POLYCPILLARY OPTICS: AN ENABLING TECHNOLOGY FOR NEW APPLICATIONS

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1 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume POLYCPILLARY OPTICS: AN ENABLING TECHNOLOGY FOR NEW APPLICATIONS David Gibson and Walter Gibson X-Ray Optical Systems, Inc., 30 Corporate Circle, Albany, NY ABSTRACT Polycapillary optics have gained broad acceptance and now are being used in a wide variety of applications. Beginning as optics integrated into research setups, they then were 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 the optics capabilities. Development of compact X-ray sources, matched to the optic input requirements have allowed large reduction of 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 sensors for new applications in industry, science, or medicine. 1. INTRODUCTION Having undergone rapid development over the past ten years, polycapillary optics have gained broad acceptance. Indeed, this conference (DX-2001) marks an important transition in which the focus of papers and presentations are primarily or exclusively on applications and not on the design and characteristics of the optics. For example, in this conference there are over twenty papers that utilize polycapillary optics. In some cases, polycapillary optics enhance the sensitivity or improve the convenience of standard X-ray analysis equipment. An example is the use of a collimating optic into an X-ray diffractometer to produce a quasiparallel beam that increases the diffracted beam intensity and at the same time, simplifies alignment and alleviates sample position, roughness, shape, and transparency constraints. Furthermore, in an impressive number of cases, the effect of polycapillary optics is dramatic enough to enable entirely new applications, either by making new kinds of measurements possible or, more commonly, by reducing the size, power and cost enough to allow traditional laboratory or even synchrotron based measurements to migrate to in situ or on-line use in sample preparation or manufacturing environments. This paper will summarize such enabling studies and measurements by X- Ray Optical Systems (XOS) in collaboration with the Center for X-Ray Optics (CXO) at the University at Albany and a large number of other organizations and individuals History and overview of polycapillary optics The basic physics that underlies polycapillary X-ray optics was described in and the possibility to guide X-rays in hollow capillary tubes was discussed in The principles of operation of polycapillary optics are shown in Fig. 1. Optics using multiple channels each involving multiple reflections were first reported in These were comprised of single thin-walled glass capillary tubes guided through thin metal screens. A photo of one of the first focusing optics is shown in Fig. 2. This optic was nearly one meter long and, because of the limitations on the diameter of the capillary tubes (~ 350 µm), was designed for 1.5 kev X-rays. Indeed, the lowest energy X-rays that could make the long trip from the source to the detector because of absorption in the air was ~4 kev. Even so, this focusing optic showed a gain for 4 kev x-rays in the 0.8 mm focal spot, of ~2500 and for 8 kev X-rays a gain of ~400 (in part, the large gain is due to the long distance from the source to the focal spot which reduces the intensity without the optic due to the dependence of intensity on 1/D 2, where D is the distance from the source). The next major advance was the use of polycapillary fibers in which many hollow capillary channels were contained in a single glass fiber of about the same size as the original single glass capillaries 4. These polycapillary fibers were threaded through thin metal grids. Such multifiber polycapillary optics allowed significant reduction in size and increase of the useable X-ray energy. A photograph of such a multifiber optic and a cross section of a single fiber are shown in Fig. 3.

2 This document was presented at the Denver X-ray Conference (DXC) on Applications of X-ray Analysis. Sponsored by the International Centre for Diffraction Data (ICDD). This document is provided by ICDD in cooperation with the authors and presenters of the DXC for the express purpose of educating the scientific community. All copyrights for the document are retained by ICDD. Usage is restricted for the purposes of education and scientific research. DXC Website ICDD Website -

