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Title: Advanced control of neutral beam injected power in DIII-D

Abstract

In the DIII-D tokamak, one of the most powerful techniques to control the density, temperature and plasma rotation is by eight independently modulated neutral beam sources with a total power of 20 MW. The rapid modulation requires a high degree of reproducibility and precise control of the ion source plasma and beam acceleration voltage. Recent changes have been made to the controls to provide a new capability to smoothly vary the beam current and beam voltage during a discharge, while maintaining the modulation capability. The ion source plasma inside the arc chamber is controlled through feedback from the Langmuir probes measuring plasma density near the extraction end. To provide the new capability, the plasma control system (PCS) has been enabled to change the Langmuir probe set point and the beam voltage set point in real time. When the PCS varies the Langmuir set point, the plasma density is directly controlled in the arc chamber, thus changing the beam current (perveance) and power going into the tokamak. Alternately, the PCS can sweep the beam voltage set point by 20 kV or more and adjust the Langmuir probe setting to match, keeping the perveance constant and beam divergence at a minimum. Thismore » changes the beam power and average neutral particle energy, which changes deposition in the tokamak plasma. The ion separating magnetic field must accurately match the beam voltage to protect the beam line. To do this, the magnet current control accurately tracks the beam voltage set point. In conclusion, these new capabilities allow continuous in-shot variation of neutral beam ion energy to complement« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
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  1. General Atomics, San Diego, CA (United States)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Nuclear Energy (NE); USDOE Office of Science (SC), Fusion Energy Sciences (FES)
OSTI Identifier:
1374822
Alternate Identifier(s):
OSTI ID: 1631800
Grant/Contract Number:  
FC02-04ER54698; AC02-09CH11466
Resource Type:
Accepted Manuscript
Journal Name:
Fusion Engineering and Design
Additional Journal Information:
Journal Volume: 123; Journal ID: ISSN 0920-3796
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; Neutral beam; High voltage; Control

Citation Formats

Pawley, Carl J., Crowley, Brendan J., Pace, David C., Rauch, Joseph M., Scoville, John T., Kellman, Daniel H., and Kellman, Arnold G. Advanced control of neutral beam injected power in DIII-D. United States: N. p., 2017. Web. doi:10.1016/j.fusengdes.2017.02.106.
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Pawley, Carl J., Crowley, Brendan J., Pace, David C., Rauch, Joseph M., Scoville, John T., Kellman, Daniel H., & Kellman, Arnold G. Advanced control of neutral beam injected power in DIII-D. United States. https://doi.org/10.1016/j.fusengdes.2017.02.106
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Pawley, Carl J., Crowley, Brendan J., Pace, David C., Rauch, Joseph M., Scoville, John T., Kellman, Daniel H., and Kellman, Arnold G. Thu . "Advanced control of neutral beam injected power in DIII-D". United States. https://doi.org/10.1016/j.fusengdes.2017.02.106. https://www.osti.gov/servlets/purl/1374822.
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@article{osti_1374822,
title = {Advanced control of neutral beam injected power in DIII-D},
author = {Pawley, Carl J. and Crowley, Brendan J. and Pace, David C. and Rauch, Joseph M. and Scoville, John T. and Kellman, Daniel H. and Kellman, Arnold G.},
abstractNote = {In the DIII-D tokamak, one of the most powerful techniques to control the density, temperature and plasma rotation is by eight independently modulated neutral beam sources with a total power of 20 MW. The rapid modulation requires a high degree of reproducibility and precise control of the ion source plasma and beam acceleration voltage. Recent changes have been made to the controls to provide a new capability to smoothly vary the beam current and beam voltage during a discharge, while maintaining the modulation capability. The ion source plasma inside the arc chamber is controlled through feedback from the Langmuir probes measuring plasma density near the extraction end. To provide the new capability, the plasma control system (PCS) has been enabled to change the Langmuir probe set point and the beam voltage set point in real time. When the PCS varies the Langmuir set point, the plasma density is directly controlled in the arc chamber, thus changing the beam current (perveance) and power going into the tokamak. Alternately, the PCS can sweep the beam voltage set point by 20 kV or more and adjust the Langmuir probe setting to match, keeping the perveance constant and beam divergence at a minimum. This changes the beam power and average neutral particle energy, which changes deposition in the tokamak plasma. The ion separating magnetic field must accurately match the beam voltage to protect the beam line. To do this, the magnet current control accurately tracks the beam voltage set point. In conclusion, these new capabilities allow continuous in-shot variation of neutral beam ion energy to complement},
doi = {10.1016/j.fusengdes.2017.02.106},
journal = {Fusion Engineering and Design},
number = ,
volume = 123,
place = {United States},
year = {Thu Mar 23 00:00:00 EDT 2017},
month = {Thu Mar 23 00:00:00 EDT 2017}
}
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Journal Article:
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Publisher's Version of Record
https://doi.org/10.1016/j.fusengdes.2017.02.106
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Works referenced in this record:

Overview of recent experimental results from the DIII-D advanced tokamak program
journal, December 2003

DIII-D research to address key challenges for ITER and fusion energy
journal, July 2015

Rotation of a Neutral Beamline to Obtain Counter-Injection on the DIII-D Tokamak
journal, October 2007

Status of the ITER heating neutral beam system
journal, March 2009

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    Works referencing / citing this record:

    Feedback control of stored energy and rotation with variable beam energy and perveance on DIII-D
    journal, May 2019

    Dynamic neutral beam current and voltage control to improve beam efficacy in tokamaks
    journal, May 2018

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    • DOI: 10.1063/1.5016160
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