Biased-electrode operation of electron cyclotron resonance ion sources

In order to supplement our investigations on the biased electrode in electron cyclotron resonance ion sources, we have carried out dedicated measurements with a special double structure (ring plus disk) electrode. This geometry allows to separate two mechanisms contributing to the “biased disk effect”: the creation of secondary electrons at the disk and the reflection of plasma loss electrons by the potentials of the disk. At sufficiently high ring-electrode potentials the axial electron losses can be blocked completely. From the experimental results, it is suggested that electrostatic blocking is the main contribution to the biased electrode effect.