An experimental investigation of the impurity behaviour of the Reversed Field Pinch (RFP) HBTX1A/B is presented. The investigation was initiated by determining the impurity composition of the plasma through spectral surveys utilising both photographic and multi-channel techniques. The principal low Z impurities were found to be carbon and oxygen while the principal high Z impurity was iron with smaller amounts of chromium and nickel. The investigation was extended using quantitative techniques in the Extreme Vacuum Ultraviolet (EVUV), Vacuum Ultraviolet (VUV) and Ultraviolet(UV)/visible regions of the spectrum. A novel technique involving a scintillator imaged on to an Optical Multichannel Analyser (OMA) was used for quantitative work in the VUV region and a unique scanning toroidal mirror system was also developed for this range. It was found that the impurity concentration was a small fraction of the electron density (5% 0, -1% C, -0.2% Fe) and, in conjunction with the bolometric results from other workers, it was found that the impurity radiation was a small fraction (-4%) of the global input power (for I/N >7 x 10-14 A.m) and did not lead to radiative cooling at any position in the discharge. The value of the resistivity calculated from the impurity composition was significantly less than the value obtained from helicity balance calculations, assuming a perfect boundary. The impurity diffusion coefficient for carbon was determined using a unique technique based on spatial measurements of CV emission. The measured value of 100-150 m2.s-1 was anomalously high compared to neoclassical predictions. It was not possible to determine the diffusion mechanisms of either the bulk plasma or the impurities, hence this measurement represents the first step in a more detailed investigation of RFP impurity dynamics.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:704433 |
| Date | January 1988 |
| Creators | Manley, Adrian Mark |
| Publisher | Royal Holloway, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://repository.royalholloway.ac.uk/items/399b20c9-df81-40ed-aa9b-3d872fec13ce/1/ |
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