A miniature mixed gas refrigeration system and method is disclosed. A selected gas mixture is compressed to less than 420 psia for safety reasons. The compressed gas mixture is passed through a primary heat exchanger (140) and a primary/secondary heat exchanger (240) to precool the gas mixture. The secondary side of the primary/secondary heat exchanger is cooled by a secondary Joule-Thomson refrigeration system (200). Flow restrictions in the primary side of the primary/secondary heat exchanger (240) can solidify and trap liquid contaminants. The gas mixture exiting the primary outlet of the primary/secondary heat exchanger (240) passes to a primary expansion element (150) to expand isenthalpically to a to 183K or below to cool a heat transfer element. Return gas through the primary heat exchanger (140) precools the incoming high pressure gas mixture. A distal primary heat exchanger (160) can be added between the primary/secondary heat exchanger (240) and the primary expansion element (150).