Invited keynote possibilities for microwave/far infrared cavities and waveguides using high temperature superconductors

Possibilities for use of high temperature superconductors in microwave/far infrared resonators and waveguides are described. Relative to conventional superconductors, the use of high temperature superconductors could remove the constraint of relatively low energy gaps and provide larger thermal margins and more effective cooling. The higher critical magnetic fields may also be important for an increased range of operation. These features could be used to improve performance of present superconducting microwave cavities and to provide new applications at both microwave frequencies and at much higher frequencies. Constraints that may inhibit development include a need for superconducting properties over a high fraction of the surface, limits on critical RF fields and the effect of D.C. magnetic fields.