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in creator/contributor: "Prater, R."

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Electron-cyclotron-heating results on JFT-2, and their implications for the Doublet III ECH design

Electron cyclotron heating experiments are described in which 28 GHz microwave power is injected into the JFT-2 tokamak. Ordinary mode power injected from the low field side increased the central electron temperature from 600 eV to 1000 eV with 110 kW, for densities below the ordinary mode cutoff density of 1.0 x 10/sup 13/ cm/sup -3/. Extraordinary mode power launched obliquely from the high field side increased the temperature from 600 eV to 1200 eV with 85 kW, for densities well below the ex… more

Date: March 1, 1982

Creator: Prater, R. & Moeller, C.P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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EC-5 fifth international workshop on electron cyclotron emission and electron cyclotron heating

This report contains papers on the following topics: electron cyclotron emission measurements; electron cyclotron emission theory; electron cyclotron heating; gyrotron development; and ECH systems and waveguide development. These paper have been indexed separately elsewhere. (LSP).

Date: December 31, 1985

Creator: Prater, R. & Lohr, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Noninductive current drive experiments on DIII-D, and future plans

Experiments on DIII-D (and other tokamaks) have shown that improved performance can follow from optimization of the current density profile. Increased confinement of energy and a higher limit on beta have both been found in discharges in which the current density profile is modified through transient means, such as ramping of current or elongation. Peaking of the current distribution to obtain discharges with high internal inductance {ell}{sub i} has been found to be beneficial. Alternatively, … more

Date: February 1, 1994

Creator: Prater, R.; Austin, M. E. & Baity, F. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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FWCD and ECCD experiments on DIII-D

Fast wave current drive and electron cyclotron current drive experiments have been performed on the DIII-D tokamak as part of the advanced tokamak program. The goal of this program is to develop techniques for controlling the profile of the current density in order to access regimes of improved confinement and stability. The experiments on fast wave current drive used a four strap antenna with 900 phasing between straps. A decoupler was used to help maintain the phasing, and feedback control of… more

Date: February 1, 1994

Creator: Prater, R.; Austin, M. E. & Baity, F. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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First results on fast wave current drive in advanced tokamak discharges in DIII-D

Initial experiments have been performed on the DIII-D tokamak on coupling, direct electron heating, and current drive by fast waves in advanced tokamak discharges. These experiments showed efficient central heating and current drive in agreement with theory in magnitude and profile. Extrapolating these results to temperature characteristic of a power plant (25 keV) gives current drive efficiency of about 0.3 MA/m{sup 2}.

Date: July 1, 1995

Creator: Prater, R.; Cary, W.P. & Baity, F.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Electron Cyclotron Current Drive Efficiency in General Tokamak Geometry

Green's-function techniques are used to calculate electron cyclotron current drive (ECCD) efficiency in general tokamak geometry in the low-collisionality regime. Fully relativistic electron dynamics is employed in the theoretical formulation. The high-velocity collision model is used to model Coulomb collisions and a simplified quasi-linear rf diffusion operator describes wave-particle interactions. The approximate analytic solutions which are benchmarked with a widely used ECCD model, facilit… more

Date: March 1, 2003

Creator: Lin-Lui, Y. R.; Chan, V. S. & Prater, R.

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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Radial Transport Effects on Eccd in the Tcv and Diii-D Tokamaks and on Ohmic Discharges in the Mst Rfp

The comprehensive CQL3D Fokker-Planck/Quasilinear simulation code has been benchmarked against experiment over a wide range of electron cyclotron conditions in the DIII-D tokamak (C.C. Petty et al., 14th Topical Conf. on RF Power in Plasmas, 2002). The same code, in disagreement with experiment, gives 560 kA of ECCD for a well documented, completely ECCD-driven, 100 kA TCV shot [O. Sauter et al, PRL, 2000]. Recent work (R.W. Harvey et al, Phys. Rev. Lett., 2002) has resolved the differences as … more

Date: July 1, 2002

Creator: Harvey, R. W.; Sauter, O.; Prater, R.; Nikkola, P.; O'connell, R. & Forest, C. B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fast Wave Heating and Current Drive in DIII-D Discharges With Negative Central Shear

The noninductive current driven by fast Alfven waves (FWCD) has been applied to discharges in DIII-D with negative central shear. Driven currents as high as 275 kA have been achieved with up to 3 MW of fast wave power with the efficiency and profile as predicted by theory-based modeling. When counter-current FWCD was applied to discharges with negative central shear, the negative shear was strengthened and prolonged, showing that FWCD can help to control the current profile in advanced tokamak … more

