The atomic beam probe (ABP) is a beam diagnostic concept that opens opportunities in plasma edge measurements due to the sensitivity of the magnetic field and the high temporal resolution. The first ABP has been installed and is operating on the COMPASS tokamak. A new numerical toolset, which is the subject of this paper, was required to model the diagnostic to accurately detect the alkali beam. For further development and understanding of the diagnostic, this tool had to be designed to simulate different magnetic field configurations in a performance-efficient manner. The TAIGA synthetic diagnostic (TAIGA-SD), which was implemented with a massively parallel trajectory solver core that runs on graphic cards to support experiments, provides a better understanding of measurements and has opened opportunities for future applications. This paper presents the model concept with relevant physical processes and necessary simplifications. The submodules implemented or integrated into the synthetic diagnostic are explained and described, and their scopes of validity are highlighted. This includes the integration of RENATE-OD for the primary ionization radial distribution for lithium beams, as well as the implementation and verification of a combined electron impact and charge exchange ionization module for other alkaline beams, which is a new atomic physics solver. Calculations were performed to investigate the relation between magnetic field, electron density, and temperature perturbations. Further simulations were run to estimate beam attenuation due to secondary ionization. The utilization of the ABP synthetic diagnostic is demonstrated by comparing it with the measurements.

Diagnosing the density profile at the edge of high temperature fusion plasmas by an accelerated lithium beam is a known technique since decades. By knowledge of the relevant atomic physics rate coefficients, the plasma electron density profile can be calculated from the relatively calibrated light profile along the beam. Several additional possibilities have already been demonstrated: Charge Exchange Resonance Spectroscopy (CXRS) for ion temperature/flow and Zeeman polarimetry for edge plasma current; therefore the Li-beam diagnostic offers a wealth of information at the plasma edge. The weaknesses of the method are the relatively faint light signal, background light, and technical difficulties of the beam injector which usually seriously limit the applicability. In this talk, we present systematic developments in alkali-beam diagnostics (Li, Na) for the injector and the observation system and detectors which resulted in strongly increased capabilities. Advanced systems have been built, and microsecond scale density profile, turbulence, and zonal flow measurement have been demonstrated. A novel edge current measurement technique has also been designed, and components have been tested with potential microsecond-scale time resolution. Additional possibilities of these advanced systems for spectral measurements (CXRS and various Zeeman schemes) are also discussed.