Deep multilayer gratings with adjustable bandpass for XRF spectroscopy

We propose here a deep multilayer grating with adjustable bandpass as an alternative dispersing element to PET crystal in WDXRF spectroscopy. When making a multilayer grating, we remove part of the reflecting planes of a multilayer, allowing radiation to penetrate deeper. Since the resolution, or the bandpass, is reciprocally proportional to the penetration depth, we improve the resolution and reduce the bandpass of a simple multilayer mirror without affecting the reflectivity. By changing the grating land/period ratio, the amount of the removed material can be continuously varied and, thus, the extinction depth and the bandpass, or resolution, can be continuously varied. In this way we can find an optimum between required resolution and flux for a particular application. Retaining all the advantages of multilayer mirrors, such as stability to moisture and heating, multilayer gratings allow improving resolution of multilayers and making their performance comparable to PET crystals.