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AIR CORE CRYOGENIC MAGNET COILS FOR FUSION RESEARCH AND HIGH ENERGY NUCLEAR PHYSICIS APPLICATIONS

Description: It is shown that cryogenic techniques offer the possibility of substantially improving the efficiency and practicality of generating high magnetic fields in air-core coils of large size. Over-all reductions in power requirements of as high as 25, by comparison with conventional coils, are predicted, provided high purity conductors and efficient refrigeration cycles are used. (W.D.M.)
Date: October 30, 1959
Creator: Post, R. F. & Taylor, C. E.
Partner: UNT Libraries Government Documents Department

Ambient-temperature passive magnetic bearings: Theory and design equations

Description: Research has been underway at the Lawrence Livermore National Laboratory to build a theoretical and experimental base for the design of ambient-temperature passive magnetic bearings for a variety of possible applications. in the approach taken the limitations imposed by Earnshaw`s theorem with respect to the stability of passive magnetic bearing systems employing axially symmetric permanent-magnet elements are overcome by employing special combinations of elements, as follows: Levitating and restoring forces are provided by combinations of permanent-magnet-excited elements chosen to provide positive stiffnesses (negative force derivatives) for selected displacements (i.e., those involving translations or angular displacement of the axis of rotation). As dictated by Eamshaw`s theorem, any bearing system thus constructed will be statically unstable for at least one of the remaining possible displacements. Stabilization against this displacement is accomplished by using periodic arrays (`Halbach arrays`) of permanent magnets to induce currents in close-packed inductively loaded circuits, thereby producing negative force derivatives stabilizing the system while in rotation. Disengaging mechanical elements stabilize the system when at rest and when below a low critical speed. The paper discusses theory and equations needed for the design of such systems.
Date: December 30, 1997
Creator: Post, R.F. & Ryutov, D.D.
Partner: UNT Libraries Government Documents Department

Anomalous transport in mirror systems

Description: As now being explored for fusion applications confinement systems based on the mirror principle embody two kinds of plasma regimes. These two regimes are: (a) high-beta plasmas, stabilized against MHD and other low frequency plasma instabilities by magnetic-well fields, but characterized by non-Maxwellian ion distributions; (b) near-Maxwellian plasmas, confined electrostatically (as in the tandem mirror) or in a field-reversed region within the mirror cell. Common to both situations are the questions of anomalous transport owing to high frequency instabilities in the non-maxwellian portions of the plasmas. This report will summarize the status of theory and of experimental data bearing on these questions, with particular reference to the high temperature regimes of interest for fusion power.
Date: August 20, 1979
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

Attractive characteristics of mirrors

Description: A summary of the attractive characteristics of mirror devices is presented. Recent progress in development of axisymmetric mirror devices is described. Potentialities of mirrors as a basis for D{sup 3}He fusion power generators and high-flux neutron sources for fusion material tests are discussed.
Date: December 15, 1994
Creator: Post, R. F. & Ryutov, D. D.
Partner: UNT Libraries Government Documents Department

''Ballistic damping'': a proposed method of stabilizing resonant ion cyclotron modes

Description: The essence of the idea is as follows: One or more beams of energetic ions (or neutral atoms that will become ionized) are injected, parallel to the field lines, at radii where the instability electric field has maximum amplitude (say roughly halfway between the axis and the outer radius of the plasma). While in transit through the plasma these ions acquire transverse energy by resonant acceleration, thereby extracting energy from the wave. This imparted energy is then carried out of the confined plasma by the beam particles as they exit through the far mirror. In this way the ballistic damping process introduces a damping mechanism that can be used to inhibit the growth of unstable waves and/or to damp them out before they reach unacceptably high amplitude. It is also shown that the beam power required is substantially lower than the plasma powers involved, scaling in a favorable way with increase in the size of the mirror cell.
Date: July 31, 1978
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

Comments on open-ended magnetic systems for fusion

Description: Differentiating characteristics of magnetic confinement systems having externally generated magnetic fields that are open'' are listed and discussed in the light of their several potential advantages for fusion power systems. It is pointed out that at this stage of fusion research high-Q'' (as deduced from long energy confinement times) is not necessarily the most relevant criterion by which to judge the potential of alternate fusion approaches for the economic generation of fusion power. An example is given of a hypothetical open-geometry fusion power system where low-Q operation is essential to meeting one of its main objectives (low neutron power flux).
Date: September 24, 1990
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

