[Halla12_software] SoLID Baffles

[Eugene Chudakov]

Hi,

the slits were defined using the following procedure:

a) I ran GEANT simulating production in a long target,
    at the edges of a phi-theta sector. The sector
    width was 5 deg at thet_min and 9 deg at thet_max.
    At the low phi edge (against the rotation in the field),
    I took the max XBj and calculated the momentum for the given
    theta. At the higher edge I took the min XBj.

b) GEANT generated hits of these tracks in the planes of the baffles.
    The target length in Z makes things a bit complex, but it turned
    out that simple rules could be used to select the most inner
    points for the given R.
    I took the hits and extrapolated the phi-R curves with parabolas
    as phi=p0+p1*r+p2*r**2.
    The results were stored in the PAW session.

c) Using the stored parameters of the baffles, I printed
    the input to GEANT, splitting the holes in the baffles into
    about 20 rings.

It was not possible to define a slit as a single shape in GEANT3.
I do not know about GEANT4. It would be a complex slice of a paraboloid,
overlapping with other volumes.
Multiple volumes work well in GEANT. One slit was defined,
then copied to all 30 sectors of the given ring. This part of the FFREAD input
code defining the geometry was generated by a script (too many lines to type
by hand).

Eugene



On Thu, 20 Jan 2011, Zhiwen Zhao wrote:

> Hi, Paul and Eugene
>
> I see the baffle is made of small blocks.
> but aren't they generated from some analytic functions?
> If that's true, can I use the function to describe a single slit instead of 
> some rectangle blocks to simply the geometry definition?
>
> Another related question is how the slits on the baffle will be made. Are 
> they gonna be cut out from a whole plate or built with small blocks?
> This will help us decide how to describe it in simulation to match better 
> with the engineering process.
>
> Thanks
>
> Zhiwen
>
>
> On 01/19/2011 02:31 PM, Paul E. Reimer wrote:
>> Hello,
>> 
>> Attached are two files.  One is a PAW kumac.  In it you will see a large
>> array of points which I received from Eugene (the points, not the
>> kumac).  These are used to define small rectangles that are added
>> together to form the baffle.  The output of the kumac is also attached
>> so that you can visualize what it looks like.
>> 
>> Paul
>> 
>> 
>> 
>> 
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>