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This paper, part of a continuing study of means for the stabilization of magnetohydrodynamic interchange modes in axisymmetric mirror-based plasma confinement systems, represents a preliminary look at a technique that would employ a train of plasma pressure pulses produced by electron cyclotron resonance heating (ECRH) to accomplish the stabilization. The use of sequentially pulsed ECRH rather than continuous-wave ECRH facilitates the localization of the heated-electron plasma pulses in regions of the magnetic field with positive field-line curvature, e.g., in the “expander” region of the mirror magnetic field, outside the outermost mirror. The technique proposed relies on the time-averaged effect of plasma pressure pulses generated in regions of positive field-line curvature to overcome the destabilizing effect of plasma pressure in regions of negative field-line curvature within the confinement region. The plasma pulses, when produced in regions of the confining field having a negative gradient,...

An axisymmetric tandem mirror system should possess many advantages over conventional tandem-mirror systems. The Kinetic Stabilizer Tandem Mirror (k-S T-M) represents one possible way to MHD-stabilize such systems. However, to design such systems requires the simultaneous satisfaction of MHD stabilization conditions and the constraints of technological feasibility and acceptable power demands This paper reviews the basic requirements for a K-S T-M and discusses various technological approaches for meeting those requirements.

A novel means of MHD stabilizing axially symmetric mirror systems was proposed by Ryutov and demonstrated in the Gas Dynamic Trap at Novosibirsk. It relies on the strongly stabilizing effect exerted by low density plasma on the expanding field lines outside the mirrors. The “Kinetic Stabilizer Tandem Mirror” implements Ryutov’s technique by injecting axially directed ion beams into the expander. The ions, stagnated, and reflected by the converging magnetic field, form the stabilizing plasma. MHD stability code calculations show stabilization at beta values of 40%, with stabilizer beam powers that are small compared to the T-M fusion power output. Implicit in the calculations is the assumption that adequate “communication” exists between the plug plasmas and the stabilizer plasmas. This paper examines one means for enhancing communication: Utilize the stabilizer plasma to create a potential peak that, together with the plug potential, forms a potential well that traps and contains a “bridging” plasma.

The Fifth Symposium on Current Trends in International Fusion Research was held on 24–29 March 2003 in Washington, USA in co-operation with the International Atomic Energy Agency (IAEA). Well-known scientists in their field of interest in fusion research were invited to present review papers. The presentations covered a broad range of fusion topics, including inertial confinement fusion, electrostatic confinement, various magnetic confinement schemes, and hybrid schemes. Each session chairman composed a session report, which John Pucadyil used to create this Report on the Fifth Symposium.

The 'Kinetic Stabilizer' has been proposed as a means of MHD stabilizing an axisymmetric tandem mirror system. The K-S concept is based on theoretical studies by Ryutov, confirmed experimentally in the Gas Dynamic Trap experiment in Novosibirsk. In the K-S beams of ions are directed into the end of an 'expander' region outside the outer mirror of a tandem mirror. These ions, slowed, stagnated, and reflected as they move up the magnetic gradient, produce a low-density stabilizing plasma. At the Lawrence Livermore National Laboratory we have been conducting theoretical and computational studies of the K-S Tandem Mirror. These studies have employed a low-beta code written especially to analyze the beam injection/stabilization process, and a new code SYMTRAN (by Hua and Fowler) that solves the coupled radial and axial particle and energy transport in a K-S TM. Also, a 'legacy' MHD stability code, FLORA, has been upgraded and employed to benchmark the injection/stabilization code and to extend its results to high beta values. The FLORA code studies so far have confirmed the effectiveness of the K-S in stabilizing high-beta (40%) plasmas with stabilizer plasmas the peak pressures of which are several orders of magnitude smaller than those of the confined plasma.more » Also the SYMTRAN code has shown D-T plasma ignition from alpha particle energy deposition in T-M regimes with strong end plugging. Our studies have confirmed the viability of the K-S-T-M concept with respect to MHD stability and radial and axial confinement. We are continuing these studies in order to optimize the parameters and to examine means for the stabilization of possible residual instability modes, such as drift modes and 'trapped-particle' modes. These modes may in principle be controlled by tailoring the stabilizer plasma distribution and/or the radial potential distribution. In the paper the results to date of our studies are summarized and projected to scope out possible fusion-power versions of the K-S T-M« less

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.

