Design of solid-state Marx modulator with high duty factor for the proton beam extraction

To overcome these limitations, various solid-state Marx modulators have been proposed in recent years. The solid-state Marx modulator is a concept that substitutes HV diode and solid-state switch (metal oxide semiconductor field effect transistor; MOSFET or insulated-gate bipolar transistor; IGBT) for charging resistor, grounding resistor and spark gap switch in conventional Marx configuration. The pulse width can be adjusted flexibly and the repetition rate can be increased by using only a small portion of the energy stored in the Marx capacitors. A solid-state Marx modulator with high duty factor is proposed for the extraction of proton beam. The designed modulator has a total of 30 stages and it fires output pulses of 55 kV, 30 mA at 120 pps. The switch located in the grounding path enhances recharging efficiency and implements the crowbar function. This enables high duty operation up to 24%. We designed the overall circuit layout and the driving circuit optimized for the required performance. Each board consists of five Marx stages and a board control unit which sustains the utility power required at each stage. The control signals delivered to each stage are isolated using an optocoupler, and the gate power is supplied through the bootstrap bias supply. The structure of the driving circuit is simplified, and further variation and optimization are expected in various research fields. The Marx modulator proposed in this paper will be constructed and tested at Seoul National University.