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Re: FCAL test
On Thu, 13 Sep 2007, Elton Smith wrote:
Dear Beni,
in addition to Eltons points. I would actually measure the response to
different incident angles and I would also put a radiator in front of the
test FCAL which simulates all the material corresponding to the tof in
front of it.
Actually could you present something in one of the next hall D meetings.
thanks elke
> Date: Thu, 13 Sep 2007 12:10:54 -0400 (EDT)
> From: Elton Smith <elton@jlab.org>
> To: beni zihlmann <bzihlman@indiana.edu>
> Cc: Richard Jones <richard.t.jones@uconn.edu>,
> Matthew Shepherd <mashephe@indiana.edu>,
> Alex Dzierba <dzierba@indiana.edu>,
> Elke-Caroline Aschenauer <elke@jlab.org>, Elliott Wolin <wolin@jlab.org>,
> George Lolos <George.Lolos@uregina.ca>,
> Zisis Papandreou <zisis@uregina.ca>, Elton Smith <elton@jlab.org>,
> David Lawrence <davidl@jlab.org>
> Subject: Re: FCAL test
>
>
> Hi Beni,
>
> My recollection was that the main studies of the test were to check
> * light collection with new light guides
> * understand the fadc readout as well as the summing boards for the
> trigger.
>
> There are probably others, but here some thoughts off the top of my head:
>
> For the acceptance of the detector we have re-learned from looking at the
> bcal that the energy threshold is clearly very important, and we should
> make sure that we have a clear plan for the fcal as well. At the moment
> our nominal threshold is 100 MeV but it would probably be good to
> understand this experimentally. For example, what is the resolution near
> threshold? And what is the impact of the thresholds on physics?
>
> At the upper end of the spectrum, other terms become dominant in the
> resolution, e.g. the constant term. It is not clear to me how much we
> can learn about this contribution from a prototype. The constant term
> comes from leakage and systematics. Leakeage is determined by the geometry
> (different between a small prototype and the full detector) and
> systematics, which depends on electronics (likely different between
> prototype and full detector) and environment.
>
> One issue that I would like to make sure we understand is the dynamic
> range that is required and is achievable in practice, especially given the
> fADC are 10 bits. I know that there has been discussion of modeling
> saturated pulses to effectively increase the dynamic range, but this needs
> to be studied very carefully. I personnally have always been biased
> against relying on extracting reliable data which saturates the
> electronics. To study the dynamic range, the broader the range of energy
> measured the better. But in any case, measurements at these energies would
> require extrapolation to the upgrade energies, and we need to make sure
> that we have a scheme to do this. Any discussion on this topic should
> involve our electronics group and may be a good topic for discussion at
> the electronics meeting prior to the collaboration meeting.
>
> In addition to looking at the response for photons, we had also talked
> about measuring the response to electrons. These could be selected for
> energy by placing the prototype under the tagging magnet and looking at
> the scattered electron. This would give almost monochromatic electron
> beams (different energies by moving the detector). The impact position
> would have to be measured independently. It is unlikely that the primary
> electron beam could be used for tests due to the rate.
>
> Cheers, Elton.
>
> Elton Smith
> Jefferson Lab MS 12H5
> 12000 Jefferson Ave
> Suite # 16
> Newport News, VA 23606
> elton@jlab.org
> (757) 269-7625
>
> On Wed, 12 Sep 2007, beni zihlmann wrote:
>
> > Dear Colleagues,
> > I am soliciting advice and ideas about a future test of the FCAL.
> > We are in the process of setting up a plan for testing an 8x8 array of
> > the FCAL calorimeter blocks. One of the main questions is what
> > photon energies do we need for such a test. In GlueX the FCAL
> > will see the whole spectrum of particles from the lowest energy
> > up to beam energy. Do we need to test the full range or is it enough
> > to test the low energy side similar as was done for the BCAL and
> > ensure that we have enough dynamic range up to 9GeV? Or do you
> > think we also need to measure at high energies and show that
> > the calorimeter is linear?
> >
> > I am looking forward for your advice,
> > Beni
> >
> > --
> >
> > B. Zihlmann
> > Indiana University
> > Physics Department
> > 727 E. Third Street
> > Bloomington, IN 47405
> > phone: (812) 855 6973
> > Fax: (812) 855-5533
> >
> >
>
>
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