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 limitations to achievable x-ray brightness within the laboratory1 for x-ray spectra is a well-known problem for improving the throughput, sensitivity, and resolution of a wide variety of x-ray techniques. Specific examples of such challenges include: throughput in Talbot-Lau interferometry for medical applications, limits to sensitivity in micro x-ray fluorescence (microXRF), and resolution in x-ray microscopy.
We will present our patented x-ray source technology and recent developments. The major innovations in our x-ray source are the x-ray anodes, which are comprised of arrays of microstructured metal x-ray emitters embedded within a diamond substrate. The diamond substrate enables highly localized large thermal gradients that passively and rapidly cool the metal microstructures as heat is generated under the bombardment of electrons. Electron power densities, 4X higher than conventional solid metal targets can be achieved on the target even greater for metals of lower thermal conductivity. The thermal advantages of the anode design enables the use of many elements that were previously unsuitable as x-ray source materials, and will enable access to new x-ray characteristic lines to optimize performance in monochromatic x-ray analysis.
In addition, we will review practical benefits of our patented FAASTTM (fine array anode source technology) x-ray source over both conventional x-ray sources and newer schemes such as liquid metal anodes2. Advantages include the ability to produce a patterned microbeam optimized for Talbot-Lau interferometry (phase contrast imaging) and the ability to produce various characteristic lines through the incorporation of novel materials (e.g. Au, Pt, Cr) for dual energy capabilities.
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.
The permanent refractive index change induced by ultrashort laser pulses in zinc phosphate glasses has been investigated both at the surface and in bulk. At the sample surface, irradiations have been performed by using loosely focused single fs-laser pulses at different energies. Optical microscopy images of the irradiations illustrate an interferometric pattern in form of concentric Newton rings due to the laser induced multilayer system (unmodified glass, thin laser-modified layer, air). This experimental reflectivity modulation along with simulations based on Abeles theory for multilayer optical systems allows retrieving laser-induced refractive index changes on the order of Δns= -10-3. In bulk, fs-laser written waveguides have been generated by translating the sample with respect to a tightly focused laser beam. The so-produced waveguides have been characterized by studying the optical near field of the TEM00 guided mode at 660 nm and using white light microscopy. The optical changes linked to the inscribed waveguides have been characterized by measuring the far field output profiles yielding values of approximately Δnb= +3·10-4. The laser-modified optical properties in bulk and at the surface will be linked to the glass structural changes as well as discussed in terms of the role of the incubation effects for multi-pulse processing.
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