US 12631389 B2 / May 19, 2026

High efficiency cold finger

Thermal energy transmission from a cryocooler cold finger is enhanced by means of a high thermal conductivity material used for or placed adjacent the cold finger end cap. In addition, the actual or effective surface area contacted by the working gas proximate the endcap is increased, thereby increasing the convective heat transfer coefficient. These features permit the coolest gas expansion space in the cold finger to be provided within the highly thermally conductive end cap, unlike many conventional designs in which the cold finger of low thermally conductive metal forms the expansion space side walls and the endcap forms only the axially facing outer surface in contact with the cooled equipment. Having the expansion space built into the high thermally conductive end cap reduces the temperature drop between the load to be cooled and the gas (e.g., helium), thus increasing the thermodynamic cycle efficiency.