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    User name johna

    Log entry time 23:36:01 on October27,2002

    Entry number 89167

    keyword=spec_r_tc strange behavior

    spec_r_tc is quantized, in ~6ns regions (compared to the left arm, normal spectrum). Looking more closely, it is 6.4ns, corresponding to 64 TDC channels. On the assumption that it might be a problem with the TDC readout (missing or stuck bit). Checked this out by looking at the exact channel number where the peaks start and stop. The tallest peak goes from channel 2304 to 2367, or in binary:

    2304 = 100100000000
    2367 = 100100111111

    So this is consistent with the guess that the 7th bit is always reading zero, and so
    events which should occur in 2368-2431 all read out 64 channels lower. The TDC should be checked at some point. If it's just one channel, a duplicate version of the signal can be put in another channel.

    FIGURE 1

    FIGURE 2