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in subjects: "Non-Inductive Current Drive"

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Traveling wave antenna for fast wave heating and current drive in tokamaks

The traveling wave antenna for heating and current drive in the ion cyclotron range of frequencies is shown theoretically to have loading and wavenumber spectrum which are largely independent of plasma conditions. These characteristics have been demonstrated in low power experiments on the DIII-D tokamak, in which a standard four-strap antenna was converted to a traveling wave antenna through use of external coupling elements. The experiments indicate that the array maintains good impedance mat… more

Date: July 1, 1995

Creator: Ikezi, H. & Phelps, D. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Experimental studies of fast wave propagation in DIII-D

Fast Alfven waves radiated from the phased array antenna in the DIII-D tokamak and used for heating and current drive are studied by employing a B-loop array mounted on the vacuum vessel wall. The wave propagation direction controlled by the antenna phasing is clearly observed. A small divergence of the rays arising from the anisotropic nature of the fast wave is found. Comparison with a ray tracing code confirms that the ray position calculated by the code is accurate up to at least one toroid… more

Date: June 1, 1995

Creator: Ikezi, H.; Pinsker, R. I.; Chiu, S. C. & deGrassie, J. S.

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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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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High performance low and high q discharges in DIII-D

The High performance H-mode regime on DIII-D has been extended to both low q and high q (high {Beta}p) and low q operation. In high current operation, VH-mode discharges were obtained for the first time with I{sub P}(MA)/B{sub T} (T) > 1. These discharges had q{sub 95}= 3.4, H = 2.9, {Beta}{sub N}= 3, and {Beta}{sub T}{Tau}{sub E}=3%-sec. {Beta}{sub T}{Tau}{sub E} was improved by approximately 50% over previous results. These discharges were obtained with neutral beam injection during the plasm… more

Date: January 1, 1996

Creator: Osborne, T.H.; Burrell, K.H. & Chu, M.S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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[Magnetic helicity and current drive in fusion devices]. Final technical report

The research program focused on two main themes: (i) magnetic helicity and (ii) current drive by low-frequency waves. At first these themes seemed unrelated, but as time progressed, they became interwoven, and ultimately closely connected. A sub-theme is that while the MHD model of a plasma stimulates many intriguing counter-intuitive ideas for creating and sustaining magnetic confinement configurations, usually the crux of these schemes involves some sort of breakdown of MHD, i.e., involves ph… more

Date: February 2, 1998

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Reduction of toroidal rotation by fast wave power in DIII-D

The application of fast wave power in DIII-D has proven effective for both electron heating and current drive. Since the last RIF Conference FW power has been applied to advanced confinement regimes in DIII-D; negative central shear (NCS), VH- and H-modes, high {beta}{sub p}, and high-{ell}i. Typically these regimes show enhanced confinement of toroidal momentum exhibited by increased toroidal rotation velocity. Indeed, layers of large shear in toroidal velocity are associated with transport ba… more

Date: April 1, 1997

Creator: Grassie, J.S. de; Baker, D.R. & Burrell, K.H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Fast wave current drive in neutral beam heated plasmas on DIII-D

The physics of non-inductive current drive and current profile control using the fast magnetosonic wave has been demonstrated on the DIII-D tokamak. In non-sawtoothing discharges formed by neutral beam injection (NBI), the radial profile of the fast wave current drive (FWCD) was determined by the response of the loop voltage profile to co, counter, and symmetric antenna phasings, and was found to be in good agreement with theoretical models. The application of counter FWCD increased the magneti… more

Date: April 1997

Creator: Petty, C. C.; Forest, C. B. & Pinsker, R. I.

