Verlag des Forschungszentrums Jülich
JUEL-2872
Maddison, Geoffrey P.; Reiter, Detlev
Recycling source terms for edge plasma fluid models and impact an convergence behaviour of the BRAAMS "B2" code
70 S., 1994
Abstract
Predictive simulations of tokamak edge plasmas require the most
authentic description of neutral particle recycling sources, not merely
the most expedient numerically. Employing a prototypical ITER divertor
arrangement under conditions of high recycling, trial calculations
with the "B2" steady-state edge plasma transport code, plus varying
approximations of recycling, reveal marked sensitivity of both results
and its convergence behaviour to details of sources incorporated. Comprehensive
EIRENE Monte Carlo resolution of recycling is implemented
by full and so-called "short" intermediate cycles between the plasma
fluid and statistical neutral particle models. As generally for coupled
differencing and stochastic procedures, though, overall convergence properties
become more difficult to assess. A pragmatic criterion for the
"B2" /EIRENE code system is proposed to determine its success, proceeding
from a stricter condition previously identified for one particular
analytic approximation of recycling in "B2". Certain procedures are also
inferred potentialiy to improve their convergence further.
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