Dynamics and Confinement of Ultralow-q Plasmasin the RFX-mod Device

Experimental UltraLow q, ULq q(a)< 1 plasma dynamics study in RFX mod device. Good agreement with non linear 3 D visco resistive MHD simulations. Both almost quiescent and largely fluctuating plasmas strongly sensitive on q(a Tendency of a dominant single mode (kink or resonant internal mode. Magnetic reconnection determines magnetic topology. Flat T e profiles for q(a) 0 5 internal gradients emerge for 0 5 q(a) 1 at low n e core localized thermal structures associated to single helical states. High electron density regimes, n e n G 1 accessible with peaking factors 1. Energy confinement time t E 1 ms with I p 800 kA. No wall locking detected, no double resonant m 1 mode observed.