Real-time vertical instability growth rate formulation and proximity controller application in the TCV tokamak

Vertical instability is a major cause of disruptions in elongated tokamak plasmas. To prevent Vertical Displacement Events (VDEs), advanced control strategies, such as proximity controllers, have been developed. These controllers help avoid regimes where traditional systems fail to maintain stability and have been tested in tokamaks such as DIII-D and EAST. Proximity control relies on real-time monitoring of vertical instability indicators, notably the growth rate. In this paper, a new real-time formula for the growth rate is derived. The proposed metric was implemented on the TCV tokamak and used to develop a proximity controller for vertical stability. The controller was tested on TCV discharges, and its performance, efficiency, and limitations are analyzed and discussed in detail.