Untersuchungen zur Wandkonditionierung mit mikrowellenerzeugten Plasmen in einem toroidalen Magnetfeld
Untersuchungen zur Wandkonditionierung mit mikrowellenerzeugten Plasmen in einem toroidalen Magnetfeld
One main problem for the use of the controlled fusion as possible energy source for the future is the interaction between of the hot fusion plasma with the surrounding wall components of the vacuum vessel. These parts are hit by high energetic, charged or neutral particles from the plasma which can...
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Personal Name(s): | Ihde, J. (Corresponding author) |
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Contributing Institute: |
Publikationen vor 2000; PRE-2000; Retrocat |
Imprint: |
Jülich
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
2001
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Physical Description: |
III, 169 p. |
Document Type: |
Report Book |
Research Program: |
ohne Topic |
Series Title: |
Berichte des Forschungszentrums Jülich
3935 |
Link: |
OpenAccess OpenAccess |
Publikationsportal JuSER |
One main problem for the use of the controlled fusion as possible energy source for the future is the interaction between of the hot fusion plasma with the surrounding wall components of the vacuum vessel. These parts are hit by high energetic, charged or neutral particles from the plasma which can cause the release of wall material. This leads an the one hand side to a limited life time of the high load components, as limiter or divertor plates, and an the other hand side lt cause a contamination of the fusion plasma. The eroded particles penetrate into the discharge volume so that the mixture of deuterium and tritium is diluted and cooled down by radiation losses. To reduce these negative effects lt is indispensable to condition the vessel walls regular by deposition of thin, oxygen gettering layers using reactive gases like silane (S$_{i}$H$_{4}$) er diborane (B$_{2}$H$_{6}$) and to remove accumulated impurities. These methods have been mainly developed at the experimental device TEXTOR at the research centre Jülich [9,10,11] and are successfully practised at many fusion devices by using glow discharges . The implementation of superconducting field coils in future fusion devices will lead to significant extended discharge duration but will also require new techniques for the wall conditioning, because glow discharges are not compatible with the permanent magnetic fields. Therefore, this thesis is dedicated to the investigation of microwave generated plasmas in a toroidal magnetic field. In the first part the discharge is characterised in dependence an the selectable parameters magnetic field strength, neutral gas pressure and microwave input power. Spatial measurements of the electron density and temperature were done for different process gases to allow an extrapolation of the results an the plasma parameter during the layer deposition in reactive gaseous like methane (CH$_{4}$) or acetylene (C$_{2}$H$_{2}$). As a result of the application of various diagnostics the spatial distribution of the film thickness an the wall of the vacuum vessel could be distinguished. Further an the composition of the layers by carbon and hydrogen could by analysed and the thermal stability of the fiems was investigated ex-situ.The results of these measurements leads to an improved understanding an the mechanism of the film growth and the influence of neutral radicals and charged hydrocarbons an it. In addition the erosion of the deposited layers by discharges in hydrogen, deuterium and oxygen has been characterised by mass spectrometry and investigation of the layer thickness by interference colour analysis. |