[Halld-pid] Fwd: TOF 6-fold ambiguity constant, shadow band

[Mark Ito]

from Kei Moriya:


-------- Forwarded Message --------
Subject: 	TOF 6-fold ambiguity constant, shadow band
Date: 	Wed, 06 May 2015 22:55:41 -0400
From: 	Kei Moriya <kmoriya at jlab.org>
To: 	Mark Ito <marki at jlab.org>, halld-pid at jlab.org



Dear TOFers,

I was checking the so-called 6-fold ambiguity for the TOF CAEN
TDCs in the spring run. During cosmic testing before beam, I
had thought the firmware upgrade had fixed this constant to 1
so that we would never have to calibrate this again on a
run-by-run basis. It turned out that the constant we put in the
CCDB for runs 2900 onward was incorrectly set to 0, where it
should have been 1. This has been fixed.

However, I am seeing a new problem. If I look at the
(event time modulo 6) vs the timing difference of the ADC
and TDC, I see a shadow band that appears only for data taken
with mode 7. The difference of the bands is approximately 200 ns.

I have uploaded a file to the DocDB
http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=2702
showing the plots for many runs of spring 2015.
Comparing to the info in
https://halldweb.jlab.org/cgi-bin/data_monitoring/run_conditions.pl
you can see that the shadow band appears only for runs
taken in mode 7.

	Kei



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