The double monochromator geometric theory and compensation of aberrations

The light path function for the double monochromator is constructed, and th e formulas of account of the members of its expanding in ascending power se ries adequate for the defocusing and the first order astigmatism aberration s are found. On the basis of results of the minimisation of obtained expres sions the opportunity of construction of a double monochromator so that the second monochromator fractionally compensates aberrations of the first one is analysed. It is also noticed, that in the scheme of the double monochro mator under certain conditions compensation of an astigmatism of the second order is automatically carried out. It allows to use a deviation angle of the scheme for more complete compensation of other aberrations and to devel op double monochromators with the improved performances.