  A 3D tomographic reconstruction technique is described for inversion of a set
of limited-angle high-resolution 2D visible light emission projections
(extended in the vertical and toroidal directions) of global MHD eigenmodes in
the H-1NF heliac. This paper deals with some of the features and challenges
that arise in the application of tomographic imaging systems to toroidal
devices, especially limited viewing access and the strong shaping of optimised
stellarator/heliotron configurations. The fluctuations are represented as a
finite sum of Fourier modes characterised by toroidal and poloidal mode numbers
having fixed amplitude and phase in a set of nested cylindrical flux volumes in
Boozer space. The complex amplitude is calculated using iterative tomographic
inversion techniques such as ART, SIRT and standard linear least-squares
methods. The tomography is applied to synchronous camera images of singly
charged carbon impurity ion emission at 514nm obtained at three discrete
poloidal viewing orientations. It is shown that the 2D amplitude and phase
projections provide high quality reconstructions of the radial structure of the
fluctuations that are compact in Boozer space and allow clear determination of
the poloidal mode number as well as some degree of toroidal mode number
differentiation.
