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Numerical calculation of impurity charge state distributions

Description: The numerical calculation of impurity charge state distributions using the computer program IMPDYN is discussed. The time-dependent corona atomic physics model used in the calculations is reviewed, and general and specific treatments of electron impact ionization and recombination are referenced. The complete program and two examples relating to tokamak plasmas are given on a microfiche so that a user may verify that his version of the program is working properly. In the discussion of the examples, the corona steady-state approximation is shown to have significant defects when the plasma environment, particularly the electron temperature, is changing rapidly.
Date: September 1, 1977
Creator: Crume, E. C. & Arnurius, D. E.
Partner: UNT Libraries Government Documents Department

Physics of burn control in tokamak reactors

Description: A one-dimensional multifluid transport code was used to investigate some of the critical physics considerations for long burn times in a tokamak fusion reactor. Among these are the effects of helium ash build-up, toroidal field ripple, and fueling in the presence of a divertor. Particle and energy transport models are based on extrapolations from present day devices.
Date: January 1, 1979
Creator: Attenberger, S.E. & Houlberg, W.A.
Partner: UNT Libraries Government Documents Department

Tandem Mirror Reactor Systems Code (Version I)

Description: A computer code was developed to model a Tandem Mirror Reactor. Ths is the first Tandem Mirror Reactor model to couple, in detail, the highly linked physics, magnetics, and neutronic analysis into a single code. This report describes the code architecture, provides a summary description of the modules comprising the code, and includes an example execution of the Tandem Mirror Reactor Systems Code. Results from this code for two sensitivity studies are also included. These studies are: (1) to determine the impact of center cell plasma radius, length, and ion temperature on reactor cost and performance at constant fusion power; and (2) to determine the impact of reactor power level on cost.
Date: September 1, 1985
Creator: Reid, R.L.; Finn, P.A.; Gohar, M.Y.; Barrett, R.J.; Gorker, G.E.; Spampinaton, P.T. et al.
Partner: UNT Libraries Government Documents Department

Tokamak equilibria with. beta. close to 1

Description: Equilibrium calculations have been done for a High-Beta Tokamak experiment, that has been under consideration in Los Alamos. The geometry studied was that of a torus with a major radius R/sub 0/ of 30 cm and a racetrack-shaped minor cross section of a height of 48 cm and a width of 24 cm. A metal shell around the discharge vessel keeps the magnetic surfaces closed and inside the vessel so that force-free currents can flow along the field lines. Results showing equilibria at very high beta have been obtained with a computer program. It appears that the beta limit for equilibrium has disappeared and that the force-free currents and the elongation of the minor cross section allow equilibria with a beta close to 1 at a small shift of the magnetic axis. There is a strong relation between these pinch-like equilibria and the Flux Conserving Tokamak (F.C.T.).
Date: January 1, 1977
Creator: Van der Lann, P.C.T. & Mann, L.W.
Partner: UNT Libraries Government Documents Department

Disruption model

Description: Calculations of disruption time and energy dissipation have been obtained by simulating the plasma as an electrical conducting loop that varies in resistivity, current density, major radius. The calculations provide results which are in good agreement with experimental observations. It is believed that this approach allows engineering designs for disruptions to be completed in large tokamaks such as INTOR or FED.
Date: July 1, 1982
Creator: Murray, J.G. & Bronner, G.
Partner: UNT Libraries Government Documents Department

Physics of compact ignition tokamak designs

Description: Models for predicting plasma performance in compact ignition experiments are constructed on the basis of theoretical and empirical constraints and data from tokamak experiments. Emphasis is placed on finding transport and confinement models which reproduce results of both ohmically and auxiliary heated tokamak data. Illustrations of the application of the models to compact ignition designs are given.
Date: March 1, 1986
Creator: Singer, C.E.; Ku, L.P.; Bateman, G.; Seidl, F. & Sugihara, M.
Partner: UNT Libraries Government Documents Department

Coupled plasma-neutral transport model for the scrape-off region

Description: Analysis of the scrape-off region requires treatment of the plasma transport along and across the field lines and inclusion of the neutral transport effects. A method for modeling the scrape-off region that is presented here uses separate models for each of these aspects that are coupled together through an iteration procedure that requires only minimal numerical effort. The method is applied here to estimate the neutral pumping rates in the pump-limiter and divertor options for a proposed deuterium-tritium (D-T) ignition experiment. High neutral recycling in the vicinity of the neutralizer plate dramatically affects pumping rates for both the pump-limiter and divertor. In both cases, the plasma flow into the channel surrounding the neutralizer plate is greatly reduced by the neutral recycling. The fraction of this flow that is pumped can be large (> 50%), but in general it is dependent on the particular geometry and plasma conditions. It is estimated that pumping speeds approximately greater than 10/sup 5/ L/s are adequate for the exhaust requirements in the pump-limiter and the divertor cases. Also, high neutral recycling on the front surface of the limiter tends to increase the neutral pumping rate.
Date: March 1, 1985
Creator: Galambos, J.D.; Peng, Y.K.M. & Heifetz, D.
Partner: UNT Libraries Government Documents Department

