Advanced study of the thermoelectrically generated magnetic field in a nine-cell cavity during the superconducting phase transition
J.-M. Köszegi, J. Knobloch
DOI 10.1103/PhysRevAccelBeams.22.052001 · Physical Review Accelerators and Beams
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Abstract
Today’s superconducting radio-frequency (srf) cavities approach quality factors up to 1011. With the decrease in overall dissipation the loss contributions previously considered minor gain in importance. One contribution is trapped magnetic flux. Superconducting rf cavities have to be cooled down to their cryogenic operating temperature. During the process, high temperature differences can occur in the system driving thermoelectric currents in the cavity wall and the surrounding liquid helium tank. The associated magnetic field can get trapped in the superconductor during its phase transition from the normal conducting into the superconducting (sc) state and significantly increase dissipation during later operation. The existence of this effect has been proven in general. The study presented here now adds experimental data and simulations on the amplitude and distribution of the trapped magnetic flux after the sc phase transition in the complete nine-cell cavity geometry. Furthermore, the dynamic behavior in the thermoelectrically generated magnetic field during the phase transition is evaluated.
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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