Abstract
Most divertor impurity modelling gives the result that negligible leakage occurs of impurities produced at the plates, to the confined plasma. This is not, however, found experimentally. A Monte Carlo impurity code has been employed in exploratory studies aimed at identifying possible leakage pathways to the main plasma. It was found that for substantial range of divertor plasma densities and temperatures, the friction force dominated all other forces on the impurities, including the temperature gradient forces which are generally directed away from the plates. Thus, if it was assumed that the deuterium plasma flow was everywhere directed toward the plates, negligible leakage to the confined plasma occurred. The possibility of deuterium flow reversal was also considered where it was assumed that over some radial fraction of the SOL, the deuterium plasma flow was directed away from the plates, starting at a distance from the plates equal to the deuterium average ionization distance. The spatial distribution of impurity (carbon) physically sputtered neutrals was modelled and it was found that a fraction of the impurity neutrals were ionized in the deuterium flow reversal zone. When these impurity particles were then tracked through further ionization, and their parallel and cross-field transport was followed,
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Stangeby, P C
[1]
- Toronto Univ., ON (Canada). Inst. for Aerospace Studies
Citation Formats
Stangeby, P C.
The magnitude and direction of forces on impurities near a diverter plate. An exploratory investigation.
Canada: N. p.,
1990.
Web.
Stangeby, P C.
The magnitude and direction of forces on impurities near a diverter plate. An exploratory investigation.
Canada.
Stangeby, P C.
1990.
"The magnitude and direction of forces on impurities near a diverter plate. An exploratory investigation."
Canada.
@misc{etde_10119964,
title = {The magnitude and direction of forces on impurities near a diverter plate. An exploratory investigation}
author = {Stangeby, P C}
abstractNote = {Most divertor impurity modelling gives the result that negligible leakage occurs of impurities produced at the plates, to the confined plasma. This is not, however, found experimentally. A Monte Carlo impurity code has been employed in exploratory studies aimed at identifying possible leakage pathways to the main plasma. It was found that for substantial range of divertor plasma densities and temperatures, the friction force dominated all other forces on the impurities, including the temperature gradient forces which are generally directed away from the plates. Thus, if it was assumed that the deuterium plasma flow was everywhere directed toward the plates, negligible leakage to the confined plasma occurred. The possibility of deuterium flow reversal was also considered where it was assumed that over some radial fraction of the SOL, the deuterium plasma flow was directed away from the plates, starting at a distance from the plates equal to the deuterium average ionization distance. The spatial distribution of impurity (carbon) physically sputtered neutrals was modelled and it was found that a fraction of the impurity neutrals were ionized in the deuterium flow reversal zone. When these impurity particles were then tracked through further ionization, and their parallel and cross-field transport was followed, a substantial impurity density was found in the confined plasma with Z{sub eff} values of 3 or more. It was thus concluded that flow reversal of the deuterium plasma is a promising possible explanation of the leakage of divertor plate impurities to the confined plasma.}
place = {Canada}
year = {1990}
month = {Jun}
}
title = {The magnitude and direction of forces on impurities near a diverter plate. An exploratory investigation}
author = {Stangeby, P C}
abstractNote = {Most divertor impurity modelling gives the result that negligible leakage occurs of impurities produced at the plates, to the confined plasma. This is not, however, found experimentally. A Monte Carlo impurity code has been employed in exploratory studies aimed at identifying possible leakage pathways to the main plasma. It was found that for substantial range of divertor plasma densities and temperatures, the friction force dominated all other forces on the impurities, including the temperature gradient forces which are generally directed away from the plates. Thus, if it was assumed that the deuterium plasma flow was everywhere directed toward the plates, negligible leakage to the confined plasma occurred. The possibility of deuterium flow reversal was also considered where it was assumed that over some radial fraction of the SOL, the deuterium plasma flow was directed away from the plates, starting at a distance from the plates equal to the deuterium average ionization distance. The spatial distribution of impurity (carbon) physically sputtered neutrals was modelled and it was found that a fraction of the impurity neutrals were ionized in the deuterium flow reversal zone. When these impurity particles were then tracked through further ionization, and their parallel and cross-field transport was followed, a substantial impurity density was found in the confined plasma with Z{sub eff} values of 3 or more. It was thus concluded that flow reversal of the deuterium plasma is a promising possible explanation of the leakage of divertor plate impurities to the confined plasma.}
place = {Canada}
year = {1990}
month = {Jun}
}