Polycapillary and doubly curved crystal (DCC) optics coupled with small spot x-ray sources in a special X-Beam package provide compact, high-sensitivity, low-power, highly stable subsystems that can be used for in situ analyzers. These analyzers provide remote, unattended use for environmental applications, bench-top or in-line instruments for industrial applications, and point-of-care clinical instruments for medical diagnosis or monitoring. Micro x-ray fluorescence (μXRF) and monochromatic micro x-ray fluorescence (MμXRF) can be used to measure trace element concentrations and distributions. Parallel-beam and convergent-beam x-ray diffraction (XRD) can be used for in situ phase composition, texture, strain, and crystal structure measurements.
Polycapillary x-ray optics are bundles of micron size hollow tubes, inside of which x rays are propagated by total reflection much like visible light in solid fiber optics. The small critical angle for total reflection from the glass walls of the tubes, 0.06° at 27 keV, results in very high angular selectivity. The field of view of each capillary tube is limited by this angular acceptance to less than 50 microns at a source-to-optic distance of 2 cm. Each adjacent tube works in parallel so that a large area can be covered at this resolution with much higher count rate than for a single collimator. Measurements have been performed using 125I brachytherapy seeds in Lucite phantoms using the optics and imaging detectors. Measured resolutions were detector-limited at better than 0.1 mm. Calculations for expected sensitivity and signal-to-background ratios were developed from geometrical models and show good agreement with measurements. Results indicate that the optics provide superior signal count rates to conventional collimators for geometries such as small animal imaging in which sub millimeter resolution with inch-wide or larger fields of view are desirable.
Three dimensional focusing of characteristic x-rays can be achieved by diffraction from doubly curved crystals (DCC). A focused beam total reflection x-ray fluorescence technique was developed based on these optics. This technique provides good detection sensitivity and spatial resolution for localized detection of surface deposits. Compact low power small spot x-ray sources were used to demonstrate the benefit of the x-ray optics for focusing Cr Kα, Cu Kα and Mo Kα radiation.
The DCC optic was also applied to monochromatic micro x-ray fluorescence (MMXRF), providing good detection sensitivity and spatial resolution for deeper impurities. The detection capability of the focused beam TXRF and MMXRF systems was investigated with dried droplets of calibrated low concentration solutions.
Additionally, the implementation of high contrast monochromatic imaging with a very low power source was demonstrated using the DCC optics at mammographic energies. Images of contrast phantoms were obtained with high clarity.
Applications of neutron diffraction for small samples (<1mm3) or small fiducial areas are limited by the
available neutron flux density. Recent demonstrations of convergent beam electron and x-ray diffraction and focusing of cold (λ>1 Å) neutrons suggest the possibility to use convergent beam neutron diffraction for small sample crystallography. We have carried out a systematic study of diffraction of both monoenergetic and broad bandwidth
neutrons at the NIST Research Reactor and at the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory. Combining convergent beams with time-of-flight Laue diffraction is particularly attractive for high efficiency small sample diffraction studies. We have studied single crystal and powder diffraction of neutrons with convergence angles as large as 15° and have observed diffracted peak intensity gains greater than 20. The convergent beam method (CBM) shows promise for crystallography on small samples of small to medium size molecules (potentially even for proteins), ultra-high pressure samples, and for mapping of strain and texture distributions in larger samples.
The relatively low flux from neutron sources means that structural analysis using neutron diffraction requires large crystals that are often not available.We are exploring the possibilities of a polycapillary focusing optic to produce a small intense beam spot of size ⪅0.5 mm for small crystals.We have conducted measurements at five different thermal neutron wavelengths to determine the transmission characteristics of a tapered monolithic focusing lens with a focal length of 100 mm,suitable for time-of-flight diffraction.Both the width of the focused beam and the intensity gain of the optic increase as a function of wavelength.We have performed similar measurements on a polychromatic beam on a pulsed neutron source,where the results are subject to background from short wavelength neutrons.The use of a beryllium filter shows the increased effective gain for the longer wavelengths at the expense of an increased focused beam width by a factor of two.In a diffraction measurement from an alpha quartz crystal using a 2.1° convergent beam from a pulsed neutron source,we observed six diffraction peaks in the 1.5 Å -4 Å wavelength bandwidth transmitted by the optic.These diffraction spots show an intensity gain of 5.8 ±0.9 compared to a direct beam diffracting from the same sample volume as that illuminated by the convergent beam.
