Re: Charge range on tracking chambers

[Elke-Caroline Aschenauer <elke@jlab.org>]

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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