Electron neutral collision frequency measurement with the hairpin resonator probe

Peterson, David J.; Kraus, P.; Chua, Thai Cheng; Larson, Lynda; Shannon, Steven

doi:10.1088/1361-6595/aa80fa

Cited by 17 publications

(16 citation statements)

References 21 publications

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“…The electron densities under plasma conditions were calculated from the shift in frequency of the resonance peak, using the iterative method described by Piejak et al Corrections for the sheath and for electron collisions were made using the formulas proposed by Sands et al and the step-front sheath model from ref to estimate the sheath width. The electron-neutral collision frequency was calculated with the method proposed by Peterson et al The collision frequencies derived from the fitting of the Lorentzian profile of the resonance peak are in fair agreement with tabulated values for different gases given in ref .…”

Section: Methodssupporting

confidence: 69%

Time Evolution of the Dissociation Fraction in rf CO₂ Plasmas: Impact and Nature of Back-Reaction Mechanisms

2020

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The time evolution of the dissociation fraction in a pulsed radio frequency (rf) CO2 discharge is studied by infrared absorption. A large parametric study performed in a closed reactor brings valuable information about both dissociation and recombination processes. The CO2 conversion shows a time evolution initially controlled by electron impact dissociation. For longer plasma-on times, the dissociation fraction reaches a steady-state that corresponds to a balance between dissociation processes and back-reaction mechanisms. The characteristic times of vibrational and rotational excitation of CO and CO2 are measured during a single plasma pulse. The dependence of the CO2 conversion as a function of pulse duration and frequency is then analyzed, showing the influence of the plasma excitation conditions on the back-reaction mechanisms. The study of CO2–O2 and CO–O2 gas mixtures gives further insight into the impact of the oxygen content in these mechanisms. The global back-reaction rate observed in these experiments is compared with calculated values from rate coefficients available in the literature. The experimental results and preliminary calculations reveal a key role of molecular oxygen and of the metastable electronically excited state CO(a 3Π r ) in the back-reaction. Competing processes involving vibrational excited CO are not dominant in our discharge conditions but may become relevant at slightly higher vibrational temperatures.

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Section: Methodssupporting

confidence: 69%

Time Evolution of the Dissociation Fraction in rf CO₂ Plasmas: Impact and Nature of Back-Reaction Mechanisms

2020

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“…No matter what dimensions of the hairpins we choose, our Q values are below 100 when the resonant frequencies are higher than 8.0GHz. The hairpins reported by Sands et al [6] and Peterson et al [5] have Q > 100, but their resonant frequencies fall in the range of 2.0 -3.1GHz. The compromise of accuracy is unavoidable when pursuing higher measurable frequencies.…”

Section: Fig 5 Comparison Of Hairpins With Dimensions Given Inmentioning

confidence: 92%

“…The hairpin is sensitive to changes of multiple parameters of plasma. For example, due to its behavior at higher pressures, it can be used to measure the collision frequency in moderate pressure plasma (1 -10Torr) [5]. When it measures the electron density in the higher pressure (>1 Torr), a collisional correction is put forward [6].…”

Section: Introductionmentioning

confidence: 99%

Electron density measurement using a partially covered hairpin resonator in an inductively coupled plasma

Fan

Wug²,

Han³

et al. 2020

Review of Scientific Instruments

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Hairpin probes measure electron density in plasmas where other techniques are unsuitable. Previous hairpins were constructed as a quarter-wave resonant structure typically made from a folded piece of wire. The present work conducts the hairpin measurement in high electron density, up to approximately 10 12 / cm 3 , corresponding to a plasma frequency of about 9 GHz. A series of four probes is described, together with an easily reproducible implementation of the associated microwave electronics using commercial off the shelf components that are inexpensive compared to the network analyzer that is typically required. Measuring higher densities requires increasing the resonant frequency, but we were unable to accurately fabricate the required quarter wavelength structure on the scale of 4 mm. Toward this end we explore operating a larger quarter-wavelength structure at its 3d harmonic (3/4 resonator). Correction coefficients are described for both the plasma sheath effect and the wire coating. Measurements are taken in Argon at pressures below 20 mTorr. Results are compared with Langmuir probe measurements.

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“…where e¢ and e represent the real and imaginary part of the dielectric constant, respectively. 28) So, the Q-factor of plasma, Q plasma is expected to decrease with increasing pressure and has less than w n / . However, precise calculation of the Q plasma is difficult because it is affected by additional dissipation through collisionless heating and poor antenna coupling.…”

Section: Plasma System As a Loadmentioning

confidence: 99%

Phase-transition time of a commercial magnetron driving a surface-wave plasma load

Kim¹,

Cha²,

Shon³

et al. 2023

Jpn. J. Appl. Phys.

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Surface-wave plasma which generates a specific wave mode between the plasma and a dielectric window by microwave is superior to RF plasmas in producing relatively higher electron density at low temperature. To challenge the uniformity issue of the microwave plasma whose wavelength is shorter than the size of the industrial system, rotating field systems by imparting a phase difference of microwaves from multiple inputs over time are attracting attention. The authors investigate the feasibility of a phase-locked-loop (PLL) injected magnetron (MGT) as a highly efficient microwave source to modulate the phase difference of high-power microwaves fast and precisely. The phase-transition time of the MGT with a plasma load is estimated to be below 45 ns by theoretical analysis and experimental measurement. The results show that the phase-modulation frequency of microwaves with the PLL-injected MGT is capable of reaching up to 10 MHz.

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Electron neutral collision frequency measurement with the hairpin resonator probe

Cited by 17 publications

References 21 publications

Time Evolution of the Dissociation Fraction in rf CO₂ Plasmas: Impact and Nature of Back-Reaction Mechanisms

Time Evolution of the Dissociation Fraction in rf CO₂ Plasmas: Impact and Nature of Back-Reaction Mechanisms

Electron density measurement using a partially covered hairpin resonator in an inductively coupled plasma

Phase-transition time of a commercial magnetron driving a surface-wave plasma load

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Electron neutral collision frequency measurement with the hairpin resonator probe

Cited by 17 publications

References 21 publications

Time Evolution of the Dissociation Fraction in rf CO2 Plasmas: Impact and Nature of Back-Reaction Mechanisms

Time Evolution of the Dissociation Fraction in rf CO2 Plasmas: Impact and Nature of Back-Reaction Mechanisms

Electron density measurement using a partially covered hairpin resonator in an inductively coupled plasma

Phase-transition time of a commercial magnetron driving a surface-wave plasma load

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Product

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Time Evolution of the Dissociation Fraction in rf CO₂ Plasmas: Impact and Nature of Back-Reaction Mechanisms

Time Evolution of the Dissociation Fraction in rf CO₂ Plasmas: Impact and Nature of Back-Reaction Mechanisms