Magnetic Confinement Fusion Research Papers (original) (raw)

Transport is the outstanding physics issue in the quest for fusion by magnetic confinement. In spite of the intrinsic difficulty, a great deal of progress has been made in the past 25 years. Experiments have gone from being dominated by high anomalous losses, of the order of Bohm diffusion losses, to operation with no anomalous transport. This success is due to a combination of improved experimental infrastructure and the high degree of knowledge on how to control plasma discharges. Both have made it possible to access enhanced confinement regimes and to unravel new effects in confinement physics. Although there is not yet a complete understanding of the dynamical mechanisms underlying the anomalous transport process, there is some understanding of important components such as the ion transport loss mechanism at the plasma core and of the main mechanism for turbulence suppression in the enhanced confinement regimes.

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- Physics, Fusion, Magnetic Confinement Fusion, Heating

Time-dependent integrated predictive modelling is carried out using the PTRANSP code to predict fusion power and parameters such as alpha particle density and pressure in ITER H-mode plasmas. Auxiliary heating by negative ion neutral beam injection and ion-cyclotron heating of He 3 minority ions are modelled, and the GLF23 transport model is used in the prediction of the evolution of plasma temperature profiles. Effects of beam steering, beam torque, plasma rotation, beam current drive, pedestal temperatures, sawtooth oscillations, magnetic diffusion and accumulation of He ash are treated self-consistently. Variations in assumptions associated with physics uncertainties for standard base-line DT H-mode plasmas (with I p = 15 MA, B TF = 5.3 T and Greenwald fraction = 0.86) lead to a range of predictions for DT fusion power P DT and quasi-steady state fusion Q DT (≡P DT /P aux ). Typical predictions assuming P aux = 50-53 MW yield P DT = 250-720 MW and Q DT = 5-14. In some cases where P aux is ramped down or shut off after initial flat-top conditions, quasi-steady Q DT can be considerably higher, even infinite. Adverse physics assumptions such as the existence of an inward pinch of the helium ash and an ash recycling coefficient approaching unity lead to very low values for P DT . Alternative scenarios with different heating and reduced performance regimes are also considered including plasmas with only H or D isotopes, DT plasmas with toroidal field reduced 10% or 20% and discharges with reduced beam voltage. In full-performance D-only discharges, tritium burn up is predicted to generate central tritium densities up to 10 16 m −3 and DT neutron rates up to 5 × 10 16 s −1 , compared with the DD neutron rates of 6 × 10 17 s −1 . Predictions with the toroidal field reduced 10% or 20% below the planned 5.3 T and keeping the same q 98 , Greenwald fraction and β n indicate that the fusion yield P DT and Q DT will be lower by about a factor of two (scaling as B 3.5 ).

- by Robert Budny
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- Plasma Physics, Numerical Simulation, Computer Simulation, Nuclear Fusion

In this paper, we present a semi-analytic full-vector method for calculating the spatial profile, optical confinement factor, resonant frequency, absorption loss, and mirror loss of lasing modes in cylindrically symmetric microcavity verticalcavity surface-emitting lasers (VCSEL's). It can be shown that this method gives the best separable approximation for the electric and magnetic vector potentials. Our technique can model the entire VCSEL structure and can treat complex media. We apply the method to etched-post and oxide-apertured VCSEL's designed for 980-nm emission and find a blueshift in cavity resonance as the cavity radius shrinks. We also find a minimum optical cavity radius below which radially bound lasing modes cannot be supported. This radius depends on the device geometry and lies between 0.5 and 1 m for the devices studied. Once this model is augmented to include diffraction losses-the dominant loss mechanism for conventional small aperture lasers-it will provide a complete picture of lasing eigenmodes in microcavity VCSEL's.

This review surveys the present state of the art of diagnostics and removal techniques for particles suspended in plasma. Research on "Dusty Plasmas" is necessary for ITER and the fusion reactors of the future. The aim is to transfer the knowledge acquired in complex (dusty) plasma research and in the low temperature plasma community to the broad fusion community, which is being mobilized to understand/quantify this phenomenon and find solutions. The introductory style makes it accessible also to safety personnel and other interested readers with only basic knowledge of plasma. In the transfer from research to technology we have tried to assess the applicability of the methods proposed and we have identified further, much needed, R&D.

