[Tpe] TPE: downstream collimator

[Larry Weinstein]

Dear Folks,

The downstream collimator is a cylinder 40 mm ID, 98 mm OD and about 6" 
long.  It is currently lead and we would like it to be tungsten (based 
on Cristian's simulation results).

  1) The downstream collimator will be tungsten ID 40 mm, OD 76.2 mm 
with a lead jacket ID 76.2 mm, OD 98 mm.  It will take 4-6 weeks to get 
a bigger piece of tungsten so that the entire piece is made of 
tungsten.  We do not have that time.
  2) Dave K suggests that we taper or step the ID of the tungsten to 
reduce the effects of a possible misalignment and to let the tungsten 
also be its own clean-up collimator.  Do we want the collimator to be ID 
40 mm for the first half (3") and then ID 42 mm for the 2nd half?
     a) Do we want a step in the collimator?
     b) If so, where do we want the step (how far downstream)?
     c) How big do we want the ID change to be?

I will discuss this with Dave Monday (and I will not be available tomorrow).

- Larry

-------- Original Message --------
Subject: 	collimator at target
Date: 	Thu, 14 Oct 2010 16:56:55 -0400
From: 	David Kashy <kashy at jlab.org>
To: 	Larry Weinstein <weinstei at jlab.org>



Hi Larry,

The shop tells me to get tungsten of 4" OD will be 4-5 weeks just for
the material, I called a place my self and they said 5-6 weeks. I don't
think we should risk the delay since there is a piece at the shop that
is 3" od and just over 6" long.

I did have an idea that you might want to consider.

We could make a taper or step in the ID so that slight miss alignment of
the collimator has less effect that would be something like making the
first 2, 3 or 4" with 40 mm id and the final 4 , 3 or 2 inches is 42mm
or 44mm

Let me know

Dave

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