  The dynamics of the positive ions created by particle interactions inside
argon time projection chambers plays an important role in characterizing the
next generation of massive detectors planned for the direct search for dark
matter and the study of neutrino properties. We have constructed a 1 L liquid
argon chamber (ARION: ARgon ION experiment) with a high voltage pulse generator
capable of injecting, in a controlled manner, a sizeable ion current into the
drift region. This chamber is capable of reproducing a volume charge similar to
that found in large detectors, allowing its effects to be studied
systematically. New experimental results regarding ion dynamics in the liquid
and direct demonstration of ion feedback from the gas to the liquid are
discussed in this paper. In addition, a novel technique to measure the drift
velocity of argon ions is introduced along with preliminary results obtained in
gas.
