CQL3D Time-Dependent Runaway Electron Discharge Dynamics, Including Self-Consistent Ampere-Faraday Equation, Radial Transport, and RF QL Diffusion

CQL3D [1,2] provides a relativistic, finite-difference, bounce-averaged Fokker-Planck solution for the electron distribution $f$(v$_{\mathrm{0}}$,theta$_{\mathrm{0}}$,rho$_{\mathrm{0}}$,t) under the influence of density/temperature variations induced, in this case, by a parameterized model for impurity stream from gas or pellet injection simulating plasma disruption or RE mitigation, and the toroidal electric field. For CQL3D, 6D phase-space is reduced to 3D by averaging over gyro-phase, bounce-phase, and toroidal angle in toroidal axisymmetric geometry. The solution is found self-consistently with the time-dependent Ampere-Faraday equations. We vary parameters controlling the amount and velocity of the impurity source, the rate of T$_{\mathrm{e}}$-reduction, and the lowest T$_{\mathrm{e}}$ achieved, in order to clarify the role of these parameters for RE minimization. Effects of RF wave injection and internal excitation are considered, as a mechanism for enhanced pitch-angle scattering of electrons. [1] R.W. Harvey and M.G. McCoy, ``The CQL3D Fokker Planck Code,'' \underline {www.compxco.com/cql3d.html}. [2] R.W. Harvey, V.S. Chan, S.C. Chiu et al., Phys. Plasmas 7, 4590 (2000).