  We describe an experimental setup comprised of a discharge source for
supersonic beams of metastable helium atoms and a magneto-optical trap (MOT)
for ultracold lithium atoms that makes it possible to study Penning ionization
and associative ionization processes at high ion count rates. The cationic
reaction products are analyzed using a novel ion detection scheme which allows
for mass selection, a high ion extraction efficiency and a good
collision-energy resolution. The influence of elastic He-Li collisions on the
steady-state Li atom number in the MOT is described, and the collision data are
used to estimate the excitation efficiency of the discharge source. We also
show that Penning collisions can be directly used to probe the temperature of
the Li cloud without the need for an additional time-resolved absorption or
fluorescence detection system.
