Time Projection Chambers for tracking and identification of radioactive beams

Time Projection Chambers (TPC) with delay-line readout have been built as position sensitive detectors for high-resolution experiments at the magnetic spectrometer FRS at GSI. The main qualities of TPCs are a small amount of material in the active area, a high tracking efficiency (approximate to 98%), and a spatial resolution of sigma similar to 115 mu m in x-direction, measured by a delay line, and sigma similar to 50 mu m in y-direction, measured by drift time. The TPC works as a true two-dimensional detector. A multiple energy-loss measurement allows to identify light fragments (Z = 4-6) with a resolution better then sigma(Z) < 0.14. With the TPCs, several parameters of the spectrometer could be improved considerably and a higher momentum resolution of the FRS was obtained. The TPC construction, test results, and physical experiments are presented. (C) 1998 Elsevier Science B.V. All rights reserved.