[Halld-tagger] Tagger magnet excitation studies

[Richard Jones]

Hello Dan and all,

Let's put this at the top of the list for the next biweekly meeting's agenda, on 6/24.  Sascha, do we need answers before then?

-Richard J.

On 6/11/2013 4:09 PM, Daniel Sober wrote:
> I have finally gotten around to analyzing Yang's Tosca midplane maps at excitations of 6, 9, 12, 14, 15, 16 and 17 kilogauss.  The results are posted at http://faculty.cua.edu/sober/HallD/Excitation .
>
> The most informative single plot is probably the one labeled "Plot vs B" (http://faculty.cua.edu/sober/HallD/Excitation/Bnorm_vs_B.pdf). If the permeability were infinite, the field per ampere-turn would be constant at about 0.83 gauss/amp-turn.  The figure shows that the saturation effects are already significant at the operating field of 15 kG.  If you look at the "fine" plots of B/NI versus z, you will note that the saturation effects are not uniform through the magnet.  For B>15 kG, the field at the ends of the magnet (z = ±300 cm) is slightly higher than the field at the center (z=0), while at lower fields the z-dependence is negligible.
> Conclusions for mapping:
> 1.  If there is any possibility of running above 12 GeV, we must map at the highest conceivable field.  (What is the expected power supply limit?)
> 2.  To allow for running at beam energies other than 15 kG, we should map the magnet at 16, 15, 14, 12 and 6 kG.  Some of these maps may be made at coarser granularity if time is short.
> 3.  Note that the Tosca calculations were made using the "default steel" permeability table, so we must make measurements at several excitations to test the reliability of the Tosca calculations.
>
> I will be traveling in Europe from June 13-July 14.  See you next month.
> Dan
> -- 
> /Daniel Sober
> Professor
> Physics Department
> The Catholic University of America
> Washington, DC 20064
> Phone: (202) 319-5856, -5315
> E-mail: sober at cua.edu <mailto:sober at cua.edu>/
>
>
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