Breakdown in High Pressure Gases under the Effect of Nano- and Subnanosecond Highvoltage Pulses
Tech Area / Field
- PHY-PLS/Plasma Physics/Physics
- PHY-RAW/Radiofrequency Waves/Physics
3 Approved without Funding
Siberian Branch of RAS / Institute of High Current Electronics, Russia, Tomsk reg., Tomsk
- VNIIEF, Russia, N. Novgorod reg., Sarov
- University of Erlangen-Nurnberg / Department of Physics, Germany, Erlangen\nStevens Institute of Technology, USA, NJ, Hoboken\nPrinceton University / School of Engineering and Applied Science / Department of Mechanical and Aerospace Engineering, USA, NJ, Princeton
Project summaryThe purpose of the project is a research of mechanisms of the electrical breakdown in high-pressure gases under the effect of high-voltage nano-and subnanosecond pulses. The project is mainly concentrated on the physics of gas discharge. However, the investigations in subnanosecond time range can be executed if only the researchers have the corresponding pulsed generators. Therefore, a significant part of the work covers the development of instrumentation for the investigations, i.e. a subnanosecond pulsed generator. The project activity is going to be carried out along three interconnected directions that, as a matter of fact, represent the primary goals of the work.
· Investigations of the gas breakdown in the highly overvolted gaps with a voltage risetime of about 1 ns and a typical voltage up to 300 kV. Studying the breakdown mechanisms and revealing the conditions in which a subnanosecond switching time mode can be achieved.
· Development and construction of the subnanosecond high-voltage pulsed generator on the basis of the researches specified in the previous item.
· Investigations of the breakdown mechanisms under the effect of the high voltage pulses with subnanosecond pulse duration.
The area of the gas discharge, to which the project is addressed, is rather new and poorly investigated, despite of the wide prospects for the applications of the nanosecond gas discharge itself and the nanosecond and subnanosecond pulsed generators. Among the traditional applications it would be possible to mention the pumping of the solid-state and gas lasers; generation of the nanosecond electron beams, X-ray, and microwave radiation; researches in the field of radiation physics and chemistry. In recent years, considerable interest has been revealed in the pulsed generators that are used in the technology of gas and water cleaning and in non-thermal medical/biological treatment (including the effect of the nanosecond pulses on the permeability of the cell membranes).
The study of the discharge in subnanosecond time range and the development of the corresponding pulsed generators open up the new prospects. For example, it becomes possible so-called wide-band radiolocation with a usage of the subnanosecond pulses. The subnanosecond electron beams and the bursts of radiation manifest themselves as a unique instrumentation in physics of interaction of the radiation with the matter since the interaction time becomes comparable with a characteristic transient time for the elementary processes in the gases and solids. A decrease in the high voltage pulse duration results in an increase in the dielectric strength for insulating materials. Then a transfer from nano- to subnanosecond pulse range offers a possibility for developing the subminiature high-voltage facilities (for instance, the transportable X-ray apparatus and X-ray tubes for intracavitary diagnostics and therapy, and so on).
Investigations of the high-pressure gas discharge under the effect of nano- and subnanosecond pulses are of a great interest from the viewpoint of obtaining the new information on the fundamental processes that are responsible for breakdown in extremely overvolted gap. Due to working out the project the participants intend to contribute in this area.
In the course of the investigations it is planned to carry out the measurements of the delay time to breakdown and the discharge switching time. An effect of delay in switching the gap for the case of changing the polarity in the voltage pulse is also planned for studying. On the basis of the obtained information a theoretical model for switching process is going to be elaborated.
The measurements of the spatial and temporal characteristics for the fast electron beams and for the attendant X-ray radiation, which appears at the stage of the delay time to breakdown, will be undertaken. A theoretical model for interpretation of the electron beam generation mechanism will be developed.
The features of the power input in so-called corona-streamer discharge that starts burning in the gap with applying a high-voltage nanosecond pulse will be elucidated and the adequate physical model will be developed.
A set of the experiments with the pulses of subnanosecond duration is planned in the framework of the project. These experiments cover the measurements of the threshold voltages at which a considerable conductivity current appears in the gap for a regime of single pulses and a regime of high pulse repetition rate. The threshold voltages with which a surface breakdown starts developing are also will be defined.
The participants of the project have at their disposal the nanosecond pulsed generators and the high-speed instrumentation. To investigate discharges produced by subnanosecond pulses a subnanosecond high-voltage generator will be developed and constructed the Institute of High Current Electronics.
The scientific groups include in itself both the highly skilled experimental personnel and the people who have a great experience in developing the physical models and in computer modeling of the gas discharge processes. Due to the previous publications in the leading journals and reporting at the relevant international conferences the investigations of the involved groups are well known in the world scientific community. The leader of the project (Prof. Yu. Korolev, IHCE) has published four monographs on physics of pulsed gas discharges. The leader of another team (Prof. L. Babich, RFNC-VNIIEF) is also well known expert on the field of high-pressure pulsed gas discharge.
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