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Cleaning Strategies for Storage Rings

This presentation discusses the importance of cleaning storage ring vacuum vessels and provides strategies and processes for effective cleaning. It covers topics such as vacuum system design, material choice, surface analysis, and different cleaning and passivation processes.

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Cleaning Strategies for Storage Rings

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  1. Cleaning Strategies for Storage Rings Ron Reid Group Leader, Vacuum Science Group ASTeC CCLRC Daresbury Laboratory Warrington WA4 4AD, UK ALBA Workshop, Barcelona, 12-13th Sept 2005

  2. Why Clean Storage Ring Vacuum Vessels? • To ensure maximum transmission of particles by reducing beam-gas scattering • Lifetime limit better than other processes • To reduce scattered radiation for health & safety (bremsstralüng) • To minimise conditioning time ALBA Workshop, Barcelona, 12-13th Sept 2005

  3. Trapped Areas Solvent Trapping Vacuum System Design Issues • The Vacuum Engineer should consider the following at the design stage: • How all parts can be cleaned (initially and in service) • Component level clean • Full assembly clean • Sub-assembly clean • Cleaning Plant • Size • Robustness • Handling/Risks ALBA Workshop, Barcelona, 12-13th Sept 2005

  4. Vacuum System Design Issues • Material choice • Porosity • Effect of cleaning on tolerances • Multiple materials • Varying effects of cleaning process • Risk of electro-chemical action (galvanic cell) • Assessment of cleaning effectiveness ALBA Workshop, Barcelona, 12-13th Sept 2005

  5. Requirements for UHV/XHV • Minimise desorption • Remove ‘contaminants’ (i.e. components with high outgassing/vapour pressure) • Deplete reservoirs • Bulk gases • Surface overlayers (e.g. adventitious graphite) • Provide barriers • Bulk diffusion ALBA Workshop, Barcelona, 12-13th Sept 2005

  6. How do we know if a surface is clean? • Phenomenologically • Measure outgassing (thermal desorption) • Measure stimulated desorption (according to requirements of system) • In each case total and partial pressure measurements useful • Characterise surfaces • Surface analysis ALBA Workshop, Barcelona, 12-13th Sept 2005

  7. A Distinction • Differentiate between • Cleaning • Removal of unwanted components • Passivation • Formation of barriers • Low sticking probabilities ALBA Workshop, Barcelona, 12-13th Sept 2005

  8. Some examples of cleaning processes • Solution • Water based • Solvent based • Alcohols • Chlorinated hydrocarbons • Detergents • Etchants • Acids • Alkalis • Vacuum Baking/Firing ALBA Workshop, Barcelona, 12-13th Sept 2005

  9. Some examples of passivation • Air Baking • Electropolishing • Glow Discharge • But note that all of these have some cleaning effect! ALBA Workshop, Barcelona, 12-13th Sept 2005

  10. Some actual cleaning processes ALBA Workshop, Barcelona, 12-13th Sept 2005

  11. Results: Stainless steel contaminated then cleaned Aqueous based detergent Hydrofluoroether solvent ALBA Workshop, Barcelona, 12-13th Sept 2005

  12. Acknowledgements • Joe Herbert • Keith Middleman ALBA Workshop, Barcelona, 12-13th Sept 2005

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