Method and apparatus for determination and control of plasma state

A plasma processing system comprising:

• a plasma chamber;
• a plurality of open resonators provided within said plasma chamber, said plurality of open resonators being configured to produce microwave signals;
• a plurality of detectors configured to detect the microwave signals and measure a mean electron plasma density along paths of the microwave signals within a plasma field of said plasma chamber;
• and
• a processor configured to receive a plurality of mean electron plasma density measurements from said detectors that correspond to locations of said plurality of open resonators.

A plasma processing system comprising:

• a plasma chamber;
• means for measuring mean electron plasma density along a path at a plurality of locations within a plasma field in said plasma chamber;
• and
• means for calculating plasma density within the plasma field as a function of position using the measured mean electron plasma density.