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 learne...

Arising out of research at the Lawrence Livermore National Laboratory on passive magnetic bearings, a new magnetic levitation system, the Inductrack, has been developed and tested at model scale. The system employs special arrays of permanent magnets (Halbach arrays) on the moving car. The magnetic field from the arrays induces repelling currents in a close-packed array of shorted circuits in the track. Above a low transition speed (a few kilometers per hour), levitation forces approach a constant value, while drag forces decrease inversely with speed, with L/D reaching 200:1 or more at operating speeds. The high magnetic efficiency of the Halbach arrays, plus the use of close-packed track circuits, results in levitating forces approaching 40 metric tonnes per square meter (using NdFeB permanent magnet arrays, whose weight in typical cases is a few percent of the levitated weight). The system is passively stable: only motion is required for levitation. Failure of the drive system only results in the train slowing down and settling onto auxiliary wheels at a low speed. A detailed theoretical analysis of the Inductrack was made, on the basis of which a small-scale model was constructed and operated. The Laboratory is building a new small-scale model system (under NASA sponsorship) to demonstrate the acceleration rates and speeds (10-g and Mach 0.4 in the model) needed to magnetically launch rockets.

This Resource Letter is intended to introduce the reader to the history of fusion research, and to provide references covering the research since its first beginnings and up to the present for those who wish to dig deeper.

Although the maglev operating technology could produce smooth train rides at speeds up to 500 km per hour, no full scale operating maglev system has been built. The problems encountered, such as being much more expensive than conventional railways and as yet, not fail-safe, have limited the maglev application. A new design which uses no superconducting magnets or powered electromagnets is being developed. Named Inductrack, it uses permanent room-temperature magnets which are similar to bar magnets. In this concept, the underside of each train car has an Halbach array of magnetic bars which produce a very strong magnetic field. The track has closely packed coils of insulated wire and each coil is a closed circuit. The Inductrack produces levitating forces by inducing electric currents in the track. This article explores the theory of Inductrack and presents other possible uses for this new concept.

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. 16 refs., 2 figs.

In this paper, the special synergisms between open-ended magnetic confinement systems and the D-{sup 3}He fuel cycle are discussed, both in general terms and through examples. Properties of open systems that make them especially suited for this fuel cycle include their ability to stably confine high-beta plasmas, their compatibility with electrostatic direct converters, and their linear geometry, which can greatly simplify the practical attainment of high magnetic fields. The example systems given include a linear collider and thermal barrier tandem mirror systems for both terrestrial and space travel applications. It is concluded that satisfying the demanding physics requirements posed by the D-{sup 3}He fuel cycle may be more readily possible through the use of open-ended magnetic systems than it will be through the use of closed systems of the tokamak genre.

(1992). Summary of the First Wisconsin Symposium on D-3He Fusion, Madison, Wisconsin, August 21–22, 1990. Fusion Technology: Vol. 21, No. 4, pp. 2346-2348.

A line from a song in Rodgers and Hammerstein's "The Sound of Music" (with a slight change) encapsulates much of the essence of the now near half-century quest for fusion energy: "How do you hold a sunbeam in your hand?" Indeed, from its very beginning fusion research both captured the imagination of researchers and daunted them with its difficulty. More than 40 years later, fusion research finds itself in great peril and not for justifiable reasons. "The Sound of Music" has a happy ending after peril; fusion may not if present trends continue. The seeds of the fusion quest were planted by astrophysicists in the 1930s. They provided the explanation—nuclear fusion—for the seemingly inexhaustible source of heat radiated by the Sun and the stars. That understanding, coupled with the discernment of an essentially limitless source of fusion fuel on Earth—heavy hydrogen in the waters of the ocean—set the stage. Though the search was delayed ...

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.

Back-reflections from a target, lenses, etc. can gain energy passing backwards through a laser just like the main beam gains energy passing forwards. Unless something blocks these back-reflections early in their path, they can seriously damage the laser. A Mechanical Beam Isolator is a device that blocks back-reflections early, relatively inexpensively, and without introducing aberrations to the laser beam.

