ABSTRACT
Many systems, with increased complexity and better performances, were built and used in many astrophysical experiments. This chapter describes some of the most used systems, from single-stage to triple-stage sorption refrigerators. It describes in detail how to properly design a single-stage and a double-stage sorption cooler. The chapter discusses possible ways to achieve continuous operations with sorption coolers with completely sealed closed-cycle systems. The helium pot is the chamber where the liquid helium is collected, usually by the action of gravity. Pumping tubes normally connect stages at different temperatures. The main requirements therefore are maximum strength and minimal thermal conductivity. The condenser is the place where the helium gas is subject to condensation and, once it becomes liquid, it is pulled down by gravity into the helium pot. Heat switches are used for two reasons: pre-cooling of the cold stage and connection of charcoal pumps to the main reservoir.
