Numerical simulations of the transition from the low
confinement (L-) mode to the high confinement (H-) mode in magnetically
confined plasmas - as, e.g., Tokamak devices.
The confinement of plasma particles and energy in
magnetically confined plasmas and thereby the performance of a fusion reactor
is strongly influenced by turbulent transport. This transport is generally
increasing as the input power is ramped up until a threshold value, where the
edge heat flux reaches a critical value. The confinement is then abruptly
improved, and the plasma enters a state of high confinement, the so-called H –
mode, contrasting the low confinement state - the L-mode.
The transition from L- to H-mode is routinely observed
and controlled in fusion experiments for the last three decades, but still
lacks a first principles explanation. It is thus one of the high-priority
topics of fusion research.
The formation of a transport barrier limiting the
transport at the plasma edge, as the transition occurs, is believed to be
connected with the appearance of large scale shear flows. Insight into the L-H
transition dynamics has been gained from simplified models of the predator-prey
type, basically describing the self-regulation of the turbulence by means of
the shear flow that is fed by the turbulence. Recent simulation results using
the four field plasma fluid code, HESEL, have revealed L-H transitions
recovering the transport barrier formation as described by the simplified models.
The HESEL model governs the edge-region dynamics of magnetically
The topic of this project is to apply the HESEL model
to investigate the L-H transition for different heating scenarios, e.g.,
different ratios between electron and ion power input using plasma parameters
from experiments, specifically from selected JET shots. A power built-up is
expected as the system enters H-mode and the system should be studied well
after the transition to observe an eventual power burst and temporary returns
to L-mode confinement. Comparisons with experimental data may also be
Knowledge of numerical solutions of coupled ordinary as well as partial differential equations.Some knowledge of continuum dynamics, plasma physics, and complex dynamics will be beneficial.