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in subjects: "Ecr Heating"

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Advanced Tokamak Scenario Modeling with Off-Axix ECH in DIII-D

Time-dependent simulations with transport coefficients derived from experimentally achieved discharges are used to explore the capability of off-axis electron cyclotron current drive (ECCD) to control hollow current profiles in negative central shear discharges. Assuming these transport coefficients remain unchanged at higher EC power levels, the simulation results show that high confinement, high normalized beta and high bootstrap fraction can be achieved with EC power expected to be available… more

Date: July 1, 1999

Creator: Murakami, M.; Casper, T. A.; Lao, L. L.; St. John, H. E.; Deboo, J. C.; Greenfield, C. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Macroscopic magnetic islands and plasma energy transport

A model is presented, based on the combined effects of m=n=l magnetic island dynamics, localized heat sources, large heat diffusivity along magnetic field lines and plasma rotation, which may explain the multipeaked temperature profiles and transport barriers observed in tokamak plasmas heated by electron cyclotron resonant waves.

Date: December 3, 1998

Creator: Cima, G; Porcelli, F; Rossi, E & Wootton, A J

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Modeling of electron cyclotron current drive experiments on DIII-D

Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in Advanced Tokamak (AT) operation. Localized ECCD has been clearly demonstrated in recent proof-of-principle experiments on DIII-D. The measured ECCD efficiency near the magnetic axis agrees well with standard theoretical predictions. However, for off-axis current drive the normalized experimental efficiency does not decrease with minor radius as expected from the standard theory; the observed… more

Date: May 1, 1999

Creator: Lin-Liu, Y. R.; Chan, V. S.; Luce, T. C.; Prater, R.; Sauter, O. & Harvey, R. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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High-power corrugates waveguide components for mm-wave fusion heating systems

Considerable progress has been made over the last year in the U.S., Japan, Russia, and Europe in developing high power long pulse gyrotrons for fusion plasma heating and current drive. These advanced gyrotrons typically operate at a frequency in the range 82 GHz to 170 GHz at nearly megawatt power levels for pulse lengths up to 5 s. To take advantage of these new microwave sources for fusion research, new and improved transmission line components are needed to reliably transmit microwave power … more

Date: October 1, 1996

Creator: Olstad, R.A.; Doane, J.L.; Moeller, C.P.; O`Neill, R.C. & Di Martino, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Applications of high power millimeter waves in the DIII-D fusion program

First operation of a new generation of MW level, 110 GHz generator (gyrotron) on the DIII-D fusion experimental device has been achieved. The desire for high power, cw millimeter (mm) wave sources to support fusion research and development is just now beginning to be realized. Plasma heating and current drive with directed mm waves rely on the strong absorption achieved when the wave frequency matches the natural ``cyclotron`` frequency of electrons in a magnetic field, or its harmonics. Recent… more

Date: August 1, 1996

Creator: Freeman, R.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Development of high power radio frequency components for fusion plasma heating. Final report, Revision 3

The purpose of this CRADA was to develop advanced microwave heating systems for both ion cyclotron heating and electron cyclotron heating for magnetic fusion reactors. This involved low-frequency (UHF), high-power (millimeter-wave) microwave components, such as antennas, windows, and matching elements. This CRADA also involved developing conceptual designs for new microwave sources. General Atomics built and tested the distributed cooled window and provided LLNL with transmission and reflection… more

Date: September 11, 1997

Item Type: Report

Partner: UNT Libraries Government Documents Department

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DIII-D electron cyclotron heating 2 MW upgrade project. Final report, FY1989--FY1997

The 2 MW, 110 GHz ECH system was based on the General Atomics Proposal to the Department of Energy: DIII-D Fusion Research Program Vol. I Technical, and Vol. II Cost (GACP-72-166, July 1987 and revised). This proposal was reviewed in August 1987 by a senior technical review committee, who recommended to vigorously pursue increasing the ECH power to 6 MW. The realization of the higher frequency and power ECH on DIII-D was recognized by the committee to be important, not only for the DIII-D progr… more

Date: August 1, 1997

Creator: Callis, R. W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Multi-megawatt 110 GHz ECH system for the DIII-D tokamak

Two 110 GHz gyrotrons with nominal output power of 1 MW each have been installed on the DIII-D tokamak. The first 110 GHz gyrotron built by Gycom has a nominal rating of 1 MW and a 2s pulse length, with the pulse length being determined by the maximum temperature allowed on the edge cooled boron nitride window. This gyrotron was first operated into the DIII-D tokamak in late 1996. The second gyrotron was built by Communications and Power Industries (CPI) was commissioned during the spring of 19… more

