8th International Workshop on Thin Films and New Ideas for Pushing the Limits of RF Superconductivity

Session

Theoretical modelling of RF behaviour

8 Oct 2018, 16:15

Villi Room (INFN - Laboratori Nazionali di Legnaro)

29. A simple model for the RF field dependence of the trapped flux sensitivity based on a non-linear pinning force

Ruggero Vaglio (NA)

08/10/2018, 16:15

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...

16. Two different origins of Q-slope problem in a Nb film cavity for HIE-ISOLDE

Dr Akira Miyazaki (CERN and the University of Manchester)

08/10/2018, 16:40

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...

28. Trapped flux sensitivity in the low amplitude radio-frequency regime

Dr Mattia Checchin (Fermilab)

08/10/2018, 17:05

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...

7. A theory of field-dependent surface resistance and possibilities of engineering optimal SN and SIS surface nano-structuring of the SRF cavities

Dr Takayuki Kubo (KEK and ODU)

08/10/2018, 17:30

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...