B. Cassany

Long Life Rotating ARC Gap Coaxial Switch for MEGA-AMP, Kilo-Coulomb, High Action Switching of Multi-MJ Capacitor Banks

Titan Pulse Sciences Division (Titan) has developed and extensively tested a scaled down version of the rotating arc gap (RAG) switch that had been previously considered for the National Ignition Facility laser system capacitor banks at Lawrence Livermore National Laboratory. The new switch is a candidate for the French CEA mega-Joule laser (LMJ) power conditioning system; switching 250 kA and < 75 Cb per shot at 24 kV with an expected 10,000 shot life before major maintenance.

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.

Ultra Wideband Antennas for High Pulsed Power Applications

1.1 UWB antennas in the field of high pulsed power For the last few years, the generation of high-power electromagnetic waves has been one of the major applications of high pulsed power (HPP). It has aroused great interest in the scientific community since it is at the origin of several technological advances. Several kinds of high power radiation sources have been created. There currently appears to be a strong inclination towards compact and autonomous sources of high power microwaves (HPM) (Cadilhon et al., 2010; Pecastaing et al., 2009). The systems discussed here always consist of an electrical high pulsed power generator combined with an antenna. The HPP generator consists of a primary energy source, a power-amplification system and a pulse forming stage. It sends the energy to a suitable antenna. When this radiating element has good electromagnetic characteristics over a wide band of frequency and high dielectric strength, it is possible to generate high power electromagnetic waves in the form of pulses. The frequency band of the wave that is radiated can cover a very broad spectrum of over one decade in frequency. In this case, the technique is of undoubted interest for a wide variety of civil and military applications. Such applications can include, for example, ultra-wideband (UWB) pulse radars to detect buried mines or to rescue buried people, the production of nuclear electromagnetic pulse (NEMP) simulators for electromagnetic compatibility and vulnerability tests on electronic and IT equipment, and UWB communications systems and electromagnetic jamming, the principle of which consists of focusing high-power electromagnetic waves on an identified target to compromise the target’s mission by disrupting or destroying its electronic components. Over the years, the evolution of the R&D program for the development of HPM sources has evidenced the technological difficulties intrinsic to each elementary unit and to each of the physical parameters considered. Depending on the wave form chosen, there is in fact a very wide range of possibilities for the generation of microwave power. The only real question is

Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., “Considerations of rod-pinch diode operation in negative polarity for radiography,” in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975–978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., “Theoretical modeling and experimental characterization of a rod-pinch diode,” Phys. Plasmas 8(10), 4618–4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., “Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,” IEEE Trans. Plasma Sci. 32(5), 2004–2016 (2004). We have studied this diode at 4.5 MV...

Reproducibility Improvement on High Voltage Self-Break Water Switches

CESAR, a high current electron beam facility (800 kV, 400 kA) and AMBIORIX, a 2 MA Z-pinch driver are two of the main pulsed power facilities at CEA-CESTA in France. They use the classical technology of low-impedance generators, a Marx generator associated with a water line. One of the limitations of this kind of device is the switching process between the water lines. In order to improve the reproducibility, their first water switches were recently changed. On the basis of the work done by Puetz et al. for RITS-3 [1], the geometry of the main switch of each device, which links the intermediate storage (IS) and the pulse forming line (PFL), has been optimized. In this paper, we present the results of this modification.

Experimental study of self magnetic pinch diode as flash radiography source at 4 megavolt

The Self Magnetic Pinch (SMP) diode is a potential high-brightness X-ray source for high voltage generators (2–10 MV) that has shown good reliability for flash radiography applications [D. D. Hinchelwood et al., “High power self-pinch diode experiments for radiographic applications” IEEE Trans. Plasma Sci. 35(3), 565–572 (2007)]. We have studied this diode at about 4 MV, driven by the ASTERIX generator operated at the CEA/GRAMAT [G. Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference (1989), pp. 567–570]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode is modified in order to set up flash radiographic diodes. A previous set of radiographic experiments was carried out on ASTERIX with a Negative Polarity Rod Pinch (NPRP) diode [B. Etchessahar et al., “Study and optimization of negative polarity rod pinch d...

Prototype of a high power compact Marx generator for microwave applications

A compact pulsed power system is described. This system has been built to drive low impedance HPM sources (vircator, MILO). It consists of two Marx generators in parallel. Each Marx contains 13 bipolar (/spl plusmn/ 50 kV) stages of capacitors and switches placed in a tank filled with dielectric oil. This system stores 10 kJ and is capable of delivering a current up to 50 kA at 800 kV to a matched load. The rise time of the current is less than 100 ns. The Marx generators and the vacuum interface have a diameter of 0.8 m and a total length of 2 m. The voltage is monitored inside the oil tank by using a resistive divider, and the current is measured under vacuum with a Bdot probe. In this paper we present experimental results with a resistive load as well as data obtained when the obtained Marx generator is coupled to HPM tubes.

Wideband Patch Antenna for HPM Applications

This paper presents the design, fabrication, and characterization of a compact wideband antenna for high-power microwave applications. The antennas proposed are array of high-power wideband patches with high compactness and less than λ/10 thick. The concept developed can be fed by high-voltage signals (up to 60 kV) in repetitive operation. Two designs are produced at central frequencies of 350 MHz and 1 GHz. Their relative bandwidth is larger than 40% at 350 MHz and 25% at 1 GHz for S11 <; - 10 dB, respectively. The arrays studied produce a gain of more than 14 dB.

Repetitive auto-triggered Marx generator as the driver of an ultrawideband source

Traditional uses of the Marx generator have been limited to energy storage and delivering systems, such as charging capacitors or pulse forming lines. However, low energy, compact, high peak power Marx generators can be used as repetitive drivers for many applications. This paper presents the design, the realisation and experimental tests of a repetitive auto-triggered Marx generator expected to be the driver of a broadband radiation system. This whole system consists of a pulsed power source, i.e. a pulse forming line charged by a Marx bank and an UWB antenna array. Design of the Marx generator were planned to reach a voltage level of up to 400kV, a 200Hz repetition rate and a good reproducibility. In this way, the generator is supplied with a high voltage pulsed power supply; charging and discharging circuits were made of home-designed inductors. Furthermore, we focus on the first stage of this Marx generator in which a new simple auto-triggered spark-gap was integrated. The Marx is then combined to a forming line and a peaking spark gap to deliver rectangular output pulses with rise-times closed to 250ps.

High current fast Marx generator and vircator experiments

This paper describes a compact pulsed power generator. This system stores 10 kJ and is capable of delivering up to 40 GW to an electron diode. It has been optimized to drive high power microwaves devices that require high current. In order to limit the parasitic inductance and to reduce the rise time of the current to less than 100 ns, two Marx generators have been associated in parallel. Some typical results of vircator operation in S band are also presented.