3 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume Figure 1. Schematic representation of the principles of capillary optics. 0, is the critical angle for total external reflection, R is the radius of curvature of the capillary and d is the capillary diameter. &!?L * L R~500 mm 0, =3.8mrad d< 5wrn Figure 2. Photograph of original Kumakhov focusing optic. Length is - 1 m and diameter is -200 mm. Figure 3. a) Multifiber polycapillary collimating optic. The length is -10 cm and The width is 2 cm. b) Polycapillary fiber. This example has -400,50 u.rn channels and is -600 pm flat-to=flat. More typical polycapillary fibers have -2000,5-10 pm channels and are -500 pm wide. A very important advance, development of monolithic polycapillary optics was announced in For both the original capillary optics and the multifiber polycapillary optics, the cross section of the individual hollow capillary channels is constant, For monolithic optics, however, the cross section of the channels changes along the length of the channels, as shown in Fig. 4. Photographs of monolithic optics are shown

4 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume in Fig. 5 and the microcapillary makeup of these optics are shown in Fig. 6. Note the dramatic size decrease (accompanied by an x-ray energy increase) compared to the early stage optic shown in Fig. 2. Figure 4. Collimating and focusing monolithic polycapillary optics. Figure 5. Photographs of bare and packaged mololithic optics. 5mm 300 µm 10 µm Figure 6. Photographs showing the microchannel makeup of monolithic polycapillary optics. Depending on the size, an optic may contain up to 2 million channels Optics Capabilities Capabilities of polycapillary optics are summarized in Table II and Table III. Only monolithic optics are shown in Table III since they can give focal spot sizes much smaller than multifiber focusing optics for which the spot size is limited by the polycapillary fiber width. In special cases, as for neutron focusing, multifiber focusing optics may be used because of their larger collecting area. Also multifiber collimating optics are often selected for applications requiring a large cross section parallel beam as for large area thin film texture studies 6 or X-ray lithography X-RAY BEAMS A principle benefit of polycapillary optics is the ability to capture X-rays from a divergent source over a large angle and to redirect them into a quasiparallel or focused X-ray beam, thus avoiding the inverse

5 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume square dependence of x-ray intensity on the distance from the source that has limited many applications of X-rays since their discovery over 100 years ago. A comparison between a polycapillary focusing optic and a conventional 0.1 mm pinhole aperture is shown in Fig Collimating Optics Multifiber Output beam size: 10 x 10, 20 x 20, 30 x 30 mm 2 Output divergence: ~ 4mrad Cu Kα Capture angle: 4.2, 7, 8.8 Axial and planar divergence are identical Up to 30 % transmission efficiency Monolithic Output beam size diameter: 0.5mm, 1.5mm, 4mm, 6mm Output divergence: ~1 mrad Mo Kα, ~2 mrad Cu Kα Capture angle: up to 20 Transmission efficiency: up to 30 % (geometry and energy dependent) Focusing Monolithic Optics Point to point focusing Small focal spots < 25 Cu Kα < 15 Mo Kα Capture angle: up to 20 Transmission efficiency: up to 30 % (geometry and energy dependent) Table II. Characteristics of collimating polycapillary optics. Table III. Characteristics of focusing polycapillary optics. Scatter x-ray spectra (W-anode, 30kV, 0.1mA) Figure 7. X-ray energy spectrum from 3 W tungsten x-ray source with polycapillary focusing optic and with conventional pinhole aperture (ref. 8). Counts Ar in air W Lα W Lβ W Lγ Polycapillary focusing optic 0.1 mm aperture 100 mm from the source Fe and Cr from the aperture material To overcome the traditional 1/D 2 limitation, high-power laboratory X-ray sources such Energy (kev) as rotating-anode sources (up to 18 kw), or laser-plasma sources have been developed. Desire for increased intensity has also motivated development of synchrotron or free-electron-laser (FEL) X-ray sources. Such sources, are large, expensive, and complex. For many applications polycapillary optics make use of such sources unnecessary. For polycapillary optics, the capture angle is limited by the angle subtended by the source at the input of the optic. This can be maximized for a given source-optic distance by making the optic input area large, which means using a multifiber lens for many standard X-ray sources which often have source-spot to window distance of several cm (the largest area monolithic optics with good performance at present is ~ 10 mm). However, with reduction of the source- optic distance to a few mm, even monolithic optics can have a large capture angle. In this case, it is important that the source spot size be small (<0.1 mm). Recently, several close-access, microfocus X-ray sources have been developed. When coupled with monolithic optics, X-ray flux and flux density values have been obtained with compact low-power sources that are comparable to or greater than those obtained with conventional high-power rotating anode sources equipped with modern confocal optics. An integrated source-optic system is shown in Fig. 8. By choice of optic, this can produce a quasiparallel beam or a focused beam. Table IV shows some examples of beam characteristics with focusing X-Ray Beams and Table V and Table VI with collimating X-Ray Beams.

