Production of low-electron-temperature electron cyclotron resonance plasmausing nitrogen gas in the mirror magnetic field

An electron cyclotron resonance (ECR) plasma with a low electron temperatur e (< 2eV) and high electron density (similar to 10(12) cm(-3)) was realized in a mirror magnetic field for Ar/N-2 or N-2 gas. It was found based on th e particle and power balance that the decrease in the electron temperature was due to the magnetic-mirror confinement depending on the collision cross section between electrons and neutral particles. The experimental and nume rical results suggest that diluting with N-2 gas, whose excitation cross se ction peaks at a low electron energy of about 2 eV, in the mirror magnetic field enables us to reduce the electron temperature efficiently in an ECR p lasma.