Electron and ion energies in plasmas generated by the electron-cyclotron-resonance mechanism

A theory is developed for the electron-cyclotron-resonance (ECR) plasmas, and an experiment is carried out to compare the theoretical predictions and experimental measurements. Several points are noteworthy from the theory and from experiment for electron temperature. First, electron temperature is inversely proportional to the square root of the chamber pressure. Second, electron temperature in a high-pressure (p≳1 mTorr) chamber is almost constant as the microwave power increases. Third, two components of electron temperature are observed in a low-pressure (p<1 mTorr) chamber. Fourth, energetic electrons are mostly concentrated around the ECR region. Fifth, overall electron temperature may display anisotropic behavior in a low-pressure chamber. A theoretical model of an ion acceleration mechanism deep inside ECR plasmas is developed, based on the ambipolar diffusion. It is found that the mean ion energy is proportional to the electron temperature and inversely proportional to the square of the density variation length. Therefore, the ion energy in a uniform plasma is negligibly small.