Abstract A time projection chamber (TPC) is proposed in which the gas amplification is obtained in a single parallel gap between a transparent cathode grid and an anode plate. The anode is segmented into circular pad rows for rφ measurement by centroid finding and into circular strips for d E/d x sampling. This technique offers (a) higher rφ resolution (up to a factor 2) due to the suppression of the major error source, the combined effect of ionization fluctuations and E× B and track angle smearing, (b) better two track resolution (up to a factor 4, in principle), and (c) substantially reduced positive ion feedback. In addition, there results a simpler construction, less dead space and slower ageing by deposit formation. With Ar/CH 4 (80/20%) a maximum gain above 10 5 was obtained in a single amplification gap. Positive ion feedback was found smaller than 4%. The properties of this detector and first test results will be discussed.