OEDGE Modeling of the DIII-D H-Mode 13CH4 Puffing Experiment PDF Download
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
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Book Description
Use of carbon in tokamaks leads to a serious tritium retention issue due to co-deposition. To further investigate the processes involved, a detached ELMy H-mode (6.5 MW NBI) experiment was performed on DIII-D in which 13CH4 was puffed into the main vessel through the toroidally symmetric pumping plenum at the top of lower single-null discharges. Subsequently, the 13C content of tiles taken from the vessel wall was measured. The interpretive OEDGE code was used to model the results. The 13C deposition pattern could be reproduced, in general shape and magnitude, by assuming in the code the existence of a parallel flow and a radial pinch in the scrape-off layer. Parallel flows of Mach (almost equal to) 0.3 toward the inner divertor and a radial pinch (almost equal to)10 to 20 m/s (+ R-direction) were found to yield 13C deposition comparable to the experiment.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 18
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Book Description
Use of carbon in tokamaks leads to a serious tritium retention issue due to co-deposition. To further investigate the processes involved, a detached ELMy H-mode (6.5 MW NBI) experiment was performed on DIII-D in which 13CH4 was puffed into the main vessel through the toroidally symmetric pumping plenum at the top of lower single-null discharges. Subsequently, the 13C content of tiles taken from the vessel wall was measured. The interpretive OEDGE code was used to model the results. The 13C deposition pattern could be reproduced, in general shape and magnitude, by assuming in the code the existence of a parallel flow and a radial pinch in the scrape-off layer. Parallel flows of Mach (almost equal to) 0.3 toward the inner divertor and a radial pinch (almost equal to)10 to 20 m/s (+ R-direction) were found to yield 13C deposition comparable to the experiment.
Author: John David Elder
Publisher:
ISBN: 9780494393710
Category : Aerospace engineering
Languages : en
Pages : 155
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Book Description
In 2003 and 2005 13CH4 puffing experiments were conducted on DIII-D [1] in L and ELMy H mode plasmas respectively. The motivation for these experiments was to develop a greater understanding of impurity creation, transport and deposition for hydrocarbons which are produced at the walls of DIII-D by chemical sputtering. In both experiments, tiles from around the vessel were removed after the experiment was complete and the distribution of the 13C deposition was measured using nuclear reaction analysis. During each of these experiments the plasma conditions and emissions were monitored by a number of direct and spectroscopic diagnostics including Langmuir probes, Thomson scattering, the multichord divertor spectrometer, filterscopes, reciprocating probes and others. These diagnostic measurements are used in the thesis to develop a background plasma solution for the experiments through the procedure of empirical plasma reconstruction. These background plasma solutions are used as the basis for modeling the emissions, transport and deposition of the 13C resulting from the breakup of 13CH4 using the OEDGE code. OEDGE was enhanced by the addition of improved methane breakup kinetics models, improved peripheral particle transport, improved support for line profile modeling as well as many other features. The modeling successfully reproduces most of the spectroscopic measurements as well as the observed 13C deposition patterns in both distribution and magnitude. In order to match the experimental results, fast parallel transport in the SOL had to be imposed on the carbon ions. In addition, a radial pinch was required in the SOL for both the L and H mode experiments to move the carbon closer to the separatrix so that it could deposit where it was measured experimentally. Without both of these flows the simulations were unable to replicate the experimental observations. The effects of radial variation in the parallel flow and erosion of deposited 13C were also both investigated. It was found that neither of these processes by itself appears to be capable of replicating the experimental results.
Author:
Publisher:
ISBN:
Category : Fusion reactors
Languages : en
Pages : 406
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Book Description
