haracterization of new Transition Edge Sensors for quench detection of Superconducting RF cavities via Second Sound and Thermal Mapping

One of the limitations in the operation of a Superconducting Radio Frequency cavities, utilized to improve the luminosity of future particle accelerators, is the quench (sudden loss of its superconducting state due to overheating). Localisation of quench initiating defects on the cavities is crucial in order to understand it and correct it. One of the methods used for the quench detection is called Transition Edge Sensors (TES), thermometers made of a superconducting narrow Au-Sn thin film that are currently being developed at CERN. This non-contact thermometry technique is based on the detection of a second sound wave, originated by the quench, in superfluid helium. Within the transition temperature range, a very large resistance change occurs from zero to the normal value, which makes the TES very sensitive. More details about TES’s operation, relevant concepts and scientific background can be found in Section 1. A large number of measurments was done in order to get TES's characteristics and assess the second sound capabilities of the TES. My work, described in Section 2, mainly relied on analysing data from these measurements and improving pulse analysis. Results showed a crucial role of composition, microstrucutre, thermal history, fabrication method and position on the wafer on sensor performance. After second sound detection test, pulse and peak analysis were done in order to validate TES as quench detectors. Section 3. consists of project conclusions and upcoming work. Literature used while writing this the report is presented in Section 4.