Portable & Low Cost Giga-Watt Pulsed Power Source for Intense Electron Beam Generation

An alternative approach for applications requiring production of intense electron beam without using conventional configuration of Marx/Tesla accompanying Pulse Forming Line has been explored. The developed portable system utilizes four stage Blumlein pulse forming network made from inexpensive commercially available URM-67 coaxial cables having characteristic impedance of 50Omega. All stages are charged in parallel and then synchronously discharged through single low inductance railgap switch. Use of low jitter (<5 ns) railgap switch allows synchronization with other events and improves reproducibility of the system. Each stage of Blumlein is configured as eight parallel pulse forming network, with a resultant output impedance of 6.25 Omega per stage. For four stages the output impedance is therefore 25 Omega. A 24 V battery driven 50 kV DC to DC Converter has been used for charging the system. The generator is capable of delivering power up to 200 kV, 4 kA across matched load of 50 Omega. The voltage pulse duration and rise time are 50 ns and 8 ns respectively. In the presented paper, generator construction has been described and performance of the system is evaluated to realize adverse effect of parasitic impedance on the voltage gain and pulse shape. Also its operation has been simulated by PSPICE circuit simulator program and good agreement has been obtained between simulated and experimental results. The entire cost of the generator including raw material and labor is under US $2500. Other than low cost of the generator, added advantage of cable based system is that - the slow DC charging of transmission line to a known voltage eliminates the possibility of diode voltage prepulse in electron beam generation experiments. Applications of this pulse generator also include flash X- ray generation, breakdown tests, ion implantation, streamer discharge studies, ultra wideband generation etc.