OPTICAL-EMISSION AND MICROWAVE FIELD INTENSITY MEASUREMENTS IN SURFACE WAVE-EXCITED PLANAR PLASMA

A large-planar (22 cm diam.) high-density (similar to 2 x 10(12) cm(-3 )) plasma is produced in argon gas at 140 Pa by 2.45 GHz-1 kW discharg es, using a microwave launcher of small slot antennas. The two-dimensi onal distributions of optical emission intensities as well as microwav e field intensities are measured near the plasma surface irradiated wi th microwaves. Both the optical emission and the microwave field clear ly show stationary patterns of azimuthal mode m = 3 and radial mode n = 3 at higher pressures (140 Pa), while a mode change to m = 6 and n = 2 is observed at lower pressures (44 Pa). These patterns are attribut ed to the excitation and absorption of standing surface waves near the cutoff layer.