Bulletin of the American Physical Society
75th Annual Gaseous Electronics Conference
Volume 67, Number 9
Monday–Friday, October 3–7, 2022;
Sendai International Center, Sendai, Japan
The session times in this program are intended for Japan Standard Time zone in Tokyo, Japan (GMT+9)
Session IF2: Discharge Physics |
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Chair: Daisuke Ogawa, Chubu University Room: Sendai International Center Sakura 2 |
Friday, October 7, 2022 10:00AM - 10:15AM Author not Attending |
IF2.00001: Rotating Surface Wave Excitation by Time-varying Phase Agitation and Amplitude Modulation using Cylindrical Resonator Ju-Hong Cha, Seong-Tae Han, DoHan Kim, Jong-Soo Kim, Chae-Hwa Shon As a planar-type microwave plasma source, surface wave plasma (SWP) which generates a specific wave mode between the plasma and a dielectric plate is mainly used. To improve plasma uniformity, it is necessary to improve the uniformity of the electric field at dielectric surface. For this purpose, a microwave source which uses rotating surface wave excitation has been developed. A higher-order mode (TE130) cylindrical cavity resonator is used for plasma generation. Electromagnetic waves generated by individual magnetron systems (phase-locked, 2.458 GHz) propagate to the cylindrical resonator via two different input ports at orthogonal positions. The cavity field rotates orthogonally when the phase difference (ϕ) is π, depending on the phase agitation frequency (~5 kHz). Based on the electric field distribution of the pill-box cavity, electromagnetic waves propagate through a hybrid type slot antenna composed of a ring and a large aperture structure. The electric field distribution of the surface wave (TM mode) formed on the dielectric window surface also rotates according to the change of phase difference. This effect is experimentally confirmed in Ar plasma at 0.1~1 Torr with total injection powers from 0.6 to 1.5 kW, which shows plasma uniformity is improved. |
Friday, October 7, 2022 10:15AM - 10:30AM |
IF2.00002: Numerical Simulation of Frequency Dependence of Millimeter-wave Discharge at Subcritical Condition Soichiro Suzuki, Masayuki Takahashi A high-power millimeter-wave irradiation induces air breakdown under atmospheric pressure. An ionization front propagates toward the beam-source direction at high speed while forming various types of discharge structures such as comb-shaped, diffusive, and filamentary patterns. The millimeter-wave discharge can be classified into overcritical and subcritical conditions according to the electric-field intensity of the millimeter-wave. Past subcritical discharge experiments reported that the propagation speed, the discharge structure, and the structural transition threshold have frequency dependence on the millimeter-wave frequency and the electric-field intensity. However, the frequency dependence has not been examined by numerical simulations because those simulations at subcritical condition could not capture the ionization process. The authors have recently developed a new model that can simulate the ionization-front propagations of millimeter-wave discharge at subcritical condition by coupling millimeter-wave propagation, plasma fluid, compressible neutral fluid, detailed chemical reaction, and radiation transfer models. The calculation results changing the beam frequency are in agreement with the trends of past discharge experiments. |
Friday, October 7, 2022 10:30AM - 10:45AM |
IF2.00003: Characterization of DC driven moderate pressure water vapor glow discharge Md Ebrahim Khalil Bhuiyan, Tanvir Farouk Despite significant studies conducted to get insight on the physicochemical processes being influenced due to trace water vapor studies involving high water vapor content is limited, which is critical for developing, and assessing water vapor kinetic models. In this study a dc driven moderate pressure glow discharge operating in 100% water vapor has been characterized. The experiments are conducted at 12 Torr with an interelectrode separation of 4 cm. Degassed, deionized water is introduced at 298K preventing any possible condensation of water vapor in the system. VI characteristics of a water vapor plasma is measured over a broad current range. The measurements show that a normal glow is established at ~8 mA having a current density of 6.32 mA/cm2 and discharge voltage of 850V. The voltage along the interelectrode separation is measured to determine the electric field in the cathode fall and the positive column. Optical emission spectrometry is performed to determine the gas temperature as well as the presence of key excited and dissociated species. Finally, experiments are also conducted for an air plasma at 12 torr and the characteristics are compared against the water vapor discharge. |
Friday, October 7, 2022 10:45AM - 11:00AM |
IF2.00004: Time evolution of NO X 2Π (ground), A 2Σ+ state and O 3P atomic ground state density in downstream of a nitrogen-oxygen pulsed microwave surfaguide discharge Abhyuday Chatterjee, Omid Samadi, Kseniia Leonova, Nikolay Britun, Rony Snyders Nitric oxide is the dominant product in low pressure N2-O2 (1:1) microwave plasma used for oxidative nitrogen fixation [1].This study was focued to understand the formation of Nitric oxide in a pulsed (500 Hz 50-50 duty cycle) 2.45 GHz surfaguide microwave discharge. Laser Induced Fluorescence(LIF) of NO was used to determine the absolute X 2Π NO ground state density over the duration of the pulse(on and off time) in the downstream. The NO X molecules were excited to A(0,0) state using a 10 Hz tuneable pulsed dye laser at 226.23 nm(frequency doubled from 452.46 nm). The fluorescence at 247 nm of A→X (0,2) was recorded using an ICCD camera with a 248/10 nm filter and a lens. The 247 nm A→X(0,2) emission [1] naturally occurring from the electronic excitation in the plasma showed reverse trend of time evolution than the X state density. O atom plays vital role in both formation and annihilation of NO in the plasma [2]*. To correlate O atomic density evolution in an identical plasma condition(2,5 Torr total pressure; 0.7 kW power) we used Two photon Absorption LIF(TALIF,excitation wavelength: 225.6 nm 2p 3P → 3p 3P ). The 844 nm fluorescence was recored with the ICCD camera with a lens and 840/10 nm bandpass filter. |
