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Title Effect of low temperature baking on niobium cavities
Type Talk  
Abstract A low temperature (100C 150C) in situ baking under ultra high vacuum has been successfully applied as final preparation of niobium RF cavities by several laboratories over the last few years. The benefits reported consist mainly of an improvement of the cavity quality factor and a recovery from the so-called Q drop without field emission at high field. A series of experiments with a CEBAF single cell cavity have been carried out at Jefferson Lab to carefully investigate the effect of baking at progressively higher temperatures for a fixed time on all the relevant material parameters. Measurements of the cavity quality factor in the temperature range 1.37K 300K and resonant frequency shift between 7K and 9.3K provide information about surface resistance, energy gap, penetration depth and mean free path. The experimental data have been analyzed with the complete BCS theory of superconductivity using a modified version of the computer code originally written by J. Halbritter. Small niobium samples inserted in the cavity during its surface preparation were analyzed with respect to their hydrogen content with a nuclear reaction analysis (NRA). The single cell cavity have been tested at three different temperatures befor and after baking to gain some insight on thermal conductivity and Kapitza resistance and the data are compared with different models. This paper will describe the results from these experiments and will comment on the existing models to explain the effect of baking on the performance of niobium RF cavities. Future work will include measurements on single cell cavities prepared with electropolishing. Work supported by the U.S. Department of Energy, contract DE-AC05-84ER40150

List of authors...

Principle author first.

Last (Family) Name First Name (Initials only) Affiliation or Organization (abbreviations if possible)
Ciovati G TJNAF
Kneisel P TJNAF
Myneni G. R. TJNAF

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