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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Design of the HHFW heating and current drive system for NSTX

The National Spherical Tokamak Experiment (NSTX) is a low aspect ratio (A = 1.25) tokamak being built at Princeton Plasma Physics Laboratory (PPPL), with major radius = 0.8 m, B{sub T} = 0.32 T and I{sub p} up to 1 MA. The machine requires on the order of 6 MW of auxiliary heating in order to test {beta} limits and it needs electron heating/current drive in order to extend the pulse length and demonstrate non-inductive startup. The high harmonic fast wave (HHFW) system, operating at 30 MHz, is … more

Date: November 1, 1998

Creator: Ryan, P. M.; Carter, M. D. & Swain, D. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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RF current drive antenna. Final report, August 15, 1993--August 14, 1995

This work represents an attempt to solve a fundamental problem with all coupling devices in tokamaks intended to launch waves in the ion cyclotron range of frequencies (ICRF), that of excessive voltage levels on the launcher and its feed lines. These voltages can lead to impurity problems in the plasma, and they determine the maximum power that can be coupled to the plasma, since it is when arcs caused by this voltage frequently occur that the power must be reduced. The approach taken is to con… more

Date: September 1, 1995

Creator: Probert, P.H.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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ICRF antenna modeling and simulation. Final report, March 1, 1993--May 31, 1996

SAIC has undergone a three year research and development program in support of the DOE Office of Fusion Energy`s (OFE) program in Ion Cyclotron Range of Frequencies (ICRF) heating of present, next generation, and future plasma fusion devices. The effort entailed advancing theoretical models and numerical simulation technology of ICRF physics and engineering issues associated predominately with, but not limited to, tokamak Ion Cyclotron Heating (ICH) and fast wave current drive (FWCD). Ion cyclo… more

Date: August 30, 1996

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Electron cyclotron current drive in DIII-D

Clear measurements of the localized current density driven by electron cyclotron waves have been made on the DIII-D tokamak. Direct evidence of the current drive is seen on the internal magnetic field measurements by motional Stark effect spectroscopy. Comparison with theoretical calculations in the collisionless limit shows the experimental current drive exceeds the predictions by a substantial amount for currents driven near the half radius. In all cases the experimental current density profi… more

Date: May 1, 1999

Creator: Luce, T. C.; Lin-Liu, Y. R.; Lohr, J. M.; Petty, C. C.; Politzer, P. A.; Prater, R. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

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4 MW upgrade to DIII-D FWCD system: System commissioning and initial operation

The initial installation of the 4 MW fast wave current drive (FWCD) upgrade started in 1992 with the purchase of two ABB/Thomcast AG rf power amplifiers. These amplifiers cover the frequency range 30 MHz to 120 MHz. A maximum output power of over 2 MW between 30 MHz and 80 MHz and 1 MW at 120 MHz were the specification requirements. The system as installed is comprised of the two mentioned rf amplifiers, coaxial transmission and matching components, rf phase and amplitude monitoring, and a SUN … more

Date: October 1995

Creator: Cary, W. P.; Callis, R. W.; de Grassie, J. S.; Harris, T. E.; O`Neill, R. C.; Pinsker, R. I. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Current profile modification with electron cyclotron current drive in the DIII-D tokamak

Proof-of-principle experiments on the suitability of electron cyclotron current drive (ECCD) for active current profile control are reported. Experiments with second harmonic extraordinary mode absorption at power levels near 1 MW have demonstrated ability to modify the current profile. This modification is manifested in changes in the internal inductance and the time at which sawteeth appear. Measurements of the local current density and internal loop voltage using high resolution motional Sta… more

Date: November 1998

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

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

RF power diagnostics and control on the DIII-D, 4 MW 30--120 MHz fast wave current drive system (FWCD)

The Fast Wave Current Drive System uses three 2 MW transmitters to drive three antennas inside the DIII-D vacuum vessel. This paper describes the diagnostics for this system. The diagnostics associated with the General Atomics Fast Wave Current Drive System allow the system tuning to be analyzed and modified on a between shot basis. The transmitters can be exactly tuned to match the plasma with only one tuning shot into the plasma. This facilitates maximum rf power utilization.

Date: October 1, 1995

Creator: Ferguson, S. W.; Allen, J. C.; Callis, R. W.; Cary, W. P. & Harris, T. E.

