[Halld-physics] draft text of the eta-Primakoff proposal update

[Matthew Shepherd]

Hi Ashot,

It seems that the total count rates you cite 1-3 kHz are orders of magnitude away from what we are used to thinking about.

Take a look at the first plot on this page:

http://www.jlab.org/Hall-D/software/wiki/index.php/FCAL_Backgrounds

It is a bit dated, but should still be approximately correct.  There you can see count rates *per block* in the region next to the beam hole of 3 MHz.  It is significantly higher inside the beam hole and will probably be higher yet behind the calorimeter where you will get beam interactions with the walls of the hole in the FCAL.

One very important note in this:  we are counting energy deposition all the way down to 2 MeV.  This is relevant for radiation damage, but not for tagging high energy particles like you would like.  We need to check the rates at high energy.

My naive estimate based on these numbers would be a total count rate in the CompCal of a couple hundred megahertz.

-Matt

On Nov 29, 2010, at 7:00 PM, Ashot Gasparian wrote:

> 
>  Hi Matt,
> 
>  Thanks for raising good questions. Let me try to come up with
> my thoughts on your questions:
> 
> 1) the suggested CompCal detector is actually a very small copy
>    of existing HyCal. It will have 16x16 PbWO4 crystal detectos
>    (with a size: 32x32 cm^2) and central 2x2 crystals removed
>    (that makes a 4x4 cm^2 hole in the center, like the HyCal is)
> 2) the expected count rates: we had some MC results done in last
>    year for the CompCal detector also. My recollection is that we
>    did not finish it on the level to estimate the count rate. It is
>    in plan for the December, but we have a direct experimental data
>    from the two PromEx-I and PrimEx-II experiment. There we had a
>    similar detector with the similar beam hole and in intencive
>    photon beam: Ie=110 nA, on 10^4 r.l. radiator, no collimator on
>    beam, gives ~ 7x10^7 eq. photons/sec., 5 to 10 r.l. physics targets
>    in beam and the calorimeter located on ~7.5 m down from the targets.
>    Our rates in the proposal are also calculated for a similar beam
>    conditions. The total HyCal rate (for the sum) was from 1 KHZ to
>    3 KHz depending on beam tune. With these rates we had it as the
>    primary trigger in the experiment with a good physics results.
>    The CompCal will be all the same only the outer dimension much
>    smaller. Based on our experimental reasults, I do not expect any rate
>    problem with this design. Though, we will try to finish the MC
>    simulations left from the last year.
>  3) for the document for CompCal: I agree with you we need a draft of
>     technical design report for this detector. I will try to do that in
>     the comming weeks and post it in the GlueX wiki.
> 
>  Hope these are answering to your questions in some ways. Please let
> me know if some of them needs more discussions.
> 
> Thanks,
> Ashot
> 
> 
> .............................................................
> Ashot Gasparian                    Phone:(336)285-2112 (NC A&T)
> Professor of Physics
> Physics Department                       (757)-269-7914 JLab
> NC A&T State University              Fax:(757)-269-6273 JLab
> Greensboro, NC 27411               email: gasparan at jlab.org
> .............................................................
> 
> 
> On Mon, 29 Nov 2010, Matthew Shepherd wrote:
> 
>> 
>> Hi Ashot,
>> 
>> Do you have a document that outlines the details of CompCal
> including simulations of the background?  Has such a technique
> been used for other experiments?  What is the geometry of this
> detector -- does it have a beam hole?  I imagine count rates
> for this detector must be incredibly high.
>> 
>> -Matt
>> 
>> On Nov 29, 2010, at 5:53 AM, Ashot Gasparian wrote:
>> 
>>> 
>>> Dear Hall D Collaborators,
>>> 
>>> We are required to submit a short update for the eta-Primakoff
>>> proposal to this upcoming PAC37 for the beam time assignment and
>>> scientific rating.
>>> The proposal was approved a year ago by PAC35.
>>> 
>>> The first draft of the suggested update is in the attachment of
>>> this email. The submission deadline is on this Wednesday, so you
>>> will have a few days to send your critical suggestions and questions
>>> to us to make this document better for the submission.
>>> 
>>> Thank you for your participation and valuable support,
>>> Ashot, Liping
>>> 
>>> 
>>> 
>>> .............................................................
>>> Ashot Gasparian                    Phone:(336)285-2112 (NC A&T)
>>> Professor of Physics
>>> Physics Department                       (757)-269-7914 JLab
>>> NC A&T State University              Fax:(757)-269-6273 JLab
>>> Greensboro, NC 27411               email: gasparan at jlab.org
>>> .............................................................
>>> <eta_update_PAC37_v3.pdf>_______________________________________________
>>> Halld-physics mailing list
>>> Halld-physics at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/halld-physics
>> 
>>