Scalings and Plasma Profile Parameterisation of ASDEX High Density Ohmic Discharges

TL;DR

This paper presents statistical analysis of high-density Ohmic discharges in ASDEX, deriving plasma parameter scalings and profile shapes, revealing dependencies on safety factor and plasma current with implications for plasma equilibrium modeling.

Contribution

It introduces new empirical scalings for plasma energy and temperature profiles in high-density Ohmic discharges, enhancing understanding of plasma behavior in tokamaks.

Findings

Total plasma energy scales as n̄^{0.54} I_p^{0.90} and is independent of B_t.

Electron temperature peaking factor scales with q_a^{1.07}, consistent with classical resistive equilibrium.

Inner plasma profiles depend strongly on q_a, while outer profiles broaden with increasing current.

Abstract

High density ($.3 < \bar{n}/10^{20}{\rm m^{-3}} < .8$), low $q_a$ ($1.9<q_a<3.4$), Ohmic discharges from the ASDEX experiment is analysed statistically. Bulk parameter scalings and parameterised temperature and density profile shapes are presented. The total plasma kinetic energy, assuming $T_i=T_e$, scales as $\bar{n}^{\ .54\pm .01} {I_p}^{.90\pm .04 } $ and is almost independent of $B_t$. The electron temperature profile peaking factor scales as ${T_0^{3/2}/<T^{3/2}>} = .94(\pm.04){q_a}^{1.07\pm.04}$ in close agreement with the assumption of classical resistive equilibrium. In the inner half of the plasma, the inverse fall-off length for both temperature and density has a strong dependence on $q_a$, with the temperature dependence being more pronounced. Outside the half radius, the $q_a$ dependence disappears but the density profile broadens near the edge with increasing plasma current.