[MAP] Be Wall Cavity: on- or off-axis?

[Michael S. Zisman]

I don't think a 2 cm displacement in a solenoid matters much. I would proceed. 

--Mike

Michael S. Zisman
Mail Stop 71R0211
Lawrence Berkeley National Lab
One Cyclotron Road
Berkeley, CA 94720

On Jun 22, 2012, at 3:10 PM, Daniel Bowring <dbowring at lbl.gov> wrote:

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> 
> All,
> 
> Is it necessary that the beryllium wall cavity be coaxial with the
> magnetic field in the Lab G solenoid?
> 
> Debate on this issue has slowed the design effort.  We would like to
> finish the design very soon, but one last attempt at consensus seems
> warranted.  Our next design meeting with SLAC will probably happen on
> Tuesday, June 26.  If you have strong feelings about this issue,
> please share those feelings with me before then.  (And please accept
> my apologies for the somewhat late notice.)
> 
> Please see our recent IPAC paper for background information:
> http://199.190.250.75/prepress/THPPC033.PDF
> In that design, the cavity center is 2 cm lower than the magnet axis.
> 
> Very briefly:
> 
> - Some people feel the cavity axis should be aligned with the axis of
> the solenoid.  Since we know so little about the physics of breakdown
> in strong magnetic fields, it is felt that azimuthal symmetry would
> simplify our analysis of future data.  The only way to achieve
> azimuthal symmetry is to design a cavity that is coaxial with the
> solenoidal fields.
> 
> - On the other hand, there's not much room in the solenoid.  Centering
> the cavity is surprisingly difficult once you account for nonzero
> waveguide thicknesses, bolted flanges, vacuum conductance, etc.  Given
> our time and budgetary constraints, a prolonged R&D effort in this
> direction may be unwarranted.  Especially because there is not
> currently any convincing *physics* argument in favor of such an
> effort.
> 
> These arguments are expanded in my most recent MTA-RF meeting presentation:
> https://indico.fnal.gov/conferenceDisplay.py?confId=5697
> 
> Furthermore, Yagmur has provided a link to the solenoid's field map.
> Scroll down to the bottom of this page:
> http://mice.iit.edu/mta/magnet/magnet.html
> 
> If you have input, please send it to me by Tuesday, June 26.  (Please
> do not "reply-all" to this email.)
> 
> Thanks very much,
> Daniel
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