Investigations on a 3.3 K four-stage Stirling-type pulse tube cryocooler. Part B: Experimental verifications

•Experimental verifications on the four-stage SPTC in Part A are conducted.•A no-load temperature of 3.3 K is achieved with He-3 at lower stages.•Interactions among four stages are experimentally clarified.•Cooling performances with He-4 and He-3 are experimentally studied and compared.•Cooling capacities at four temperatures are simultaneously achieved. In this part, a four-stage Stirling-type pulse tube cryocooler (SPTC) is worked out to verify the theoretical analyses conducted in Part A. Experiments are carried out to investigate the interactions among the four stages. The operating frequency, charge pressure and input power of the last two stages are optimized with He-4 and He-3, respectively. The experimental results show that a no-load temperature of 4.2 K is reached with He-4 and it further decreases to 3.3 K with He-3. The ability to providing simultaneous cooling powers is also tested. With He-3, the cooling powers of 4.4 W at 70 K, 1.0 W at 40 K, 0.29 W at 15 K and 0.025 W at 5 K are simultaneously achieved by the four stages, respectively. Satisfactory agreements are observed between theoretical and experimental studies.