User name R. Michaels
Log entry time 03:41:15 on October14,2000
Entry number 50366
This entry is a followup to: 50335
Followups:
keyword=origin of double peaksJeff was worried about double peaks on L-arm, S1 and S2
paddle 2 TDCs. Here I plot for PMT on S1(left). The double
peaks originate from multiple track events. The PMT multiplicity
plotted shows a high rate of more than 2 PMT hits per plane. The
double peak disappears if I make cuts do demand only one track on
the 'gold plated S-Ray' pattern (lower left plot). If there are multiple hits
I get the plot in the lower right histogram, showing a nearly 1:1 ratio of
double peaks. Generally we get multiple peaks and shoulders in
TDCs because different PMTs can strobe the MLU. In the case
of paddle 2, it is probably because there is a ~10 nsec mismatch in
timing between a neighboring paddle, for instance because we put
signals on paddle 3 through a linear fan-in and we didn't perfectly
match the timing (10 nsec is quite possible). Is it a problem ? I don't
think so, but the timing algorithm in ESPACE might need upgrading
for this high rate environment. The only subtlety is if we get EARLY
strobes coming from photons (or something that doesn't make a track)
that accompany the tracks, these can kill the trigger for the tracks. For
this reason the MLU strobe timing should exceed the split of paddle timing.
The MLU strobe time for beam is >= 22 nsec for the S1 and >= 12 for S2 (ouch).
We could reduce the split using remote delays.
FIGURE 1
