IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 41, NO. 3, MARCH 2013
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Observation of Ionization Wave Refraction at a Plane-Parallel Interface Alexander E. Dubinov, Artem N. Maksimov, Nikolay A. Pylayev, and Victor D. Selemir
Abstract—Photo images of ionization waves in a disk chamber are presented in this paper. The disk chamber has a narrowing in the form of a ledge. Igniting a dc glow discharge, we observed for the first time refraction of ionization wave beams at their passage of the ledge. The refraction is similar to one of light at a plane-parallel plate. Analysis of the images confirmed the fulfillment of Snell’s law for ionization waves. Index Terms—Glow discharge, ionization waves, refraction, Snell’s law, strata.
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ONIZATION waves in weakly ionized plasma are the most common wave phenomenon in gas discharges. They appear due to ionization-overheating instability in a plasma column and could be in the form of a running or immobile sequence of bright and dark plasma layers. They are called strata. Results of many investigations of strata obtained in the experiments with long thin tubes are analyzed and presented in reviews [1]–[3] and monographs [4], [5]. In [6], the authors describe experiments on strata generation in a plasma disk of the glow discharge with radial current. Experiments have been carried out in the disk gas-discharge chamber. A cylindrical cathode was located along the lateral surface of this chamber; an anode was located in the center of the chamber. Concentric annular strata generated in such disk space could be considered as 2-D since their thickness was significantly smaller than their diameter. Authors of [7] and [8] generated and studied annular strata and the strata in the form of 2-D wave beams in larger plasma disks using radial current. It has also been found out that diffraction on the obstacles and slits, and interference similar to well known in optics and acoustics, could appear in the strata. Can strata suffer refraction at a sharp interface of two regions? Until now, there has not been an answer on this question.
Manuscript received January 18, 2013; revised January 23, 2013; accepted January 25, 2013. Date of publication February 22, 2013; date of current version March 7, 2013. A. E. Dubinov and V. D. Selemir are with the Russian Federal Nuclear Center–All-Russian Scientific and Research Institute of Experimental Physics (RFNC-VNIIEF), 607188 Sarov, Russia, and also with the Sarov State Institute of Physics and Technology (SarFTI), National Research Nuclear University MEPhI, 607186 Sarov, Russia (e-mail:
[email protected];
[email protected];
[email protected]). A. N. Maksimov and N. A. Pylayev are with the Russian Federal Nuclear Center–All-Russian Scientific and Research Institute of Experimental Physics (RFNC-VNIIEF), 607188 Sarov, Russia (e-mail:
[email protected];
[email protected]). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TPS.2013.2243761
Fig. 1. Scheme of the gas-discharge chamber: 1: cathode, 2: window, 3: anode, 4: chamber bottom, 5: ledge.
The goal of this paper is to search experimental conditions and photo recording of 2-D ionization waves refraction at a plane-parallel interface of two regions having different effective refraction indices. We took the idea of how to create sharp interface of two regions with different effective refraction indices from [9] and [10]. In these papers, the authors determined strata wavelength in long thin tubes, depending on the tube’s radius. The discovered dependence shows that the wavelength and the effective refraction index depend on the tube radius; in more general case of arbitrary tube section, on the area of the cross section of the stratified discharge channel. Thus, to form sharp interface of two regions with different refraction indices for the ionization waves, it is necessary to use the chamber with a sudden change of the transversal area of the discharge section. The experiments have been carried out in the disk gasdischarge chamber of 45-cm diameter and 5-cm height (see Fig. 1) having a quartz window on the top, of 6-cm thickness. On a sidewall of the chamber, we installed diametrical electrodes (a cathode of 2-cm diameter and an anode of 0.5-cm diameter). A dc glow discharge has been ignited in the chamber at reduced pressure in the atmosphere of air and alcohol mixture similar to [7] and [8]. In this case, the plasma column has been stratified and had the view of a 2-D wave beam similar to that observed in [8]. Locating the dielectric ledge of 2.5-cm height and 6-cm width in the chamber (see Fig. 1), we observed refraction of the wave beams similar to refraction of light at a plane-parallel plate. The ledge is just the construction element narrowing the transversal section of the discharge. Examples of images of the refracting wave beam obtained at different ledge positions and pressures, and recorded with an
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IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 41, NO. 3, MARCH 2013
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Fig. 2. Image of the refracting wave beam at the ledge (the pressure is 3 torr, the discharge current is 120 mA, and the voltage is 1200 V).
Fig. 3. Image of the refracting wave beam at the ledge (the pressure is 5 torr, the discharge current is 120 mA, and the voltage is 1150 V).
FE-280 (Olympus) camera, are presented in Figs. 2 and 3. A dozen of such images with different angles of incidence of the wave beam to the ledge has been made. Obtained images allow us to be ascertained in the validity of Snell’s law that could be written in the form sin ϕ1 / sin ϕ2 = λ2 /λ1 , where ϕi is the angle between the strata and the ledge edge, and λi is the wavelength (i.e., distance between the neighboring strata). For example, in Fig. 2, we have ϕ1 = 40◦ , ϕ2 = 27◦ , λ1 = 6.1 mm, λ2 = 7.4 mm, sin ϕ1 / sin ϕ1 = 1.42, λ2 /λ1 = 1.21, and error of Snell’s law fulfillment δ = 16.7%; and in Fig. 3, ϕ1 = 40◦ , ϕ2 = 28◦ , λ1 = 5.6 mm, λ2 = 6.8 mm, sin ϕ1 / sin ϕ2 = 1.37; λ2 /λ1 = 1.21, and error of Snell’s law fulfillment δ = 12.8%. Here, the subscript “1” is for the cathode region, and the subscript “2” is for the ledge region. In general, the law fulfillment error has not been exceeded 20%. Thus, for the first time, we showed that ionization waves can refract, and this refraction follows Snell’s law with acceptable precision.
