Field Mapping


  • We have data at different currents
  • For upstream SS we have survey that maps field mapper to fiducials
  • For both FCs we have survey that relates the mapper to the flanges; and we can relate the flanges to the fiducials

Aim to relate the axis to the fiducials
Aim to improve knowledge of coil dimensions

Magnetic Axis

Two algorithms exist to find the axis; quick one and slow one; both should converge on the same answer
  • Fit Bx vs x, By vs y, look for y-intercept
  • Bulk field calculation vs assumed position/dimensions of the coil
  • Calibration: misalignment of hall probes; python function in the code
  • Calibration: mispositioning of the mapper; python function in the code
  • Calibration: cross-check field integral on a loop (Maxwell law)
    Follow the calibration procedure done by Atlas

All proved on fake data

Coil Dimensions

Two algorithms exist; assume the axis
  • Brute force approach; fit to position, dimensions of the coil; go coil by coil
  • Not brute force approach; take short thin field map, long thick field map, add together linear sum of the two field maps

All proved on fake data

Other issues (spoilers)
  • MDIC paper
  • This
  • Step I papers

Risk: non-linearity in the iron in SS
Risk: misalignment of coils on the bobbin
Risk: force dependent alignment

Let's meet again: Friday 14th November