File:Cockcroft-Walton 3MV Kaiser Wilhelm Institute 1937 top view.png

English: 3 megavolt Cockcroft-Walton particle accelerator at Kaiser Wilhelm Institute of Physics in Berlin in 1937. The source claims it was the world's most powerful accelerator at the time. It consisted of two 4 stage Cockcroft-Walton voltage multiplier stacks of opposite polarity, with the high potential appearing at the top of the stacks applied to electrodes at opposite ends of an evacuated accelerator tube (not visible). Subatomic particles are accelerated to high speeds in the tube by the high potential. The black vertical segments on each stack are capacitors which store the charge, while the diagonal "rungs" between the columns are vacuum tube rectifiers called kenotrons, which only allow charge to pass in one direction. An alternating voltage of several hundred kilovolts is applied between the bottom of the columns, which act as a "charge pump" forcing charge into the top electrode. All exposed parts at high potential must have smooth gently curving surfaces to prevent corona discharge which causes leakage of current into the air. The output voltage of this machine was close to the limit for open-air electrostatic generators; even modern Cockcroft-Walton machines cannot produce more than about 5 megavolts.

Alterations to image: cloned in a small amount of wall behind lefthand column to replace overlap of adjacent picture on page.