- by Gregor Morfill
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- Dusty Plasma, Safety, Magnetic Confinement Fusion, Cold Plasma

Several permanent-magnet structures for whole-body nuclear magnetlc resonance diagnostics are described and compared. All provide a field of 1 . 5 kOe over wurkin volumes of about 0.9 m3 without the use of e H ectrical solenoids or bulky puwer su plies. A previously pro osed ferrite mudel now we$s more than 11 tons. by using rnpre unorth ox configurations employin rare earth permanent magnets, the same per P orrnance can be attained with as little as 3.6 tons of material.

- by Anthony Busigin
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- Diffusion, Magnetic Confinement Fusion, Tritium

To realize continuous-wave (CW) operation of millimeter-wave gyrotrons at megawatt (MW)-power levels, these devices must operate in very high-order modes. To excite such an operating mode and to drive it into the regime of MW-level operation with high efficiency requires careful consideration of the startup scenario through which the operating parameters of the device are brought to their nominal values. In the present paper, several common startup scenarios and the most important physical effects associated with them are discussed. Then, the paper presents the results of startup simulations for a 140-GHz, MW-class gyrotron developed by Communications and Power Industries (CPI) for electron-cyclotron plasma heating and current drive experiments on the "Wendelstein 7-X" stellarator. The simulations were done with MAGY, a multifrequency, self-consistent code developed at the University of Maryland. Simulations tracking six competing modes show that, with a proper choice of operating parameters, stable excitation of the desired TE 28 7 -mode at 1 MW level can be realized, despite the presence of dangerous parasites in the resonator spectrum. These results are in approximate agreement with experimental tests, in which the gyrotron demonstrated reliable operation at power levels up to 900 kW. PACS numbers: 84.40.Ik, 52.75 Ms.

- by Gregory Nusinovich
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- Resonators, Millimeter Wave Antennas, Magnetic Confinement Fusion, Spectrum

Helicon waves are right-hand polarized (RHP) waves which propagate in radially confined magnetized plasmas for frequencies ωci ≪ω≪ωce where ωci is the ion cyclotron frequency and ωce is the electron cyclotron frequency. They are part of a much larger family of waves which can propagate down to zero frequency and constitute a very rich field for studying complex propagation characteristics and wave-particle interactions. This paper gives a historical perspective of the waves and their relationship to plasma source development up to the mid 1980s, presents a simple description of their propagation characteristics in free and bounded plasmas, and finishes with their first reported use in plasma processing experiments

- by Francis F. Chen
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- History, Plasma Processing, Frequency, Polarization
- by Anthony Busigin
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- Diffusion, Magnetic Confinement Fusion, Tritium

The study of core turbulence represents a key line of research in fusion plasmas. By adding collisions and electromagnetic induction to the parallel dynamics of the standard six-moment toroidal model, it is possible to study the gyrofluid electromagnetic phenomena in the context of edge turbulence with the GEM code. Currently, the code describes the fluctuation free-energy conservation in a gyrofluid model by means of the polarization equation which relates the ExB flow and eddy energy to the combinations of the potential, the density, and the perpendicular temperature. To do so, supercomputers have been used only to date. In this paper, we demonstrate its feasibility as a cluster application on a production environment based on any kind of distributed memory, enhancing in this way its scope. The scalability (which grows linearly with a correlation factor of 0.99978) and the correctness of our solution with respect to the previous GEM version have been evaluated in a local cluster of 88 nodes. The fault tolerance and the Grid suitability have been demonstrated by executing our application in the EUrope Fusion for ITER Applications infrastructure by adapting the code to this paradigm and by improving its parallel Grid performance. It can be employed on its own or belonging to workflows in order to perform a wider more complex analysis of fusion reactors.

This paper presents a method for compensating for nonunifonnity of magnetization in a yokeless permanent magnet designed for clinical applications of nuclear magnetic resonance (NMR). The field generated by the magnet is confined within the magnetic material without the use of an external yoke. The method involves two steps: compensation in the individual magnet components and shiiruning of the assembled magnet. This paper discusses the first step, and, in particular, the compensation of the lowest hannonics of the field.

- by Ernest Potenziani
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- Engineering, Nuclear Magnetic Resonance, Magnetic Materials, Assembly
- by Marina Vroubel
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- Engineering, Magnetic thin film, Magnetic field, Anisotropy

Fusion alpha parameters are calculated for tokamaks with high DT fusion rates using the TRANSP plasma analysis code. Parameters include the fast alpha density n α , fast alpha pressure normalized to magnetic field energy β α , and its normalized gradient −R × ∇(β α ). The plasma conditions are taken from the plasmas in TFTR and JET with the highest DT fusion rates, and from plasmas in the proposed IGNITOR, FIRE, and ITER-FEAT tokamaks.

