AC compensation of 3D magnetic diagnostic signals in DIII-D and National Spherical Torus Experiment-Upgrade (NSTX-U) for real-time application
Abstract
A time domain algorithm has been developed to remove the vacuum pickup generated by both coil current (DC) and induced vessel current (AC) in real time from three dimensional (3D) magnetic diagnostic signals in the National Spherical Torus Experiment-Upgrade (NSTX-U) and DIII-D tokamaks. The possibility of detecting 3D plasma perturbations in real time is essential in modern and future tokamaks to avoid and control MHD instabilities. The presence of vacuum field pickup, due to toroidally asymmetric (3D) coils or to misalignment between sensors and axisymmetric (2D) coils, pollutes the measured plasma 3D field, making the detection of the magnetic field produced by the plasma challenging. Although the DC coupling between coils and sensors can be easily calculated and removed, the AC part is more difficult. Here, an algorithm based on a layered low-pass filter approach for the AC compensation and its application for DIII-D and NSTX-U data is presented, showing that this method reduces the vacuum pickup to the noise level. Comparison of plasma response measurements with and without vacuum compensation shows that accurate mode locking detection and plasma response identification require precise AC and DC compensations.
- Authors:
-
[1];
[2];
[1];
[3];
[1];
[4]
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
- Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- General Atomics, San Diego, CA (United States)
- Publication Date:
- Research Org.:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)
- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Fusion Energy Sciences (FES)
- OSTI Identifier:
- 1890809
- Alternate Identifier(s):
- OSTI ID: 1890120; OSTI ID: 1890255
- Report Number(s):
- LLNL-JRNL-839011
Journal ID: ISSN 0034-6748; 1058945; TRN: US2310088
- Grant/Contract Number:
- AC52-07NA27344; AC02-09CH11466; FC02-04ER54698; NA0003525
- Resource Type:
- Accepted Manuscript
- Journal Name:
- Review of Scientific Instruments
- Additional Journal Information:
- Journal Volume: 93; Journal Issue: 9; Journal ID: ISSN 0034-6748
- Publisher:
- American Institute of Physics (AIP)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; plasma confinement; magnetic field sensors; signal processing; eddy current; fusion energy; tokamaks; plasma diagnostics
Citation Formats
Munaretto, S., Myers, C. E., Gerhardt, S. P., Logan, N. C., Menard, J. E., and Strait, E. J. AC compensation of 3D magnetic diagnostic signals in DIII-D and National Spherical Torus Experiment-Upgrade (NSTX-U) for real-time application. United States: N. p., 2022.
Web. doi:10.1063/5.0101630.
Munaretto, S., Myers, C. E., Gerhardt, S. P., Logan, N. C., Menard, J. E., & Strait, E. J. AC compensation of 3D magnetic diagnostic signals in DIII-D and National Spherical Torus Experiment-Upgrade (NSTX-U) for real-time application. United States. https://doi.org/10.1063/5.0101630
Munaretto, S., Myers, C. E., Gerhardt, S. P., Logan, N. C., Menard, J. E., and Strait, E. J. Thu .
"AC compensation of 3D magnetic diagnostic signals in DIII-D and National Spherical Torus Experiment-Upgrade (NSTX-U) for real-time application". United States. https://doi.org/10.1063/5.0101630. https://www.osti.gov/servlets/purl/1890809.
@article{osti_1890809,
title = {AC compensation of 3D magnetic diagnostic signals in DIII-D and National Spherical Torus Experiment-Upgrade (NSTX-U) for real-time application},
author = {Munaretto, S. and Myers, C. E. and Gerhardt, S. P. and Logan, N. C. and Menard, J. E. and Strait, E. J.},
abstractNote = {A time domain algorithm has been developed to remove the vacuum pickup generated by both coil current (DC) and induced vessel current (AC) in real time from three dimensional (3D) magnetic diagnostic signals in the National Spherical Torus Experiment-Upgrade (NSTX-U) and DIII-D tokamaks. The possibility of detecting 3D plasma perturbations in real time is essential in modern and future tokamaks to avoid and control MHD instabilities. The presence of vacuum field pickup, due to toroidally asymmetric (3D) coils or to misalignment between sensors and axisymmetric (2D) coils, pollutes the measured plasma 3D field, making the detection of the magnetic field produced by the plasma challenging. Although the DC coupling between coils and sensors can be easily calculated and removed, the AC part is more difficult. Here, an algorithm based on a layered low-pass filter approach for the AC compensation and its application for DIII-D and NSTX-U data is presented, showing that this method reduces the vacuum pickup to the noise level. Comparison of plasma response measurements with and without vacuum compensation shows that accurate mode locking detection and plasma response identification require precise AC and DC compensations.},
doi = {10.1063/5.0101630},
journal = {Review of Scientific Instruments},
number = 9,
volume = 93,
place = {United States},
year = {Thu Sep 29 00:00:00 EDT 2022},
month = {Thu Sep 29 00:00:00 EDT 2022}
}
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