Collisional Radiative Models for Hydrogen Atoms and for Hydrogen Molecules In a Tokamak Plasma
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Date
1992-06
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Addis Ababa University
Abstract
A collisional radiative model is applied to study the ionization,
recombination, and energy loss rates of an optically thin hydrogen plasma in a
Tokamak thermonuclear fusion reactor. The effective ionization and
recombination coefficients are found to be increasing functions of electron
density, the increase being bigger when the temprature is low. The rate of
radiative energy loss is significant only in low density plasmas; and the estimate
that has been used by most plasma modelers is pretty big that it cannot be applied
for dense plasmas.
Edge plasma cooling due to the interaction of recycling neutral particles
near diverter targets with the scrape off layer is an important effect to reduce
the heat load on Tokamak vessel components. The relevant atomic data for
hydrogenic atoms are well established, whereas the data base for molecules is
less complete. Collisional radiative processes are considered to study the effects
of hydrogen molecules in the edge plasma boundary. Effective dissociation and
dissociative ionization rate coefficients are calculated. Rate coefficients for the
production of neutral atoms from hydrogen molecules are also evaluated. Finally
the rate of electron energy loss per dissociation of molecules into atoms and/or
ions is calculated. The rate of this energy loss is significant and the dissociation
of the molecules may account for the missing heating power in the divertor
region
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Collisional Radiative Models