6 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume With Cu-anode source (50 kv, 50W, source spot: 0.15 mm): Cu Kα intensity: photon/second Flux density: photon/s/µm 2 With Mo-anode source (50 kv, 50W, source spot: 0.15 mm): Mo Kα: photon/second Figure 8. X-ray Beam TM, with integrated optic alignment and Flux density: photon/s/µm 2 Table IV. Characteristics of X-ray Beam TM with shutter assembly. focusing monolithic optics (ref. 8). Table V. Collimating X-Ray Beam TM with Cu Kα source (ref. 8). Beam diameter 1.5 mm 6.0 mm Beam flux 1.9 x 10 9 p/s 40kV, 80W (Bede Microsource) 1.0 x 10 9 p/s 40 kv, 50W (Oxford 5011 source) Beam divergence (FWHM) 2.0 mrad. (0.12 ) 2.0 mrad. Beam diameter 1.0 mm 4.0 mm Beam flux at 50kV, 40W (Oxford UltraBright source) 7.1 x 10 7 p/s 3.5 x 10 8 p/s Table VI. Collimating X-Ray Beam TM with Mo Kα source (ref. 8). Beam divergence (FWHM) 1.0 mrad mrad. 3. APPLICATIONS 3.1. Focused beam applications Micro X-ray fluorescence (MXRF) 9 MXRF is currently the most widely used application of polycapillary optics, being an integral part of several commercial MXRF instruments. The small size and low power enables development of on-line MXRF sensors for semiconductor, pharmaceutical, and other materials based industries and development of remote or portable environmental and mineralogical (e.g. planetary rover) instruments. MXRF systems can take many different forms, some of which are illustrated in Figs Currently attainable focal spot sizes are listed in Table III.

7 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume Computer Si(Li) detector Motion controller XYZ Stages X-ray source Optic #1 Sample XYZ Stages Optic #2 XYZ Stages Figure 9. Standard MXRF configuration. Figure 10. Dual optic MXRF system. The sample can be scanned to measure the Particularly useful for special measurements of distribution with ~ 10 µm resolution. radioactive samples (ref 10). The compact size and flexibility of focused X-ray Beam systems facilitates their incorporation into existing processing or diagnostic instruments. An example is shown in Fig. 11. An interesting application in a low-voltage scanning electron microscope (LV-SEM) or environmental SEM (ESEM) is shown in Fig In this case the electron beam spreads in the high-pressure environmental chamber and fluorescent X-rays generated outside the area of interest get into the detector and reduce the image contrast. A polycapillary optic collects X-rays from an area defined by the optic spot size and focuses them on the detector, reducing the background and enhancing the image contrast. EDS Detector e - Sample chamber Spreaded e beam Polycapillary optic Specimen Specimen holder Figure 11. MXRF X-ray Beam Figure 12. Monolithic focusing optic as incorporated into an SEM. a spatial filter in an ESEM (ref. 11). High-resolution X-ray fluorescence measurements, not only greatly increase the elemental discrimination and measurement sensitivity but in some important cases can give chemical as well as compositional information. This can be done by wavelength dispersive detection with a collimating optic to increase the diffracted beam intensity as shown in Fig and Fig. 14 or by use of an ultra high resolution microcalorimeter detector as shown in Fig An example of the XRF spectrum from such a measurement is shown in Fig Other focused beam applications Other applications of polycapillary monolithic focusing optics, sometimes together with a collimating optic are; x-ray absorption fine structure (EXAFS or XAFS) as shown in Fig and x-ray absorption near edge spectroscopy (XANES) shown in Fig XAFS measures the local microstructure with atomic resolution and XANES measures the chemical state of selected constituents. These applications as

