In this paper, two simplified models of edge localized mode (ELM) power
exhaust are developed, one based on the kinetic and the other on the fluid
treatment of parallel losses. These models are found to capture many (though
not all) of the salient features of kinetic simulations at substantiasl savings in
both cost and complexity (CPU time in seconds versus days), making them
ideal as real time interpretive tools or as modules in non-linear MHD, transport
and/or turbulence codes. The kinetic model offers analytic expressions for the
ion and electron powers deposited on the divertor, parametrized in terms of
transient sheath energy transmission coefficients γi and γe, in good agreement
with particle-in-cell simulations. The fluid model successfully reproducesELM
filament densities and electron energies measured at the outer poloidal limiter
on JET, as well as recent measurements ofELMfilament ion energies in the JET
far-scrape-off layer (SOL). Taking confidence from this favourable comparison,
the same model is then used to predict ion impact energies due to the incidence
of Type-I ELM filaments on the ITER limiter. Although the models are applied
here exclusively to ELMs, they have a potential application to other tokamak
transients, such as intermittent SOL bursts and the disruption thermal quench. |