Potential conductors for a dc superconducting power transmission line in a 20-meter test bed

The cryogenic and electrical aspects of a program to evaluate superconductors for a d.c. superconducting power transmission line are presented. Results for 20-m long conductors operated at less than or equal to 10 kA are described. A battery driven power supply which is capable of delivering and controlling these currents is discussed. Specific experiments are discussed which were designed to probe the response of the conductors to a variety of thermal and electrical conditions, such as: thermal gradients over the length of the conductor, single and 2-phase flow of cryogen, loss of coolant flow, operation around critical temperature, a.c. ripple current, and high current ramping rates. (auth)