APEX heavy ion counters

Abstract A large solid-angle array of low pressure multiwire proportional counters has been constructed as part of the Atlas Positron EXperiment (APEX). Eight three-element trapezoidal counters provide 360° coverage in φ and 20°–68° coverage in θ. Angle sensitivity in θ is provided by a transmission-line delay cathode, while the segmentation provides angle sensitivity in φ. Sample data are presented from the 1450 MeV 238 U + 181 Ta reaction.