Simulation of Runaway Electron Production with CQL3D coupled to NIMROD*

The CQL3D bounce-averaged Fokker-Planck (FP) code [1,2] is used to simulate Runaway Electron (RE) production in DIII-D thermal quench experiments with Neon shattered pellet injection. A one-way coupling has been achieved between the 3D extended MHD code NIMROD and CQL3D; the time-dependent data on plasma profiles (Ohmic current density, temperatures, toroidal electric field, densities of all ionization states of Neon, etc.) is read from NIMROD and mapped to the CQL3D grid. CQL3D then advances the FP solution for electrons over the same time range as NIMROD. As REs appear, the toroidal electric field used in CQL3D is adjusted by an internal feedback procedure to maintain a nearly constant current density during the thermal quench. Early results without radial transport of REs show a modest production of RE current. The distribution functions reveal an evolving velocity-dependent bump-on-tail feature. Time-dependent magnetic field fluctuation data from NIMROD is being used by CQL3D to calculate the effects of RE radial transport.

[1] R.W. Harvey, V.S. Chan, S.C. Chiu et al., Phys. Plasmas 7, 4590 (2000)

[2] R.W. Harvey and M.G. McCoy, www.compxco.com/cql3d.html