Date: November 1, 1997

Creator: Callis, R. W.; Lohr, J.; O`Neill, R. C.; Ponce, D. & Prater, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Determination of the Electron Cyclotron Current Drive Profile

Evaluation of the profile of non-inductive current density driven by absorption of electron cyclotron waves (ECCD) using time evolution of the poloidal flux indicated a broader profile than predicted by theory. To determine the nature of this broadening, a 1-1/2 D transport calculation of current density evolution was used to generate the signals which the DIII-D motional Stark effect (MSE) diagnostic would measure in the event that the current density evolution followed the neoclassical Ohm's … more

Date: November 1, 1999

Creator: Luce, T. C.; Petty, C. C.; Schuster, D. I. & Makowski, M. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Future Prospects for ECR Plasma Generators With Improved Charge State Distributions

The growing number and variety of fundamental, applied, and industrial uses for high intensity, high charge state ion beams continues to be the driving force behind efforts to develop Electron Cyclotron Resonance (ECR) ion sources with superior performance characteristics. Incumbent with the advent of sub-micron electronic devices and their fabrication has been the demand for improved process control and optimization. These demands have led to the development of methods for cleaning, chemical e… more

Date: June 1, 1997

Creator: Alton, G. D. & Liu, Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Distinguishing Gyro-Bohm and Bohm scaling in stellarators

With statistical analysis of global data from one, two and four stellarators, it is possible to draw limited conclusions whether Gyro- Bohm or Bohm scaling prevails. Either scaling may be favored, depending on whether corrections are included for possible {Beta} and v{sub *} corrections and whether all data are taken, or selected cases with low collisionality, or low net toroidal current, or with ECH heating applied, and so on. Monte Carlo-like simulations are used to test reliability of infere… more

Date: May 5, 1993

Creator: Dory, R.A.; Murakami, M. & Stroth, U.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Performance of the DIII-D 110 GHz ECH system during the first year of operations and testing

The first of four Varian 500 kW 110 GHz gyrotrons (VGT-8011) to be used in the new 2 MW 110 GHz electron cyclotron heating system being developed for the DIII-D tokamak was put into test at General Atomics within the last year. This gryotron has been used to demonstrate the overall system efficiency and to validate the design of individual transmission line components. The first plasma heating observed with a 110 GHz was consistent with the power expected for the greater than 85% transmission e… more

Date: October 1, 1993

Creator: Wright, A. L.; Allen, J. C.; Cary, W. P. & Harris, T. E.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fast wave current drive on DIII-D

The physics of electron heating and current drive with the fast magnetosonic wave has been demonstrated on DIII-D, in reasonable agreement with theoretical modeling. A recently completed upgrade to the fast wave capability should allow full noninductive current drive in steady state advanced confinement discharges and provide some current density profile control for the Advanced Tokamak Program. DIII-D now has three four-strap fast wave antennas and three transmitters, each with nominally 2 MW … more

Date: July 1, 1995

Creator: deGrassie, J. S.; Petty, C. C. & Pinsker, R. I.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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NRL quasioptical gyrotron program. Final report, November 1, 1991--October 31, 1993

The quasioptical gyrotron (QOG) has been under development as a high power, tunable source for tokamak plasma heating applications. Given the critical importance of source efficiency for large-scale ESCH applications, understanding the causes of the low QOG efficiency and finding ways of improving it became a top priority for the current NRL program. The importance of the present work is that is represents new insight into the factors controlling the efficiency of quasioptical gyrotrons. The au… more

Date: June 1, 1997

Creator: Fliflet, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Upgrade of the DIII-D RF systems

The DIII-D Advanced Tokamak Program requires the ability to modify the current density profile for extended time periods in order to achieve the improved plasma conditions now achieved with transient means. To support this requirement DIII-D has just completed a major addition to its ion cyclotron range of frequency (ICRF) systems. This upgrade project added two new fast wave current drive (FWCD) systems, with each system consisting of a 2 MW, 30 to 120 MHz transmitter, an all ceramic insulated… more

Date: October 1, 1995

Creator: Callis, R. W.; Cary, W. P. & O`Neill, R. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Electron cyclotron heating experiments on the DIII-D tokamak

Initial experiments on heating and current drive using second harmonic electron cyclotron heating (ECH) are being performed on the DIII-D tokamak using the new 110 GHz ECH system. Modulation of the ECH power in the frequency range 50 to 300 Hz and detection of the temperature perturbation by ECE diagnostics is used to validate the location of the heating. This technique also determines an upper bound on the width of the deposition profile. Analysis of electron cyclotron current drive indicates … more

Date: January 1998

Creator: Prater, R.; Austin, M. E. & Bernabei, S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The high density and high {Beta}{sub pol} disruption mechanism on TFTR

No Description Available.

