Progress in TPG Construction

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 μm size. The aligned pads are connected in parallel to one strip out of three sets of 576 parallel strips (500 μm 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.