Processes and properties of edge-localised instabilities in 2T 2MA plasmas in the Joint European Torus

Processes and properties of edge-localised instabilities in 2T 2MA plasmas in the Joint European Torus

Processes and properties of edge-localised instabilities in 2T 2MA plasmas in the Joint European Torus 150 150 Mathew

Processes and properties of edge-localised instabilities in 2T 2MA plasmas in the Joint European Torus

During July 2012, 150 almost identical H-mode plasmas were consecutively created in the Joint European Torus, providing a combined total of approximately 8 minutes of steady-state plasma with 15 000 Edge Localised Modes (ELMs). In principle, each of those 15 000 ELMs are statisti- cally equivalent. Here, the changes in edge density and plasma energy associated with those ELMs are explored, using the spikes in Beryllium II (527 nm) radiation as an indicator for the onset of an ELM. Clearly different timescales are observed during the ELM process. Edge temperature falls over a 2ms timescale, edge density and pressure fall over a 5ms timescale, and there is an additional 10 ms timescale that is consistent with a resistive relaxation of the plasma’s edge. The statistical properties of the energy and density losses due to the ELMs are explored.

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09/11/2014