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Divertor Particle Exhaust And Wall Inventory On Diii D
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Book Synopsis Divertor Particle Exhaust and Wall Inventory on DIII-D. by :
Download or read book Divertor Particle Exhaust and Wall Inventory on DIII-D. written by and published by . This book was released on 1995 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many tokamaks achieve optimum plasma performance by achieving low recycling; various wall conditioning techniques including helium glow discharge cleaning (HeGDC) are routinely applied to help achieve low recycling. Many of these techniques allow strong, transient wall pumping, but they may not be effective for long-pulse tokamaks, such as the International Thermonuclear Experimental Reactor (ITER), the Tokamak Physics Experiment (TPX), Tore Supra Continu, and JT-60SU. Continuous particle exhaust using an in-situ pumping scheme may be effective for wall inventory control in such devices. Recent particle balance experiments on the Tore Supra and DIII-D tokamaks demonstrated that the wall particle inventory could be reduced during a given discharge by use of continuous particle exhaust. In this paper we report the first results of wall inventory control and good performance with the in-situ DIII-D cryopump, replacing the HeGDC normally applied between discharges.
Book Synopsis Recent DIII-D Divertor Research by :
Download or read book Recent DIII-D Divertor Research written by and published by . This book was released on 1995 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: DIII-D currently operates with a single- or double-null open divertor and graphite walls. Active particle control with a divertor cryopump has demonstrated density control, efficient helium exhaust, and reduction of the inventory of particles in the wall. Gas puffing of D2 and impurities has demonstrated reduction of the peak divertor beat flux by factors of 3--5 by radiation. A combination of active cryopumping and feedback-controlled D2 gas puffing has produced similar divertor heat flux reduction with density control. Experiments with neon puffing have shown that the radiation is equally-divided between a localized zone near the X-point and a mantle around the plasma core. The density in these experiments has also been controlled with cryopumping. These experimental results combined with modeling were used to develop the new Radiative Divertor for DIII-D. This is a double-null slot divertor with four cryopumps to provide particle control and neutral shielding for high-triangularity advanced tokamak discharges. UEDGE and DEGAS simulations, benchmarked to experimental data, have been used to optimize the design.
Book Synopsis Hydrogen Recycling at Plasma Facing Materials by : C.H. Wu
Download or read book Hydrogen Recycling at Plasma Facing Materials written by C.H. Wu and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 351 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most important issues in the construction of future magnetic confinement fusion machines is that of the materials of which they are constructed, and one of the key points of proper material choice is the recycle of hydrogen isotopes with materials at the plasma face. Tritium machines demand high safety and economy, which in turn requires the lowest possible T inventory and smallest possible permeation through the plasma facing materials. The recycle behaviour of the in-vessel components must also be known if the plasma reaction is to predictable and controllable, and finally, the fuel cycle and plasma operating regimes may be actively controlled by special materials and methods. The book discusses both laboratory experiments exploring the basic properties of non-equilibrium hydrogen-solid systems (diffusion, absorption, boundary processes) and experimental results obtained from existing fusion machines under conditions simulating future situations to some extent. Contributions are from experts in the fields of nuclear fusion, materials science, surface science, vacuum science and technology, and solid state physics.
Download or read book INIS Atomindex written by and published by . This book was released on 1996 with total page 730 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis PARTICLE EXHAUST SCHEMES IN THE DIII-D ADVANCED DIVERTOR CONFIGURATION. by : M.M. MENON.
