Re: Hodoscope location

[Tim Whitlatch <whitey@jlab.org>]

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
>
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