To:	Distribution	30 June 95
	From:	Martin Nordby
	Subject:	Minutes of Near IR Task Force Meeting of 30 June 95


Mike and Hobey reported on their progress in designing a Q1/B1b hybrid 
quad/bend permanent magnet in place of the off-centered (or maligned, 
in both senses of the word) Q1.
The latest design for the new hybrid produces a 11.6 mm radial 
clearance inside the Support Tube.  According to Roy and Fred, this 
should be enough for SVT cables.
According to Mike, this hybrid behaves optically identically to the 
previous off-center design.  Mike and John Seaman will investigate 
further.
Mike also will look at the higher harmonics of the new hybrid.
Hobey and Gordon have been looking at what influence the outer dipole 
field has on the inner quad field.  Specifically, does the diple field tend to 
reduce the field strength of the quad?  Preliminary estimates of the peak 
dipole field present in the quad Sm2Co17 is 10 kGauss.  This uses 
StanŐs most recent radial geometry, and assumes a 16 block magnet.  It 
is not clear whether this is enough to damage the quad field.  They will 
continue looking into this.
(per Mike) Dave Coupal has completed the geometry and turtle decks for 
the shielding simulations for the Drift Chamber, and will start running 
simulations of various shielding combinations next week.  He should 
have something to report by next FridayŐs meeting.
Martin showed results of a tolerance study of the gap between the Vertex 
Chamber and the SVT.  The current design has a gap of 3.69 mm.  
However, at the worst-case tolerance stack-up of position and dimension 
tolerances of the two assemblies, this may be reduced to around 1.78 
mm.  To completely close this gap by tipping the B1 magnets, the tip 
angle would have to be 32 mrad.  This is far more than the 2.2-4 mrad 
range that has been estimated for the Support Tube deflection-induced 
tipping.  This suggests that it should not pose a problem.
John Hodgson presented results of a 3-D heat transfer model of the B1 
magnet.  With a single cooling circuit at the back of B1, the temperature 
variation in B1 can be held to only 1.1 ˇC above the water temperature.  
This includes the film temperature drop to the water, the temperature rise 
of the water, and the azimuthal and axial conduction along the magnet.  
This assumes that no heat flows between the brass retaining collars, and 
the the pineapple slices of Sm2Co17 are separated by a small air gap.
Also, in a lively discussion, John pesented a graph showing that natural 
convection in the air gap between the B1 chamber and magnet should 
not play a significant role until the gap is around 5 mm wide, with the 
temperature gradient across the gap of around 28 ˇC.