Ruggero Vaglio
(NA)
10/8/18, 4:15 PM
Theoretical modelling of RF behavior
Recently, the improvement of RF superconducting cavities performances has motivated a considerable research effort to elucidate the effect of trapped magnetic flux. Here we will show that by introducing a non-linear pinning force in the Gittleman-Rosenblum equations for the RF power dissipation due to an external trapped magnetic field in a superconductor, we can describe most of the common...
Dr
Akira Miyazaki
(CERN and the University of Manchester)
10/8/18, 4:40 PM
Theoretical modelling of RF behavior
Since their invention, the performance of Nb film cavities has always been limited by a strong Q-slope. Recent tests at CERN of the newly developed seamless Quarter-Wave Resonator (QWR) showed an interesting decomposition of the Q-slope, which might help to explain/cure this limitation. One is caused by non-linear trapped flux oscillation in the residual component, whose surface resistance...
Dr
Mattia Checchin
(Fermilab)
10/8/18, 5:05 PM
Theoretical modelling of RF behavior
In this study, the radio-frequency complex response of trapped vortices in superconductors calculated for small values of applied radio-frequency field, will be presented. In agreement with experimental data on bulk niobium radio-frequency cavities, the calculated surface resistance shows a non-monotonic trend as a function of the mean-free-path and a sigmoidal-like trend as a function of the...
Dr
Takayuki Kubo
(KEK and ODU)
10/8/18, 5:30 PM
Theoretical modelling of RF behavior
We propose a theory of the nonlinear surface resistance of a dirty superconductor in a strong RF field, taking into account realistic materials features, such as magnetic and nonmagnetic impurities, subgap states originating from finite quasiparticle lifetimes, and a proximity-coupled normal layer at the surface. The Usadel equations with the RF pair-breaking current are solved to obtain the...
