Small ELMs in Quasi-Double Null Plasmas at JET

This paper describes the results of recent identity experiments with ASDEX Upgrade in Quasi Double Null (QDN) plasmas to access the type II ELM regime. These ELMs are defined as "irregular, high frequency, low amplitude", appearing when the plasma is in QDN configuration. With the new JET divertor (MKII-HD), it has been possible to develop a QDN plasma configuration matching simultaneously upper and lower triangularity as well as the elongation of a quasi double null plasma of ASDEX Upgrade and a steady state regime has been achieved. The proximity to double null configuration was varied from lower single null to upper single null defining an optimum interval of sep to obtain type II ELMs. These results show that double null configuration is important to access this regime, but not sufficient. To achieve collisionalities relevant for ITER a plasma current (Ip) scan, from 0.86MA to 1.6MA, was performed. A regime with small ELMs is reproducible at both these plasma currents.
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