Date: October 1, 1996

Creator: Prater, R.; Austin, M. E. & Baity, F. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Electron cyclotron current drive and current profile control in the DIII-D tokamak

Recent work in many tokamaks has indicated that optimization of the current profile is a key element needed to sustain modes of improved confinement and stability. Generation of localized current through application of electron cyclotron (EC) waves offers a means of accomplishing this. In addition to profile control, electron cyclotron current drive (ECCD) is useful for sustaining the bulk current in a steady state manner and for instability suppression. ECCD is particularly well suited for con… more

Date: July 1998

Creator: Prater, R.; Luce, T. C. & Petty, C. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Superconducting poloidal coils for STARFIRE commercial reactor

STARFIRE is considered to be the tenth commercial tokamak power plant. A preliminary design study on its superconducting poloidal coil system is presented. Key features of the design studies are: the elimination of the ohmic heating coil; the trade-off studies of the equilibrium field coil locations; and the development of a conceptual design for the superconducting equilibrium field coils. Described are the 100 kA cryostable conductor design, the coil structure and evaluation of the coil force… more

Date: January 1, 1979

Creator: Wang, S. T.; Evans, K., Jr.; Turner, L. R.; Huang, Y. C.; Prater, R. & Alcorn, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Physics of Off-Axis Electron Cyclotron Current Drive

Electron cyclotron current drive is a key option for driving current off-axis in a tokamak, as needed for example for current profile control or for suppression of neoclassical tearing modes. Experiments in DIII-D at low beta have shown that the partial cancellation of the Fisch-Boozer co-current by the Ohkawa counter-current can cause strong deterioration of the current drive efficiency at larger minor radius. However, more recent experiments at higher power have shown that the loss in efficie… more

Date: July 1, 2002

Creator: Prater, R.; Petty, C. C.; Harvey, R.; Lin-Liu, Y. R.; Lohr, J. M. & Luce, T. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

THE 110 GHz MICROWAVE HEATING SYSTEM ON THE DIII-D TOKAMAK

OAK-B135 Six 110 GHz gyrotrons in the 1 MW class are operational on DIII-D. Source power is > 4.0 MW for pulse lengths {le} 2.1 s and {approx} 2.8 MW for 5.0 s. The rf beams can be steered poloidally across the tokamak upper half plane at off-perpendicular injection angles in the toroidal direction up to {+-} 20{sup o}. measured transmission line loss is about -1 dB for the longest line, which is 92 m long with 11 miter bends. Coupling efficiency into the waveguide is {approx} 93% for the Ga… more

Date: July 2003

Creator: Lohr, J.; Callis, R. W.; Doane, J. L.; Ellis, R. A.; Gorelov, Ya; Kajiwara, K. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Polarization Measurements During Electron Cyclotron Heating Experiments in the DIII-D Tokamak

The polarization of the launched electron cyclotron wave has been optimized for coupling to the X-mode by adjusting the inclination of grooved mirrors located in two consecutive mitre bends of the waveguide. The unwanted O-mode component of the launched beam can be positively identified by the difference in the power deposition profiles between X-mode and O-mode. The optimal polarization for X-mode launch is in good agreement with theoretical expectations.

Date: July 1, 1999

Creator: Petty, C. C.; Luce, T. C.; Austin, M. E.; Ikezi, H.; Lohr, J. & Prater, R.

Item Type: Article

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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The DIII-D 3 MW, 110 GHz ECH System

Three 110 GHz gyrotrons with nominal output power of 1 MW each have been installed and are operational on the DIII-D tokamak. One gyrotron is built by Gycom and has a nominal rating of 1 MW and a 2 s pulse length, with the pulse length being determined by the maximum temperature allowed on the edge cooled Boron Nitride window. The second and third gyrotrons were built by Communications and Power Industries (CPI). The first CPI gyrotron uses a double disc FC-75 cooled sapphire window which has a… more

Date: July 1, 1999

Creator: Callis, R. W.; Lohr, J.; Ponce, D.; O'Neill, R. C.; Prater, R. & Luce, T. C.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Modeling of Trapped Electron Effects on Electron Cyclotron Current Drive for Recent DIII-D Experiments

Owing to its potential capability of generating localized non-inductive current, especially off-axis, Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in achieving Advanced Tokamak (AT) operation. In recent DIII-D proof-of-principle experiments [1], localized off-axis ECCD has been clearly demonstrated for first time. The measured current drive efficiency near the magnetic axis agrees well with predictions of the bounce-averaged Fokker-Planck… more

Date: August 1999

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

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Modeling of 110 GHz electron cyclotron wave propagation and absorption on DIII-D