Friday, October 7, 2022 11:00AM - 11:15AM |
IF2.00005: Investigation of conditions necessary for inception of positive corona in air based on differential formulation of photoionization Victor P Pasko, Reza Janalizadeh, Jaroslav Jansky Photoionization of molecular oxygen due to extreme ultraviolet emissions of molecular nitrogen in the wavelength range 98-102.5 nm [Zheleznyak et al., High Temperature, 20, 357, 1982] is a fundamental process in initiation of positive corona discharges [e.g., Naidis, Sov. J. Plasma Phys., 13, 645, 1987]. The mathematical formulation of the positive corona problem can be found in [e.g., Naidis, J. Phys. D: Appl. Phys., 38, 2211, 2005; Liu et al., JASTP, 80, 179, 2012; Benilov et al., J. Appl. Phys., 130, 121101, 2021]. Here we present a new approach to finding inception conditions of positive corona, which is based on differential formulation of the photoionization problem [Bourdon et al., PSST, 16, 656, 2007; Janalizadeh and Pasko, PSST, 28, 105006, 2019]. We compare results with (1) previous steady-state integral formulations [e.g., Naidis, 2005; Liu et al., 2012] and (2) a time-dynamic plasma fluid model originally developed for studying ignition of streamers in a system of two colliding hydrometeors [Jansky and Pasko, JGR, 125, e2019JD031337, 2020]. Results demonstrate significance of: (1) the increase in electron density due to reduction in discharge volume near sharp point in addition to electron avalanche multiplication included in the standard integral formulations [Naidis, 2005; Liu et al., 2012]; (2) accurate representation of photoionization in small discharge volumes; (3) inaccuracy of the approximation that most of photoionizing radiation originates next to surface of coronating electrode (especially in the case of large electrode dimensions ~1 m at low air pressures < 10% of atmospheric pressure). |
Friday, October 7, 2022 11:15AM - 11:30AM |
IF2.00006: Repetitively pulsed positive streamer discharge in electronegative gas mixtures at high pressure Zheng Zhao, Xinlei Zheng, Anbang Sun, Jiangtao Li Electronegative gas components and gas pressure are two important influential factors of the evolutions of repetitively pulsed positive streamer discharge. Discharge memory effect agents may significantly change with increasing the electronegative gas components. Meanwhile, the decay and diffusion processes are dependent on the gas pressure. We experimentally investigated evolutions of repetitively pulsed positive streamer discharge in typical weak electronegative (O2) and strong electronegative (SF6) gas mixtures. Propagation features in N2 and N2-O2 mixtures are similar. The secondary streamer is accelerated under following voltage pulses than under the first voltage pulse, probably due to the effect of residual pre-ionization density on the conductivity of the primary streamer stage. Interestingly, discharge evolutions and discharge memory effects are more pronounced in N2-SF6 mixtures. A large radial deviation of the following discharge channel from the central axis could be observed. It is possibly induced by the high-density residual charges. It is preliminarily observed that the leader formation is possible under following pulses in a pulse train. It implies that the gas gap breakdown mechanism no longer follows the streamer mechanism but the leader mechanism, where the thermal process plays a decisive role. |
Friday, October 7, 2022 11:30AM - 11:45AM |
IF2.00007: Streamer discharge development in long air gaps Andrey Starikovskiy, Eduard Bazelyan, Nickolay Aleksandrov The purpose of this work is to study the factors on which the electric field in the channel can depend for long (tens of centimeters) streamers. Changes in the pulse amplitude, and voltage rise time do not cause a significant change in the field in the streamer channel, which remains at the level Ech ~ 5 kV/cm in the range from 5 kV to 1000 kV. The length of the streamer propagation essentially depends on the anode radius (through velocity). The field in the channel depends on the electrode radius only at small distances. The pulse rise time has practically no effect on the field in the channel, streamer velocity and propagation distance. The kinetics of ionization and recombination significantly change both the electric field in the channel and the propagation distance of the streamer. |
Friday, October 7, 2022 11:45AM - 12:00PM |
IF2.00008: Fluid modeling and coherent Rayleigh-Brillouin scattering measurements of gas temperature in a xenon DC glow discharge plasma Shigemitsu Suzuki, Robert Randolph, Alexandros Gerakis, Kentaro Hara Plasma fluid models that include both plasma chemistry and gas heating mechanisms are necessary to better understand the nonequilibrium nature of plasma flows in industrial plasma sources. In this talk, we present the development of a plasma fluid simulation for a weakly ionized DC glow discharge. As the characteristic times for the transport and reactions between charged (ions and electrons) and neutral species are separated, different time steps are applied to update the charged and neutral species, so that the simulation is accelerated to obtain steady-state solutions efficiently. The preliminary results of the steady-state neutral temperature profile from a 1D radial simulation are in agreement with experimental measurements obtained using coherent Rayleigh-Brillouin scattering (CRBS), in which the translational temperature of the neutral species is estimated by measuring the velocity distribution functions of neutral atoms. |
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