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TUP040 |
Quench Dynamics in SRF Cavities | |
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Funding: The work herein has been performed at Fermilab, which is operated by Fermi Research Alliance, LLC under Contract with the United States Department of Energy. A quench in SRF cavities is a thermal runaway process that causes a rapid loss of the stored RF energy. A quench is one of the factors that limits performance of the cavity. We have developed a comprehensive model describing the thermal and electromagnetic dynamics in the quench zone of an SRF cavity. The model has already provided us with insights essential to improved performance of SRF cavities. The predicted size of the hot spot that emits 2nd-sound during the quench is important for the Oscillating Sound Transducer (OST) quench detection technique; the maximum size of the normal zone formed during the quench determines cavity quality degradation; anomalous RF decay time distinguishes a real quench from other mechanisms of sudden loss of RF power in the cavities. We describe the model, discuss the most important results and compare them to experimental data. |
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| TUP112 | Time-Resolved Measurements of High-Field Quench in SRF Cavities | 743 |
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| Fermilab’s temperature mapping system for SRF cavities has been improved to observe quench dynamics with 1ms time resolution. The increase in sampling rate was achieved by localizing the quench and then performing the measurements using a limited subset of thermometers. Implemented experimental procedure allowed to measure temperature distribution within quench spot, as well as the amount of stored energy, at the moment quench starts, during its growth, and decay. For three tested SRF cavities, quenching at fields 21.7 – 33 MeV/m, maximal radius of the normal zone was 40 – 65 mm; time to return to superconducting state: 90 – 250 ms. In the beginning of the process temperature increase rate in the center of the normal zone is as high as 2.5 K/ms, radius increase rate – 20 mm/ms. The described experimental procedure can be useful for investigating how different surface treatments affect the breakdown, understanding of the nature of high-field quench, improvement of quench detection techniques, and material science research for future SRF cavities. | ||