Real-Time Siliconization System on HL-2A Tokamak

In order to control the plasma impurity during plasma discharge, a real-time siliconization system was built on HL-2A tokamak. A piezoelectric valve was employed to control the injection flow rate, and the control sequence of the HL-2A central control system was utilized as the trigger signal. The gas injection function and the sequential control were tested and proven with good stability and repeatability. Preliminary real-time siliconization experiment with different injection parameters was performed under HL-2A divertor and limiter plasma discharge condition, to study their impact on the plasma parameters. The experiment results show that the total line-average density increases after gas injection, while Dαand SiV only increase during the injection phase. A short-width injection pulse with high amplitude causes a larger perturbation on the plasma than that of a long-width pulse with low amplitude, indicating that a long-width pulse with low amplitude may be more suitable for the experiment. The coating area of one injection point is limited, which was evaluated by the Dαsignal in the toroidal direction, indicating that more injection points are necessary to obtain a uniform effect.