Dynamic characteristics of adsorbents for adsorption pumps of dilution refrigerators

The data have been obtained on absorption isotherms of 4He in synthetic adsorbents at temperature of 4.2 K in pressure range 1-10-2 torr. The dependencies of pressure on adsorbed gas amount are studied in adsorption pumps under conditions simulating the pump work in dilution refrigerators. It is found that, at a constant pumping rate in the range (10-6-10-4) mole/s, the pressure in the pumps is practically independent of absorbed helium amount, in a fairly wide pressure range. The characteristics obtained can be used to design and to develop pumps for dilution refrigerators