Re: updated geometry

[Elton Smith <elton@jlab.org>]

HI Beni and Richard,

I am entering this discussion mid-way, but the Al plate was to replace the
first lead sheet and it has a similar number of radiation lengths. So the
effect on low-energy photons should not be too different than the original
design.

Cheers, Elton.




Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton@jlab.org
(757) 269-7625
(757) 269-6331 fax

On Mon, 14 Jul 2008, Richard Jones wrote:

> Beni,
>
> Yes we should have as much of reality as is relevant for performance,
> and certainly this plate will affect the performance.  But it simply
> cannot be there if we want to measure low-energy photons.  Perhaps we
> can let the MC studies show that, but I don't think we need MC to know
> what the result will be.  I would say that our concern about the FDC
> cables pales in comparison with this.
>
> Richard Jones
>
> Beni Zihlmann wrote:
> > Hi Richard and All,
> > indeed I forgot to adjust the overall module volume to accommodate for
> > the inside aluminum plate. I can/will fixt that in a second.  But now
> > I have a question to your comment. I agree that an 8mm aluminum plate
> > inside the BCAL surface will degrade the resolution but that is
> > exactly what is in the drawings to build the BCAL and Elke asked me to
> > put it into the geometry. Don't we want to have the studies to be made
> > by Matt et al. having a geometry as close as possible to reality?
> >
> > cheers,
> > Beni
> >
> > Btw. yes I am really interested in your tools.
> >
> >
> > Richard Jones wrote:
> >> Beni, some work is still needed on this geometry.  The following
> >> items are invalid, so that no particle will ever be able to enter
> >> their volumes.  This is not a comprehensive list, just the result of
> >> a quick spot check I did.  I have a tool that can enables a quick
> >> point-and-click check on individual volumes.  I can show you how to
> >> use it, if you are interested.
> >>
> >>    1. FDC cables re-routed to run upstream
> >>    2. 8mm aluminum plate in front of BCAL
> >>
> >> That aluminum 8mm plate will completely wipe out the BCal resolution,
> >> once it is in there!  For the moment, however, it causes no problems
> >> at all, because particles do not see it. :-)
> >>
> >> -Richard Jones
> >>
> >>
> >> Beni Zihlmann wrote:
> >>> Dear colleagues,
> >>> I updated the geometry in the repository. The geometry now reflects
> >>> all the changes and design decisions that have been made lately.
> >>> 1) remove outer most CDC layer thereby reducing the CDC radius by
> >>> 1.6 cm
> >>>    including the cable runs.
> >>> 2) re-route the FDC cables to run upstream
> >>> 3) add an 8mm aluminum plate on the inside of the BCAL
> >>> 4) the BCAL readout segmentation is 4x6 (sector x layer)
> >>>
> >>> all these changes are now available the in geometry file
> >>> hddsGeant3.F located in
> >>> src/programs/Simulation/HDGeant/
> >>>
> >>> cheers,
> >>> Beni
> >>>
> >>
> >
> >
>
>