- by Robert Budny
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- Monte Carlo Methods, Magnetic field, Nuclear Fusion, Plasma

The U.S.-ITER DCLL (Dual Coolant Liquid Lead) TBM (Test Blanket Module) uses a Flow Channel Insert (FCI), to test the feasibility of high temperature DCLL concepts for future power reactors. The FCI serves a dual function of electrical insulation, to mitigate MHD effects, and thermal insulation to keep steel-PbLi interface temperatures below allowable limits. As a nonstructural component, the key performance requirements of the FCI structure are compatibility with PbLi, longterm radiation damage resistance, maintaining insulating properties over the lifetime, adequate insulation even in case of localized failures, and manufacturability. The main loads on the FCI are thermally induced due to through the thickness temperature gradients and due to non-uniform PbLi temperatures along the flow channel (~1.6 m). A number of SiC-based materials are being developed for FCI applications, including SiC/SiC composites and porous SiC bonded between CVD SiC face sheets. Here, we report on an FCI design based on open-cell SiC-foam material. Thermo-mechanical analysis of this FCI concept indicate that a SiC-foam FCI structure is capable of withstanding anticipated primary and secondary stresses during operation in an ITER TBM environment. A complete 30 cm long prototypical segment of the FCI structure was designed and is being fabricated, demonstrating the SiC-foam based FCI structure to be very low-cost and viability candidate for an ITER TBM FCI structure.

- by Robert Shaefer
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- Design, Performance, Conception, CVD
- by Richard York
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- Materials Science, Magnetic field, Geometry, Computer Model
- by alberto coletti
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- Electromagnetics, Magnetic field, Conceptual Design, Magnetic Confinement Fusion

Neutron irradiation damage in terms of displacement and transmutant production, is assessed in inertial (ICF) and magnetic (MCF) confinement fusion reactors, for the reduced activation martensitic steel, B-TAHF. These results, along with current experimental and theoretical information available on ferritic/martensitic steels, have been used to infer irradiation responses, such as swelling and ductile to brittle transition temperature (DBTT). The ICF approach can lead to concepts with a first structural wall (FSW) able to last the power plant's entire lifetime. In MCF, the material at end of life does not fulfill the technological requirements. Damage calculations have also been carried out in the HFIR and the FFTF reactors, for purposes of planning and assessing irradiation experiments in fission reactors in the light of fusion reactor needs. Fission irradiations can be very useful for assessing ICF reactor materials, but appear to have little engineering relevance for MCF commercial applications.

Summary form only given. Dielectric Cherenkov maser with a plasma column, an axial dielectric rod and a thin annular relativistic electron beam (TAREB) is studied in the presence of external magnetic field. The dispersion equations of the beam-wave interaction are derived. The growth rates of the wave are obtained, and the effects of the accelerating voltage, beam current and the background plasma density on the growth rate of the wave are numerically calculated and discussed. Also results are numerically compared with pervious work. We concluded that, by placing a dielectric rod in the axes of waveguide, the growth rate increases.

- by hamid ghomi
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- Masers, Magnetic field, Classical Physics, Dielectrics

Nonlinear gyrokinetic simulations have been conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal E × B shear value for plasma confinement. Local maxima in the momentum fluxes are also observed, allowing for the possibility of bifurcations in the E × B shear. The sensitive dependence of heat flux on temperature gradient is relaxed for large flow shear values, with the critical temperature gradient increasing at lower flow shear values. The turbulent Prandtl number is found to be largely independent of temperature and flow gradients, with a value close to unity.

- by Michael Barnes
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- Plasma Physics, Turbulence, Magnetic Confinement Fusion

The role of the magnetic field in the confinement or compression of interstellar gas clouds is reconsidered. The virial theorem for an isolated magnetized cloud in the presence of distant magnetic sources is reformulated in terms of moments of the internal and external currents, and an equilibrium condition is derived. This condition is applied to the interaction between isolated clouds for the simple-and artificial-case in which the field of each cloud is a dipole. With the simplest of statistical assumptions, the probability of any given cloud being compressed is calculated as ~ 10~, the magnetic field acting as a medium which transmits the kinetic pressure between clouds. Even when compression occurs the magnetic pressure 89 2 may decrease on leaving the cloud surface. * Paper dedicated to Professor Hannes Alfv6n on the occasion of his 80th birthday, 30 May 1988.

