Ultrafast Velocity Measurement of Shock Wave using Microwave Photonic Velocimetry

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This award supports fundamental research on a novel sensing modality, namely, microwave photonic velocimetry (MPV). In shock wave experimentation, velocimetry is the measurement of the speed of a shock wave as it develops, propagates, and fades. This provides critical information on shock wave behavior. The goal of this project is to support the measurement of the velocity of ultrafast shock waves, traveling at speeds in the order of several tens of km/s, in-situ and in real-time. This will enable the study of energetic materials, and eventually lead to much safer industrial workplaces where explosions may pose a hazard. Robust and accurate velocimetry that can measure ultrafast shock waves is an outstanding technical challenge that limits our understanding of shock wave physics and chemistry. If successful, the MPV technology will fill this void by substantially expanding our knowledge of materials' ability to detonate under a wide variety of physical conditions (temperature, pressure, concentration, etc.). Thus, breakthroughs in MPV as pursued in this project, will have significant societal benefits in preventing disasters and improving safety in hazardous environments. In particular, MPV is anticipated to be an enabling tool in the safe handling and storage of non-ideal (borderline) explosives. These are materials that are conventionally rated as safe, but may become a deadly threat in workplaces under certain conditions. Specific research objectives include understanding and characterizing the MPV concept, investigating novel signal processing methodologies, and validating this novel sensing modality using large-scale, outdoor detonation tests. The direct outcome is the fundamental knowledge, implementation, and demonstration of the MPV concept. Key innovations include: 1) the innovative use of interactions between microwave and optical waves, enabling the creation of a precise, robust, and low-cost velocimetery, 2) the innovative integration of optical frequency comb technologies in the MPV system to precisely separate elements measured in the frequency-domain, 3) the novel MPV probe with integrated graded index fiber (GIF) collimator, which significantly enhances MPV's performance, 4) a novel signal processing algorithm that intelligently reconstructs the velocity history profiles of explosion events, and 5) enhanced multiplexing capability allowing for simultaneous, multi-probe shock wave velocity measurement.