Time-average electric field of the plasma presheath determined by analysis of the particle interactions

Summary form only given, as follows. Particle interactions were directly determined from the lateral compression of two-dimensional plasma dust crystals confined in a parabolic potential well. The shape of the parabolic potential well was confirmed by observing trajectories of single particles falling within the well. Particle trajectories are in good agreement with values calculated using gas temperatures derived from laser induced fluorescence measurements of the argon metastable velocity distributions and assuming diffusive gas scattering. Measured particle separations combined with an equation of state for the crystal were used to derive values for the particle screening length and the charge on the particles. Particle screening length and charge were measured for a range of plasma power, pressure and particle diameter (mass). Analysis of the particle heights and charge were used to derive the time average electric fields at edge of the RF driven plasma sheath. These measurements show that the particles are confined to the on the bulk plasma side of the classical Bohm point and that the sheath has an exponential spatial dependence, not linear.