We aim to understand how porosities in the metal directed energy deposition (DED) process are formed, to achieve desired material property by using simulation-guided process design, and to counter machine-to-machine variations by fusing simulation and experimental data. High-speed synchrotron imaging has been used for in-situ observation of melt-pool dynamics, powder entrainment, and defect formation in laser powder bed fusion (LPBF), but phenomena in powder-blown processes, such as directed energy deposition (DED), will be very different due to much more stochastic and violent powder delivery. Our group addresses those differences by using the X-ray imaging technique at the Advanced Photon Source and a high through-put DED set-up to measure melt-pool geometry and fluctuations over a large range of energy densities and mass flowrates. Melt-pool conditions leading to pore formation and pore entrapment are elucidated and will be discussed. Finally, process control of the DED process at the macro-scale will be presented.