This thesis describes the numerical modelling of H-mode plasmas on the Joint European
Torus (JET), both during and between edge localised modes (ELMs). The multi-fluid code
EDGE2D-EIRENE has been benchmarked against experimental data from the inter-ELM
phase of an ITER-relevant JET plasma. Despite matching all other reliable experimental
measurements to within a factor ∼ 1.5, the simulated radiation was located primarily at
the targets, whereas the experimental radiation was located primarily at the X-point. This
discrepancy occurred because the majority of radiating carbon ions in the simulation were
located near the targets. In addition, the inner target Dα measurement was underestimated
in the simulation by a factor of 9. A wide parameter scan did not change these two discrepancies.
The inclusion of a thermoelectric parallel current in the simulations was found to
be consistent with experimental measurements and to give more realistic degrees of in/out
power asymmetry. A fuelling scan was carried out from the benchmarked simulation and
compared to experiment. For similar increases in upstream density, the simulated and experimental
outer target profiles were seen to agree well. This lead to an experimentally
verified scaling of [Equation appears here. To view, please open pdf attachment] for the maximum parallel energy flux density
at the outer target as a function of the electron separatrix density at the outer mid-plane.
Preliminary simulations with nitrogen seeding are also discussed.
The ELM transport phase has also been modelled. By making a simple modification to
the analytic ion free streaming equations (Fundamenski et al. 2006 PPCF, 48:109-156), the
equations are shown to match the impulse responses for target particle and energy fluxes, as
calculated by a 1d kinetic code, to a high degree of accuracy. The linearity of the force-free
Vlasov equation means that a distributed ELM source in time and space can be modelled by
convolving the impulse responses with the ELM source function. Although this introduced some error (due to the fact that, in reality, the potential evolves in time for a distributed
ELM source), the agreement with even a complex 1d3v particle-in-cell code was remarkably
good. A new code is presented that tracks portions of the ELM distribution function in
three-dimensional space as they free stream to the vessel walls. The code is simple and fast
and is shown to reproduce similar scalings for the maximum energy density as were found
in experiment. It also reproduced an experimentally observed profile for the energy density
at the outer target, and encouragingly the agreement was seen to improve when a more
physically realistic distribution for the ELM influx was used in the poloidal direction. The
simulated rise and fall times were too short compared to experiment when an impulse ELM
influx was used and reasons for this discrepancy are discussed. Also demonstrated is the
ability of the code to model the effect of stochasticity of filament size on the surface energy
flux density at the target.