X-ray Doppler Velocimetry: An imaging diagnostic of 3D fluid flow in turbulent plasma

We describe a novel technique for measuring bulk fluid motion in materials that is particularly applicable to very hot, x-ray emitting plasmas in the high energy density physics (HEDP) regime. This X-ray Doppler Velocimetry technique relies on monochromatic imaging in multiple closely-spaced wavelength bands near the center of an x-ray emission line in a plasma, and utilizes bent crystals to provide the monochromatic images. Shorter wavelength bands are preferentially sensitive to plasma moving toward the viewer, while longer wavelength bands are preferentially sensitive to plasma moving away from the viewer. Combining multiple images in different wavelength bands allows for reconstruction of the fluid velocity field integrated along the line of sight. Extensions are also possible for absorption geometries, and for three dimensions. We describe the technique, and we present the results of simulations performed to benchmark the viability of the technique for implosion plasma diagnosis.