User name R. Michaels
Log entry time 10:11:08 on November 7,2001
Entry number 76238
This entry is a followup to: 76030
Followups:
keyword=oddities of TC (coinc time)This is a follow-up to halogs 76030 and 76127 regarding coincidence time (TC).
Figure 1 which shows the TC measured on R-arm TDC and on L-arm TDC.
I will prepare a memo to explain this better. Short version:
1. There is a normal region where the TC's on 2 arms are anti-correlated.
Starts come from a local scintillator retiming signal, stop from other arm's trigger.
2. Region A seems where the L-arm has no retiming signal. One gets a
forced retiming which follows the timing of the accepted trigger (L1A).
3. Region C and the smear below it is due to pileup of the retiming signal.
There is a window in which this signal can arrive. If it is a bit early you get the
smeared region, and if earlier than L1A by <= 100 nsec you get forced retimings.
4. The region to the right of "normal" is the same as item 3 for L-arm.
5. Region D is, I think, due to random overlaps at the trigger supervisor in
a 10 nsec window, which are programmed to be "event 5" but are random T5.
Rate here should be T1*T3*10 nsec / (ps1 * ps3)
6. There is a box all around bordered by ~50 nsec and 409.6 nsec.
These are underflows and overflows.
7. Probably the simplest way to correct for these things is to throw out all but
the normal region and apply corrections (few %) to cross section where relevant.
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Figure 2 shows the TC on R-arm for run 1468 as mentioned in halog 76127
I also see glitches in places, don't know why. But it appears we are plotting
different data (?)
======== TDC channels for TC =========
TDC model 1875 with 100 psec resolution, common start, single hit
Spectrometer........Crate.....Slot......Channel
R-arm...............roc 1......21........5 th
L-arm...............roc 2......3.........49 th
FIGURE 1
FIGURE 2
