Annual report 2004
2004 was a productive year – the group moved into purpose-built laboratories in the new Weigold wing, work began on recasting the business plan to suit the operational phase of the facility, and the automation of H-1 was largely completed. Automation by the use of programmable logic controllers accelerates data-taking, improves the quality of data by extensive logging of measurements, and reduces the manpower required to operate the H-1 facility. As a result over 3,100 plasma pulses were recorded, amounting to 20 Gigabytes of raw data. New systems included a directional gas injection system (DISH) and an electron cyclotron resonance heating (ECRH) incident energy monitor. 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 in the Advanced Imaging and Inverse Methods Group have developed a series of instruments known as coherence imaging spectrometers. These are novel imaging spectrometers that use electro-optic technology and advanced image and signal processing to determine temperatures and flows in radiating media such as plasmas. This year Dr Howard has expanded the development of novel multi-spectral imaging systems with two recent provisional patent applications on instruments suitable for industrial colour pyrometry for temperature and emissivity imaging, and for high-speed high-resolution spectroscopic imaging. Unique `camera´ instruments similar to those successfully employed on the H-1 heliac, and optimized for high-speed plasma Doppler studies have been commissioned under contract to Consorzio RFX Italy, Max Planck Institute for Plasma Physics (Germany) and the Korean Basic Science Institute. Another system is being developed for the University of Sydney with LIEF grant support. The visible emission tomography system based on a 55 channel fibre coupled coherence imaging spectrometer demonstrated its full potential by imaging intensity, ion temperature and flow in an argon plasma, and by reconstructing both normal surfaces and magnetic islands.
Ground-breaking experimental studies of plasma turbulence in the heliac by Dr Michael Shats and his colleagues demonstrated the role of self-organisation, zonal flows and spectral energy transfer in regulating the outward transport of particles and achieving enhanced plasma confinement. 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 both 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 computer controlled precision magnet power supplies (12,000,000 Watts) together with the above-mentioned automation allow precise adjustment of the complex magnetic geometry.
With a large operational range of magnetic fields (>20:1), gases, and the variety of heating systems, H-1NF is the most flexible plasma machine in the world. This facilitates detailed investigation of the effect of spatial resonances on 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.