Determination of the Confining Potential in Dusty Plasma Experiments

In dusty plasma experiments, the confining potential of the GEC rf Reference Cell is commonly assumed to be parabolic. There are various ways to test this assumption, many of which interfere with the plasma. We use the noninvasive method of perturbing a single particle suspended in the plasma with laser pulses. In this experiment a cw laser (532nm, 0.01.05W) supplied the radiation pressure force on a single MF microsphere. The trajectory of the particle is then analyzed to determine the confining potential. We varied the size of the confining cutout, pressure, system power, and DC bias to better understand their effects on the shape of the confining potential. The experiments showed that the potential did have a parabolic shape and that increasing the cutout size, gas pressure, and DC bias all decreased the curvature of the parabola.