Development and validation of a local neoclassical transport module in NLT with applications to EAST-relevant impurity transport

A local neoclassical transport module has been developed and validated in the semi-Lagrangian gyrokinetic code NLT for multi-species collisional plasmas. The module incorporates a linearized multi-species Sugama collision operator and provides two complementary solution strategies. In the initial-value formulation, a composite substep source-integration scheme is introduced to accurately evaluate the neoclassical drive along unperturbed particle trajectories while retaining large macroscopic time steps. A direct steady-state solver is also implemented to obtain the stationary neoclassical response without long-time relaxation. Both approaches are benchmarked against NEO for electron-ion plasmas, and the direct steady-state solver is further tested for three-species plasmas containing carbon impurities. The NLT results reproduce the NEO particle and energy fluxes, parallel flows, and bootstrap current over a broad collisionality range. As a representative application, the validated framework is applied to tungsten impurity transport under EAST-relevant conditions. The results demonstrate that tungsten neoclassical transport is sensitive to local plasma-profile gradients. This application extends the capability of NLT toward realistic multi-species collisional neoclassical transport simulations.