Re: question on pair spectrometer shielding

[Alexander Somov <somov@jlab.org>]

Hello Richards,

I am sorry, I  missed thread. I was talking about
the iron shielding blocks which we were planning to
install after the vacuum chamber and ps scintillator
counters, i.e., about 2.4 meters downstream the beam
from the pair spectrometer magnet. Are we discussing
the same blocks ?

Cheers,
        Alex



On Mon, 23 Mar 2009, Richard Jones wrote:

> Alex,
>
> The iron will completely change the field, won't it?  Then it makes no sense 
> to move it, map it, and then put it back.  We might as well not map it!  The 
> magnetic forces will be big, maybe bigger than the weight for some blocks. 
>> - There is enough space after the chamber in the case
>> we decide to unscrew it and move aside to map the field
>> (we could probably make inserts in the chamber to measure
>> the field) 
> -Richard J.
>
>
> Alexander Somov wrote:
>> Richard,
>> 
>> I don't understand completely your concerns:
>> - There is enough space after the chamber in the case
>> we decide to unscrew it and move aside to map the field
>> (we could probably make inserts in the chamber to measure
>> the field)
>> - The platform can hold heavier objects, should not be an
>> issue (the platform support should be beneath the blocks)
>> 
>> We can replace cheap iron blocks with a band of lead bricks;
>> (we will need  ~20/30 radiation lengths of shileding anyway).
>> that is what we were thinking of doing originally.
>> Let's discuss it during the meeting.
>> 
>> Alex
>> 
>> 
>
>