The use of phase modulating zone plates as objective optics for X-ray
microscopy in the energy range 1-8 keV is considered, and a new analyt
ic method for determining the optimum zone thickness is derived. The a
dvantages, in terms of manufacture and ease of use. of using the secon
d diffraction order of the zone plate, instead of the first, are discu
ssed. (C) 1997 Elsevier Science B.V.