Field Emission and Thermal Breakdown in Superconducting Niobium Cavities for Accelerators
نویسنده
چکیده
Field emission and thermal breakdown are the main mechanisms limiting the accelerating gradient of niobium radio-frequency cavities. Diagnostic tools to study these mechanisms include quality measurements, thermometry, and microscopy. Results presented here demonstrate that micron-size, conducting particles are the source of field emission. Thermal breakdown is caused by a variety of defects such as inclusions, pits, and submillimeter-size particles. Techniques developed to minimize field emission and thermal breakdown include clean-room assembly, high-power processing (to avoid field emission) and the use of high-purity niobium (to avoid thermal breakdown). With these techniques, accelerating gradients of 20–30 MV/m can be achieved in
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