Bulletin of the American Physical Society
66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013; Princeton, New Jersey
Session ET1: Glows: dc, pulsed, microwave, others |
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Chair: Sergey Macheret, Lockheed Martin Aeronautics Co Room: Ballroom I |
Tuesday, October 1, 2013 1:30PM - 1:45PM |
ET1.00001: Properties of linear microwave plasma sustained by coaxial TEM waveguide Moon-Ki Han, Kwon-Sang Seo, Dong Hyun Kim, Hae June Lee, Ho-Jun Lee A linear 2.45GHz microwave plasma sustained by coaxial circular TEM waveguide has been developed for the low temperature large area plasma enhanced chemical vapor deposition application. TE-TEM microwave power coupling was achieved by copper rod located at $\lambda_{\mathrm{g}}$/4 from short-end of TE$_{10}$ waveguide. TEM waveguide consists of quartz tube surrounded by plasma and copper rod electrode. TEM waveguide is 60 cm in length and 3 cm in diameter, which is terminated with shorted metal cap. For the operation condition of 300 W input power and Ar pressure of 200 mTorr, a clear standing wave pattern with wavelength of 10 cm was observed. Measured plasma density and temperature at 5 cm from quartz wall was 1.2 $\times$ 10$^{17}$/cm$^{3}$ and 1.7 eV respectively. Density non-uniformity was less than 6{\%} along quartz tube in spite of standing wave set-up. In addition, properties of the microwave source are also investigated through electromagnetic field simulation coupled with drift-diffusion approximation of plasma. Calculated and measured standing wave pattern was almost identical. Electron density and temperature distribution show similar behavior with experimental results. S$_{11}$ value of input port of TE$_{10}$ waveguide was calculated as 17dB. [Preview Abstract] |
Tuesday, October 1, 2013 1:45PM - 2:00PM |
ET1.00002: Kinetic simulation of subnanosecond current front rise in high-voltage pulse open discharge Irina Schweigert, A.L. Alexandrov, P. A. Bokhan, Dm. E. Zakrevsky Generation of high-power electrical pulses with nanosecond front rise times is widely used in various applications. In this work in kinetic simulation we study the switching performance of moderate-pressure open discharge in helium for the experimental conditions [1]. The discharge ignition (with current front rises) takes place during time t \textless\ 1 ns after applying few kilovolts voltage. This phenomenon of high-efficiency generation of electron beams was studied previously and based on the effect of runaway of electrons. The discharge has a plane geometry and glows in a narrow gap (of width less than 1 cm) between two cathodes and a grid anode between them. The mechanism providing the high-efficiently electron generation is related to the fast excitation of atoms and transport of the photons to the cathodes without reabsorption. In calculations, the motion of electrons, ions and fast neutrals is simulated, solving the kinetic equations and Poisson equation with PIC MCC method self-consistently. The ionization and excitation of atoms takes place after collisions of neutrals with electrons, ions and fast neutrals. \\[4pt] [1] P.A. Bokhan, P.P. Gugin, M.A. Lavrukhin, and Dm.E. Zakrevsky, Phys. Plasma, \textbf{20}, 033507, (2013). [Preview Abstract] |
Tuesday, October 1, 2013 2:00PM - 2:15PM |
ET1.00003: Bifurcation of electron density in microwave plasma source with negative-permeability metamaterial Osamu Sakai, Yoshihiko Nakamura High electron-density plasmas beyond cutoff density were generated by high-power microwaves in a negative-permeability space, in which negative permittivity achieved in high density plasma makes refractive index real and negative. Experimental results using a high power microwave source and negative-permeability metamaterials verify that this plasma generation is in bifurcated states: high density and low density cases. This indicates that the process is quite nonlinear, partly predicted by our previous study [1]. When we made the permeability positive, we did not see such clear bifurcations. Furthermore, after high-density plasma generation, transmitted microwaves increased, which is quite abnormal in usual microwave plasma sources. Our previous report [2] demonstrates ``plasma metamaterials'' which include array of microplasmas and metallic microstructures with functional roles as media of electromagnetic waves with small amplitudes. The state of plasmas generated by high-power microwaves and immersed in the metallic metamaterial microstructures will open novel functions of plasma metamaterials; they are nonlinear metamaterials for scientific interests, potential high-density microwave sources for plasma processing, and potential switches for high-power microwaves. \\[4pt] [1] O. Sakai et al., J. Appl. Phys., vol. 109 (2011), 084914.\\[0pt] [2] O. Sakai et al., Plasma Sources Sci. Technol., vol. 21 (2012), 013001. [Preview Abstract] |
