remarks to the drawings

[Elke-Caroline Aschenauer <elke@jlab.org>]

Dear Sergey,

I'm not sure you had already a look to
http://www.jlab.org/Hall-D/software/wiki/index.php/Tagger_Engineering_Design
but as we agreed in your phone meeting Richard set up this page so some
information is documented.
I will include below the questions from Franz and Guangliang, I think it
would be nice if you could address them in out meeting on Monday.

Thanks elke

p.s. As soon as I receive the other drawing from Tanya I will put them in
/group/halld/civil/tagger_apr_07 and send a mail

Questions by Franz and Guangliang
=================================

*  Discussion and questions regarding the Serpukov tagger design
   drawings
o Franz Klein: The design effort should address the following
               areas of concern.
1. Field and trajectory changes due to small misalignment of the magnets:
   this was answered in detail by Yang's simulation.

2. Stress on vacuum chamber with 2 big magnets attached
   (relative motion of energized magnets and evacuated chamber).

3. Sealing the large vacuum chamber at the contact with the magnets:
   large o-rings that show up in various drawings as two different shapes.

4. I don't see how the largely reduced number of brackets around the pole
   stems can insure that the o-rings stay in place when heavy pole shoes are
   placed on top.

5. I'd like to see an explanation of how the system (magnets+chamber) is put
   together.

6. I want to see what FEA or other stress analysis has been done on the new design.

7. There are comparatively detailed drawings about the stands but I cannot
   imagine that the stand for the vacuum chamber is sufficient to account for
   the large moments (vertical+horizontal(x-dir)).

o Yang Guangliang: About the drawings provided by the IHEP group,
  I found the following.

1. In general, these drawings are based on our two identical magnet tagged design;
   the layout of the tagger has not been changed.

2. Some of detailed things have been changed, they are:
1. The number of brackets which are used to compress the O-ring and also to
   counteract the vacuum force has been reduced to half of the original number.
   The way to attaching this bracket to the pole shoes has been modified.
2. The brackets used to support the coils have been redesigned.
3. The vacuum chamber design has been modified slightly. A long metal strip was
   welded to those vacuum chamber edges which are around the pole stem, and are
   used to attach the O-ring compressing brackets to the vacuum chamber surface.
   At the same time, the pole shoe profiles have also been changed accordingly to
   accommodate the modified vacuum chamber.
4. The O-ring groves were made on the vacuum chamber.
   Previously, we used a long strip of metal attached to the pole shoes lips
   to act as the O-ring groves.
5. There is a detailed design about how to bolt the yoke and pole shoes together.
6. There is a detailed design for the quadrupole magnet and stands.
7. The brackets used to support the vacuum chamber have been modified.
8. The thin window has been modified.
9. The hole through the return yoke of the second magnet which is used to
   accommodate the photon pipe is not in the correct position and direction.

3. There are several questions that I want to ask. They are:
1. Have they done any stress analysis for the whole magnet to determine the
   location, size and the number of the bolts which are used to hold the magnet
   together? And what kind of method can be used to control the magnet deformation
   within limit when the magnet is operating at 1.5 T?
2. Have they ever done any stress calculation for the vacuum chamber to determine
   how to support it?
3. Have they done any stress analysis on the brackets to see if the brackets are
   strong enough? How many brackets are needed?  From my point of view, I think the
   number of brackets used to compress O-ring is too small, and the number of
   brackets which are used to support the coil is too large.


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