Date: April 1, 1993

Creator: Fredrickson, E. D.; Manickam, J.; McGuire, K. M.; Monticello, D.; Nagayama, Y.; Park, W. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Interaction of fast waves with ions

To fully utilize the available power sources in DIII-D (FW, NBI, ECH), understanding of the synergism between the heating mechanisms is important. In this paper the ion distribution, under simultaneous application of NBI and FW, is calculated from Fokker-Planck code CQL3D coupled to ray-tracing code CURRAY. It is found that interaction between energetic ions and FW can be minimized or maximized by adjusting various parameters such as magnetic field, density, beam energy, and FW frequency. Speci… more

Date: June 1, 1995

Creator: Chiu, S. C.; deGrassie, J. S. & Harvey, R. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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STABILZATION OF NEOCLASSICAL TEARING MODES BY LOCALIZED ECCD IN DIII-D

Neoclassical tearing modes (NTMs) are MHD modes which can become destabilized in a tokamak by a helical pressure perturbation. The NTM is particularly well suited to control since the mode is linearly stable although nonlinearly unstable, so if the island amplitude can be decreased below a threshold size the mode will decay and vanish. One means of shrinking the island is the replacement of the ''missing'' bootstrap current by a localized current generated by electron cyclotron current drive (E… more

Date: May 1, 2002

Creator: Prater, R.; Eliss, R. A., III; La Haye, R. J.; Lohr, J. M.; Luce, T. C.; Perkins, F. W. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Experimental investigation of fast electron diffusion during ECRH

The spatial diffusion of fast electrons created by electron cyclotron resonant heating (ECRH) is examined using electron cyclotron emissions viewed along a nearly vertical chord in the TEXT-U tokamak. Enhanced emission at frequencies downshifted from the cold cyclotron frequency is attributed to non-thermal electrons. The emission spectra during ECRH are consistent with the presence of low density suprathermal electrons. Comparison of the spectra measured during ECRH with a bounce averaged Fokk… more

Date: June 7, 1995

Creator: Steimle, R.F.; Roberts, D.R. & Giruzzi, G.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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3 MW, 110 GHz ECH system for the DIII-D tokamak

To support the Advanced Tokamak (AT) operating regimes in the DIII-D tokamak, methods need to be developed to control the current and pressure profiles across the plasma discharge. In particular, AT plasmas require substantial off-axis current in contrast to normal tokamak discharges where the current peaks on-axis. An effort is under way to use Electron Cyclotron Current Drive (ECCD) as a method of sustaining the off-axis current in AT plasmas. The first step in this campaign is the installati… more

Date: July 1998

Creator: Callis, R. W.; Lohr, J.; Ponce, D.; Harris, T. E.; O`Neill, R. C.; Remsen, D.B. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Continued development of modeling tools and theory for rf heating. Final report

The work performed during the grant has been reported long before this date, specifically in: (1) the grant`s annual performance report for 1991, MRC/WDC-R-277; (2) the published AIP Conference Proceedings {number_sign}244, Radio Frequency Power in Plasmas, Charleston, SC 1991, ``Evaluation of Wave Dispersion, Mode-Conversion, and Damping for ECRH with Exact Relativistic Corrections,`` by D.N. Smithe and P.L. Colestock; and (3) an unpublished paper entitled ``Temperature Anisotropy and Rotation… more

Date: September 1, 1998

Creator: Smithe, D.N.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Status of Advanced Tokamak Scenario Modeling with Off-Axis Electron Cyclotron Current Drive in DIII-D

The status of modeling work focused on developing the advanced tokamak scenarios in DIII-D is discussed. The objectives of the work are two-fold: (1) to develop AT scenarios with ECCD using time-dependent transport simulations, coupled with heating and current drive models, consistent with MHD equilibrium and stability; and (2) to use time-dependent simulations to help plan experiments and to understand the key physics involved. Time-dependent simulations based on transport coefficients derived… more

Date: December 1, 1999

Creator: Murakami, M.; St.John, H. E.; Casper, T. A.; Chu, M. S.; DeBoo, J. C.; Greenfield, C. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Current profile modeling to extend the duration of high performance advanced Tokamak modes in DIII-D

We use a model for negative central shear (NCS) heat transport which has a parametric dependence on the plasma conditions with a transport barrier dependence on the minimum of the safety factor profile, 4, qualitatively consistant with experimental observations. Our intention is not to do a detailed investigation of transport models but rather to provide a reasonable model of heat conductivity to be able to simulate effects of electron cyclotron heating (ECH) and current drive (ECCD) on confine… more

Date: June 25, 1998

Creator: Casper, T. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department