Operating experience with the MARK J time expansion chamber

Abstract A new drift chamber concept with a special charge-sampling geometry, pulse shaping electronics and a 100 MHz flash ADC readout was for the first time operated in a colliding e + e − beam environment. The detector formed part of the MARK J experiment at PETRA (DESY) during the last year before its final shutdown in November 1986. Operated with a CO 2 /i-C 4 H 10 gas mixture at 1.9 bar, an intrinsic resolution of 40 μm for Bhabha events has been achieved.