The Design of Large Cryogenic Magnet Coils. Paper No. 2

Description: Preliminary design and experimental work aimed toward fabrication of large magnet coils with encapsulated sodium conductors is outlined. Aspects of cooling cycles are discussed along with heat transfer, thermal stability, and the mechanical reinforcement of such coils. (J.R.D.)
Date: October 30, 1959
Creator: Taylor, C. E. & Post, R. F.
Partner: UNT Libraries Government Documents Department

The electromechanical battery: The new kid on the block

Description: In a funded program at the Lawrence Livermore National Laboratory new materials and novel designs are being incorporated into a new approach to an old concept -- flywheel energy storage. Modular devices, dubbed ``electromechanical batteries`` (EMB) are being developed that should represent an important alternative to the electrochemical storage battery for use in electric vehicles or for stationary applications, such as computer back-up power or utility load-leveling.
Date: August 1, 1993
Creator: Post, R. F.
Partner: UNT Libraries Government Documents Department

Fokker-Planck equation in mirror research

Description: Open confinement systems based on the magnetic mirror principle depend on the maintenance of particle distributions that may deviate substantially from Maxwellian distributions. Mirror research has therefore from the beginning relied on theoretical predictions of non-equilibrium rate processes obtained from solutions to the Fokker-Planck equation. The F-P equation plays three roles: Design of experiments, creation of classical standards against which to compare experiment, and predictions concerning mirror based fusion power systems. Analytical and computational approaches to solving the F-P equation for mirror systems will be reviewed, together with results and examples that apply to specific mirror systems, such as the tandem mirror.
Date: August 11, 1983
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

Fusion power and the environment

Description: Environmental characteristics of conceptual fusion-reactor systems based on magnetic confinement are examined quantitatively, and some comparisons with fission systems are made. Fusion, like all other energy sources, will not be completely free of environmental liabilities, but the most obvious of these-- tritium leakage and activation of structural materials by neutron bombardment-- are susceptible to significant reduction by ingenuity in choice of materials and design. Large fusion reactors can probably be designed so that worst-case releases of radioactivity owing to accident or sabotage would produce no prompt fatalities in the public. A world energy economy relying heavily on fusion could make heavy demands on scarce nonfuel materials, a topic deserving further attention. Fusion's potential environmental advantages are not entirely ''automatic'', converting them into practical reality will require emphasis on environmental characteristics throughout the process of reactor design and engineering. The central role of environmental impact in the long-term energy dilemma of civilization justifies the highest priority on this aspect of fusion. (auth)
Date: June 1, 1975
Creator: Holdren, J.P.; Fowler, T.K. & Post, R.F.
Partner: UNT Libraries Government Documents Department

Fusion reactors as future energy sources

Description: From conference on energy policies and the international system; New, Delhi, India (4 Dec 1973). The need is now apparent for a global energy policy with the following characteristics: Compatibility with environmental and economic factors; large fuel resources, the recovery and exploration of which have minimal environmental impact and which do not introduce disturbing factors into the world political situation. Fusion power in this context is discussed, including assessments of its potential and of the problems yet to be solved in achieving its realization. The proposition is advanced that fusion should be considered as the ultimate source of energy, and that other sources of energy, including conventional nuclear power, should be considered as interim sources. (auth)
Date: January 1, 1973
Creator: Post, R.F. & Ribe, F.L.
Partner: UNT Libraries Government Documents Department

Fusion research: the past is prologue

Description: At this juncture fusion research can be viewed as being at a turning point, a time to review its past and to imagine its future. Today, almost 50 years since the first serious attempts to address the daunting problem of achieving controlled fusion, we have both an opportunity and a challenge. Some predictions place fusion research today at a point midway between its first inception and its eventual maturation - in the middle of the 21st century - when fusion would become a major source of energy. Our opportunity therefore is to assess what we have learned from 50 years of hard work and use that knowledge as a starting point for new and better approaches to solving the fusion problem. Our challenge is to prove the "50 more years" prophesy wrong, by finding ways to shorten the time when fusion power becomes a reality. The thesis will be advanced that in the magnetic confinement approach to fusion open-ended magnetic confinement geometries offer much in responding to the challenge. A major advantage of open systems is that, owing to their theoretically and experimentally demonstrated ability to suppress plasma instabilities of both the MHD and the high-frequency wave-particle variety, the confinement becomes predictable from "classical," i.e., Fokker-Planck-type analysis. In a time of straitened budgetary circumstances for magnetic fusion research now being faced in the United States, the theoretical tractability of mirror-based systems is a substantial asset. In pursuing this avenue it is also necessary to keep an open mind as to the forms that mirror-based fusion power plants might take. For example, one can look to the high-energy physics community for a possible model: This community has shown the feasibility of constructing large and complex particle accelerators using superconducting magnets, vacuum chambers and complicated particle-handling technology, housed in underground tunnels that ...
Date: October 14, 1998
Creator: Post, R F
Partner: UNT Libraries Government Documents Department

