This paper describes the manufacture and test of a thermally connected two-stage 4 K pulse tube refrigerator. The second stage of the refrigerator involved the use of either a “two middle-buffer with double inlet” type phase shifter or a “two middle-buffer with displacer.” The phase shifter of the first stage was a two middle-buffer type. The connecting tubes between the cold head and the pressure switching valves were 1.5 meter long in order to reduce the vibration and the electromagnetic noise near the cold head. The best cooling capacity, 0.58 W at 4.2 K, was achieved with 5.5 kW of input power and the two middle-buffer with double inlet type phase shifter.
KeywordsMass Flow Rate Needle Valve Pulse Tube Valve Timing Bypass Line
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