X rays emitted over a large angular range from conventional, laboratory-based sources can be transformed into a parallel beam or focused onto a small sample area to give efficient utilization of small sources for powder diffraction. For optimal system design, it is important that source parameters be well characterized. Source to window distance, spot size, intensity, and uniformity were measured for an Oxford Ultrabright Molybdenum source. Two polycapillary optics, a weakly focusing, and a collimating, optic were also characterized in detail. Measurements of x-ray diffraction data have been assessed for silicon and organic powders, and agree well with parameters predicted from the source and lens characterization.
This paper is about the beam divergences of polycapillary optics. The definitions and measurement methods of polycapillary optics beam local divergence and global divergence are given. Factors like source spot size, optic input focal distance etc. for determining the beam local divergences are analyzed. Some simulation and experimental results for the polycapillary optics, which are used for X-ray diffraction and X-ray lithography, will also be presented.
The potential use of polycapillary optics could provide extraordinarily high spatial resolution imaging of radioactive sources for a new generation of gamma cameras is being investigated. A series of images from 125I brachytherapy seeds in Lucite phantoms display resolution better than 0.1 mm and signal to noise ratios in excess of a factor of 10. Such "cellular" level resolution might allow early stage location of prostate tumors, and be used to study their size, shape, and rate of growth. Even before being developed into the compact size needed for transrectal investigation of prostate cancer, imaging detectors using such high spatial resolution polycapillary angular filters may be valuable for small animal model studies and other research.
In this paper, we describe a low power system using Polycapillary collimating and focusing optics that were designed to collect Cu Ka radiation from an Oxford Ultra-Bright micro-focus source for X-ray powder diffraction measurements. The characterizations of the source and polycapillary optics are presented. A collimator with two apertures was used to block high energy X-rays. An optic alignment system was designed to optimize coupling between the optics and the source, taking into account the maximum radiation direction from the source. Several powder sample data sets were collected with this system and their qualities are compared with data sets from the same samples taken with an Enraf-Nonius FR590 sealed-tube source system. Discussion is also presented for further improving the performance of this low power system.
Polycapillary and doubly curved crystal x-ray optics have gained broad acceptance and are now being used in a wide variety of applications. Beginning as optics integrated into research setups, they were then used to enhance the performance of existing x-ray analytical instruments and are now widely used as essential components in x-ray spectrometers and diffractometers designed to utilize their capabilities. Development of compact x-ray sources, matched to the optic input requirements have allowed large reduction in the size, power, and weight of x-ray systems which are now resulting in development of compact x-ray instruments for portable, remote, or in-line analytical tools for new applications in industry, science, or medicine.
Polycapillary x-ray optics provide an innovative new way to control x-ray beams. Placing these optics after the object to be imaged provides very efficient rejection of Compton scatter, while allowing image magnification without loss of resolution, image demagnification, or image shaping to match with digital detectors. An extensive study of the effects of surface and profile defects have greatly enhanced the understanding of the manufacturing process and lead to improved reproducibility and manufacturability of the optics. Measurements were performed on magnifying tapers. The optics had measured primary transmissions greater than 50% and scatter transmission of less than 1%. For a 5-cm thick Lucite phantom, this resulted in a contrast enhancement compared to a conventional grid of nearly a factor of two. The magnification from the tapered capillary optics improved the MTF at all frequencies out to 1.9 times the original system resolution. Increases below the system resolution are most important because clinically relevant structures generally occupy lower spatial frequencies. Alternatively, placing a collimating optic and diffracting crystal before the patient provides sufficient monochromatic beam intensity for medical imaging. Contrast, resolution, and intensity measurements were performed with both high and low angular acceptance crystals. At 8 keV, contrast enhancement was a factor of 5 relative to the polychromatic case, in good agreement with theoretical values. At 17.5 keV, monochromatic subject contrast was more than a factor of 2 times greater than the conventional polychromatic contrast. An additional factor of two increase in contrast is expected from the removal of scatter obtained from using the air gap which is allowable from the parallel beam. The measured angular resolution after the crystal was 0.4 mrad for a silicon crystal. The realization of these applications has been advanced by the recent marked improvement in available optic quality and reproducibility. Manufacturing progress has been assisted by the development of simulation analyses which allow for increasingly accurate assessment of optics defects. Optics performance over the whole range of energy from 10 to 80 keV can often be matched with one or two fitting parameters. Continuing optics manufacturing challenges include the advance of applications at energies above 40 keV and the production of optics for imaging which are of adequate clinical size. Multioptic jigs designed to increase imaging area have been tested.
