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    User name silwal

    Log entry time 18:09:50 on August28,2009

    Entry number 286642

    keyword=Happex det linearity studies with led pulsers

    Baseline led pulsing from 6-750 KHz
    Diff led pulsing at 5 KHz

    On the plot below, on the first one, the vertical axis is the adc counts. Blue points are with baseline only, red points are baseline+diff.
    The total intensity from the led seems to be changing grossly with baseline frequency. We would expect the intensity to increase linearly with frequency, but it is not what we observe. It is probably because of the led being pulsed at very low currents, so low that any thermal changes in the led is affecting the amount of raditaion emitted. The PMT is unlikely to be the source of the intensity change observed below.

    The second plot is what we would expect for a linear PMT. The differences in the intensity seen by the PMT between the diff led on and off is fairly independent of the amount of light incident on the PMT.

    Det: Bugs Bunny, Joe/Base H-C, right arm

    FIGURE 1