DEFECT LOCATION IN SUPERCONDUCTING CAVITIES COOLED WITH HE-II USING OSCILLATING SUPERLEAK TRANSDUCERS*

Superconducting RF cavity quench location is presently a cumbersome procedure requiring two or more expensive cold tests with large arrays of thermometers. One cold test identifies the cell-pair involved via quench field measurements. A second test follows with numerous fixed thermometers attached to the culprit cell-pair to identify the particular cell. A third measurement with many localized thermometers is necessary to zoom in on the quench spot. By operating superconducting RF cavities at temperatures below the lambda point the second sound wave emanating from the location where quench occurred can be utilized to triangulate on the quench-spot. Here a method which utilizes a few (e.g. 8) oscillating superleak transducers (OST) to detect the He-II second sound wave driven by the defect induced quench is discussed. Results characterizing defect location with He-II second sound wave OST detection, corroborating measurements with carbon thermometers, and second sound aided cavity repairs will be presented