Re: Hodoscope location

[Alexander Somov <somov@jlab.org>]

Hello Tim, Richard,

If we need more space for maintenance and decide to shrink
the chamber a bit, I can go quickly through the mc and check
the resolutions.

Cheers,
        Sascha


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
>> 
>