Scrape-off layer based modelling of the density limit in beryllated JET limiter discharges

Abstract

The paper gives a scrap-off layer based interpretation of the density limit in beryllated JET limiter discharges. In these discharges, JET edge parameters show a complicated time evolution as the density limit is approached and the limit is manifested as a nondisruptive density maximum which cannot be exceeded by enhanced gas puffing. The occurrence of Marfes, the manner of density control ad details of recycling are essential elements of the interpretation. Scalings for the maximum density are given and compared with JET data. The relation to disruptive density limits, previously observed in JET carbon limiter discharges, and to density limits in divertor discharges is discussed