In modeling electron cyclotron (EC) waves for heating (ECH) and current drive (ECCD) applications, the standard approach describes wave propagation using geometric optic ray tracing with cold plasma dispersion and wave absorption using a relativistic warm plasma expression. However, recent vertical O-mode transmission measurements on Tore Supra indicate that wave trajectories near the fundamental resonance frequency can significantly deviate from predictions of cold plasma analysis. The experim… more

Date: April 1, 1997

Creator: Lin-Liu, Y. R.; Luce, T. C.; Chiu, S. C.; Miller, R. L. & Prater, R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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2 MW 110 GHz ECH heating system for DIII-D

A 2 MW 110 GHz ECH system using Varian 0.5 MW gyrotrons is under construction for use on the DIII-D tokamak by late 1991. Most of the components are being design and fabricated at General Atomics, including the gyrotron tanks, superconducting magnets, and transmission line. These components are intended for operation with 10 second pulses and, in the future, with 1 MW gyrotrons. 6 refs., 5 figs.

Date: September 1990

Creator: Moeller, C.; Prater, R.; Callis, R.; Remsen, D.; Doane, J.; Cary, W. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Increased Stable Beta in Diii-D by Suppression of a Neoclassical Tearing Mode Using Electron Cyclotron Current Drive and Active Feedback

OAK A271 INCREASED STABLE BETA IN DIII-D BY SUPPRESSION OF A NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE AND ACTIVE FEEDBACK. In DIII-D, the first real-time active control of the electron cyclotron current drive stabilization of a neoclassical tearing mode (here m/n=3/2) is demonstrated. The plasma control system is put into a search and suppress mode to align the ECCD with the island by making either small rigid radial position shifts (of order 1 cm) of the entire plasma (… more

Date: September 1, 2002

Creator: Lahaye, R. J.; Humphreys, D. A.; Lohr, J.; Luce, T. C.; Perkins, F. W.; Petty, C. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Applications of fast wave in spherical tokamaks

In spherical tokamaks (ST), the magnetic field strength varies over a wide range across the plasma, and at high betas it deviates significantly from the 1/R dependence of conventional tokamaks. This, together with the high density expected in ST, poses challenging problems for RF heating and current drive. In this paper, the authors investigate the various possible applications of fast waves (FW) in ST. The adjoint technique of calculating current drive is implemented in the raytracing code CUR… more

Date: April 1, 1997

Creator: Chiu, S. C.; Chan, V. S.; Lin-Liu, Y. R.; Miller, R. L.; Prater, R. & Politzer, P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Polarization, propagation, and deposition measurements during ECCD experiments on the DIII-D tokamak

The power deposition profiles for different poloidal and toroidal launch angles have been determined by modulating the ECH power and measuring the electron temperature response. The peak of the measured power density follows the poloidal steering of the ECH launcher, and perpendicular launch gives a narrower deposition profile than does oblique (current drive) launch. The difference in wave refraction between X-mode and O-mode allows positive identification of an unwanted O-mode component of th… more

Date: March 1, 1999

Creator: Petty, C. C.; Luce, T. C.; Lin-Liu, Y. R.; Lohr, J.; Prater, R. & Austin, M. E.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Physics of Elctron Cyclotron Current Drive on Diii-D

OAK A271 PHYSICS OF ELCTRON CYCLOTRON CURRENT DRIVE ON DIII-D. Recent experiments on the DIII-D tokamak have focused on determining the effect of trapped particles on the electron cyclotron current drive (ECCD) efficiency. The measured ECCD efficiency increases as the deposition location is moved towards the inboard midplane or towards smaller minor radius for both co and counter injection. The measured ECCD efficiency also increases with increasing electron density and/or temperature. The expe… more

Date: September 1, 2002

Creator: Petty, C. C.; Prater, R.; Luce, T. C.; Ellis, R. A.; Harvey, R. W.; Kinsey, J. E. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Complete Suppression of the M=2/N-1 Neoclassical Tearing Mode Using Electron Cyclotron Current Drive on Diii-D

A271 COMPLETE SUPPRESSION OF THE M=2/N-1 NEOCLASSICAL TEARING MODE USING ELECTRON CYCLOTRON CURRENT DRIVE ON DIII-D. The first suppression of the important and deleterious m=2/n=1 neoclassical tearing mode (NTM) is reported using electron cyclotron current drive (ECCD) to replace the ''missing'' bootstrap current in the island O-point. Experiments on the DIII-D tokamak verify the maximum shrinkage of the m=2/n=1 island occurs when the ECCD location coincides with the q = 2 surface. The DIII-D p… more

Date: March 1, 2003

Creator: Petty, C. C.; Lahaye, L. A.; Luce, T. C.; Humphreys, D. A.; Hyatt, A. W.; Prater, R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department