89 research outputs found
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WHIST transport analysis of high neutron production, ICRH heated, pellet fueled jet plasmas
The WHIST 1-1/2-D predictive transport code is used to model the particle and energy transport of JET pellet-fueled, ICRH-heated plasmas. Pellet injection during the current rise phase was used to produce strong central peaking of the particle density followed by central ICRH heating and led to transient period of enhanced confinement. The evolution of the density profile as well as the electron and ion temperature profiles and strong ICRH heating conditions are examined during this period of enhanced confinement in the context of models for particle and energy transport. Because WHIST is a predictive transport code, it requires models for particle and energy sources and transport coefficients. The analysis procedure thus consists of modeling the particle source terms (pellets, gas, and recycled neutrals), energy source terms (ohmic and ICRH heating), and energy loss terms (primarily radiation), and varying the transport models until the best qualitative and quantitative agreement is obtained between calculated and observed quantities. We find that plasma behavior is well described during the first second of ICRH heating following pellet injection by the same transport coefficients that describe the ohmic plasma. The distinction between electron and ion thermal losses depends on the relative heating rates of electrons and ions as determined by the ICRH model, as well as the radiation losses. 10 refs., 4 figs
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A two-stage pneumatic repeating pellet injector for refueling magnetically confined plasmas in long-pulse fusion experiments
An experiment to demonstrate the feasibility of a repetitive pneumatic pellet injector at 1 Hz in the velocity range of 2 to 3 knVs was carried out in a collaboration between Oak Ridge National Laboratory and ENEA Frascati, in the context of a cooperative agreement between the US Department of Energy and EURATOM-ENEA Association. The third round of this experiment was completed in May 1995. Both the operation and performance of the equipment were improved, and the original objectives of the collaboration have been met. The facility was also briefly operated with neon pellets to explore the potential for producing fast ``killer`` pellets for disruption amelioration applications. Speeds of 1.7 km/s were achieved using a piston mass of 43 g. Higher speeds should be achievable with a system specifically designed for neon or other higher Z gases. Finally, tests were performed with thin boron carbide coatings (2 {mu}m) on the Ergal pistons. The test results were encouraging because piston friction was reduced was the piston wear
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Continuous pellet fueling experiments on D-III
A centrifuge pellet injector developed at ORNL was used to continuously fuel beam-heated limiter discharges in D-III. This injector was capable of producing and maintaining a high density neutral beam-heated plasma without auxilary gas fueling. Viewgraphs from the presentation are included
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Fueling of magnetic-confinement devices
A general overview of the fueling of magnetic confinement devices is presented, with particular emphasis on recent experimental results. Various practical fueling mechanisms are considered, such as cold gas inlet (or plasma edge fueling), neutral beam injection, and injection of high speed cryogenic hydrogen pellets. The central role played by charged particle transport and recycle of plasma particles from material surfaces in contact with the plasma is discussed briefly. The various aspects of hydrogen pellet injection are treated in detail, including applications to the production of high purity startup plasmas for stellarators and other devices, refueling of tokamak plasmas, pellet ablation theory, and the technology and performance characteristics of low and high speed pellet injectors
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18th IAEA Fusion Energy Conference Summary of Technology and Power Plans
There were 90 papers presented at the Conference in the category of Technology and Power Plants accounting for about 25% of the total number of contributions. As was the case at the previous meeting, a large number of papers dealt with the ITER-Engineering Design Activity (EDA) and ITER technology R&D. In the author's opinion, the rapid progress made during the ITER EDA extension on the completion of the new ITER-FEAT design and its physics and technology R&D validation stands out as the highlight of the meeting. Steady progress is being made on several other technology fronts as well. The results point towards emerging research trends in the following areas: steady-state operation with advanced performance and the increasingly important role of enabling technologies in achieving this goal, advanced, high-performance, environmentally attractive materials for the fusion energy goal, reactor and near-term applications studies that exploit advances both in the physics and technology fronts for lower cost of electricity and improved safety and environmental features, and socioeconomic studies that are helping to promote the attractive features of fusion and its public acceptance. The remaining sections of this paper are organized along the lines of these major themes; namely, ITER EDA Design, ITER Technology R&D, Progress Towards Advanced Performance and Steady State, Compact Cu Burning Plasma Experiments and Neutron Sources, Advanced Materials Research, Power Plant Design and Economic Forecasts, and Conclusions
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Pellet injector development at ORNL
Oak Ridge National Laboratory (ORNL) has been developing pellet injection systems for plasma fueling experiments on magnetic fusion confinement devices for about 20 years. Recently, the development has focused on meeting the complex fueling needs of the International Thermonuclear Experimental Reactor (ITER) and future reactors. The proposed ITER fueling system will use a combination of deuterium- tritium (D-T) gas puffing and pellet injection to achieve and maintain ignited plasmas. The pellet injection system will have to provide D-T fueling for much longer pulse lengths (up to {approx}1000 s) than present day applications (typically limited to less than several seconds). In this paper, we describe the ongoing pellet injector development activities at ORNL, including the following three in direct support of ITER: (1) an improved pellet feed system for the centrifuge injector, (2) a steady-state extruder feed system, and (3) tritium extruder technology. In addition to the major activities, a repeating two-stage light gas gun for high-speed pellet injection ({approx}2.5 km/s) has been developed in a collaboration with ENEA Frascati; also, the production of impurity pellets (Ne, Ar, and Kr) has been demonstrated using the DIII-D and Tokamak Fusion Test Reactor pneumatic pellet injection system
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