The discovery of traces of life in the ancient Mars meteorite triggered the development of the rapidly emerging field of Astrobiology. Astrobiologists are seeking to develop conclusive methods to recognize biosignatures and microfossils of bacteria and other microbiota as well as to understand the spatial, temporal, environmental and chemical limitations of microbial extremophiles. Recent discoveries have revealed the great distribution and diversity of microbial extremophiles on Earth and profoundly increased the probability that life may exist elsewhere in the Cosmos. The rapidly emerging science of Bacterial Paleontology has provided important new information critical to the recognition of fossil bacteria on Earth and in Astromaterials. We have recently conducted independent scanning electron microscopy and x-ray analysis investigations in the US and Russia in order to better understand the morphology and chemical composition of microfossils in ancient terrestrial rocks and carbonaceous meteorites. In this paper, we review some aspects of microbial extremophiles of Earth as modals for life on other bodies of the Solar System. We consider several of the important chemical, mineral and morphological biomarkers that provide definitive evidence of biogenic activity in ancient rocks and meteorites. We present Environmental Scanning Electron Microscope images of microfossils found in-situ in freshly fractured meteorite surfaces and describe Energy Dispersive Spectroscopy and Link microprobe analysis of the chemical elements in the mineralized and/or kerogenous microfossils and meteorite rock matrix. We also discuss technqiues and methods that may be used to help discriminate indigenous microfosils from recent terrestrial contaminants. We will also present new data from our in-situ investigations of living cyanobacteria and bacteria and freshly broken surfaces of terrestrial rocks and meteorites. Comparative analysis of these images are interpreted as providing dramatic evidence of indigenous microfossils of magnetotactic bacteria, cyanobacteria, and acritarchs in the Nogoya, Efremovka, Orgueil, Murchison and Tagish Lake Meteorites. Many of the forms in carbonaceous meteorites are large and complex providing strong evidence of biogenicity. Many of the forms found in carbonaceous meteorites are strikingly similar to microfossils of bacteria, cyanobacteria and fungi we know from the Cambrian phosphorites of Khubsugul, Mongolia and high carbon Phanerozoic and Precambrian rocks of the Siberian and Russian Platforms. Some meteorite microfossil assemblages are consistent with known characteristics of distinct microbial life cycles and reproductive stages of Nostocacean cyanobacteria. We also recognize assemblages consistent with microbial ecosystems we studied in permafrost and cryoconite communities of Antarctica, Alaska and Siberia and microfossil ecosystems from the Cambrian of Mongolia.
The paper discusses status of the polycapillary optics and its perspectives for the nearest future. Modern level of the polycapillary optics technology permits to speak about possible implementation of a 'laboratory synchrotron' based on a combination of small micro-focus x-ray tubes with (10 ÷ 100) W power only and optics. In this instance, at the lens focal spot having a size of several microns, a flux of the order of 107 photon/sec μm2 is obtained. After a half-lens, it is possible to obtain quasi-parallel monochromatic flux with 1010 photon/sec mm2 density. These parameters aer comparable with those of mid-generation synchrotrons. On the basis of this optics, the Institute for Roentgen Optics has created new generations of compact x-ray fluorescent spectrometers, diffractometers, comparators etc.
Refractive microcapillary lens for hard x-rays is presented. The lens is designed as glass capillary filled by a large number of biconcave microlenses. Fabrication technique for the lens is described. It is shown that the the microlenses have a spherical shape. The spherical aberrations of the lens are calculated. The possibility of production of micrometer sized x-ray beams by using the microcapillary x-ray lens is discussed.
An approach to the numerical simulation of optical systems consisting of tens of x-ray lenses arranged in series is described. Possibilities of such an approach for the simulation of a multi component optical elements is considered.
Features of a planar x-ray waveguide (PXW) functioned on the base of an x-ray total reflection phenomenon and been distinguished by an air clearance presense as the transportation medium are discussed. It is shown that the narrow size clearance area exists, and it is characterized by a resonance manner of an x-ray beam guiding across the waveguide. The high efficiency of the x-ray beam transporation systems based on planar x-ray waveguides allows them to complete with guiding abilities of the polycapillary optics. Characteristics of an x-ray diffractometer and TXRF-spectrometer equipped with PXW are analyzed. The experimental data of a thin film testing at application of the diffractometer and the TXRF spectrometer built with using PXW are presented. The design of the planar x-ray waveguide-monochromator is considered, in passing.
