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in creator/contributor: "WALKER,M.L"

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Active Filter Hardware Design & Performance for the DIII-D Plasma Control System

OAK-B135 The digital plasma control system (PCS), currently in operation on the DIII-D tokamak, requires inputs from a large number of sensors. Due to the nature of the digitizers and the relative noisy environment from which these signals are derived, each of the 32 signals must be conditioned via an active filter. Two different types of filters, Chebyshev and Bessel with fixed frequencies: 100 Hz Bessel was used for filtering the motional Stark effect diagnostic data. 800 Hz Bessel was design… more

Date: October 1, 2003

Creator: Sellers, D.; Ferron, J. R.; Walker, M. L. & Broesch, J. D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Status of DIII-D plasma control

A key component of the DIII-D Advanced Tokamak and Radiative Divertor Programs is the development and implementation of methods to actively control a large number of plasma parameters. These parameters include plasma shape and position, total stored energy, density, rf loading resistance, radiated power and more detailed control of the current profile. To support this research goal, a flexible and easily expanded digital control system has been developed and implemented. We have made parallel p… more

Date: October 1, 1995

Creator: Walker, M. L.; Ferron, J. R. & Penaflor, B.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Control of plasma poloidal shape and position in the DIII-D tokamak

Historically, tokamak control design has been a combination of theory driving an initial control design and empirical tuning of controllers to achieve satisfactory performance. This approach was in line with the focus of past experiments on simply obtaining sufficient control to study many of the basic physics issues of plasma behavior. However, in recent years existing experimental devices have required increasingly accurate control. New tokamaks such as ITER or the eventual fusion power plant… more

Date: November 1, 1997

Creator: Walker, M. L.; Humphreys, D. A. & Ferron, J. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Multivariable shape control development on the DIII-D tokamak

In this paper, the authors describe recent work on plasma shape and position control at DIII-D. This control consists of two equally challenging problems--the problem of identifying what the plasma actually looks like in real time, i.e. measuring the parameters to be controlled, and the task of determining the feedback algorithm which best controls these plasma parameters in a multiple input-output system. Recent implementation of the EFIT plasma equilibrium reconstruction algorithm in real tim… more

Date: November 1, 1997

Creator: Walker, M. L.; Humphreys, D. A. & Ferron, J. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A structured architecture for advanced plasma control experiments

Recent new and improved plasma control regimes have evolved from enhancements to the systems responsible for managing the plasma configuration on the DIII-D tokamak. The collection of hardware and software components designed for this purpose is known at DIII-D as the Plasma Control System or PCS. Several new user requirements have contributed to the rapid growth of the PCS. Experiments involving digital control of the plasma vertical position have resulted in the addition of new high performan… more

Date: October 1, 1996

Creator: Penaflor, B. G.; Ferron, J. R. & Walker, M. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Automated Fault Detection for DIII-D Tokamak Experiments

An automated fault detection software system has been developed and was used during 1999 DIII-D plasma operations. The Fault Identification and Communication System (FICS) executes automatically after every plasma discharge to check dozens of subsystems for proper operation and communicates the test results to the tokamak operator. This system is now used routinely during DIII-D operations and has led to an increase in tokamak productivity.

Date: November 1, 1999

Creator: Walker, M. L.; Scoville, J. T.; Johnson, R. D.; Hyatt, A. W. & Lee, J.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A hybrid digital-analog long pulse integrator

A digital-analog integrator has been developed for use with inductive magnetic sensors in long-pulse tokamaks. Continuous compensation of input offsets is accomplished by alternating analog-to-digital convertor samples from the sensor and a dummy load, while an RC network provides passive integration between samples. Typically a sampling rate of 10 kHz is used. In operational tests on the DIII-D tokamak, digital and analog integration of tokamak data show good agreement. The output drift error … more

Date: May 1, 1996

Creator: Strait, E. J.; Broesch, J. D.; Snider, R. T. & Walker, M. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Current status of DIII-D real-time digital plasma control