Fusion-product ash buildup in tokamak with radial electric field

Description: The buildup of thermalized fusion products (ash) in a tokamak can seriously limit burn times. Prior studies have concentrated on deposition profile effects on alpha particle transport in tokamaks but have not considered the effect on ash of radial electric fields (either created internally, e.g. due to high-energy alpha leakage, or generated externally). The present study focuses on this issue since it appears that electric fields might offer one approach to control of the ash. Approximate field and source profiles are used, based on prior calculations. (MOW)
Date: January 1, 1979
Creator: Downum, W.B.; Choi, C.K. & Miley, G.H.
Partner: UNT Libraries Government Documents Department

User's guide for FRMOD, a zero dimensional FRM burn code

Description: The zero-dimensional FRM plasma burn code, FRMOD is written in the FORTRAN language and is currently available on the Control Data Corporation (CDC) 7600 computer at the Magnetic Fusion Energy Computer Center (MFECC), sponsored by the US Department of Energy, in Livermore, CA. This guide assumes that the user is familiar with the system architecture and some of the utility programs available on the MFE-7600 machine, since online documentation is available for system routines through the use of the DOCUMENT utility. Users may therefore refer to it for answers to system related questions.
Date: October 15, 1979
Creator: Driemeryer, D. & Miley, G.H.
Partner: UNT Libraries Government Documents Department

Study of possible separable solutions for plasma transport in ohmically heated tokamaks

Description: The transport problem for an ohmically heated tokamak plasma is investigated analytically with the separation of the variables time, t, and rho = r/sup 2/h(t), where r is the space coordinate and h(t) is only a function of time. This investigation examines the circumstances under which these analytical solutions are possible. The time evolution of the current density and temperature profiles is then obtained for a simple plasma model which includes the electric field diffusion and heat conduction losses. Expressions are also given for plasma discharge parameters such as the time evolution of the safety factor, the plasma current, the poloidal flux function, the skin time, the poloidal beta, the transformer flux, and the electron energy lifetime. The results are then applied to a typical size tokamak device.
Date: October 1, 1977
Creator: Uckan, T.
Partner: UNT Libraries Government Documents Department

High pressure tokamaks. [Review of equilibrium and stability problems]

Description: The successful development of the neutral beam injection method of heating tokamaks has opened up a new range of theoretically predicted phenomena to be explored. This article, intended for the nonspecialist, reviews the existing experimental observations and theoretical understanding of tokamak equilibrium and large scale stability. Then a survey is presented of the new phenomena, such as flux conserving sequences of equilibria and pressure-driven ballooning modes, that are expected to accompany the significantly enhanced plasma pressure to be produced in tokamaks now under construction.
Date: May 1, 1978
Creator: Bateman, G.
Partner: UNT Libraries Government Documents Department

Axisymmetric tokamak scapeoff transport

Description: We present the first self-consistent estimate of the magnitude of each term in a fluid treatment of plasma transport for a plasma lying in regions of open field lines in an axisymmetric tokamak. The fluid consists of a pure hydrogen plasma with sources which arise from its interaction with neutral hydrogen atoms. The analysis and results are limited to the high collisionality regime, which is optimal for a gaseous neutralizer divertor, or to a cold plasma mantle in a tokamak reactor. In this regime, both classical and neoclassical transport processes are important, and loss of particles and energy by diamagnetic flow are also significant. The prospect of extending the analysis to the lower collisionality regimes encountered in many existing experiments is discussed.
Date: August 1, 1982
Creator: Singer, C.E. & Langer, W.D.
Partner: UNT Libraries Government Documents Department

FERMI: a code for modeling field-reversed magnetic-mirror fusion devices

Description: We present the design and implementation for the array processor of FERMI, a code for modeling the physics of field-reversed magnetic-mirror fusion machines. The physical model is described briefly, along with a discussion of important physical effects that this code can model. We show that the code results are in agreement with theoretical predictions.
Date: February 1, 1981
Creator: Brengle, T.A. & Cohen, B.I.
Partner: UNT Libraries Government Documents Department

TRIDENT-CTR: a two-dimensional transport code for CTR applications

Description: TRIDENT-CTR is a two-dimensional x-y and r-z geometry multigroup neutral transport code developed at Los Alamos for toroidal calculations. The use of triangular finite elements gives it the geometric flexibility to cope with the nonorthogonal shapes of many toroidal designs of current interest in the CTR community.
Date: January 1, 1978
Creator: Seed, T.J.
Partner: UNT Libraries Government Documents Department

Nuclear elastic scattering effects on fusion product transport in the FRM

Description: Large energy transfer (LET) events such as nuclear elastic scatterng (NES) are shown to have significant effects on fusion product transport in the field-reversed mirror. The method used and preliminary results obtained from the study on NES effects on f/sub p/ orbits are described. (MOW)
Date: January 1, 1981
Creator: DeVeaux, J.C.; Greenspan, E. & Miley, G.H.
Partner: UNT Libraries Government Documents Department

