What a fantastic topic for regenerating old memories!
I just remembered the neat voltage doubler I learned about when I was
a Junior at Cal. It was in the first week of Physics 129A, a nuclear
physics course taught by Luis Alvarez. We studied accelerators first,
and modest guy that he was, Alvarez's first example of an accelerator
was one he had invented himself. It lived in the basement of the
Electrical Engineering building, Cory Hall, and was called a
"Swindletron". It took H- ions from a source at ground potential,
accelerated them through five megavolts to a thin gold stripper foil
which removed two electrons. The newly naked five MeV proton then
found itself to be five megavolts above ground, and promptly dropped
through that potential to emerge as a ten MeV proton. Ten MeV ground
to ground for a five megavolt investment, a swindle, indeed!
The technique of accelerating H- ions is still used many places today
(including our own TRIUMF accelerator here in BC). I don't know if
that particular trick was invented by Alvarez, but he was so clever
that it is possible. That was the first time I ever heard of it. At
TRIUMF we have a very large circular accelerator with circulating H-
ions. Extracting beam from a normal cyclotron is always a feat, but
extracting protons from an H- cyclotron is easy. One simply drops a
thin gold (maybe the don't use gold) foil into the beam and the
stripped protons reverse their curvature and exit the magnetic field.