Bulletin of the American Physical Society
70th Annual Gaseous Electronics Conference
Volume 62, Number 10
Monday–Friday, November 6–10, 2017; Pittsburgh, Pennsylvania
Session DT2: Diagnostics I |
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Chair: Vince Donnelly, University of Houston Room: Duquesne |
Tuesday, November 7, 2017 8:00AM - 8:15AM |
DT2.00001: Electron neutral collision frequency measurements with the hairpin resonator probe David Peterson, Philip Kraus, Thai Cheng Chua, Steven Shannon Electron neutral collision frequency is measured over pressures ranging from 0.1-2.0 Torr in Ar, He, Ar-He, and N$_{\mathrm{2}}$ plasmas. Measurements are made with both grounded and fully floating hairpin resonator probes in a symmetric parallel plate capacitively coupled system driven at 27 MHz. The analysis treats the hairpin probe as open circuit two wire transmission line immersed in a dielectric medium. Results are compared to hybrid plasma equipment module (HPEM) simulations, showing good agreement with simulated collision frequency. Appropriate sheath models are shown to be a factor in determining measured quantities. Additionally, models that either include or neglect the RF sheath are compared for grounded and floating probes, respectively. The possibility of inferring both mean electron energy and dissociation fractions in N$_{\mathrm{2}}$ from measured collision frequency is also briefly discussed. [Preview Abstract] |
Tuesday, November 7, 2017 8:15AM - 8:30AM |
DT2.00002: A Kinetic Approach to the study of Ideal Multipole Resonance Probe Junbo Gong, Sebastian Wilczek, Jens Oberrath, Denis Eremin, Michael Friedrichs, Ralf Peter Brinkmann Active Plasma Resonance Spectroscopy (APRS) denotes a class of industry-compatible plasma diagnostic methods which utilize the natural ability of plasmas to resonate on or near the electron plasma frequency. One particular realization of APRS with a high degree of geometric and electric symmetry is Multipole Resonance Probe (MRP). The Ideal MRP (IMRP) is an even more symmetric idealization which is suited for theoretical investigations. In this work, a spectral kinetic scheme is presented to investigate the behavior of the IMRP in the low pressure regime. The scheme consists of two modules, the particles pusher and the field solver. The particle pusher integrates the equations of motion for the studied particles. The Poisson solver determines the electric field at each particle position. The fluid model is studied to provide the initial conditions of simulation for optimization reason. The proposed method overcomes the limitation of the cold plasma model and covers kinetic effects like collisionless damping. [Preview Abstract] |
Tuesday, November 7, 2017 8:30AM - 8:45AM |
DT2.00003: Planar Multipole Resonance Probe: A kinetic model based on a functional analytic description Michael Friedrichs, Ralf Peter Brinkmann, Jens Oberrath Measuring plasma parameters, e.g. electron density and electron temperature, is an important procedure to verify the stability and behavior of a plasma process. For this purpose the multipole resonance probe (MRP) represents a satisfying solution. However, the influence of the probe on the plasma due to its physical presence makes it unattractive for processes in industrial applications. As an improvement the planar design of the MRP (pMRP) was introduced, which combines the advantages of the spherical MRP with the possibility to be integrated into the chamber wall of a plasma reactor. To measure the electron temperature with the pMRP, a kinetic model of the probe-plasma system is necessary. In this work such a kinetic model based on a functional analytic description will be presented. [Preview Abstract] |
Tuesday, November 7, 2017 8:45AM - 9:00AM |
DT2.00004: Abstract Withdrawn
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Tuesday, November 7, 2017 9:00AM - 9:15AM |
DT2.00005: Measurement of Langmuir probe sheath using dusty plasma T. E. Sheridan The radius of the sheath around a thin cylindrical Langmuir probe is measured using dust. The probe tip is oriented perpendicularly to the horizontal, powered electrode in an rf discharge. The current-voltage characteristic of the probe is measured without dust and then with dust. The negatively-charged dust particles are repelled from the probe tip when the probe bias is below the plasma potential, creating a dust-free circular region around the probe tip. We observe a slight decrease in plasma density with dust which is consistent with electron depletion. The probe sheath radius, which we assume is the radius of the dust free region, decreases roughly like the square root of the probe bias. Plasma parameters measured using the Langmuir probe will be compared with measurements using two free-floating dust particles. [Preview Abstract] |
Tuesday, November 7, 2017 9:15AM - 9:30AM |
DT2.00006: Plasma Density Perturbation by Microwave and Magnetic Probes Valery Godyak, Natalia Sternberg Magnetic probes (B-dot, or BDP) have been used over decades for measurement of rf electric field and plasma current. Recently, a variety of microwave probes (MWPs) has been proposed for plasma density measurement. In both cases, insertion of B-dot or microwave probes causes unaccounted plasma disturbance around the probe. Recent analyses$^{\mathrm{\thinspace }}$of MWP probes has shown that they are based on too simplified and unrealistic assumptions about plasma uniformity, sheath capacitance evaluation, cold plasma permittivity, and a Maxwellian EEDF. The assumption of plasma uniformity around the probe is the most serious and common drawback of all MWP and the majority of BDP techniques. Plasma perturbation by a probe has the same localization area as that of MWP and BDP sampling area. This may result in essential difference between measured plasma parameters and those in absence the probe. In this presentation, we give an analysis of plasma perturbations by a spherical probe for arbitrary collisionality. The results were obtained by solving numerically a set of fluid equations for neutral plasma with cold ions, taking into account ion inertia and nonlinear ion friction force. In addition, an analytical solution was found for the collisionless case. The calculation showed a significant plasma density depletion around the probe growing with gas pressure. The depletion of plasma density should underestimate plasma density values inferred from MWP measurement, and dramatically distort rf field and current within BDP. The last is demonstrated for rf field and current distributions in inductive discharge at low gas pressure.. [Preview Abstract] |
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