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Re: Readout crates in counting house?

Elliott Wolin wrote:
Hi Paul,

> Even with preamps, you would lose timing resolution.  Maybe this wouldn't be so 
> bad.
>
> Cost would be a big issue.  There are ~30K channels.  Assume 25 
> cents/foot/signal and each foot away from the detector costs $7500.  Your 50 
> feet would cost $375K.


I believe (hope?) that we could avoid losing resolution by using good cables,
and that cable length could be kept to a minimum.  I agree it will cost more,
but it may be worth it.  Does it really cost 25 cents/foot/signal?


> I agree strongly with you about wanting access to crates while beam is on.  How 
> about shielding the detector with concrete blocks and having the crates just 
> outside this shielding?  Or, how about turning the beam down low enough to allow 
> crate access during setup but not during actual running?


Having the crates "virtually" in the counting house, i.e. outside the radiation
area, is perfectly acceptable...we'd only need 10cm concrete shielding for full
access (e.g. the crates could be along the walls of the building).

I doubt JLab will let anyone into the hall with the beam on.


				Sincerely,
					Elliott
 

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Elliott Wolin <wolin@jlab.org>
Physicist
Jefferson Lab
Physics Department

Hello folks,
   I've been following the hall-D mailings (just in case anyone wondered). Anyway, I have some input on the idea of putting the readout outside the radiation controlled area. This is clearly to be encouraged if at all possible for the following reasons plus many others,

1) Monitoring of signals is much simplified (stick a scope on it).
2) Routine maintainance is faster.
3) Manual reset/power cycling of embedded processors is simpler.
4) The hall-D trigger (or lack of) is novel and having access to the electronics with beam on is a great advantage when the trigger is being developed.
4) Less need for beam to be shut off for accesses (How many people remember the early days of hall-B. Having the beam cut off in hall-B while some electronics is reset and not having the beam recovered for several hours.) 

If you can do it, go for it!!

--
    
                     Graham
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