Analysis of H-mode and L-mode plasmas with a liquid Sn CPS divertor test unit in the ASDEX Upgrade tungsten divertor

This study analyzes impurity transport during ASDEX Upgrade experiments in which a Liquid Tin Module (LTM) was exposed to diverted plasmas. Using ASTRA and Aurora, we interpret H-mode and L-mode discharges to assess tin penetration into the core and its impact on radiated power. In H-mode, the simulations reproduce the observed tin radiation and droplet ejection, resulting in core concentrations of around 10^-4 and significant radiated power fractions, incompatible with sustained performance. In contrast, L-mode conditions mitigate impurity accumulation even under comparable source strengths, highlighting the sensitivity of tin transport to background confinement and density. Nonetheless, droplet-induced bursts remain the dominant risk in both regimes. Extrapolation to CPS-like (Capillary Porous Structure) divertor configurations suggests that uncontrolled droplet ejection could drive excessive radiation - especially in H-mode - whereas L-mode scenarios remain more tolerant. Overall, the results indicate that liquid tin divertors can be compatible with acceptable core performance, provided that effective strategies to suppress droplet ejection are implemented.