[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: BCAL inner layer

Title:
Thanks George and Zisis,

This sounds good. I will look into the tungsten option also. There will be modest added stiffness from the stainless steel. I will run the numbers.

Cheers,

       Tim

George Lolos wrote: 
Hi Tim:

There are a number of issues here that need careful study before we
commit one way or another.  

First, the easy one:  To machine a stainless steel layer to accept
grooves for SciFi's is neither easy nor really necessary.  A flat plate
on top of the last grooved lead sheet with enough epoxy to fill the
grooves under pressure will work better.  We can use a much stronger
industrial epoxy that will adhere very strongly to the lead without
worrying about the fibers being destroyed by the chemicals in the epoxy.
 

Now the tough part.  If the steel or tungsten glued on the inner face of
the BCAL is of sufficient thickness to protect it and to add stiffness
to the structure, we will have to model it and predict what its effect
will be on low energy photons that are proving so important for the
GlueX physics.  On the other hand, if we opt for an increased ratio of
SciFi to Pb structure, we may have to use a pre-radiator (like tungsten)
to reduce electromagnetic leakage out the back, so this may be the best
solution.

I can see the use of a protective layer to avoid damage to the soft
inner layer of the BCAL, however, even if we get some damage on the lead
surface, it does not alter any of the functions of the BCAL or causes
any damage.  As for stiffness, the Pb/epoxy/SciFi structure is very
stiff and the whole thing glued on the Al plate with stiffening ribs in
the back, I don't know how much do we really gain by adding steel.  

The bottom line is that we need MC simulations to tell us what we can
tolerate or want and what price we'll pay on the physics, if any.  Our
graduate student here will model all these possibilities and then we can
revisit the issue with better information to proceed.

Cheers,

George

  
Tim Whitlatch <whitey@jlab.org> 11/06/07 7:02 AM >>>
        
Hi George and Zisis,

If you remember back a couple of months, we discussed using a stainless 
steel layer on the inner most layer of the barrel calorimeter wedges for

additional stiffness. If this was to take the place of lead, what 
thickness would we want to use (the thicker, the better for stiffness)? 
Of course we would have to have grooves machined to accept the 
fibers.This would also serve as a protective layer for assy and 
installation.

Cheers,
       Tim