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

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

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

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

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.

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

CHICSi

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.

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)

Outgassing from glue H2 H2O CO CO2 CH4 rate 377 1.15 90 1.5 1.410-6 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) rate 377 1.15 90 1.5 1.410-6 150 24 1.3 10-9 1.8 10-10 2.0 4 10-11 610-11 410-9 H20E 2.16 410-7 1.6 10-7 610-8 810-9 610-7 4 10-11 1.2 3 2 1.4 7 10-9 H27D 3.90 1.110-6 3 10-7

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

Outgassing from printed circuit boards Materials Area Bake-out H H2O CO Total outgassing rate cm2 Air ºC Time h Vacuum ºC Time h mbar l/ cm2s Pyralux (2 layers) 19 150 20 210-8 410-10 310-9 310-8 AP (2 layers) 98 210-10 410-11 310-10 110-9 Epoxy-Acrylic (2 layers) 30 110-10 Epoxy-Glass fibre, 1 layer 36 210-9 Alumina (14 layer electrical print) 32 3·10-10 Glass reinforced Kapton 74 24 210-11 FR4 (4 layers) 475 1.510-11 FR4 331 610-10 23 210-13 610-11 77 410-12 FR4 – 6 layers 120 <110-10 510-10

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

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?)