Dynamic response treatment of a burning fusion plasma. Dedicated to Nils Robert Nilsson on the occasion of his retirement from NORDITA

The dynamic response of a burning fusion plasma to periodic particle source fluctuations as well as to self-induced or externally induced fluctuations in the transport coefficients is studied. Simple coupled reaction-diffusion equations are deduced for the dynamic description of the time variation of the temperature and density in the central part of the plasma. As a result of the form of the alpha particle heating term such a system of equations exhibits free oscillations in temperature and density in approaching an equilibrium state from any given initial state. When the particle sources or the transport coefficients are asumed to have driven periodic parts the plasma responds dynamically by exhibiting a mixture of free and forced oscillations. Since, due to heat conduction and particle diffusion, the free oscillations will be damped, only the forced oscillations remain after some time. The plasma dynamic response to the driven variations in the source and transport coefficients contains information about the plasma transport parameters, e.g. the power of the temperature dependence of the heat conductivity as well as of the particle diffusion. It might therefore be used for diagnostics for a burning fusion plasma. (orig.)