Polycapillary optics are shaped arrays of tiny hollow tubes through which x rays are guided by total external reflection at grazing incidence. Optics could be used prepatient, to shape the beam, or post patient, as scatter rejection grids. Significant resolution and contrast enhancement have been previously demonstrated at mammographic and lower energies for post patient optics. Measurements were performed to investigate the application of polycapillary post patient optics at higher energies. Measurement of contrast enhancement was performed using a small tapered optic. This tapered optic was designed to be placed into a multiple taper jig to create a large area device. The transmission of the taper was 71% at 20 keV and close to 30% at 40 keV. The scatter transmission of the taper, measured using a 6 cm thick polyethylene phantom, was about 1% at 40 keV. Because of the removal of scatter radiation, the measured contrast enhancement for the optic was a nearly factor of three at 40 keV.
Many medical imaging and industrial applications for x rays require large area optics with good scatter rejection. Preliminary scatter rejection and contrast measurements show that a prototype long borosilicate optic increases the contrast by a factor of 1.7 by decreasing the scatter transmission nearly a factor of 10 at 20 keV. Since borosilicate optics have higher scatter transmissions at high energies, the optics have to be fairly long to give good scatter rejection at high energies. However, long optics are complex to manufacture and have increased defect rates. Lead glass would allow the optic to be much shorter and still give good contrast enhancement, because of the superior absorption of leaded glass. In order to investigate the feasibility of using leaded glass polycapillary optics for these applications, measurements and simulations have been performed on the behavior of leaded glass polycapillary fibers in the 9 - 80 keV energy range.
This paper describes the design and performance of a low power protein crystallography system using polycapillary optics. The characterization of the source and polycapillary optics are presented. Three optic types: collimating, slightly focusing and strongly focusing optics have been used in low power source-optic combination systems. The source-collimating optic and source- slightly focusing optic systems were used to collect data sets for chicken egg-white Lysozyme with conventional sample oscillation during data collection. The data sets show high quality by analysis with a conventional software package, DENZO. Still diffraction patterns without oscillation have also been obtained by a low power source-strongly focusing optic combination. These patterns have been analyzed by developing software for processing diffraction patterns obtained with strongly convergent X-ray beams. The directions of future work and system improvements are also discussed.
Polycapillary fibers and a prototype collector for high energy x rays with a 2 m focal length have been fabricated and characterized. Measurements of a prototype collector, performed in collimating mode, show that the optic has high transmission, good uniformity, and small exit divergence. The transmission as a function of energy was analyzed using an extended single fiber geometrical optic simulation and the result shows that the simulation fits the data fairly well. Scatter transmission and contrast enhancement were measured in focusing mode using a parallel beam input.
Polycapillary collimating optics collect x rays produced by a point source over a wide solid angle (as large as 10 - 15 degrees cone angle) and a large energy bandwidth, and provide a quasi-parallel beam with a small divergence (a few milliradians). These optics are emerging as important tools in materials analysis, medical imaging, x-ray lithography and protein crystallography. Results of measurements carried out on three multi-fiber polycapillary x-ray collimating optics are described. Parameters influencing efficient employment of these optics, such as transmission versus photon energy, output beam uniformity, and divergence are characterized. Monte Carlo simulations based on ray-tracing geometrical optics are compared with experimental performances to extract additional information.
