Re: Hodoscope location

[Franz Klein <fklein@jlab.org>]

Tim and Richard,

last Friday James showed me the design drawing. My initial worry that we 
won't have more clearance but 2.8cm (for largest scintillator) was based 
on the pdf file James sent around on 1/22. However, the vacuum chamber 
drawing is largely conceptual: the flange for the long window is 1" thick 
and not detailed. It is more realistic to assume a 1/4" plate as flange, 
which gives enough space for a cover plate (which will be suspended from 
above and fall into a grooved beam).

Greetings

Franz

On Wed, 4 Feb 2009, Tim Whitlatch wrote:

> Thanks Richard.
>
> Yes we are talking about shrinking the vacuum chamber. Right now we have 
> about 3cm. We can make due with this but do not have an easy way for vacuum 
> sealed plate. I do not think this is required, but hearing protection would 
> be required to work in the area at all times.
>
> Tim
>
> Richard Jones wrote:
>> Tim,
>> 
>> If you mean 20cm of open space normal to the window, I don't think we want 
>> that much distance between the window and the detectors.  At a crossing 
>> angle of 10 degrees, that would mean more than 1m of electron trajectory 
>> after the window.  Of course, we are talking about shrinking the vacuum 
>> chamber by 20cm, not moving the focal plane by 20cm, right?  Yang can tell 
>> you that moving the focal plane is a much bigger job!  You could gain that 
>> space by shrinking the vacuum chamber, but it would affect our resolution. 
>> We could simulate it, but I am pretty sure that the effect would be 
>> significant degradation in the resolution.
>> 
>> Richard Jones
>> 
>> 
>> 
>> Tim Whitlatch wrote:
>>> Hi all,
>>> 
>>> How critical is the spacing  (air gap) between the hodoscope scintillators 
>>> and the vacuum window? Is 20 cm ok to allow a mechanism for a window cover 
>>> during maintenance? If not, we will have to slide the protective plate 
>>> over the window.
>>> 
>>> Thanks,
>>> 
>>>
>>>    Tim
>> 
>

===============================================================
                   Franz J. Klein, Associate Professor
                   CUA, Department of Physics
                   Washington, DC 20064
   office: Hannan Hall 206          phone: 202-319-6190
   or: Jefferson Lab,CC F-243       phone: 757-269-6671
---------------------------------------------------------------
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