Heat cutoff signal transmission unit and superconducting signal transmission apparatus

A superconducting signal transmission apparatus characterized by being provided with

• a vacuum container;
• a superconducting electronic device provided in the vacuum container;
• an input side transmission line and an output side transmission line, both comprising coaxial cables passing through the vacuum container and further being connected, respectively, to a signal input end and signal output end of the superconducting electronic device;
• and
• a cooling mechanism for cooling the superconducting electronic device;
• wherein a respective heat cutoff signal transmission unit is inserted into each of the input side transmission line and output side transmission line, wherein each said heat cutoff signal transmission unit comprises a flat circuit body provided with a substrate and with a signal transmission line and a ground layer both disposed on the substrate, where the substrate comprises a dielectric material having a low heat conductivity and where conductor portions providing the signal transmission line and ground layer have a thin thickness enabling suppression of the flow of external heat and the ground layer having slits for substantially reducing a sectional area of said ground layer to increase a thermal resistance through said sectional area, and wherein said coaxial cables are coaxial cables each having a heat cutoff structure at an outer conductor thereof.