Swarm parameters in SF<sub>6</sub>and CO<sub>2</sub>gas mixtures

Xiao, Di; Li, X G; Xu, Xin

doi:10.1088/0022-3727/34/24/102

Cited by 24 publications

(26 citation statements)

References 5 publications

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“…In the absence of any other R net measurements in SF 6 , to our knowledge 16 , figure 4 only displays the rate coefficient of Aschwanden [66], reported directly in that thesis, and the rate coefficients of de Urquijo et al [103] and Xiao et al [98,104], transformed through the relationship (30), with good agreement observed between all.…”

Section: Sfmentioning

confidence: 93%

Foundations and interpretations of the pulsed-Townsend experiment

Casey

Stokes

Cocks

et al. 2021

Plasma Sources Sci. Technol.

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The pulsed-Townsend (PT) experiment is a well known swarm technique used to measure transport properties from a current in an external circuit, the analysis of which is based on the governing equation of continuity. In this paper, the Brambring representation (1964 Z. Phys. 179 532) of the equation of continuity often used to analyse the PT experiment, is shown to be fundamentally flawed when non-conservative processes are operative. The Brambring representation of the continuity equation is not derivable from Boltzmann's equation and consequently transport properties defined within the framework are not clearly representable in terms of the phase-space distribution function. We present a re-analysis of the PT experiment in terms of the standard diffusion equation which has firm kinetic theory foundations, furnishing an expression for the current measured by the PT experiment in terms of the universal bulk transport coefficients (net ionisation rate, bulk drift velocity and bulk longitudinal diffusion coefficient). Furthermore, a relationship between the transport properties previously extracted from the PT experiment using the Brambring representation, and the universal bulk transport coefficients is presented. The validity of the relationship is tested for two gases Ar and SF 6 , highlighting also estimates of the differences.

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Section: Sfmentioning

confidence: 93%

Foundations and interpretations of the pulsed-Townsend experiment

Casey

Stokes

Cocks

et al. 2021

Plasma Sources Sci. Technol.

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“…The swarm data of C 3 F 7 CN have also shown that the effective ionisation coefficient increases much slower with increasing electric field than that of SF 6 . The slopes of C 3 F 7 CN and SF 6 gases are 3.53 � 10 −24 and 3.04 � 10 −23 m 2 /Td, respectively [24,25]. This means that less energy is required for to ionise C 3 F 7 CN than SF 6 .…”

Section: Surface Roughness Measurementsmentioning

confidence: 98%

Gas decomposition and electrode degradation characteristics of a 20% C ₃ F ₇ CN and 80% CO ₂ gas mixture for high voltage accelerators

et al. 2021

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Sulphur hexafluoride (SF 6 ) is a potent greenhouse gas used in high voltage accelerators. As a promising alternative to SF 6 , the C 3 F 7 CN/CO 2 gas mixture and its by-products are of great interest to ensure the safe operation of accelerators that will adopt any SF 6 -free solution. This work experimentally examines the electrical ageing characteristics of a 20% C 3 F 7 CN/80% CO 2 gas mixture tested using spark gaps under a pressure of 7.2 bar (abs.). Gas samples were collected after 1000 DC breakdowns and analysed using gas chromatography mass spectrometry (GC-MS) with an estimated toxicity value of 54,459 ppm v , which indicates the aged mixture to be non-toxic. Subsequent investigation was conducted on the gas-solid interface after 500 breakdowns for both SF 6 and the 20% C 3 F 7 CN/80% CO 2 gas mixture. Aged electrodes were analysed using X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. Electrode surface analysis revealed the formation of metal fluorides on the electrode surface tested using the 20% C 3 F 7 CN/80% CO 2 mixture, whereas metal fluorides and sulphides were detected for electrodes tested with SF 6 . The findings provide a reference on the toxicity and gas-solid interaction of the electrically aged 20% C 3 F 7 CN/80% CO 2 gas mixture for potential retro-fill application in high voltage accelerators.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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“…where σ m is the total momentum cross-section consisting of contributions from all possible collision processes. Several papers [40][41][42] have given the measurement result for μ e N at 300 K. In Fig. A6, μ e N values measured at 300 K are denoted by several symbols such as open circles.…”

Section: Rate Coefficient For Electron Collision Process In Hot Sf 6 Gasmentioning

confidence: 99%

Rate coefficient and collision frequency for electron collision process in hot SF₆ gas under electric field: electrical breakdown property at 300–3000 K

Yokomizu

Murakita

Kojima

et al. 2018

IEEJ Transactions Elec Engng

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Hot SF 6 gas of several thousand kelvins is produced during the current interruption process in a gas circuit breaker. If the hot gas is subjected to an electric field, electrical breakdown of the hot gas can occur as a consequence of the ionization and attachment processes by electron impact. The probability of occurrence of the process is stated in terms of a rate coefficient. First, this paper describes the rate coefficients of the electron impact processes in the hot SF 6 gas subjected to an electric field. The rate coefficients in SF 6 gas in the range 300-3000 K at 0.6 MPa are evaluated for 21 processes such as SF 4 + e → SF 4 + + 2e and F 2 + e → (F 2 − ) * → F − + F. Second, using these rate coefficients we obtain the collision frequencies of the 21 processes and find out the predominant processes in the hot SF 6 gas. Finally, 26 continuity equations with the rate coefficients are expressed in terms of the particle number densities. Using numerical solutions of the continuity equations, we derive the critical electric field of SF 6 gas for different temperatures. Furthermore, comparative discussions are presented on the critical electric field strength and the collision cross-sections shown in other published papers. The present study is considered to provide the rate coefficients and the critical electric field strengths with higher accuracy.

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Swarm parameters in SF₆and CO₂gas mixtures

Cited by 24 publications

References 5 publications

Foundations and interpretations of the pulsed-Townsend experiment

Foundations and interpretations of the pulsed-Townsend experiment

Gas decomposition and electrode degradation characteristics of a 20% C ₃ F ₇ CN and 80% CO ₂ gas mixture for high voltage accelerators

Rate coefficient and collision frequency for electron collision process in hot SF₆ gas under electric field: electrical breakdown property at 300–3000 K

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Swarm parameters in SF6and CO2gas mixtures

Cited by 24 publications

References 5 publications

Foundations and interpretations of the pulsed-Townsend experiment

Foundations and interpretations of the pulsed-Townsend experiment

Gas decomposition and electrode degradation characteristics of a 20% C 3 F 7 CN and 80% CO 2 gas mixture for high voltage accelerators

Rate coefficient and collision frequency for electron collision process in hot SF6 gas under electric field: electrical breakdown property at 300–3000 K

Contact Info

Product

Resources

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Swarm parameters in SF₆and CO₂gas mixtures

Gas decomposition and electrode degradation characteristics of a 20% C ₃ F ₇ CN and 80% CO ₂ gas mixture for high voltage accelerators

Rate coefficient and collision frequency for electron collision process in hot SF₆ gas under electric field: electrical breakdown property at 300–3000 K