I. Introduction
TPG is the acronym for Time Projection Chamber [1] with GEM amplification, hexaboard read-out and FADC electronics. TPG [2] uses GEM foils [3] for electron multiplication and a read out board with hexagonal pads connected to three sets of strips at 120 degrees [4]–[6]. The principle and practical advanctages of the choice of GEM and hexaboard to equip a TPC imaging chamber have been discussed in [1], [7] and summarized in [8]. The use of GEM foils in the multiplication region introduces several advantages [4]:
decoupling of multiplication and signal generation processes;
flexibility in the design of the read-out plane;
minimization of the positive ion feedback into the drift region;
minimization of distortion effects.