Understanding plasma instabilities in the H-1 heliac

A typical raw image of the plasma as viewed along a major radius between two of the H-1 toroidal field coils

The H-1 heliac exhibits a range of helical global instabilities in hydrogen-helium discharges at 0.5T. An array of diagnostic systems, including multi-axis magnetic probes and the upgraded mm-wave imaging interferometer are being used to characterise their behaviour to allow comparison with 3d models.

A fast gated camera synchronised to the magnetic perturbation signal associated with the instability allows us to freeze-frame the structure at various phases of its oscillation.

By applying Fourier techniques to a sequence of such images obtained at different phases, it is possible to obtain images of the harmonic components of the light emission.

The figure below shows the extracted dc emission (left) as well as the amplitude (centre) and phase (right) of the fundamental component of the oscillation. These images can be tomographically unfolded to deliver information about the radial structure of the instability for comparison with modeling.

Contact

John Howard

(02) 612 53751