  A time projection chamber (TPC) based on a gaseous chamber with micro pixel
electrodes (micro-PIC) has been developed for measuring three-dimensional
tracks of charged particles. The micro-PIC with a detection area of 10 cm
square consists of a double-sided printing circuit board. Anode pixels are
formed with 0.4 mm pitch on strips aligned perpendicular to the cathode strips
in order to obtain a two-dimensional position. In the TPC with drift length of
8 cm, 4 mm wide field cage electrodes are aligned at 1mm spaces and a uniform
electric field of about 0.4 kV/cm is produced. For encoding of the
three-dimensional position a synchronous readout system has been developed
using Field Programmable Gate Arrays with 40 MHz clock. This system enables us
to reconstruct the three-dimensional track of the particle at successive points
like a cloud chamber even at high event rate. The drift velocity of electrons
in the TPC was measured with the tracks of cosmic muons for three days, during
which the TPC worked stably with the gas gain of 3000. With a radioisotope of
gamma-ray source the three-dimensional track of a Compton scattered electron
was taken successfully.
