What sets the residual surface resistance floor of niobium cavities? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title · changed
Revision 1: What sets the residual surface resistance floor of niobium cavities
Revision 2: What sets the residual surface resistance floor of niobium cavities?
Plain
Even far below the superconducting transition, cavities keep a small leftover energy loss whose sources are only partly identified.
Precise · changed · core
Revision 1: At $T <\sim 1.5\,\mathrm{K}$, where the BCS surface resistance at 1.3 GHz is negligible, the quality factor of the best Nb cavities saturates at $Q_0$ of order 1e11 (residual resistance $\sim 1-3\,\mathrm{nOhm}$), set by a temperature-independent residual surface resistance. Determine the fractions contributed by trapped magnetic vortices, two-level systems in the surface Nb2O5 oxide, and subgap quasiparticle states, as functions of field, frequency and surface treatment.
Revision 2: At $T <\sim 1.5\,\mathrm{K}$, where the BCS surface resistance at 1.3 GHz is negligible, the quality factor of the best Nb cavities saturates at $Q_0$ of order $10^{11}$ (residual resistance $\sim 1-3\,\mathrm{nOhm}$), set by a temperature-independent residual surface resistance. Determine the fractions contributed by trapped magnetic vortices, two-level systems in the surface $\mathrm{Nb_2O_5}$ oxide, and subgap quasiparticle states, as functions of field, frequency and surface treatment.
Settled by
Measurements of residual resistance versus trapped flux, frequency and field, combined with oxide removal or regrowth, that separate the three contributions.
Kind
well-posed
Answer type
identification
References
(empty)
Literature status
open
Status note
(empty)
Posed since
(empty)

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