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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Charge exchange in ion-atom collisions relevant to fusion plasma diagnostics

Davies, Peter George January 1998 (has links)
Total charge exchange and excitation cross-sections are presented for collisions between He(^2+) ions and helium atoms, the laboratory frame collision energy being in the range 16-800keV. Cross-sections from the helium ground state and the He(ls2s(^1)S) and He(ls2s(^3)S) metastable states are calculated. The calculations were performed using the semiclassical impact parameter model where wave-functions are expressed as an expansion of two-electron atomic basis states. Transfer channels included plane-wave translation factors. The transition He(^+)(n = 4) → He(^+)(n = 3) results in the emission of visible light (468.5nm) which is observed in the JET fusion device. Helium beam injection into the JET device introduces some of the atoms in initially excited states. Even a small fraction of metastable helium effects the observed 468.5nm spectrum significantly because of the very large charge exchange cross-sections. Accurate charge exchange cross-sections to the He(^+)(n = 4) states are required to analyse the spectroscopic data used in the diagnosis of the plasma. The cross-sections produced are therefore also presented in a form suitable for direct inclusion into the plasma analysis database. Where possible the current results are compared to previous calculations. Total charge exchange cross-sections from the He(ls2s(^1)S) state are in good agreement with the previous one-electron calculation. Charge exchange cross-sections from the triplet state are found to differ with those from the singlet. The results are discussed in the context of their usefulness in the diagnosis of fusion plasmas. Suggestions for further work are made.
142

Microwave resonant cavity measurements of electron loss processes in caesium plasmas

Harris, J. H. January 1980 (has links)
No description available.
143

Langmuir probe measurements in the divertor plasma of the JET tokamak

Monk, Raymond David January 1996 (has links)
This thesis describes the design and application of a new array of Langmuir probes to measure the plasma parameters in the divertor region of the Joint European Torus (JET) tokamak. A novel probe tip design was developed to withstand the high heat fluxes in the divertor region following thermal analysis and beam tests to identify the most suitable material. The probes operate in the "very strong magnetic field" regime with a large projected area (4mm2) and incidence angle to the magnetic field (> 10°) to avoid the sheath expansion effects associated with flush mounted divertor probes. The probes may be remotely configured as single, triple or floating probes. The combination of triple probe measurements and strike point sweeping has provided unique high resolution profiles of plasma parameters across the divertor target. Emphasis is placed upon the evaluation of probe interpretation assumptions and comparison with non-disturbing diagnostics to assess the reliability of the measurements. The distortion of the probe current-voltage characteristics is strongest for high recycling and detached divertor conditions. Single probe analysis methods overestimate the electron temperature while the virtual asymmetric double probe assumption matches well the functional form of the current-voltage characteristics and is more consistent with independent measurements and numerical modelling than single probe interpretation. However, the effects of plasma resistivity remain difficult to evaluate quantitatively. Analysis of the divertor plasma parameters over a wide range of conditions is presented. The behavior of the ion fluxes and parallel gradients during high recycling and detached discharges is studied and compared with predictions from simple analytical models of detachment. Numerical models are used to study the impurity production from the divertor target plate. A new technique of evaluating the plasma parameters both between and during Edge Localized Modes (ELMs) using the triple probes is applied to study the influence of active pumping on the divertor parameters.
144

The use of Langmuir probe techniques to determine the properties of the plasma produced by a duoplasmatron source

Walmsley, H. L. January 1979 (has links)
No description available.
145

Ultraviolet radiation from low current density electrical discharges

Sattar, K. A. January 1978 (has links)
No description available.
146

Mass energy analysis of processing plasmas

Surowiec, Roman January 1994 (has links)
No description available.
147

A diagnostic investigation of RF plasma

Chang-jin, Wu January 1991 (has links)
No description available.
148

Laser plasma interactions using ultrashort laser pulses

Fabrikesi, E. T. January 1981 (has links)
No description available.
149

X-ray absorption spectroscopy of dense, shock compressed, laser plasma

Goodman, D. A. January 1992 (has links)
No description available.
150

Optical and particle diagnostics in laser produced plasma

Ahmad, Zahrah January 1992 (has links)
No description available.

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