[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Charge range on tracking chambers
Hall D Electronics:
Just a very simple physics arguement:
For the same path length, the energy depsoited scales like
1/beta^2, so for a 350 MeV/c pion and proton, the relavent factor
is ~7, for 300 MeV/c it is ~9.
For a particle crossing at 8 degrees (minimum for ~ 10 CDC hits), the
path length relative to 90 degrees goes like 1/sin(theta), or about a factor
of 7.
Assuming that we are total charge limited in the preamp, we are hit with the
entire factor which is 49 to 63 --- say about 60. If we are pulse-height limited,
then the area scales by 63, but the height will go up by a smaller factor.
We then multiply by 4 (pick your favorite factor) to get 240 for the dynamic
range.
On Tue March 18 2008, Curtis A. Meyer wrote:
> 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
> > >
> >
> > ( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=
> > ) `\ -
> > / '. | +
> > | `, Elke-Caroline Aschenauer =
> > \,_ `-/ -
> > ,&&&&&V Jefferson Lab +
> > ,&&&&&&&&: HALL-D 12C / F381 121-A Atlantic Avenue =
> > ,&&&&&&&&&&; Suite 8 Hampton, VA 23664 -
> > | |&&&&&&&;\ 12000 Jefferson Ave +
> > | | :_) _ Newport News, VA 23606 Tel.: 001-757-224-1216 =
> > | | ;--' | Mail: elke@jlab.org Mobil: 001-757-256-5224 -
> > '--' `-.--. | +
> > \_ | |---' Tel.: 001-757-269-5352 =
> > `-._\__/ Fax.: 001-757-269-6331 -
> > +=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+
> >
>
>
>
--
Professor Curtis A. Meyer Department of Physics
Phone: (412) 268-2745 Carnegie Mellon University
Fax: (412) 681-0648 Pittsburgh PA 15213-3890
cmeyer@ernest.phys.cmu.edu http://www.curtismeyer.com/