Dmitri M Orlov | Searcharxiv

arXiv2026

Assessment of 0-D L-H Power Threshold Scaling and Regression Stability in DIII-D with Applied 3D Magnetic Fields

A database of 192 L-H transitions in DIII-D is used to assess the effects of applied three-dimensional (3D) magnetic fields on the H-mode power threshold and the stability of zero-dimensional (0-D) empirical regressions. The dataset includes nominally axisymmetric discharges and discharges with resonant or non-resonant magnetic perturbations. Filtering criteria reduce uncertainties associated with absorbed power, neutral-beam modulation, and fast-ion losses, while applied-field components are quantified using equilibrium reconstruction and spectral analysis. Measured threshold powers show substantial scatter and systematic deviations from the 2008 ITPA multi-machine scaling, including for discharges without applied perturbations. TRANSP modeling indicates that empirical estimates can substantially underpredict fast-ion losses, particularly at low plasma current and with non-axisymmetric fields. Adding global 3D-field metrics does not robustly isolate the effects of applied perturbations. A fully unconstrained regression retains a 70% residual root-mean-square error and produces nonphysical parameter dependencies, including a plasma surface-area exponent of 2.79. Extrapolations to ITER-relevant conditions consequently have broad confidence intervals. These results show that hidden-variable dependencies can strongly affect empirical threshold parameterizations even in a restricted single-machine dataset. Machine-specific conditions, local edge physics, and power-accounting uncertainties limit the predictive capability of purely 0-D scalings. Improved predictions for ITER and future devices will require better fast-ion-loss treatment and physics-based, edge-localized quantities.

physics.plasm-ph↗

arXiv2025

Predicting core transport in ITER baseline discharges with neon injections

Achieving self-consistent performance predictions for ITER requires integrated modeling of core transport and divertor power exhaust under realistic impurity conditions. We present results from the first systematic power-flow and impurity-content study for the ITER 15 MA baseline scenario constrained directly by existing SOLPS-ITER neon-seeded divertor solutions. Using the OMFIT STEP workflow, stationary temperature and density profiles are predicted with TGYRO for $1.5 \le Z_{\rm eff} \le 2.5$, and the corresponding power crossing the separatrix $P_{\rm sep}$ is evaluated. We find that $P_{\rm sep}$ varies by more than a factor of 1.7 across this scan and matches the $\sim 100$~MW SOLPS-ITER prediction when $Z_{\rm eff} \simeq 1.6$ or when auxiliary heating is reduced to $\sim 75\%$ of nominal. Rotation-sensitivity studies show that plausible variations in toroidal flow magnitude modify $P_{\rm sep}$ by $\lesssim 20\%$, while AURORA modeling confirms that charge-exchange radiation inside the separatrix is dynamically negligible under predicted ITER neutral densities. These results identify a restricted compatibility window, $Z_{\rm eff} \approx 1.6$--1.75 and $0.75 \lesssim f_{P_{\rm aux}} \le 1.0$, in which core transport predictions remain aligned with neon-seeded divertor protection targets. This self-consistent, model-constrained framework provides actionable guidance for impurity control and auxiliary-heating scheduling in early ITER operation and supports future whole-device scenario optimization.

physics.plasm-ph↗