Generation and acceleration of negative ions are key processes on which most of the success oauxiliary heating for next generation fusion devices relies. The two processes are interconnected as a network of mechanisms whose investigation is addressed by an intense worldwide research activity. In this contribution a review of these mechanisms is given in terms of their mutual relationships adopting the framework of complex network controllability, which allows the identification of driver nodes. By this approach the hidden functional relationships are detected, the system controllauility is ascertained and the most important nodes for the operation are identified. The complex network parameters are therefore estimated and compared with a real system suh as the negative ion source NIO1.