Download or read book PARTICLE EXHAUST SCHEMES IN THE DIII-D ADVANCED DIVERTOR CONFIGURATION. written by M.M. MENON. and published by . This book was released on 1989 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Energy Research Abstracts written by and published by . This book was released on 1992-02 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Particle Exhaust Schemes in the DIII-D Advanced Divertor Configuration by :
Download or read book Particle Exhaust Schemes in the DIII-D Advanced Divertor Configuration written by and published by . This book was released on 1989 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: For density control in long-pulse operation, the open divertor on the DIII-D tokamak will be equipped with a baffled chamber and a pumping system. The throat of the baffle chamber is sized to provide optimal pumping for the typical plasma equilibrium configuration. Severe limitations on the toroidal conductance of this baffle chamber require the use of in-vessel pumping to achieve the desired particle exhaust of about 25 Torr{center dot}l/s. Two separate pumping schemes are considered: an array of titanium getter modules based on the design developed by the Tore Supra team and a cryocondensation pump. The merits and demerits of each scheme are analyzed, and the design considerations introduced by the tokamak environment are brought out. 3 refs., 5 figs.
Download or read book Nuclear Fusion written by and published by . This book was released on 2001-11 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Particle Exhaust Modeling for the Collaborative DIII-D Advanced Divertor Program by :
Download or read book Particle Exhaust Modeling for the Collaborative DIII-D Advanced Divertor Program written by and published by . This book was released on 1990 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: A principal objective of the collaborative DIII-D Divertor Program (ADP) is to achieve density control in H-mode discharges with edge biasing and with continuous particle exhaust at a rate determined by the external fueling sources (typically 20 Torr{center dot}L/s). The divertor baffle-bias ring system has been optimized for pumping speeds (almost equal to)50,000 L/s with the neutral transport code DEGAS. With an entrance slot conductance of 50,000 L/s, a pumping speed of the same order is required to remove half of the (almost equal to)40 Torr{center dot}L/s that enters the baffle chamber for typical H-mode discharges. Increasing the exhaust fraction with higher pumping speed is self-limiting, owing to the attendant reduction of the recycling flux. The effects of pumping on the plasma core, scrape-off layer (SOL), and divertor have been estimated with a model that self-consistently couples the transport in these regions. The required (almost equal to)50,000 L/s pumping speed can be achieved with either titanium getter pumps or cryopumps. Evaluation of both systems has led to the conclusion that cryopumps will be more compatible with the environment of the DIII-D divertor. 8 refs., 7 figs.
Book Synopsis Government Reports Announcements & Index by :
Download or read book Government Reports Announcements & Index written by and published by . This book was released on 1996 with total page 814 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Divertor Heat and Particle Control Experiments on the DIII-D Tokamak by :
Download or read book Divertor Heat and Particle Control Experiments on the DIII-D Tokamak written by and published by . This book was released on 1994 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper we present a summary of recent DIII-D divertor physics activity and plans for future divertor upgrades. During the past year, DIII-D experimental effort was focused on areas of active heat and particle control and divertor target erosion studies. Using the DIII-D Advanced Divertor system we have succeeded for the first time to control the plasma density and demonstrate helium exhaust in H-mode plasmas. Divertor heat flux control by means of D2 gas puffing and impurity injection were studied separately and in, both cases up to a factor of five reduction of the divertor peak heat flux was observed. Using the DiMES sample transfer system we have obtained erosion data on various material samples in well diagnosed plasmas and compared the results with predictions of numerical models.
Book Synopsis Radiative and SOL Experiments in Open and Baffled Divertors on DIII-D. by :
Download or read book Radiative and SOL Experiments in Open and Baffled Divertors on DIII-D. written by and published by . This book was released on 1998 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors present recent progress towards an understanding of the physical processes in the divertor and scrape-off-layer (SOL) plasmas in DIII-D. This has been made possible by a combination of new diagnostics, improved computational models, and changes in divertor geometry. They have focused primarily on ELMing H-mode discharges. The physics of Partially Detached Divertor (PDD) plasmas, with divertor heat flux reduction by divertor radiation enhancement using D2 puffing, has been studied in 2-D, and a model of the heat and particle transport has been developed that includes conduction, convection, ionization, recombination, and flows. Plasma and impurity particle flows have been measured with Mach probes and spectroscopy and these flows have been compared with the UEDGE model. The model now includes self-consistent calculations of carbon impurities. Impurity radiation has been increased in the divertor and SOL with puff and pump techniques using SOL D2 puffing, divertor cryopumping, and argon puffing. The important physical processes in plasma-wall interactions have been examined with a DiMES probe, plasma characterization near the divertor plate, and the REDEP code. Experiments comparing single-null (SN) plasma operation in baffled and open divertors have demonstrated a change in the edge plasma profiles. These results are consistent with a reduction in the core ionization source calculated with UEDGE. Divertor particle control in ELMing H-mode with pumping and baffling has resulted in reduction in H-mode core densities to n{sub e}/n{sub gw} (almost equal to) 0.25. Divertor particle exhaust and heat flux has been studied as the plasma shape was varied from a lower SN, to a balanced double null (DN), and finally to an upper SN.
