[Amps] Ion Pumps

[g8on at btinternet.com]

At one time, there were a number of big tx's (100kW+, dating from the 1930s) over here in HF point-to-point service that used 'demountable' valves. These were continuously pumped, and had replaceable grids and filaments. My father-in-law worked on such tx's: he said that people with greasy hands were a disaster, insofar as it took far longer to pump the valves down after replacing a filament.  They would wear linen gloves when re-assembling but even so, some people's hands would still get some grease through. I was told they tried latex gloves, but lubrication on the latex (talc) was even more of a problem.
I think the filaments were pure tungsten, as there were no facilities for carburisation.
Peter G3RZP