Implementation and preliminary results of the first vertical stabilization control system for HL-2M

Abstract

Achieving advanced divertor configurations and high-confinement operating regimes is crucial for mitigating divertor heat loads and exploring enhanced confinement physics in the HL-2M tokamak. However, these scenarios with highly elongated plasmas face severe Vertical Displacement Events (VDEs) that can lead to rapid plasma termination and potential device damage. Robust active control of vertical instability is therefore essential. As HL-2M lacks internal control coils, we developed two sets of vertical stabilization (VS) control systems, each employing a pair of external poloidal field (PF) coils, PF main power supplies, and VS power supplies. This paper details the first vertical stabilization (VS1) control system's circuit diagram, hardware architecture, and software implementation, and discusses issues encountered during commissioning and their solutions. By improving the internal hardware of the VS power supply, the voltage rise time was reduced to approximately 30 microseconds, resolving branch current imbalances. The transmission delay of the control signals is approximately 38 µs. Preliminary plasma experiments demonstrated effective vertical displacement control with the VS1 control system, achieving a maximum plasma elongation of 1.73 and typical control accuracy of ~ 20 mm. This work lays the foundation for robust control under high-parameter operational scenarios and the design and implementation of the higher-power VS2 control system.