The paper presents the results of recent experimental studies. The subject of research was the discharge of atmospheric pressure in a gas stream in focused beams of microwave radiation. The radiation sources were: a gyrotron with a radiation frequency of 263 GHz and a power of up to 1 kW, a free-electron laser with a radiation frequency of 2.3 GHz and with an average power of up to 400 W. The paper presents the results of measurements and calculations of breakdown fields, the results of measuring plasma parameters in these cases. Possible applications are discussed.
The process of plasma interaction with magnetic fields of an arch configuration plays a decisive role, for example, in coronal ejections in the sun or in the interaction of the solar wind with the Earth's magnetosphere. In this work, this process is simulated in laboratory conditions. The density of the plasma in the magnetic flow tube is determined by the vacuum arc discharge current, and the electrons are additionally heated under conditions of electron cyclotron resonance by the microwave radiation of the gyrotron. A technique for diagnostics and study of the characteristics of plasma flows is proposed. Test experiments were carried out, and a number of dependencies were obtained between the given parameters of the plasma flow density and electron cyclotron heating and the features of the plasma flow propagation.
The paper describes an experimental facility for plasma physics and material science research. The system provides effective transportation of radiation from gyrotron output to the area under investigation inside the vessel, which can be arranged for specific task and equipped with different control and measurement tools. The use of this facility made it possible to realize a series of various experiments, in particular, initiating and studying the fundamental properties of a terahertz discharge, obtaining nanopowders by evaporation-condensation method, as well as measuring the dielectric properties of metal oxide powders. As a radiation source we used 0.26 THz/1 kW gyrotron, which can operate both in CW or pulse mode, gyrotron, the radiation of which can, if necessary, be focused by quasi-optical mirror into a spot with a diameter of about 2.5 mm, providing a power density of up to 20 kW/cm2 in the region of interest. The main components of the facility are described and some results of recent experiments are given.
This paper presents the results of the studies of the subthreshold discharge propagation under the action of the focused beam of sub-terahertz CW gyrotron (1 kW@0.26 THz). The discharge propagation velocity towards electromagnetic radiation was measured in various noble gases in the wide pressure range (0.1 – 2 atm) for various field intensities into the focal spot (5-15 kW/cm2). It was demonstrated that discharge velocity increase along with pressure decrease and drops with electric field decrease as it moves away from the focal spot. Typical velocity values and discharge spatial structure suggest the so-called equilibrium mechanism of discharge propagation.
Previous experiments performed in IAP RAS showed the possibility of realizing a localized (characteristic size not more than 1 mm in diameter) discharge in an inhomogeneous gas flow by focused sub-terahertz radiation beam. Plasma with an overcritical density up to 3·1016 cm - 3 was obtained. In these experiments, discharge glow was observed both in the range of vacuum (VUV) and extreme (EUV) ultraviolet. The performed experiments demonstrated that in order to increase the yield of EUV, the shorter wavelengths of heating radiation must be used. According to estimations, if the 1 THz radiation with power of several kilowatts is in a good coupling with the plasma, the plasma density will substantially exceed 1016 cm - 3 with electron temperature of the level of 50 eV. This should provide extreme ultraviolet glow of the discharge with power of about 100 W in the range 13-17 nm for xenon.
The spatial-time dynamic of THz nitrogen discharge in the background pressure range from a few torrs to one atmosphere was obtained. The work discuss issues of discharge propagation mechanism and shock wave formation. The radiation source was the gyrotron with maximum pulse power of about 40kW at frequency 0:67THz and duration 20μs. The main diagnostic tool was laser interferometry, based on the analysis of changes in the fringe structures made by a probe beam (r = 12mm at 1=e2 level) crossing the plasma cloud. The Michelson interferometer scheme with a diode laser at 532nm was used.
An extreme-ultraviolet (EUV) source based on a low-pressure discharge sustained in a magnetic trap by the high-power millimeter-wave radiation under electron-cyclotron-resonance (ECR) conditions is discussed. Multiple charged ions are efficiently generated and excited in such a discharge (tin ions injected into the trap from a vacuum-arc discharge were used) and emit line radiation in the desired wavelength range. A radiation power of 50 W into a solid angle of 4π sr in a wavelength range of 13.5 nm±1% and an efficiency of about 1% for the conversion of the microwave radiation absorbed in the plasma to the extreme ultraviolet radiation were achieved in the preliminary experiments. The article describes in detail the method of measuring EUV light emission power and background radiation. The emissivity of the plasma heated by gyrotron radiation with frequencies of 170 and 300 GHz is calculated. The proposed scheme can reduce the size of the emitting region up to ∼ 1 mm. The source can operate in both continuous and in pulsed mode.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.