Recording multiple signals on a single waveform recorder

The data acquisition system for the PBFA II accelerator is recording up to 3 signals on each of 64 LeCroy 6880 waveform recorders by separating the signals in time. The time separation is done using both the natural delay times in the accelerator and delay cables. Fast switches must be used to gate the signals to the recorder only during the time of interest. Phillips Scientific model 744 Quad Linear Gated Fan-in/Fan-out NIM modules are being used to switch the signals. Several problems with these switches had to be solved. The switches have a dc thermal drift and a nonlinear transfer function. This requires using a programmable function generator to measure and correct for the switch/6880 amplitude transfer function. The switches have a .1Ω output impedance. This produces spurious signals on recorded waveforms due to reflections from small deviations from 50Ω at the 6880 input. This problem was solved using a 5X attenuator at the switch output. Phillips has recently introduced a new model 7145 switch which should solve some of the problems encountered with the 744