Machine And Magnetic Diagnostics System On J-TEXT Tokamak

The Joint TEXT (J-TEXT) tokomak, formerly named as the TEXT/TEXT-U tokomak and operated by the University of Texas at Austin in USA, has been reconstructed in Huazhong University of Science and Technology in China and it is the only medium-size tokomak device in Chinese universities. The machine has been run for two experimental campaigns since 2007 and a plasma current, more than 200 kA with duration of 300 ms, has been obtained. At present, all sub-systems, like poloidal field (PF) and toroidal field (TF) power supplies, vacuum system, diagnostics systems etc, are successfully integrated into the routine operation. The plasma position can be elaborately controlled within two centimeters. All operating behavior and limits of the J-TEXT tokomak are typical of the machine and easy to understand, compared to the former TEXT/TEXT-U experimental results. The Joint TEXT Lab was established to cultivate fusion engineers and do some basal physical study such as disruption. It is open to world-wide fusion researchers and J-TEXT machine can serve as the complementary and pre-experimental device for large-size tokomaks in the future.A new vacuum system is designed and developed on the Joint Texas Experimental tokomak (J-TEXT), which consists of two pumping stations, Taylor discharge cleaning system and gas puffing. With this system, the vacuum vessel of the J-TEXT tokomak can easily reach a vacuum condition which allows the operation of the machine. The sub-control system of the vacuum pumping systems with the self-protection function is reliable and easy to use. Inside the chamber, the base pressure can be lowered to 6.4×10^-6 Pa, and the total leakage and outgassing rates in 12 hours is below 1.5×10^-8 Pa·m³/s. Moreover, the Taylor discharge cleaning sub-system is used to clean the first facing walls of vacuum chamber to guarantee a good wall condition of the device before each run of the experimental campaign on the J-TEXT tokomak. The basic functions of the vacuum system meet the essential requirements of present experiments on J-TEXT tokomak.As a basic part of the plasma diagnostic systems on J-TEXT, the magnetic diagnostic system is very important for machine operation and the plasma physics research. The tasks of magnetic diagnostics are as follows: Measurement of basic plasma parameters such as plasma current, loop voltage, equilibrium plasma configuration determination and MHD phenomena studies. The magnetic diagnostic system had been designed and installed on J-TEXT before J-TEXT first plasma. The measurement system includes magnetic probes, Rogowski coil, poloidal flux/voltage Loops, and diamagnetic loop. Before the experiment, all the sensors and integrators are calibrated accurately by PF coils/Power supplies. This ensures each signal enough precision for the magnetic configuration determination. In both campaigns, the magnetic diagnostics provided sufficient measurements for the efficient machine operation and physical research.