The control of voltage in an arbitrary manner has lead to fundamental advances in fields which range from music to lasers. Such generators have traditionally been limited to a maximum voltage of 10 V. We have conceived, developed, tested and operated an arbitrary waveform generator with a range of voltages up to 720 kV. These devices have a wide variety of applicability. They are effective, high capability devices for simple square wave generation, and they also allow for a remarkable range of waveforms to be produced. The generators we have built are similar in some ways to solid state Marx generators, but with a novel charging system. The topology - but not the charging system - is also similar to the type of device described by Swanson in US Patent 4,403,197. The topology consists of a set of pulse generators arrayed in series where each pulse generator has a shunt diode. Each of the subunits can be on or off. We array the subunits in series. If M units are on at a voltage V we have voltage MV. We vary M in order to make an arbitrary voltage. The stages are truly independent, so the voltage of an individual stage device never increases due to the action of the other devices. This is in contrast to the action of switching in a series IGBT stack where one slow device will be subjected to N times its rated voltage. The main problem is to charge the stage capacitances C1...CN. We have developed a novel means of charging the stages using air core magnetic flux. We place the stages inside rings which have secondary coils on them. We arrange outside the rings - and with adequate spacing - to have a primary coil which provides a time varying axial magnetic field. The individual stages are charged with voltage multipliers connected to secondaries coupled to the magnetic field. In this paper we describe successful construction and operation of one of these devices up to 720 kV.
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