Profile Shape Parameterization of JET Electron Temperature and Density Profiles

TL;DR

This paper models the shape of electron temperature and density profiles in JET using log-additive models, revealing how control variables like heating type, magnetic field, and density ratios influence profile shapes.

Contribution

It introduces a parameterization method for JET profiles using log-additive models and identifies key control variables affecting profile shapes.

Findings

Density profile depends on $ar{n}/B_t$ ratio.

Temperature profile shape varies with heating type and $Z_{eff}$.

Density profile broadens with increased $ar{n}/q_{95}$ and current.

Abstract

The temperature and density profiles of the Joint European Torus are parameterized using log-additive models in the control variables. Predictive error criteria are used to determine which terms in the log-linear model to include. The density and temperature profiles are normalised to their line averages ($\bar{n}$ and $\bar{T}$). The normalised Ohmic density shape depends primarily on the parameter $\bar{n}/B_t$, where $B_t$ is the toroidal magnetic field. Both the Low-mode (L-mode) and edge localized mode-free (ELM-free) high mode (H-mode) temperature profile shapes depend strongly on the type of heating power, with ion cyclotron resonant heating producing a more peaked profile than neutral beam injection. Given the heating type dependence, the L-mode temperature shape is nearly independent of the other control variables. The H-mode temperature shape broadens as the effective charge, $Z_{eff}$, increases. The line average L-mode temperature scales as $B_t^{.96}$(Power per particle)$^{.385}$. The L-mode normalized density shape depends primarily on the ratio of line average density, $\bar{n}$, to the edge safety factor, $q_{95}$. As $\bar{n}/q_{95}$ increases, the profile shape broadens. The current, $I_p$, is the most important control variable for the normalized H-mode density. As the current increases, the profile broadens and the gradient at the edge sharpens. Increasing the heating power, especially the ion cyclotron resonant heating, or decreasing the average density, peaks the H-mode density profile slightly.