In direct current discharges between a cathode and an anode, applying too large an electric field will cause the discharge to break into an arc. In electrodeless rf discharges, however, extremely large electric fields can be applied without arcing.
This phenomenon would be expected to occur preferentially in gases, such as hydrogen, that do not have a large peak in the cross-section. Landau and cyclotron damping in rf discharges. Production of primary electrons by Landau damping has been postulated for helicon discharges, but there has been no prediction or measurement of the number of electrons accelerated in this manner. More recently, cyclotron damping has been proposed as an additional mechanism that can be important in low magnetic fields.
These kinetic absorption mechanisms may be important in low-pressure plasmas used for materials processing. Particle confinement by multidipole magnetic fields.
Theory Low Temperature Plasma Physics by Shi Nguyen Kuok
Previous studies of confinement by such surface fields were concerned with the overall confinement time of the plasma. In etching tools, however, it is the confinement of each velocity class of electrons that matters, since the electron distribution has a large effect on the production of the various molecular species and on the damage incurred on thin oxide layers. This problem should be reexamined in the light of the new requirements.
Expansion of plasma in rapidly diverging magnetic fields. The usual adiabatic invariants are not preserved in such an environment, but there may be other invariants if the system is axisymmetric. The manner in which the electrons and ions of various energies move will determine the potential and density gradients in the downstream plasma, as well as the ionization occurring there.
Though numerical modeling may ultimately be needed to treat this complicated problem, insight into the physics can be gained by considering general principles such as the invariants mentioned above. Plasma instabilities. All plasmas, particularly magnetized ones, are subject to instabilities. In industrial devices, there can be drift instabilities due to gradients in density or temperature; gravitational instabilities due to curving magnetic field lines; or streaming instabilities due to non-Maxwellian distributions, such as in ECR.
No devastating instabilities have yet been seen, but they will no doubt be found someday. In that case, stabilizing measures, such as minimum-B fields, are well in hand because of what has been learned in magnetic fusion. The theoretical and experimental study of basic plasma phenomena in industrially relevant plasmas will benefit from the experience of personnel with extensive knowledge of plasma physics as well as considerable insight and experience in finding and solving simple, tractable problems within a complicated system.
NRL has such expertise. An opportunity exists for NRL to draw on this expertise and focus its basic research on understanding the intrinsic behavior of low-temperature plasmas. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website. Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.
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Chapter 8 Low-Temperature Plasma Physics. Page 31 Share Cite. Drift waves are known as "the universal instability", and within magnetically confined plasmas, they play an important role in the turbulent transport of heat and particles. It is exciting to work on a machine like the YLPD, as it means that I can observe first hand plasma phenomena discussed in lectures.
This encompasses a large range of physical phenomena, including the behaviour of high energy particle beams, electromagnetism, optics, atomic fine structure, atomic spectral emission and kinetic theory of gases. When completed, the diagnostic will measure the proportions of energetically different particles in the beam. This information is then used to aid with the understanding of many aspects of fusion plasma behaviour, and is of key importance if neutral beams are to play a significant role in the future of fusion energy.
I joined the MSc having worked as a teacher of physics at a secondary school for 2 years. The MSc in Fusion Energy has been hugely enjoyable so far, providing the kind of challenge I missed outside academia.
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I am currently working on my final project, "Computational Modelling of Plasma Eruptions. My project involves looking at one of the leading theories proposed to explain this instability, working with one of the original creators of this theory! It also involves amending existing computer code and writing my own code to try and shed some more light into the causes of this instability.
The motivation is, of course, to find a way to reduce or even eliminate this instability, as large tokamaks will not be able to survive its presence. I first got interested in fusion while studying for my BSc in physics at York, and decided to return for the inaugural year of the MSc after living in Japan.
My project focuses on the theoretical and computational modelling of drift waves; these are instabilities which are thought to produce turbulence in magnetised plasmas, with important consequences for tokamak fusion reactors. I'm really enjoying the challenge of applying the fundamental plasma theory and programming skills I've learnt over the course to understand a specific problem in detail and write a modelling code.
Eventually, I hope to be able to compare my results to experimental data from York's linear plasma device.
Having completed my BSc in Physics at York and being interested in plasma physics as well as excited by the prospect of fusion energy as a future power supply, it was a natural progression for me to join the Fusion Energy MSc course. My MSc project involves looking at the fundamentals of plasma physics diagnostics using a DC glow discharge tube.
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In a glow discharge tube, a plasma is generated by applying a potential difference of several hundred volts across a gas Helium in this case held at low pressure; a mechanism used in fluorescent lamps and plasma-screen televisions. In order to characterise the plasma, I am currently in the process of designing and building a Langmuir probe to measure parameters such as the plasma potential, electron density and electron temperature.
What attracted me most to this particular project was the opportunity to do some real hands-on science, that and actually being able to generate a visible plasma!
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So far, the project has provided me with valuable experience in both problem solving and of working in a professional laboratory environment. Physics University. Dissociation of Carbon Dioxide into Carbon Monoxide using low temperature atmospheric pressure plasmas Steven Thomas Global warming due to greenhouse gases such as carbon dioxide is a growing world wide concern. Vlasovian modelling of high harmonic generation Christopher Davie I'm a graduate from Manchester University, and came back to do physics after a couple of years in industry. Computational modelling of plasma eruptions Christos Stavrou I joined the MSc having worked as a teacher of physics at a secondary school for 2 years.
The motivation is, of course, to find a way to reduce or even eliminate this instability, as large tokamaks will not be able to survive its presence Theory of drift waves in magnetised plasmas Tom Williams I first got interested in fusion while studying for my BSc in physics at York, and decided to return for the inaugural year of the MSc after living in Japan.
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