X-ray propagation through hollow channel: PolyCAD - a ray tracing code (1)

A new CAD program, PolyCAD, designed for X-ray photon tracing in polycapillary optics is described. To understand the PolyCAD code and its results, the theoretical basis of X-ray transmission by a single cylindrical channel (monocapillary) is discussed first. Then the simplest cases of cylindrically and conically shaped polycapillary optics are examined. PolyCAD allows any type of X-ray source to be used: an X-ray tube of finite beam dimensions or an astrophysical object can be simulated in combination with the polycapillary optics. The radiation distribution images formed on a screen located at various focal distances are discussed. The good agreement of some of the PolyCAD results with those reported in earlier papers validate the code. This is the first paper of a series dedicated to the development of an exhaustive CAD program, work is in progress to develop the code to include other polycapillary-optics shapes, such as semi-lenses and full-lenses.Comment: Submitted to Applied Optic

X-ray luminescence computed tomography using a focused X-ray beam

Due to the low X-ray photon utilization efficiency and low measurement sensitivity of the electron multiplying charge coupled device (EMCCD) camera setup, the collimator based narrow beam X-ray luminescence computed tomography (XLCT) usually requires a long measurement time. In this paper, we, for the first time, report a focused X-ray beam based XLCT imaging system with measurements by a single optical fiber bundle and a photomultiplier tube (PMT). An X-ray tube with a polycapillary lens was used to generate a focused X-ray beam whose X-ray photon density is 1200 times larger than a collimated X-ray beam. An optical fiber bundle was employed to collect and deliver the emitted photons on the phantom surface to the PMT. The total measurement time was reduced to 12.5 minutes. For numerical simulations of both single and six fiber bundle cases, we were able to reconstruct six targets successfully. For the phantom experiment, two targets with an edge-to-edge distance of 0.4 mm and a center-to-center distance of 0.8 mm were successfully reconstructed by the measurement setup with a single fiber bundle and a PMT.Comment: 39 Pages, 12 Figures, 2 Tables, In submission (under review) to JB

Quick X-ray Reflectivity using Monochromatic Synchrotron Radiation for Time-Resolved Applications

We describe and demonstrate a new technique for parallel collection of x-ray reflectivity data, compatible with monochromatic synchrotron radiation and flat substrates, and apply it to the in-situ observation of thin-film growth. The method employs a polycapillary x-ray optic to produce a converging fan of radiation incident onto a sample surface, and an area detector to simultaneously collect the XRR signal over an angular range matching that of the incident fan. Factors determining the range and instrumental resolution of the technique in reciprocal space, in addition to the signal-to-background ratio, are described in detail. Our particular implementation records $\sim$5\degree{} in $2\theta$ and resolves Kiessig fringes from samples with layer thicknesses ranging from 3 to 76 nm. Finally, we illustrate the value of this approach by showing in-situ XRR data obtained with 100 ms time resolution during the growth of epitaxial \ce{La_{0.7}Sr_{0.3}MnO3} on \ce{SrTiO3} by Pulsed Laser Deposition (PLD) at the Cornell High Energy Synchrotron Source (CHESS). Compared to prior methods for parallel XRR data collection, ours is the first method that is both sample-independent and compatible with highly collimated, monochromatic radiation typical of 3rd generation synchrotron sources. Further, our technique can be readily adapted for use with laboratory-based sources.Comment: Accepted in Journal of Synchrotron Radiatio

Confocal micro-XRF/XANES analysis on insects trapped in amber

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Spectral structure of a polycapillary lens shaped X-ray beam

Polycapillary X-ray optics is widely used in X-ray analysis techniques to create a small secondary source, for instance, or to deliver X-rays to the point of interest with minimum intensity losses [1]. The main characteristics of the analytical devices on its base are the size and divergence of the focused or translated beam. In this work, we used the photon-counting pixel detector ModuPIX to study the parameters for polycapillary focused X-ray tube radiation as well as the energy and spatial dependences of radiation at the focus. We have characterized the high-speed spectral camera ModuPIX, which is a single Timepix device with a fast parallel readout allowing up to 850 frames per second with 256•256 pixels and a 55 [mu]m pitch defined by the frame frequency. By means of the silicon monochromator the energy response function is measured in clustering mode by the energy scan over total X-ray tube spectrum

On X-Ray Waveguiding in Nanochannels: Channeling Formalism

The question on X-ray extreme focusing (smallest reachable spot size) brings us to the idea for using the wave features of X-ray propagation in media. As known, wave features are revealed at propagation in ultra-narrow collimators as well as at glancing reflection from smooth flat and/or strongly curved surfaces. All these phenomena can be described within the general formalism of X-ray channeling.Comment: by the invited lecture at ISRP-1