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Ignition and steady-state current drive capability of INTOR plasma

Description: The confinement capability of the INTOR plasma for achieving ignition and noninductively driven, Q>5 steady-state operation has been assessed for various energy confinement scaling laws and current drive schemes by using a global power balance model. Plasma operation contours are used to illustrate the boundaries of the operating regimes in density-temperature (n-T) space. Results of the analysis indicate a very restricted capability (if any) for ignition and a limited flexibility in driven modes of operation in the INTOR (8-MA) design. Nearly a factor of two increase in plasma current (through stronger plasma shaping) could improve the feasibility of ignition in INTOR. 14 refs., 4 figs., 3 tabs.
Date: January 1, 1988
Creator: Uckan, N.A.
Partner: UNT Libraries Government Documents Department

Relativistic effects on cyclotron wave absorption by an energetic electron tail in the PLT tokamak

Description: Electron cyclotron wave absorption by mildly relativistic electrons in the low density regime of the PLT tokamak is investigated. Appreciable wave damping is found for vertical propagation at frequencies of 50, 60, and 70 GHz when the spatially constant cyclotron frequency is 89 GHz. The perpendicular temperature T/sub perpendicular/(v/sub parallel/) of the fast tail is also measured from emission of radiation in the same direction. The results obtained are in satisfactory agreement with the theory of wave emission and absorption.
Date: July 1, 1984
Creator: Mazzucato, E.; Efthimion, P. & Fidone, I.
Partner: UNT Libraries Government Documents Department

Computer simulation of lower-hybrid heating in tokamaks. Final report

Description: A simple quasilinear model was added of lower hybrid heating to the BALDUR 1-D tokamak transport code. The program was used to simulate PLT and the INTOR reactor design. For PLT a temperature increase of approx. = 2 keV/kW of RF input power was predicted. Quasilinear theory gave slightly less heating than linear theory, because of greater electron edge losses.
Date: April 29, 1981
Creator: Ogden, J. M.
Partner: UNT Libraries Government Documents Department

Characteristics of radiated power for various TFTR (Tokamak Fusion Test Reactor) regimes

Description: Power loss studies were carried out to determine the impurity radiation and energy transport characteristics of various TFTR operation and confinement regimes including L-Mode, detached plasma, co-only neutral beam injection (energetic ion regime), and the enhanced confinement (''supershot'') regime. Combined bolometric, spectroscopic, and infrared photometry measurements provide a picture of impurity behavior and power accounting in TFTR. The purpose of this paper is to make a survey of the various regimes with the aim of determining the radiated power signatures of each. 10 refs., 6 figs., 1 tab.
Date: April 1, 1988
Creator: Bush, C.E.; Schivell, J.; McNeill, D.H.; Medley, S.S.; Hendel, H.W.; Hulse, R.A. et al.
Partner: UNT Libraries Government Documents Department

Bootstrap current in TFTR (Tokamak Fusion Test Reactor)

Description: Neutral-beam-heated plasmas in TFTR show evidence of substantial non-ohmically-driven toroidal current, even for balanced beam momentum input. The observations are inconsistent with calculations including only ohmic and beam-driven currents, and presently can only be matched by models including the neoclassical bootstrap current. 28 refs., 9 figs., 1 tab.
Date: March 1, 1988
Creator: Zarnstorff, M.C.; Bell, M.G.; Bitter, M.; Goldston, R.J.; Grek, B.; Hawryluk, R.J. et al.
Partner: UNT Libraries Government Documents Department

Computation of self-consistent 2-D MHD with neutral-beam and bootstrap currents in elongated plasmas