- by michel azar
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- Kinetics, Magnetic field, Molecular Clouds, Gravitational Collapse

Measurements of the angular flux distribution of the cathodic arc plasma (I < 100 A) subjected to a transverse magnetic field (B < 8.5 X 10-2 T) ae presented. The angular distribution without magnetic field approximately follows the cosine law. Expansion with transverse field is found to deviate strongly from the cosine law, the plasma being confined close to the cathode plane and expanding along the magnetic-field lines. Furthermore, time-resolved photographs of the expansion reveal the predicted pulsating behavior of the expanding plasma.

- by Jeanluc Meunier
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- Magnetic field, Time Resolved, Magnetic Confinement Fusion, Magnetic Fields

We describe the decoherence-free subspace of N atoms in a cavity, in which decoherence due to the leakage of photons through the cavity mirrors is suppressed. We show how the states of the subspace can be entangled with the help of weak laser pulses, using the high decay rate of the cavity field and strong coupling between the atoms and the resonator mode. The atoms remain decoherence-free with a probability which can, in principle, be arbitrarily close to unity.

The Wendelstein 7-X (W7-X) optimized stellarator is presently under construction at the Max-Planck-Institut für Plasmaphysik in Greifswald. The goal of W7-X is to verify that the advanced stellarator magnetic confinement concept is a viable option for a fusion reactor. The W7-X coil system consisting of 70 superconducting coils of seven different types is supported by a massive central support structure (CSS), and thermally protected by the cryostat. The magnet system's weight is borne by supports (cryo-legs) which are bolted to the cold CSS. They reach down through the cryostat wall to the warm machine base which means that a small thermal conductivity is important to keep thermal losses at an acceptable level. Therefore, the design of the cryo-legs incorporates glass-reinforced plastic (GRP) tubes which are shrink-fitted into stainless steel flanges at the ends. In order to ensure free thermal shrinkage of the magnet system and to reduce stresses in the cryo-legs, sliding and rotating bearings are used as interfaces to the machine base. Tie rods between the machine base and the warm ends of the cryo-legs prevent toroidal movements of the magnet system with respect to the torus axis. Nevertheless, significant deformation of the CSS during operation results in tilting of the cryo-legs in such a way that toroidal movements of the whole magnet system take place. The number of cryo-legs and their stiffness are chosen such that the toroidal movement is kept within an acceptable range. All these restrictions, as well as requirements concerning simplicity and ease of assembly, make the cryo-leg design and structural analysis quite a complex and challenging task. The paper presents an overview of structural analyses of the W7-X magnet system with cryo-legs, local analyses of a cryo-leg under design loads, and FE simulation of the cryo-leg mechanical test.

The effect of the strong external magnetic field is studied on the dielectric Cherenkov maser, which is included with an axial thin annular relativistic electron beam and a plasma column in a dielectric lined slow-wave waveguide. The dispersion equations of the beam-wave interaction are derived. The growth rates of the wave are obtained, and the effects of the accelerating voltage, beam current and the background plasma density on the growth rate of the wave are numerically calculated, discussed, and compared in the presence and absence of external magnetic field.

- by hamid ghomi
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- Masers, Magnetic field, Classical Physics, Dielectrics

The nonlinear dynamics of a single ion in a field reversed configuration (FRC) were investigated. FRC is a toroidal fusion device which uses a specific type of magnetic field to confine ions. As a result of angular invariance, the full three-dimensional Hamiltonian system can be expressed as two coupled, highly nonlinear oscillators. Due to the high nonlinearity in the equations of motion, the behavior of the system is extremely complex, showing different regimes, depending on the values of the conserved canonical angular momentum and the geometry of the fusion vessel. Perturbation theory and averaging were used to derive an integrable Hamiltonian and frequencies of the two degrees of freedom. The derived equations were then used to find resonances and compare to Poincare surface-of-section plots. A regime was found where the nonlinear resonances were clearly separated by KAM curves. The structure of the observed island chains was explained. The condition for the destruction of KAM curves and the onset of strong chaos was derived, using Chirikov island overlap criterion, and shown qualitatively to depend both on the canonical angular momentum and geometry of the device. After a brief discussion of the adiabatic regime, the paper goes on to explore the degenerate regime that sets in at higher values of angular momenta. In this regime, the unperturbed Hamiltonian can be approximated as two uncoupled linear oscillators. In this case, the system is near-integrable, except in cases of a universal resonance, which results in large island structures, due to the smallness of nonlinear terms, which bound the resonance. The linear force constants, dominant in this regime, were derived and the geometry for a large one-to-one resonance identified. The above analysis showed good agreement with numerical simulations and was able to explain characteristic features of the dynamics.

