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Accepted · first revision · record

Title: Why low-temperature baking at about 120 C removes the Q-slope
Plain: Heating a niobium cavity at about 120 degrees Celsius for two days removes the high-field loss rise. What this mild bake changes in the metal is not fully known.
Precise: A 120 C bake of 24 to 48 h in vacuum eliminates the high-field Q-slope in electropolished Nb. Determine which change in the near-surface region (oxygen diffusion from the native oxide, suppression of hydride nucleation by vacancy-hydrogen complexes, or change in mean free path) is necessary and sufficient, and predict the required bake time and temperature.
Settled by: Depth-resolved composition and defect measurements on samples baked in parallel with cavities, reproducing the cure and its absence for varied bake parameters.
Kind: phenomenon
Answer type: mechanism
References: (empty)
Literature status: contested
Status note: (empty)
Posed since: (empty)