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User name X. Zheng
Log entry time 00:44:59 on November 24, 2009
Entry number 302244
Followups:
keyword=Quick analysis for pion trigger efficiencies
Today Diancheng changed the GC width in the VETO circuit from 50ns to
40ns. This is just "for fun", in case the observed deadtime change
exactly by 10ns.
Otherwise, the main difference between today's deadtime study and last
Friday is that: Today we are running at positive polarity. The T1 rate
is high. But the GC rate, and the PS, TS rates of each group are
low. The EN and EW rates of each group are very low. While last
friday when we ran at the negative polarity, the T1 and the GC have
roughly the same high rate, and they are dominated by electrons. The PS,
TS and EN, EW rates of each group are fractions of the total T1 or GC
rate.
The 10ns decrease in deadtime did not happen. The fractional tagger loss
on the right arm stays the same, still proportional to T1 rate, and show
a T1 deadtime of about 95ns. On the other hand, since all other rates are
low, we can exclude the possibility that this tagger loss is from any
other part of the DAQ, including GC. But it could still be from the VETO circuit. For
example, if the loss is due to PS or TS rates, the deadtime would be
10^4ns to 1microsec level, which is impossible.
The left arm, on the other hand, shows very different behavior: Last
friday's electron runs showed a T1 deadtime of about 30-35ns. Today, the
runs all show a 95ns T1 deadtime, the same as the right arm. Why this
changed is uncertain.
What is causing this T1 deadtime?
Below is a table to show numerical results of these two sets of deadtime
studies. Some of the GC or T1 rates are not shown (but for electron runs
they scale with beam current for sure). Some error bars are not shown
because I have to rerun my macro to get the error and now I don't want to
do that for all runs.
Right arm:
| Polarity | Ibeam | run# | T1 rate | GC
rate | T1 deadtime |
| e- | 95 | 14087 | 78.95k | 69.08k | 95.75
+/- 3.04ns |
| e- | 80 | 14088 | 69.02k | 60.55k | 99.00
+/- 3.52ns |
| e- | 60 | 14089 | - | - | 100.79
+/- 4.82ns |
| e- | 40 | 14091 | - | - | 105.10
+/- 5.20ns |
| e- | 20 | 14092 | - | - | 108.92
+/- 7.89 |
| e+ | 110 | 14186 | 215.74k | 43.28k | 95.56
+/- 1.98ns |
| e+ | 80 | 14185 | 158.25k | 31.68k | 89.14
+/- 2.46ns |
| e+ | 60 | 14183 | 119.85k | 24.03k | 94.43ns |
Left arm:
| Polarity | Ibeam | run# | T1 rate | GC
rate | T1 deadtime |
| e- | 95 | 14087 | 324.46k | 328.11k | 32.68
+/- 0.87ns |
| e- | 80 | 14088 | - | - | 31.51
+/- 0.98ns |
| e- | 60 | 14089 | - | - | 31.44
+/- 1.32ns |
| e- | 40 | 14091 | - | - | 33.67
+/- 1.44ns |
| e- | 20 | 14092 | - | - | 31.24
+/- 2.07ns |
| e+ | 110 | 14186 | 286.87k | 36.46k | 88.53ns |
| e+ | 80 | 14185 | 211.63k | 27.37k | 91.15ns |
| e+ | 60 | 14183 | 160.29k | 21.46k | 91.36ns |
A copy of this log entry has been emailed to: dwang,deng,rom,pkpan,rsubedi,doug,dalton