- by Mark Edelman
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- Applied Mathematics, Plasma Physics, Nonlinear dynamics, Magnetic field

Reliable and accurate estimates of the ion effective charge Z eff in tokamak plasmas are of key importance with respect to impurity transport studies and the establishment of thermonuclear burn criteria. These issues are of fundamental interest to ITER and reactor operational scenarios in general. However, Z eff estimates derived from bremsstrahlung spectroscopy on the one hand and from the weighted summation of individual impurity concentrations obtained via Charge Exchange Spectroscopy (CXS) on the other hand, often are not compatible. This is a long-standing problem in fusion plasma diagnosis. A rigorous analysis of uncertainty sources and their propagation in the experimental determination of Z eff can contribute significantly to the derivation of a Z eff value with reduced uncertainty that is consistent with both the bremsstrahlung and CXS data sets. In the present work, Bayesian Probability Theory is used in an integrated approach as a powerful tool for an advanced error analysis in the derivation of Z eff , even in the presence of systematic errors on the data. A simple probabilistic model is proposed for the estimation of Z eff , first assuming only statistical uncertainty, next taking into account also systematic deviations. The obtained Z eff estimates have smaller error bars than the Z eff values derived from the individual bremsstrahlung and CXS measurements, approaching ITER requirements. The estimates are shown to be consistent with all available information. In addition, systematic errors on the data are quantized through the requirement of data consistency between different time slices in the acquired measurements.

- by Geert Verdoolaege
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- Data Analysis, Bremsstrahlung, Probabilistic Model Checking, Error Analysis
- by Richard york
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- Physics, Materials Science, Magnetic field, Cyclotron

General Fusion is a 65-employee private company developing fusion energy with $40M of capital to date. This report will describe General Fusion's design for an acoustically driven Magnetized Target Fusion (MTF) reactor concept. The advantages of this particular MTF scheme will be discussed. Our experimental and numerical work and results so far will be presented, as well as plans for future development Keywords-Magnetized Target Fusion; I.

- by Stephen Howard
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- Acoustics, Magnetic Confinement Fusion, Fusion Energy

The design of a new type of storage ring (synchrotron) for heavy ions using electrostatic deflection and focusing devices is described. Such a storage ring will be attractive for many atomic-physics experiments, and also for basic... more

- by Søren Møller
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- Physics, Atomic Physics, Magnetic field, Synchrotron

In laser-plasma interaction experiments there are a variety of effects which will scatter or deflect a probing electron beam. For example, a longitudinally probing electron beam is defocused by the ponderomotive force of a laser, but in a plasma the laser can set up fields which actually confine the electron beam. In the cases of plasma wave excitation via the

- by Chan Joshi
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- Magnetic field, Experimental Study, Magnetic Confinement Fusion, Scattering

In the concept known as Magnetized Target Fusion (MTF) in the United States and Magnitnoye Obzhatiye (MAGO) in Russia, a preheated and magnetized target plasma is hydrodynamically compressed to fusion conditions. Because the magnetic field suppresses losses by electron thermal conduction in the fuel during the target implosion heating process, the implosion velocity may be much smaller than in traditional inertial confinement fusion. Hence "liner-on-plasma" compressions, magnetically driven using relatively inexpensive electrical pulsed power, may be practical. The relatively dense, hot target plasma, with starting conditions O(lO'* cmJ, 100 eV, 100 kG), may spend 10 or more microseconds in contact with a metal wall during formation and compression. Influx of a significant amount of high-Z wall material during this time could lead to excessive cooling by dilution and radiation that would prevent the desired near-adiabatic compression heating of the plasma to fusion conditions. Magnetohydrodynamic (MHD) calculations including detailed effects of radiation, heat conduction, and resistive field diffusion are being done, using several different computer codes, to investigate such plasma-wall interaction issues in ongoing MTF target plasma experiments and in proposed liner-on-plasma MTF experiments.

