M. Rivaletto

Self-Contained, Hand-Portable, and Repetitive Ultrawideband Radiation Source

This paper presents the design and experimental results of a hand-portable, self-contained, and repetitive radiation source of high-power ultrawideband (UWB) pulses. This source consists of a deployed UWB antenna driven by a high-pulsed power (HPP) generator and powered by a self-contained 50-kV rapid charger at repetition rates up to 100 Hz. By changing the HPP generator, two different electric wave shapes with two different frequency spectra can be generated. Each HPP generator is based on the use of a repetitive Marx generator. On the one hand, a 200-kV/1.4-J Marx generator is associated with a coaxial pulse-forming stage consisting of two highly pressurized spark gap switches and a Blumlein line, which produces bipolar pulses. Its main characteristics are an output voltage of +100 kV/-100 kV and a pulsewidth of 1.5 ns. On the other hand, we have developed a second eight-stage Marx generator, where the pulse-forming stage is the last stage of the structure. It delivers pulses in the 150-kV/1-J range, with a fall time of 300 ps and an 850-ps pulse duration. Electrical signals are radiated by a deployed Valentine antenna. It is a new traveling wave antenna that is designed to radiate high-voltage repetitive pulses with the challenge of high gain and low dispersion in an extremely restricted volume. The design of a rapid charging power supply is also presented, meeting stringent package constraints while still enabling high repetition rates. It has already demonstrated its capability of charging, from a dc power battery, a 5-nF capacitance up to 50 kV in 5 ms at a 100-Hz repetition rate for some bursts of thousand pulses. The autonomy is more than 35 000 shots (depending on the number of battery packs inside). Electric field measurements were performed on the whole package to determine the figure of merit (the maximum value of far-field peak electric field strength multiplied by the distance) of the UWB source in each configuration (bipolar and monopolar sets). The figure of merit measured is 200 kV for both.

Simple and compact capacitive voltage probe for measuring voltage impulses up to 0.5 MV

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.

MOUNA: An Autonomous, Compact, High-Power, and Wideband Electromagnetic Source Based on a Novel Resonant Pulsed Transformer

Nowadays, a broad range of modern defense applications requires compact pulsed power generators to produce high-power electromagnetic waves. In a conventional design, such generators consist of a primary energy source and an antenna, separated by a power-amplification system, such as a Marx generator or a Tesla transformer, which forwards the energy from the source to the antenna. The present system, however, uses a novel and very compact high-voltage resonant pulsed transformer to drive a dipole antenna. The complete pulsed power source, termed MOUNA (French acronym for “Module Oscillant Utilisant une Nouvelle Architecture”), is composed of a set of batteries, a dc/dc converter for charging four capacitors, four synchronized spark gap switches, a resonant pulsed transformer that can generate 555 kV/265 ns pulses, an oil peaking switch and, during preliminary testing, a dipole antenna. The paper not only provides design details for each system component, but also presents the mechanical arrangement of the complete pulsed power system and the electrical diagnostics, particularly those related to measurement of the resonant transformer output waveform, the line oscillations, and the radiated electric field.

An oil peaking switch to drive a dipole antenna for wideband applications

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 power-amplifier. 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.

Compact and portable, repetitive high peak power generator for an ultra-wideband source

The development of an autonomous, repetitive, pulsed power generator is presented. This work is a coordinate effort between CEA, Pau University and Technix to develop a tightly integrated unit, including a battery pack, an intermediate dc/dc converter, a high voltage dc/dc converter, the control system and a high PRF Marx generator. Pau University has designed the Marx generator. They have built a 170 mm diameter, 330 mm length Marx generator capable of delivering 200 kV pulses into 50 Ω impedance with tens nanosecond rise times and a 100 Hz repetition rate, enabling it to drive a pulse forming line and peaking switches. The French Atomic Energy Commission has worked closely with the French company Technix in developing a rapid charging power supply to meet stringent package constraints and still permit high pulse repetition rates. This system has already demonstrated the ability to charge, from DC battery power, a 5 nF capacitance up to 50 kV in 5 ms in a burst of one thousand pulses with 100 Hz repetition rate, delivering a peak power of 3.2 kW. The autonomy is more than 35000 shots or 35 bursts. This generator is equipped with a microcontroller which is remote at a distance up to 75 m with an optical fiber interface. Details of this repetitive peak power generator are presented in this paper. Results of preliminary tests are also included.

