Alright, itīs FKP1 again, it cost a lot of money, but is still the best way to go. This is the new 4" MMC, itīs actually 2 times the 3" MMC. Itīs 2 strings out of 15 series 220n@1250V WIMA FKP1 caps. This MMC is 30nF@18,75KV.
Here you see the old (and never finished) MMC, it was designed for 37,5nF@17,6KVAC.
Sideview of the giant MMC, still needs to be reworked someday to connect all the strings together.
Here you see the safety gap for the tank-cap