Nitrogen Precooled Multi-Stage Pulse Tube Refrigerator Reaching 2.1 K

Abstract

The pulse tube refrigerator (PTR) offers the advantage of having no moving parts at low temperatures. This feature results in increased reliability and reduced vibrations of the cold head. Moreover, the extension to multi-stage PTR systems is mechanically quite simple. This chapter reports performance studies on a multi-stage pulse tube refrigerator (PTR) for operation at liquid 4He temperatures. In the current set-up the 1st stage consists of a liquid nitrogen bath with heat exchangers which serve to precool the oscillating 4He-gas flow passing two subsequent pulse tube stages. The two PTR stages are operated in orifice- and double-inlet mode with the phase-shifting components located at ambient temperature. Er3Ni shot is used for the regenerator matrix in the coldest stage. A minimum temperature of 2.13 K has been achieved.