2202 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 39, NO. 11, NOVEMBER 2011
Self-Organization Pattern of MicrogapAtmospheric Barrier Discharge
Tomohiko Sato, Tatsuya Hasegawa, Hiroyuki Fue, Seiji Mukaigawa, Koichi Takaki, and Tamiya Fujiwara
Abstract—Symmetric self-organized discharge filaments havebeen observed in the 140-µm-microgap dielectric barrier dis-charge between two parallel glass plates. Images of the dischargein microseconds were obtained using an intensified charge-coupleddevice (ICCD) camera. The diameters of these self-organizingfilaments, the distance between the filaments, and the approximatespeed of the moving filaments were obtained using the ICCDimages.
Index Terms—Dielectric barrier discharge (DBD), intensifiedcharge-coupled device (ICCD), microgap, plasma photonic crystal(PPC), self-organization.
P LASMA photonic crystals (PPCs) have been obtained bythe self-organization of filaments in an atmospheric dielec-
tric barrier discharge (DBD), which has attracted significantattention from researchers [1]. PPCs not only have a photonicbandgap (which intercepts a specific electromagnetic wave) andnegative refraction but also have dynamic controllability. InPPCs, it is important to determine the diameters of the self-organizing filaments, the distance between filaments, and theelectron density of the filament, because the bandgap dependsgreatly on the structure of the self-organizing discharge pattern.In this paper, the transition of the atmospheric self-organizedDBD plasma in submicrometers is investigated using an inten-sified charge-coupled device (ICCD) camera.
The microgap consists of two glass plates, each of which is5 mm wide, 20 mm long, and 0.4 mm thick. An indium tinoxide (ITO) film is evaporated on the glass plates and usedas a transparent electrode for the visible light emitted by thedischarge. The distance between the two dielectric glass plateswas set to 140 µm. The upper ITO-evaporated glass plate wasused as a powered electrode and was connected to a 100-kHz-RF power source. The lower ITO-evaporated glass plate wasconnected with grounding. The applied voltage was between570 and 963 V. Helium gas was fed into the gap between the twoparallel glass plates through a mass flow controller. The heliumgas velocity was between 1.1 and 88.9 m/s. Images of thedischarge were photographed with a digital camera (exposuretime: 500 µs) and an ICCD camera (exposure time: 100 µs).
Manuscript received December 3, 2010; accepted May 21, 2011. Date ofpublication July 14, 2011; date of current version November 9, 2011. Thiswork was supported by the Ministry of Education, Culture, Sports, Science andTechnology of Japan under Grant-in-Aid for Young Scientists 21740393.
T. Sato, H. Fue, S. Mukaigawa, K. Takaki, and T. Fujiwara are withthe Department of Electrical Engineering and Computer Science, IwateUniversity, Morioka 020-8551, Japan (e-mail: [email protected];[email protected]; [email protected]; [email protected];[email protected]).
T. Hasegawa is with Toshiba Corporation, Yokohama 230-0045, Japan(e-mail: [email protected]).
Digital Object Identifier 10.1109/TPS.2011.2158244
Fig. 1 shows the discharge as it appeared when photographedwith a digital camera using an exposure time of 500 µs. Byvarying the applied voltage and the gas flow velocity, we wereable to obtain various consistent patterns. At a relatively lowvoltage and gas flow velocity, a hexagonal pattern is generatedas shown in Fig. 1(a) that corresponds to an applied voltageof 570 V and a flow velocity of 1.1 m/s. This filament seemsto be stationary. The average diameter of this filament was0.49 mm, and the average distance between filaments was1.11 mm. In some discharge systems, a similar “stationaryhexagonal pattern” of the discharge structure has been observedby some researchers [2]. The striped pattern shown in Fig. 1(b)was observed at an applied voltage of 760 V and a gas flowvelocity of 33.3 m/s. This filament also seems to be stationary,and the distance between the filaments was 0.82 mm. At rela-tively high voltages and gas flow velocities, the discharge tendsto become uniform, as shown in Fig. 1(c) (applied voltage of963 V and gas flow velocity of 88.9 m/s).
Fig. 2 shows the discharge images that were photographedwith an ICCD camera, maintaining the same conditions asthose in Fig. 1. Stationary filaments similar in shape to those inFig. 1(a) were also observed in Fig. 2(a). The average diameterof these filaments was 0.53 mm, and the average distance be-tween them was 1.02 mm, which are almost equal to the valuesin Fig. 1. However, Fig. 2(b) is clearly different from Fig. 1(b).Although there is some distortion, the hexagonal pattern ofthe discharge structure can be clearly recognized. The averagediameter of this filament was 0.56 mm, and the average distancebetween the filaments was 0.86 mm. A uniform discharge thatis almost identical to that in Fig. 1(c) was also observed inFig. 2(c).
With respect to the differences between Figs. 1(b) and 2(b),it is thought that the filaments in the two figures approximatelyhave the same structure. In Fig. 1(b), the discharge looks like aline at an exposure time ∆t = 500 µs, despite a filamentary dis-charge appearing in Fig. 2(b). This difference may be attributedto the movement of the filament when the shutter opens inFig. 1(b). From the consideration mentioned previously, we canroughly estimate the speed of the moving filament. When weassume the movement velocity v of the filament in Fig. 2(b), themovement distance should at least be larger than the filamentspace L = 0.86 mm. It is expressed as
(L/∆t) < v.
From above, it can be concluded that the moving filament has aspeed of at least 17.2 m/s.
0093-3813/$26.00 © 2011 IEEE
SATO et al.: SELF-ORGANIZATION PATTERN OF ATMOSPHERIC BARRIER DISCHARGE 2203
Fig. 1. Digital camera images of the discharge observed with varying applied voltage amplitude and helium gas velocity (exposure time: 500 µs). (a) 570 V,1.1 m/s. (b) 760 V, 33.3 m/s. (c) 963 V, 88.9 m/s.
Fig. 2. ICCD images of the discharge observed with varying applied voltage amplitude and helium gas velocity (exposure time: 100 µs). (a) 570 V, 1.1 m/s.(b) 760 V, 33.3 m/s. (c) 963 V, 88.9 m/s.
REFERENCES
[1] W. Fan, X. Zhang, and L. Dong, “Two-dimensional plasma photoniccrystals in dielectric barrier discharge,” Phys. Plasmas, vol. 17, no. 11,p. 113 501, Nov. 2010.
[2] E. Ammelt, Y. A. Astrov, and H.-G. Purwins, “Hexagon structures in atwo-dimensional dc-driven gas discharge system,” Phys. Rev. E, Stat. Phys.Plasmas Fluids Relat. Interdiscip. Top., vol. 58, no. 6, pp. 7109–7117,Dec. 1998.
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