Both laboratory and synchrotron-based microanalytical techniques (e.g. microXRF, microXRD, x-ray microscopy, SAXS, etc.) have made substantial advances in the past decades, including improved algorithms and faster, higher sensitivity detectors. However, laboratory performance remains comparatively limited in performance (e.g. sensitivity and resolution), primarily due to limited laboratory x-ray source brightness and narrow selection of usable x-ray optics.
Here we present our patented x-ray source concept. Coupled with our proprietary high efficiency x-ray optics, the system provides over 50X brightness over a conventional x-ray illumination beam system comprised of a microfocus source and polycapillary optic. The brightness is enabled by the design of the x-ray targets, which are comprised of microstructured x-ray emitters in thermal contact with a diamond substrate. Utilization of a diamond substrate enables highly localized and large thermal gradients that rapidly cool the metal as x-rays and heat are generated under the bombardment of electrons.
In addition to brightness, the spectral output of the x-ray source, particularly the characteristic lines, is sometimes indeed more important than brightness alone. For example, fluorescence cross-sections can vary by several orders of magnitude depending on the characteristic energy employed. Throughput and contrast of x-ray imaging and microscopy are also highly dependent on x-ray energy. Because characteristic lines can be the dominant spectral output for some metals, the ability to select and change metal types within an x-ray source provides substantial performance advantages. Sigray’s x-ray source incorporates several choices of metals on its x-ray target for push-button energy selectability within the x-ray source. A turret of Sigray’s interchangeable x-ray optics that are optimized for highest efficiencies at these energies can be coupled to provide the optimal flux and spectrum for each application.
The past decade has witnessed tremendous growth in both interest and available techniques for laboratory X-ray analysis. From the progression of commercially-available micro- and nano-CT scanners to the resolution and sensitivity enhancements of x-ray fluorescence spectrometers, the scientific community is benefiting from a rapid expansion of laboratory-based x-ray techniques.
In our work, we have developed a suite of advanced x-ray instrumentation providing a wide range of enhanced capabilities for specimen characterization. The key enabling technology lies in the X-ray source, which features a microstructured target capable of providing 5-10x higher brightness than conventional sealed-tube x-ray sources and offering power flux densities that rival rotating anode sources. The target array can be custom-designed to incorporate a variety of materials, facilitating fast & easy switching between characteristic emission lines and radiation spectra. This source has been subsequently integrated with state-of-the-art X-ray focusing optics, such as ellipsoidal/paraboloidal capillary lenses and finely-structured Fresnel zone plate imaging objective lenses, and sensitive scintillator-coupled CCD detection systems, opening up new opportunities for advancing laboratory x-ray inspection equipment.
Here, we will describe the system geometries in detail and demonstrate how these new advancements have led us to the development of laboratory micro-XRF, nano-XRM, and XAS instrumentation. We will also briefly introduce the image-centric software workspace, which facilitates novice users to collect data quickly and reliably with minimal training overhead.
Sigray’s axially symmetric x-ray optics enable advanced microanalytical capabilities for focusing x-rays to microns-scale to submicron spot sizes, which can potentially unlock many avenues for laboratory micro-analysis. The design of these optics allows submicron spot sizes even at low x-ray energies, enabling research into low atomic number elements and allows increased sensitivity of grazing incidence measurements and surface analysis. We will discuss advances made in the fabrication of these double paraboloidal mirror lenses designed for use in laboratory x-ray applications. We will additionally present results from as-built paraboloids, including surface figure error and focal spot size achieved to-date.