Fusion Science and Technology / Volume 61 / Number 1 / January 2012 / Pages 11-18
We have designed and constructed a system for control of the normalized (N) in the National Spherical Torus Experiment [M. Ono et al., Nucl. Fusion, Vol. 40, p. 557 (2000)]. A proportional-integral-derivative operator is applied to the difference between the present value of N (from real-time equilibrium reconstruction) and a time-dependent request in order to calculate the required injected power. This injected power request is then turned into modulations of the neutral beams. The details of this algorithm are described, including the techniques used to develop the appropriate control gains. Example uses of the system are shown.