sPHENIX discussion of the superconducting solenoid

[EdwardOBrien <eobrien AT bnl.gov>]

        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
>
>


--
Dr. Pasquale Fabbricatore
INFN Sezione di Genova
via Dodecaneso 33, 16146 Genova Italy
Direct tel  + 39 010 3536340
Laboratory  + 39 010 3536437
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E-mail   pasquale.fabbricatore AT ge.infn.it
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