ISSN 1063-780X, Plasma Physics Reports, 2011, Vol. 37, No. 11, pp. 965–971. © Pleiades Publishing, Ltd., 2011. Original Russian Text © S.I. Gritsinin, P.A. Gushchin, A.M. Davydov, I.A. Kossyi, M.S. Kotelev, 2011, published in Fizika Plazmy, 2011, Vol. 37, No. 11, pp. 1034–1040. 965 A microwave plasmatron, or a microwave spark plug (MSP), designed and fabricated at the Prokhorov General Physics Institute, Russian Academy of Sci- ences, and the Baranov Central Institute of Aviation Motors (CIAM) was tested as an alternative to stan- dard spark plugs used to ignite fuel/air mixtures in avi- ation propulsion engines [2–4]. A schematic and a photograph of the MSP are shown in Figs. 1 and 2, respectively. The plasmatron is a coaxial waveguide transporting microwave energy from magnetrons used in domestic microwave ovens to the discharge system located at the waveguide output. The microwave energy is transported at the funda- mental mode of the waveguide. The discharge system is a 20-mm-diameter disk insert made of a radiotrans- parent material (quartz). The disk diameter is equal to the inner diameter of the outer electrode. The 6-mm- diameter central electrode is inserted through an aper- ture made at the center of the disk. A special design of the discharge system ensures tight contact between the central electrode and the quartz disk. The magnetron operates at a frequency of f = 2.45 GHz in a single-pulse mode. The pulsed micro- wave power is up to 1.6 kW, and the amplitude of the electric field in the running wave is up to 1.3 kV/cm. The pulse duration varies from 5 μs to 1 ms. A typical oscillogram of the magnetron anode current is shown in Fig. 3. When operating with atmospheric-pressure gas mixtures, the supply of microwave power to the plas- matron is accompanied by the development at its end of several discharge channels adjacent to the quartz disc surface and bridging the discharge gap. For the plasmatron to operate efficiently, the discharge system should satisfy a number of requirements. An impor- tant requirement that ensures generation of plasmoids at the output of the coaxial waveguide is that the cen- tral electrode be in tight contact with the quartz disk. If there is no such contact, the MSP does not operate. In the absence of matching and adjusting elements in the MSP waveguide (which simplifies its design and makes it appreciably cheaper), the geometry of the device (the length of the coaxial waveguide, the radial dimensions of its elements, etc.) plays an important role. The plasmatron version presented in Figs. 1 and 2 was used as an igniter of a kerosene/air flow at the CIAM test bench [2–4]. The experiments were carried out with a model frontal device of a turbojet combus- tion chamber (Fig. 4) at different ignition and stabili- zation conditions. The MSP was placed at the exit of the model frontal device, which formed a fuel/air flow with a Mach number of M air = 0.1–0.35 and tempera- PLASMA DIAGNOSTICS Coaxial Microwave Plasma Source S. I. Gritsinin a , P. A. Gushchin b , A. M. Davydov a , I. A. Kossyi a , and M. S. Kotelev b a Prokhorov General Physics Institute, Russian Academy of Sciences, ul. Vavilova 38, Moscow, 119991 Russia b Gubkin State University of Oil and Gas, Leninskii pr. 65, Moscow, 11917 Russia Received March 25, 2001 Abstract—Physical principles underlying the operation of a pulsed coaxial microwave plasma source (micro- wave plasmatron) are considered. The design and parameters of the device are described, and results of exper- imental studies of the characteristics of the generated plasma are presented. The possibility of application of this type of plasmatron in gas-discharge physics is discussed. DOI: 10.1134/S1063780X11100059 Δr 1 2 3 4 5 Fig. 1. Schematic of the MSP coaxial microwave plasma- tron: (1) outer electrode, (2) quartz disk, (3) inner elec- trode, (4) discharge channels, and (5) microwave radia- tion.