Development of a radiative divertor simulator using the KAIMIR device

In this study, a radiative divertor simulator was developed using the linear magnetic mirror device KAIMIR, considering the center chamber as the upstream scrape-off layer and the expander chamber as the downstream region. To achieve divertor-relevant conditions, the gas feed system of the KAIMIR device was upgraded to increase the particle flux at the downstream region. In addition, a differential pumping system using a skimmer structure was implemented to enable independent control of the neutral pressure between the upstream and downstream regions by reducing the vacuum conductance between the chambers. With this system, a neutral pressure up to 70 mTorr was achieved in the expander chamber while maintaining plasma characteristics in the center chamber. Simulations were then conducted, where non-monotonic behaviour of the ion saturation current and line-integrated density was observed with increasing neutral pressure in the expander chamber, suggesting a transition from attached to detached plasma regimes. Visible emission profiles from fast camera measurements revealed enhanced recombination emission and the formation of localised low-temperature plasma near the downstream region. These results demonstrate that the upgraded KAIMIR device provides a controllable linear divertor simulator suitable for the investigation of radiative and detached divertor plasma physics in a linear configuration.