We discuss and propose a complete data treatment, in close contact to typical microwave experimental data, in order to derive vortex parameters, such as pinning constant and viscous drag coefficient (also referred to as "vortex viscosity"), in a way as model independent as possible. We show that many of the accepted models for the complex resistivity can be described by a single, very general analytical expression. Using typical measurements of real and imaginary resistivity as a function of the applied field, we show that, even for single-frequency measurements, it is always possible to obtain (a) estimates of viscous drag coefficient and pinning constant with well-defined upper and lower bounds and (b) quantitative information about thermal creep. It turns out that neglecting thermal creep, in particular and counterintuitively at low temperatures, might result in a severe overestimation of the viscous drag coefficient. We also discuss the impact of thermal creep on the determination of the pinning constant. The present results might lead to a reconsideration of several estimates of the vortex parameters

To account for the dark matter content in our Universe, post-inflationary scenarios predict for the QCD axion a mass in the range (10 − 10 3 ) µeV. Searches with haloscope experiments in this mass range require the monitoring of resonant cavity modes with frequency above 5 GHz, where several experimental limitations occur due to linear amplifiers, small volumes, and low quality factors of Cu resonant cavities. In this paper we deal with the last issue, presenting the result of a search for galactic axions using a haloscope based on a 36 cm 3 NbTi superconducting cavity. The cavity worked at T = 4 K in a 2 T magnetic field and exhibited a quality factor Q0 = 4.5 × 10 5 for the TM010 mode at 9 GHz. With such values of Q the axion signal is significantly increased with respect to copper cavity haloscopes. Operating this setup we set the limit gaγγ < 1.03 × 10 −12 GeV −1 on the axion photon coupling for a mass of about 37 µeV. A comprehensive study of the NbTi cavity at different magnetic fields, temperatures, and frequencies is also presented.

The introduction of artificial pinning sites in YBa2 Cu3O7−d (YBCO) epitaxial thin films has been\ud obtained by pulsed laser deposition ͑PLD͒ technique from YBCO-BaZrO3 ͑BZO͒ composite targets\ud with BZO concentration ranging from 2.5 to 7 mol %. The typical critical temperature, Tc , drop\ud observed in YBCO-secondary phase films grown by PLD has been successfully recovered by\ud increasing the deposition temperature. Transport properties analyses revealed improved pinning\ud force values for YBCO-BZO films for BZO concentration above 5 mol %. These films exhibited an\ud anomalous dual peak structure which has been ascribed to the presence of two pinning\ud contributions. The crossover field, Bm , separating these two pinning regimes has been observed to\ud be temperature independent suggesting the occurrence of the matching field effect. The measured\ud value of Bm agreed with the matching field value, B⌽ = Knd⌽0 , as evaluated from transmission\ud electron microscopy investigations. The mark of this phenomenon is retained down to 10 K, making\ud YBCO-BZO more performing than pristine YBCO films at applied magnetic fields below Bm in all\ud the temperature range inspected. On the contrary, in the high magnetic field range ͑above Bm͒, the\ud effectiveness of correlated pinning is progressively reduced on lowering the temperature suggesting\ud that at low temperatures the dominant pinning contribution arises from isotropic pinning centers