MEASUREMENT OF THERMAL-CONDUCTIVITY OF ULTRAPURE COPPER AT LOW-TEMPERATURES

Ultrapure copper with purity of 99.99999% (7N) was prepared and its th ermal conductivity was measured by a steady-state method, from 4.2 K t o 90 K. The apparatus for ultrapure copper measurement is introduced a nd the measured data are presented in this paper. As a result, the pea k of thermal conductivity is measured to be 45200 W/m.K when the tempe rature is 6.51 K. The measured data are compared with data in literatu re and with the value calculated by theory.