Re: updated geometry

[Beni Zihlmann <zihlmann@jlab.org>]

Hi Elton,
ok but then I think what I did is wrong. I just added the Aluminum plate 
to the existing
BCAL geometry. That means the total thickness increased by 8mm.
 From your comment I take it that the calorimeter should go in radius 
from 65cm to 90cm
this corresponds to a total thickness of 25cm with the first 8mm  
Aluminum and the last 2.54cm  Aluminum.
Do I understand this correct?

cheeres,
Beni
> 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
>>>>>
>>>>>           
>>>       
>>     
>
>   


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Benedikt Zihlmann
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