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The paper describes a simple and compact 0.5 MV high-voltage capacitive probe developed in common by Université de Pau (France) and Loughborough University (UK). Design details are provided, together with a simple and straightforward methodology developed to assess the characteristics of high-voltage probes. The technique uses a 4 kV pulsed arrangement combined with results from a 2D electric field solver and a thorough PSpice circuit analysis. Finally, a practical example of high-voltage measurement performed using such a probe during the development phase of a high power microwave generator is provided.

When the load is an antenna, the High Pulsed Power (HPP) generators allow generating electromagnetic waves in the form of pulses for wideband or ultra wideband applications. In this case, the HPP generator is usually made up of a primary energy source loading a power-amplification system. A Marx generator or a Tesla transformer is classically used as a poweramplifier. Our structure uses an innovating very compact resonant transformer. This power amplification device is connected to a fast switch which forwards the energy from this source to the antenna. The antenna behavior is directly linked to the performances of the main element of this whole device: an oil peaking switch.The whole device is composed of a battery set, a DC/DC 300V-10kV converter which feeds four primary capacitors with a 1.2A current, four triggered spark gap switches, a resonant transformer with four primaries generating a few hundreds kV pulses, the oil peaking switch and the dipole antenna. The device must transmit waveforms with a wide frequency band. This paper presents first the preliminary studies on an oil switch used in a transmission line setup. Several oils are studied, tested and compared. First experimental tests aimed at determining the electrical breakdown field in oils and the rise-time for conditions close to our application. The switch characteristics (breakdown voltage, breakdown electric field, rise time, etc) are thus studied for various electrodes gap distances. These results and the influence of these previous parameters on the antenna performances (antenna factor, figure-of-merit, radiated field) are predicted by CST Microwave Studio and compared to measurements.

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A complete pulsed power source, named MOUNA, is composed of a set of batteries, a DC/DC converter to charge four capacitors, four synchronized spark gap switches, a resonant transformer generating 600kV/265ns pulses, an oil peaking switch and a dipole antenna. This device must transmit waveforms with a wide frequency band and a high figure-of-merit.However, to radiate very high electric fields, the low gain of the dipole antenna is detrimental. The use of a directional antenna may improve performance really significantly focusing the radiation in a preferred direction. The main characteristics of the axial helical antenna (compactness, high gain on the axis, wideband spectrum and high impedance) make it an excellent candidate.In this paper, the first results concerning the design of the antenna (number of turns, size…), of a switch oscillator directly implemented at the output of the transformer are presented. The design of the novel radiating source composed of the MOUNA pulsed power source, the switch oscillator and the helical antenna is also described. The pulsed source and the oscillator contains in a volume of only 25 litres. Finally a CSTbased simulation is proposed to predict the performances of this wideband source.