Polycapillary optics are shaped arrays of tiny hollow tubes through which x rays are guided by total external reflection at grazing incidence. In previous work, it has been demonstrated that a small prototype optic can provide nearly total scatter rejection at mammographic energies with simultaneous resolution enhancement due to geometrical-blur- free magnification. Recent measurements on straight capillaries and lenses show that capillary optics could possibly be applied to higher energy imaging applications, such as angiography and chest radiography. Transmission efficiency for straight bundles was measured to be fairly flat out to 60 keV and in excess of 30% at 80 keV. Extensive simulations and measurements have been performed for prototype capillary optics at photon energies from 20 to 100 keV. Transmission of the central part (0.5 mm diameter) of a 166 mm long prototype tapered lens was as high as 60% near 30 keV and in excess of 40% up to 70 keV. The reduction of transmission at high energies was found to be caused by optic profile defects: surface waviness and centerline bending. Absorption and scatter rejection measurements indicate that almost total scatter rejection is achievable at high energies. Scatter transmission of the tapered borosilicate glass lens is around 5% at 60 keV. Even better scatter rejection could be achieved by using lead glass capillaries. By estimating the contrast improvement factor and Signal to Noise Ratio (SNR) with the scaled up lenses, this paper demonstrates the potential for polycapillary optics in various medical x-ray imaging applications.
Polycapillary optics, shaped arrays consisting of hundreds of thousands of hollow glass capillary tubes, can be used to redirect, collimate, or focus x-ray and low energy neutron beams. X rays emitted over a large angular range from conventional, laboratory-based sources can be transformed into a beam with a small angular divergence or focused onto a small sample or sample area. Focused spot sizes as small as 20 micrometer have been achieved, with flux densities more than two orders of magnitude larger than that produced by pinhole collimation. This results in a comparable decrease in data collection times due to the increase in direct beam intensity and reciprocal space coverage. In addition, the optics can be employed to reduce background and provide more convenient alignment geometries. The inverse dependence of the critical angle for total external reflection on photon energy results in suppression of high energy photons. This effect can be employed to allow the use of higher tube potentials to increase characteristic line emission. Using parallel beam geometries peak shapes are found to be symmetric and independent of angle and sample alignment. Measurements of x- ray diffraction data and crystallographic analysis have been assessed for powders, thin films, minerals, elemental crystals, polymers, and protein crystals.The benefits and limitations of polycapillary optics for such measurements will be reviewed.
Polycapillary x-ray optics, arrays of hollow capillary tubes used to guide x-rays by total reflectance, are now being used in increasing numbers of applications, such as materials analysis, microelectronics manufacturing, x-ray astronomy and medical imaging. Because each optic contains hundreds of thousands of precisely shaped and located hollow channels, it is desirable to assess the feasibility of a variety of capillary geometries for a new application without physically constructing the optic. This assessment requires increasingly sophisticated modeling capability as new applications with more stringent requirements are developed. Previous analysis has shown that high-energy applications such as hard x-ray astronomy and medical imaging are particularly sensitive to optic profile errors such as channel waviness. A more physical model for surface waviness has been developed and included in optics simulations. The results are compared to measured data and to the results of other numerical simulation programs.
A prototype capillary optical system has been developed to further test the possible use of polycapillary optics for a hard x-ray spectrometer for astrophysical applications. It has been evaluated both as a concentrator and a collimator of x-rays with energies between 10 and 60 keV. Transmission efficiency, angular acceptance and focal spot size have been measured. Both experiment and simulation results for the prototype optic have demonstrated the potential of x-ray polycapillary optics for astrophysical applications. Further design and fabrication improvements indicated by prototype studies are discussed.
Polycapillary X-ray optics, which is comprised of bundles of tens of thousands to millions of hollow glass capillary tubes, can be used as concentrators of astronomical X-rays for spectroscopic studies. Measurements have been performed of transmission efficiency of straight polycapillary fibers in the range of 10-80 keV. A geometrical optics simulation has been developed which accurately models experimental results and includes the effects of surface roughness and profile error. An optic designed for 8-keV photons has been tested as a concentrator for parallel beam synchrotron radiation. The results, a factor of 65 in intensity gain, are in good agreement with optics simulation. A prototype optic designed for 10-50 keV is currently under construction with a predicted gain of more than 100. Design requirements for higher energy photons are considered. By using a small or position sensitive detector, improvements of two orders of magnitude at 80 keV are expected from the use of this type of collector.
