Annual report 2003
2003 marks the successful demonstration of all power systems funded under the H-1NF Major National Facility upgrade. High power (~200,000 Watt) radio frequency and microwave heating systems provide independent means of heating ions and electrons, and the greatly increased magnetic field strength improves confinement at much higher temperatures, in excess of 2 Million K. An array of programmable Logic Controllers provide simple, safe, largely automated operation of H-1, and cryopump enhancements provide increased plasma purity, and improved turnaround time for attachment of collaborator’s experiments and diagnostics. The computer controlled precision magnet power supplies (12,000,000 Watts) allow precise adjustment of the complex magnetic geometry, and with large operational range of magnetic fields (>20:1), gases, and the variety of heating systems, this makes H-1NF the most flexible plasma machine in the world.
Exploration of the huge parameter space is well underway; the first objective is an understanding of the role of rational rotational transforms, aided by automated scans and data mining software. The facility has already provided important experimental data for turbulence studies, in particular the first experimental evidence for zonal flows in plasma. The enhanced flexibility now available, and several innovative diagnostics are being exploited to advance this work.
Studies of the plasma turbulence in the heliac by Dr Michael Shats and his colleagues demonstrated the role of zonal flows and self-organisation in regulating the outward transport of particles and achieving enhanced confinement regimes. This physics is essential to achieving efficient confinement of fusion plasmas, but is also a universal phenomenon in complex dynamical systems, such fluid flows and Earth and planetary atmospheric physics, and is a rapidly developing research area worldwide. The heliac has been shown to be a uniquely effective experimental environment for precise studies of these phenomena. The heliac is also being used to develop experimental techniques that can be applied on large-scale international fusion experiments.
Dr John Howard and his colleagues have developed a series of instruments called MOSS (modulated solid state spectrometers) which are novel imaging spectrometers that use electro-optic technology and advanced signal processing to determine temperatures and flows in radiating media such as plasmas. Basic experiments on the H-1 heliac have developed techniques which have been applied on instruments in use on fusion plasma experiments in Germany (the Wendelstein VIIAS and WEGA experiments at the Max-Planck Institute) , Italy (the RFX experiment), and the USA (Alcator C-MOD). Infrared MOSS instruments for use in defence applications and in-situ monitoring of flowing steel production have also been developed with support from DSTO and the ACT government.
The magnetic configuration of the heliac can be varied extremely precisely and rapidly, which permits the study of spatial resonances on the magnetic configuration and confinement. Experiments carried out by Dr Boyd Blackwell, Professor Jeffrey Harris and their colleagues demonstrated the sensitivity of confinement and fluctuations to these resonance effects, and a related collaborative experiment on the large D3D tokamak facility in the USA demonstrated the use of spatially-resonant magnetic fields to control the stability of the plasma edge to sudden pulses of heat and particle flux which present control problems for fusion reactors.