Regulation of the central safety factor and normalized beta under low NBI torque in DIII-D

Pajares, A.; Schuster, E.; Wehner, W. P.; Burrell, K. H.; Ferron, J. R.; Walker, M. L.; Humphreys, D. A.

doi:10.1016/j.fusengdes.2022.113363

Regulation of the central safety factor and normalized beta under low NBI torque in DIII-D

Journal Article · Fri Dec 09 00:00:00 EST 2022 · Fusion Engineering and Design

DOI:https://doi.org/10.1016/j.fusengdes.2022.113363· OSTI ID:1963840

^[1]; Schuster, E. ^[2]; Wehner, W. P. ^[3]; Burrell, K. H. ^[3]; Ferron, J. R. ^[3]; Walker, M. L. ^[3]; ^[3]

Lehigh Univ., Bethlehem, PA (United States); General Atomics
Lehigh Univ., Bethlehem, PA (United States)
General Atomics, San Diego, CA (United States)

An algorithm has been designed to simultaneously control the central safety factor (q₀) and normalized beta (β_N) while ensuring near-zero torque from the neutral beam injection in DIII-D. Feedback control of q₀ and β_N in tokamaks can be beneficial due to the close relationship that these variables have with plasma performance and magneto-hydrodynamic stability. In addition, low neutral-beam-torque conditions are of special interest in present devices because future burning-plasma tokamaks such as ITER will most likely operate at very low plasma rotation. The control synthesis of the algorithm presented in this work is based on a linearized, one-dimensional (1D) model of the current-profile dynamics coupled with a zero-dimensional (0D) plasma-energy balance. The actuators considered are neutral beam injection and electron-cyclotron heating and current drive, and discrete logic determines the neutral-beam injection powers that deliver near-zero torque. Here, the algorithm has been tested in nonlinear, 1D simulations using COTSIM (Control-Oriented Transport SIMulator) and in DIII-D experiments, demonstrating satisfactory performance.

View Accepted Manuscript (DOE)

Research Organization:: General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

Grant/Contract Number:: FC02-04ER54698; SC0010661

OSTI ID:: 1963840

Journal Information:: Fusion Engineering and Design, Journal Name: Fusion Engineering and Design Vol. 187; ISSN 0920-3796

Publisher:: ElsevierCopyright Statement

Country of Publication:: United States

Language:: English

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