Progress in TPG construction [particle detector]

TPG is the acronym for a 3D imaging gas chamber with GEM amplification, hexaboard read-out and FADC electronics. We have constructed a TPG-head with three GEM foils (30 cm diameter) and a read-out board (30 cm diameter active surface) covered with 710000 hexagonal pads of 300 /spl mu/m size. The aligned pads are connected in parallel to one strip out of three sets of 576 parallel strips (500 /spl mu/m pitch). The three sets of strips run at 120 degrees from each other and at three different depths inside the hexaboard multi-layer structure. Each strip is read by FADC electronics. The TPG-head is under initial test in a small container with a drift volume 33 mm long and of 30 cm diameter. A 150 cm long drift volume inside a 0.7 Tesla solenoidal magnetic field has been prepared by using HARP-TPC instrumentation as a test bed.