Measurements have been performed on a prototype CdZnTe linear array designed for direct digital mammography. Direct detection of x-ray photons without conversion to visible light avoids the trade-off between resolution and efficiency with phosphor thickness inherent in the conversion process. Polycapillary x-ray optics can be used to shape the x-ray image in a manner similar to the use of fused fiber optic tapers with visible light. The polycapillary optics also provide significant scatter rejection and resultant contrast enhancement. The theoretical detector quantum efficiency of CdZnTe at mammographic energies (20 keV) is quite high. Measurements were performed of DQE values and uniformity from 13 - 256 keV in large single pixel detectors. Uniformity and imaging measurements were also performed on a prototype 1 cm long linear detector array with 50 micrometer pixels attached to read-out electronics using indium bump bonding technology.
A monolithic polycapillary focusing optic, consisting of hundreds of thousands of small tapered glass capillaries, can collect a large solid angle of x-rays from a point source and guide then through the capillaries by multiple total reflections to form an intense focused beam. Such a focused beam has many applications in microbeam x-ray fluorescence (MXRF) analysis. Two monolithic polycapillary focusing optics were tested and characterized in a MXRF set- up using a microfocusing x-ray source. For the CuK(alpha ) line, the measured focal spot sizes of these optics were 105 micrometers and 43 micrometers full-width-half-maximum, respectively. When the source was operated at 16W, the average CuK(alpha ) intensities over the focal spots were measured to be 2.5 X 104 photons/s/micrometers2 and 8.9 X 104 photons/s/micrometers2, respectively. When we compared the monolithic optics to straight monocapillary optics with approximately the same output beam sizes, intensity gains of 16 and 44 were obtained. The optics were applied to the MXRF set-up to analyze trace elements in various samples and a minimum detection limit of about 2 pg was achieved for the transition elements (V, Cr, Mn, and Fe). The optics were also used to map the distributions of trace elements in various samples.
Recent developments in the design, fabrication and applications of polycapillary optics for x-rays and neutrons have produced impressive new results and possibilities. These include x-ray and neutron probe measurements; diffraction based structural analysis of thin metal and magnetic films, powders, and protein crystals; x-ray lithographic patterning of integrated electronics and microstructures; and materials and medical imaging applications. Advances in the understanding, control, and reproducibility of fabrication parameters along with recent commercial availability of these optics have increased their accessibility and broadened their application base. This will likely lead to the incorporation of polycapillary optic components in a variety of commercial x-ray and neutron analysis systems. Expansion of the effective x-ray energy range downward to 0.3 and upward to 80 keV opens new possibilities, especially for medical and astronomical applications. Quantitative agreement between computer simulations and observed properties of both individual capillaries and complete lens structures provides not only a reliable basis for design of custom optics for a particular source or application, but also provides a firm basis for defining the limitations of polycapillary optics. The broad range of demonstrated applications, as well as limitations and prospects for polycapillary optics will be discussed.
A geometrical optics simulation program which includes roughness and waviness effects has been developed to analyze the performance of polycapillary x-ray optics in the energy regime 10-80 keV. The simulation was in excellent agreement with previous experimental results. The calculations showed that low energy x-ray performance is sensitive to roughness while high energy x-ray performance is affected by waviness and profile error (bending). Despite the low critical angle for total external reflection at high energies, capillary x- ray optics appear promising for many hard x-ray applications. Transmission measurements at high energies have also proven to be a very sensitive tool in capillary quality analysis.
Polycapillary x-ray optics have found potential application in many different fields, including antiscatter and magnification in mammography, radiography, x-ray fluorescence, x-ray lithography, and x-ray diffraction techniques. In x-ray diffraction, an optic is used to collect divergent x-rays from a point source and redirect them into a quasi-parallel, or slightly focused beam. Monolithic polycapillary optics have been developed recently for macromolecular crystallography and have already shown considerable gains in diffracted beam intensity over pinhole collimation. Development is being pursued through a series of simulations and prototype optics. Many improvements have been made over the stage I prototype reported previously, which include better control over the manufacturing process, reducing the diameter of the output beam, and addition of a slight focusing at the output of the optic to further increase x-ray flux at the sample. We report the characteristics and performance of the stage I and stage II optics.
