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    User name P. Monaghan

    Log entry time 23:51:01 on March 14, 2005

    Entry number 141503

    keyword=N1-5 channel adc and tdc plots for runs 2655 and 2659

    Shown below are the adc and tdc plots for both the left and right pmts and the adc vs tdc plots for the left and right pmts, for channel N1-5 in the neutron detector. Figure 1 shows the plots for run 2655 which was the first long carbon production run of this evening after beam was restored from being off since this morning. Figure 2 shows the plots for run 2659 which was taken about two hours later. The adc spectra in the online detector replays showed a decrease in the spectrum for the second run (2659). The plots below show that the pmts appear to have much more events at higher adc/tdc channels for run 2655 than for 2659. Does this mean that the tube is noisy at high rate for a while when beam is first restored and then it somehow settles down as time goes on? Why would we be seeing this in both the right and left pmts on the same bar, even though the signals from each pmt go through separate (ie left and right) electronics modules (amplifier, discriminator etc.)? Comments, questions and suggestions are welcome. Note, these plots are for a full analysis of all 200000 events in each run and the only 'cut' included is asking for a single hit in the first plane - "NA.nd.p1.npadhit==1".

    Figure 1

    Figure 2