Cryogenic Thermal Management Advances during the CRYOTOOL Program

This paper describes the cryogenic thermal management advances made during the AFRL‐sponsored CRYOTOOL program. Advances occurred as a result of conducting four technology development tasks: (1) development of a differential thermal expansion cryogenic thermal switch (DTE‐CTSW) made with high purity Al end‐pieces and an Ultem support rod; (2) carrying out of a dual DTE‐CTSW/dual cryocooler performance test to quantify CTSW benefits in a redundant cryocooler system; (3) development of a miniaturized cryogenic loop heat pipe (mini‐CLHP) that combines flex link, conduction bar, and CTSW functionalities; and (4) development of an across‐gimbal cryogenic thermal transport system (GCTTS) with large diameter transport line coils for optics cooling. The results are as follows. The DTE‐CTSW achieved an ON conductance of 2–3.6 W/K (from 35–90 K) and an OFF resistance of 1100–2300 K/W (300–230 K warm end). The redundant cryocooler test showed modest parasitic heat leak savings when dual DTE‐CTSWs were used versus when they were not used. The mini‐CLHP, using neon as the working fluid, transported 2.5 W at 35 K, achieved an OFF resistance of 1555 K/W, and had cross/axial flexibilities of 100–450 N/m. Lastly, GCTTS, using nitrogen as the working fluid, transported 20 W at 100 K in a flat configuration. Additional work is needed to verify GCTTS operation in an elevated orientation.