This paper describes the current status of real-time digital plasma control for the DIII-D tokamak. The digital plasma control system (PCS) has been in place at DIII-D since the early 1990s and continues to expand and improve in its capabilities to monitor and control plasma parameters for DIII-D fusion science experiments. The PCs monitors over 200 tokamak parameters from the DIII-D experiment using a real-time data acquisition system that acquires a new set of samples once every 60 {micro}s. … more

Date: June 1, 1999

Creator: Penaflor, B. G.; Piglowski, D. A.; Ferron, J. R. & Walker, M. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

A flexible software architecture for tokamak discharge control systems

The software structure of the plasma control system in use on the DIII-D tokamak experiment is described. This system implements control functions through software executing in real time on one or more digital computers. The software is organized into a hierarchy that allows new control functions needed to support the DIII-D experimental program to be added easily without affecting previously implemented functions. This also allows the software to be portable in order to create control systems … more

Date: October 1, 1996

Creator: Ferron, J. R.; Pentaflor, B.; Walker, M. L.; Moller, J. & Butner, D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Improving plasma shaping accuracy through consolidation of control model maintenance, diagnostic calibration, and hardware change control

With the advent of more sophisticated techniques for control of tokamak plasmas comes the requirement for increasingly more accurate models of plasma processes and tokamak systems. Development of accurate models for DIII-D power systems, vessel, and poloidal coils is already complete, while work continues in development of general plasma response modeling techniques. Increased accuracy in estimates of parameters to be controlled is also required. It is important to ensure that errors in support… more

Date: December 1, 1995

Creator: Baggest, D. S.; Rothweil, D. A.; Pang, S.; Walker, M. L. & Nerem, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development of a Closed Loop Simulator for Poloidal Field Control in DIII-D

The design of a model-based simulator of the DIII-D poloidal field system is presented. The simulator is automatically configured to match a particular DIII-D discharge circuit. The simulator can be run in a data input mode, in which prior acquired DIII-D shot data is input to the simulator, or in a stand-alone predictive mode, in which the model operates in closed loop with the plasma control system. The simulator is used to design and validate a multi-input-multi-output controller which has b… more

Date: November 1, 1999

Creator: Leuer, J. A.; Walker, M. L.; Humphreys, D. A.; Ferron, J. R.; Nerem, A. & Penaflor, B. G.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Real time equilibrium reconstruction for control of the discharge in the DIII-D tokamak

Optimum performance of a tokamak discharge requires accurate feedback control of many of the discharge parameters. For this to be possible, the values of these parameters must be accurately measured. The values of many discharge parameters, such as shape and safety factor profile, are not directly measured but can be evaluated from the available diagnostic data: magnetic field and flux measurements, for example. The most complete evaluation comes from a least squares fit of the diagnostic data … more

Date: July 1, 1997

Creator: Ferron, J. R.; Walker, M. L.; Lao, L. L.; Penaflor, B. G.; St. John, H. E.; Humphreys, D. A. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Integrated Plasma Control for Advanced Tokamaks

OAK-B135 Advanced tokamaks (AT) are distinguished from conventional tokamaks by their high degree of shaping, achievement of profiles optimized for high confinement and stability characteristics, and active stabilization of MHD instabilities to attain high values of normalized beta and confinement. These high performance fusion devices thus require accurate regulation of the plasma boundary, internal profiles, pumping, fueling, and heating, as well as simultaneous and well-coordinated MHD contr… more

Date: October 1, 2003

Creator: Humphreys, D. A.; Ferron, J. R.; Johnson, R .D; Leuer, J. A.; Penaflor, B. G.; Walker, M. L. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Diii-D Plasma Control Simulation Environment

OAK-B135 Many advanced have been made to the DIII-D plasma control simulation environment since the previously developed hardware-in-the-loop plasma shape simulation capability was reported. In the present paper they summarize the major improvements to this simulation environment, including, introduction of the non-linear plasma evolution code DINA. Comparisons with DIII-D experimental results are presented. Recent model developments in advanced neoclassical tearing mode (NTM) and resistive wal… more

