Integrated modeling of highly radiative plasmas with negative triangularity shaping*

A reactor-class fusion device with high radiation fraction from noble gas impurities and with negative triangularity (NT) shaping could have confinement on the scale of an H-mode plasma while intrinsically avoiding edge localized modes (ELMs). Highly radiative positive triangularity (PT) plasmas have demonstrated enhanced confinement while remaining in L-mode by dispersing heat from the core before it reaches the edge [1]. Separately, NT plasmas have demonstrated enhanced confinement in low radiation fraction plasmas [2]. In this work, we use the integrated modeling code STEP (Stability Transport Equilibrium Pedestal) to self-consistently study the core of highly radiative plasmas with noble gas radiators in both PT and NT configurations. Our workflow is validated with experimental data from DIII-D. We extend our analysis to reactor-relevant conditions and study fusion power balance in the PT and NT model reactors ARCH [3] and MANTA, respectively. We find that there is an impurity fraction that optimizes confinement before the plasma undergoes radiative collapse in both PT and NT.

[1] S Coda et al 2022 Plasma Phys. Control. Fusion 64 014004

[2] A O Nelson et al 2022 Nucl. Fusion 62 096020

[3] S J Frank et al 2022 Nucl. Fusion 62 126036