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Re: your note on timing





Gerard,

I very much agree with your comments on the FADC timing.  As you
know our current setup with the Hall B SIP preamplifiers and
our postamplifiers, lead to a timing resolution (compared with the
TDC) of about 4 ns for the 100 MHz FADC (and the same number
comes out for the 200 MHz FADC).  Simon is away for the holiday
at this time, but I think a visit in January is important to
coordinate to address some of the mysteries that we have found
on the timing.  We should communicate again at the start of the
new year on this matter.

Also note that the primary issue here in considering FADCs on the
anodes is for dE/dX measurements.  If these are not necessary for
the FDCs, then I would favor performing timing measurements with
TDCs.  If dE/dX is deemed necessary for the FDCs, remember that
we are reading out the cathodes with FADCs which, in principle,
should have the same information as the anodes for dE/dX purposes.
The reasons why other folks have not been successful in getting
dE/dX measurements from cathodes is still an open question.

				Regards,

					Daniel


**********************************************************************
*                                                                    *
* Dr. Daniel S. Carman                   e-mail : carman@jlab.org    *  
* Staff Scientist                        office : (757)-269-5586     *
* Jefferson Laboratory                   web: www.jlab.org/~carman   *  
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