Heat Transfer between Fine Copper Powders and Dilute 3He in Superfluid 4He
The use of high-surface-area materials in dilution refrigerators has prompted several studies of the thermal resistance between such materials and dilute or concentrated 3He in 4He. Roubeau et al. t first reported anomalously high values for the Kapitza resistance of 20-μm-thick copper foil as compared with the Kapitza resistance of bulk copper. They proposed that this was a result of a thermal resistance between phonons and electrons. Wheatley et al.2 also saw this higher resistance when using 32-μm copper foil. We looked for this effect in sintered copper powders of 27, 20, and 2 μm diameter and also found high resistances.3 Our results were in semiquantitative agreement with Seiden’s calculations’ on the phonon-electron resistance.
KeywordsThermal Resistance Copper Foil Copper Powder Bulk Copper Thermal Boundary Resistance
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