This issue summarises what we know (so far) about the magnetic axis of FC2, USS and DSS and the cross-checks that have been made.

• Item #2: FC2 current axis estimates
  • Axis in mapper co-ordinate system
  • Axis w.r.t. fiducials in R9 co-ordinate system
  • Axis w.r.t. PCD
• Item #3: USS current axis estimates
  • Axis in surveyed co-ordinate system
• Item #4: DSS current axis estimates
  • Axis in surveyed co-ordinate system
• Item #5: Method summary
• Item #6: Alternative axis cross-check using |B|
  ...

FC2 axis estimates¶

The mapper was centred and surveyed w.r.t. the centre defined by the inner flanges of the warm bore. This was related to the fiducials by a second survey within the R9 network of survey nests. First determine the axis in the mapper's co-ordinate system, then translate to the R9 network.

• Define '_z_' as the longitudinal co-ordinate
• Define '_x_' as the horizontal co-ordinate
• Define '_y_' as the vertical co-ordinate

Magnetic axis in the mapper system¶

• The magnetic axis is assumed to be a straight line (as the coils are wound on a common bobbin), which has the form:
  • x = az + b
  • y = cz + d
• a and c are rotations around the y and x axes respectively, b and d are offsets.
• Within the mapper system, the two flanges are at approximately z = 918mm and z = 1762mm (the latter being the side with the inner flange).
• Have determined the (x, y) co-ordinates of the axis at these locations, and the equation of their lines, at different currents and in Flip and Solenoid mode.

USS axis estimates

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DSS axis estimates

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Method summary

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Alternative cross-check using |B|

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Note talk at CM42

https://indico.cern.ch/event/374187/session/6/contribution/29/material/slides/1.pdf