Abstract of FELTOR Project

The objective of this project is to gain a thorough understanding of the dynamics of turbulence and instabilities in the edge and tokamak scrape-off layers. This is achieved via simulations on high performance computers, data analysis and comparisons with experimental results. The goal is to predict the heat load on the limiter/divertor and the plasma facing components. This is highly relevant for the heat exhaust problem laid out in Mission 2 of the European fusion road map. We will particularly investigate the power load caused by single seeded filaments and by coupled edge/scrape-off layer turbulence. We especially focus on geometric effects like field line curvature and magnetic shear. The often invoked Boussinesq approximation is not applied in our full-F gyrofluid model, which also incorporates electromagnetic as well as finite Larmor radius effects due to finite ion temperatures. This distinguishes our model from drift-fluid models and the model is therefore highly suited for the high fluctuation levels and the large ion to electron temperature ratios that are universally observed in tokamak scrape-off layers. Our code package FELTOR, which we developed during the last four years, is able to solve the equations efficiently on high performance compute clusters. It is an open source project and the resulting code extensions and improvements are made public alongside peer-reviewed journal articles. FELTOR is the only code available today with the described capabilities.

The indicated nature of the HLST support being requested is the optimization of hybrid MPI and OpenMP back end of the code, especially for the Intel Knights Landing architecture on the A2 partition of the MARCONI cluster.