Equilibrium reconstruction of DIII-D plasmas using predictive modeling of the pressure profile

Journal Article · Fri Jun 03 00:00:00 EDT 2022 · Physics of Plasmas

DOI:https://doi.org/10.1063/5.0078935· OSTI ID:1871041

Kinsey, J. E. ; Lao, L. L. ; Meneghini, O. ; Candy, J. ; Snyder, P. B. ; Staebler, G. M.

New workflows have been developed for predictive modeling of magnetohydrodynamic (MHD) equilibrium in tokamak plasmas. The goal of this work is to predict the MHD equilibrium in tokamak discharges without having measurements of the kinetic profiles. The workflows include a cold start tool, which constructs all the profiles and power flows needed by transport codes; a Grad–Shafranov equilibrium solver; and various codes for the sources and sinks. For validation purposes, a database of DIII-D tokamak discharges has been constructed that is comprised of scans in the plasma current, toroidal magnetic field, and triangularity. Initial efforts focused on developing a workflow utilizing an empirically derived pressure model tuned to DIII-D discharges with monotonic safety factor profiles. This workflow shows good agreement with experimental kinetic equilibrium calculations, but is limited in that it is a single fluid (equal ion and electron temperatures) model and lacks H-mode pedestal predictions. The best agreement with the H-mode database is obtained using a theory-based workflow utilizing pressure profile predictions from a coupled TGLF turbulent transport and EPED pedestal models together with external magnetics and Motional Stark Effect (MSE) data to construct the equilibrium. Here, we obtain an average root mean square error of 5.1% in the safety factor profile when comparing the predicted and experimental kinetic equilibrium. We also find good agreement with the plasma stored energy, internal inductance, and pressure profiles. Including MSE data in the theory-based workflow results in noticeably improved agreement with the q-profiles in high triangularity discharges in comparison with the results obtained with magnetic data only. The predictive equilibrium workflow is expected to have wide applications in experimental planning, between-shot analysis, and reactor studies.

• Sponsoring Organization: USDOE
• Grant/Contract Number: FG02-95ER54309; FC02-04ER54698
• OSTI ID: 1871041
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Vol. 29 Journal Issue: 6; ISSN 1070-664X
• Publisher: American Institute of Physics
• Country of Publication: United States
• Language: English