G.J.J. Winands

X-ray emission in streamer-corona plasma

X-ray emission has been detected occasionally during the streamer-corona propagation in a wire-plate corona reactor open to ambient air. A 65 kV pulse with 15 ns rise time is applied to the wire anode superimposed on a 20 kV dc bias. The duration of the driving voltage pulse (110 ns) is less than 2.5 times the primary streamer transit time. Under this condition no arc discharge occurs between the wire and the cathode plates separated by 6 cm air. The onset of x-ray emission coincides with the initiation of the primary streamers near the wire anode. No x-rays were detected later, during or after the primary or secondary streamer development. X-ray energies ranged between 10 and 42 keV, as detected by a LaBr3 (Ce) scintillator–photomultiplier combination. Time resolved imaging of the streamer propagation highlights the different stages in the streamer discharge process. The energetic electrons originate near the anode, at the moment of streamer initialization.

Evaluation of Pulsed Power Sources for Plasma Generation

Abstract This paper reports repetitive pulsed power sources for generation of pulsed streamer corona and electrohydraulic spark discharge plasmas, respectively. Single- and multiple-switch circuit topologies are used for scaling the average power up. For positive streamer corona plasma, ultra-short (~ 50 ns) hybrid pulsedpower technologies have been under investigations with an industrial pilot system. For electrohydraulic spark discharge plasma, an all solid-switch pulsed power technology has been developed and introduced into the market since 2002. This paper also discusses critical circuit elements, such as heavy-duty thyristor, transmission line transformer, and triggered spark-gap switch, and their industrial applications.

Failure of polymeric light emitting diodes by controlled exposure of the polymer-cathode interface to oxygen

The influence of the controlled exposure to oxygen of the calcium cathode of polymeric light emitting diodes (pLEDs) is investigated. The LEDs are fabricated with ITO as anode, OC1C10-PPV as electroluminescent polymer, calcium as cathode and aluminium as protecting layer. The polymer layers of the LEDs are spincoated in a dry nitrogen atmosphere and transported directly into an UHV chamber where the metal electrodes are deposited by evaporation. In order to investigate the influence of the exposure to oxygen of the calcium cathode, the deposition of the calcium layer was interrupted in some cases and the samples were exposed to 30-1000?mbar of oxygen. We determined the amount of oxygen in the different layers of the I-V-light characterized pLEDs with elastic recoil detection analysis and correlated it with the characteristics of the devices. Exposing a part of the calcium layer to oxygen at layer thicknesses equal to or less than 10?nm leads to a total loss of the brightness, while exposing thicker layers or the pristine PPV does not affect the LEDs significantly.

Applications of repetitive pulsed power, research at TU/E

Summary form only given. Current pulsed plasma research at TU/e Eindhoven, Department of Electrical Engineering, focuses on the integration of pulsed power technology into processes of multidisciplinary character. Examples of such processes are sustainable energy generation, chemical processing, and plasmas in super critical media. The research area concerns three interrelated systems: power modulator (1), interfacing plasma (2) and target process (3). The main challenges are adequate energy transfer between the three systems, tuning of the plasma energy levels and durable fast switching systems. The results show that pulsed power is a reliable and controllable technology for reducing industrial emissions, for syngas conditioning and for unconventional chemical processing. Our research will shift more in the direction of pulsed power produced plasmas for sustainable technology. Plasmas, chaotic in nature and present everywhere in the universe can be tailor made in the laboratory. Such controlled pulsed plasmas create intelligent processing to facilitate the drive towards sustainability. To proceed along these lines the research has to focus on the generation of pre-defined plasmas and selective processing. Consequently, our efforts are be directed to integrating the three competence areas of plasma physics, pulsed power technology and chemical process technology. Recent results of the work will be summarized. Items will include radical efficiency of streamer phases, non-steady state chemistry, tar removal from biomass derived syngas, industrial systems for VOC reduction and plasmas under supercritical conditions.

A Repetitive Pulser with Four Spark Gap Switches

A repetitive four spark gap switches and transmission line based pulsed power generator has been developed to study the multiple switching technology. It includes 16 1.5m-long coaxial cables, four cables in parallel per switch. By means of transmission lines, the four switches can be synchronized in nanoseconds. It can produce a pulse at a high voltage or a large current. Combined with the LCR (inductor-capacitor-resistor) trigger method, the setup can be operated repetitively and very stably. The detailed experimental results will be discussed in this paper

Recent advances of power conditions for streamer corona plasma applications

Publisher Summary This chapter reviews the state-of-the-art of power conditions for streamer–corona plasma applications. It also discusses some critical issues when developing industrial systems. Based on streamer generation and interaction between power sources and reactors, the power conditions can be divided into two groups—namely, hybrid pulsed-power system (HPPS) and DC/AC. Today, single- and multiple-switch circuit topologies have become available to scaleup the HPPS system. DC/AC sources are being introduced into the market. Over the past 20 years, pulsed corona plasma system was expected to be integrated together with electrostatic precipitator for a simultaneous removal of dusts, SO 2 , NO x , and heavy metals from exhaust gases. The data available would be sufficient enough for commercial-scale design for either odor-emission control or exhaust-gas cleaning. By retrofitting available electrostatic precipitation (ESP), a plasma-based gas cleaning system to simultaneously remove polluting gases, heavy metals, and particles will be applied in the near future.

Pulsed Power Technology

Pulsed power refers to the science and technology of accumulating energy over a relatively long period of time and releasing it as a high-power pulse composed of high voltage and current over a short period of time; as such, it has extremely high power but moderately low energy. Pulsed power is produced by transferring energy generally stored in capacitors and inductors to a load very quickly through switching devices. Applications of pulsed power continue expansion into fields including the environment, recycling, energy, defense, material processing, medical treatment, plasma medicine, and food and agriculture.

A Multiple-switch Technology for High-power Pulse Discharging

This article presents our recent research on a new multiple-switch pulsed power technology. With this technique, multiple spark-gap switches can be synchronized automatically, like in Marx generator. However, in contrast to a Marx, Pulsed power can be produced either at a high voltage or with a large current, or it can be used to drive multiple independent loads simultaneously. It is promising for the development of an efficient large pulsed power supply with an increased lifetime. Through use of this technique, an efficient ten-switch prototype system has been successfully developed. Experimental results show that 10 spark-gap switches can be synchronized within about 10 ns. The system has been successfully demonstrated at repetition rates up to 300 pps (Pulses Per Second). Pulses with a rise-time of about 11 ns, a pulse width of about 55 ns, an energy of 9 J-24 J per pulse, a peak power of 300 MW-810 MW, a peak voltage of 40–77 kV, and a peak current of 6 kA-11 kA have been achieved with an energy conversion efficiency of 93%–98%.