Magnetic confinement systems that use externally generated magnetic fields can be divided topologically into two classes:“closed”and“open”, The tokamak, the stellarator, and the reversed-field-pinch approaches are representatives of the first category, while mirror-based systems and their variants are of the second category. While the recent thrust of magnetic fusion research, with its emphasis on the tokamak, has been concentrated on closed geometry, there are significant reasons for the continued pursuit of research into open-ended systems. The paper discusses these reasons, reviews the history and the present status of open-ended systems, and suggests some future directions for the research.

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.

This report describes the design of a passive magnetic bearing system to be used in electromechanical batteries (flywheel energy storage modules) suitable for vehicular use. One or two such EMB modules might, for example, be employed in a hybrid-electric automobile, providing efficient means for power peaking, i.e., for handling acceleration and regenerative braking power demands at high power levels. The bearing design described herein will be based on a ''dual-mode'' operating regime.

As a bonus from an existing LDRD-supported project (Electromechanical Battery Research and Development) a new concept for the magnetic levitation of a moving object evolved. To initiate a study of the merits of the concept mid-year ``seed money`` LDRD funding was provided. The FY94 activities resulted in a preliminary evaluation of the merits of this concept through calculations, laboratory measurements, and the design of a simple test model. There is now considerable international interest in the ``Maglev`` concept for highspeed trains. Wear, rolling friction, and speed limitations of conventional rail technology make this technology unsuitable for such trains, whence the use of magnetic levitation. In present Maglev trains, however, such as those constructed in Germany and Japan, servo-controlled magnetic systems are required, involving sensor and control circuitry and non-trivial on-board power requirements. In such systems the failure of a control system can have serious consequences, so that redundant systems may be required, thus adding to the cost and complexity. It would be highly desirable to replace the present ``active``, servo-controlled magnetic levitation systems with a totally passive one, one for which neither control circuits nor on-board power would be required. Failure of such a system could be made to be much more benign in its consequences than for servo-controlled ones, and the cost, particularly of the on-board equipment, might be greatly reduced.

New materials and new design concepts are being incorporated in a new approach to an old idea -- flywheel energy storage -- to create 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. We visualize such EMBs (electromechanical batteries) as being modular in character, with small (1--5 kWh) modules being used for power-conditioning and for vehicular use, and paralleled 25 kWh modules being used for bulk storage, i.e., load-leveling, applications. In a funded program at the Laboratory two fractional kWh, 200 kW (design peak power) modules have been constructed and subjected to shake-down testing. Their design for high peak power was prompted by awareness of a particular commercial need, as a component in a power-line conditioning device. In addition to such stationary applications, the high power capability of our EMB designs makes them attractive for use in hybrid-electric vehicles. Important elements of the LLNL program include the development of passive magnetic bearings and the application of new high-efficiency permanent magnet arrays to an ironless generator/motor. Use of these particular elements, together with a multi-ring design for the flywheel rotor, is particularly conducive to amore » systemic approach to the design of an EMB module. These particular design developments have been motivated by the economic issues of simplification, lowered cost, and extended maintenance-free service life.« less

Numerical simulations and experimental studies have been made related to the possibility of employing an externally imposed electrostatic potential wave to separate isotopes. This wave/ion interaction is a sensitive function of the wave/ion difference velocity and for the appropriate wave amplitude and wave speed, a lighter faster isotope will be reflected by the wave to a higher energy while leaving heavier, slower isotopes virtually undisturbed in energy--allowing subsequent ion separation by simple energy discrimination. In these experiments, a set of some 200 individual electrodes, which surrounded a microamp beam of neon ions, was used to generate the wave. Measurements of the wave amplitudes needed for ion reflection and measurements of the final energies of those reflected ions are consistent with values expected from simple kinetic arguments and with the more detailed results of numeric simulations.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

An approximate theoretical analysis is given of a proposed technique for producing high transient electric fields within a mirror-confined hot-electron plasma. It is shown that exploitation of the ''loss-cone'' nature of the distribution function of the confined electrons, together with ion inertial effects and the plasma quasi-neutrality constraint, leads to a degree of control over the space-charge potentials that may permit application of the concept to high-energy particle accelerators.

