Speaker
Description
Functionalized amorphous carbon (a-C) coatings are being developed to reduce the secondary electron emission yield (SEY) and to control the surface resistance of ceramic supports for the HL-LHC kicker magnets. Pressure spikes observed during high-voltage pulsing of the new LHC MKI Cool kicker magnets are attributed to flashovers caused by high electron emission and insufficient draining of surface charge on the alumina supports of the beam-pipe. To address this issue, the alumina supports for the next generation of MKI Cool magnets are coated with an a-C film providing suitable surface resistivity to prevent charge accumulation while preserving the insulating function of the supports, together with a low SEY.
This contribution reports on the R&D programme aimed at tuning the resistivity of the a-C films through hydrogen doping while maintaining acceptable SEY performance. Results from the production of a series of 25 coated supports are presented, along with complementary studies carried out to optimise the coating process for future large-scale production. The potential of these resistive a-C films as alternatives to Ti and TiN coatings for insulating components is also discussed.
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