Ballistic Imaging for Dense Spray Diagnostics in Harsh Chemically Reacting Environments

The primary objective of this Phase-II research effort will be to build, deliver, and test a next-generation time-domain ballistic photon imaging (BPI) system based on ultrafast lasers for characterizing the two-phase combustion region within bi-propellant rocket engines. This will include integration into a rocket facility of choice for the Air Force Office of Scientific Research and the Air Force Research Laboratory. Preparations will be conducted in consultation with researchers at Edwards AFB and our industry partner, Aerojet Corporation. This work will build upon the successful application of the BPI technique in various sprays during the Phase-I research activities. The unique feature of BPI is that it can circumvent the difficulties associated with propagating light through dense media. Through the combined use of ultrafast time gating, polarization gating, and spatial filtering, photons that propagate without interference (i.e., ballistic photons) are preferentially detected over photons that undergo significant beam steering or multiple scattering. In addition to ballistic photon imaging, the delivered diagnostic hardware will provide an ultrafast laser source that is the key element for a number of emerging diagnostic approaches, including Terahertz spectroscopy and ultrafast coherent anti-Stokes Raman scattering. In this manner, the current effort will lay the foundation for a versatile ultrafast laser diagnostic system for harsh chemically reacting environments.