We have studied the advantages to be gained by replacing the orifice of a pulse tube cooler with an inertance tube--a long thin tube that introduces the possibility for additional phase shift between pressure and mass flow in the pulse tube section. A case for using an inertance tube is made by employing an electrical analoygy, where the 'inductance' added by the inertance tube allows for an improved power transfer efficiency at the cold end of the pulse tube. Detailed computer modeling of pulse tube systems with inertance tubes confirms these advantages. Comparison between a laboratory cooler with an orifice and with two inertance tubes is presented; the inertance tubes yield dramatic improvements over the use of the orifice.
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