Characteristics of an activated carbon monolith for a helium adsorption compressor

An activated carbon monolith (ACM) with a high helium adsorption/desorption capacity, high density, low pressure drop, low thermal expansion and good mechanical properties was prepared and applied successfully in a helium adsorption compressor as a part of a 4.5 K sorption cooler. The activated carbon (AC) used in the monolith preparation was selected from a series of ACs prepared from an anthracite and bituminous coals activated using KOH, NaOH and CO2, and having a variety of surface areas, micropore size distributions and packing densities. The selected AC was combined with a binder to prepare an ACM with suitable mechanical properties for machining. The results of this study, related to an helium sorption compressor includes: packing density, mechanical properties (compression strength, vibration tests), thermal expansion, pressure-drop measurements and also helium adsorption isotherms measured at high pressure (up to 35 bar) and low temperatures (from 20 K up to 150 K).