Superconductors and microwaves

Superconductivity, along with other cryogenic electronic technologies, can provide microwave and millimeter-wave (mm-wave) components, both passive and active, with characteristics superior to what can be realized using conventional room-temperature technologies [1], [2]. Radio astronomers have been cooling their receiver front ends to temperatures of 10 K and below for more than 50 years whereas superconductor-insulator- superconductor (SIS) devices cooled to near 4 K have been used as the mixers and detectors of preference for radio telescopes operating in the mm-wave frequency range since the 1970s. Other cryogenic electronics that date back to the 1960s include infrared focal plane arrays that were operated at temperatures of 50-70 K whenever long wavelength operation and very low noise are required. Although superconducting devices (such as high Q-value cavities) have a long history in high-energy physics (HEP) particle accelerators, other applications have not found wide use. Several factors have contributed to this situation including the lack of maturity of some of these technologies, as well as the practical fact that the cryogenic burden has been perceived as too great compared to the performance advantage that could be realized.