Fast digital link for a tokamak current source control

The need for real-time plasma position control on the ISTTOK tokamak led to the development of two similar 240 A:500 kA/s fast power supplies, for the vertical and horizontal magnetic equilibrium fields. This paper presents the design, the digital link, the modeling and operation of the vertical B-field power supply. It consists of a digital hard real-time control embedded board, based on a microcontroller programmed in assembly to ensure a fault free operation. In order to avoid the magnetic noise present in tokamak operation, the communication with the power supply is optic. A robust and fast communication protocol was developed to reduce processing time. An optimized control for the vertical power supply was also developed and tested successfully. Simulation and experimental results are presented showing the efficiency of the proposed power supply.