Dihedral-like electrostatic potential and analysing systems based on it: aberration coefficients and energy resolution

The essential feature of the dihedral-like potential Φ=arctan (y/x), where x and y are Cartesian co-ordinates, is the possibility to compress, i.e. to make narrower in the real space, beams of charged particles. The coefficient M of the reduction of a ribbon-like beam cross-over can be varied in the wide diapason: 1<M<20. Due to this, the resolution of two- or more-cascade dispersive systems based on Φ can be more than 10 times higher than the same value of any traditional analyser or monochromator. But aberration coefficients divided by linear energy dispersion are approximately 10 times bigger in dihedral mirror analyser (DMA), than in the traditional plane mirror analyser (PMA). That is why only 0 – 2° diverging ribbon-like beams can be treated successfully with the DMA. The experimental model of a two-cascade monochromator, the basic distance between its entrance and exit diaphragms is 150 mm and the entrance slit is 6.4 mm wide, has a resolution of 0.3%.