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[Fwd: Re: Collimator layout]



Sorry for the error. The links are..

http://www.jlab.org/~whitey/Collimator-Elevation-rev1.pdf
http://www.jlab.org/~whitey/Collimator-Top1-rev1-Model-1.pdf


-------- Original Message --------
Subject: Re: Collimator layout
Date: Tue, 27 May 2008 16:59:53 -0400
From: Tim Whitlatch <whitey@jlab.org>
To: Richard Jones <richard.t.jones@uconn.edu>
CC: Hall D beam working group <halld-tagger@jlab.org>, Vladislav Razmyslovich <vgr@jlab.org>
References: <4832F961.7060801@jlab.org> 48341C95.4090207@uconn.edu"><48341C95.4090207@uconn.edu> Pine.LNX.4.58.0805211015260.350@elton01.jlab.org"><Pine.LNX.4.58.0805211015260.350@elton01.jlab.org> Pine.LNX.4.58.0805211017380.21052@jlabl1.jlab.org"><Pine.LNX.4.58.0805211017380.21052@jlabl1.jlab.org> 48344E19.4030305@jlab.org"><48344E19.4030305@jlab.org> 48346B89.6010607@jlab.org"><48346B89.6010607@jlab.org> 483546F0.9070502@uconn.edu"><483546F0.9070502@uconn.edu>


Ok Richard, I believe we have incorporated your comments. The linked 
revisions can be used as a baseline if it is correct. You mentioned 
three mylar windows. Are you including the target window in the three? 
We can then start looking at locating the pair spectrometer. Can the 
secondary collimator be moved upstream at all?

http://www.jlab.org/~whitey/Collimator-Elevation-rev1.pdf/
http://www.jlab.org/~whitey/Collimator-Top1-rev1-Model-1.pdf

Cheers,

    Tim

Richard Jones wrote:
> Tim, see my answers below.
> -Richard J.
>
> Tim Whitlatch wrote:
>> Hi Richard,
>>
>> After going through these items with Slava and Chuck, we have the 
>> following comments/questions;
>>
>> 1. Yes, the 10 inch tube extends 12" into the cave. Since the vacuum 
>> picks up just downstream of the 2nd collimator, what type of thin 
>> window is required is required at both locations?
> In the simulation, I have 500 microns of mylar for all three windows.
>> 2. On the 3D model from Igor, the primary collimator has (3) 5cm 
>> tungsten sections (15cm total). Should there be 6 of these?
> Yes, those should be doubled.  That seems to have been an error.
>> 3. We will show 2cm pole gap for now
> Good.  Our simulation currently has a 2cm x 2cm (5cm x 5cm for sweep 
> 2) square hole through the sweep magnet gap for the beam to pass, and 
> the rest of the gap is filled with lead.  We might want to ask Sascha 
> how effective that intra-gap lead is at reducing backgrounds, once he 
> has optimized the sweep magnet field value.
>> 4/5. We can put a 2cm square hole. Can it be round?
> Yes, they can be round.  If we make that block by stacking rectangular 
> sheets of iron then it might be easier to make it square.  At least 
> this was the thinking behind the square hole.
>> 6. Again, the secondary collimator shows (5) 5cm nickel sections (25 
>> cm total). Should there be 10?
> Yes.
>> 7. The inner dimensions of the cave are 452 cm wide by 269.24 cm 
>> high.This can vary as much as 3 cm. Currently there are no provisions 
>> for a notch in the concrete on the civil drawings. This would require 
>> a modification to the design. We will have to detail out that design 
>> and submit to facilities.
> The problem was that we were seeing a significant peak in the 
> background at the GlueX detector out at larger radii, which my student 
> traced to
> radiation leaking around the perimeter of the lead wall.  At that time 
> the cave dimensions were smaller horizontally than they are now.  
> Let's simply extend the lead wall to fill the entire cave interior 
> cross section and leave it at that.  That way the wall can be moved 
> upstream/downstream in the layout without impacting the civil design.
>> The facility drawings are available on the M drive. If you cannot 
>> access them, I can send .pdf of pertinent sheets.
>> M:\planteng\12_GeV\Design\Hall_D_Design\Final_Design\Draft_Final_Submittal\Dwgs
>>
>> Thanks,
>>
>>        Tim
>

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