Optimizing the energy bandwidth for transmission full-field X-ray microscopy experiments.

Malte Storm,Christoph Rau,Florian Döring,Silvia Cipiccia,Shashidhara Marathe,Christian David

doi:10.1107/s1600577521011206

Abstract

Full-field transmission X-ray microscopy (TXM) is a very potent high-resolution X-ray imaging technique. However, it is challenging to achieve fast acquisitions because of the limited efficiency of the optics. Using a broader energy bandwidth, for example using a multilayer monochromator, directly increases the flux in the experiment. The advantage of more counts needs to be weighed against a deterioration in achievable resolution because focusing optics show chromatic aberrations. This study presents theoretical considerations of how much the resolution is affected by an increase in bandwidth as well as measurements at different energy bandwidths (ΔE/E = 0.013%, 0.27%, 0.63%) and the impact on achievable resolution. It is shown that using a multilayer monochromator instead of a classical silicon double-crystal monochromator can increase the flux by an order of magnitude with only a limited effect on theresolution.

Highlights

This study presents theoretical considerations of how much the resolution is affected by an increase in bandwidth as well as measurements at different energy bandwidths (ÁE/E = 0.013%, 0.27%, 0.63%) and the impact on achievable resolution
Full-field transmission X-ray microscopy (TXM) is an established modality for nano-tomography measurements as it can offer short acquisition times and large fields of view which make it interesting for in situ applications which rely on fast measurements
We have shown that TXM experiments are possible with larger energy bandwidths than specified by the Fresnel zone plates (FZPs) resolution criterion and that the FZP resolution criterion of ÁE/E 1/N can be violated with only a moderate deterioration in experimental performance

Summary

Introduction

Full-field transmission X-ray microscopy (TXM) is an established modality for nano-tomography measurements as it can offer short acquisition times and large fields of view which make it interesting for in situ applications which rely on fast measurements. Common TXM setups still require relatively small effective pixel sizes on the detector because the achievable X-ray magnification is typically limited by the working distance required to be compatible with in situ environments. This fact prevents most beamlines from using efficient photon counting detectors and they must rely on scintillator-based detector systems combined with a CMOS or CCD chip. As scintillators emit over the full solid angle, only a fraction of the emitted photons can be collected in the camera system which makes these systems very photon inefficient

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