8 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume Flat Crystal Electron Beam,..I.~ Sample m Figure 13. Micro Wavelength Dispersive Figure 14. Electron Probe Wavelength X-ray Fluorescence (MWDXRF)(ref. 12) Dispersive Spectroscopy (EPWDS) Micro Calorimeter Detector Figure 15. Monolithic focusing optic to increase the efficiency (>300 x) of super conductor microcalorimeter detector (ref. 13). Figure 16. XRF spectrum from 0.5 pm WSiOZ particle on SiOZ substrate. (ref. 14) well as most of the other applications discussed in this section, make use of the broad energy (or wavelength) band-width accommodated by polycapillary optics. This distinguishes polycapillary optics from diffractive optics such as flat or curved crystal optics and multilayer thin film optics. Additional applications of focusing optics (not discussed in this review) include; focusing of low energy (cold) neutrons for prompt gamma activation analysis (PGAA)17 which gives measured neutron intensity gains as high as 80 and focal spot sizes as small as 90 pm, making neutron microanalysis possible for the first time, and concentration of high energy (20-50 kev) X-rays for astrophysical spectroscopic measurements *. Figure 17. X-ray absorption fine structure (XAFS). This arrangement gives high beam intensity and small beam size (< 0.1 mm)(ref. 15).

9 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume Figure 18. Setup for x-ray absorption near edge spectroscopy- µ XANES (ref. 17) Collimated beam applications Powder X-ray diffraction (Powder XRD) (phase analysis, stress-strain, texture). Collimating polycapillary optics increase the diffracted intensity ( X depending on the application). This is because they convert a highly divergent beam (up to 20 o depending on the capture angle) into a quasiparallel beam with divergence of 1-4 mradians as shown in Table II. The number (fraction) of X-rays diffracted from a crystal therefore greatly increases depending on the intrinsic (Darwin) width of the diffracting crystal. Fig. 19 shows the general arrangement for a phase, stress or texture measurement. And Fig 20 shows the change in diffracted beam intensity with a polycapillary collimator 19. Figure 19. General arrangement for X-ray diffraction (XRD) measurement (after ref. 6) Intensity cts/s 2KW Diffractometer cts/10s XOS Prototype System KW Parallel-Beam Diffractometer 20W XOS Prototype System Figure 20. Comparison of the diffracted beam intensity from a SRM 688 basalt standard with a 2 kw parallel beam diffractometer and a 20 W polycapillary based Collimated X-Ray Beam (ref. 19) θ [deg] Plots offset by 500 cts for clarity The quasiparallel beam from the polycapillary collimator relaxes constraints on sample position, shape, roughness and transparency and therefore removes the sample preparation required by conventional Bragg-Brentano (parafocusing) geometry. This, together with the reduced power, size, weight and cost make collimating X-ray Systems natural candidates for on-line diffraction systems for quality control and

10 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume feedback in manufacturing and process environments. Such systems are under development and implementation for the semiconductor, steel, pharmaceutical and cement industries among others. Fig. 2 1 shows measurements involving diffraction from a silicon single crysta12 that illustrates the effect of changing the sample position on the diffracted peak. Fig. 22 shows a pole figure measurement of the texture of a 100 A silver thin film on a silicon crysta121. Figure 21. Diffracted beam shape and position for Si(100) with polycapillary Collimated Beam System and conventional Bragg- Brentano geometry (ref. 20). Using XOS polycapillary parallel beam optic Regular Bragg-Brentano Diffractometer I I : [ z 3000 P f Ii i :I :I II I I $ I! :: ; ii : 3 Ii 11 :: / ; Iis 2;; 1ooc-! 1000 _;: ; f ;::;, -1,i ( J :, 0,(,.>&d~ ;d;b; k.$,,.;~..~ O 47 - Omm - - 2mm 4mm Degrees 2 Theta Omm -- lmm Degrees 2 Theta Figure 22. Pole figure-100 AAgon Si(ll1) tex :ture map (ref. 21). The flexibility provided by the parallel beam Collimated Beam System is shown in Fig.23 where a setup is shown for powder diffraction measurements which eliminates preferred orientation errors22 and in Fig. 24 which shows an arrangement for in-plane scattering. X-Ray Source Monochromator Side View Soiler Slit Detector Top View ttt Air Flow Figure 23. Powder XRD with Collimated X-Ray Beam to eliminate crystallite preferred orientation (ref. 22). Detector Figure 24. Setup for in-plane scattering

