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Re: Charge range on tracking chambers



Hall D Electronics:

We are now trying come up with a number, but I would guess that 250 is a better
factor for the CDC if we consider the path-length variations over angles.

   Curtis
On Tue March 18 2008, Elke-Caroline Aschenauer wrote:
> Hall D Electronics:
> 
> On Mon, 17 Mar 2008, Fernando J. Barbosa wrote:
> 
> Dear Fernando,
> 
> the CDC I think needs more a dynamic range of 100. if you look to the dE
> under 20^o and under 90^o comparing pion DE and proton dE you get without
> modelling any fluctuation a factor of 30, If you take fluctuations into
> account you come closer to a factor 100.
> 
> So I think that is what we should be able to cover a factor 100 in dynamic
> range.
> 
> Eugene I have a question for you, how big of a problem is a non-linearity
> in the cdc detector response for the dE/dx performance.
> 
> cheers elke
> 
> 
> > Date: Mon, 17 Mar 2008 22:02:12 -0400
> > From: Fernando J. Barbosa <barbosa@jlab.org>
> > To: Elke-Caroline Aschenauer <elke@jlab.org>
> > Cc: Daniel S. Carman <carman@jlab.org>, Simon Taylor <staylor@jlab.org>,
> >      Curtis Meyer <cmeyer@ernest.phys.cmu.edu>,
> >      Yves Van Haarlem <yvhaarle@ernest.phys.cmu.edu>,
> >      "halld-electronics@jlab.org" <halld-electronics@jlab.org>,
> >      halld-tracking-hw@jlab.org
> > Subject: Charge range on tracking chambers
> >
> > Hi Elke,
> >
> > Document 747 on the portal shows the charge deposited on the CDC and FDC
> > detectors. These numbers were first estimated for the Electronics Review
> > in July 2003 and were based on geometrical constructs only. You can find
> > a brief summary on slide 22 (a back-up slide) of my presentation for the
> > Hall D Drift Chamber Review of 6-8 March 2007, document 751. Anyway,
> > these numbers have not changed in years....
> >
> > For the CDC, the dynamic range is shown to be 100 fC - 3 pC - a factor
> > of 30. Because the charge amplifier has a peaking time of about 11 ns,
> > the dynamic range of the preamp would be about 400 fC for point
> > ionization (~13% of total charge). The gain of the preamp would then be
> > ~ 1000 mV (a reasonable maximum amplitude to expect from a preamplifier)
> > divided by 400 fC times a factor to allow for some headroom before
> > saturation, say 80%. The result is 2 mV/fC.
> >
> > Similarly for the FDC, the dynamic range for the anodes was estimated to
> > be 300 fC - 3 pC, a factor of 10. For the preamp, 400 fC for point
> > ionization and 2 mV/fC for gain.
> >
> > For the FDC cathodes, the dynamic range was estimated to be 10 fC - 1
> > pC, a factor of 100. For the preamp, 133 fC for point ionization and 6
> > mV/fC for gain. Note that here, the estimate presumed a 1/3 of the
> > charge of the anode on the cathode (charge sharing on adjacent strips).
> > Later, it was decided that this number needed to be changed to 1/5 based
> > on published data. For the preamp, the point ionization was then
> > estimated to be 80 fC and 10 mV/fC for gain.
> >
> > According to these estimates, the CDC and the FDC anodes require the
> > same gain (2 mV/fC) and the FDC cathodes require x5 gain or 10 mV/fC.
> >
> > Obviously, this numbers must be updated to reflect the physics events in
> > the detectors. I hope this helps.
> >
> > Regards,
> > Fernando
> >
> 
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-- 
Professor Curtis A. Meyer        Department of Physics
Phone:  (412) 268-2745          Carnegie Mellon University
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