Influence of the secondary electrons emitted by a cylindrical metal-dielectric structure on the Frankfurt 14 GHz electron cyclotron resonance ion source performances

Previous research allowed us to develop highly efficient electron emissive metal-dielectric (MD) structures, which are suitable to be used as sources of secondary electrons in electron cyclotron resonance ion sources (ECRIS). First tests have been performed replacing the stainless steel disk of the Frankfurt 14 GHz ECRIS by a MD structure. This method was recently extended by inserting a MD cylinder (150 mm long and 58 mm in diameter) into this s ource. The experiments were performed with pure argon as source gas and wit h gas mixing (argon+oxygen). In this contribution, the performance with MD cylinder is compared to that of the standard source (stainless steel plasma chamber) and to the case, where a cylinder of technical aluminum was insta lled. With the MD cylinder the yield of highly charged ions from the ECRIS are significantly enhanced. For Ar16+ ion current enhancement factors of up to 50 were obtained. (C) 2000 American Institute of Physics. [S0034-6748(0 0)53002-0].