11 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume Single crystal diffraction. The benefits noted above for powder diffraction also apply to single crystal diffraction applications. Perhaps the most important and most studied application to date has been application of a Collimated X- Ray Beam to protein crystallography23. Fig 25 is a schematic representation of such a measurement and a diffraction pattern for Lysozyme is shown in Fig mm 1Omm -* F- microfocus polycapillary x-ray source concentrator --A 0.5mm, l., l.., /. s l *.,,., * X/1 _*-- _--. l ---; ---_I~ $9 macromolecular cryslal a l _ ;i_ 2 r.. :.- l - _ : : x-ra - deiec r or. Figure 25. Schematic resentation of protein crystallography measurement. The diffracted beam intensity obtained with a polycapillary monolithic optic with a slightly convergent (- 0.5 ) beam and a 50 watt microfocus source was equal or greater to that from a 5 kw rotating anode source equipped with the most advanced confocal optics, with resolution < 2 A and Rmerge < 6 % for Lysozyme24. At the present time the local divergence (divergence of X-rays from each capillary channel) of -0.12, limits the unit cell size of molecules that can be analyzed to Figure 26. Diffraction pattern < 200 A. A similar X-ray Beam based system which also for Lysozyme (ref. 23). includes a graphite monochromator and which is available commercially has recently been announced25 By using more strongly convergent beams26 (up to - 2, it is possible to obtain even higher X-ray density on smaller beam spots. Together with special software27 for analysis of convergent beam diffraction patterns these can be used for screening of very small protein crystals2*, microdiffraction measurements with very low source power (-2W)(e.g. for planetary rovers), and for neutron diffraction from small crystals for macromolecular structure, high pressure, or low temperature studies X-ray lithography Polycapillary collimating optics can also be used to produce a quasiparallel beam for X-ray lithography7. The setup for this is shown in Fig. 27. Figure 27. X-ray lithography (XRL), with potential applications and benefits. l l Applications - Large volume - Small features - Large dies - Memory chips - GaAs semiconductors - Deep Lithography l Michromechanical systems Benefits - Mass production - Small resolution - Parallel Beam

