Classification of Edge Instabilities at Globus-M2 Tokamak
В. В. Солоха, Г. С. Курскиев, A. Yu. Yashin, И. М. Балаченков, В. И. Варфоломеев, A. V. Voronin, В. К. Гусев, V. Yu. Goryainov, V. V. Dyachenko, N. S. Zhiltsov, Е. О. Киселев, В. Б. Минаев, A.N. Novokhatsky, Yu. V. Petrov, А. М. Пономаренко, N. V. Sakharov, A. Yu. Telnova, E. E. Tkachenko, В. А. Токарев, S. Yu. Tolstyakov, E. A. Tukhmeneva, Н. А. Хромов, П. Б. Щеголев
Abstract
Abstract Among the peripheral instabilities observed at the Globus-M2 tokamak, two types of edge localized modes (ELMs) are brought into focus: ELMs synchronized and desynchronized with the sawtooth oscillations. The desynchronized ELMs appear in regimes that are characterized by high values of pressure in the pedestal, p ped ≥ 3 kPa, and they are observed in discharges with the toroidal magnetic field B T > 0.6 T and plasma current I P > 0.3 MA. The desynchronized ELMs belong to the type-III/V with the dominating effect of the peeling mode. The synchronized ELMs were observed in a wider range of discharge parameters, including at B T < 0.6 T and I P < 0.3 MA. Calculations of the stability of the peeling-ballooning (PB) mode showed that at pedestal width ψ norm = 0.09 and p ped > 3.5 kPa, destabilization of PB modes is possible without additional influence. Experimental data shows that the microtearing mode plays a dominant role in the pedestal. The microtearing mode does not allow the pedestal at Globus-M2 tokamak to reach the state of the unstable kinetic ballooning mode (KBM), which explains the low predictive power of the EPED model at this tokamak.