µLAN DATA ACQUISITION OVERVIEW

Rates

The data acquisition was designed to handle a beam rate of up to 2 x 105 incident muon/sec. In addition it permits the collection of data in three modes: (i) only CAEN data, (ii) both CAEN data and WFD data, and (iii) all CAEN data with pre-scaled WFD data.

The CAENs record both the electron hits in the inner/outer tiles and the muon stops in the t0 counter. Assuming each incoming muon produces one t0 counter hit and each decay electron produces one inner tile hit and one outer tile hit, the CAEN data rate is 1.2 MBytes per 10 5 muons (the CAEN generates one 32-bit word per hit). The CAENs thus produce a total of 1.2 TB of data per 1011 muon decays.

The WFDs record the pulse shapes of the scintillator pulses from the t0 counter. The WFD frontend was designed to permit processing of raw pulse-shape data into compressed pulse-parameter data. The raw data comprises four 32-bit words per WFD pulse and contain the time, area, height, pedestal and island index. Thus parametrized singles data will yield 1.6 MB/sec at 105 muon/sec and 1.6 TBytes per 1011 muon decays.

Two difficulties are associated with the WFD readout - firstly the readout rate from WFDs is limited to about 8 MB/s and secondly the WFDs generate a large volume of pulse-shape data. Thus we expect to run the experiment with either (i) short WFD+CAEN runs and long only-CAEN runs or (ii) CAEN data with prescaled WFD data. Both modes of operation are permitted by the DAQ setup.