Implementation and testing of a 3D extension of the SOLT model for tokamak edge turbulence*

Progress is reported on development of a 3D extension of the tokamak edge turbulence model SOLT [1]. The original SOLT solves for time-evolution of plasma density, temperature, and electrostatic potential in 2D, in a plane perpendicular to the magnetic field in the outboard midplane region of a tokamak; dynamics along the magnetic field is approximated by a parallel scale length parameter. The extended 3D version of SOLT, being developed in the BOUT++ framework [2], follows the original SOLT physics model but includes parallel variations of plasma fields and electron dynamics along the magnetic field line. Like the original SOLT, it models a domain representing the outer midplane region of a tokamak around the last closed flux surface, and divertor target plates are represented by sheath boundary conditions. Testing of the model includes verification of linear instabilities supported by the model, drift-resistive-ballooning and conducting-wall modes, and nonlinear solutions for isolated plasma filament propagation in the SOL. [1] Russell et al., Phys. Plasmas 22, 092311 (2015); [2] Dudson et al., Comp. Phys. Comm. 180, 1467–1480 (2009).