Abstract:
Effective understanding of gas flow is important to ensure efficient operation of gas neutralizer
systems such as those used at the Joint European Torus (JET), which form part of invaluable
heating systems for nuclear fusion experiments. Computational fluid dynamics modelling of the
neutral gas flow in the JET neutraliser has been undertaken, motivated by the shortfall in neutralisation
efficiency and apparent loss of gas target observed in the JET neutraliser system. This has
presented a challenging modelling endeavour due to the interaction of beam, background plasma
and rarefied neutral gas. Utilising the continuum flow approximation, the Navier-Stokes and
Augmented Burnett equations have been implemented and applied in conjunction with secondorder
slip boundary conditions to form a gas solver accurate within the continuum-transition
regime.
Simulations in the presence of the ionic beam and background neutraliser plasma encountered
during tokamak heating operations have been achieved via the development of a coupled beamplasma-
gas solver. The gas flow governing equations have been supplemented by a series of
source/sink terms for mass/energy that describe the complex web of interactions between the
neutraliser constituents.
The developed solver has been validated against experimental data, both in the absence and
presence of beam. The design of future gas neutraliser systems has also been considered, with
variation of several model and geometry parameters in order to better understand the loss of
neutralisation efficiency and how future systems might be optimised. The neutraliser design for
the forthcoming International Thermonuclear Experimental Reactor (ITER) has also been evaluated.
