Neoclassically driven tearing modes (NTMs) are a major problem for tokamaks operating in a conventional ELMy H-mode scenario. Depending on the mode numbers these pressure-driven perturbations cause a mild reduction in the maximum achievable βN = βt/(Ip/aBt) before the onset of the NTM, or can even lead to disruptions at a low edge safety factor, q95. A control of these types of modes in high βN plasmas is therefore of vital interest for magnetically confined fusion plasmas. The control consists of two major approaches, namely the control of the excitation of these modes and the removal, or at least mitigation, of these modes, once an excitation could not be avoided. For both routes examples will be given and the applicability of these approaches to ITER will be discussed.
Control of multi-helicity neo-classical tearing modes by electron cyclotron current drive in tokamak plasmas