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Unformatted text preview: Electromagnetic fields and structure of microwave torch discharge A. Ya. Kirichenko, O. A. Suvorova Institute for Radiophysics and Electronics NAS of Ukraine, Proskury 12, 61085 Kharkov, Ukraine e-mail: [email protected] Received 25 May 2006 The paper contains experimental results obtained by the investigation of electromag- netic fields of microwave discharge created in a coaxial microwave plasmatron. A new method for mm wavebands field measurements has been proposed. The method is based on application of a weakly perturbing body and allows an observation of a electromagnetic field image in real time. By this method the existence of slow surface wave in the discharge plasma has been proved experimentally and its parameters have been determined. A theo- retical consideration of the wave propagation along the central channel axis acknowledges the experimental results. PACS : 52.80.Pi Key words : plasma, microwave discharge, surface wave, electromagnetic field distribution 1 Introduction Sources of a dense low–temperature plasma (plasmatrons) are widely used in physical experiments and engineering. In these devices, a cold working gas is blown through the discharge region. In the 1970s, it was shown that a CW 3–cm–wave- length microwave source could be used to produce a steady–state flow of a strongly nonequilibrium cold plasma at atmospheric pressure [ 1 ]. The electrodynamic struc- ture of such a plasmatron is a coaxial–to–waveguide converter (Fig. 1). The working gas (argon) is introduced into the plasmatron through a hollow inner conductor of the coaxial line. A laminar plasma torch is a continuation of the inner conductor. The spectral and some other parameters of the plasma torch in various modes of plasmatron operation were studied in [ 1 ] to [ 2 ]. The plasma torch diameter is less than 1 mm, and the torch length attains 10 mm. The plasma electron temperature is 10 4 K, the gas temperature at the plasma torch axis is 600 ÷ 1000 K, and the plasma electron density is higher than 10 14 cm- 3 . In view of parameters of such a plasmatron, it was suggested to use it as a light source for spectral analysis. The authors of [ 1 ] believe that plasma is produced due to the high electric field strength in the torch. However, the data on the structure of electromagnetic fields in the microwave plasmatron under consideration are still lacking. This is explained, first of all, by the fact that the diameter of the plasma torch is significantly smaller than the wavelength of the electromagnetic field producing the discharge. An additional difficulty is that the discharge is produced in free space, in which case there are only few methods for studying microwave fields. We note that the electrical plasma parameters in a microwave plasmatron under consideration meet the conditions for Czechoslovak Journal of Physics, Vol. 56 (2006), Suppl. B B1079 A.Ya. Kirichenko, O.A. Suvorova the propagation of a surface electromagnetic wave. The goal of this study is to in-the propagation of a surface electromagnetic wave....
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- Spring '10
- Electromagnet, Wavelength, Electromagnetic spectrum, microwave, O. A. Suvorova