The Particle Image Velocimetry (PIV) system is used to make direct, two-dimensional measurement of the dust particle velocities in the dusty plasma. These dusty plasma experiments at Auburn represent the FIRST application of PIV to dusty plasma experiments [ref. E. Thomas, Jr., Phys. Plasmas, 6, 2672 (1999)]
In the PIV technique, two laser pulses (one each from a pair of frequency-doubled 25 mJ, Nd-YAG lasers) are expanded into a 2-D "sheet" by a 50 mm cylindrical lens. The pulses are separated by a time interval dt andilluminate the dust particles. The laser pulses are synchronized to a CCD camera so that each firing of the laser appears on a single CCD image frame. Each pair of images are cross-correlated and the displacement of the particles is recorded. In this manner, with a known time interval, and a local displacement, a 2-D velocity profile of the dust particle motion is computed. A schematic of this technique is shown below.
It is a fluid-like measurement in that each computed velocity vector represents an average over several dust particles within field of view. As compared to other velocimetry techniques (e.g., laser doppler velocimetry) which measure one particle at a time, PIV is a volumetric measurement... that is the PIV measurement is performed over the entire illumated region. This it provides a "snap-shot" of the average motion of ALL of the particles.
Click HERE for a link to one of the first PIV measurements.
Click HERE for a more extensive listing of measurements from DPX.
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