Optical return study for common surface preparations used in Photon Doppler Velocimetry

We present detailed measurements of the bidirectional reflectance distribution function (BRDF) for common surface preparations and materials used in Photon Doppler Velocimetry (PDV), i.e. four different surface preparations (Scotch-Brite hand and drill roughened, ball-rolled, and grit blasted), and four different materials (copper, aluminum, stainless steel, and tantalum). These measurements employ a conventional PDV probe and obtain diffraction limited angular resolution with 10 pW accuracy and 2.6% repeatability. In addition to scattering data, we employ scattering theory and simulations to accurately emulate the measured data. We also present a straightforward method to derive the average scattering distribution from surface profilometry and note several qualitative aspects of the scattering data which may help to optimize PDV signals.