Some of the long-range implications and advantages of achieving the production of power from controlled fusion reactions between isotopes of hydrogen, helium, and lithium are set forth. The physical conditions which seemingly must be established to accomplish this are presented. These are shown to lead to a situation in which the fusion fuel will exist in the form of a very hot, tenuous, fully ionized gas-i.e., a plasma. It is shown that the required conditions can be maintained only by the use of a force field, for example, a magnetic field, to confine the plasma. A simple example of magnetic confinement?the pinch effect?is described. The electrodynamic properties of a fully ionized gas interacting with a magnetic field are briefly outlined. General scaling laws which would probably apply to any operable controlled fusion reactor are given. Examples are cited of fruitless approaches to the achievement of controlled fusion. Some aspects of the problem of "plasma diagnostics" are described to illustrate means for an experimental approach to high temperature plasma physics.

Some of the long-range implications and advantages of achieving the production of power from controlled fusion reactions between isotopes of hydrogen, helium, and lithium are set forth. The physical conditions which seemingly must be established to accomplish this are presented. These are shown to lead to a situation in which the fusion fuel will exist in the form of a very hot, tenuous, fully ionized gas-i.e., a plasma. It is shown that the required conditions can be maintained only by the use of a force field, for example, a magnetic field, to confine the plasma. A simple example of magnetic confinement?the pinch effect?is described. The electrodynamic properties of a fully ionized gas interacting with a magnetic field are briefly outlined. General scaling laws which would probably apply to any operable controlled fusion reactor are given. Examples are cited of fruitless approaches to the achievement of controlled fusion. Some aspects of the problem of "plasma diagnostics" are described to illustrate means for an experimental approach to high temperature plasma physics.

The quest for fusion power began some forty years ago, with the discovery of nuclear fusion reactions, followed by the theory of thermonuclear processes, which successfully explained the source of the energy of the Sun and stars. But then, apart from the musings of a perceptive few, nearly twenty years passed before heightened interest in nuclear energy sources stimulated a serious attack on the problem. By this time both the potentialities of fusion and the growing need for energy from other than fossil‐fuel sources had become apparent. Here I shall try to evaluate the present state of research on controlled thermonuclear reactions in the context of the urgent need for developing new, environmentally acceptable, energy sources.

This report was prepared in late 1965 at the request of the U.S. House-Senate Joint Committee on Atomic Energy (JCAE) to review its program on controlled thermonuclear research (CTR), now called just “fusion energy research.” It was transmitted to them on June 11, 1966 by then chairman of the U.S. Atomic Energy Commission (AEC) Glenn T. Seaborg. The AEC is the predecessor agency of the current U.S. Department of Energy (DOE). The report has previously only been available as AEC report TID-23277. This version of the report is complete except for the omission of lengthy discussions of the then current fusion research activities at various AEC sites. This paper includes, as does the original report, a copy of Seaborg’s June 11, 1966 transmittal letter and, as appendices, copies of a 1962 review of the fusion program by the AEC’s General Advisory Committee (GAC), a review of the Policy Paper by a special 1965 AEC committee, prior to its submittal to the JCAE, comments on the report by the GAC and the President’s Science Advisory Committee, and the charter for then newly established CTR Standing Committee.

In the fields of controlled fusion research and high-energy nuclear physics it is becoming evident that means for the efficient generation of very high magnetic fields must be sought. Since ferromagnetic materials are of no help at the required fields of 105 gauss, one can only rely on the use of air core coils, so that the fields which can be reached depend only on the ampere-turns achievable and simple geometrical factors. In this case the limitations on attainable fields usually come down to a question of available electrical power, or, more fundamentally, to limitations imposed by heating of the coil conductors and problems of heat transfer within the coil. For laboratory — sized magnets, the limit is reached in magnets such as the Bitter magnet, where the ultimate limit is nearly reached in power density and heat transfer while achieving steady fields of 105 gauss in volumes of the order of 1 liter.

