Time: Nov. 23, 10am
Place: IFTS conference room
Title: Self-consistent fast ion relaxation in Resonance Broadened Quasi-Linear (RBQ) code modeling.
Speaker: Dr. Nikolai Gorelenkov, Princeton Plasma Physics Laboratory, Princeton University, USA
Abstract:
We present a realistic Quasi-linear (QL) model to find the energetic particle distribution function relaxed in the presence of Alfvénic instabilities. This approach is a numerically efficient method to capture the evolution of a beam ion distribution function. The spatial structure of the instabilities is computed by the eigenvalue solver for predictive simulations. The effect of Alfvénic eigenmodes (AE) is evaluated by adapting the QL theory [H. Berk et al., Phys. Plasmas'96] generalized for this problem. The application of the model to realistic plasma conditions is improved by going beyond the perturbative-pendulum-like approximation for the wave particle dynamics near the resonance. In addition the resonance broadening includes the Coulomb collisional or anomalous pitch angle scattering.
We apply the RBQ code to a DIII-D plasma with elevated q-profile where the beam ion profiles show stiff transport properties [C. Collins et al. PRL'16]. The sources and sinks are included via the Krook operator. The properties of AE driven fast ion distribution relaxation are studied for validations of the applied QL model to DIII-D discharges. Initial results show that the model is robust, numerically efficient, and can predict the fast ion relaxation in present and future burning plasmas.
