Alternative configurations for the DEMO divertor are being explored to achieve an improved mitigation of the heat and particle loading at the plasma-material interfaces. These configurations with a variable volume in the private flux region (PFR), which consequently influences the neutral behavior and hence the achieved divertor pumping efficiency. This paper studies, in terms of the pumping efficiency, a wide range of prominent proposed alternatives to the conventional, single-null divertor, namely the "double null" divertor, the "X divertor", the "Super-X divertor" and the "snowflake" divertor. The investigation of the impact of neutral gas dynamics on the particle exhaust for an alternative divertor under steady-state operation, will be performed using the numerical tool DIVGAS (Divertor Gas Simulator). The DIVGAS code is based on the Direct Simulation Monte Carlo (DSMC) method, in which the solution of the Boltzmann kinetic equation is reproduced by simulating the collisions and the ballistic flight of model particles, which statistically mimic the behavior of real molecules. In view of DEMO, the DIVGAS code will allow for identifying the design space of an optimum divertor, which features high pumping efficiency. In our workflow, the neutral flow field for each of the aforementioned alternative divertor configurations will be derived from plasma boundary conditions extracted from SOLPS fluid simulations, exactly at the interfaces between the Scrape-off layer (SOL) and the PFR. All assumed plasma scenarios are based on a highly dissipative divertor relying on a partially detached divertor operating regime, similar to ITER, or even on full detachment. Moreover, the position and the size of the pumping port as well as their influence on the neutral flow behavior in the PFR are analyzed and the advantages and disadvantages of each case are discussed.

Alternative configurations for the DEMO divertor are being explored to achieve an improved mitigation of the heat and particle loading at the plasma-material interfaces. These configurations with a variable volume in the private flux region (PFR), which consequently influences the neutral behavior and hence the achieved divertor pumping efficiency. This paper studies, in terms of the pumping efficiency, a wide range of prominent proposed alternatives to the conventional, single-null divertor, namely the "double null" divertor, the "X divertor", the "Super-X divertor" and the "snowflake" divertor. The investigation of the impact of neutral gas dynamics on the particle exhaust for an alternative divertor under steady-state operation, will be performed using the numerical tool DIVGAS (Divertor Gas Simulator). The DIVGAS code is based on the Direct Simulation Monte Carlo (DSMC) method, in which the solution of the Boltzmann kinetic equation is reproduced by simulating the collisions and the ballistic flight of model particles, which statistically mimic the behavior of real molecules. In view of DEMO, the DIVGAS code will allow for identifying the design space of an optimum divertor, which features high pumping efficiency. In our workflow, the neutral flow field for each of the aforementioned alternative divertor configurations will be derived from plasma boundary conditions extracted from SOLPS fluid simulations, exactly at the interfaces between the Scrape-off layer (SOL) and the PFR. All assumed plasma scenarios are based on a highly dissipative divertor relying on a partially detached divertor operating regime, similar to ITER, or even on full detachment. Moreover, the position and the size of the pumping port as well as their influence on the neutral flow behavior in the PFR are analyzed and the advantages and disadvantages of each case are discussed.