Lenseless X-ray nano-tomography down to 150 nm resolution: on the quantification of modulation transfer and focal spot of the lab-based ntCT system

Abstract

The ntCT nano tomography system is a geometrically magnifying X-ray microscopy system integrating the recent Excillum NanoTube nano-focus X-ray source and a CdTe photon counting detector from Dectris. The system's modulation transfer function (MTF) and corresponding point spread function (PSF) are characterized by analyzing the contrast visibility of periodic structures of a star pattern featuring line width from 150 nm to 1.5 μm. The results, which can be attributed to the characteristics of the source spot, are crosschecked by scanning the source's electron focus over an edge of the structured transmission target in order to obtain an independent measurement of its point spread function. For frequencies above 1000 linepairs/mm, the MTF is found to correspond to a Gaussian PSF of 250 nm full width at half maximum (FWHM). The lower frequency range down to 340 linepairs/mm shows an additional Gaussian contribution of 1 μm FWHM. The resulting resolution ranges at 3200 linepairs/mm, which is consistent with the visual detectability of the smallest 150 nm structures within the imaged star pattern.

Laboratory-Based Nano-Computed Tomography and Examples of Its Application in the Field of Materials Research

“…According to the specifications, it achieves a 300 nm FWHM electron spot at 200 mW target. This information is consistent with our own investigations [31]. The source features an internal validation of the actual electron spot size as a measure of the achievable resolution.…”

“…For this purpose, the focus of the electron beam was manually scanned over edges on the patterned transmission target, to obtain an independent measure of the source point spread function by evaluating the radiation intensity measured in this process. For a more detailed description of the method, please refer to the previous study indicated [31]. For the visible resolution, which corresponds to the 10% MTF level, 3200 lp/mm is achieved with the high-resolution portion (narrow PSF).…”

“…2D MTF graph derived from the Siemens star image. As the electron spot in the source can be approximately described by the superposition of a narrow and a wide focal spot, the MTF is also composed of a high-frequency contribution (corresponding to 250 nm point spread FWHM) and a low-frequency background share (corresponding to 1.1 µm point spread FWHM)[31].…”

Development of Fibrous SF/PCL Tympanic Membrane Scaffolds via Electrospinning: Modeling and Experimental Verification

“…1 (2) displays the distribution of the pore size of a PCL membrane. The maximum pore diameter is about 13 µm and the maximum pore volume is 530 µm 3 . Process parameters of electrospinning like voltage or working distance seem to have only a minor influence on the porosity of the SF/PCL membranes.…”

“…In this study, a modeling based technique combining the electrospinning process, the nano-/microscale fiber structure and macroscale acousto-mechanical properties of scaffolds was applied. The electrospun SF/PCL fibrous membranes were scanned with the noval ntCT nano-tomography system [3], exploiting phase contrast at a spatial resolution of 250 nm and 60 KeV acceleration voltage. As shown in Fig.…”