Investigation of the dependency of JET midplane separatrix density as a function of engineering parameters

Abstract

AbstractMidplane separatrix density is a crucial parameter in tokamaks since it strongly impacts divertor conditions. Scaling midplane separatrix density, ne, SEP, and pedestal density, ne, PED, as function of engineering parameters such as auxiliary heating Pinjected, toroidal magnetic field BT, and plasma poloidal current Ip are relevant to observe the effect of tuning these parameters on, for example, quality of confinement and divertor regime governed by ne, PED and ne, SEP, respectively. Thus, a dataset of JET H‐mode pulses performed with Iter like wall (ILW) has been analysed. Midplane density data are collected from an HRTS (high‐resolution Thomson scattering) diagnostic and ne, SEP is determined using the power balance method. Parallel heat flux model is chosen using transport code SOLEDGE2D (S2D) applying power balance method over a simulated ne, SEP and Te, SEP profiles to obtain separatrix positions. The parameters are averaged over time windows with order of (85–185 ms) and the magnetic configuration has been fixed to avoid divertor geometrical effect on ne, SEP determination, configuration chosen is corner–corner. A ratio between separatrix density and pedestal density at outer midplane ranges between 0.3 and 0.7 on the data set. A scaling law of ne, SEP/ne, PED is obtained as function of Pinjected, BT, and IP.