30 research outputs found
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Time to pause before the next step
Many scientists, who have staunchly supported ITER for years, are coming to realize it is time to further rethink fusion energy`s development strategy. Specifically, as was suggested by Grant Logan and Dale Meade, and in keeping with the restructuring of 1996, a theme of better, cheaper, faster fusion would serve the program more effectively than ``demonstrating controlled ignition...and integrated testing of the high-heat-flux and nuclear components required to utilize fusion energy...`` which are the important ingredients of ITER`s objectives. The author has personally shifted his view for a mixture of technical and political reasons. On the technical side, he senses that through advanced tokamak research, spherical tokamak research, and advanced stellarator work, scientists are coming to a new understanding that might make a burning-plasma device significantly smaller and less expensive. Thus waiting for a few years, even ten years, seems prudent. Scientifically, there is fascinating physics to be learned through studies of burning plasma on a tokamak. And clearly if one wishes to study burning plasma physics in a sustained plasma, there is no other configuration with an adequate database on which to proceed. But what is the urgency of moving towards an ITER-like step focused on burning plasma? Some of the arguments put forward and the counter arguments are discussed here
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Scaling results and future plans for the Los Alamos FRX-C experiment
The particle containment time in FRX-C is measured to be 140 +- 30 ..mu..s. This corresponds to R/sup 2/ scaling when compared with earlier FRX-B results and agrees with predictions based on lower-hybrid cross-field diffusion. Further improvement in confinement may be possible by translating a field-reversed configuration (FRC) in such a way as to increase x/sub s/
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FRX-C and multiple-cell experiments
Two new compact torus experiments have recently been proposed and one (FRX-C) is now under construction. The proposed experiments are based on recent theoretical advances and experimental results obtained with the LASL FRX-A and FRX-B field-reversed theta-pinch devices. These recent experiments demonstrate a formation method and establish some of the confinement properties for one type of plasma compact torus - an elongated prolate plasma torus confined by purely poloidal magnetic field. The plasma displays a quiescent phase, free of any gross MHD instabilities, that persists much longer than either characteristic MHD times or open-field line loss times. (MOW
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Proceedings of the third symposium on the physics and technology of compact toroids in the magnetic fusion energy program
This document contains papers contributed by the participants of the Third Symposium on Physics and Technology of Compact Toroids in the Magnetic Fusion Energy Program. Subjects include reactor aspects of compact toroids, energetic particle rings, spheromak configurations (a mixture of toroidal and poloidal fields), and field-reversed configurations (FRC's that contain purely poloidal field)
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Radiation hardening of diagnostics
The world fusion program has advanced to the stage where it is appropriate to construct a number of devices for the purpose of burning DT fuel. In these next-generation experiments, the expected flux and fluence of 14 MeV neutrons and associated gamma rays will pose a significant challenge to the operation and diagnostics of the fusion device. Radiation effects include structural damage to materials such as vacuum windows and seals, modifications to electrical properties such as electrical conductivity and dielectric strength and impaired optical properties such as reduced transparency and luminescence of windows and fiber optics during irradiation. In preparation for construction and operation of these new facilities, the fusion diagnostics community needs to work with materials scientists to develop a better understanding of radiation effects, and to undertake a testing program aimed at developing workable solutions for this multi-faceted problem. A unique facility to help in this regard is the Los Alamos Spallation Radiation Effects Facility, a neutron source located at the beam stop of the world's most powerful accelerator, the Los Alamos Meson Physics Facility (LAMPF). The LAMPF proton beam generates 10{sup 16} neutrons per second because of spallation'' reactions when the protons collide with the copper nuclei in the beam stop
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On the Possible Equilibria in a Configuration of the Type of a Diffuse Pinch
Consider an axisymmetric equilibrium in a configuration where the current density j has only r and z components, and the magnetic field, accordingly, has only the {var_phi} component. Such configurations are of interest for magnetized target fusion (MTF) [1]: they include a simple diffuse Z pinch configuration and a MAGO configuration. Both can be, in principle, imploded by conducting shells to create a plasma with fusion-grade parameters. To be of interest for fusion, these configurations have to provide MHD equilibria acceptable from the viewpoint of confinement requirements. In the present note the authors analyze possible equilibria and show that only equilibria where the plasma pressure is a function of a radial coordinate (no axial dependence) are possible. A framework for such an analysis is outlined, e.g., in Shafranov's survey in ``Reviews of Plasma Physics''. In an arbitrary geometry the analysis may be quite cumbersome. What the authors show here is, that in the geometry of the type of an axisymmetric Z pinch equilibrium analysis is reduced to a set of simple algebraic relations, and allows one to come to very robust and reliable conclusions with regard to the possible equilibria
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Parameters of a possible FRC adiabatic compression experiment
An experiment is described that would address the following research goals for field-reversed configurations (FRC). (a) Test FRC stability with a number of ion gyroradii relative to the plasma radius substantially greater than in present experiments. (b) Increase the electron temperature sufficiently to test the physics of electron energy confinement and of trapped-flux losses. (c) Improve confinement while remaining in a density regime (n less than or equal to 5 x 10/sup 15/ cm/sup -3/) most likely to be relevant to fusion power production