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TT: Fachverband Tiefe Temperaturen

TT 58: SC: Vortex Dynamics, Vortex Phases, Pinning

TT 58.1: Talk

Thursday, March 17, 2011, 17:30–17:45, HSZ 301

Study of the imperfect Meissner effect in niobium — •Sarah Aull, Oliver Kugeler, and Jens Knobloch — Helmholtz-Zentrum Berlin

When cooling niobium below the critical temperature T_c in the presence of a magnetic below H_c1, the magnetic field is expected to be expelled from the sample via the Meissner effect.

However, even below H_c1 one observes flux trapping - presumably at pinning centers such as impurities and lattice defects - leading to an incomplete Meissner effect or even suppression of the Meissner effect entirely.

We measured the level of flux trapping in niobium samples that have undergone several different treatments commonly employed for the production of superconducting RF cavities, such as chemical and heat treatment. The dependance on the material crystallinity and the influence of spatial and temperoral temperature gradients during cool-down were investigated as well.