When the magnetic field is switched on, the particles in a dust cluster rotate as a whole like a rigid body. And the angular velocity of the dust cluster increases as the magnetic field strength increases. But interestingly, the cluster does not go under uniform rotation especially when the magnetic field is weak (0 to 15G). The angular velocity of the cluster actually accelerates and then decelerates at a particular angle (see Figure 1.2.1). This phenomena observed in our experiment and also by other experimental groups is what we defined as "Periodic Pause".

 

Figure 1.2.1 - Angle versus time for the two particles in a Planar-2 dust cluster configuration. The rigidity of the crystal is shown from the constant phase difference between the two particles. And the periodic pause is shown from the slope of the graph. This visualization is drawn using Microsoft Excel XP.

However, the reason why such periodic motion occurs in the cluster rotation is unknown. Since at stronger magnetic field settings, the clusters goes under uniform rotation, it would appear that the existence of the periodic pause is dependent on the magnetic field strength. And in order to obtain this relationship between the periodic pause, one method  is to generate a 3-D phase diagram for the cluster rotation.
Since conventional graphing packages (e.g. MS Excel, Kaleidagraph,etc) are either insufficient or incapable of creating a 3-D plot, a better data visualization method is necessary to obtain the information. In this project, several software packages were used to provide us a scientific visualization of how the periodic pause of the cluster changes as a function of magnetic field strength.