  The output of highly charged ions from an electron cyclotron resonance ion
source (ECRIS) consists of ionic losses from a highly confined plasma.
Therefore, an increase of the output of the ions of interest always is a
compromise between an increase in the confinement and an increase of the
losses.One route towards a solution consists of attacking the losses in
directions (i.e., radial directions) that do not contribute to the required
output. This was demonstrated in an experiment (using the Kei ECRIS at NIRS,
Japan) where radial losses were electrostatically reduced by positively biasing
one set of six side electrodes surrounding the plasma in side-ward directions
attached (insulated) to the cylindrical wall of the plasma chamber. Recently
new studies were performed in two laboratories using two essentially different
ion sources. At the BioNano ECRIS (Toyo University, Japan) various sets of
electrodes were used; each of the electrodes could be biased individually. At
the Atomki ECRIS (Hungary), one movable, off-axis side electrode was applied in
technically two versions. The measurements show indeed a decrease of ionic
losses but different effectivities as compared to the biased disk.