Book Synopsis 16th IEEE/NPSS Symposium Fusion Engineering by :
Download or read book 16th IEEE/NPSS Symposium Fusion Engineering written by and published by . This book was released on 1995 with total page 900 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Energy and Particle Transport in the Radiative Divertor Plasmas of DIII-D. by :
Download or read book Energy and Particle Transport in the Radiative Divertor Plasmas of DIII-D. written by and published by . This book was released on 1997 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: It has been argued that divertor energy transport dominated by parallel electron thermal conduction, or q(parallet to) = -kT522 dT{sub e}/ds(parallet to), leads to severe localization of the intense radiating region and ultimately limits the fraction of energy flux that can be radiated before striking the divertor target. This is due to the strong T52{sub e} dependence of electron heat conduction which results in very short spatial scales of the T{sub e} gradient at high power densities and low temperatures where deuterium and impurities radiate most effectively. However, we have greatly exceeded this constraint on DIII-D with deuterium gas puffing which reduces the peak heat flux to the divertor plate a factor of 5 while distributing the divertor radiation over a long length.
Download or read book Fusion Energy written by and published by . This book was released on 1997 with total page 962 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Variation of Particle Control with Changes in Divertor Geometry by :
Download or read book Variation of Particle Control with Changes in Divertor Geometry written by and published by . This book was released on 2004 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent experiments on DIII-D point to the importance of two factors in determining how effectively the deuterium particle inventory in a tokamak plasma can be controlled through pumping at the divertor target(s): (1) the divertor magnetic balance, i.e., the degree to which the divertor topology is single-null (SN) or double-null (DN), and (2) the direction of the of Bx{divergent}B ion drift with respect to the X-point(s). Changes in divertor magnetic balance near the DN shape have a much stronger effect on the particle exhaust rate at the inner divertor target(s) than on the particle exhaust rate at the outer divertor target(s). The particle exhaust rate for the DN shape is strongest at the outer strike point opposite the Bx{divergent}B ion particle drift direction. Our data suggests that the presence of Bx{divergent}B and ExB ion particle drifts in the scrapeoff layer (SOL) and divertors play an important role in the particle exhaust rates of DN and near-DN plasmas. Particle exhaust rates are shown to depend strongly on the edge (pedestal) density n{sub e, PED}. In the lower range of densities considered in this study, i.e., n{sub e, PED}/ n{sub GREENWALD}
Book Synopsis Recent Results from the DIII-D Tokamak by :
Download or read book Recent Results from the DIII-D Tokamak written by and published by . This book was released on 1995 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of the DIII-D program is to provide the integrated basis for commercially attractive steady state fusion power plants. Significant progress toward this goal has been achieved, enabled by system improvements including an error field correction coil, an expanded diagnostic set, a digital plasma control system, and high power rf systems. Simultaneous improvements in both the confinement and stability have been achieved during both VH-mode and negative central shear discharges. Fully non-inductive discharges with high bootstrap current fraction have been obtained. The divertor program has demonstrated simultaneous reduction of divertor heat flux and effective particle control using gas puffing and an in-vessel cryopump. Control of the wall particle inventory, He exhaust, and characterization of the scrapeoff layer and divertor plasma have been achieved. Progress has also been made in addressing additional specific needs for ITER: investigation of basic transport scaling, disruption characterization and avoidance, material erosion, and steady state beta limits.
