sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Hi,

It does seem that we need to understand more about the strain gauges, what to expect, how to use them ....
Pasquale also said Wes Craddock  is the person to ask.

In our BaBar server, we've scanned one document called "Alignment, Support Rods, Fields and Forces, Reservoir & Vacuum System.pdf"
(which I've plaed in the folder of "Volume 5 DESIGN AND QUALITY CONTROL REPORT"), Wes, Pasquale et. al. have written
a lot about the alignment and calculations.   It has 488 pages but maybe the first 283 pages (which also discuss about some old calculations
for the forces/stresses) are relevant.   Some of us (like smart engineers ?!) may need to study those ...

I've actually found that "page 128" of the above-mentioned pdf file is exactly what Pasquale's "Coil Alignment.pdf" is.

Kin

On 06/18/2015 04:39 PM, EdwardOBrien wrote:

    Hi Kin and John,
     Do I understand Pasquale's answer to mean that we need
    to understand the expected change in the tie-rod
    loading as the magnet is cooled, so that the tie-rod
    strains can be monitored as we cool down? Who at SLAC
    would know what to expect for the tie-rod strain
    gauges readings?  Craddock or Racine?


    Ed
    

On 6/18/2015 12:09 PM, Kin Yip wrote:

However this
is a point to be fully understood before cooling down the coil.
May be you could try obtaining further information by SLAC
( They operated the magnet for 10 years).

Kin,
for the test at 100 A I would only use some Hall probes in the bore
of the magnet (the center)  for checking the
ratio Field/Current in the operating condition for being sure no major
problems are.

No more than that.  Later you will need a detailled  field mapping,
especially if you
change the iron configuration moving the end caps.
The alignment should  be done mechanically. About the alignment
I am looking for some material. I know (because it was an idea of mine)
that the coil was placed with
the axis (look at the attached page) displaced about 3 mm down. The
reason was that at room temperature
the coil is suspended at 8 of the tie-rods (see II attached figure):
T1,T8,T3,T6 at one side, T11,T18,T13,T16 at the opposite side.
The remaining tie-rods should be almost unloaded.

Cooling down the coil, the suspending tie-rods contracts and the coil
moves up
of about 2.5 - 3 mm.
At 4.2K  also the remaining tie-rods are a bit loaded.
Kin, I am not completely sure about that (too long time ago). However this
is a point to be fully understood before cooling down the coil.
May be you could try obtaining further information by SLAC
( They operated the magnet for 10 years).


Pasquale


Il 17/06/2015 22:12, Kin Yip ha scritto:
> Hi,
>
> Or, is it something that you'd worry about ??  ( The physicists tend
> not to worry about it too much ... )
>
> Kin
>
> On 06/17/2015 03:42 PM, Kin Yip wrote:
>> Hi,
>>
>> Some of us (in our sPHENIX project) are asking whether we should do
>> some magnetic field measurement (during our 100 A test or full
>> current test).
>> We thought a little and it's not easy and non-trivial ...
>>
>> In BaBar, as far as you know, have they tried to measure magnetic
>> fields to find misalignment (the "magnetic center") etc. ?   Any
>> experience that you
>> may share with us  ?
>>
>> Kin
>
>