I have reviewed Dennis Wright's TN-43, regarding (in particular) the
alignment of the solenoid within the yoke.

This is in follow-up to a conversation I had with Curtis Ballard today,
in which I learned that the present position of the solenoid relative to
the axis of the yoke is accurate to approximately 1 mm.  (The left-right
varies from 1.1 mm off axis to on axis over a length of 2500 mm. 
Up-Down varies from 1.3 mm to 0.8 mm in 2500 mm).

Dennis- Tech Note
(http://stoney.phys.ualberta.ca/~e614/Projects/E614TN/00043/) indicates
what appear to be unnecessarily restrictive tolerances in the abstract. 
There are two considerations:  Excessive forces due to assymetric
loading of the coils, and field non-uniformity.

With respect to the forces, it is important to consider only the results
in the transverse force, as the latter part of the work suggests a
mirror of the cryo aperture at the bottom of the yoke - which we adopted
as part of the design.

I conclude that (with respect to the Force tolerance of one ton), we
need transverse alignments (of the solenoid to the yoke) of +/- 10 mm. 
We should apply a safety factor to this, so perhaps 3 mm alignment is
safe.  (TN43, Table 3)

With respect to the longitudinal centering of the solenoid within the
yoke, we get (one ton / 6mm).  Therefore, I conclude that (with a factor
a ~3 for safety) we need to have the solenoid centered to within 2mm in
z.  (TN43, Table 4)

As concerns field uniformity, the same 2mm accuracy in z would result in
approximately a part in 10,000 variation in the field.  The assymetry
would be twice this, or about 2 in 10,000.  The field deviates less than
this in the central region (TN43, figure 3).

Errors in the transverse alignment of the solenoid result in assymetries
in the radial field.  I have a harder time defining a tolerance here,
but TN43 Figure 4 shows that a misalignment of 1mm results in variations
in the radial field of ~ 10G.  The radial integral has 5% deviations.  I
believe we need more MC to determine the effect of the radial field
assymetries on the beam.
-----------
Conclusions:

I propose on this basis that we allow the transverse misalignments of ~1
mm to remain for the present.  

I propose that we require that the solenoid be centered to within 2 mm
in z.

Please let me know if you disagree with the above two conclusions.

				nate
-- 
Nathan Rodning, Associate Chair
Professor of Physics
University of Alberta
Edmonton, Alberta   T6G 2J1
Canada
(780) 492-3518  /  Fax:  (780) 492-0714
http://www.thehungersite.com/

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