Methods and apparatus for generating strongly-ionized plasmas with ionizational instabilities

A method of generating a strongly-ionized plasma, the method comprising:

• a) supplying feed gas proximate to an anode and a cathode assembly;
• b) generating a weakly-ionized plasma by applying a first voltage between the anode and the cathode assembly, the first voltage having at least one of a controlled amplitude and a controlled rise time that prevents forming an arc between the anode and the cathode assembly, the magnitude and the rise time of the first voltage being sufficient to ignite the feed gas;
• and
• c) generating a strongly-ionized plasma from the weakly-ionized plasma by applying a second voltage between the anode and the cathode assembly, the second voltage having at least one of a controlled amplitude and a controlled rise time that prevents forming an arc between the anode and the cathode assembly, the magnitude and the rise time of the second voltage being sufficient to shift an electron energy distribution in the weakly-ionized plasma to higher energies that increase an ionization rate which results in a rapid increase in electron density and a formation of the strongly-ionized plasma.

A method of generating a strongly-ionized plasma, the method comprising:

• a) supplying feed gas proximate to an anode and a cathode assembly;
• and
• b) applying a voltage pulse between the anode and the cathode assembly with at least one of a controlled amplitude and a controlled rise time that prevents forming an arc between the anode and the cathode assembly, the voltage pulse comprising:
• a first peak voltage having a magnitude and a rise time that is sufficient to ignite a weakly-ionized plasma from the feed gas;
• and a second peak voltage having a magnitude and a rise time that is sufficient to shift an electron energy distribution in the weakly-ionized plasma to higher energies that increase an ionization rate resulting in a rapid increase in electron density and a formation of the strongly-ionized plasma.

An apparatus for generating a strongly-ionized plasma, the apparatus comprising:

• a) means for supplying feed gas proximate to an anode and a cathode assembly;
• b) means for generating a weakly-ionized plasma from the feed gas;
• c) means for shifting an electron energy distribution in the weakly-ionized plasma to higher energies by controlling at least one of an amplitude and a rise time of a voltage applied between the anode and the cathode assembly to prevent forming an arc between the anode and the cathode assembly, the voltage increasing an ionization rate which results in a rapid increase in electron density and a formation of the strongly-ionized plasma from the weakly-ionized plasma;
• and
• d) means for sustaining the strongly-ionized plasma for greater than 200 μsec.