We developed and studied refracting microcapillary lens for x-ray photons with energy 5.4 keV. This lens is a glass capillary wiht a central channel filled with a number of concave microlenses. The lenses are made by injection compressed air into a capillary channel, previously filled by liquid polymer. The images of 20-100μm width slits are obtained. A good agreement is seen betweenthe image and slits sizes. Ray tracing calculations of iamge formation are made. Experimental and calculated results are in a good agreement.
While processign experimental data, it is important to have pictorial presentation of information. Currently, within the scope of the research programs carried out at the Institute for Roentgen Optics, severla automated set-ups have been created and are now used to perform x-ray scanning experiments. At the development stage it became clear that presentation of experimental data in a pcitorial and conventient to the researcher form, by means of 3D computer graphics algorithms, enables more precise evaluation of the results and, thus, correctly determination of the strategy for further research.
Simulation of x-ray transmission through glass poly-capillary structures is considered. Authors obtained sufficiently high level of correlation between the parameters of actual products and parameters calculated through tracing using teh proposed software model.
Planar neutron waveguide structures can be used as resonant beam coupling devices to produce a coherent and divergent neutron line source with cross-sections in the sub-micrometer range. This article reveiws our recent work on the theoretical model, the fabrication and the characterization of these devices, demonstratign cleraly the good agreement between the theoretical model and the feasability of using neutron waveguides for various applications. As one major result, the farfield-pattern of the first three modes of a neutron waveguide was measured, yielding a 17 times enhanced flux throughput compared to a pair of slits corresponding to the thickness of the guiding layer. Additionally we have generalized the principle of neutron resonant beam coupling to waveguides containing multiple guiding layers, where several beams iwth a width of the order of 10 to 100 nm can be extracted at the end leading to an typical farfield interference pattern.
Review on wave theory of x-ray channeling in capillary systems of various channel sizes is presented: theoretical models of coherent and incoherent scattering, which have been developed for the last years, are considered; analysis of recent experimental results on radiation distribution behind capillary systems is given. It has been shown that the propagation of radiation at conditions defined may be presented as interference of surface bound states depending strongly on surface curvature.
Due to the low value of the critical angle, the main problem is using a polycapillary lens is to position it correctly with respect to the x-ray source. We have developed a recursive procedure for fast and precise alignment by means of a four-circle diffractometer and a Cu x-ray tube. After the alignment we observed the focusing effect on a fluorescent target and measured an increase of about 30 in the local density of the x-ray beam. During the experiments a sharp decrease in the beam divergence behind the capillary structures was also detected. This unexplained fact, already mentioned in the past by several reserachers, was explained for the first time by our group in the framework of the wave scattering theory. The same alignment procedure was successfully repeated using synchrotron radiation at the Elettra storgae ring at Trieste. The focal spot position was evaluated by a set of photo images. In the same experiment we also tested and evaluated the operating characteristics of a straight polycapillary lens.
In this report the main results of experimental study on possibility to apply capillary structures for handling soft synchrotron radiation are presented. This research has been done at the S-60 FIAN accelerator facilites for the period 1993-1999. The possibility of using capillary systems to control the parameters of soft SR, such as radiation density and bending of beam, at the specified wavelength range has been experimentally confirmed. Discovered for the first time the structural radiation redistribution at the focal plane behind the capillary halflenses was carefully studied in experiments with two bent capillaries of focusing geometry. As a result the wave scattering theory of radiation inside the capillary channels was developed. The first experiments on measuring the luminescence spectrum for Ce3+ lithium/yttrium fluoride matrix by the use of capillary halflens has been done in comparison with the spectrum for the direct SR beam. The last confirms the fact that capillary optics is useful instruments to condense the radiaton beam on the samples of small sizes.
