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    User name D. Parno

    Log entry time 17:42:12 on January 29, 2008

    Entry number 227922

    Followups:

    keyword=DAC Scan of FADC

    I scanned the DAC offsets of the Compton FADC for a -2500 V PMT voltage and gating of (40 = 100 microseconds) and integration window of 13000 (32.5 milliseconds). The results were dramatic and Rich and I are not sure what to make of them. The minimum (at a DAC value of 38000) puts the pedestal at about 1990 rau. There were about 10,000 events per run.

    Fig. 1 shows a plot of accdiff rms (pedestal noise) as a function of DAC offset.

    Run numbers were as follows:

    60274 DAC: 38000 Accdiff RMS: 0.66e6 60275 DAC: 43000 Accdiff RMS: 2.579e6 60276 DAC: 48000 Accdiff RMS: 3.395e6 60277 DAC: 33000 Accdiff RMS: 2.759e6 60278 DAC: 28000 Accdiff RMS: 3.313e6 60279 DAC: 30000 Accdiff RMS: 3.261e6 60280 DAC: 38000 Accdiff RMS: 0.64e6 60281 DAC: 38000 Sampling run to determine pedestal location




    Figure 1