Hello,
after tedious search I believe that there could be two problems that may
explain the L/R timing difference.
The new fact is that there is a 16 ns shift between the prompt out at the
patch for analogue signals and the input to the ECL fan-out to the TDC's.
I also realized that although the retiming (i.e. what we plot) is by
definition independent of when/how the TDC common start arrived, there is
one subtlelty. The start counter signal has been fed to two different
sectors, and hence any difference in the L/R cabling for TDC channel 16
(either 16top or 16bottom or both) would have resulted in a shifted
TDC spectrum.
_ I suspect the 16 ns offset is due to the calibration of the delay unit
right after the CFD. It is *assumed* to be 2 ns/tab, but the same unit
(will look just the same) may have 4 ns/tab or the equivalent unit on
the right sector be a 1 ns unit. They will look EXACTLY the same since the
tab size is fixed by LeCroy (but the model name/number does not change)
In either case - for our settings - this would explain why L16top is 16 ns
later than R16 top, for signal coming at the same time.
There are many ways to check this calibration, we are trying to confirm
this suspicion using the (known) TDC calibration in the fastbus crate
_ The second caveat is the following. The analysis routine just takes the
retiming or value. However, also the start counter goes through the 32
channel retiming OR. Therefore, if the start counter passes the OR
typically earlier than any tof-scintillitor, you will be plotting
retimed_start-counter - start-counter
We are also going ot check this tonight (by delay the start counter
enough such that it comes in last at the retime or. For the trigger
common start this should not matter since we only need a (any) trigger
start.
*******
Today I measured temperatures at the D-tunnel crates to be
45-55 C @ NIM/CAMAC electronics
40-45 C @ fastbus electronics
this was reported at the daily meeting. Prompt action!!
*********************
regards,
tancredi
________________________________________________________________________________
Tancredi Botto, phone: +1-617-253-9204 fax: +1-617-253-9599
research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
On Tue, 23 Jul 2002, Peter Karpius wrote:
>
> For the 7-23-02 Shift Summary please see the electronic logbook
>
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