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    User name R. Michaels

    Log entry time 11:13:10 on July17,2003

    Entry number 104247

    This entry is a followup to: 104243

    keyword=Event type NOT a problem

    It should be noted that because of the trigger supervisor (TS) programming, the
    CODA event type is not necessarily the trigger type. We program the TS such that
    if a trigger type N appears alone it will be event type N, but if two trigger types
    appear and overlap within10 nsec we must define the CODA event type. Due to
    long experience with people getting confused, we decided to program all overlaps as event type 5.
    Note, there are no trigger 5 plugged in. The way to see what triggers
    were involved is to look at the so-called trigger latch pattern, which is a TDC 1877
    in ROC3, slot 5, channels 1-16 (see adaql1:~adaq/evchk/README and associated
    code there). Below is a 2D plot showing correlation of CODA event type to trigger
    latch pattern for run 21381. Although we tried before the experiment to make sure
    trigger 3 arrives well before (30 nsec) all other triggers, evidently with beam T2 and
    T3 overlap within 10 nsec, and the prescale factors were one. If you put ps2 high
    (as I suggest you do) and keep mostly T3 you would see mostly CODA event type 3.
    I suggest the experiment start looking at this trigger latch pattern.

    FIGURE 1