Sufficient condition for velocity-space stability of the alpha particle distribution in a tokamak reactor

Description: A condition is derived for the velocity-space distribution of suprathermal alpha particles to be monotonically decreasing with energy - and hence stable to homogeneous plasma instabilities - during the heating phase of a tokamak reactor. This stability condition is easily satisfied for presently envisaged neutral injection heating of reactors, but may be violated in strong heating of smaller plasmas or during fast compressional heating.
Date: August 1, 1980
Creator: Cordey, J.G.; Goldston, R.J. & Mikkelsen, D.R.
Partner: UNT Libraries Government Documents Department

Guiding-center Hamiltonian figure-8 particles in axisymmetric field-reversed configurations

Description: The guiding-center Hamiltonian K is derived for so-called figure-8 particles which are present in field-reversed mirror configurations, using a formalism developed previously. For such particles, the gyro-orbit cannot be approximated by a circle, and standard approaches to guiding-center theory are thus totally inapplicable. K manifests this intrinsic difference by a quite different dependence on the gyroaction, and by familiar effects such as mirroring and magnetic-gradient drifts being controlled by the radial derivative of the magnetic field strength B at the point of field-reversal, rather than by B itself, as occurs in standard guiding-center theory.
Date: September 1, 1979
Creator: Mynick, H.E.
Partner: UNT Libraries Government Documents Department

Transport code studies of INTOR at PPPL

Description: This report summarizes transport modeling studies carried out with the BALDUR one-dimensional transport code for the International Tokamak Reactor INTOR. This report has been written to provide an accessible compilation of INTOR plasma simulation results, and to be included as part of the documentation provided by the Modeling Subcommittee. The reference transport model and results of plasma simulations using this model are described. Particular attention is paid to the length of the heating pulse needed for ignition, and the value of the plasma pressure at ignition. The particle fluxes through the plasma boundary are also reported. The results of varying the assumptions in the reference machine design and transport model are reported. Particular attention is paid to the problem of variations in the assumed plasma confinement, since this is a major source of uncertainty in reactor design. The conclusions of this study are summarized.
Date: November 1, 1979
Creator: Singer, C.E.; Post, D.E. & Rutherford, P.H.
Partner: UNT Libraries Government Documents Department

TMRBAR: a code to calculate plasma parameters for tandem-mirror reactors operating in the MARS mode

Description: The purpose of this report is to document the plasma power balance model currently used by LLNL to calculate steady state operating points for tandem mirror reactors. The code developed from this model, TMRBAR, has been used to predict the performance and define supplementary heating requirements for drivers used in the Mirror Advanced Reactor Study (MARS) and for the Fusion Power Demonstration (FPD) study. The equations solved included particle and energy balance for central cell and end cell species, quasineutrality at several cardinal points in the end cell region, as well as calculations of volumes, densities and average energies based on given constraints of beta profiles and fusion power output. Alpha particle ash is treated self-consistently, but no other impurity species is treated.
Date: August 30, 1983
Creator: Campbell, R.B.
Partner: UNT Libraries Government Documents Department

Studies of finite gyro-radius effects in a field reversed mirror configuration

Description: The field-reversed mirror (FRM) is characterized by a small size such that finite gyro-radius effects must be considered in both stability and transport analyses. Consequently, such effects are important to the interpretation of both ongoing experiments and extrapolation to future reactor concepts. The present work employs an energy principle to study stability of low-frequency (..omega.. << ..cap omega../sub ce/, ..omega.. approx. = ..cap omega../sub ci/) acoustic modes. Also a Monte Carlo technique has been developed for study of high energy-ion transport.
Date: January 1, 1979
Creator: Miley, G.H.; Gilligan, J.G.; Driemeyer, D.E.; Morse, E.C. & Condit, W.C.
Partner: UNT Libraries Government Documents Department

Anomalous alpha particle transport in thermonuclear tokamak plasma

Description: Due to the strong localization of the fusion born ..cap alpha..-particles in velocity and configuration space and their coupling to Alfven waves in the background plasma the relaxation of ..cap alpha..-s is anomalous. In a finite system, the enhanced electromagnetic fluctuations can produce rapid spatial losses of ..cap alpha..-population and energy. These losses prevent the ..cap alpha..-velocity distribution from attaining a stable collisional equilibrium, thus maintaining a steady state turbulence level. A self-consistent numerical quasilinear calculation is performed for the most dominant mode, showing the evolution of the ..cap alpha..-distribution and yielding the anomalous loss rates.
Date: August 1, 1977
Creator: Sigmar, D. J. & Chan, M. C.
Partner: UNT Libraries Government Documents Department

User's guide for MCFRM, a Monte Carlo particle code for FRM studies

Description: The Monte Carlo particle code MCFRM described in this work is also written in the FORTRAN language and is available on either the MFE-7600 or the CRAY-1 computers. The discussion presented here deals only with the steps required to execute the code on the CRAY, since the majority of its use should be on that machine.
Date: October 15, 1979
Creator: Driemeyer, D. & Miley, G.H.
Partner: UNT Libraries Government Documents Department