a modified double greinacher high voltage power supply wherein the side - string capacitances thereof have an inductance associated in series therewith , the inductance / capacitance circuits being appropriately tuned to the frequency of the r - f input voltage source . preferably the center - string capacitance may have an inductance associated in series therewith , such circuit being similarly tuned . the input r - f voltage , rather than being supplied as a sine wave is supplied substantially as a square wave to the first stage and is transmitted to each of the subsequent stages substantially as a square wave .