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Enhancing Accelerator Material Data: Outgassing Analysis and Recommendations

This study by E. Hedlund from Uppsala University, Sweden, emphasizes the importance of outgassing data for accelerator and storage ring experiments. It discusses measuring practices, database creation, and future outlook. The conclusions stress the need for more comprehensive outgassing information and a freely available database with specific parameters. Various outgassing methods and their challenges are explored, alongside recommended practices for accurate measurements. The study highlights the influence of surface conditions and the role of diffusion in outgassing from materials. It suggests strategies for improving data availability and quality, including increasing bakeout temperatures and finding lower outgassing glues. Additionally, it proposes a metrology approach for outgassing analysis through consistent round-robin studies.

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Enhancing Accelerator Material Data: Outgassing Analysis and Recommendations

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  1. The need for more outgassing data of materials for accelerators and storage ring experiments E. Hedlund Uppsala University, Sweden SP-Swedish Testing and Research Institute

  2. Outline • Outgassing properties of materials • Recommended practices for outgassing measurements • Measurement accuracy • Create a database for outgassing measurement • Outlook

  3. 16th IUVSTA Workshop Outgassing properties of materials Conclusions: • Better correlation between outgassing measurements and the morphology and chemical structure of the surface and near surface layers • Identification of the chemical state of H2O on or near the surface. • Measurement of the sticking coefficient of H2O on practical surfaces (steel and Al) as a function of surface conditions

  4. Conclusions… • Influence of deposited passivation layers of outgassing • Measurements and corresponding modeling of outgassing from model systems • Experiments that could identify and quantify the role of diffusion in the near-surface region of vacuum materials

  5. From this we can conclude: • Lack of published outgassing data • Need for a freely available database with e.g. following parameters: Precise material, surface and bulk treatments, surface structure, cleaning, heat treatment etc.

  6. Outgassing methods • Throughput method • Conductance modulation method • Two-path method • Gas ackumulation method • Mass-loss measurements ”Recommended practices for measuring and reporting outgassing data” by P. A. Redhead in J. Vac. Sci. Technol. A 20(2002) 1667-1675

  7. CHICSi

  8. Outgassing methods • Method: pump down for a certain time and observe the final pressure. • Must know the pumping speed at the chamber, which gives larger uncertainty.

  9. CHICSi • Problem to find data for conductive and non-conductive glue, printed circuit boards and insulators • NASA: Total Mass Loss (TML) Collected Volatile Condensable Material (CVCM)

  10. Type Weight Bake-out in air Bake-out in vacuum H2 H2O CO CO2 CH4 Total out-gassing rate (g] Temp(ºC ] Time (h ] Temp (ºC) Time (h) (mbar l /s g) (mbar l /s g) (mbar l /s g) (mbar l /s g) (mbar l /s g) rate (mbar l /s g) 377 1.15 90 1.5 1.410-6 377 1.15 90 1.5 150 24 1.3 10-9 1.8 10-10 2.0 10-10 4 10-11 610-11 410-9 H20E 2.16 90 1.5 410-7 1.6 10-7 610-8 810-9 610-7 H20E 2.16 90 1.5 150 24 4 10-11 1.2 10-9 3 10-10 2 10-10 1.4 10-10 7 10-9 H27D 3.90 90 1.5 1.110-6 H27D 3.90 90 1.5 150 24 3 10-7 Outgassing from glue

  11. Printed circuit boards Kapton Ceramics FR-4 Glass reinforced kapton Kapton insulated band cable

  12. Outgassing from printed circuit boards

  13. Outlook • Increase bakeout temperature for the whole system to 200 ˚C or possibly 300 ˚C. • Search for conductive and non-conductive glue with lower outgassing rate • Find a new type of a flexible multi-layer bandcable

  14. Outgassing metrology • Round robin study of outgassing: - materials from same batch, - same surface treatment - run at experimental facilities in different laboratories • Create a database (only UHV?)

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