ELMy H-mode

Fig. 3.3. Time traces for a JET discharge evolving from L-mode to Type I ELMy H-mode [15]. (NBI) is the input power into the plasma by fast neutral beams, Wtot is the total plasma energy (thermal + non-thermal component), Da (divertor) is the deuterium emission in the Balmer a line from neutrals coming into the plasma in the divertor area, average n is the average density of the discharge, Ti>core and Te,core are the ion and electron temperatures in the centre of the discharge and TelPed is the electron temperature at the top of the pedestal...

Fig. 3.8. Normalized energy confinement in JET Type I and Type III ELMy H-modes versus plasma density normalized to the Greenwald value for various plasma shapes [10]...

Because of this, the Type I ELMy H-mode regime has been chosen as the reference operating regime for high fusion gain experiments in next step devices, such as ITER and FIRE [23], despite the drawbacks associated with the large energy and particle fluxes on the PFCs inherent to the Type I ELMs themselves. 

Fig. 3.13. Time duration of the edge plasma collapse phase determined from the edge soft X-ray emission for a large range of JET Type I ELMy H-mode plasmas [27]...

Fig. 3.16. Normalized ELM energy loss (AITELM/IFpeci) versus pedestal plasma collisionality for a large range of Type I ELMy H-mode plasmas in ASDEX Upgrade, DIII-D, JT-60U and JET including various plasma triangularities, ratios of Pinput/Fl-h and pellet triggered ELMs and qg5 = 3-4 [33]...

Upgrade and DIII-D, as shown in Fig. 3.17. In this context, the expected values of T ront in ITER fall in the upper range of those seen in existing experiments, despite the very small collisionality of the pedestal plasma in ITER. In existing experiments, large values of T ront in Fig. 3.17 correspond to Type I ELMy H-modes at high densities and low pedestal temperatures, for which the ELM conductive losses are smaller and, consequently, the total ELM energy losses are small as well. 

Fig. 3.21. Time evolution of the surface temperature of the outer divertor target and the deduced power flux, for typical low density ELMy H-mode conditions in JET (ne,ped = 5.2 1019m 3, Te,pea = 1650eV). For inter-machine comparisons, the duration of the ELM power pulse is characterized by the rise time of the surface temperature during the ELM (tiIrLM), as illustrated in the figure [16,40]...

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