[1] A.V. Nedospasov, “Striations,” Sov. Phys.—Usp., vol. 11, no. 2, pp. 174– 187, Feb. 1968. [2] L. Pekarek, “Ionization waves (striations) in a discharge plasma,” Sov. Phys.—Usp., vol. 11, no. 2, pp. 188–208, Feb. 1968. [3] V. I. Kolobov, “Striations in rare gas plasmas,” J. Phys. D, Appl. Phys., vol. 39, no. 24, pp. R487–R506, Dec. 2006. [4] G. A. Kurshev, V. E. Privalov, and Y. A. Fofanov, Strata in Helium–Neon Lasers. Kiev, Ukraine: Naukova Dumka, 1986 [in Russian]. [5] Y. P. Raizer, Gas Discharge Physics. Berlin, Germany: Springer-Verlag, 1991. [6] S. A. Novopashin, V. V. Radchenko, and S. Z. Sakhapov, “Threedimensional striations of a glow discharge,” IEEE Trans. Plasma Sci., vol. 36, no. 4, pp. 998–999, Aug. 2008. [7] A. E. Dubinov, A. N. Maksimov, and V. D. Selemir, “Observation of ionization wave diffraction in plasmas of air-alcohol mixtures,” Khimiya Vysokikh Energiy, vol. 47, no. 1, pp. 15–18, Jan. 2013 [in Russian]. [8] A. N. Belonogov, A. E. Dubinov, A. N. Maksimov, and V. D. Selemir, “The effects of wave optics as they are observed in ionization waves in plasma,” IEEE Trans. Plasma Sci., vol. 41, no. 1, pp. 36–42, Jan. 2013. [9] D. A. Keys and J. F. Heard, “The striated discharge,” Nature, vol. 125, no. 3165, pp. 971–972, Jun. 1930. [10] V. A. Lisovskiy, V. A. Koval, E. P. Artushenko, and V. D. Yegorenkov, “Validating the Goldstein–Wehner law for the stratified positive column of dc discharge in an undergraduate laboratory,” Eur. J. Phys., vol. 33, no. 6, pp. 1537–1545, Nov. 2012.
Alexander E. Dubinov was born in Arzamas-16, Russia, in 1958. He received the M.S.(Hons.) degree from Moscow Engineering Physics Institute (MEPhI), Moscow, Russia, in 1988 and the Ph.D. and D.Sc. degrees in physics and mathematics from the Russian Federal Nuclear Center–All-Russian Scientific and Research Institute of Experimental Physics (RFNC-VNIIEF), Sarov, Russia, in 1997 and 2004, respectively. Since 1984, he has been with RFNC-VNIIEF, where he is currently the Deputy Director of the Scientific and Technical Center of High-Energy Density Physics and Directed Radiation Fluxes. He is also currently a Professor with the Chair of Experimental Physics, Sarov State Institute of Physics and Technology (SarFTI), National Research Nuclear University MEPhI, Sarov. He has authored 3 books, more than 150 articles, and more than 80 inventions. His scientific interests are plasma physics, high-power microwave electronics, physics of nonlinear waves, and gas-discharge physics.
Artem N. Maksimov was born in 1980. He received the M.S. degree on nuclear stations and energy facilities from Nizhny Novgorod State Technical University, Nizhni Novgorod, Russia, in 2003. Since 2003, he has been with the Russian Federal Nuclear Center–All-Russian Scientific and Research Institute of Experimental Physics (RFNC-VNIIEF), Sarov, Russia, where he is currently the Research Fellow of the Scientific and Technical Center of High-Energy Density Physics and Directed Radiation Fluxes. His main scientific areas are laser methods of isotope separation and gas discharges.
DUBINOV et al.: OBSERVATION OF IONIZATION WAVE REFRACTION AT AN INTERFACE
Nikolay A. Pylayev was born in Ivanovo region, Russia, in 1983. He received the M.S. degree on technology of engineering industry from Energetic State University of Ivanovo, Ivanovo, Russia, in 2008. Since 2003, he has been with the Russian Federal Nuclear Center–All-Russian Scientific and Research Institute of Experimental Physics (RFNC-VNIIEF), Sarov, Russia, where he is currently the Design Engineer of the Scientific and Technical Center of High-Energy Density Physics and Directed Radiation Fluxes. His research activity is connected with the design of electrophysical facilities.
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Victor D. Selemir was born in Chernovtsy, Ukraine, in 1948. He received the M.S. degree from Kharkov State University, Kharkov, Ukraine, in 1972 and the D.Sc. degree in physical and mathematical sciences Russian Federal Nuclear Center–All-Russian Scientific and Research Institute of Experimental Physics (RFNC-VNIIEF), Sarov, Russia, in 2000. Since 1972, he has been with the RFNC-VNIIEF, Sarov, Russia, where he is currently the Deputy Scientific Leader and the Director of the Scientific and Technical Center of High-Energy Density Physics and Directed Radiation Fluxes. He is also currently a Professor with the Chair of Experimental Physics, Sarov State Institute of Physics and Technology (SarFTI), National Research Nuclear University MEPhI, Sarov. He has authored more than 150 articles and more than 70 inventions. His research interests are high-energy density physics, high-power pulsed electrophysics, high-power microwave electronics, and physics of particle accelerators. Dr. Selemir was twice a recipient of the State Award of Russian Federation.
