µLAN DATA ACQUISITION OVERVIEW

Timing

The DAQ is organized to accumulate the data in time segments of order of 4-40 ms (the time segment is defined in hardware by a gate generator). Much shorter time segments would cause the frontend synchronization to be too time consuming and much longer time segments would cause the WFD memory to overflow (this makes the ideal time segment a function of incident muon rate).

The CAEN frontend process synchronizes the readout of time segments from the CAEN crate and the WFD crate. First the CAEN frontend process generates a start pulse that fires the gate generator and defines the time segment (the time segment is the start input for the CAEN module and the WFD module). Then the CAEN frontend process polls the gate generator to identify the completion of the time segment. On identifying time segment completion the CAEN frontend process then informs the WFD frontend process to start the readout and processing of WFD data. On completing the readout and processing of WFD data the WFD frontend process then informs the CAEN frontend process its finished. Once the CAEN frontend and WFD frontend have completed their readout a new start pulse is generated and a new time segment is begun.

CAENs may be readout while acquiring data and therefore their readout is occuring continuously during the time segment. However WFDs may not be readout while acquiring data and therefore their readout is occuring immediately following the time segment. Consequently the CAEN readout introduces very little deadtime whereas the WFD readout induces significant deadtime.