Contrast optimization of Fresnel zone plate imaging

Fresnel zone plates (FZPs) are circular diffractive elements that operate as a lens for x-rays. They have gained interest in the field of laser-plasma physics due to their ability to achieve higher spatial resolution than pinholes. Their design and implementation are complicated by the fact that a significant amount of the x-rays passing through the FZP will not diffract (zeroth order) and present a background to the measurement. This background can be large and inhomogeneous depending on the geometric setup of the experiment. Here, we present calculations of the diffracted (first order) and un-diffracted (zeroth order) flux profiles, which makes it possible to optimize the contrast between the first order imaging rays and the zeroth order background. Calculations for the implementation of a central block in the FZP, designed to block the zeroth from the entire field of view, are also presented.

Automated summary

Fresnel zone plates (FZPs) are diffractive elements that act as lenses for x-rays and have higher spatial resolution than pinholes. However, a significant amount of x-rays passing through FZPs do not diffract, resulting in a background noise. This study presents calculations of diffracted and un-diffracted flux profiles, allowing the optimization of contrast between imaging rays and background noise. Additionally, the implementation of a central block to block the zeroth order diffraction from the entire field of view is discussed.