Electron temperature gradient driven instabilities in helical reversed field pinch plasmas

Helical states have, in general, beneficial consequences on the reversed field pinch plas m aperfor m ance. Good confine m ent properties are achieved due to an overall reduction of m agnetic chaos. On the other hand, this physical condition favors the onset of radially localized electrostatic/electro m agnetic turbulence due to the si m ultaneous for m ation of large pressure gradients in the region surr ounding the he lical core. In a previous work, ion-te m perature-gradient (ITG) turbulence has been investigated with a realistic geo m etric description of the 3D configuration * . The core displace m ent turns out to have an unfavorable effect in ter m s of ITG turbulent transport: in the region of higher m agnetic surface proxi m ity, the local te m perature gradients beco m e larger with consequent growing instabilities, weaker zonal flows, and, in general, larger ion heat fluxes. Since the transport barriers are usually observed in the electron heat channel, in this contribution we m ainly focus on the occurrence of instabilities driven by the electron te m perature gradient. Due to the i m portance of electro m agnetic effects in the reversed field pinch, we include finite ? and collisionality, using realistic geo m etry and plas m a profiles. The occurrence of low wavenu m ber m icrotearing m odes (MTMs) and high wavenu m ber electron- te m perature-gradient (ETG) m odes is discussed, with their possible role in the deter m ination of the electron heat conductivity. The role of the geo m etric coefficients is also explicitly analyzed, m aking a co m parison with the corresponding axisy mm etric configurations.