The effect of pacing pellets on ELMs, W impurity behaviour and pedestal characteristics in high-power, JET-ILW H-mode plasmas

The effect of pacing pellets on ELMs, W impurity behaviour and pedestal characteristics in high-power, JET-ILW H-mode plasmas

The effect of pacing pellets on ELMs, W impurity behaviour and pedestal characteristics in high-power, JET-ILW H-mode plasmas 150 150 UKAEA Opendata
UKAEA-CCFE-CP(19)35

The effect of pacing pellets on ELMs, W impurity behaviour and pedestal characteristics in high-power, JET-ILW H-mode plasmas

In high-performance, ITER baseline-scenario pulses (3MA/2.7T) in JET-ILW with high levels (~ 32 MW) of heating power, typically ~ 20-40% of the input power is radiated, predominantly by W impurities, which are sputtered from the divertor targets and reach the confined plasma. Sustained ELMy H-mode operation at such high heating power in JET-ILW requires gas puffing to increase the ELM frequency and thereby the rate of W flushing from the confined plasma, as well as sweeping of the strike points to avoid overheating of the target material [1]. Core ICRH heating is also used for control of heavy impurity accumulation. A deleterious effect of the gas puffing is to reduce the pedestal temperature [2] by increasing the heat transport across the pedestal between ELMs [3, 4], which reduces the pedestal pressure [5] and the overall confinement compared to that achieved in similar JET-C pulses at the same heating power.

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46th European Physical Society Conference on Plasma Physics (EPS), Milan, 8-12 July 2019