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Pulse tube cooler has the advantages of higher reliability and longer MTTF compared with Stirling cooler due to the elimination of moving components at the cold end. Pulse tube cooler working in the liquid hydrogen temperature region has already become a strong candidate in the fields of space science and high-temperature superconductivity. However, the current efficiency of the pulse tube cooler at liquid hydrogen temperatures is still low. In this paper, a two-stage thermally-coupled Stirling-type pulse tube cooler working in the liquid hydrogen temperature region is simulated. The first and second stages use independent ambient displacers as phase shifters. The middle of the second stage regenerator and pulse tube will be pre-cooled by consuming part of the cooling capacity of the first stage through the intermediate heat exchangers. The simulation results show that the pulse tube cooler can reach a higher relative Carnot efficiency due to the improvement of the phase distribution of the whole system by using ambient displacers. Meanwhile, the influence of factors such as charge pressure, frequency, pre-cooling position and pre-cooling temperature on the system performance will also be discussed.
