Bulletin of the American Physical Society
73rd Annual Gaseous Electronics Virtual Conference
Volume 65, Number 10
Monday–Friday, October 5–9, 2020; Time Zone: Central Daylight Time, USA.
Session TR3: Plasma SourcesLive
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Chair: Svetlana Radovanov, Applied Materials |
Thursday, October 8, 2020 10:00AM - 10:15AM Live |
TR3.00001: Microwave plasma source based on plasma-metamaterial nonlinearity. Osamu Sakai, Akinori Iwai, Shigeyuki Miyagi Microwave plasmas are one of the main plasma sources applicable for various industrial material processes. Changing magnetic permeability based on metamaterial concepts [1], we verified expansion of plasma parameters as well as nonuniform profiles of microscopic parameters inside a plasma [2]. In this study, focusing on nonlinearity inherent in a plasma-metamaterial composite [3], we investigate microwave signals detected in microwave plasma with various reactor designs. When we set negative-permeability metamaterial in microwave plasma space, we detected enhancement and saturation of microwave signals as the input power was raised and nonlinear properties emerged. However, in the case without this metamaterial, the detected signals decreased in the opposite tendency. These results suggest that prediction from linear wave propagation is partially valid in both cases, but a nonlinear property emerging in high-power microwave plasma with metamaterial effects may include more rich behaviors that have not been observed so far. [1] A. Iwai, F. Righetti, B. Wang, O. Sakai and M. A. Cappelli, Phys. Plasmas 27, 023511 (2020). [2] A. Iwai, Y. Nakamura, O. Sakai and Y. Omura, Plasma Sources Sci. Technol. 29, 035012 (2020). [3] O. Sakai, J. App. Phys. 109, 084914 (2011). [Preview Abstract] |
Thursday, October 8, 2020 10:15AM - 10:45AM Live |
TR3.00002: Generation of highly-controllable versatile microwave plasma using dual resonant-cavity Invited Speaker: Hideo Sugai In near future, conventional magnetron sources are being to be replaced by digital solid-state sources at microwave frequency, which enables us to control frequency, phase, and amplitude. Based on this state-of-the-art microwave technology, we succeeded in developing a novel plasma using two resonant cavities. One is a rectangular cavity (mode:$ m=$1 at resonant frequency $f_{\mathrm{1}})$ which generates a center-high plasma. The other is a toroidal cavity ($m=$3 at $f_{\mathrm{3}})$ which generates an edge-high plasma. Injecting the microwave power (2400 - 2500 MHz) into the dual resonant-cavity, we can generate a radially uniform plasma by adjusting a ratio of the rectangular cavity power at $f_{\mathrm{1}}$ to the toroidal cavity power at $f_{\mathrm{3}}$. In addition, an azimuthally uniform plasma can be generated by rotating the resonant fields inside the two cavities. In this rotation system, a pair of microwave powers modulated in amplitude at low frequency (0.1 - 1000 Hz) is injected into each cavity. Microwave powers are supplied from dual input ports orthogonally placed on each cavity, with the modulation phase shifted by 90°. The simulations and experiments showed that the microwave cavity field and the plasma optical emission pattern are rotated at the modulation frequency. The microwave plasma of 40 cm in diameter was generated in a wide range of argon pressure (0.1- 20 Torr) with a total microwave power \textless 3 kW. Additional experiments of methane discharge will be also reported in the conference in view of applications of this novel microwave plasma to CVD process of graphene and diamond film. [Preview Abstract] |
Thursday, October 8, 2020 10:45AM - 11:00AM Live |
TR3.00003: Increasing the surface production of negative ions from nitrogen doped diamond in low pressure hydrogen plasmas G. Smith, J. Ellis, T. Gans, J. Dedrick, J. Achard, R. Issaoui, S. Doyle, A. Gibson, P. Diomede, M. Kushner, L. Tahri, R. Moussoui, C. Paranaud, C. Martin, G. Cartry Plasma negative ion sources are of interest for material surface processing and neutral beam injection. Incorporating dielectrics as plasma facing surfaces can increase plasma control, but maximising the production yield remains a challenge. In this study, we investigate the production of negative ions from nitrogen doped diamond films in a low pressure deuterium plasma via mass spectrometry and Raman spectroscopy. The incorporation of nitrogen dopant into the film increases the negative ion yield when its temperature reaches 550$^{\mathrm{o}}$C and it becomes conductive. Pulsing the bias voltage enables the enhanced yield of negative ions to be maintained at lower temperatures (30 - 450$^{\mathrm{o}}$C) when the film is otherwise non-conductive. To better understand the mechanisms for production of negative ions, we undertake fluid/Monte-Carlo simulations, implementing a chemistry set that includes 14 molecular vibrational states of hydrogen (P Diomede et al 2017 Plasma Sources Sci. Technol. 26 075007), gas heating, and a model dielectric surface. *We wish to acknowledge financial support from EPSRC (EP/L01663X/1) and the French research federation (FR-FCM). The participation of M Kushner was supported by the US National Science Foundation and the US Department of Energy's Office of Fusion Energy Science. [Preview Abstract] |
