Studies of Asperity-Scale Plasma Discharge Phenomena

Albright, Javan; Raja, Laxminarayan L.; Manley, Matthew Halperin; Ravi‐Chandar, K.; Satapathy, S.

doi:10.1109/tps.2011.2141689

“…This is due to the fact that the MCD thruster operates at pressures ∼40 kPa and discharge gaps ∼100 µm which corresponds to a pd (pressure×discharge gap) ∼3 Torr cm. Field emission is seen to play an important role in discharges with extremely small inter electrode distances typically at a pd ∼ 0.2 Torr cm [14]. Secondary electron emission due to electron impact is also neglected here.…”

Section: Plasma Governing Equationsmentioning

confidence: 99%

Simulation studies of RF excited micro-cavity discharges for micro-propulsion applications

Sitaraman¹,

Raja²

2012

J. Phys. D: Appl. Phys.

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A detailed computational modelling study of the micro-cavity discharge (MCD) thruster is presented. The MCD thruster concept incorporates a microdischarge with dielectric covered electrodes operated using alternating current (ac) excitation. The thruster geometry comprises a constant area pipe section followed by a divergent micro-nozzle. Two ring electrodes are embedded in the wall of the pipe section with the downstream electrode close to the pipe-micronozzle intersection. A microdischarge plasma is generated in argon propellant gas flowing through the thruster. A detailed plasma dynamics model coupled with the compressible Navier-Stokes equations is used to study the flow and plasma phenomenon in the thruster. Results show a highly pulsed microdischarge with plasma densities of ∼10 19 m −3 and current densities ∼700 mA cm −2 for an ac excitation in the radio frequency (RF) regime of 10 and 20 MHz. The dominant gas heating mechanism in these discharges is through ion Joule heating. Higher electron densities and spatially dominant thermal source terms are observed for the 20 MHz excitation compared with 10 MHz excitation. The addition of 20% nitrogen to the flow resulted in much better performance compared with the pure argon cases. A peak gas temperature rise ∼200 K is seen for a cycle-averaged power deposition of 76 mW. For the conditions explored in this study, the overall specific impulse of the thruster operating with the microdischarge plasma is found to be about 25% higher than a corresponding cold gas case.

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“…2 below pd~2 Torr.cm. Recent experiments, however, have shown that the breakdown voltage decreases monotonously for small gaps [19][20][21][22][23][24] that are less than 10 μm in 1 Atmosphere in air. The cause of this behavior is attributed to ion-enhanced field emission that occurs as the positive ions approach the negative electrode (cathode).…”

Section: Fig 2: Paschen Curves For 5 Different Gases Of Importance Imentioning

confidence: 96%

“…As the gap distance is reduced below 10 μm at 1 atmosphere in nitrogen, the Paschen curve predicts very large breakdown voltages that is experimentally shown not to be accurate. The ion-assisted field emission takes over in this regime and lowers the breakdown voltage considerably [19][20][21][22][23][24]. If it wasn't for the ionassisted emission process, it would have been impossible to realize MPDs with single digit breakdown voltages.…”

