Achievement of Long Sustainment of High Performance Discharge
In JT-60U, an ELMy H-mode with favorable confinement performances (central ion temperature ~ one hundred million °C and confinement improvement factor ~ 1.7) was sustained almost steadily for 9sec under a high neutral beam heating power of 20-25MW at a plasma current of 1.5MA and a toroidal magnetic field = 3.6T (see Fig.).
The total energy input (time integration of the heating power) reached 203MJ (the highest value in divertor tokamaks ). Even at this high value, no increase in carbon and recycling particles was observed. Before the divertor modification, large increase in carbon and recycling severely degraded the discharge performance at the total energy input of ~70-80MJ.
Fig. Waveform of 9 sec ELMy H-mode
Such improvement in sustainment of high performance ELMy H-mode is expected to further understanding of physics characterized by parameters with long time constants such as the current profile and particle recycling etc.