The 4K Tactical Cryocooler (4KTC) Concept Demonstration Program, a Phase II STTR, was awarded to Iris Technology Corporation by the Office of Naval Research (ONR) in September 2011. The primary objective of the program is to demonstrate a 3-stage hybrid Stirling/pulse tube/pulse tube “Demonstration Cryocooler” that is a pathfinder for a future productized 4KTC intended for use in low temperature superconducting electronics applications.
The objective operating point for the productized 4KTC is 200 mW of cooling at 4K. The cooler will additionally provide nominal capacity at the two higher temperature stages to intercept heat load and possibly cool intermediate electronics, such as low noise amplifiers. The objective cryocooler will be compact, lightweight, and affordable, with a price point substantially closer to that of a present day tactical cryocooler ($5000-$15,000) than a space cryocooler (>$2M). In short, ONR sought a solution that is substantially more compact, efficient and reliable than traditional commercial Gifford-McMahon type cryocoolers, which are the present standard for closed-loop 4K cryogenic refrigerators.
At the core of the effort is the development of a numerical model premised upon using three proven cryocooler software modeling tools. Each tool is used for the aspect of the modeling for which it is particularly well suited. Computational domains are deliberately overlapped so that in key areas (like the 3rd stage regenerator) the results from different software tools can be compared to enhance modeling confidence.
The primary objective of Phase II is to obtain experimental test data to substantiate the analytic predictions. In a cost savings move, this is to be accomplished by leveraging a new purpose-built pulse tube cold head (i.e., the 2nd and 3rd stages) with existing cryocooler assets, namely a compressor and Stirling expander 1st stage and warm end. Successful build and test of this cryocooler will represent the first build of this type of three-stage cryocooler, thus establishing the viability of the concept. Furthermore, it will provide an invaluable tool for the model correlation to inform the productized versions to follow.
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