Design of a Plasma Position Calculator using the ADSP2105 digital signal processor

A Plasma Position Calculator, which determines the plasma position in real time during a plasma shot, has been developed for use on TFTR. Digital signal processing technology is used to calculate plasma current, major radius and vertical position as functions of differential magnetic flux signals and poloidal magnetic field signals. The position information is supplied to the TFTR Neutral Beam Permissive Generator where it will be used to prevent beam injection when the plasma is in an undesirable position. This paper describes the algorithm used and the hardware and firmware design.