Simultaneous Control of Electron Density and Effective Atomic Number in Non-burning Tokamak Plasmas
D. Boyer, P. Boyle, E. Schuster, G. Bateman, A. Kritz
Division of Plasma Physics (DPP) Annual Meeting of the American Physical Society (APS)
Atlanta, Georgia, November 2-6, 2009
Abstract
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The control of plasma kinetic profiles is one of the most fundamental
problems in tokamaks. Precise regulation of electron density and
effective atomic number, or alternatively hydrogen and impurity
densities, is required during routine operation. A common means of
actuation toward this end is the use of fast-acting gas valves for the
injection of different species. However, non-linear coupling may lead
to a closed-loop oscillatory behavior when there is a failure to
properly account for the multi-input-multi-output nature of the
problem. In this work, controllers are sought to regulate both the
average value and spatial profiles of the electron density and
effective atomic number. One-dimensional transport equations for these
variables are represented in cylindrical coordinates by a set of
partial differential equations (PDEs) and used for control synthesis
based on nonlinear and backstepping techniques. Numerical simulations
illustrating the effectiveness of the resulting control laws are
presented.