Tuesday, October 1, 2013 2:15PM - 2:30PM |
ET1.00004: Plasmas created by UV illumination rather than electron impact Raoul Franklin Some of the early experimental work in fusion concerned itself with problems of current limitation and neutral gas depletion, and so was carried out in mercury gas discharges at very low pressures. We return to such a situation and examine it where the plasma is generated by ultra-violet illumination in mercury and develop equations to describe it. The cases of full illumination and partial illumination are considered. These equations are not very different from those conventionally used to describe low pressure gas discharges, but when examined in different geometries throw up problems not necessarily anticipated. So we have examined the situation in different geometries, stimulated by the fact that in the unilluminated region in the quasi-neutral approximation gives rise to a plasma of undefined extent with uniform density and constant drift speeds. We have obtained results in cylindrical geometry, which we believe are asymptotically correct and describe such plasmas. [Preview Abstract] |
Tuesday, October 1, 2013 2:30PM - 2:45PM |
ET1.00005: Resonance Ionization Instability in HF and Microwave Discharges Sergey Dvinin, Vitaliy Dovzhenko For the first time ionization instability of HF plasma has been described in [1]. Later it has been shown [2] that in the spatially limited low pressure microwave discharge the given instability leads not only to change plasma structure, but to appearance of resonances at electron densities, when the size of plasma becomes multiple to some number of half waves of the standing surface wave, exciting on plasma boundary. Evolution of electron density perturbation is defined by two processes -- negative feedback owing to a total current continuity (as in striations) and positive one due to excitation of a wave, which is close to a resonance. In the given work the theory [2] has been improved with accounting of both processes that has allowed to reach better coincidence with experiment [3]. In addition, the general theory of ionization instability has been developed. Application of the model to CCP HF (100 MHz and higher) discharge with large electrodes has shown that excitation of the instability accompanied by surface waves, propagating along plasma-sheath-electrodes interface, is possible. \\[4pt] [1] V.B. Gildenburg, A.V. Kim. XI ICPIG. Berlin, 1976, 273.\\[0pt] [2] S. Dvinin, et al. Sov. Phys.: Fizika Plazmy, 8, 1982, 1228, 9, 1983, 1058.\\[0pt] [3] S. Dvinin et al, Sov. Phys.: Fizika Plazmy, 9, 1983, 1297. [Preview Abstract] |
Tuesday, October 1, 2013 2:45PM - 3:00PM |
ET1.00006: A two-dimensional plasma model for a coaxial microwave discharge Sara Rahimi, Manuel Jimenez-Diaz, Simon H\"{u}bner, Efe H. Kemaneci, Joost J.J.A van der Mullen, Jan van Dijk We present a two-dimensional plasma model for a coaxial microwave discharge. The microwave energy at driving frequency of 2.45~GHz is fed into a coaxial configuration in which the plasma acts as an outer conductor in such a way that a spatially extended surface wave is created. This geometry permits large surface treatment especially if a set of such coaxial lines is used. The 2D model based on the Plasimo toolkit describes the coaxial discharge self consistently. The model for argon as working gas is validated with experimental results for the electron density and temperature obtained by Thomson Scattering. The model is implemented for SiH4/H2 and is used to study the influence of various working conditions. [Preview Abstract] |
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