[Sane-analysis] Minutes of April 13 Analysis Meeting

[Oscar Rondon-Aramayo]

On Wed, 13 Apr 2011 18:51:25 -0400
  Narbe Kalantarians <narbe at jlab.org> wrote:
> _*Whit:*_ Looked into scenario of if the target field was reversed.
> http://quarks.temple.edu/~whit/SANE/talks/sane_magnet_reversed.pdf

Here are the results of my standalone code to track through the target 
field, for 4.7 and 5.9 GeV. Whit is right that the beam center is shifted up 
only a few mm at the target center.
http://twist.phys.virginia.edu/~or/sane/analysis/targeta.ps
http://twist.phys.virginia.edu/~or/sane/analysis/targetb.ps

The lines going exactly through the center are straight line projections at 
the same starting angles.

But the 1 to 1.1 cm raster envelope hits the top of the cup for at least the 
downstream half of the cup for 4.7 GeV, and for much of the same region for 
5.9 GeV. The target group should confirm if evidence for radiation damage to 
the top of the cups was seen when the inserts were removed.

In particular, the cups of insert C which were used without reloading during 
the last part of the 4.7 perp data and the early part of the 5.9 parallel 
would have been more likely to show damage signs when removed during the 
rotation from 80 to 180. Given the very shallow angle of incidence on the 
cup's top, the damage would have been very substantial.

To make the plots I used vertical downward offsets at z =-150 cm from the 
target center that correspond approximately to the numbers in the chicane 
settings table. Keep in mind that those settings are for the energies 
indicated on the table, but for the plots I used the actual energies of the 
run. The offsets I used are -7.07 cm for 4.723 GeV (table is -6.6 cm) and 
-5.7 cm for 5.892 (table is -5.6), which put the bent tracks almost exactly 
at the target center.
http://hallcweb.jlab.org/experiments/sane/rondon/chicane.pdf

I used the vertical angles on the chicane table, although the exact angles 
would be slightly different, at about the millidegree level.

The total deflection for 4.7 GeV is 5.8 degrees, which projects to 3 m above 
the standard hall dump. In summary, it still seems unlikely the field was 
reversed.

Cheers,

Oscar