Halbach array motor/generators: A novel generalized electric machine

Description: In August 1979, Halbach submitted a paper entitled ``Design of Permanent Multipole Magnets with Oriented Rare Earth Cobalt Material.`` In this paper, he presented a novel method of generating multipole magnetic fields using non-intuitive geometrical arrangements of permanent magnets. In subsequent publications, he further defined these concepts. Of particular interest to one of the authors (RFP) was the special magnet array that generated a uniform dipole field. In 1990 Post proposed the construction of an electric machine (a motor/generator) using a dipole field based on Klaus Halbach`s array of permanent magnets. He further proposed that such a system should be employed as an integral part of ``an electromechanical battery`` (EMB), i.e., a modular flywheel system to be used as a device for storing electrical energy, as an alternative to the electrochemical storage battery. This paper reviews Halbach`s theory for the generation of a dipole field using an array of permanent magnet bars, presents a simple analysis of a family of novel ``ironless`` electric machines designed using the dipole Halbach array, and describes the results obtained when they were tested in the laboratory.
Date: October 28, 1994
Creator: Merritt, B.T.; Post, R.F.; Dreifuerst, G.R. & Bender, D.A.
Partner: UNT Libraries Government Documents Department

The Inductrack Approach to Magnetic Levitation

Description: Concepts developed during research on passive magnetic bearing systems at the Lawrence Livermore National Laboratory gave rise to a new approach to magnetic levitation, the Inductrack. A passive induced-current system employing permanent magnets on the moving vehicle, the Inductrack maximizes levitation forces by a combination of two elements. First, the permanent magnets on the vehicle are arranged in a ''Halbach array,'' a magnet configuration that optimally produces a periodic magnetic field below the array, while canceling the field above the array. Second, the track is made up of close-packed shorted electrical circuits. These circuits couple optimally to the magnetic field of the Halbach array. As a result, levitating forces of order 40 metric tonnes per square meter of Halbach array can be generated, using NdFeB magnets whose weight is a few percent of the levitated weight. Being an induced-current system, the levitation requires motion of the vehicle above a low transition speed. For maglev applications this speed is a few kilometers per hour, walking speed. At rest or in the station auxiliary wheels are needed. The Inductrack is thus fail-safe, that is, drive system failure would only result in the vehicle slowing down and finally settling on its auxiliary wheels. On the basis of theoretical analyses a small model vehicle and a 20-meter-long track was built and tested at speeds of order 12 meters per second. A second model, designed to achieve 10-g acceleration levels and much higher speeds, is under construction under NASA sponsorship, en route to the design of maglev-based launchers for rockets. Some of the presently perceived practical problems of implementing full-scale maglev systems based on the Inductrack concept will be discussed.
Date: April 19, 2000
Creator: Post, R.F. & Ryutov, D.D.
Partner: UNT Libraries Government Documents Department

The Inductrack concept: A new approach to magnetic levitation

Description: This report describes theoretical and experimental investigations of a new approach to the problem of the magnetic levitation of a moving object. By contrast with previously studied levitation approaches, the Inductrack concept concept represents a simpler, potentially less expensive, and totally passive means of levitating a high-speed train. It may also be applicable to other areas where simpler magnetic levitation systems are needed, for example, high-speed test sleds for crash testing applications, or low-friction conveyer systems for industrial use.
Date: May 1, 1996
Creator: Post, R.F. & Ryutov, D.
Partner: UNT Libraries Government Documents Department

