Köszegi, Julia-Marie: Surface resistance minimization in SRF cavities by reduction of thermocurrents and trapped fluxMinimierung des Oberflächenwiderstandes supraleitender HF Resonatoren durch Reduzieren von Thermoströmen und eingefangenem Magnetfluss. 2016
Inhalt
- Abstract
- Zusammenfassung
- Contents
- List of Figures
- List of Tables
- Symbols
- Abbreviations
- Introduction: Pushing Niobium to its Limits
- Basic Principles
- RF Cavities for Particle Acceleration
- RF Superconductivity
- The Origin of Superconductivity
- Phenomenology and Theoretical Descriptions
- AC Losses in Superconductors
- Knobs for the Reduction of RF Dissipation
- Trapped Magnetic Flux
- The Structure of a Flux Line
- Flux Pinning
- Losses Due to Trapped Flux
- Sources of Magnetic Field in the SRF Environment
- Thermoelectric Currents
- Experimental Methods
- Evidence of Thermoelectric Loss Contribution in Cavity Tests
- The TESLA Cavity and Its Passband Modes
- HoBiCaT Cooldown Schemes
- The BCP Cavity
- The BCS and the Residual Resistance
- Correlation of Residual Resistance and Cooling Parameters
- Spatial Distribution of the Losses
- The N-Doped Cavity
- Estimate of Thermoelectrically Generated Magnetic Field
- The Thermopower
- The Thermopower in Literature
- The Thermopower Measurement Setup (PPMS)
- Software and Data Analysis
- Results
- The Thermovoltage as a Function of Temperature
- The Thermocurrent and Its Magnetic Field
- Direct Measurement of the Magnetic Field at the RF Surface
- Change in Magnetic Field During a Cycle
- Phase Transition and Trapped Flux
- Comparison to RF Data
- Comparison to Simulations
- Discussion: Thermocurrents in SRF Cavities
- Flux Trapping and Flux Expulsion
- The Kinetics of the Phase Transition in Superconductors
- Recent Progress in SRF Science
- Tests on Samples
- Discussion: Flux Trapping and Flux Expulsion
- Summary and Outlook
- Appendices
- The Thermoelectric Effect: Charge and Heat Currents
- The Fluxgate Magnetometer in Detail
- The AMR Sensor in Detail
- Measured Thermopower Values as a Table
- AMR Sensors for SRF Application
- Bibliography
- Acknowledgements