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The outgassing rates of PEEK, Vespel® and Kapton® foils as a function of time and thickness have been studied through a series of pump-down tests. Samples of at least five different thicknesses for each material, exposed to normal levels of moisture in the air (30-65% R.H.), were pumped in a dedicated setup. The pump down curves were fitted with a Fickian diffusion model. A discrepancy between the model and the experimental results was observed for extended pump down time. A new empirical model was proposed and applied with excellent results. The discrepancy could be due to micro-voids in the vitreous parts of the polymers as described by the dual model.

MAX IV is presently under construction at Lund, Sweden, and the first beam for the production of synchrotron radiation is expected to circulate in 2016. The whole set of 3-GeV ring beam pipes is coated with Ti-Zr-V Non Evaporable Getter (NEG) thin film in order to fulfil the average pressure requirement of 1x10⁻⁹ mbar, despite the compact magnet layout and the large aspect ratio of the vacuum chambers. In this work, we present the optimisations of the coating process performed at CERN to coat different geometries and mechanical assembling used for the MAX IV vacuum chambers; the morphology of the thin films is analysed by Scanning Electron Microscopy; the composition and thickness is measured by Energy Dispersive X-ray analysis; the activation of the NEG thin film is monitored by X-ray Photoemission Spectroscopy; the vacuum performance of the coated beam pipes is evaluated by the measurement of hydrogen sticking coefficient. The results of the coating production characterisation for the 84 units coated at CERN are presented., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Electron-cloud is one of the main limitations for particle accelerators with positively charged beams of high intensity and short bunch spacing, as SPS at CERN. The Secondary Electron Yield (SEY) of the inner surface of the vacuum chamber is the main parameter governing the phenomenon. The effect could be eliminated by coating the magnets vacuum chambers with a material of low SEY, which does not require bake-out and is robust against air exposure. For such a purpose amorphous carbon coatings were produced by magnetron sputtering of graphite targets. They exhibit maximum SEY between 0.9 and 1.1 after air transfer to the measuring instrument. After 1 month air exposure the SEY rises to values between 1.1 and 1.4. Storage under nitrogen or by packaging in Al foil makes this increase negligible. The coatings have a similar XPS C1s spectrum for a large set of deposition parameters and exhibit an enlarged line-width compared to pure graphite. The static outgassing without bake-out depends on deposition parameters and is in a range from 1 to 10 times higher than that of stainless steel. Instead, electron stimulated outgassing is lower than for stainless steel and is dominated by CO., Proceedings of the 1st International Particle Accelerator Conference, IPAC2010, Kyoto, Japan