Description: The observation of substantial current drive from neutral beam injection (NBI) in TFTR, JET and DIII-D has led to renewed interest in a steady state, non-inductively driven tokamak. The discovery of apparently considerable neoclassical (bootstrap) current in TFTR, makes a steady state device even more attractive since the bootstrap portion of the current could be obtained without additional power input. Motivated by these results, we have developed a code, ACCOME, which self-consistently computes the 2-D MHD equilibrium with the current driven by neutral beams, bootstrap and the electric field. In this paper we first describe some details of the code in the next section and in the subsequent section show some applications to DIII-D and to a possible ITER design.
Date: April 5, 1983
Creator: Devoto, R.S.; Tani, K. & Azumi, M.
Partner: UNT Libraries Government Documents Department

Fast wave heating of two-ion plasmas in the Princeton large torus through minority cyclotron resonance damping

Description: Strong minority proton heating is produced in PLT through ion cyclotron resonance damping of fast waves at moderate rf power levels. In addition to demonstrating good proton confinement, the proton energy distribution is consistent with Fokker--Planck theory which provides the prescription for extrapolation of this heating regime to higher rf power levels.
Date: July 1, 1979
Creator: Hosea, J.; Bernabei, S. & Colestock, P.
Partner: UNT Libraries Government Documents Department

Fast wave heating in the Princeton Large Torus

Description: Fast wave heating in the ion cyclotron range of frequencies (ICRF) is being studied on the Princeton Large Torus (PLT) to evaluate its potential for heating large reactor-scale toroidal plasmas. Of primary interest are the two-ion and pure second harmonic heating regimes which, with proper control of the ion energy distribution and the rf power deposition profile, permit substantial energy glow into the bulk plasma ions. Initial heating experiments have been conducted with a single 1/2 turn antenna up to wave powers of P/sub rf/ approx. = 350 kW for durations of greater than or equal to 100 ms in the two-ion regime under conditions for which direct fundamental cyclotron damping on the minority ion species dominates the wave absorption. Ion-ion coupling serves to heat the majority ions and for energetic minority ion energy distributions, energy flow to the electrons results from electron drag. Substantial ion heating is found for D-p mixtures; ..delta..T/sub d/(0) approx. = 600 eV for 350 kW with anti n/sub e/ approx. = 2 x 10/sup 13/ cm/sup -3/. The deuteron heating efficiency is improved by about a factor of approx. 2 in D/sup -3/He mixtures; ..delta..T/sub d/(0) approx. = 500 eV for 150 kW with anti n/sub e/ approx. = 2.1 x 10/sup 13/ cm/sup -3/.
Date: October 1, 1979
Creator: Hosea, J.C.; Arunasalam, V. & Bernabei, S.
Partner: UNT Libraries Government Documents Department

Neutral beam heating of detached plasmas in TFTR

Description: Detached plasmas on TFTR have been heated with neutral beam auxiliary power for the first time. At beam powers above 2 MW the detached plasmas in TFTR expand and reattach to the limiters. Deuterium and/or impurity gas puffing can be used to maintain plasmas in the detached state at powers of over 5 MW. Transient events were observed in a number of these plasmas, including a confinement-related delay in evolution of the edge emissivity and some phenomena which appear similar to those seen in the H-mode. 16 refs., 5 figs.
Date: May 1, 1989
Creator: Bush, C.E.; Strachan, J.D.; Schivell, J.; Mansfield, D.K.; Taylor, G.; Grek, B. et al.
Partner: UNT Libraries Government Documents Department

Ordinary-mode fundamental electron cyclotron resonance absorption and emission in the Princeton Large Torus

Description: Fundamental electron cyclotron resonance damping for 4 mm waves with ordinary polarization is measured for propagation along the major radius traversing the midplane of the plasma in the Princeton Large Torus (PLT). Optical depths obtained from the data are in good agreement with those predicted by the relativistic hot plasma theory. Near blackbody emission over much of the plasma midplane is obtained and, in conjunction with the damping measurements, indicates that the vessel reflectivity is high. The practical use of ordinary mode fundamental electron cyclotron resonance heating (ECRH) in existing and future toroidal devices is supported by these results.
Date: November 1, 1979
Creator: Efthimion, P.C.; Arunasalam, V. & Hosea, J.C.
Partner: UNT Libraries Government Documents Department

