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Plasma Physics Research Institute [PPRI]
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PLASMA PHYSICS RESEARCH INSTITUTE
Director: Professor M A Hellberg

Members: Professor M M Michaelis, Professor J D Hey and Dr H P Krumm.
Honorary Senior Research Fellow: Professor R Bharuthram (MLSultan).
Honorary Research Fellows: Professor S Baboolal (UDW) and Dr C C Chu.
Collaborators: Professors F Verheest (University of Gent, Belgium),P K Shukla (Ruhr-Universität Bochum, Germany), Drs N F Cramer (University of Sydney, Australia), Ph. Mertens (Forschungszentrum Jülich, Germany), R L Mace and S R Pillay (UDW), and A A L Jarvis (Electrical and Electronic Engineering, UND).
Research Students: E M McKenzie, R Moorgawa, A Conti, C Mahlase.
Technical Support: W J de Beer, D Dixon, L Kolb, J J Coetzer, R Piasecki


The Plasma Physics Research Institute comprises several groups with diverse interest in the general field. These groups conduct experimental and theoretical research into plasma wave propagation and instabilities, plasma excitations and atomic spectroscopy, laser physics and also technological applications, such as the development of hot-gas lenses and plasma processing surface hardening techniques. It collaborates with colleagues at the University of Durban-Westville and the M L Sultan, and has wide-ranging international linkages.

1. Plasma Theory (Hellberg, Bharuthram, Mace, Baboolal)
Group Leader: Professor M A Hellberg.

These studies, which include a collaboration with the University of Durban-Westville and the ML Sultan Technikon, as well as international collaborators in Ghent (Belgium), Bochum (Germany), and Sydney (Australia) are related to two general areas, viz. linear waves in multi-species and non-Maxwellian plasmas, and non-linear electrostatic structures such as solitons and double layers. Although the emphasis is on basic plasma studies, there are important areas of application of this work in, for instance, space physics. This work was supported by the NRF, the Flanders-South African Collaboration Project, and the University Research Fund. The research was published in peer-reviewed journals and presented at international conferences in Iowa City (USA), Potsdam (Germany) and Faro (Portugal).

Projects completed this year or under active study include:
(i) a study of electrostatic modes in a self-gravitating dusty plasma with a distribution of dust masses and charges;
(ii) a study of a dust-modified magnetosonic instability driven by dust streaming relative to a plasma;
(iii) the development of a new plasma dispersion function for electrostatic waves in magnetized plasmas with anisotropic power-law velocity distributions; and its application to ion-acoustic and plasma waves, as well as to investigate the effect of an excess of superthermal particles on the ion wake field in the formation of dusty plasma crystals;
(iv) a study of a resistive dust-ion hybrid drift instability, with possible space physical applications;
(v) a theory of oblique electron-acoustic solitons in a magnetized plasma, with applications to satellite observations in the auroral zone;
(vi) and, arising from that, a unified study of oblique solitons in various multi-species magnetized plasmas;
(vii) scattering of electromagnetic waves by electron-acoustic waves in a plasma with two electron temperatures.


2. Plasma Spectroscopy and Atomic Processes in Fusion Plasmas (Hey, Chu, in collaboration with members of the Institut für Plasmaphysik, Forschungszentrum Jülich, in Germany).
Group leader: Professor J. D. Hey.

One of the two major research projects undertaken in 2001 was related to the spectra of two of the most important impurity elements in fusion plasmas: carbon and oxygen. Spectra in the visible from multiplet 1 of C2+ and O+ ions were recorded by high-resolution Zeeman spectroscopy at the TEXTOR tokamak in Germany, and analysed to yield the respective ion temperatures, and the relative particle concentrations in the relevant excited states. It was shown that both physical and chemical sputtering (in the case of carbon), and electron impact-induced molecular dissociation (in the case of oxygen) play important roles in modelling the observed temperatures of the ion species. The transition between the regimes of physical and chemical sputtering was observed in the carbon ion spectra, as a function of mean electron concentration and local electron temperature. The comparatively high temperatures attained by O+ ions was explained by the rapid increase in dipole polarisability of neutral oxygen as a function of principal quantum number, since the production of these atoms by molecular dissociation takes place via highly excited Rydberg states, by electron impact. This work was presented by Prof. J. D. Hey at the 28th European Physical Society Conference on Controlled Fusion and Plasma Physics, held in Funchal de Madeira (Portugal) in June 2001. The second project was initiated in November 2001 by Dr. C. C. Chu on a visit to Germany, when a new collaborative programme was arranged for the analysis of hydrogen spectra emitted by tokamak plasmas. This work entails the use of codes for the Zeeman (Paschen-Back) effect in high magnetic fields developed in Durban, and will provide access to workers at the University of Natal to some of the best atomic spectra yet obtained from fusion devices. The details of the method have been provided in a series of technical reports from this Institute, written in the years 1996-1998, and also included in various publications in recent years.


3. Laser-based Studies (Michaelis, Chu, Moorgawa, Jarvis, Conti, McKenzie, Mahlase)
Group Leader: Professor M M Michaelis.

The laser group is engaged in research into various applications of lasers, including: atmospheric LIDAR; gas lenses, diode laser modulation; laser space propulsion and peripheral systems such as tensional vacuum vessels. The group is supported by the Franco-South African NRF co-operation (LIDAR), by SDI Pty Ltd and by NRF-THRIP (Diode lasers) and by the NRF-National Laser Centre (NLC), (Laser Propulsion). The group maintains close ties with the laser company SDI, with the NLC (Pelindaba) and with the CSIR. A number of post-graduate students from both inside and outside South Africa are involved in research projects. Gas lenses, as their name implies, are lenses whose optical characteristics are determined by the gradient index (GRIN) behaviour of gases. They are able to handle the enormous power (up to 1015W) of modern lasers. Lenses made from solid materials, such as glass, have reached their power handling limits for many applications.

The LIDAR (the optical equivalent of a radar) system, operated in conjunction with the French CNRS and the Laboratoire de Physique de L’Atmosphere at Reunion Island, investigates wave and aerosol behaviour in the atmosphere above Durban, which is of interest to geographers and ecologists.

Successful experiments in laser propulsion have been carried out at Pelindaba and in Durban. A new project using diode lasers for spectroscopic analysis of pollutants is being developed together with Mr Jarvis at the School of Electronic Engineering, and Dr Chu.


Visitors to the Institute during 2001

Professor Frank Verheest (University of Gent, Belgium).
Mr Michael Hoarau (Département de Physique, Université de la Réunion).
Dr David Boutchiama, (Département de Physique, Université de la Réunion).
Dr H Bencherif (Département de Physique, Université de la Réunion).
Mr J Porteneuve (CNRS, France)
Mr S Brezinsek (Institut für Plasmaphysik, Forschungszentrum Jülich in Germany).
Mr J Leclair de Belleuve (Département de Physique, Université de la Réunion).


Special interest:

Professor M A Hellberg:
(i) Member, National Laser Centre Advisory Board.
(ii) Council Member. SA Institute of Physics (Past President)
(iii) Appointed Member of International Advisory Committee, International Conference on Plasma Physics, Sydney, Australia.
(iv) Appointed Member of Scientific Programme Committee, World Space Environment Forum, Adelaide, Australia.

Professor M M Michaelis:
(i) Gave the opening address/talk at the SPIE High Power Laser Ablation conference in New Mexico, USA.

 
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