[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Charge range on tracking chambers



Hi Elke,

I believe the ASIC already covers a dynamic range of 100. I think I measured this on the bench sometime ago but I will be glad to measure it more accurately. However, I think it will be hard to get anything significantly higher than a factor of 100.

Regards,
Fernando





Elke-Caroline Aschenauer wrote:
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                              -
            +=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+

  
begin:vcard
fn:Fernando J. Barbosa
n:Barbosa;Fernando J.
org:Jefferson Lab
adr:Suite #10, 12B3;;12000 Jefferson Ave.;Newport News;VA;23606;USA
tel;work:757-269-7433
version:2.1
end:vcard