| Presented as an invited talk at the 1998 Applied Superconductivity Conference and submitted for publication in IEEE Transactions on Applied Superconductivity. c○1999 IEEE. SRF 981009-07 Field Emission and Thermal Breakdown in Superconducting Niobium Cavit (2008) | |||||||||||||
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| Abstract—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 niobium cavities. I. | |||||||||||||
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