sPHENIX discussion of the superconducting solenoid

[EdwardOBrien <eobrien AT bnl.gov>]

        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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