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Re: updated geometry
Hi Elton,
I agree we should get the inner dimension of the BCAL correct, but
maybe this change is minor and we should incorporate it into the next
round of geometry revisions. One may want to segment the BCAL
differently so that the inner 8 mm layer of this composite mixture is
not active. We have calibration constants now for both the 6x4 and
3x3 geometries and we are working through various photon and pi^0
resolution and efficiency studies.
-Matt
On Jul 15, 2008, at 9:06 AM, Elton Smith wrote:
>
> HI Beni,
>
> Generally it might be good to have the inner dimension correct for the
> Bcal. The material in the Bcal is already a composite of Pb/Sci/
> Glue, and
> the addition of the Al plate should not change this effective
> composite
> very much, one might want to change the dimension of the Bcal but
> leave it
> all as Bcal material.
>
> Comments?
>
> 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 Tue, 15 Jul 2008, Beni Zihlmann wrote:
>
>> Hi All,
>> talking to Elton I think this issue with the Aluminum plate is more
>> tricky.
>> Here is the deal.
>> The 8mm Aluminum are supposed to replace the first 0.5mm lead of the
>> lead/scintillator
>> matrix. So after the last scintillator layer this aluminum plate is
>> glued on instead of a lead
>> layer with the aluminum being so thick that it is equivalent to the
>> last
>> layer of lead. That is
>> where the 8mm thickness is coming from.
>> This means I have a problem modeling this in the geometry file
>> because
>> the active volume
>> of the calorimeter is already defined as a mixture of
>> lead/glue/scintillator. So I can not simply
>> replace the innermost 0.5mm lead by 8mm aluminum.
>>
>> My conclusion of this problem is that we should leave it as it is
>> without aluminum plate
>> for the simulation because this is the closest to reality in terms of
>> radiation length and that
>> is probably more important/critical than the additional volume size.
>>
>> What is your opinion?
>>
>> cheers,
>> Beni
>>
>>> 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
>>>>>>>>
>>>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>
>>>
>>
>>
>> --
>> ***********************************************************
>> Benedikt Zihlmann
>> TJNAF
>> HallD 12C/ F350
>> Suite 8
>> 12000 Jefferson Av.
>> Newport News VA, 23606
>>
>> tel: 757 269 5310
>> fax: 757 269 6331 zihlmann@jlab.org
>> ***********************************************************
>>
>>
>>
>