Patent ID: 7462293

Claim:
A method of monitoring plasma, comprising the steps of: inserting and attaching an insulating pipe into and to a chamber in or into which the plasma is created or introduced; inserting a coaxial cable, which has a probe portion formed by exposing a front core wire of the coaxial cable, into the insulating pipe in the axial direction of the insulating pipe; in a first continuous state where the plasma does not exist in the chamber, batch obtaining first frequency characteristics at a plurality of measurement locations with respect to reflection coefficients of electromagnetic waves irradiated from the probe portion placed in the insulating pipe; in a second continuous state where the plasma exists in the chamber, batch-obtaining second frequency characteristics at the measurement locations with respect to the reflection coefficients of the electromagnetic waves irradiated from the probe portion placed in the insulating pipe; and measuring plasma absorption frequencies at the measurement locations based on the first and the second frequency characteristics.