High field Q slope and the effect of low-temperature baking at 3 GHz

• Published in: Physical review. Accelerators and beams Vol. 21; no. 1; p. 012002
• Main Authors: Ciovati, G., Eremeev, G., Hannon, F.
• Format: Journal Article
• Language: English
• Published: College Park American Physical Society 29.01.2018
• Subjects: Baking; Heating; Low temperature; Niobium; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Q factors
• ISSN: 2469-9888; 2469-9888
• DOI: 10.1103/PhysRevAccelBeams.21.012002

A strong degradation of the unloaded quality factor with field, called high fieldQslope, is commonly observed aboveBp≅100mTin elliptical superconducting niobium cavities at 1.3 and 1.5 GHz. In the present experiments several 3 GHz niobium cavities were measured up to and aboveBp≅100mT. The measurements show that a high fieldQslope phenomenon limits the field reach at this frequency, that the high fieldQslope onset field depends weakly on the frequency, and that the high fieldQslope can be removed by the typical empirical solution of electropolishing followed by heating to 120°C for 48 hrs. In addition, one of the cavities reached a quench field of 174 mT and its field dependence of the quality factor was compared against global heating predicted by a thermal feedback model.