Multilayer interference mirrors as components for soft x-ray WDS monochromators and tunable radiation sources

摘要

Multilayer interference mirrors (MIMs) are widely used as low-resolution monochromators for soft x-ray wavelength dispersive spectrometry (WDS). It is now possible to fabricate multilayer monochromators with medium resolution by etching MIMs with a large number of bilayers according to the profile of a lamellar grating. It will be shown both theoretically and experimentally that these multilayer gratings with appropriate characteristics can be used as monochromators; for soft x-rays, whose spectral resolving power is considerably improved with respect to mere interference mirrors. Moreover, tunable soft x-ray sources based on the interaction of medium-energy electron beams with periodic multilayer structures are presently being developed in several countries. The physical processes involved in this type of sources belong to the class of quasi-Cerenkov emission. Among them are resonant transition radiation and parametric radiation. We present the basic concepts and the first experimental results concerning this new type of sources which should be very interesting for WDS. Copyright (C) 2007 John Wiley & Sons, Ltd.