We are developing a novel diagnostic for measurement of bulk fluid motion in materials, that is particularly applicable to
very hot, x-ray emitting plasmas in the High Energy Density Physics (HEDP) regime. The X-ray Doppler Velocimetry
(XDV) technique relies on monochromatic imaging in multiple x-ray energy bands near the center of an x-ray emission
line in a plasma, and utilizes bent imaging crystals. Higher energy bands are preferentially sensitive to plasma moving
towards the viewer, while lower energy bands are preferentially sensitive to plasma moving away from the viewer.
Combining multiple images in different energy bands allows for a reconstruction of the fluid velocity field integrated
along the line of sight. We review the technique, and we discuss progress towards benchmarking the technique with
proof-of-principle HEDP experiments.
A Chirped Pulse Amplification (CPA) mode of operation is being developed on the VULCAN high power Nd:glass laser system, at the Rutherford Appleton Laboratory (RAL). Experiments have been carried out using an interim configuration yielding pulses of up to 30 J on target of 2.4 picoseconds length at focused intensities up to 4 X 1017 W cm-2, with contrast ratio of 106. In the CPA technique the amplification of a stretched pulse to high energy followed by recompression provides a means of delivering a higher peak power to target than can be propagated through the laser system due to non-linear effects and component damage thresholds. In the system described here a grating pair is used to stretch a transform limited pulse of 2 ps, to 80 ps prior to amplification to high energy (80 J). The linear stretch produced by the gratings enables the pulse to be recompressed without pedestal. Recompression to the 10 TW level by a second grating pair is carried out in a vacuum propagation and reflective focusing system to avoid non-linear effects in air, windows and lenses.