Re: Collimator layout

[Tim Whitlatch <whitey@jlab.org>]

Thanks Richard. We will proceed and reissue layout with all the comments.

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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