Thursday, October 8, 2020 11:00AM - 11:15AM Live |
TR3.00004: Interactions of floating-wire-assisted atmospheric-pressure H$_{\mathrm{2}}$/Ar plasma with SnO$_{\mathrm{2}}$ film on glass substrate forming spherical Sn particles Thi-Thuy-Nga Nguyen, Minoru Sasaki, Hidefumi Odaka, Takayoshi Tsutsumi, Kenji Ishikawa, Masaru Hori Tin (Sn) metal has been extracted from ores for a long time and is a highly demanded material for industrial applications To extract Sn metal from SnO$_{\mathrm{2}}$, various reduction processes required high-treatment temperatures and reducing agents such as CH$_{\mathrm{4}}$ that produces CO$_{\mathrm{2}}$ emission In this study, the floating-wire-assisted atmospheric-pressure plasma using a mixture of 0.05{\%} H$_{\mathrm{2}}$/Ar gas can reduce SnO$_{\mathrm{2}}$ film on glass substrate to form Sn spheres without using any additional heater. The H$_{\mathrm{2}}$/Ar plasma with a high electron density of 10$^{\mathrm{14}}$ cm$^{\mathrm{-3}}$, a hydrogen atom density of 10$^{\mathrm{14}}$ cm$^{\mathrm{-3}}$, and a rotational temperature of 940 K was obtained at a remote distance of 150 mm. A model for the formation of spherical Sn particles from SnO$_{\mathrm{2}}$ film on glass substrate in H$_{\mathrm{2}}$/Ar plasma is presented here. The treatment time and substrate temperature affect the expansion rate of the reduction area and the growth of Sn spheres. The results present a green method to synthesize Sn particles from SnO$_{\mathrm{2}}$ in atmospheric-pressure plasma for various applications. [Preview Abstract] |
Thursday, October 8, 2020 11:15AM - 11:30AM Live |
TR3.00005: RF-plasma H- ion sources as driver for high power accelerators Baoxi Han, Martin Stockli, Robert Welton, Syd Murray Jr., Terry Pennisi, Chris Stinson, Sarah Cousineau RF-plasma H- ion sources have become the preferred choice for driving high power accelerators that utilize accumulator rings to provide intense, time-structured beams for a variety of applications. Advancements in this technology have enabled proton accelerators to cross the megawatt threshold in beam power. The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory employs an RF-driven, Cesium-enhanced H- ion source for the present operational beam power of 1.4 MW and for the future upgrades up to 2.8 MW. This type of RF-plasma H- ion source was initially developed at Lawrence Berkeley National Laboratory and then further developed at SNS to a highly reliable, long lifetime (several months), high current (\textgreater 50 mA) H- ion source operated with 1 ms pulses at 60 Hz. The Japan Proton Accelerator Research Complex (J-PARC) is operating an RF-plasma H- ion source using SNS-type RF antenna for its beam power goal of 1.0 MW. The LANSCE accelerator at Los Alamos National Laboratory is adopting the SNS ion source to boost its beam current and availability. This talk will present the outstanding performance of the SNS ion source and discuss the advantages of RF-plasma H- ion source technology. [Preview Abstract] |
Thursday, October 8, 2020 11:30AM - 11:45AM |
TR3.00006: Measurements of material induced effects on the plasma parameters of an inductively coupled plasma. Joel Brandon, Chenhui Qu, Sang Ki Nam, Steve Shannon, Mark Kushner O2 planar inductively coupled plasmas (ICP) exhibit a characteristic heating mode within the E-H transition that exudes qualities of the gamma like heating mode of a RF CCP. The material selection for the grounded surface of a plasma has the ability to influence the duration of this heating mode via the oxygen recombination probability. Differing sets of thin metal films were exposed to a constantly running plasma eliminating possibility of interexperiment contamination. The material changes presented show a change in electron density rise time, steady state electron density, plasma potential, and electron temperatures in pulsed a planar ICP. [Preview Abstract] |
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