Abstract

Redesign of the Tokamak ISTTOK hydrogen injection system
The gas injection and wall recycling in a tokamak are critical to maintain the plasma on stable conditions. On the tokamak ISTTOK a new injection system operated with a piezo electric valve is being installed to achieve precise puffing injections of hydrogen. This redesign is intended primary to allow long period operation over 250ms, for AC operation.
The system should be suitable for feedback control based on a digital signal processor. A real time plasma density evaluation from the microwave interferometer data provides a good control variable for the preocess loop.
The major change on the system was the inclusion of one buffer operat at 10-100 mbar, which allows the reduction of the intake gas pressure during puffing experiments. This new design allows a more precise hydrogen quantities injection based on the piezo electric open-time and leads to longer and stable plasma shots.