In 1932 Cockcroft and Walton did not have semiconductor diodes, but vacuum-tube diodes and triodes were common. As C & W's accelerator demanded a steady potential, their power-supply design would not have used spark gaps as switches. Possibly you are thinking here of a Marx generator; a high-energy device typically used to deliver short, high-voltage, high-current pulses into a load. C & W's first schematic was used only to illustrate the principle of the thing and used switch symbols for simplicity. The actual multipliers used vacuum tubes exclusively.

C & W's "atom-smasher" accelerated charged particles exclusively by means of electric fields. As the actual flow of ions to the target represented a negligible current - a few microamps at most - it was only necessary for the power supply to deliver a few tens of microamps at the required voltage. Most of this current was due to leakage and not ion current.

Their first multiplier design (see below) featured four vacuum-tube diodes and two triodes (note the absence of circles around the cathode/anode pairs in all the schematics. Vacuum-tube symbols later evolved to include an enclosing circle to denote a sealed envelope). C & W abandoned their first multiplier design in favor of one that used diodes exclusively. In1932, triodes that could withstand 200 kV to 400 kV were simply unavailable. Clearly a different approach was needed.

C & W's second design not only eliminated the triodes, but also reduced to half the voltage seen by the various components. In their final submission to Proceedings of the Royal Society, C & W used two schematics (below) to illustrate both the new multiplier design and the transport of charge between two successive stages in the multiplication process:

Although it may seem this discussion has gotten a bit off-topic, C-W voltage multipliers do parallel the notion of motors being in "series" - the second motor mounted on the shaft of the first, the third on the shaft of the second, etc, although perhaps a better analogy might be one of high-speed elevators atop high-speed elevators.

-e