Advanced Cold Head Manufacturing Techniques

Cryocoolers are small-scale cryogenic refrigerators with refrigeration capacities ranging from a few milli-Watts to several tens of Watts. The two main classes of cryocoolers are regenerative and recuperative, with the distinction being made by the major heat exchanger type required. Within the regenerative cryocoolers, the two major types for aerospace use are Stirling and pulse tube. Both types are based on the same thermodynamic cycle and have many similarities in operation. The primary difference is the manner in which the phase is shifted between the pressure and mass flow to generate the cooling. In the Stirling, this is done with a moving displacer while a pulse tube uses a passive phase shifter, often an inertance tube. The cold head is a complex part to manufacture and we propose a new method to manufacture the cold head as one part using photo etching and diffusion bonding. This would allow simple manufacturing of the cold head and also provide more control over the geometry, particularly the regenerator, allowing a higher level of optimization improving system performance and reducing mass.