Overdense Plasma Production Using Electron Cyclotron Waves

The density limit in ECR plasma production is overcome using electron cyclotron waves. The plasma of 3×10 13 cm -3 density is achieved by parallel injection of circularly polarized microwaves with a frequency 2.45 GHz, corresponding to a 400 times higher density than ordinary mode cutoff. It is found that the plasma is produced in the high field side region between the incident position and the ECR point, and this is due to the generation of high energy electrons and the Doppler-shifted cyclotron resonance.