3D plasma-wall interaction in the RFX-mod device

This thesis is devoted to the characterisation of the plasma instabilities causing the Plasma Wall Interaction (PWI) observed during a high current discharge by the Optical Camera System in the RFX-mod reversed field pinch (RFP) device, operated by Consorzio RFX in Padova, Italy. The PWI shows two distinct stripes of neutral carbon radiation on the internal graphite wall of the device. The main goal is to simulate and understand the origin of the pattern. The topic is not specific to the RFP configuration, but is is studied in perspective of ITER, the nuclear fusion experimental reactor which is under construction in Cadarache, south of France. The complicate 3D topology of the plasma which gives birth to the PWI in the case study is investigated via the Hamiltonian guiding center code Orbit . A preliminary analysis with a simplified model of 3D topology shows that the maximum toroidal mode number of plasma instabilities involved in the PWI event is higher than the measured n ≤ 23. This information is important in view of the refurbished RFX-mod2 device. Further analysis is performed with Orbit and regards the description of the map of connection lengths to the wall. This map qualitatively reproduces the experimental PWI pattern on the surface of the RFX-mod wall. Finally, it shows that the two stripes of the PWI, represented by low connection lengths, are caused by modes with different poloidal number, m = 0 and m = 1.