The sixteen-channel APEX constant fraction discriminator

A sixteen-channel constant fraction discriminator (CFD) has been constructed for the ATLAS Positron EXperiment (APEX). An integrated circuit, recently introduced commercially, contains all the electronic building blocks required to construct a CFD and makes it possible to fit sixteen CFD channels into a single-width CAMAC module. An important new feature is the time-to-charge converter that is part of each CFD channel. Its calibration constant is controlled via CAMAC. The time-to-charge converter allows the use of low-cost charge-sensitive analog-to-digital converters for timing measurements.