The Atomic Beam Probe Synthetic Diagnostic and its Application in Fusion Plasmas

Abstract: The Atomic Beam Probe was installed on the COMPASS tokamak in Prague as an extension of the Beam Emission Spectroscopy. The construction and installation of the diagnostic were preceded by conceptional design and measurements with a test detector. This development work was supported by a trajectory solver, written as a sequential code, called ABPIons, whose shortcomings were discovered early on. For further modeling, orders of magnitude larger numerical performance were required. Therefore, the trajectory calculator has been redesigned and implemented as a GPGPU (general-purpose computing on graphics processing units) code in CUDA C language, which resulted in a performance improvement of three orders of magnitude. The new solver, the Trajectory simulator of ABP Ions with GPU Acceleration (TAIGA), was used to establish the final diagnostics. To aid the improvement of the diagnostics and to design further measurement scenarios, we improved the code and developed a complete synthetic diagnostic. The trajectory solver is an essential tool for designing the ABP. However, a more sophisticated tool was required to consider all essential physical parameters in the simulation. Therefore, we developed the TAIGA-SD synthetic diagnostic, which is the subject of the paper. In this article, we introduce the concept of the Atomic Beam Probe synthetic diagnostics. We then show the initial input conditions, followed by the trajectory simulator, the mathematical and physical models we used, and the synthetic signal processing. Finally, we present how synthetic diagnostics supported the measurements and what the relation is between the synthetic and the measurement data.