In this paper we present a comprehensive account of our results on streamer propagation in dielectric fluids in point-plane geometries. Propagation velocities for both positive and negative streamers have been determined as a function of the following parameters: temperature, pressure, density, viscosity, composition, and conductivity. Effects of voltage and interelectrode spacing were examined. Current and light emission during streamer growth were measured. The relation between shock wave and streamer velocities was investigated. Small concentrations of low-ionization potential additives markedly accelerated the positive streamers, while electron scavengers accelerated the negative streamers. Mechanisms to account for these observations are discussed.
A functional description of the lifetimes of the ion pairs produced in the radiolysis of pure hydrocarbons is derived from the concentration dependence observed for ion scavenging. A number of consequences which follow from this description are explored. In particular it is shown that in the absence of scavenger the decay of the geminate ions must be very closely described by F(t) = eλterfc(λt)1/2, where λ is a constant and F(t) is the fraction of ions present at time t. Appropriate descriptions for the growth and decay of secondary ions are given, and the results are applied to real systems of finite pulses. Comparison is made between the predictions given here for the time dependence of the population of secondary negative ions and the experimental observations of Thomas and co-workers on the decay of diphenylide negative ion in pulse irradiated cyclohexane solutions of diphenyl. From this comparison it is concluded that the rate constant for electron scavenging by the diphenyl is ∼ 3 × 1011M−1·sec−1 and that the preponderant fraction of ion recombination occurs in the time region of 10−11–10−9 sec.
Articles you may be interested inOn the solvation of the trapped electron in γirradiated deuterated ethanol glass at 4 K Electron scavenging in liquid methanol and ethanol has been examined as a function of 14CHaBr and SF& concentration in the region from 10-5 to 0.3 M. The empirical scavenging model previously proposed for hydrocarbons can be successfully extended to alcohols if a competitive first-order reaction of the s?lvated free electron is included. Solvated free-electron and geminate-electron yields have been determmed to be 1.05 and 3.1. Analysis of the data from competitive experiments leads to an estimation of ~he absolute rate constants for reaction of solvated electrons with CHaBr, CHaC!, SF&, N.D, and acetone m methanol and ethanol and to an estimation of the half-life of the solvated free electrons in both solvents. The present results in ethanol can be correlated with the observations of Thomas and Bensasson on the nanosecond decay of solvated electrons in terms of an ion-pair lifetime distribution function similar to that applicable to hydrocarbon radiolysis.
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