This work investigates the evolution of dense tin vapor/plasma structures generated during divertor-relevant high heat flux irradiation of a liquid tin capillary porous system target in the OLMAT facility. The target was exposed to 125 ms hydrogen particle beam pulses (effective heat fluxes ∼33 MW m−2). The near-surface plasma was diagnosed using an embedded Langmuir probe and optical emission spectroscopy, while the target thermal response was monitored by infrared pyrometry. The addition of transient type-I edge localized modes-like 2 ms laser loads (∼500 MW m−2 heat flux) enabled access to previously unexplored plasma/liquid-metal boundary conditions at a quasi-stationary target-temperature plateau near 1775 ± 100 K. The generated, nearly pure Sn plasmoid was characterized up to target temperatures of ∼1700 K, corresponding to peak Sn+ densities ∼2 × 1020 m−3. The measured density increase is qualitatively consistent with the strong exponential rise of the evaporative Sn neutral source. However, the plasma evolution cannot be explained solely by vapor production. A simple Sn+ ionization-efficiency analysis reveals a progressive decrease above target temperatures of ∼1500 K despite electron temperatures remaining within 2–5 eV. Simultaneously, the radial expansion velocity decreases while the characteristic plasma size saturates, suggesting an increasing influence of collisional processes. A phenomenological Sn–Sn+ collisionality parameter was introduced by comparing inferred plasma length scales with ion-neutral mean free paths (Langevin-type collision model estimates). Although affected by significant uncertainty, collisionality increases by more than two orders of magnitude over the target temperature range driven by the strong rise in neutral tin density. Ion-neutral collision times also become substantially shorter than characteristic plasma expansion times against the particle beam. The inferred onset of moderate and strong collisionality occurs within the same target-temperature and plasma-density range associated with heat-flux mitigation at the target surface. These observations are qualitatively consistent with a power exhaust transition toward a dissipative, collisional vapor-plasma regime.