| Plasma electronic density is one of the important parameters in magnetic confined thermal fusion experiments. Keeping the plasma density the same with the desired quantity during the flat-top phase is required in tokamak physical experiments. So how to control plasma density accurately in real time is essential for the fusion research.The purpose of this article is to establish a plasma density feedback control system on the Joint Texas Experimental Tokamak(J-TEXT) for meeting the need for an accurate plasma density in physical experiments. Among the factors that influence plasma density in tokamak device, to control gas inlet for minimizing the difference between the reference and real plasma density is also the most simple and effective. As density control system on many other devices, this system is controlled with the method of adjusting the gas inlet in real time according to the change of the density signal during discharge. The system consists of density measurement subsystem, feedback control subsystem and gas puffing subsystem. Normal operation and cooperation with each other for every subsystem show real-time capability and stability of the whole system. According to the characteristic of gas puffing system, voltage amplitude control mode has been applied in the feedback control strategy, which is accomplished by the proportion, integral and differential(PID) controller. And control algorithm chooses incremental PID control algorithm.This paper has conducted in-depth research into density control based on Tokamak. According to the characteristics of the J- TEXT device, a feedback control model has been designed, and the feedback control algorithm is designed based on the model. And the quantity calibration of gas injection, adjusted responding to the change of the density signal, has been carried out. After the completion of the entire system, we make a lot of experiments to test the performance of the system. Some experimental results have been shown and discussed. |
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