The structure of a collisionless scrape-off-layer (SOL) plasma in tokamak
reactors is studied in order to define the electron distribution function and the
corresponding sheath potential between the divertor plate and the edge plasma. The
collisionless model is shown to be valid during the thermal phase of plasma
disruption, as well as during the newly desired low-recycling normal phase of operation
with low-density, high-temperature, edge plasma conditions. An analytical solution
is developed by solving the Fokker–Planck equation for electron distribution
and balance in the SOL. The solution is in good agreement with numerical studies
using Monte Carlo methods. The analytical solutions provide insight into the role
of different physical and geometrical processes in a collisionless SOL during
disruptions and during the enhanced phase of normal operation over a wide range of
parameters.
On the role of finite grid extent in SOLPS-ITER edge plasma simulations for JET H-mode discharges with metallic wall
