Conveners
Sensitivity to trapped flux: Part 1
- Akira Miyazaki (University of Manchester (GB))
- Mattia Checchin (FNAL)
Sensitivity to trapped flux: Part 2
- Akira Miyazaki (University of Manchester (GB))
- Mattia Checchin (FNAL)
The trapped flux surface resistance dependence on surface treatment, RF field and resonance frequency has been intensively studied at FNAL. The findings of this study are here presented, with a particular focus on the level of sensitivity at high fields given by the state-of-the-art high-gradient treatments such as 120C baking, N-infusion and modified 75-120C baking . Analyzing these results...
We report an overview of Cornell's measurements of residual resistance due to trapped flux in Nb3Sn and impurity-doped niobium in single-cell 1.3 GHz and 2.6 GHz TESLA-shape cavities
Surface resistance arising from trapped flux is experimentally measured, by which the sensitivity to trapped flux is derived. Measurements are carried out with single-cell L-band SRF cavities made of high-purity large-grain niobium materials, immersed in a uniform externally applied magnetic field generated by a solenoid whose axis overlaps the cavity axis. The surface resistance is found by...
"Sensitivity measurements have been performed for several
kinds of surface treatment in SRF cavities. Experimental setup
and results will be shown"
We will describe Fermilab experiments that focus on the optimization of doping parameters to achieve low sensitivity to magnetic flux while maintaining very high Q characteristic of nitrogen doped cavities and same or higher quench fields. One of the directions pursued is using lighter doping recipes which have been shown in the past to increase the mean free path of the resonator and decrease...
In this talk I discuss the RF dissipation of trapped vortices which contribute to the residual surface resistance in SRF cavities. In particular, the power caused by oscillations of flexible pinned vortex segments driven by a weak RF field, and the dependencies of the RF power on frequency, spatial distribution of pinning centers and purity of the material are considered. A brief overview of...
In this talk, I will explain the hysteretic mechanisms that are responsible for field-dependent residual losses of SRF cavities due to the motion of isolated trapped vortex lines under the action of parallel oscillating fields at the surface. By invoking collective weak pinning theory in the context of the Bardeen-Stephen model of vortex dynamics, I will present simple estimates, approximate...
