sPHENIX discussion of the superconducting solenoid

[Achim Franz <afranz AT bnl.gov>]

Ed, 

if you have no end-plugs it creates larger radial field components that 
create these excess forces and yes its the shear strength between the mandrel 
and the coils epoxy. For fs- and e-PHENIX this might be an issue.

The 1.37T agrees with Wuzheng's calculations … 

> On Mar 26, 2015, at 15:00 , EdwardOBrien <eobrien AT bnl.gov> wrote:
> 
>       Hi John, Kin,
>        I'd like to make sure that I understand this.
>       In Pasquale's answers to Kin's questions
>       he wrote:
> 
>       8) The compressing force of 380 MT can be  held by the coil
>       (about 10 MPa compression)
> 
>       9) The effect of type, size and position of iron tips shall be
>       carefully evaluated.
> 
>       10) Without iron tip the radial field at the coil ends
>       increases, causing an increase of the axial force.
>       During the factory test (without yoke) we limited the
>       field to 1/3 of the nominal field. For this coil it is better
>       not overcome 20 MPa axial pressure on coil.
> 
>       Now he has written that the compressive force w/o
>       the endcaps increase the compressive fore by 85%.
>       Do I interpret this to mean that at BaBar the coil operated
>       with a 10 MPa compressive axial force and that w/o the pole tips
>       we will be operating with something 85% higher, or 18.5 MPa?
> 
>       If so we are approaching the the 20MPa axial pressure he warned
>       us not to exceed.
> 
>       Also do you understand what sets the 20 MPa threshold? Is
>       that the shear strength of the epoxy connection between the
>       coil and the mandrel?
> 
>       Thanks.
> 
>       Ed
> 
> 
> On 3/26/2015 1:43 PM, John Haggerty wrote:
>> -------- Forwarded Message --------
>> Subject: Babar coil without end caps
>> Date: Thu, 26 Mar 2015 18:30:13 +0100
>> From: fabbric <Pasquale.Fabbricatore AT ge.infn.it>
>> To: John Haggerty <haggerty AT bnl.gov>, Yip, Kin <kinyip AT bnl.gov>
>> CC: Mills, James A <mills AT bnl.gov>, Than, Yatming (Roberto) <ythan AT bnl.gov>
>> 
>> Hi all.
>> 
>> I did a fast computation with Comsol removing the
>> end caps (indeed I put to 1 the magnetic  permeability).
>> 
>> At the same current the central magnetic field is reduced from 1.5 T
>> to 1.37 T and it is more inhomogeneous.
>> The peak field on the conductor seems to
>> be a bit higher  and placed at the coil
>> axial ends (so the current cannot be increased
>> or we have a reduced stability margin).
>> The axial compression increases of 85%
>> (i.e. a bit less than double).
>> 
>> My first impression is that this solution could be considered
>> if you can accept a reduced magnetic field.
>> 
>> Best regards
>> 
>> Pasquale
>> 
>> 
>> 
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