Ultrahigh cryovacuum systems cooled by solid nitrogen

Theoretical, computational, and experimental data are described which demonstrated that sorption pumps with smooth metal surfaces and classical adsorbents cooled by solid nitrogen to 63-35 K are more effective than pumps operating at 77.4 K. Several pump designs with liquid and solid N2 coolants are considered, and their characteristics and operating properties are discussed. Experimental and calculated isotherms are presented for adsorption of N2 and H2 by activated charcoal for T = 77.4-50 K.