The 'Q disease' in superconducting niobium RF cavities
Jul 10, 200318 pages
Part of Proceedings, 1st International Workshop on Hydrogen in Materials and Vacuum Systems : Newport News, Virginia, November 11-13, 2002, 133-150
Published in:
- AIP Conf.Proc. 671 (2003) 1, 133-150
Contribution to:
- Published: Jul 10, 2003
DOI:
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Abstract: (AIP)
Superconducting niobium cavities can achieve quality (Q 0) factors of 1010–1011, more than six orders of magnitude higher than conventional copper cavities. However, to maintain this performance at high accelerating gradient (20 MV/m) the radio‐frequency (rf) surface must be damage and dust free. Cavity preparation techniques therefore routinely include a chemical etch or electropolishing. Under certain conditions, these (and other) treatments can contaminate the niobium with hydrogen. Hydrides may then form when the cavity is cooled through 150 K, even if only a few atomic percent hydrogen are present. If hydrides are formed, the cavity quality can degrade substantially (Q disease). A rapid cooldown often inhibits the hydride formation. Other “cures” include degassing cavities at 900 °C to eliminate the hydrogen. A historical review of the Q disease is provided here, with the emphasis being placed on its discovery, symptoms, mechanism, and cures.- talk: Newport News 2002/11/11
- RF system: superconductivity
- niobium
- RF system: energy loss
- RF system: impedance
- RF system: surface
- damage: surface
- hydrogen
- history
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