BEAMS
In the literature: open
Origin of the field-dependent losses in Nb3Sn cavities
In plain words
Even before stopping, Nb3Sn cavities lose more energy as the field grows. The source of this extra loss is unclear.
Precise statement
Nb3Sn cavities at 4.2 K and 1.3 GHz show $Q_{0}$ decreasing with $B_{\mathrm{pk}}$ above $\sim 300\ \text{to}\ 500\,\mathrm{G}$. Determine whether this arises from grain-boundary Josephson weak links, vortex penetration at local defects, tin-poor phases, or nonlinear BCS response, with a model predicting $Q_{0}(B_{\mathrm{pk}}, T)$.
What would settle it
Measured $Q_{0}(B_{\mathrm{pk}})$ for cavities with controlled grain size and stoichiometry matched by a predictive model.