Abstract
Pure metals have extremely large thermal conductivity at cryogenic temperatures, and are therefore key materials for conduction cooling of cryogenic devices. Copper is a typical example of such as material (as is aluminum): it can be highly purified up to the seven-nine level (7N) and is commercially available owing to recent technical developments. In this paper, the heat conductivity of 7N pure copper wire is analogized using the Wiedemann-Franz law from the resistivity measurement at cryogenic temperature. The measured RRR of the 7N copper was high, and the same as that of high-purity aluminum. Accordingly, high-purity copper can be considered as a good heat-conducting material.