Oak Ridge TNS Program: reference design and program plan for a TNS ECH startup system

Description: The use of microwave radio frequency (rf) heating in The Next Step (TNS) is considered to be a viable approach to accomplishing reliable preionization while significantly lowering the peak power requirements and cost of the ohmic heating power supply system. Electron cyclotron heating (ECH) is a promising type of rf heating in which high power microwave energy is deposited into the plasma region. The proposed system is based on a configuration of five 200-kW gyroklystrons which will deliver 1 MW at 120 GHz to the plasma area for pulse periods of up to 6.0 sec. Completion of an operational system could be targeted for December 1989 at an estimated cost (in 1978 dollars) of $4 million. A discussion and description of a conceptual system are presented. Estimates of costs, schedules, and research and development (R and D) needs are included.
Date: April 1, 1979
Creator: Rosenfeld, R.
Partner: UNT Libraries Government Documents Department

Experimental investigation on electron cyclotron absorption at down-shifted frequency in the PLT tokamak

Description: The absorption of 60 GHz electron cyclotron waves, with the extraordinary mode and an oblique angle of propagation, has been investigated in the PLT tokamak in the regime of down-shifted frequencies. The production of energetic electrons, with energies of up to 300 to 400 keV, peaks at values of toroidal field (approx. =29 kG) for which the wave frequency is significantly smaller than the electron cyclotron frequency in the whole plasma region. The observations are consistent with the predictions of the relativistic theory of electron cyclotron damping at down-shifted frequency. Existing rf sources make this process a viable method for assisting the current ramp-up, and for heating the plasma of present large tokamaks.
Date: May 1, 1986
Creator: Mazzucato, E.; Fidone, I.; Cavallo, A.; von Goeler, S. & Hsuan, H.
Partner: UNT Libraries Government Documents Department

Lower hybrid current drive in the PLT tokamak

Description: Order of magnitude improvements in the level and duration of current driven by lower hybrid waves have been achieved in the PLT tokamak. Steady currents up to 175 kA have been maintained for three seconds and 400 kA for 0.3 sec by the rf power alone. The principal current carrier appears to be a high energy (approx. 100 keV) electron component, concentrated in the central 20 to 40 cm diameter core of the 80 cm PLT discharge.
Date: July 1, 1982
Creator: Bernabei, S.; Daughney, C. & Efthimion, P.
Partner: UNT Libraries Government Documents Department

ORNL-TNS/PEPR overall heating requirements

Description: The ORNL TNS/PEPR studies have the objectives of (1) leading to a system that demonstrates the fusion reactor core in the mid-to-late 1980's and extrapolates to an economic tokamak power reactor, and (2) providing a near-term focus for the scientific and technological programs toward the power reactor. This discussion of the overall heating requirements for the ORNL TNS/PEPR is concerned with the neutral beams as the primary heating method, the electron-cyclotron resonance (ECR) heating at a lower power level for profile control, and the upper hybrid resonance (UHR) initiation and preheating of currentless plasmas to reduce current start-up loop voltage (V/sub l/) requirements.
Date: January 1, 1977
Creator: Peng, Y. K.M. & Rome, J. A.
Partner: UNT Libraries Government Documents Department

Plasma heating r and d assessment

Description: The purpose of this report is to compare the heating requirements of INTOR with the present state-of-the-art of tokamak plasma heating technology and demonstrated heating performance, and also with the technology expected by 1983-84 according to development and testing programs in place. This comparison results in a set of recommendations for a heating technology development program for the 1980s.
Date: November 1, 1979
Creator: Jassby, D.L.; Berkner, K.H.; Colestock, P.L.; Freeman, R.L.; Haselton, H.H.; Hosea, J.C. et al.
Partner: UNT Libraries Government Documents Department

