Flow Characterization of Plasma Field Using Filtered Rayleigh Scattering and Its Optical Characterization Using Shack-Hartmann Sensor

ABSTRACT: A varying density field in a plasma chamber is diagnosed using filtered Rayleigh Scattering (FRS) to obtain spatially and temporally resolved densities in a planar field. By tuning a narrow band laser light to the absorption line of a molecular iodine cell, unwanted light scattered from the windows in the path of the laser beam is blocked from reaching the detector. To test this proposed flow diagnostics, a plasma discharge facility that creates a variety of density conditions and with excellent optical access will be fabricated. The measured density fluctuations and their distributions enable the characterization of flow field, information that is needed towards the development of onboard optical sensors, and for transmitting high-quality communication signals. To gauge the effects of the plasma field on the quality of an optical beam, a laser beam is traversed through it and the wavefront distortions are measured with fast temporal resolution using a Shack-Hartmann wavefront sensor that employs a high frame-rate camera. BENEFIT: With renewed interest in hypersonic flights, Expendable Launch Vehicles (ELV) and Reusable Launch vehicles (RLV) represent the future of space applications. The proposed flow diagnostic using FRS is quite easy to implement and integrate, and can be made compact and modular to be easily integrated aboard space vehicles. With private enterprises besides US Air Force and NASA entering the space launch vehicle market, there is a growing need for modular optical instruments that can interrogate flight environment under harsh conditions and thus enable the passage of high-quality communication signals.