From: Arthur W. Brooks
Sent: Wednesday, January 02, 2008 2:44 PM
To: Michael C. Zarnstorff
Cc: Thomas G. Brown; Hutch Neilson; Michael R. Kalish; Phil
Heitzenroeder
Subject: Revised Trim Coil Configuration Performance

Attachments: 122107.xls

Mike Z,

Attached are some comparisons of the performance of the Revised Trim Coil Configuration (aka 122107). 

Without the Midplane Coils, the modifications made (ie more, smaller coils with some moved closer to the MCWF) result in higher max currents needed for comparable island suppression. This is driven by a ~10% reduction in trim coil area caused by splitting coils and avoiding interferences. 

This is again based on the 95% level for the random assembly of coils, including known background field error sources, as was done for the Constructability Review. 

The Midplane Coils allow for a modest reduction in currents when used with the Revised Trim Coil Configuration or with the Original Configuration (36 coils, 24 circuits).

I looked to see if we should include the Midplane Coils but maybe eliminate some of the others (inner or outer). The Inner + Midplane Coils would be the better combination but still not as good as just the Inner + Outer coils.

For reference, I include the Inner, Outer and Midplane Coils separately, none of which is sufficient by themselves without driving currents significantly higher.

Bottom line, based on this linear perturbation analysis, is the midplane coils do not add much. 

Art