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

Midplane separatrix density is a crucial parameter in tokamaks since it strongly impacts divertor conditions. Scaling midplane separatrix density, n e , SEP , and pedestal density, n e , PED , as function of engineering parameters such as auxiliary heating P injected , toroidal magnetic field B T , and plasma poloidal current I p are relevant to observe the effect of tuning these parameters on, for example, quality of confinement and divertor regime governed by n e , PED and n e , 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 n e , 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 n e , SEP and T e , 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 n e , 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 n e , SEP / n e, PED is obtained as function of P injected , B T , and I P .