Possible sources of residual power loss in R.F. superconducting cavities

The residual power loss in rf superconducting cavities has not been well understood. Various power loss sources are considered and their dependence on frequency and temperature are compared with experimental results D One power loss mechanism stands out as the most likely source of the residual power loss, It has been observed that a residual power loss exists in rf superconducting resonant cavities at very low temperatures, contrary to theoretical expectations 192 which predict that for angular frequencies, w, below the quantum region, the power loss should vanish as the temperature, T , approaches 0 K. The good agreement between these theories and experiment at higher reduced temperatures suggests that they are valid, and that the discrepancy lies in the presence of a very low, non-superconducting power loss mechanism. The nature of this loss has not been well understood. This is due in part in the past to a lack of agreement between results reported by various investigators on nominally equivalent samples. However, the more recent experimental data in which the residual power loss has been further reduced tend to be more consistent. These results indicate that for very