Variable phase shift devices for pulse tube coolers

Various embodiments are directed to pulse tube coolers having flow resistance devices that are variable within the thermodynamic cycle of the pulse tube. An example pulse tube may comprise a compressor, a regenerator, a reservoir and a pulse tube. A working fluid may be positioned within the regenerator, pulse tube and reservoir. Further, a variable phase control device may be positioned in a fluid path between the pulse tube and the reservoir. The pulse tube cooler may also comprise a control circuit. The control circuit may be programmed to vary a characteristic of the variable phase control device based on the position of the pulse tube cooler in its thermodynamic cycle.