Achieving the goals set by the US National Semiconductor Roadmap requires that sub 0.18 micrometers design rules be incorporated into semiconductor device structures by the year 2001. A promising approach makes use of shorter wavelength radiation than is presently used in lithography, namely x-rays. Arrays of glass fibers have the potential of controlling parameters important to point-source lithogrpahy including local divergence, global divergence, and field uniformity. The high absorption rate and scattering of x-rays in air at energies less than 3 keV necessitates that experiments must be conducted in an evacuated environment. Consequently, there has been little research on the transmission of x-rays through glass polycapillary fibers at energies of 3 keV and lower. An experimental setup to test capillaries under such conditions has been developed at XOS. It has sufficiently long optical paths in the vacuum chamber to be useful in evaluating the parameters critical for semiconductor lithography. Experimental and simulated transmission characteristics of polycapillary fibers as well as a discussion on the feasibility of using them in a collimator for x-ray lithography are presented in this paper.
A multifiber collimating lens designed to collect divergent Cu-K(alpha) x-rays over an 8.6 degree angle has been tested in a standard diffraction geometry. The lens was first characterized with a small (0.30 mm diameter) spot source and found to have transmission efficiency of 27%, output divergence of 0.22 degrees, and input focal spot size in the transverse and axial directions of 0.71 mm and 14.7 mm (FWHM), respectively. The lens was then tested with a standard rotating anode diffraction system for a variety of thin film structure and stress analyses. The measured data are compared to thoses obtained from a fixed tube parafocusing Bragg-Brentano geometry system. The effect of the lens on measurement efficiency was found to depend on the specific application, ranging from no benefit for small area (1.5 cm diameter) films to as much as 8.4 X computed gain in efficiency for highly textured films with finite-size broadened reflections. Typical efficiency gains for the same power and angular resolution were about 3.2 X. In general, the parallel beam geometry provided by the lens was more convenient then the Bragg-Brentano geometry because of reduced sample displacement and general defocusing errors. Since the lens was simply incorporated into systems optimized for non-lens measurements, it is felt that further diameter exceeded that of the soller slit, monochromator crystal, and detector. The geometric gain of the lens with respect to a pinhole with the same resolution is 74 for a line source in the point focus geometry and 159 for a point source. Incorporating straight capillary bundles as soller slits could provide a better match than traditional soller slits to diffraction system using a capillary lens and they may also be beneficial in reducing x-ray diffraction background. Optimization and other aspects of the use of the capillary lens in 'real world' analysis applications will be discussed.
Several applications of Kumakhov polycapillary optics require extended exposure to intense x- ray radiation. No degradation of performance has been observed when using polycapillary x- ray optics with laboratory sources. As part of an ongoing study to develop an understanding of damage mechanisms and performance limitations, borosilicate glass polycapillaries have been exposed to white beam bending magnet synchrotron radiation with peak energies of 5 and 11 keV, and focused broad band energy centered at 1.4 keV synchrotron radiation. In situ and ex situ measurements of degradation of x-ray transport efficiency have been performed at doses up to 1.8 MJ/cm2 at ambient and elevated temperatures. No decrease in transmission was observed for in situ measurement of fibers exposed to 1.4 keV photons at doses up to 1.4 MJ/cm2. Ambient temperature exposure to higher photon energies causes degradation that can be recovered by low temperature annealing. Exposure at elevated temperatures prevented any measurable damage to rigid fibers, at doses up to 800 kj/cm2.
Medical imaging was one of the earliest applications of x radiation and remains one of the most common and most important. Despite the advent of ultrasound and magnetic resonance imaging, x-ray imaging is still the most widely used medical imaging modality. Its low cost and ease of use are critical for mass screening, for example in cancer detection. The recent invention of Kumakhov polycapillary x-ray optics allows for a new mechanism of control of broadband x-ray radiation for imaging. Polycapillary x-ray optics provide nearly complete scatter rejection, and can be used to magnify or demagnify the x-ray image without conversion to visible photons. Measurements have been made of the performance of prototype magnifying antiscatter optics. Significant contrast enhancement and resolution improvement have been measured. The potential application of polycapillary optics to focused beam therapy is also discussed.
