progress and tasks

From: John Calarco (jrc@einstein.unh.edu)
Date: Sun Jul 14 2002 - 23:37:23 EDT


As can be seen from the shift summary reports, the left sector
TOFs are now timed to each other +/- 1 ns, except for LTOF 11
and 13 (counting from 1 to 16). These continue to present a
problem, scaling on cosmics consistent with the other TOFs but
having an anomolously low rate with beam. The right sector TOFs
are also timed to within +/- 1 ns, except for RTOF 12 which
displays a similar problem as above.

All retiming_OR - start_mean histograms are characterized by
FWHM that are less than or about 1 ns. This is consistent with
what was expected from GEANT simulations using the extended
target and extended start counter. Those simulations showed
that flight path variations introduced widths of 0.5 - 0.7 ns
which must then be folded in with the intrinsic detector
resolutions.

The remaining problems/tasks are:

(1) The right sector TOFs retiming_OR - start_mean is centered
near channel 1420. The corresponding TDC difference for the left
hand sector was centered at around channel 1700. Thus there
appears to be a significant time difference. This is misleading.
In our trouble-shooting efforts during the left sector measurements,
the start counter which was connected into RTOF 16 was purposely
shifted early by about 15 ns. During the recent right sector
measurements, no such shift was made. Thus one should expect
approximately 15 ns = 300 channels difference between the two
sets of data even if the TOFs on both sectors were timed together.
This is close to the observed 280 channels.

What needs to be done is to take the same amount of delay out
of the top and bottom TOF delays for LTOF 16 (the start counter
for the right sector measurements) and determine the new channel
for the average retiming_OR - start_mean for thr right sector.
If this is also now around 1420, then all LTOFs and all RTOFs are
correctly timed. If there is a difference then we know how much to shift
either all LTOFs or all RTOFs to match. The first step is to go back to
the logbook to determine how much delay was taken out of RTOF16
for the left sector measurements (it may have been 14 or 16 ns).
Then perform the measurement (after recording the present LTOF16
delay which has already been so painfully determined). A good
statistics run will determine the new value of retiming_OR - start_mean
for the right sector.

(2) There are the remaining ptoblems with LTOF 11 and 13 and RTOF 12.
These should be investigated without beam using the flasher and
cosmics during the day shift tomorrow (Monday) provided the data
described above have been taken.
 

-- 
John R. Calarco
Dept. of Physics
Univ. of New Hampshire
Durham, NH 03824
phone: (603)862-2088
FAX:   (603)862-2998
email: calarco@unh.edu



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