Results of pellet injection into ISX-B

Description: Improvements in plasma performance with pellet injection have been achieved in several tokamaks in recent experiments. On the Impurity Study Experiment (ISX-B), an increase in plasma energy by as much as 50%, has been observed following pellet injection. With 1.5-mm pellets, the value for tau/sub E/, the gross energy confinement time determined from ..beta../sub equil/, has peaked at 1.7 times ISX-B scaling for n/sub e/ = 6 x 10/sup 13/ cm/sup -3/ in both well-gettered and ungettered discharges. Following the peak, in the well-gettered shots tau/sub E/ decays to 1.2 times ISX-B scaling within 50 ms after pellet injection. In the ungettered discharges tau/sub E/ follows the Z-mode scaling that is appropriate to the plasma conditions (P/sub B/ = 1.7 MW, I/sub p/ = 180 kA). Thus, pellet injection in ISX-B shows energy confinement better than that for gas puffing in clean discharges and matches the Z-mode improvement obtained in ungettered discharges. Confinement improvement following pellet injection has also been acheived in smaller (a/sub p/ = 20 cm) plasmas with 1.0 mm diameter pellets. Comparisons of pellet shots which do show this improvement against pellet shots which do not show it was present.
Date: January 1, 1985
Creator: Schuresko, D.D.
Partner: UNT Libraries Government Documents Department

Energy confinement in Doublet III with high-Z limiters

Description: This report describes the experimental measurements and data analysis techniques used to evaluate the energy confinement in noncircular plasmas produced in Doublet III. Major aspects of the confinement measurements and analysis techniques are summarized. Machine parameters, diagnostic systems and discharge parameters relavent to the confinement measurements are given. Magnetic analysis techniques used to determine the plasma shape are reviewed. Scaling of the on-axis values of electron temperature, confinement time and Z/sub eff/ with plasma density is presented. Comparison with scaling results from other circular tokamaks is discussed. Numerical and analytic techniques developed for calculating the plasma energy confinement time and self-consistent profiles of density, temperature, current, and flux in non-circular geometries are described. These techniques are applied to the data and used to determine the central and global electron energy confinement time for a typical doublet plasma. Additional aspects of the confinement such as the radial dependence of the electron thermal conductivity and the estimated ion temperature are explored with the aid of a non-circular transport simulation code. The results of the confinement measurements are summarized and discussed. A brief summary of the theoretically expected effects of noncircularity on plasma confinement is included for reference as Appendix I.
Date: February 1, 1980
Creator: Marcus, F.B.; Adcock, S.J.; Baker, D.R.; Blau, F.P.; Brooks, N.H.; Chase, R.P. et al.
Partner: UNT Libraries Government Documents Department

High beta results in ISX-B with intense neutral beam injection

Description: Experiments on the ISX-B device show a deterioration in confinement at high beam power. In particular the electron energy confinement time falls catastrophically with increasing beam power. The maximum volume averaged beta values achieved are <2.5%; this is much less than would be predicted by extrapolating the low power data. Elongation has not been observed to have any significant effect on the maximum attainable beta, perhaps due to the limited range of both internal and external elongation. The electron energy confinement time does not follow Alcator scaling at high injection powers. There are two likely candidates for the loss of confinement. The phenomena may be ..beta../sub p/ specific and caused by the gradual onset of resistive MHD pressure driven modes producing deteriorating confinement through fluctuations in the poloidal magnetic field. Alternatively the phenomena may be specific to the method of heating, neutral injection, being caused, for example, by plasma rotation, where the rotation speed approaches the ion thermal velocity. Experiments are in progress to investigate both of these possibilities.
Date: January 1, 1982
Creator: Edmonds, P.H.; Bates, S.C. & Bell, J.D.
Partner: UNT Libraries Government Documents Department

