Vertical control of DIII-D discharges with strong negative triangularity

Nelson, A. O.; Hyatt, A.; Wehner, W.; Welander, A.; Paz-Soldan, C.; Osborne, T.; Anand, H.; Thome, K. E.

doi:10.1088/1361-6587/acbe65

Vertical control of DIII-D discharges with strong negative triangularity

Journal Article · Fri Mar 03 00:00:00 EST 2023 · Plasma Physics and Controlled Fusion

DOI:https://doi.org/10.1088/1361-6587/acbe65· OSTI ID:1969997

^[1]; Hyatt, A. ^[2]; Wehner, W. ^[2]; Welander, A. ^[2]; ^[3]; Osborne, T. ^[2]; Anand, H. ^[2]; ^[2]

Columbia Univ., New York, NY (United States); General Atomics
General Atomics, San Diego, CA (United States)
Columbia Univ., New York, NY (United States)

Through predictive modeling validated by a series of experiments on DIII-D, the vertical stability of low β diverted plasmas with strong negative triangularity (NT) ($$\delta\sim-0.6$$) is assessed. As a result of their unique magnetic geometry, NT plasmas feature larger Shafranov shifts and more elongated inner flux surfaces than positive triangularity counterparts, typically leading to enhanced vertical instability growth rates. However, coupling with the non-conformal vessel DIII-D wall reduces these growth rates to controllable values, providing a path forward for stabilizing strongly NT plasma with a diverted geometry. These discharges are used to validate GSdesign (part of the TokSys code suite) stability calculations in strong NT plasmas on DIII-D, with errors of no more than ~20% observed between modeled and experimentally measured growth rates. Additions of diagnostic noise and power supply tuning to the TokSys model are needed to accurately capture the time dependence of DIII-D NT discharges, assisting with the design of control schemes specific to the DIII-D poloidal field coils. Lastly, implications of these results on a future NT reactor are briefly described.

View Accepted Manuscript (DOE)

Research Organization:: Columbia Univ., New York, NY (United States); General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC) Fusion Energy Sciences (FES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF)

Grant/Contract Number:: FC02-04ER54698; SC0022270

OSTI ID:: 1969997

Alternate ID(s):: OSTI ID: 1991604

Journal Information:: Plasma Physics and Controlled Fusion, Journal Name: Plasma Physics and Controlled Fusion Journal Issue: 4 Vol. 65; ISSN 0741-3335

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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