X-ray Transmission Properties Research Articles

Characterizing x-ray transmission through filters used in high energy density physics diagnostics.

We report on the design and implementation of a new system used to characterize the energy-dependent x-ray transmission curve, Θ(E), through filters used in high-energy density physics diagnostics. Using an Amptek X-123-CdTe x-ray spectrometer together with a partially depleted silicon surface barrier detector, both the energy spectrum and total emission of an x-ray source have been accurately measured. By coupling these detectors with a custom PROTO-XRD x-ray source with interchangeable cathodes, accurate characterizations of Θ(E) for filters of varying materials and thicknesses have been obtained. The validity of the technique has been confirmed by accurately reproducing areal densities for high-purity filters with known x-ray transmission properties. In this paper, the experimental setup is described and the results of absorption calibrations performed on a variety of different filters are presented.

Quantitative evaluation of transmission properties of breast tissue equivalent materials under Compton scatter imaging setup

To explore the potential of utilizing Compton scattered x-ray photons for imaging applications, it is critical to accurately evaluate scattered x-ray transmission properties of targeted tissue materials. In this study, scattered x-ray transmission of breast tissue equivalent phantoms was evaluated. Firstly, two validations were carried out using a primary x-ray beam at 80 kVp with both experimental measurement (ion chamber with narrow-beam setup) and analytical calculation (Spektr toolkit). The tungsten-anode x-ray spectrum model was thus validated by measuring and calculating the transmission through increasing thickness of 1100 Aluminum filters. Similarly, the composition models of breast tissue equivalent phantoms (CIRS, 012A) were validated by measuring and calculating x-ray transmission for three different breast compositions (BR30/70, BR50/50, and BR70/30). Following validation, transmission properties of Compton scattered x-ray photons were measured with a GOS based linear array detector at the 90° angle from the primary beam. The same study was performed through three independent approaches: experimental measurement, analytical calculation, and Monte Carlo simulation (GEANT4). For all three methods, the scattered x-ray photon transmission as functions of phantom thickness were determined and fit into exponential functions. The transmission curves from all three methods matched reasonably well, with a maximum difference of 6.3% for the estimated effective attenuation coefficients of the BR50/50 phantom. The relative difference among the three methods of estimated attenuation is under 3.5%. As an initial step to develop a novel Compton scatter-based breast imaging system, the quantitative results from this study paved a fundamental base for future work.

Theoretical Simulation of X-Ray Transmission Through a Polycapillary X-Ray Lens With a Variable Capillary Radius

This article presents a model for simulating the X-ray transmission properties of a polycapillary X-ray lens in which the capillaries are arranged in a layered hexagonal structure. Each layer consists of hexagonally shaped capillary bundles which are arranged symmetrically around a centerline, and the capillary radius varies with the layer. The transmission efficiency of X-rays in different layers is studied, and by designing the capillary radius, a uniform X-ray intensity distribution is generated at the output of the polycapillary parallel X-ray lens, which has remarkable differences with the distribution of a conventional polycapillary parallel X-ray lens. In addition, several common defects in the manufacturing process of the polycapillary lens are simulated.

The use of an advanced composite material as an alternative to carbon fibre in radiotherapy

Carbon fibre has become the material of choice for many radiotherapy accessories, as it is lightweight, radio-translucent and rigid. Unfortunately specialised equipment is required to manufacture devices from it and hence these tend to be expensive. Also carbon fibre is conducting which limits its compatibility with MRI. Other composite materials have now become available that are rigid and lightweight and may be equally radio-translucent. Here we describe the use, in radiotherapy, of such a composite made of polypropylene and fibre glass (PFGC) that is MRI compatible. We measured the 6 MV x-ray transmission and build-up properties of 2.5 cm thick panels made of either carbon fibre or PFGC. They are found to have equivalent x-ray transmission properties, varying from about 0.98 at perpendicular incidence to about 0.96 at 60° oblique incidence. The build-up dose was found to be approximately 82% of the maximum dose. We also demonstrate the use of PFGC as a flat couch top for MRI scanners and as a head board for shell immobilisation devices.

