AC compensation of 3D magnetic diagnostic signals in DIII-D and National Spherical Torus Experiment-Upgrade (NSTX-U) for real-time application

Munaretto, S.; Myers, C. E.; Gerhardt, S. P.; Logan, N. C.; Menard, J. E.; Strait, E. J.

doi:10.1063/5.0101630

Title: AC compensation of 3D magnetic diagnostic signals in DIII-D and National Spherical Torus Experiment-Upgrade (NSTX-U) for real-time application

Journal Article · Thu Sep 29 00:00:00 EDT 2022 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/5.0101630· OSTI ID:1890809

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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)

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.

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Research Organization:: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Princeton Plasma Physics Laboratory (PPPL), Princeton, NJ (United States)

Sponsoring Organization:: USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: AC52-07NA27344; AC02-09CH11466; FC02-04ER54698; NA0003525

OSTI ID:: 1890809

Alternate ID(s):: OSTI ID: 1890120; OSTI ID: 1890255

Report Number(s):: LLNL-JRNL-839011; 1058945; TRN: US2310088

Journal Information:: Review of Scientific Instruments, Vol. 93, Issue 9; ISSN 0034-6748

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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