OEDGE Modeling of 13C Deposition in the Inner Divertor of DIII-D. PDF Download
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Author:
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Languages : en
Pages : 2
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Book Description
Use of carbon in tokamaks leads to a major tritium retention issue due to co-deposition. To investigate this process a low power (no beams) L-mode 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. It was found that the 13C deposition pattern is controlled by: (a) source strength of 13C, (b) radial location of the 13C source, (c) D{sub {perpendicular}}, (d) M{sub {parallel}}, the scrape-off layer parallel Mach number. Best agreement was found for (a) (almost equal to)50% conversion efficiency 13CH4 --> 13C+, (b) 13C+ source (almost equal to)3.5 cm outboard of separatrix near 13CH4 injection location, (c)D{sub {perpendicular}} (almost equal to) 0.3 m2s−1, (d) M{sub {parallel}} (almost equal to) 0.4 toward inside.
Author:
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Category :
Languages : en
Pages : 2
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Book Description
Use of carbon in tokamaks leads to a major tritium retention issue due to co-deposition. To investigate this process a low power (no beams) L-mode 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. It was found that the 13C deposition pattern is controlled by: (a) source strength of 13C, (b) radial location of the 13C source, (c) D{sub {perpendicular}}, (d) M{sub {parallel}}, the scrape-off layer parallel Mach number. Best agreement was found for (a) (almost equal to)50% conversion efficiency 13CH4 --> 13C+, (b) 13C+ source (almost equal to)3.5 cm outboard of separatrix near 13CH4 injection location, (c)D{sub {perpendicular}} (almost equal to) 0.3 m2s−1, (d) M{sub {parallel}} (almost equal to) 0.4 toward inside.
Author: S. Allen
Publisher:
ISBN:
Category :
Languages : en
Pages : 2
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Book Description
Use of carbon in tokamaks leads to a major tritium retention issue due to co-deposition. To investigate this process a low power (no beams) L-mode experiment was performed on DIII-D in which {sup 13}CH{sub 4} was puffed into the main vessel through the toroidally-symmetric pumping plenum at the top of lower single-null discharges. Subsequently, the {sup 13}C content of tiles taken from the vessel wall was measured. The interpretive OEDGE code was used to model the results. It was found that the {sup 13}C deposition pattern is controlled by: (a) source strength of {sup 13}C{sup +}, (b) radial location of the {sup 13}C{sup +} source, (c) D{sub {perpendicular}}, (d) M{sub {parallel}}, the scrape-off layer parallel Mach number. Best agreement was found for (a) {approx}50% conversion efficiency {sup 13}CH{sub 4} {yields} {sup 13}C{sup +}, (b) {sup 13}C{sup +} source {approx}3.5 cm outboard of separatrix near {sup 13}CH{sub 4} injection location, (c)D{sub {perpendicular}} {approx} 0.3 m{sup 2}s{sup -1}, (d) M{sub {parallel}} {approx} 0.4 toward inside.
Author:
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Category :
Languages : en
Pages : 17
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Book Description
Experiments are described which examine the transport and deposition of carbon entering the main plasma scrape-off layer in DIII-D. 13CH4 was injected from a toroidally symmetric source into the crown of lower single-null detached ELMy H-mode plasmas. 13C deposition, mapped by nuclear reaction analysis of tiles, was high at the inner divertor but absent at the outer divertor, as found previously for low density L-mode plasmas. This asymmetry indicates that ionized carbon is swept towards the inner divertor by a fast flow in the scrape-off layer. In the private flux region between inner and outer strike points, carbon deposition was low for L-mode but high for the H-mode plasmas. OEDGE modeling reproduces observed deposition patterns and indicates that neutral carbon dominates deposition in the divertor from detached H-mode plasmas.
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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: P. Stangeby
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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Book Description
For some divertor aspects, such as detached plasmas or the private flux zone, it is not clear that the controlling physics has been fully identified. This is a particular concern when the details of the plasma are likely to be important in modeling the problem--for example, modeling co-deposition in detached inner divertors. An empirical method of ''reconstructing'' the plasma based on direct experimental measurements may be useful in such situations. It is shown that a detached plasma in the outer divertor leg of DIII-D can be reconstructed reasonably well using spectroscopic and probe data as input to a simple onion-skin model and the Monte Carlo hydrogenic code, EIRENE. The calculated 2D distributions of n{sub e} and T{sub e} in the detached divertor were compared with direct measurements from the divertor Thomson scattering system, a diagnostic capability unique to DIII-D.
Author:
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ISBN:
Category :
Languages : en
Pages : 14
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Book Description
Author:
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Category :
Languages : en
Pages : 14
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Book Description
Recently a number of major, unanticipated effects have been reported in tokamak edge research raising the question of whether we understand the controlling physics of the edge. This report is on the first part--here focused on the outer divertor--of a systematic study of the simplest possible edge plasma--no ELMs, no detachment, etc.--for a set of 10 repeat, highly-diagnosed, single-null, divertor discharges in DIII-D. For almost the entire, extensive data set so far evaluated, the matches of experiment and model are so close as to imply that the controlling processes at the outer divertor for these simple plasma conditions have probably been correctly identified and quantitatively characterized in the model. The principal anomaly flagged so far relates to measurements of T{sub e} near the target, potentially pointing to a deficiency in our understanding of sheath physics in the tokamak environment.
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
Author: C.M. Braams
Publisher: CRC Press
ISBN: 9781420033786
Category : Science
Languages : en
Pages : 352
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Book Description
Fusion research started over half a century ago. Although the task remains unfinished, the end of the road could be in sight if society makes the right decisions. Nuclear Fusion: Half a Century of Magnetic Confinement Fusion Research is a careful, scholarly account of the course of fusion energy research over the past fifty years. The authors outline the different paths followed by fusion research from initial ignorance to present understanding. They explore why a particular scheme would not work and why it was more profitable to concentrate on the mainstream tokamak development. The book features descriptive sections, in-depth explanations of certain physical and technical issues, scientific terms, and an extensive glossary that explains relevant abbreviations and acronyms.
