Progress in the Development and Performance of a High Frequency 4 K Stirling-Type Pulse Tube Cryocooler
Bradley, P. E.
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Presently we are in the development process for a 4 K Stirling-type pulse tube cryocooler to support cooling requirements for a mobile THz detector system. In this paper we discuss the status of this development and the optimization methods for achieving 4 K with a three-stage hybrid design employing separate He-4 first and second stages that precool a He-3 third-stage. Acoustic power is provided by a linear compressor operating at 60 Hz and 2.5 MPa for the He-4 cryocoolers, whereas, a separate linear compressor operating at 30 Hz and 1.0 MPa provides acoustic power for the He-3 cryocooler. The first stage regenerator employs stainless steel mesh while the second stage regenerator employs erbium-praseodymium (ErPr). The third stage regenerator is layered with gadolinium oxysulphate (GOS) spheres at the cold end and erbium-praseodymium (ErPr) spheres at the warm end. This hybrid modular cryocooler design allows for a modular optimization approach for each cryocooler that mitigates time consuming redesign and fabrication of unaffected stages during the cryocooler development. Progress for each stage development and performance (goals and measured) optimization are presented.