[Sane-analysis] Follow-up on tracking through the reversed target field

[Whitney R. Armstrong]

> If the beam were coming in at an angle like in Oscar's plots, you'd
> also think we'd see something in the cross-hair plots.  Here's an
> attempt to show what I mean:
> http://twist.phys.virginia.edu/~jdm2z/sane/cross-hair.png
>
> I haven't taken a close look at this, but here are a couple slow
> raster plots from the 72700's super-imposed upon a picture of the
> cross-hairs.  Neither of these show the cross-hairs shifted.
> http://www.jlab.org/~sanetarget/sane%20pictures/target388.html<http://www.jlab.org/%7Esanetarget/sane%20pictures/target388.html>
> http://www.jlab.org/~sanetarget/sane%20pictures/target389.html<http://www.jlab.org/%7Esanetarget/sane%20pictures/target389.html>
>

Here is the crosshairs for run 72613, which is in my tech-note. I have put
two lines of equal length on the graph. They highlight the apparent
asymmetric cup/crosshair geometry.

It appears from the image that the crosshairs were not in the middle, but
they were, as the photo shows.
Also, the radiation damage to the bottom of the cup is consistent with this
cross hair image showing the beam hitting something at the bottom.
This could be due to the magnetic field being reversed.

Cheers,
Whit
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