Measurement of Townsend's Ionization Coefficients and Attachment Coefficients in Oxygen

Prasad, Awadhesh; Craggs, J D

doi:10.1088/0370-1328/77/2/322

Cited by 59 publications

(34 citation statements)

References 15 publications

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“…at E/p""'" 10. Prasad and Craggs (1961) have shown that for a Druyvesteyn distribution of velocities the data obtained in swarm-type experiments by H.C.B., C.P.B., Doehring, and Prasad and Craggs were in better agreement with the data from the beam experiments of Craggs, Thorburn, and Tozer (1957) and of Buchel'nikova (1959) than were the results of other swarm experiments.…”

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confidence: 57%

The Behaviour of Free and Attached Electrons in Oxygen

Rees¹

1965

Aust. J. Phys.

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SummaryThe behaviour in oxygen of swarms of electrons having mean energies of up to 2 eV has been studied. Confirmation of the occurrence in oxygen of a three-body attachment process has been obtained, and the attachment coefficient has been measured for 0·4 < E/p < 6 Vcm-1 torr-1. Values of the Townsend energy fa()tor k1 have also been obtained over the same range of values of E/p. It was observed that at least three species of negative ions were formed either directly by the electron attachment processes or through secondary collisions between these primary ions and the gas molecules. The mobilities of the various ion species were determined over the range 0

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confidence: 57%

The Behaviour of Free and Attached Electrons in Oxygen

Rees¹

1965

Aust. J. Phys.

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“…Prasad and Craggs 1961;Rees 1964;Rees and Jory 1964) have shown discrepancies no greater than might be expected as a result of imprecise knowledge of the appropriate energy distributions, the comparisons for water vapour (Prasad and Craggs 1960) were a notable exception. For this gas, values of ua calculated from swarm experiments exceeded the corresponding values calculated from Buchel'nikova's data by a factor of 5 in some instances.…”

Section: Comparison Of Attachment Data From Beam and Swarm Experimentioning

confidence: 94%

The Diffusion and Attachment of Electrons in Water Vapour

Crompton¹,

Rees²,

Jory³

1965

Aust. J. Phys.

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SummaryThe energy ratio and attachment coefficient for electrons in water vapour have been determined in the range 20 < Elp < 60 V cm-l torr-l. The results for the attachment coefficient are in general agreement with other recent determina· tions, but those for the energy ratio differ significantly from the results of Bailey and Duncanson. The use of these new data, in conjunction with values of the drift velocity determined by Pack, Voshall, and Phelps, is shown to remove the serious discrepancy which previously existed between the results of single-collision and swarm experiments. r. INTRODUCTIONWhen electrons having energies of the order of 5 e V pass through water vapour at a pressure of a few torr, an appreciable fraction of the electrons form negative ions by electron attachment. According to Laidler (1954), Craggs and McDowell (1955), and others, the dominant attachment process for energies up to about lO e V is the following resonance capture process:(1)Laidler states that the water molecule is first raised to a repulsive 2Al or 2A2 state of H 2 0-which at once dissociates into H -(IS) and OH(27T). The appearance potential is of the order of 5·5 e V, and the cross section is a maximum for electrons having energies of about 6·5 eV.The curve showing the variation with electron energy of the rate of production of H -ions from H 2 0 shows a second, smaller peak which has a maximum value at an energy of about 8·5 eV (Mann, Hustrulid, and Tate 1940; Buchel'nikova 1959). For electrons of energy greater than about 7·5 eV, 0-ions may also be produced, the reaction being (2) It is widely believed (see, for example, Cottin 1959) that the H-ions formed as above are rapidly converted to negative hydroxyl ions by the following process:At gas pressures of the order of 1 torr, Branscomb and Smith (1955) and Muschlitz and Bailey (1956) observed that the OH-ions so formed were considerably more abundant than either H -or 0-ions.

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“…10 presents the comparison of the calculated attachment coefficient in pure O 2 with the literature data. [35][36][37][38][39][40][41][42][43][44][45] At relatively low E/N (below 20Td), a deviation between the calculated results and Grünberg's data 35 can be observed, which may be because of the adopted cross section data for the 3-body attachment. However, at relatively high E/N, the calculated data drown in the literature results.…”

Section: B Ionization and Attachment Coefficientsmentioning

confidence: 93%

Study of the synergistic effect in dielectric breakdown property of CO2–O2 mixtures

2017

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Sulfur hexafluoride, SF6, is a common dielectric medium for high-voltage electrical equipment, but because it is a potent greenhouse gas, it is important to find less environmentally harmful alternatives. In this paper we explore the use of CO2 and O2 as one alternative. We studied the synergistic effect in a mixture of CO2 and O2 from both macroscopic and microscopic perspectives. The effect leads to a dielectric strength of the mixture being greater than the linear interpolation of the dielectric strengths of the two isolated gases. We analyzed the critical reduced electric field strength, (E/N)cr, the breakdown gas pressure reduced electric field, E/p, and the breakdown electron temperature, Tb, and their synergistic effect coefficients for various CO2 concentrations and various products of the gas pressure times the gap distance (pd). A gas discharge and breakdown mechanism in a homogenous electric field is known to be controlled by the generation and disappearance of free electrons, which strongly depend on the electron temperature. The results indicate that adding a small amount of O2 to CO2 can effectively improve the value of (E/N)cr and bring a clear synergistic effect. In addition, significantly different variation trends of the synergistic effect in the E/p and Tb of CO2-O2 mixtures at various CO2 concentrations and pd values were also observed.

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Measurement of Townsend's Ionization Coefficients and Attachment Coefficients in Oxygen

Cited by 59 publications

References 15 publications

The Behaviour of Free and Attached Electrons in Oxygen

The Behaviour of Free and Attached Electrons in Oxygen

The Diffusion and Attachment of Electrons in Water Vapour

Study of the synergistic effect in dielectric breakdown property of CO2–O2 mixtures

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