Re: Tagger Fixed Array & Pair Spectrometer Electronics Update (fwd)

[Elton Smith <elton@jlab.org>]

---------- Forwarded message ----------
Date: Thu, 28 Feb 2008 11:59:07 -0500 (EST)
From: Franz Klein <fklein@jlab.org>
To: Fernando J. Barbosa <barbosa@jlab.org>
Cc: Daniel Sober <sober@cua.edu>, Elke-Caroline Aschenauer <elke@jlab.org>,
     "halld-electronics@jlab.org" <halld-electronics@jlab.org>,
     Richard Jones <richard.t.jones@uconn.edu>
Subject: Re: Tagger Fixed Array & Pair Spectrometer Electronics Update


Fernando,

I apologize to have left your mail without response for such a long time.

See below my answers to your questions (I will add paragraphs on
electronics requirements to the Gluex wiki:
http://www.jlab.org/Hall-D/software/wiki/index.php/Photon_Beam_Design_Requirements

Franz

On Thu, 28 Feb 2008, Fernando J. Barbosa wrote:

> Hi Franz,
>
> I have requested this information before but I have received no updates,
> yet.
>
> I am updating the information on the electronics system diagram for all
> Hall D detectors. I would appreciate if you could provide some feedback.
>
> Tagger Fixed Array:
> 1. Are passive splitters appropriate for the fixed spectrometer (PMTs)?
> Passive (resistive) splitters will cut the amplitude of the signal in
> half (TDC and ADC) but the S/N is maintained.

We use passive splitters for the fixed spectrometer: the signals are large
enough.

> 2. Are leading edge  discriminators appropriate for the fixed spectrometer?

We want to keep it with CFDs in order to be able to adjust gains for high
luminosity runs without loosing the timing accuracy.

> 3. Is 60 ps resolution (LSB) sufficient?

That resolution is enough: we have to test some prototypes first but my
guess is a timing resolution of 100-150psec.

> 4. Recently, the fADC250 requirements have been changed to 12-bit. Is
> this appropriate?

That is fine with us!

> Pair Spectrometer:
> 1. Is the PMT used the XP2020?

Currently we use the Hall-B spectrometer as placeholder for our design
that is being developed in cooperation with Yerevan Physics Inst.
Hall B has Hamamatsu R6427 and XP2020 might be fine as well. I don't know
about the scintillator widths for Hall D yet.

> 2. Is 60 ps resolution (LSB) sufficient?

Yes: here the timing is less important than for the tagger hodoscope.

> Thanks for your attention.
>
> Regards,
> Fernando
>

===============================================================
                  Franz J. Klein, Associate Professor
                  CUA, Department of Physics
                  Washington, DC 20064
  office: Hannan Hall 206          phone: 202-319-6190
  or: Jefferson Lab,CC F-243       phone: 757-269-6671
---------------------------------------------------------------
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