The attenuation of (319\ifmmode\pm\else\textpm\fi{}4)-Mev photons in liquid hydrocarbons has been measured and has been used to infer the cross section for pair production in the field of the orbital electrons (triplet production).Targets of benzene (${\mathrm{C}}_{6}$${\mathrm{H}}_{6}$) and cyclohexane (${\mathrm{C}}_{6}$${\mathrm{H}}_{12}$) were used in good geometry. A pair spectrometer with three fast counter channels was used to measure the intensity of the transmitted photon beam. The synchrotron was monitored with a modified pair spectrometer that was sensitive only to the bremsstrahlung spectrum above 300 Mev.The total absorption cross sections in hydrogen and carbon at 319 Mev have been found to be 18.0\ifmmode\pm\else\textpm\fi{}1.8 mb per hydrogen atom, and 321.1\ifmmode\pm\else\textpm\fi{}2.8 mb per carbon atom, respectively.Subtraction of the theoretical nuclear pair and electron Compton cross sections and the experimental photomeson cross sections in hydrogen from the total hydrogen absorption cross section gives 6.8\ifmmode\pm\else\textpm\fi{}1.8 mb for the experimental triplet cross section, as compared with the theoretical value of 7.68 mb. Similarly, when one subtracts the cross sections for competing processes in carbon, one gets for the triplet cross section at 319 Mev the value 46.6\ifmmode\pm\else\textpm\fi{}6.4 mb, compared with the theoretical value of 44.4 mb. The large uncertainty in the carbon triplet cross section is due to uncertainties in the cross sections for the competing processes.

The correlation and theoretical analysis of a large number of transmission measurements made in the Potomac River and Chesapeake Bay areas warrants the conclusions which follow. Given a source of audiofrequency sound in water, the sound pressure level which may be measured at appreciable distances will be influenced in a complicated way by the boundaries, especially by the bottom. The sea bottom may be classified by its behavior for sound as “soft,” “hard,” or intermediate in character. Specifically, the velocity of sound and the density of the bottom may be estimated from acoustic measurements (hydrophone soundings and range runs), by sampling, and from hydrographic data. The effect of the boundaries on sound propagation from a ship‐mounted source may be determined from an analysis of the normal modes of vibration of the acoustic system of the sea between surface and bottom. The analysis is particularly effective for frequencies at which the wave‐lengths are comparable to the physical dimensions of the s...

A plasma confined in a mirror machine can be expected to develop an electrostatic potential with respect to its surroundings. This potential arises because of the intrinsically different rate of diffusion in velocity space of the electrons and ions. When the temperature of the confined electrons is comparable to or smaller than the ion temperature, the potential will be positive, and will vary within the plasma. The variation of plasma potential with position in a mirror machine is calculated for conditions where: (a) the electron temperature is small compared to ion temperature and (b) electrons and ions are separately in diffusion equilibrium with the mirror losses. It is shown in an example that the plasma potential tends to concentrate near the mirrors, and that its variation, between the mirrors, is relatively insensitive to the total potential. Applications and extensions of the calculations are suggested.

Three classes of electrostatic instabilities deemed likely to be encountered in magnetic mirror‐confined plasmas are examined theoretically: (A) a convective type, maser‐like in nature, with waves propagating essentially parallel to the field lines; (B) a nonconvective (absolute) instability, arising in the presence of radial density gradients; and (C) a limiting case of (B), not requiring radial density gradients for its stimulation. All three instabilities, which owe their origin to the loss‐cone nature of the particle distributions, exhibit critical conditions for onset or growth that are sensitively dependent on the shape of the distribution functions. These conditions are least restrictive for plasmas that have reached a state of collisional equilibrium in confining fields of high mirror ratio. In this limit (C) disappears and the critical conditions imposed by (A) and (B) are not unduly restrictive. In particular, at high plasma densities it is required: (1) for adequate stability against (A), the length of the plasma between the mirrors must not be greater than about 300 to 500 ion‐orbit radii, and (2) to satisfy conditions (on the radial density gradient) imposed by (B), the plasma dimensions transverse to the field must also be of the same order; i.e., the plasma must be roughly spherical. Examples are also given which show that the confinement of highly peaked distributions leads to required conditions of orders of magnitude more restrictive than those found for well‐randomized distributions.

In a pulsed experiment a magnetically guided plasma stream is reflected by a double electrode structure. Space‐charge‐limited densities up to 4×1011 cm−3 are calculated and verified. An application to stopper one end of a mirror fusion reactor is discussed.