Double NuMI triggers
Tricia and Minerba reported that every NuMI spill in run 11222 was duplicate. I.e., the same event would appear
twice in the file, but with different trigger number.
This is an odd one. The timestamps are not actually identical. See CRL entry:
copied below for convenience. Also attached is plot of the difference distribution.
Monday, January 24, 2011 17:48:35 CST: General: 2239: Peter Shanahan
Investigating double-NuMI-trigger problem in
Looking at 11222, subrun 2, I find,
1) Only NuMI triggers show this behavior. BNB
and Cosmics, which both exist in this subrun, are
That would seem to rule out multiple GlobalTrigger or SpillServer processes as the
2) Every NuMI trigger in this subrun is
duplicated, i.e., it never failed to happen.
3) It seems that the first event (in the file) of
each pair has the higher trigger number.
4) The time difference between the two triggers
in each pair fall into only the following values:
+/- 24 NOvA clock ticks, less than 10% of the time
(The difference I measure is in nanoseconds, in
this case 375ns)
+/- 28 NOvA clock ticks, the remaining times.
(In nanoseconds, this shows up as +/-437 or +/- 438 nanoseconds)
The distribution of these 4 values is random,
not following any apparent time series.