Quantitative analysis of the near-surface dislocation content performed using electron backscattered diffraction for samples cut from niobium cavities limited by the 'high field Q-slope' effect show a high dislocation content, as well as a pronounced change in the near-surface dislocation content caused by 100–120C annealing when such annealing has a healing effect on the high field Q-slope. A model was proposed for the sharp degradation of the cavity Q at high field for niobium cavities based upon dislocation-assisted magnetic flux entry at surface magnetic fields lower than those expected for ideal niobium. It was proposed that the elimination of the high field Q-slope by 100–120C annealing was caused by vacancy-assisted dislocation climb in the near-surface region.

The Role of Near-Surface Dislocations in the High Magnetic Field Performance of Superconducting Niobium Cavities. A.Romanenko, H.Padamsee: Superconductor Science and Technology, 2010, 23[4], 045008