12 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume MEDICAL A potential major area of application for polycapillary optics is in medicine 30. Used as magnifying angular filters, they have demonstrated significant and important increase in contrast and resolution for mammography 31 and are under active investigation for other soft tissue imaging and for cancer therapy. These also represent enabling applications of polycapillary optics but are not reviewed in this paper because of limited space and because they are at an earlier stage of general acceptance and application than the examples given. Also, they are reviewed in papers in the Denver 2001 Conference proceedings 32, 33 and in the 2001 SPIE Conf. Proceedings CONCLUSIONS Polycapillary optics have gained broad acceptance and are now being used in a broad variety of applications. Beginning as optics individually integrated into research setups, they then were 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. Development of compact X-ray sources, matched to the optic input requirements have allowed large reduction of the size, power and weight of X- ray systems which are now resulting in development of compact X-ray sensors for portable, remote or inline sensors for new applications in industry, science or medicine. 6. REFERENCES 1. A.H. Compton, Phil. Mag. 45, 1121 (1923). 2. F. Jentzch and E. Näring, Die Forteitung von Licht und Rötgenstrahlen durch Rören, Zeitschr. F. Techn. Phys., 12, 185 (1931). 3. V.A. Arkd ev, A.I. Kolomitsev, M.A. Kumakhov, I.Yu. Ponomarev, I.A. Khodeev, Yu. P. Chertov, and M. Shakparonov, Wide-Band X-ray Optics with a Large Angular Aperture, Sov. Phys. Usp. 32(3), 271 (1989). 4. M.A. Kumakhov and F.F. Komarov, Multiple Reflection from Surface X-ray Optics, Phys. Rep., 191(5), 289 (1990). 5. W.M. Gibson and M.A. Kumakhov, Application of X-ray and Neutron Optics, Proc. SPIE, vol. 1736, (1992). M.A. Kumakhov, U.S. Patent No. 5,192,869, Device for Controlling Beams of Particles, X-Rays, and Gamma Quanta, Appl.. 5/91, Issued 6/ Kardiawarman, B.R. York, X.-W. Qian, Q.-F. Xiao, C.A. MacDonald, and W.M. Gibson, Application of a Multifiber Collimating Lens to Thin Film Structure Analysis, Proc. SPIE, 2519, 197 (1995). 7. Z.W. Chen, R. Youngman, T. Bievenue, Q.-F. Xiao, I.C.E.Turcu, R.K. Grygier, and S. Mrowka, Polycapillary Collimator for Laser-Generated Plasma Source X-Ray Lithography, SPIE Proc., vol. 3767, (1999) 8. Internal XOS data. 9. N. Gao, I.Yu. Ponomarev, Q.F. Xiao, W.M. Gibson, and D.A. Carpenter, Monolithic Polycapillary Focusing Optics and their Applications in Microbeam X-Ray Fluorescence, Appl. Phys. Lett., 69, 1529 (1996). 10. G.J. Havrilla and N. Gao, Dual-Capillary Optic MXRF, Proc. of Denver 2001 X-Ray Conf. (2001). 11. N. Gao and D. Rohde, Using a Polycapillary Optic as a Spatial Filter to Improve Mico X-Ray Analysis in Low-Vacuum and Environmental SEM Systems, Proc. Microsc. Microanl., 7, 700 (2001). 12. H. Soejima and T. Narusawa, A Compact X-Ray Spectrometer with Multi-Capillary X-Ray Lens and Flat Crystals, Proc. 49 th Ann. Denver X-Ray Conf., July (2000). 13. D.A. Wollman, C. Jezewski, G.C. Hilton, Q.-F. Xiao, K.D. Irwin, L.L. Dulcie, and J.M. Martinis, Proc Microscopy and Microanalysis, 3, (1997). 14. D. A. Wollman, K.D. Irwin, G.C. Hilton, L.L. Dullcie, D.E. Newbury, and J.M. Martinis, J. Microscopy, 188, (1997).

