Two-dimensional Measurements of the Structure of PDP Micro-discharge Plasmas Using Laser Thomson Scattering

Laser Thomson scattering (LTS) is used for measuring spatial distributions of electron density (n_e) and temperature (T_e) in micro-discharge plasmas. Two-dimensional LTS measurements both in the X (along a surface) and Z (height) directions have been performed for an alternating current plasma display panel (AC-PDP) cell. Details of the experimental arrangement are described in [1]. The configuration of the electrodes used in this experiment was similar to that of sustain electrodes of a coplanar AC-PDP. After evacuating the discharge chamber to less than 10^-5 Torr, a Ne-Ar(10%) mixture gas was introduced at different pressures (100-500 Torr). Alternating voltage pulses with a square waveform were applied between the electrodes at a frequency of 20 kHz and with a duty ratio of 1. The peak value of the applied pulse voltage was 220 V. In this study, we extended the measurements into two-dimensions, namely at different heights above and along the electrode surface, starting at 60 microns above the electrode surface. Figure 1 shows the variation of electron density with height above the electrode surface at a gas pressure of 200 Torr. One notices from the figure that the electron density increases first then gradually decreases with increasing height above the surface, and the density peak was at 100 microns above the electrode surface. The position of this density peak varied with pressures. In order to obtain information of more detailed structures of the discharge near the electrode surface, further improvement in the spatial resolution is being tried.