Inductrack demonstration model

Description: A small-scale model track of a new type of magnetic levitation system (dubbed the ``Inductrack`` system), and a passively magnetically levitated cart, has been designed, constructed and operated. The track consists of a close-packed array of rectangular levitation coils, 15 centimeters in width transversely and 20 meters in length. The array of coils is inductively loaded above and below its lower horizontal section with ferrite tiles. Paralleling the levitation coils on each side are aluminum-channel rails on which ride auxiliary wheels attached to the cart. The cart has, on its lower surface and on its sides, fore and aft, special arrays (``Halbach arrays``) of permanent magnet bars that produce a strong periodic magnetic field below the cart. This magnetic field, when the cart is in motion, induces repelling currents in the Inductrack coils, levitating it and centering it transversely. When mechanically launched (with a pulley- and-weight system) at speeds substantially above a ``transition speed`` of about 2 meters per second, the cart levitated and flew stably down the track, settling to rest on its wheels near the end of the track. In the last phase of the program an electromagnetic launching section consisting of another array of coils, connected to pulse-driver circuits, was added at the beginning of the track. Aided by an initial launch (from stretched ``bungee`` cords), this electromagnetic launching system was operated successfully, resulting again in levitation and subsequent stable flight of the cart.
Date: February 3, 1998
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

The ''Kinetic Stabilizer'': A Simpler Tandem Mirror Confinement?

Description: In the search for better approaches to magnetic fusion it is important to keep in mind the lessons learned in the 50 years that fusion plasma confinement has been studied. One of the lessons learned is that ''closed'' and ''open'' fusion devices differ fundamentally with respect to an important property of their confinement, as follows: Without known exception closed systems such as the tokamak, the stellarator, or the reversed-field pinch, have been found to have their confinement times limited by non-classical, i.e., turbulence-related, processes, leading to the requirement that such systems must be scaled-up in dimensions to sizes much larger than would be the case in the absence of turbulence. By contrast, from the earliest days of fusion research, it has been demonstrated that open magnetic systems of the mirror variety can achieve confinement times close to that associated with classical, i.e., collisional, processes. While these good results have been obtained in both axially symmetric fields and in non-axisymmetric fields, the clearest cases have been those in which the confining fields are solenoidal and axially symmetric. These observations, i.e., of confinement not enhanced by turbulence, can be traced theoretically to such factors as the absence of parallel currents in the plasma, and to the constraints on particle drifts imposed by the adiabatic invariants governing particle confinement in axisymmetric open systems. In the past the MHD instability of axially symmetric open systems has been seen as a barrier to their use. However, theory predicts MHD-stable confinement is achievable if sufficient plasma is present in the ''good curvature'' regions outside the mirrors. This theory has been confirmed by experiments on the Gas Dynamic Trap mirror-based experiment at Novosibirsk, In this paper a new way of exploiting this stabilizing principle, involving creating a localized ''stabilizer plasma'' outside a mirror, will be discussed. To ...
Date: June 15, 2000
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

The Kinetic Stabilizer: Further Calculations and Options

Description: The Kinetic Stabilizer, employing injected and mirror-reflected ion beams, represents a method for stabilizing axisymmetric mirror and tandem mirror systems. Building on earlier work, this paper presents further calculations on the concept and explores some new options that promise to enhance its capabilities.
Date: June 19, 2002
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

The kinetic tandem concept: theory and computer simulations of the potential barriers

Description: The Kinetic Tandem fusion plasma confinement concept is a member of the class of open magnetic confinement systems whose magnetic topology is that of a tube of magnetic flux open at both ends. In open-ended systems the central problem is that of limiting the rate of plasma losses out the ends. In a conventional tandem mirror system end-plugging is accomplished by the generation of positive potential barriers within special short mirror cells located at each end of a long central confinement cell. The kinetic tandem concept accomplishes the same end result by employing dynamic effects, but without the necessity of special end cells. The field employed in the kinetic tandem is a simple axially symmetric solenoidal field whose intensity tapers to low values at the ends. Since the field line curvature is everywhere positive such a field is stabilizing for MHD interchange modes. Into each end are injected ion beams that are aimed nearly parallel to the field line direction. The ions from these beams then are radially compressed, stopped, and reflected back by magnetic mirror action in climbing up the magnetic gradient. In this way ion density peaks are formed between which the plasma is to be confined. As in the original tandem mirror concept, a localized ambipolar potential arises to maintain quasi-neutrality between the ions and the electrons. provided the plasma density in the plugs is higher than that of the plasma contained between them the ions of the central plasma will be confined between the plugs by the positive potential barriers represented by the plugs. The plasma electrons will at the same time be confined by the overall positive potential of the plasma with respect to the ends. In this report some analytical calculations of the formation of the plugs will be given. These calculations were then ...
Date: February 11, 1999
Creator: Byers, J A & Post, R F
Partner: UNT Libraries Government Documents Department