Effects of preionization by electron cyclotron heating in INTOR

Description: A model has been developed for the electron cyclotron heating (ECH) preionization and startup effects on the ISX-B tokamak. This model has satisfactory agreement with most of the observed phenomena on ISX-B. The model has been applied to INTOR under the assumption that sufficient power at a frequency commensurate with this device will be on hand. We have assumed the following parameters for INTOR: R = 5.3 m,a = 1.52 m, B/sub t/ = 6 T, and a maximum applied loop voltage of 35 V. The results suggest that moderate amounts of preionization will aid in the start up by allowing a reduction in the applied loop voltage, V/sub l/, will save some transformer flux, and will permit a more rapid current ramp. Massive preionization (greater than or equal to 1 MW) does not appear to be necessary.
Date: January 1, 1984
Creator: England, A. C. & Eldridge, D. C.
Partner: UNT Libraries Government Documents Department

Aspects of stellarator confinement scaling

Description: Extensive discussion has been made concerning stellarator experimental confinement scaling and the extrapolation to reactor systems. Two features are discussed here: (1) The role of hydrogen-impurity interactions. (2) The neoclassical (bootstrap) current has been invoked as an argument against the possibility of optimizing the stellarator magnetic configuration to reach high ..beta... It is felt that significant bootstrap current production under conditions of high ..beta.. will dominate the vacuum fields. In this regard, a brief summary is presented of a comparison made between ISX-B high-..beta.. data and the neoclassical predictions. The non-neoclassical rates of electron pitch-angle scattering serve to destroy this current, and are evidently responsible for a lack of evidence for the bootstrap current under conditions in tokamaks where a large effect is expected.
Date: January 1, 1981
Creator: Hogan, J.
Partner: UNT Libraries Government Documents Department

Plasma performance in JET: Achievements and projections

Description: An account is given of recent experimental advances on JET, especially as they relate to fusion performance. Scaling relations are used to identify the critical parameters which need to be optimized to secure the best fusion performance. Finally the established best performance of JET is used as a base to project the performance to be expected in future D-T operation. 13 refs., 20 figs., 6 tabs.
Date: January 1, 1988
Creator: Gibson, A.
Partner: UNT Libraries Government Documents Department

q-dependent, H-mode-like phenomena in TFTR

Description: A new phenomenon has been observed in TFTR discharges with neutral beam injection and slowly ramped plasma current. When q/sub /psi// (a) reaches certain values close to low-order rational numbers, the D/sub ..cap alpha../ emission decreases and the electron density profile broadens and increases, similar to observations during the H-mode in other tokamaks. This ''q-mode'' appears to have a neutral beam power threshold of /approximately/ 6 MW. During co-injection, the plasma toroidal rotation decreases by /approximately/ 50% at the transition. Very slowly toroidally rotating coherent adge modes, which slow and lock at the transition, were identified from the measured perturbations in /tilde B//sub theta// with mn /approximately/ q/sub /psi//(a). Calculations based on a tearing-mode model indicate that large islands, consistent with these measurements, could be present in the plasma edge and alter the plasma limiter interaction. At the transition Z/sub eff/ increases typically from 3 to 3.5. This increase and the electron density increase are caused largely by an increase in the carbon density. These increases raise the drag on fast ions, rapidly thermalizing some of the energy stored by beam ions, causing a transient rise in the plasma thermal energy. In addition, the global energy confinement time increases transiently. 26 refs., 7 figs., 1 tab.
Date: February 1, 1988
Creator: Budny, R.; Bell, M.; Bitter, M.; Bush, C.; Dylla, H. F.; Fredrickson, E. et al.
Partner: UNT Libraries Government Documents Department

PLT ion cyclotron range of frequencies heating program

Description: Measurements of energetic ions, impurity influx, recycling, and Bernstein waves generated in the plasma core are described for ICRF heating in PLT. Such measurements are being used for several launchers in order to optimize rf power deposition and discharge conditions. Preparations are underway to extend operation to higher rf power levels (approx. 5 MW) for the best attainable PLT conditions to permit more reactor-relevant extrapolations.
Date: September 1, 1984
Creator: Hosea, J.; Bell, R.; Budny, R.; Cavallo, A.; Cohen, S.; Colestock, P. et al.
Partner: UNT Libraries Government Documents Department