Item Type: Article

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

open access

Modification of the Current Profile in DIII-D by Off-Axis Electron Cyclotron Current Drive

Localized non-inductive currents due to electron cyclotron wave absorption have been measured on the DIII-D tokamak. Clear evidence of the non-inductive currents is seen on the internal magnetic field measurements by motional Stark effect spectroscopy. The magnitude and location of the non-inductive current is evaluated by comparing the total and Ohmic current profiles of discharges with and without electron cyclotron wave power. The measured current agrees with Fokker-Planck calculations near … more

Date: July 1, 1999

Creator: Luce, T. C.; Lin-Liu, Y. R.; Harvey, R. W.; Giruzzi, G.; Lohr, J. M.; Petty, C. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Confinement and stability of DIII-D negative central shear discharges

Negative central magnetic shear (NCS) discharges with {Beta}{sub N} {le} 4, H {le} 3, and up to 80% of the current non-inductively driven are reproducibly produced in the DIII-D tokamak. Strong peaking of T{sub i}, plasma rotation, and in some cases n{sub e} are observed inside the NCS region. Transport analysis shows that the core ion thermal diffusivity is substantially reduced and near the neoclassical value after the formation of the internal transport barrier. The negative central shear is… more

Date: December 1, 1995

Creator: Lao, L. L.; Burrell, K. H. & Chan, V. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Improvement of tokamak performance by injection of electrons

Concepts for improving tokamak performance by utilizing injection of hot electrons are discussed. Motivation of this paper is to introduce the research work being performed in this area and to refer the interested readers to the literature for more detail. The electron injection based concepts presented here have been developed in the CDX, CCT, and CDX-U tokamak facilities. The following three promising application areas of electron injection are described here: 1. Non-inductive current drive, … more

Date: December 1, 1992

Creator: Ono, Masayuki

Item Type: Report

Partner: UNT Libraries Government Documents Department

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Tokamak Physics Experiment poloidal field design

The Tokamak Physics Experiment (TPX) will have a poloidal field system capable of full inductive operation poloidal for approximately a 20-s flattop and, with superconducting toroidal and poloidal field coils and non-inductive current drive, it will be capable of true steady-state operation. The poloidal field design is based on the ideal MHD equilibrium model as implemented in the TEQ code developed at LLNL. The PF coils are arranged in an up-down symmetric configuration, external to the TF co… more

Date: October 6, 1993

Creator: Bulmer, R. H.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Novel current drive experiments on the CDX-U, HIT, and DIII-D Tokamaks

Two types of novel, non-inductive current drive concepts for starting-up and maintaining tokamak discharges have been developed on the CDX-U, HIT, and DIII-D Tokamaks. On CDX-U, a new, non-inductive current drive technique utilizing fully internally generated pressure driven currents has been demonstrated. The measured current density profile shows a non-hollow profile which agrees with a modeling calculation including helicity conserving non-classical current transport providing the ``seed cur… more

Date: October 1, 1992

Creator: Ono, M.; Forest, C. B.; Hwang, Y. S.; Armstrong, R. J.; Choe, W.; Darrow, D. S. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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The engineering design of the Tokamak Physics Experiment

A mission and supporting physics objectives have been developed, which establishes an important role for the Tokamak Physics Experiment (TPX) in developing the physic basis for a future fusion reactor. The design of TPX include advanced physics features, such as shaping and profile control, along with the capability of operating for very long pulses. The development of the superconducting magnets, actively cooled internal hardware, and remote maintenance will be an important technology contribu… more

Date: July 1, 1994

Creator: Schmidt, J. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

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Current profile evolution during fast wave current drive on the DIII-D tokamak

The effect of co and counter fast wave current drive (FWCD) on the plasma current profile has been measured for neutral beam heated plasmas with reversed magnetic shear on the DIII-D tokamak. Although the response of the loop voltage profile was consistent with the application of co and counter FWCD, little difference was observed between the current profiles for the opposite directions of FWCD. The evolution of the current profile was successfully modeled using the ONETWO transport code. The s… more

Date: June 1995

Creator: Petty, C. C.; Forest, C. B. & Baity, F. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department