Figure 2. trajectory of magnetic flux lines within the magnetic lenses CL1, CL2, CL3, CL4, CL5, CL6

From

Effect of the Geometrical Shape of the Magnetic Poles and the Distance between Them on the Focal Properties of the Condenser Magnetic Lens in the Scanning Electron Microscope (SEM)

Mohammed A. Hussein

International Journal of Physics. 2016, 4(5), 130-134 doi:10.12691/ijp-4-5-3