In article ,
Harry Bloomfield writes:
Colin Wilson formulated the question :
I'm crap at electronics, but I remember a "cockroft walton ladder" being
used in several ioniser designs

AFAIK, all mains ones work that way.

As is used on EHT supplies for CRT's.

Hum, never seen that. They mostly use the flyback energy from
the line output transformer, a diode, and a capacitor formed
from the CRT's post deflection amplification electrode and the
earthed coating on the outside of the tube.

--
Andrew Gabriel