Radio frequency sustainment of laser initiated seeded high-pressure discharge

Abstract

Summary form only given, as follows. The radio-frequency power required to initiate a discharge at high gas pressure (>100 Torr) is quite high. But once the gas breakdown has occurred and discharge is initiated, the radiofrequency power can be much more efficiently absorbed by the plasma through inductive coupling of the wave fields. The ohmic heating of the antenna and the coil current required to sustain the discharge reduce significantly. The discharge is initiated by photoionization of a low ionization potential (6.1 eV) organic gas tetrakis(dimethylamino)ethylene or TMAE, using a high power excimer laser (wavelength 193 nm and a maximum laser energy of 300 mJ for 20(/spl plusmn/) ns half-pulse width) seeded in a high-pressure gas. The discharge is then sustained by coupling 1-25 kW of radio frequency power through a five turn helical antenna using a capacitive matching network. Recent results with the laser-initiated discharge of 2-6 mTorr of seed gas with a high-pressure background gas (/spl ges/760 Torr of nitrogen and argon mix) will be presented. A large volume plasma 300-500 cm/sup 3/ in the density range 10/sup 12/-10/sup 13/ cm/sup -3/ is produced. The influence of the accurate timing of the laser and radio frequency pulses along with the radio frequency power level and gas mix to produce the high-density plasma will be discussed.