Re: references on the precision TOF

[Alex Dzierba <dzierba@indiana.edu>]

Hi Andrei

Thanks for this information - very valuable indeed.

Alex

At 8:39 PM -0400 7/31/07, Andrei Semenov wrote:
>Elke:
>
>You can find the PDF file with the paper you asked for on the meeting
>(viz., CERN NA49 detector description) on the web address
>http://www.jlab.org/~semenov/na49-detector.pdf (it's too big for the
>attachment); and the reference is NIM A430 (1999) 210.
>TOFR wall (of about 2 m^2 area and 900 PMTs) was made
>by Marburg U. group, and used Philips XP-2972 tubes; the overall TOF
>resolution (viz., including start counter contribution as well as
>electronics resolution and the 900-channels calibration misallignment) was
>about 60 ps (sigma). TOFL wall (same area, same # of PMTs) was made by
>Dubna group (myself included); it used Russian FEU-87 PMTs, and the
>overall time resolution was about 75 ps (sigma). Surely, these detectors
>are the "pixel" ones, but my point is that absolutely no special
>"stabilization" of PMTs was necessary to reach such a resolution. Critical
>decision (to reach such a resolution) was to remove the light guides and
>couple PMTs directly to the scintillators. Another important moment was to
>use the hit position from the TPC. And (of course) the quality of the
>cables from PMTs to CFDs...
>
>You might be interested to have a look on the TOF paper from BESII/BESIII
>experiment: http://www.jlab.org/~semenov/besII-tof.pdf or
>NIM A555 (2005) 142. The guys used 230x5x6 cm^3 bars, and got about
>90 ps resolution per bar. Again, it was more thick bar, and they used
>fine-mesh Hamamatsu R5924 PMTs, but light dispersion should be about the
>same => it's not an absolute limit that does not allow to reach a good
>time resolution, and the optimization is possible.
>
>Thanks,
>Andrei
>
>
>
>On Mon, 30 Jul 2007, beni zihlmann wrote:
>
>>
>>  I probably did not express myself properly. The 150ps I quoted as TOF
>>  resolution
>>  is for one plane.
>>  So one can assume that for two planes (horizontal+vertical) the timing
>>  resolution
>>  from the full device could reach 150ps/sqrt(2)=106ps. So there is
>>  justified hope
>>  that for the full device we can reach 100ps or even below. The only
>>  caveat is that
>>  while the efficiency will be high it will be not 100%, in particular
>>  because we
>>  do not stager the paddles but they are on top of each other or side by side.
>>
>>  cheers,
>>  Beni
>>


-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alex R. Dzierba
Chancellor's Professor of Physics (Emeritus)
Department of Physics / Indiana U / Bloomington IN 47405 / 812-855-9421
JLab Visiting Fellow
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