Nuclear Instruments and Methods in Physics Research A 535 (2004) 294–298 TPG construction V. Ableev a , F. Ambrosino b , M. Apollonio c,Ã , P. Bene d , A. Blondel d , M.G. Catanesi e , G. Chiefari b , P. Chimenti c , P. Favaron a , U. Gastaldi a , S. Giani f , G. Giannini c , E. Gschwendtner d , J.-C. Legrand f , M. Lollo a , G. Musso f , M. Napolitano b , R. de Oliveira f , V. Palladino b , E. Radicioni e , J.-P. Richeux d , M. Rigato a , L. Ropelewski f , L. Roscilli b , G. Saracino b , F. Sauli f , P. Temnikov a a INFN, Laboratori Nazionali di Legnaro (Pd), Italy b Universita` e sezione INFN, Napoli, Italy c Universita` e sezione INFN, Trieste, Italy d Universite´de Geneve, Geneva, Switzerland e INFN, sezione di Bari, Italy f CERN, Geneva, Switzerland Available online 12 August 2004 Abstract 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 (30cm diameter) and a read-out board (30cm diameter active surface) covered with 710,000 hexagonal pads of 300 mm size. Aligned pads are connected in parallel to onestripoutofthreesetsof576parallelstrips(500 mmpitch).Thethreesetsofstripsrunat120  fromeachotherandat three different depths inside the hexaboard multilayer structure. Each strip is read out by FADC electronics. The TPG- headisunderinitialtestinasmallcontainerwithadriftvolume33mmlongandof30cmdiameter.A150cmlongdrift volume inside a 0.7T solenoidal magnetic field has been prepared by using HARP-TPC instrumentation as test bed. r 2004 Elsevier B.V. All rights reserved. PACS: 29.40.Gx Keywords: TPC; GEM; Read-out TPG [1] is the acronym for a gas imaging chamber with TPC geometry [2] (toroidal or cylindrical drift volume with drift electric and magnetic field both uniform and parallel to the cylinder axis), which uses GEM foils for electron multiplication in gas [3] and a read-out board covered by hexagonal pads that are read out by strips running below the board surface (hexaboard [4–6]). ARTICLE IN PRESS www.elsevier.com/locate/nima 0168-9002/$-see front matter r 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2004.07.136 Ã Corresponding author. E-mail address: marco.apollonio@ts.infn.it (M. Apollonio).