Laser ionization and radiofrequency sustainment of high-pressure seeded plasmas

Summary form only given. The feasibility of using a low-ionization potential organic seed gas to initiate a high-pressure plasma discharge is examined. Laser photoionization of the working gas creates a high-density initial condition that eliminates the need for capacitive breakdown of the gas to form the plasma. The seed gas, tetrakis(dimethylamino)ethylene, has an ionization potential of 6.1 eV, and is ionized by ultraviolet laser photon absorption forming a plasma column. The plasma is sustained through inductive coupling of radiofrequency fields to the plasma through collisional damping. The laser initiation of 2-6 mTorr of the seed gas in 1-150 Torr of argon is accomplished producing steady-state plasma densities of the order n/sub e//spl sim/10/sup 12/ cm/sup -3/ in a volume of 300 cubic centimeters with RF power densities of 5-10 Watts per cubic centimeter. The dependence of the complex antenna impedance on the plasma density and neutral gas pressure is examined. The coupling can be described by absorption of the fields into a lossy plasma medium. Antenna design is aided by understanding the radial absorption profile of the inductive radiofrequency fields, and how these fields are excited by various antenna designs.