An Application of Parallel Preprocessors in Data Acquisition

A data-acquisition system is being developed for a large-scale experiment at LAMPF. It will make use of four microprocessors running in parallel to acquire and preprocess data from 432 photomultiplier tubes (PMT) attached to 396 NaI crystals. The microprocessors are LSI-11/23s operating through CAMAC Auxiliary Crate Controllers (ACC). Data acquired by the microprocessors will be collected through a programmable Branch Driver (MBD) which also will read data from 52 scintillators (88 PMTs) and 728 wires comprising a drift chamber. The MBD will transfer data from each event into a PDP-11/44 for further processing and taping. The microprocessors will perform the secondary function of monitoring the calibration of the NaI PMTs. A special trigger circuit allows the system to stack data from a second event while the first is still being processed. Major components of the system were tested in April 1981. Timing measurements from this test are reported.