Statistical Characteristics of Transmitted Nano-meter Electromagnetic Waves in Random Bio-medical Tissues for X-Ray Diagnostic Images

Medical image diagnosis and computer aided diagnosis using X-rays are very im- portant technical tools for physiological diagnosis. Scattered X-ray flelds disturb medical image signal properties given by X-ray transmission properties through biological structures concerned with X-ray absorption efiects due to biological characteristics. In this paper, in order to improve image diagnosis, statistical analysis of X-ray is discussed for X-ray propagation, attenuation and scattering in random inhomogeneous biological media. Spatial flltering characteristics of grid structure for scattering X-rays particularly, for ofi-axis X-rays are shown for image X-ray projec- tion by mode theory of lossy waveguides for higher modes. Spatial grid fllters consist of waveguide arrays of graded index inhomogeneous waveguides.

X-ray transmission properties of intelligent anvils in diamond anvil cells

High-pressure and/or high-temperature analysis of geo- and material science samples routinely employs diamond anvil cells (DACs) as a research instrument. In particular, DACs allow for various in situ characterizations (e.g. Raman and Fourier transform infra red spectroscopies, X-ray diffraction (XRD), X-ray spectroscopy including fluorescence (XRF) and absorption (XAS)) at elevated pressure and temperature. The measurement of pressure (P) and/or temperature (T) in the sample chamber is crucial, but not always accurate, more specifically in the case of low-pressure applications (a few GPa). The development of modified diamonds (intelligent anvils ‘i-anvils’) adapted to a new generation of DACs (intelligent diamond anvil cells: iDAC) can contribute to solve this problem, as the diamond itself serves as the PT sensor, being prepared, for example, by high-energy ion implantation [H. Bureau, M. Burchard, S. Kubsky et al., This volume (2006).] on a micrometric scale. Several most interesting measurement methods used with DACs are based on X-ray techniques (e.g. XRF, XRD, XAS). We present the first results of X-ray transmission measurements with iDACs, performed at the hard-X-ray microfocus beamline ID22 at the ESRF (European Synchrotron Radiation Facility), Grenoble, France. Sensor response to intense irradiation as a function of X-ray energy (E ph∈10;18.1 keV) was investigated. The values of the sensor were found to be independent of the irradiation in the investigated energy range and thus validate the use of these sensors for precise and reliable measurements on a wide range of applications with high-energy synchrotron radiation. No influence of the sensor on the X-ray transmission properties of the anvil has been found.

The soft x-ray transmission properties of thin polyimide windows and their application to future detectors

The x-ray transmission properties of a very thin polyimide window in the range 7–310 Å have been investigated. The window is nominally 0.24 μm thick and is supported by a hexagonal polyimide grid. Transmission of over 60% and 80% at the oxygen Kα and carbon Kα lines, respectively, have been achieved. The use of such windows as the entrance window of a gas scintillation counter (GSPC) operating as a broadband spectrometer at XUV wavelengths is discussed. Overall detector efficiencies of greater than 10% for wavelengths less than 150 Å are possible to achieve.

Polyimide planarization for increased transmission of large-area X-ray windows

The substrate roughness has previously set the limit for the minimum thickness of X-ray windows based on technology where planar tungsten grids are used for the membrane support, because the window membrane is built directly onto the substrate. Here this restriction is precluded by using a planarizing layer on the foil combined with retarded etchstop removal, which allows further reduction in the membrane thickness. A polyimide resin has been selected for the planarizing film, which can be removed either by solvents or by plasma etching. The fabrication process presented is capable of producing pressure-enduring X-ray window membranes in large formats down to the membrane polyimide thickness of 250 nm. The fabrication procedures of the windows are presented in detail to correlate the observed behaviour to the window structure. The test windows prepared are analyzed by pressure endurance and leak measurements and their X-ray transmission properties are presented.

