Effect of low temperature baking in nitrogen on the performance of a niobium superconducting radio frequency cavity
Pashupati Dhakal, Santosh Chetri, Shreyas Balachandran, Peter J. Lee, Gianluigi Ciovati
DOI 10.1103/PhysRevAccelBeams.21.032001 · Physical Review Accelerators and Beams
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Abstract
We report the rf performance of a single cell superconducting radiofrequency cavity after low temperature baking in a nitrogen environment. A significant increase in quality factor has been observed when the cavity was heat treated in the temperature range of 120–160 °C with a nitrogen partial pressure of ∼25 m Torr. This increase in quality factor as well as the Q-rise phenomenon (anti-Q-slope) is similar to those previously obtained with high temperature nitrogen doping as well as titanium doping. In this study, a cavity N2-treated at 120 °C and at 140 °C showed no degradation in accelerating gradient, however the accelerating gradient was reduced by ∼25% with a 160 °C N2 treatment, compared to the baseline tests after electropolishing. Sample coupons treated in the same conditions as the cavity were analyzed by scanning electron microscope, x-ray photoelectron spectroscopy and secondary ion mass spectroscopy revealed a complex surface composition of Nb2O5, NbO and NbN(1−x)Ox within the rf penetration depth. Furthermore, magnetization measurements showed no significant change on bulk superconducting properties.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 9.2 | Pressure not reported | unknown |
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