- by Rickey Faehl
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- Magnetohydrodynamics, Radiation, Magnetic field, United States

A semiconductor optical amplifier was developed for coarse wavelength-division-multiplexing (CWDM) operating over 1540-1620 nm (-band). A unique quantum-well structure was designed to meet the requirements for the CWDM operation such as wide bandwidth, low polarization-dependent gain, and high-saturation power at the short wavelength end of the band (1540 nm). Over the band, 24-dB maximum chip gain was obtained with less than 4.3-dB gain flatness and more than 14.6-dBm saturation power.

A number of experiments have attempted, with varying degrees of success, to influence the low to high confinement mode (L-H) transition through the application of an external flow shear forcing mechanism. In order to theoretically describe this type of experiment, an external torque is included in the phase transition model of Diamond et al. [Phys. Rev. Lett. 72, 2965 (1994)] for the L-H bifurcation. These equations exhibit a bifurcation between an L-mode fixed point and an H-mode fixed point with variation of a critical parameter, corresponding to the edge gradient, across a threshold value. With the addition of the external torque [from biased limiter, probe, or radio frequency (t-f) wave], the character of the transition changes in a manner analogous to the addition of an external magnetic field to a ferromagnetic material. In addition to the change in the transition dynamics, there is a marked decrease in the threshold level. In this simpIe model, the decrease in threshold level is proportional to the applied torque to the two-thirds power, in approximate functional agreement with that seen by some experiments. 0 199.5 American Institute of Physics.

- by B. Carreras
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- Plasma Physics, Turbulence, Magnetic field, Classical Physics

Abstract - The reproducible preparation of homogeneous iron oxide nanoparticles with particle size diameters less than 5 nm and rsd as low as 17% by a novel flow-injection synthesis is described. The particles were directly coated with a... more

- by German Salazar-Alvarez
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- Biomagnetism, Nanoparticles, Nanotechnology, Thermochemistry

The Caltech spheromak experiment uses a size A ignitron in switching a 59-µF capacitor bank (charged up to 8 kV) across an inductive plasma load. Typical power levels in the discharge circuit are ∼200 MW for a duration of ∼10 µs. This paper describes the setup of the circuit and the measurements of various impedances in the circuit. The combined impedance of the size A ignitron and the cables was found to be significantly larger than the plasma impedance. This causes the circuit to behave like a current source with low energy transfer efficiency. This behavior is expected to be common with other pulsed plasma experiments of similar size that employ an ignitron switch.

- by Deepak Kumar
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- Energy efficiency, Impedance, Magnetic Confinement Fusion, Energy efficient
- by ahmed abdelrahman
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- Bose Einstein Condensation, Symmetry, Band Gap, Magnetic separation

In magnetic confinement fusion, the operation of next generation devices will be significantly different compared to present day machines. The duration length of the discharges will require abandoning the traditional paradigm of processing and storing the data after the shot. In fact most information will have to be made available in real-time. The significant issues of machine protection will require more sophisticated and at the same time more robust feedback control schemes. Another very important issue emerged in the last years of JET operation, and which is expected to become more severe in ITER, is the large amount of data to be analysed, which cannot be handled in the most efficient way with traditional methods.

- by Jesus Vega
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- Mechanical Engineering, Information Retrieval, Signal Processing, Data acquisition

- by Jesus Vega
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- Mechanical Engineering, Information Retrieval, Signal Processing, Data acquisition
- by Muralidhar Yeddulla
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- Physics, Resonators, Millimeter Wave Antennas, Magnetic Confinement Fusion

The Brillouin flow equilibrium in magnetically insulated lines is a state in which field-emitted electrons, confined to a sheath near the cathode by a magnetic field, drift laminarly at the 1 X B velocity in the self-consistent fields of the anode-cathode gap. Herein, this state is perturbed by a TM disturbance traveling along the direction of electron flow. Asymptotic expansions of all quantities of interest in some small parameter are performed in the long wavelength limit. First order quantities are seen to be governed by the Korteweg-deVries' equation, which admits soliton solutions. In the appropriate limits of either infinite wavelength or vanishingly small amplitude, the results contained herein are seen to agree with other analyses, based, respectively, upon either the nondispersive telegraphers' equations or a linearized analysis.

