Systematic studies of a cavity quench localization system [book]

Bosse Kolja Bein, Bosse Kolja Bein, Wolfgang Hillert, Lea Steder
Several tools for quench localization at Superconducting Radio Frequency cavities exist. One of these techniques uses the excitation of temperature waves in liquid Helium below the lambda point. These waves are created by a quench of the cavity surface and are called second sound waves. Special sensors, such as Oscillating Superleak Transducers (OST), are able to detect these waves. With the help of the OSTs the propagation times of the signals are determined. This method allows a parallel
more » ... rement of the quench-spot during a standard cavity performance test, whereas other methods require their own dedicated cold test or bear the risk of a contamination of the cavity surface, which requires a re-treatment of the cavity surface afterwards.Using a set of algorithms a most probable spot for the quench location can be calculated via the reconstruction of the second sound wave propagation path. Two such methods are used at DESY: Multilateration and Raytracing. New algorithms are implemented for these two basic methods in the scope of this thesis. They are including a method to introduce a propagation time offset and a second sound velocity dependent reconstruction. The precision, constraints and limits of these algorithms are studied in this thesis. A data set of nearly 200 quench events measured at 18 different tested single-cell cavities is used for a stochastic evaluation. To analyze the large number of events two automation processes are introduced.In the data set an angular and height dependency of the reconstructed quench-spot is observed and attributed to specific properties of the experimental setup. A common anomaly that the reconstructed quench-spot appears several millimeters above the cavity surface could be observed with all used algorithms in different manifestations. For the generation of an uncertainty propagation a Monte Carlo simulation is written. Using the improved algorithms developed in the scope of the thesis a spatial resolution of $6$ and $8$\,mm respectively can be achieved with the two be [...]
doi:10.3204/pubdb-2019-02359 fatcat:4cq6sukpd5dnze5mmvj3vjwe6a