Systematic Studies of a Second Sound System for Quench Detection

Several tools for quench detection of supra conducting radio frequency (SRF) cavities are existing. One of these techniques uses the excitation of temperature waves in liquid Helium which are created by a quench on the cavity surface. Below the lambda point so called second sound waves occur. Special sensors, like Oscillating Superleak Transducers (OSTs) are able to detect the waves. With the help of the OSTs the transit times of the signals are determined. Using a set of algorithms one can postulate a most probable spot for the quench location. Two such methods are used at DESY: Multilateration and Raytracing. Their precision, their constraints and limits are compared, and the hardware systematics are studied. For this purpose a tool for calibration via simulation of a quench generated wave is developed. The simulation is done by injection of short heat pulses at exact known time and space coordinates. Measurements with the calibration tool and results of data analyses obtained with both algorithms will be presented.