A two-stage pulse tube cooler operating below 4 K

Abstract

A two-stage double-inlet pulse tube cooler for cooling below 4 K is designed and constructed by the aid of numerical analysis. The hot end of the 2nd stage pulse tube is connected to the phase shifting assembly at room temperature without the use of a regenerative tube. A commercial helium compressor with input power of 6 kW and a redesigned commercial rotary valve serve to generate the pressure oscillation. Using a three-layer 2nd stage regenerator filled with ErNi 0.9Co 0.1, ErNi and lead spheres, a lowest temperature of 2.23 K and cooling powers of 370 mW at 4.2 K and 700 mW at 5 K are obtained. The operating frequency is 1.0 Hz, the average helium pressure is 1.55 MPa, and the pressure ratio at the main inlet is 2.0. The cold head of the 2nd stage reaches 4.2 K after 100 min and 2.23 K after 270 min.