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Title: Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak

A new servomotor drive system has been developed for the horizontal reciprocating probe on the Alcator C-Mod tokamak. Real-time measurements of plasma temperature and density—through use of a mirror Langmuir probe bias system—combined with a commercial linear servomotor and controller enable self-adaptive position control. Probe surface temperature and its rate of change are computed in real time and used to control probe insertion depth. It is found that a universal trigger threshold can be defined in terms of these two parameters; if the probe is triggered to retract when crossing the trigger threshold, it will reach the same ultimate surface temperature, independent of velocity, acceleration, or scrape-off layer heat flux scale length. Finally, in addition to controlling the probe motion, the controller is used to monitor and control all aspects of the integrated probe drive system.
Authors:
ORCiD logo [1] ; ORCiD logo [1] ;  [1] ;  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
Publication Date:
Grant/Contract Number:
FC02-99ER54512
Type:
Accepted Manuscript
Journal Name:
Review of Scientific Instruments
Additional Journal Information:
Journal Volume: 88; Journal Issue: 7; Journal ID: ISSN 0034-6748
Publisher:
American Institute of Physics (AIP)
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
OSTI Identifier:
1474327
Alternate Identifier(s):
OSTI ID: 1367935

Brunner, D., Kuang, A. Q., LaBombard, B., and Burke, W.. Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak. United States: N. p., Web. doi:10.1063/1.4990043.
Brunner, D., Kuang, A. Q., LaBombard, B., & Burke, W.. Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak. United States. doi:10.1063/1.4990043.
Brunner, D., Kuang, A. Q., LaBombard, B., and Burke, W.. 2017. "Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak". United States. doi:10.1063/1.4990043. https://www.osti.gov/servlets/purl/1474327.
@article{osti_1474327,
title = {Linear servomotor probe drive system with real-time self-adaptive position control for the Alcator C-Mod tokamak},
author = {Brunner, D. and Kuang, A. Q. and LaBombard, B. and Burke, W.},
abstractNote = {A new servomotor drive system has been developed for the horizontal reciprocating probe on the Alcator C-Mod tokamak. Real-time measurements of plasma temperature and density—through use of a mirror Langmuir probe bias system—combined with a commercial linear servomotor and controller enable self-adaptive position control. Probe surface temperature and its rate of change are computed in real time and used to control probe insertion depth. It is found that a universal trigger threshold can be defined in terms of these two parameters; if the probe is triggered to retract when crossing the trigger threshold, it will reach the same ultimate surface temperature, independent of velocity, acceleration, or scrape-off layer heat flux scale length. Finally, in addition to controlling the probe motion, the controller is used to monitor and control all aspects of the integrated probe drive system.},
doi = {10.1063/1.4990043},
journal = {Review of Scientific Instruments},
number = 7,
volume = 88,
place = {United States},
year = {2017},
month = {7}
}