Real-time simulation of internal profiles in the presence of sawteeth using the RAPTOR code and applications to ASDEX Upgrade and RFX-mod

This work presents the integration of the Porcelli's sawtooth model in the RApid Plasma Transport simulatOR (RAPTOR) code [F.A.A. Felici et al., Nucl. Fusion 51, 083052 (2011)] and its application to ASDEX Upgrade and RFX-mod experiments. RAPTOR is a 1D transport code that evolves in real-time the current density and electron temperature profiles, using various diagnostics in input, and it is designed for real-time reconstruction of the plasma state and for various control applications. The recently implemented sawtooth module can model both partial and full reconnection triggered by a threshold in the magnetic shear at the q=1 radius. In the present work, RAPTOR is used in predictive simulations to model the current density and the electron temperature profiles in sawtoothing ASDEX Upgrade discharges, but it also simulates the same profile evolution in real-time, yielding a plasma state estimate that includes the effect of sawteeth. This work aims at modelling ASDEX Upgrade scenarios with sawteeth and understanding sawtooth control and locking experiments. It also discusses the improvements in the plasma state reconstruction, in particular in the evolution of the safety factor profile, obtained by the inclusion of the Porcelli's sawtooth model in the code. Possible applications to real-time sawtooth control, like suitable power actuator schemes and locking techniques, are investigated. An improved real-time estimate of the safety factor profile may find also other useful applications, for example to improve NTM control using ECCD. RAPTOR is also being implemented in real-time in the RFX-mod device. RAPTOR is used in this case in low-current Ohmic tokamak discharges and the main aim is to develop and test disruption avoidance schemes based on a real-time comparison between various diagnostic signals and RAPTOR predictions. This may be useful to prepare similar experiments in larger tokamaks, for example in ASDEX Upgrade.