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User name Kalyan/Xin
Log entry time 08:20:26 on November 11, 2008
Entry number 248100
Followups:
keyword=Trying to understand coincidence timing spectraXin, Brad and I made an attempt to understand the coincidence timing spectra that we were seeing in the data given by T5 timing in the TDC. The issue was that we were not seeing full window of 140ns in the T5 TDC spectrum(fig 1) and also an extra peak in the middle of T3 spectrum(see fig3).
Fig 1: Looking at the T5 timing when the stop is given by T5 itself, we should see a sharp self-timing peak. Instead we see some spread on the left side of the sharp spike. This spread can be due to the events for which T3 is coming earlier than T5 at the trigger supervisor(TS).
Note: At the TS, T5 comes first then T3 in about 3ns and the T2 at 5ns w.r.t T5.
Fig 2. Plot of T3 timing when the stop in given by ONLY T5 and NOT T3. We should look at this is spectrum to look at the full coincidence window.
Fig3. Plot of T3 time when the stop is given by ONLY T5. The left side spike is pile up (due to T3 determining the T5 timing and not T1) and the spike in the center is due to the self-timing of T3. And the usual coincidences show up at the edge.
Fig4. Plot of T3 timing when the stop is given by the T3 only. Spike on right should ideally be flat and should spread to the edge of the window(up to about 460ns see fig 3) but instead it pile because T3 comes before the T5 at the TS.
So, in conclusion we should look at fig 2 to look at the full window of the coincidence and the spike in the center of T3 is basically coming from the self-timing of T3.
If any one is interested more discussion can be had in the back room...
A copy of this log entry has been emailed to: brads,xqian,jiang,rom,moffit,vasulk,jinhuang
Figure 1
Figure 2
Figure 3
Figure 4
