The Time Expansion Chamber and Single Ionization Cluster Measurement

The time expansion chamber (TEC), a new type of drift chamber, allows the measurement of microscopic details of ionization. The mean drift time interval from subsequent single ionization clusters of a relativistic particle in the TEC can be made large enough compared to the width of the anode signal to allow the recording of the clusters separately. Since single primary electrons can be detected, the cluster counting would allow an improved particle separation using the relativistic rise of primary ionization. In another application, very high position accuracy for track detectors or improved energy resolution may be obtained. Basic ionization phenomena and drift properties can be measured at the single electron level.