Date: October 1, 2003

Creator: Leuer, J. A.; Deranian, R. D.; Ferron, J. R.; Humphreys, D. A.; Johnson, R. D.; Penaflor, B. G. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Advanced Tokamak Operation Using the DIII-D Plasma Control System

A271 ADVANCED TOKAMAK OPERATION USING THE DIII-D PLASMA CONTROL SYSTEM. The principal focus of experimental operations in the DIII-D tokamak is the advanced tokamak (AT) regime to achieve, which requires highly integrated and flexible plasma control. In a high performance advanced tokamak, accurate regulation of the plasma boundary, internal profiles, pumping, fueling, and heating must be well coordinated with MHD control action to stabilize such instabilities as tearing modes and resistive wal… more

Date: October 1, 2002

Creator: Humphreys, D. A.; Ferron, J. R.; Garofalo, A. M.; Hyatt, A. W.; Jernigan, T. C.; Johnson, R. D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Resistive Wall Stabilization of High Beta Plasmas in DIII-D

OAK A271 RESISTIVE WALL STABILIZATION OF HIGH BETA PLASMAS IN DIII-D. Recent DIII-D experiments show that ideal kink modes can be stabilized at high beta by a resistive wall, with sufficient plasma rotation. However, the resonant response by a marginally stable resistive wall mode to static magnetic field asymmetries can lead to strong damping of the rotation. Careful reduction of such asymmetries has allowed plasmas with beta well above the ideal MHD no-wall limit, and approaching the ideal-wa… more

Date: September 1, 2002

Creator: Strait, E. J.; Bialek, J.; Bogatu, N.; Chance, M.; Chu, M. S.; Edgell, D. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Active Feedback Stabilization of the Resistive Wall Mode on the DIII-D Device

A proof of principle magnetic feedback stabilization experiment has been carried out to suppress the resistive wall mode (RWM), a branch of the ideal magnetohydrodynamic (MHD) kink mode under the influence of a stabilizing resistive wall, on the DIII-D tokamak device. The RWM was successfully suppressed and the high beta duration above the no wall limit was extended to more than 50 times the resistive wall flux diffusion time. It was observed that the mode structure was well preserved during th… more

Date: November 1, 2000

Creator: Okabayashi, M; Bialek, J; Chance, M S; Chu, M S; Fredrickson, E D; Garofalo, A M et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

ACTIVE FEEDBACK STABILZATION OF THE RESISTIVE WALL MODE ON THE DIII-D DEVICE

A proof of principle magnetic feedback stabilization experiment has been carried out to suppress the resistive wall mode (RWM), a branch of the ideal magnetohydrodynamic (MHD) kink mode under the influence of a stabilizing resistive wall, on the DIII-D tokamak device [Plasma Phys. and Contr. Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159]. The RWM was successfully suppressed and the high beta duration above the no wall limit was extended to more than 50 times the res… more

Date: November 1, 2000

Creator: Okabayashi, M.; Bialek, J.; Chance, M. S.; Chu, M. S.; Fredrickson, E. D.; Garofalo, A. M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

CONTROL OF MHD STABILITY IN DIII-D ADVANCED TOKAMAK DISCHARGES

OAK-B135 Advanced tokamak research in DIII-D seeks to optimize the tokamak approach for fusion energy production, leading to a compact, steady state power source. High power density implies operation at high toroidal beta, {beta}{sub T}=<p>2{micro}{sub 0}/B{sub T}{sup 2}, since fusion power density increases roughly as the square of the plasma pressure. Steady-state operation with low recirculating power for current drive implies operation at high poloidal beta, {beta}{sub P} = <p>2… more

Date: June 1, 2003

Creator: Strait, E. J.; Bialek, J.; Chance, M. S.; Chu, M. S.; Edgell, D. H.; Ferron, J. R. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department