Development of a 0.6-MV Ultracompact Magnetic Core Pulsed Transformer for High-Power Applications

The generation of high-power electromagnetic waves is one of the major applications in the field of high-intensity pulsed power. The conventional structure of a pulsed power generator contains a primary energy source and a load separated by a power-amplification system. The latter performs time compression of the slow input energy pulse and delivers a high-intensity power output to the load. Usually, either a Marx generator or a Tesla transformer is used as a power amplifier. In the present case, a system termed “module oscillant utilisant une nouvelle architecture” (MOUNA) uses an innovative and very compact resonant pulsed transformer to drive a dipole antenna. This paper describes the ultracompact multiprimary winding pulsed transformer developed in common by the Université de Pau and Hi Pulse Company that can generate voltage pulses of up to 0.6 MV, with a rise time of less than 270 ns. The transformer design has four primary windings, with two secondary windings in parallel, and a Metglas 2605SA1 amorphous iron magnetic core with an innovative biconic geometry used to optimize the leakage inductance. The overall unit has a weight of 6 kg and a volume of only 3.4 L, and this paper presents in detail its design procedure, with each of the main characteristics being separately analyzed. In particular, simple but accurate analytical calculations of both the leakage inductance and the stray capacitance between the primary and secondary windings are presented and successfully compared with CST-based results. Phenomena such as the core losses and saturation induction are also analyzed. The resonant power-amplifier output characteristics are experimentally studied when attached to a compact capacitive load, coupled to a capacitive voltage probe developed jointly with Loughborough University. Finally, an LTspice-based model of the power amplifier is introduced and its predictions are compared with results obtained from a thorough experimental study.

A 600kV resonant pulse transformer combined to a helical antenna

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 CST-based simulation is proposed to predict the performances of this wideband source.

Compact 600 kV multi-primary windings resonant transformer to drive an electromagnetic source

Modern pulsed power applications of high power microwave technology require compact power-amplifier. In each case, the high pulsed power generator is made up of a primary energy source and a load, separated by the power-amplification system that forwards the energy from this source to the load. Usually a Marx generator or a Tesla transformer is used as the power-amplifier. Our structure uses an innovative and very compact resonant transformer to drive a dipole antenna. Our 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 600 kV/265 ns pulses, an oil peaking switch and a dipole antenna. The device must transmit waveforms with a wide frequency band and a high figure-of-merit. The paper describes the compact 600 kV multi-primary windings resonant transformer developed in common by Université de Pau and Hi Pulse Company. The resonant transformer is made of four primary windings, two secondary windings in parallel and a Metglas® 2605SA1 amorphous iron magnetic core. An innovative biconic specific geometry makes it possible to optimize the leakage inductance. The transformer mechanical characteristics are: 6 kg weight, 3.4 liters volume, 20 cm diameter and 11 cm width. Design details are explained accurately. Each feature is justified. Calculations of leakage inductance and stray capacitance between primary and secondary windings are presented. Core losses and saturation induction are studied. An LTspice-based study of the power-amplifier is proposed. Finally, the results from two experimental studies are presented. Firstly, the resonant power-amplifier loaded by a compact capacitive charge associated to a homemade capacitive voltage probe specially developed is studied. Secondly, an integrated V-dot probe measures the power-amplifier output inside the electromagnetic source. To conclude, the experimental results are compared to the LTspice simulations and discussed.

Self contained source based on an innovating resonant transformer and an oil peaking switch

Nowadays, a broad range of modern industrial applications brings the necessity of compact high-power electromagnetic wave generators. Conventionally, this kind of generator consists in a primary energy source and an antenna, separated by a power-amplification system that forwards the energy from this source to the antenna. A Marx generator or a Tesla transformer is classically used as a power-amplifier. Our structure uses an innovating very compact resonant transformer.

Synchronized spark gaps combined to multi-primary windings resonant transformer for wideband applications

The generation of high-power electromagnetic waves is one of the major applications in the field of High Pulsed Power (HPP). In each case, the HPP generator is made up of a primary energy source and a load, separated by a power-amplification system that forwards the energy from this source to the load. In such a system, the main component is classically a Marx generator or a Tesla transformer for power-amplification. Our structure uses an innovating extremely compact resonant transformer. When the load is an antenna, it is possible to generate electromagnetic pulses. This paper presents the feasibility of a broadband device for electromagnetic radiations based on this new concept. Our « all electric » device is composed of a battery and a DC/DC 300V-10kV converter to load primary capacitors, four triggered spark gap switches, a four-primary resonant transformer generating pulses with a few hundreds kilovolts amplitude, an oil peaking switch in order to sharpen the rise-time of the transformer output signal and a dipole antenna. Our device must transmit waveforms with a wide frequency band. This paper presents particularly the spark gap switches synchronization, the trigger generator realization and the resonant transformer design. Various technological solutions have been tested in order to trigger with delays and jitters as short as possible (about the ten nanoseconds), the best one is presented. The influence of the amplitude and the rise time of the trigger pulse is studied. To generate the pulse trigger, a very compact Marx generator is designed and achieved. The resonant transformer is made of four primary windings, two secondary windings in parallel and a magnetic core. This specific geometry makes it possible to optimize the coupling ratio. First results concerning their combination are also presented.