Donald A. Fisher

Monte Carlo simulation of ion transport through rf glow‐discharge sheaths

The transport of ions through rf glow‐discharge sheaths was simulated with a Monte Carlo method to determine the distributions of ion‐bombardment energy and angle of impact. Several sheath parameters were varied and their effects examined: (1) the type of ion‐molecule scattering (hard sphere, potential field interaction, charge exchange), (2) the ratio of ion and neutral masses, (3) the ratio of the sheath width to collision mean free path, (4) spatially uniform, spatially linear, and time‐dependent (rf) electric fields in the sheath, and (5) the frequency of an rf component in the sheath. The results of the Monte Carlo simulations indicate that the type of elastic scattering (hard sphere or soft sphere) does not significantly change either the impact angle distributions or the scaled ion‐bombardment energy distributions. Charge‐exchange scattering produces a much greater ion‐bombardment directionality and a different shape of the ion‐bombardment energy distribution. The fully developed distributions depe...

The production and release to the atmosphere of chlorodifluoromethane (HCFC 22)

Abstract The results of an audited production and use survey for chlorodifluoromethane (HCFC 22) for the years 1980–1991 are reported. Annual production figures for 1970–1979 have also been collected. The time delays for release to the atmosphere for the various uses of this commercial gas are estimated in order to calculate annual emissions. Calculated atmospheric concentrations and trends are compared with available measurements. Uncertainties in calculated parameters are examined relative to assumptions made in the analysis.

The production and release to the atmosphere of CFCs 113, 114 and 115

Abstract The results of an audited survey of production and use categories for three fully halogenated chlorofluorocarbons (CFCs 113, 114 and 115) are presented covering worldwide production for the years 1980–1989. Estimates of service time delays for varied uses are estimated in order to calculate annual emissions. Calculated atmospheric concentrations and trends are compared with available measurements.

Uncertainties in the calculation of atmospheric releases of chlorofluorocarbons

Production and sales data for chlorofluorocarbons (CFCs) 11, 12, 113, 114, and 115 as well as for hydrochlorofluorocarbon (HCFC) 22 are available through 1991 from producer surveys. Global atmospheric emissions are estimated from these production data using estimates of the time pattern of release following production as well as estimates for nonreported production; each of these estimates has an associated level of uncertainty. This paper describes the uncertainties associated with emission estimates based on the industrial surveys and the associated uncertainties in lifetimes derived from analysis of the observed tropospheric trends of the key CFCs. For CFC 11 this analysis shows that the greatest uncertainty is associated with the release pattern for closed cell foam blowing agents, whereas for CFC 12 the greatest uncertainty involves estimates of nonreported production and use of material in that portion of the world not surveyed.