaseous helium adsorption near the -point at low pressure were discussed at the international seminar on low temperature physics in microgravity CWS-97. It has been shown in that paper that at ⁴He cryosorption on the argon cryolayer near the ⁴He -point, a jump-like pressure change above the cryolayer took place. At ³He cryosorption on the argon layer formed in identical conditions an abrupt pressure change above the cryolayer in the ⁴He -point area has not been observed. The present study deals with the isothermal behavior of the cryopanel in terrestrial conditions. Experiments were conducted to study the character of the temperature change with respect to the column height of liquid helium inside the helium cryostat in the case of vapor pumping and in the case of warming up of liquid helium and cryopanel due to heat coming.Temperature stratification of liquid helium due to natural convection has been calculated. Calculation program for integral characteristics of the liquid heating and cooling process has been compiled accounting for the stratification effect. These characteristics include the cold nucleus volume, nucleus temperature, height of the stratification layer, temperature profile in this layer, time of these stages depending on the given rate of the pressure growth in the system.Problems of the precision experiment to study helium isotopes cryosorption (⁴He and ³He) in terrestrial conditions and at lower gravity have been discussed.