Coma-dominated aberration in magnetically deflected electron beams

The aberration of coma, occurring in a magnetically deflected electron beam, has been studied. Shapes of the deflected spot and equal-density contours within it have been calculated for the cases where the density distribution across the beam before deflection is assumed to be either uniform or Gaussian. When coma is close to its minimum, the shape of the spot assumes a fan shape. © 1967 The American Institute of Physics.