Re: TOFr TDC range

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From: W.J. Llope (llope_at_physics.rice.edu)
Date: Tue Apr 15 2003 - 10:07:30 EDT

At 10:58 PM -0400 4/14/03, Xu, Zhangbu wrote:
>Hi, Bill and others:
> The TDC is 11 bits which means the range is upto 2000.

correct.

>Our TDC
>value now is very low.

could you be more quantitative? i've been looking at the localmon
data - there's only a few counts scattered around on the stop sides.
perhaps you are looking at the DAQ files directly (which
has 10x the data)?
but the counts i do see are in the same spot as they've been
all run...

in both run-2 and run-3, the TDC peaks (for all detectors)
are near channel 500.
the range of interest (in terms of where the hadrons
are in our mass and momentum range and including all
the smearing from ADC, Zhit, Zvtx, etc etc) spans from
~ch 200 to ~700.

in E896 we used fastbus TDCs, and for those one tries to stay
in the middle ~20%-80% of the dynamic range to avoid
their ferocious nonlinearities....

but (because we knew better) we are not using fastbus tdcs in STAR...
the camac 2228A's are not nearly this bad. the most
one ever might want to avoid is the first ~50-100 chs
which is <5% of the dynamic range.

and well below (well earlier) than where our signals of interest
are coming in.

i think we're fine here... unless you're saying
the TDC peaks have shifted in between the dAu and pp runs... (?)
- bill

>Is there a reason that we should not change
>the delay so that the TDC peaks at around 1000?
>Will there be any nonlinearity if the TDC value is too low?
>
>Thanks!
> Zhangbu
>
>
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-- 

  W.J. Llope, Ph.D.                      Res. Assoc. Professor
  T.W. Bonner Nuclear Laboratory         phone:  713-348-4741
  Rice University, MS-315                fax:    713-348-5215
  6100 S. Main St.                  
  Houston, TX 77005-1892            
             e-mail:     llope_at_physics.rice.edu
             WWW home:   http://wjllope.rice.edu/default.html

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