Time Average Thermal Properties of a Computer Utilizing Thin-Film Superconducting Elements

It is necessary to understand the static thermal properties of cryotron gates before one can predict the limitations associated with dissipative heating of a complex cryotronic computer. An experimental program has been conducted to determine the thermal properties of isolated and of thermally coupled gates. All experiments reported in this paper were performed on tin gates evaporated onto glass substrates. The total thermal conductance K of a gate is defined, and experimental values of K are presented as a function of power and gate geometry. An analysis of the heat flow is given, based on a temperature-dependent coefficient of heat transfer. Theoretical values of K and temperature distribution are derived. The theory qualitatively predicts the temperature variation. Finally, the results are extrapolated to estimate the number of cryotrons that can be used safely in a thermally coupled system.