The Spellman document you refer to is very good. That is precisely the brand of HV chain in CT picker/marconi. Also Toshiba in modern versions of Aquilion and Alexion. I use a set of Spellman multipliers (from IQ CT) as HV source in my workshop. I have sometimes disassembled multipliers (removing the silicone packing) replaced capacitors and vacuum filled with curable silicone.
The section on common faults in x-ray tubes would be expanded with the case of the 7.5 MHU Varian tubes. Violent gassing with filament breakage due to oxidation. In some cases the symptom is an arc (a slight residual vacuum remains to allow ionization) and when trying to "recover" the tube the filament breaks due to heating in the presence of gases (When performing an autopsy I have seen deposits of blue metallic oxide in the filament capsule).
