[Frost] Time Walk Calibration Issues (May need a new laser run)

[Arthur Sabintsev]

Hi,

While doing the veff and time_walk (tw) calibration, I came upon a peculiar
error. Using the same cooked BOS files (from test runs 62317, 62808, 62847),
I was able to produce histograms for the veff calibration, but for the tw
calibration, the histograms were empty. Since the Time-Walk calibration
tutorial isn't the greatest (on the Hall-B Wiki), I opted to contact Craig
Bookwalter (TOF Calibration expert for g12), and he told me that we may need
a new laser run. I'm forwarding an excerpt of the message he sent me:

-----BEGIN EXCERPT-----
The only file I see in what I believe is the g9b /mss directory is this one:

/mss/clas/g9frost/data/tof_laser_062156.A00

Looking at this file with "bosdump" I see that there's basically nothing in
it except the TESC bank. I compared that to what's inside of:

/mss/clas/g9frost/data/tof_laser_055433.A01

which is one of the files I used for the g12 TW corrections. This file has
the banks needed by make_tw_histos (RFT, SC, etc). Compare the first ten
events for yourself here:

/work/clas/clasg12/craigb/tmp/g9a_laser_55433_bosdump.txt
/work/clas/clasg12/craigb/tmp/g9b_laser_62156_bosdump.txt

This is not your fault. What you need to tell everyone at the meeting is
that the single lonely laser data file you have for g9b is messed up and the
TOF expert needs to take another laser run--a good one this time. There's
only one good laser run in g9a and it has ten files--expect the same for a
good g9b laser run. Even with a good laser run though, don't expect much.
The TOF laser system is totally fucked. At least 60% of your channels will
have no laser data whatsoever, and probably 75% with too little laser data
to be useful. The question of what to do with these channels is an open one.
 For a first-order calibration, you can grab the constants from
calib_user.RunIndexg12 and put those into the g9b index.
-----END EXCERPT-----

I will mention this at tomorrow's meeting as well (if we have one). I
figured I should give everyone a heads up.

Arthur A. Sabintsev
Ph.D. Student, Graduate Research Assistant
Department of Physics, The George Washington University
isosp.in <http://www.isosp.in>
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