>
> There are no lifting fixtures on
the pole so I assume it is planned to use
> the M30 tapped holes. Should
we build a fixture to bolt on here?
Yes, you are right there is no such
lifting fixtures in the current design. And we need them, you can add
anything you think is reasonable..
>
> The pining system is clearly show which is nice.
What is the tolerance
> given by the 40H9 spec?
>
> I assume the hole pattern in view
B-B is for the pole support structure.
> Is this correct?
They will be used to support the
coils.
>
>
Has anyone considered making the pole from another material than the
>
return yoke? Would you gain anything from an small air gap between the
>
pole and the yoke?
We don't intend to specify the
materials for the tagger yokes. The manufacturer can choose what ever they want
as along as they can meet the specifications. For the pole shoes, we
require soft steel AISI 1006 or equivalent.
By introducing a small gap, you can
get better magnetic filed uniformity.
>
>
> Drawing 9086-03-00-00
AD
> =======================
> I have not looked this over in
detail. What were the arguments for and
> against this structure? I like
that you have one massive structure to
> mount the magnets. You also seem
to have a well thought out jack system to
> precisely adjust the magnets
to each other. What I do not like is that
> this is mounted on the floor.
Once you have adjusted the magnets to
> each other and have mapped the
magnet you need to make sure no one can
> touch the adjusting screws! Then
I see no freedom to move the assembly.
> The spec. on settling of teh hall
is up to 2 inches with a differential
> settlement of half this. I assume
this means that the tagger hall can
> move up to 25mm relative to the
collimator over time. Do we need to move
> the magnet stand to accommodate
for this?
>
The reason we need a strong
support is that no
relative motion among
the tagger assembly components is allowed (precision
alignment, vacuum seals, etc),
although movement of the entire assembly as a
unit is acceptable (it can be realigned as a
unit if necessary).
The tiny change of distance from the hall to the
collimator is not a big issue, but if this affects the alignment, we
probably need to adjust the magnets assembly.
> Drawing 9086-11-00-00 AD
>
=======================
> I am not going to comment on this drawing as Tim
will know infinitely more
> about it than me.
>
> Drawing
9086-09-00-00 AD
> ===========================
> As far as I can see
the purpose of these brackets are to help support the
> exit window
against he vacuum forces. Do you have a writeup to on the
> stress
calculation for the vacuum chamber? did you look at how thick the
> flange
would have to be to make it self supporting? (This is probably a
> big
number)
>
Yes, these brackets are used to
support the vacuum box. We still need a FEA calculation to optimize the rib structure for stiffening the vacuum
box.
>
>
Drawing 9086-02-01-00 AD
> ==========================
> The bottom
pole piece has big cutouts on the side for bolts to mount it to
> the
yoke. In the Protvino design you can simply make the top and bottom
>
mounting the same. If you have the iron up on wood blocks you can put
the
> bolts in from the bottom.
We should try to avoid this kind big
cutout, because it will affect the field uniformity.
Because the big strongback support
will block the access from the bottom side, how to mount the bottom pole
shoes and return yoke on the bottom yoke is a problem. If we can
get large crane, then probably we can preassemble them together, then
put them on the support structure as a whole unit.
>
> Drawing 9086-02-00-00 AD
>
========================
> The yoke plates are bolted together but not
pinned. Why?
> There is a 30x30mm channel for the photon beam. Is it
foreseen to have a
> flange on the vacuum chamber to mount this? There are
no preparations for
> survey fixtures on the top of the magnet. What is
needed?
> How do you pick up and move the individual iron pieces? I see no
tapped
> holes for lifting eyes.
> Will we need leveling fixtures on
the magnet iron?
Yes, there should be a flange on the
vacuum chamber to mount the photon pipe. The protvino people made a
mistake, they should put a flange on the vacuum chamber.
We have a plan to use position pins
on the pole shoes and on the floor to align the magnet. ( please look
at Jim Kellies presentation for the tagger review). I will provide the
co-ordinates for these position pins.
Of cause we need tapped holes
for lifting.
>
> Drawing 9086-00-00-00
>
======================
> The wall if the vacuum chamber is 15mm thick and
the lip running around
> the pole gives you an effective 30mm thick
steel flange. You could in
> principal have a support fin 150mm from the
edge. Are you sure you need
> the small support brackets to the poles on
the window side? The big
> brackets to the magnet are probably critical.
When you computed the
> stress on the magnet and the deflection on the
pole did you include the
> brackets and the total force on the
brackets?
>
> When we measure the field we will have no vacuum. If
the poles
> move due to the vacuum force then this will change our field
in a way we
> do not know. Do we need to somehow measure the vacuum forces
on the
> brackets and then artificially induce this force when we
map?
>
We will need these
brackets to compress the O-ring uniformly. If the vacuum box is stiff enough, the magnet itself will
provide the forces to compress the O-ring. But the thin window is ~10
meters long, it is not easy to achieve self-supporting for the vacuum
chamber. Any way, we need a good FEA calculation for the vacuum
chamber. If we can find a way to make the chamber stiff enough, then we will not
need these complicated brackets any more.
>
> General Questions
> ======================
>
What is the manufacturer and model number of the NMR probes you want to
>
use?
Metrolab, PT2025 NMR
TESLAMETER.
> What
precision is needed for the current measurement of the magnet?
For operating at 1.5 T, the conductor
current need to be 143 A. We need at least 10 ppm precision.
>
> How big is the JLAB mapping
machine and what precision do the hall probes
> have?
I never see this machine before. The
precision is not a problem for us. you can easily achieve a
precision of 0.01%.
>
> What iron did you simulate in
TOSCA?
Tosca default(AISI 1006), I also used
AISI 1010.
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
- Follow-Ups:
- Re:
- From: Jim Stewart <jstewart@jlab.org>