Comparison of ultrathin x-ray window designs

In order to fabricate entrance windows for soft x-ray detectors, various technologies have been developed. Depending on the x-ray-detector type and the environment in which the windows are used, entrance windows must meet several, often contradictory, requirements: while good pressure tolerance and durability as well as gas tightness require thicker structures, good x-ray transmission can only be achieved with thin membranes. In this paper, the suitability of different window types for various applications is discussed. The applicability discussion is based on the results of tests performed on prototype windows, as well as on calculated and measured x-ray transmission properties. A comparative study of endurance vs transmission properties of some candidate membrane materials is also presented. Test results include pressure tolerance and leakage rates as well as some measurements of radiation damage to the window materials. The window technologies presented include coated polyimide membranes with two different supporting schemes as well as submicrometer beryllium membranes.

On the X-ray transmission properties of multilayer windows

The X-ray transmission properties of the multilayer X-ray entrance window of the Low Energy Gas Scintillation Proportional Counter (LE-GSPC) being developed for the SAX X-ray Astronomy Satellite, were measured as a function of X-ray energy and position in the 100–1800 eV region using monochromatic synchrotron radiation. Particular attention was paid to avoiding interference effects with the fine grid and strongback, supporting the nominally 1.25 μm thick window. The window is made gas tight and atomic oxygen resistant by several Al/AlN multilayers. Since the layer thicknesses are comparable to the wavelengths of the X-ray region covered by the LE-GSPC, interference effects were not excluded a priori. The X-ray transmission revealed complex structures, particularly around the absorption edges. Such structures and observed position dependences demonstrate the necessity to calibrate these windows over a fine energy grid prior to their incorporation into any flight detector.

Comparison of Ultrathin X-Ray Window Designs

In order to fabricate entrance windows for soft x-ray detectors, various technologies have been developed. Depending on the x-ray-detector type and the environment in which the windows are used, entrance windows must meet several, often contradictory, requirements: while good pressure tolerance and durability as well as gas tightness require thicker structures, good x-ray transmission can only be achieved with thin membranes. In this paper, the suitability of different window types for various applications is discussed. The applicability discussion is based on the results of tests performed on prototype windows, as well as on calculated and measured x-ray transmission properties. A comparative study of endurance vs transmission properties of some candidate membrane materials is also presented. Test results include pressure tolerance and leakage rates as well as some measurements of radiation damage to the window materials. The window technologies presented include coated polyimide membranes with two different supporting schemes as well as submicrometer beryllium membranes.

Broad Beam Transmission Properties of Some Common Shielding Materials for Use in Diagnostic Radiology

Broad beam geometry was used to measure the x-ray transmission properties of gypsum wallboard, steel, plate glass, and concrete for x-ray tube potentials of 50-125 kVp using an x-ray generator having a three-phase, twelve-pulse waveform and total initial beam filtration sufficient to provide half-value layers representative of those found in common practice and required by regulatory agencies. Measurement results are presented graphically and as numerical fits to a mathematical model of broad beam transmission to permit their use in the design of protective barriers for medical diagnostic x-ray facilities.

X-ray Characterization of Thin Diamond Films Deposited by Hot-Filament Chemical Vapor Deposition

AbstractSynthesizing thin diamond films by chemical vapor deposition (CVD) is the most recent and technologically important development in the thin-film field. Thin diamond films are useful in many applications because of their unique physical, chemical, optical, and electronic properties.To assess thin diamond films’ suitability for support membranes in X-ray lithography, X-ray diffraction was used to characterize the crystal structure and orientation of these films deposited on silicon wafers by hot-filament assisted CVD. X-ray transmission properties of free-standing thin diamond films prepared by selectively etching silicon substrates were characterized by X-ray fluorescence in short and long wavelength regions.This paper discusses conventional and grazing incidence diffraction techniques used to study the crystal structure of thin diamond films and compares the results with film morphology. It also describes X-ray transmission properties of these films in terms of Beer's Law, the mass absorption coefficient, and the wavelength of attenuated radiation. Finally, it reveals the long wavelength regions for optimum X-ray lithography operations using polycrystalline diamond (PCD) film.