This thesis presents an experimental study of neutral particle dynamics in Alcator C-Mod -a high power-and particle-density tokamak with an advanced poloidal divertor. The primary diagnostic used in the study is a set of six neutral pressure gauges, including special-purpose gauges built for in situ tokamak operation.While a low main chamber neutral pressure coincides with high plasma confinement regimes, a high divertor pressure is required for heat and particle flux dispersion in future devices such as ITER. Thus we examine conditions that optimize divertor compression, defined here as a divertor-to-midplane pressure ratio. We find that both pressures depend primarily on the edge plasma regimes defined by the scrape-off-layer heat transport. While the maximum divertor pressure (pdiv =30-60 mTorr) is achieved at high core plasma densities ( Ke =2-4.1 020 m-3), corresponding to the detached divertor state, the maximum compression (-70) is achieved in the high-recycling regime. Variations in the divertor geometry have a weaker effect on the neutral pressures. For otherwise similar plasmas the divertor pressure and compression are maximized when the strike point is located at the bottom of the vertical target plate.We introduce a simple flux balance model, which allows us to explain the divertor neutral pressure across a range of plasma densities. In particular, a high pressure sustained in the detached divertor (despite a considerable drop in the recycling -3-source) can be explained by scattering of neutrals off the cold plasma plugging the divertor throat. Because neutrals are confined in the divertor through scattering and ionization processes (provided the mean-free-paths are much shorter than a typical escape distance) tight mechanical baffling is unnecessary. The analysis suggests that two simple structural modifications may increase the divertor compression in Alcator C-Mod by a factor of -5. Widening the divertor throat would increase the divertor recycling source, while closing leaks in the divertor structure would eliminate a significant neutral loss mechanism.