Modified distributed electron cyclotron resonance ion source for the production of large diameter ion beams

The work presented in this article concerns the conception and the study of a multiantenna electron cyclotron resonance (ECR) ion source at 2.45 GHz d edicated to the surface treatment of large area materials. In this original device, a microwave plasma is created in a 20 cm in diameter ionization ch amber. The 15 cm in diameter extracted ion beam has a current density of ab out 1 mA/cm(2). The applicator is an N-way coaxial power divider in which t he N=20 antennas are individually magnetized by internal SmCo bars in order to produce ECR zones in their vicinity. Moreover, the microwave plasma is confined by a multicusp magnetic structure surrounding the ionization chamb er. The choice of the source geometry has been guided by the study of some theoretical considerations such as the characteristic diffusion length, the minimum breakdown field, and the penetration depth of the wave into the pl asma. Simulations both of the electromagnetic field and the static magnetic field distribution have been carried out in order to validate the final ch oice of the source geometry. A full characterization of the ECR plasma and of the extracted ion beam was made with different experimental techniques. These results allow us to localize the plasma creation zones inside the ion ization chamber. A 120 mA singly charged argon ion beam with a profile homo geneity better than +/-5% over 10 cm was obtained 5 cm downstream the extra ction system with a 300 W microwave power and a neutral argon pressure of 1 0(-3) mbar in the ionizing chamber. (C) 2001 American Institute of Physics.