This paper presents a 340 GHz FMCW Pulse-Doppler Radar that detects single particles as small as 0.1 mm at 5 m distance with sufficient signal to noise for range resolution of about 1 cm and a voxel size of several cubic cm. The radar system is characterized for noise performance, range resolution, particle detection and velocity measurement with up to 10x improvement demonstrated compared to similar systems. Potential system applications are found in pharmaceutical manufacturing, in energy conversion by fluidized bed reactors, and in meteorological applications.