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Nr 3: 2D Field Quality Calculation

Goal

Demonstrate options for the calculation and visualizations of field-quality in the aperture of accelerator magnets.

Description

  • Virtual Devices:

    • Harmonic coils: We define a number of harmonic coils. Coil 1 measures relative harmonics, related to the skew quadrupole component A2, in the center of the aperture. Coil 2 measures the relative harmonics in an off-center position. Coil 3 measures relative harmonics, related to the skew quadrupole component B2. Eventually, coil 4 measures absolute harmonics.
    • More Options: In the "More Options" table we turn coil 3 by -45 degrees, so that effectively the coil measures a skew quadrupole rather than a normal quadrupole. This option can also be used to determine the impact of misplacement on field quality. The second line in the "More Options" table designates the main harmonic of coil 1 to be used as reference value for the relative multipoles measured by coil 2. We find in Plotting 2D, plots 2 and 3, that this effectively allows to extend the field quality calculations over a wider range.
    • Field along a path: We define a straight path along the x-axis, as well as a circular path around the coil. The first graph allows to visualize the gradient field, the second lets us measure stray-fields.

  • Graph: The first two graphs display relults of the "Field along a path" measurements in the Virtual Devices widget. Graph 1 displays the rising x-component of the field along the x-Axis. We see that the field changes linearly only in the center of the aperture. The second graph displays the stray-fields. Graph 3 and 4 are drawn on a single plot, representing the radial and the azimuthal field components around the reference circle of the harmonic coil.

    • More Options: In the "More options" table we assign labels and a plot title to graphs 3 and 4 in plot 3.

  • Plotting 2D: The first plot displays the powering and the field pattern. Plots 2-4 display the relative field error w.r.t. the main component of the respective harmonic coil (1-3) in a so-called IRIS plot. The red circle designates the limit of the circular good-field zone, i.e., the zone inside which the relative field error is below a reference value. Default is 1 unit. A different limit can be set in the "More options" of the Virtual Devices widget. Plots 5 and 6 show the contribution of each strand to the sextupole and decapole component in harmonic coil 3. Remember that coil three is turned by -45 degrees, so that we actually display the skew sextupole and skew decapole contributions in tesla.

Files

use_case_3.zip

  • fieldQuality.data
  • roxie.bhdata
  • roxie.cadata