Section: Introductionmentioning

confidence: 99%

Microplasma Field Effect Transistors

Tabib-Azar¹,

Pai²

2017

Preprint

0

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Micro plasma devices (MPD) with power gains are of interest in applications involving operations in the presence of ionizing radiations, in propulsion, in control, amplification of high power electromagnetic waves, and in metamaterials for energy management. Here we review and discuss MPDs with an emphasis on new architectures that have evolved during the past 7 years. Devices with programmable impact ionization rates and programmable boundaries are developed to control the plasma ignition voltage and current to achieve power gain. Plasma devices with 1-10 μm gaps are shown to operate in the sub-Paschen regime in atmospheric pressures where ion-assisted field emission results in a breakdown voltage that linearly depends on the gap distance in contrast to the exponential dependence dictated by the Paschen curve. Small gap devices offer higher operation frequencies at low operation voltages with applications in metamaterial skins for energy management and in harsh environment inside nuclear reactors and in space. In addition to analog plasma devices, logic gates, digital circuits, and distributed amplifiers are also discussed.Index Terms-Plasma devices; atmospheric-pressure plasmas; glow discharge devices; power amplifiers; terahertz switches I. INTRODUCTIONPlasmas are extensively studied during the past century [1]. Their applications in large-scale devices for fusion, and small-scale devices in switches are well accomplished and developed. Here, we concentrate on cold plasmas that can be easily generated in a small (< 1 mm 3 ) volume with moderate electrical powers of less than 5 Watts and discuss their applications in devices similar to diodes, MOSFETs and digital and analog three-terminal devices with power gains for amplification of signals. Except in distributed plasma devices and in magnetic field sensors, we only consider non-magnetized plasmas. For the most part, we assume that the plasma is quasi-neutral and it is generated at atmospheric pressures that range from 0.6 to 1.1 atmosphere.Microplasma devices have received a renewed attention in the past 5-7 years owing to their potential applications in harsh environment. Important features that make plasma devices attractive are: a) their very large off-to-on resistance ratios (10 10 Ω/0.1 Ω), b) the ability to conduct very large currents, c) the ability to operate at very high temperatures (can be as high as 1000 o C), d) improved operation in the presence of ionizing radiation, e) the ability to traverse shortest "electrical" distance between their anode and cathode (this property can be used to solve "shortest" path problems) [2], and f) the ability to form programmable electrically conducting paths making them suitable for reconfigurable antennas and circuits [3]. MPDs are also being explored in developing chip-scale electron beam accelerators and a 100 GeV electron accelerators has already been demonstrated [4].Microplasma devices are currently used in displays [5], light sources [6], ionization devices for chemical analysis [7], material processing [...

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“…As the gap distance is reduced below 10 μm at 1 atmosphere in nitrogen, the Paschen curve predicts very large breakdown voltages, which is experimentally shown not to be accurate. The ion-assisted field emission takes over in this regime and lowers the breakdown voltage considerably [ 19 , 20 , 21 , 22 , 23 , 24 ]. If it were not for the ion-assisted emission process, it would have been impossible to realize MPDs with single digit breakdown voltages.…”

Section: Introductionmentioning

confidence: 99%

“…Thus the breakdown voltage increases as indicated by the above equations and shown in Figure 2 below pd ≈ 2 Torr·cm. Recent experiments, however, have shown that the breakdown voltage decreases monotonously for small gaps [ 19 , 20 , 21 , 22 , 23 , 24 ] that are less than 10 μm in 1 Atmosphere in air. The cause of this behavior is attributed to ion-enhanced field emission that occurs as the positive ions approach the negative electrode (cathode).…”

Section: Introductionmentioning

confidence: 99%

Microplasma Field Effect Transistors

Tabib-Azar

¹

,

Pai

²

2017

View full text Add to dashboard Cite

Micro plasma devices (MPD) with power gains are of interest in applications involving operations in the presence of ionizing radiations, in propulsion, in control, amplification of high power electromagnetic waves, and in metamaterials for energy management. Here, we review and discuss MPDs with an emphasis on new architectures that have evolved during the past seven years. Devices with programmable impact ionization rates and programmable boundaries are developed to control the plasma ignition voltage and current to achieve power gain. Plasma devices with 1–10 μm gaps are shown to operate in the sub-Paschen regime in atmospheric pressures where ion-assisted field emission results in a breakdown voltage that linearly depends on the gap distance in contrast to the exponential dependence dictated by the Paschen curve. Small gap devices offer higher operation frequencies at low operation voltages with applications in metamaterial skins for energy management and in harsh environment inside nuclear reactors and in space. In addition to analog plasma devices, logic gates, digital circuits, and distributed amplifiers are also discussed.

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Studies of Asperity-Scale Plasma Discharge Phenomena

Cited by 6 publications

References 20 publications

Simulation studies of RF excited micro-cavity discharges for micro-propulsion applications

Simulation studies of RF excited micro-cavity discharges for micro-propulsion applications

Microplasma Field Effect Transistors

Microplasma Field Effect Transistors

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