Adaptive vibration reduction on dual-opposed piston free displacer Stirling cooler

In a Stirling-type pulse-tube cooler with a dual-opposed piston compressor, the residual vibration exported by the cooler is primarily a result of residual imbalances between compressor motors. Using an electronic feedback loop [1] and driving compressor motors in a master-slave configuration, the exported force from the compressor can be regulated to negligible levels. This has been demonstrated in a multitude of commercial applications [2] as well as in space applications. In a novel application of the same electronic feedback technology, the residual exported forces resulting from the motion of the free moving displacer of a Stirling cold finger are compensated, by using the linear dual-opposed piston compressor as an active balancer. Theoretical analysis of this is provided, measurements are presented on different cooler types, and the effect of integration aspects - hard mount versus suspended - is discussed. The effect on exported vibration as well as power efficiency is discussed and compared between Stirling and pulse-tube type coolers. Currently available off-the-shelf hardware, the CDE7232, is presented and future developments are discussed.