- by John Swegle
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- Physics, Magnetic field, Geometry, Solitons

The thermonuclear fusion is realised by a main technique of magnetic confinement of the plasma fusion. This reaction has for object if the production of energy. After many researches, the scientists have found that the most promoter configuration is the Tokamak machine which permits this reaction of fusion in similar conditions to the one of reactions in the sun.

- by naima sabri
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- Energy, Tokamak, Plasma, Magnetic Confinement Fusion
- by C. Hegna
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- Physics, Plasma Physics, Magnetohydrodynamics, Stability

In this paper, we demonstrate the importance of the details of the equilibria on the stability of electron drift waves. A comparison of electrostatic electron drift waves in numerical and analytical tokamak equilibria is presented in fully three-dimensional circular and non-circular tokamaks. The numerical equilibria are obtained using the variational moments equilibrium code and the analytical equilibria used is the generalizedŝ-α model. An eigenvalue equation for the model is derived using the ballooning mode formalism and solved numerically using a standard shooting technique. The stability and the localization of the electron drift wave is found to be strongly dependent on the local shear of the magnetic field. Large values of the local shear are found to be stabilizing. A disagreement in the results is found between analytical and numerical equilibria at aspect ratios of typical tokamaks, suggesting that the latter approach should be used in the transport calculations. The effects of the local shaping of the magnetic surfaces are complicated and can be both stabilizing and destabilizing, depending on the details of the equilibria.

- by T. Rafiq
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- Physics, Plasma Physics, Magnetic field, Fusion

It has been hypothesized that the sustained narrowness observed in the asymptotic cylindrical region of bipolar outflows from Young Stellar Objects (YSO) indicates that these jets are magnetically collimated. The φ B j z × force observed in z-pinch plasmas is a possible explanation for these observations. However, z-pinch plasmas are subject to current driven instabilities (CDI). The interest in using z-pinches for controlled nuclear fusion has lead to an extensive theory of the stability of magnetically confined plasmas. Analytical, numerical, and experimental evidence from this field suggest that sheared flow in magnetized plasmas can reduce the growth rates of the sausage and kink instabilities. Here we propose the hypothesis that sheared helical flow can exert a similar stabilizing influence on CDI in YSO jets.

- by Radu Presura
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- Physics, Magnetohydrodynamics, Astrophysical Plasma, Numerical Analysis

This document was prepared as an account of work sponsored by a n agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees. makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefuln e s of any information. apparatus. product. or process disclosed. or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial produck process, or service by tradepame. trademark, manufacturer, or otherwise. does not necessarily constitute or imply its endorsement, recommendation. or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. f

- by James Crotinger
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- Plasma Physics, Experimental Research, Computers, Computer Simulation

The basic scales of motion and computational requirements for low frequency fluid drift turbulence are summarised in tutorial fashion. Basic signatures for each of the competing eigenmode types are given, some of which are accessible experimentally. The emphasis is on edge turbulence since it is less intuitive. The difference in physical mechanism between linear instabilities and fully developed turbulence at the same parameters is shown. The difference in physical character from more familiar MHD models is also addressed. Experimentally, one needs to measure the fluctuating potential as well as the transported quantities in order to distinguish among physical mechanisms.

In the concept known as Magnetized Target Fusion (MTF) in the United States and Magnitnoye Obzhatiye (MAGO) in Russia, a preheated and magnetized target plasma is hydrodynamically compressed to fusion conditions. Because the magnetic field suppresses losses by electron thermal conduction in the fuel during the target implosion heating process, the compression may be over a much longer time scale than in traditional inertial confinement fusion. Hence "lineron-plasma" compressions, magnetically driven using relatively inexpensive electrical pulsed power, may be practical. One candidate target plasma known as "MAGO' was originated in Russia and is now being jointly developed by the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF) and Los Alarnos National Laboratory (LANL). Other possible target plasmas now under investigation at LANL include wall-supported deuterium-fiber-initiated Z-pinches and compact toroids. Detailed computational modeling is being done of such target plasmas. In addition, liner-on-plasma compressions of such target plasmas to fusion conditions are being computationally modeled, and experimental and computational investigation of liner implosions suitable for MIT is continuing. Results will be presented.

- by Rickey Faehl
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- Plasma Physics, Magnetic field, Mathematical Models, Hydrodynamics
- by Katsuhiko Tsuchiya
- •
- Plasma Physics, Magnetohydrodynamics, Design, Conception