  The ELISE test facility hosts a RF negative ion source, equipped with an
extraction system which should deliver half the current foreseen for the ITER
Neutral Beam Injector, keeping the ratio of co-extracted electrons to ions
below 1. An important tool for the suppression of the co-extracted electrons is
the magnetic filter field, produced by a current flowing in the plasma grid,
the first grid of the 3 stage extraction system. To boost the source
performances new concepts for the production of the magnetic filter field have
been tested, combining the existing system with permanent magnets attached on
the source walls. The topologies of these new magnetic configurations influence
the beam particles trajectories in the extraction region, with consequences for
the overall beam optics. These effects will be characterized in this article by
studying the angular distribution of the beam particles, as measured by the
Beam Emission Spectroscopy (BES) diagnostic. The behavior of the beam will be
studied also through the measurements of the currents flowing on the grounded
grid (the third grid) and on the grid holder box surrounding its exit. The main
finding is that the broader component of the beam increases when the magnetic
field is strengthened by permanent magnets, i.e. in the cases in which most of
the co-extracted electrons are suppressed.
