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Particle ingestion into turbine engines is a widespread problem that can cause significant degradation in engine service life. One primary damage mechanism is deposition of particulate matter in internal cooling passages. Musgrove et al. proposed a compact particle separator that could be installed between the combustor bypass exit and turbine vane cooling passage inlet. The design had small pressure losses but provided limited particle separation, and its performance has proved difficult to replicate in subsequent experiments. Borup et al recently developed a Magnetic Resonance Imaging (MRI) based technique for making full-field, 3D measurements of the mean particle concentration distribution in complex flows. A particle separator based on the Musgrove et all design was fabricated out of plastic using 3D printing. The primary difference from earlier designs was the addition of a drain from the collector, through which 3% of the total flow was extracted. The separator efficiency was measured at two Reynolds numbers, using water as the working fluid and 33 micron titanium microspheres to represent dust particles. Particle Stokes number was shown to play the dominant role in determining efficiency across studies. MRI was used to obtain the 3D volume fraction and 3-component velocity fields. The velocity data showed that flow was poorly distributed between the separator louvers, while the collector flow followed the optimal pattern for particle retention. The particle distribution data revealed that strong swirling flow in the collector centrifuged particles toward the outer wall of the collector and intro a partitioned region of quiescent flow, where they proceeded to exit the collector.