13 Copyright (c)jcpds-international Centre for Diffraction Data 2002, Advances in X-ray Analysis, Volume T. Taguchi, Q.-F. Xiao, and J. Harada, A New Approach for In-Laboratory XAFS Equipment, Proc. 10 th Int. Conf. On X-ray Absorption Fine Structure, (1998). 16. K. Janssens, K. Proost, L. Vincze, G. Vittiglio, G. Falkenberg, F. Wei, W. He, and Y, Yan, Polycapillary-Based Micro-XRF and Micro-Xanes by means of Conventional and Synchrotron Radiation, Proc. of Denver 2001 X-Ray Conf. (2001). 17. H.H. Chen-Mayer, G.P. Lamaze, D.F.Rmildner, R. Zeisler, and W.M. Gibson, Neutron Imaging and Prompt Gamma Activation Analysis using a Monolithic Capillary Neutron Lens, Proc. Japanese Conf. On Neutron Scattering, July, 2001., J. Phys. Soc. Japan, to be published (2001) 18. C.H. Russell, M. Gubarev, J. Kolodziejczak, M.K. Joy, C.A. MacDonald, and W.M. Gibson, Polycapillary X-ray Optics for X-ray Astronomy, Advances in X-Ray Analysis (Proc. of 48 th Ann. Denver X-ray Conf.), vol. 43, (1999). 19. XOS internal data, M. Haller, private communication. 20. S. Bates, 6 th European Powder Diffraction Conf., Budapest, 1998 (oral presentation). Data from S. Bates, KRATOS Corp. private communication. 21. K.M. Matney, M. Wormington and D.K. Bowen, Bede Scientific Cor., private communications. 22. T. Yamanoi and H. Nakazawa, Parallel-Beam X-ray Diffractometry using X-ray Guide Tubes, J. Appl. Cryst., 33, (2000). 23. S.M. Owens, J.B. Ullrich, I.Yu. Ponomarev, D.C. Carter, R.C. Sisk, J.X. Ho, and W.M. Gibson, Polycapillary X-Ray Optics for Macromolecular Crystallography, SPIE Proc., vol. 2859, (1996). 24. M. Gubarev, E. Ciszak, I. Ponomarev, W. Gibson, and M. Joy, First Results from a Macromolecular Crystallography System with a Polycapillary Collimating Optic and a Microfocus X-ray Generator, Jour. Appl. Cryst., 33 (3), (2000); M. Gubarev, E. Ciszak, I. Ponomarev, W. Gibson, and M. Joy, A Compact X-ray System for Macromolecular Crystallography, Rev. Sci. Instr., 71, (2000). 25. S.I. Foundling, M. Li, B. Michell, S.M. Edved, and R. Durst, Proteum M: The compact laboratory solution, presented at Am. Cryst. Assoc. Conf., July, S.M. Owens, F.A. Hofmann, C.A. MacDonald, and W.M. Gibson, Microdiffraction using Collimating and Convergent Beam Polycapillary Optics, in Advances in X-Ray Analysis, Proc. Of the 46 th Ann. Denver X-ray Conf., vol. 41, (1997). 27. J.X. Ho, E.H. Snell, C.R. Sisk, J.R. Ruble, D.C. Carter, S.M. Owens, and W.M. Gibson, Stationary Crystal Diffraction with a Monochromatic Convergent X-Ray Source and Application for Macromolecular Crystal Data Collection, Acta Cryst., D54, (1998). 28. H. Huang, C.A. MacDonald, W.M. Gibson, J.X. Ho, J.R. Ruble, J. Chik, A Parsegian, and I. Ponomarev, Focusing Polycapillary Optics for Diffraction, Proc. of Denver 2001 X-Ray Conf. (2001); 29, W.M. Gibson, H.H. Chen-Mayer, D.F.R. Mildner, H.J. Prask, A.J. Schultz, R. Youngman, T Gnäupel-Herold, M.E. Miller, and R. Vitt, Polycapillary Optics Based Neutron Focusing for Small Sample Neutron Crystallography, Proc. of Denver 2001 X-Ray Conf., (2001) 30. W.M. Gibson, C.A. MacDonald, and M.A. Kumakhov, in Technology Requirements for Biomedical Imaging, S.K. Mun, ed., I.E.E.E. Press Vol. 2580, (1991); C.A. MacDonald and W.M. Gibson, Medical Applications of Polycapillary X-ray Optics, Proc. SPIE, vol. 2519, (1995). 31. D.G. Kruger, C.C. Abreu, E.G. Hendee, A. Kocharian, W.W. Peppler, C.A. Mistretta, C.A. MacDonald, Imaging Characteristics of X-Ray Capillary Optics in Mammography, Medical Physics, 23 (2), , (1996). 32. F. A. Sugiro, C.A. MacDonald and W.M. Gibson, High Contrast Imaging with Polycapillary Optics, Proc. of Denver 2001 X-Ray Conf. (2001). 33. W.M. Gibson, H. Huang, J. Nicolich, P. Klein, and C.A. MacDonald, Optics for Angular Filtering of X-Rays in Two Dimensions, Proc. of Denver 2001 X-Ray Conf. (2001)