Charge Injection Device (CID) array detectors are well suited for the direct imaging with x- ray and particle beams. In common with CCD detectors, CID arrays have been shown to have good spatial resolution and broad spectral response in the visible range. In addition, CID imagers offer unique architectural features which may be particularly applicable to x-ray and particle beams, including exceptionally large pixel charge capacity, non-destructive pixel readout, and random pixel addressibility. These can dramatically extend the dynamic range, eliminate blooming effects, allow monitoring and dynamic adaptation of application exposure in real-time, improve signal-to-noise by repeated readout and permit the readout of small pixel sub-arrays at exceptionally fast rates. In addition CIDs possess extremely good radiation tolerance. Preliminary results of x-ray measurements with CIDs are presented along with a discussion of potential applications utilizing their unique features.
The Center for X-Ray Optics at the University at Albany, New York founded to pursue the development of capillary x-ray and neutron optics, has grown rapidly since its establishment less than four years ago. Quantitative characterization of these optics from 1 keV to 45 keV was reported here in 1993. In this report, a summary of the current status of this effort is described in the context of activities at the Center for X-Ray Optics.
One of the most attractive and potentially useful applications of capillary optics for x rays is conversion of divergent x rays from intense point sources into quasi parallel beams for diffraction applications. This is particularly important for investigation of small samples such as protein crystals. This report reviews the current status of development of monolithic tapered Kumakhov optics for protein structure analysis. Even at this early stage of development, gains of more than 30 compared to optimized systems without the optics have been achieved.
An x-ray lens designed to collimate x rays from a divergent source has been characterized. The lens is 10 cm long and consists of 919 polycapillary fibers. The diameter of each fiber is 400 microns with a channel size of 15 microns. The solid angle of collection of the lens is 40 msterad. The focal distance of the lens is 57 mm. The transmission and divergence properties of the lens are discussed for different x-ray energies and source conditions.
Since the recent invention by Kumakhov of polycapillary optics for the control of x-ray beams, a large number of potential applications have been identified. These include materials analysis techniques such as diffraction and microfluorescence, lithography, medical imaging applications such as angiography and mammography, and medical therapy. To develop and further identify these applications, precise knowledge is needed of the performance of a variety of capillary types for different source energies and geometries. Extensive measurements have been performed of transmission and exit divergence as a function of length, bend radius, x-ray source position, and x-ray energy (from 1 to 44 keV). X-ray source divergence was also varied; measurements were performed with point sources and synchrotron beams. The measurements were performed for a variety of polycapillary compositions, diameters, and geometries. In general, data agrees fairly well with Monte Carlo geometrical simulations.
Discovery that wide energy and angular control of x ray and neutron trajectories can be achieved with high efficiency by the use of shaped arrays of hollow capillaries has made possible important new applications in science, medicine, and industry. These include medical diagnostic imaging, medical therapy, analysis of the composition and structure of materials, x-ray microscopy, x-ray astronomy, industrial process and fault analysis, and x-ray lithography. The status and prospects for this remarkable range of possibilities is summarized in this report.
A system has been designed for concentration of an intense parallel beam of X-rays from a synchrotron. The system has two stages. The first stage consists of an array of tapered capillaries which decrease the beam cross section from 2 X 2 mm to about .05 mm and increase the beam divergence to near the critical angle. The second stage has a special asymmetric shape which decreases the beam cross section to 0.001 mm (1 micrometer) and increases the beam divergence to about 10 degrees. Although the optics have been optimized for 10 Kev X-rays, they should give substantial benefit over a range of X-ray energies from 5 - 20 Kev. The intensity gain is calculated to be between 5 X 103 and 105 depending on the transmission losses. The design parameters and the current experience with transmission measurements on prototype components will be reviewed. Questions relating to beam heating and radiation damage will also be discussed.