Overcoming Q-drop is a crucial step toward reliable achievement of the 35 MV/m
gradient in the superconducting RF cavities for the ILC project. Although a cure for
Q-drop exists, consisting of a modest temperature heat treatment, the
understanding of its cause(s) is still lacking. Many experiments have been
conducted, providing us with a solid set of facts that need to be explained by one
model. Many explanations have been proposed but none was thoroughly proven.
The purpose of this review is to gather all the experimental evidence pertinent to the
Q-drop phenomenon in niobium cavities. We also attempt to discuss the available
models to explain it. This review is yet another step in the ongoing exploration of the
Q-drop problem, one of the “hot topics” in SRF technology today. |
