  The results of a beam test performed at the KEK PS in June 2005 are
presented. Drift properties of an argon-isobutane mixture have been accurately
measured and compared with predictions at magnetic fields between 0 and 1
Tesla. The r.m.s. point resolution of a padrow is compared with simulation and
with an analytical calculation. The fundamental limitations due to detector
geometry and gas properties are reviewed and the measured performances of the
detector are found to be close to this limit. A numerical application to the
case of a Linear Collider TPC is presented.
