Form invariance in convective-diffusive systems with applications to impurity transport

Simple, closed from Green's functions are derived for convective- diffusive systems in slab and cylindrical geometries. In slab geometry, they are Gaussian, while in cylindrical geometry, they are of the form e -ar2 I0(βr), where I0 is the modified Bessel function, and α and β depend on time via e -t. Time dependent profiles resulting from various pulsed and oscillatory sources can be obtained using these Green's functions. These solutions can be used to model a variety of time dependent transport experiments such as pulsed impurity transport, oscillating gas puff, perturbative RF heating, and sawtooth heat pulse propagation. A successful comparison of our profiles with pulsed impurity injection experiments on TEXT is presented. 4 refs., 1 fig