The results of measurements of x-ray polycapillary transmission coefficient for 1.5 keV photons are given. As a source of quasi-monochromatic x-ray, a transmission-type aluminum anode x-ray tube was used for investigation of capillaries' optic features. The dependence of radiation intensity at the exit from the poly-capillary tube on the diameter of the radiation source, capillary length, and focal distance was studied. Poly-capillary transmittance capability was measured depending on the curvature radius. Measurement results are compared with calculations.
An x-ray reflectometer has been developed based on Kumakhov's optics for roughness contorl fo polished surfaces and thin-film analysis for microelectronics applications. The half-lens used enables production of spatially collimated quasi-parallel x-ray required for the method, considerable decrease of the device's dimensions and x-ray power compared to existing models. The ability of Kumakhov's half-lenses to raise x-ray quanta density makes it possible to raise significantly the reflectometer's luminosity and reflectivity while reducing hte background.
For the first time the technology of a small-size polycapillary lenses manufacturing was proposed. Technique of micro lens certification is considered. Efficiency of simultaneous using of such lenses and micro focus x-ray sources is shown.
Different radial capillary layers give different contributions in x-ray radiation field at Kumakhov lens of halflens exit. In case of halflenses transforming divergent beams into quasiparallel ones it can essentially influence an exit quasiparallel beam uniformity; in case of lenses and halflenses transforming quasiparallel beams into covergent ones focus position and focal spot uniformity depend on radial layers of capillary structure. This question is essential both for studying and using Kumakhov capillary optics. Different radial layers of Kumakhov lens are experimentally studied in this work from the standpoint of their influence on a focal spot forming.
For technological proces of polycapillary produciotn and for their further use it is necessary to know x-ray radiation transmission by polycapillary structures and its dependence on quanta energy. For this purpose special installation was assembled, technique was worked out and measurements were carried out. This paper incldues a description of the set-up, details the process of measurement and covers the outcome results.
Dose distributions of the secondary electrons were calcualted by Monte Carlo code EGS4 in water nera an infinitesimal area photon microbeam. The photon eneryg was from 10 to 100 keV, the radial resolution was 2 μm and the statistical error was from 0.1 to 1-2 percent depending on the calculation point. The Compton recoil electron and photoelectron dose fractions were separated from the dose profiles and fitted by simple analytical functions.
Investigation of Kumakhov halflenses for thermal neutron focusing was carried out on the monochromatic beam of horizontal channel at the Karpov Institute WWR-ts reactor. Efficiency and gain coefficient were measured for two halflenses. Estimation of real halflens focal spot for focused neutron monochromatic beam was made.
One of the most important features of the developed portable diffractometer making use of Kumakhov's half-lens is that allows stress strain analysis in different sections of the investigated object. Here the investigation results are presented showing efficiency of using Kumakhov's lens in reducing noise, lessening width and increasing diffraction maximums' intensity, as well as towards better accuracy of determining their angle deviation. Use of x-ray capillary half-lens to create a spatially collimated quasi-parallel beam and of full capillary lens to focus x-ray permitted a functional combination of a diffraction and spectrometer units with PSD and energy-dispersion semiconductor detectors to enable simultaneous receipt of information about stress-strain condition and element composition, respectively. The quantitative assessment of the above parameters was done based on the in-house software. Element composition analysis including strain crystal lattice deformation of material in actual products makes it possible to distinguish between deformations that occurred at the stage of manufacture or acquired in the process of operation, and strain conditions due to local changes in element composition, which is an extremely important criterion of reliability of products. Information about product's changed percentage of chemical content in stress and strain localities will provide additional information assisting expert evaluation of reasons for metal structures failures.
The possibility of increasing quanta flux intensity is considered. It was shown, that use of a single capillary glass channel permitse to change the total amount of the photons inciding per second onto the sample surface. Microcapillary devices for the study of macro-molecular structure were made.
New x-ray chemical micro analyzer for the invesitgation of chemical elements spatial distribution and for the element analyis has been designed. Characteristics of a new device and possibilities of its application are considered.
It is known that polycapillary half-lenses and lenses limit x-ray energy both in low and high eneryg area, i.e. they create an energy transmission range from 2 to 20 keV. This enables use of the lenses as filters wihtin a wide energy range. The effective transmisison range for each x-ray optical system was determined. To obtain a monochromatic beam within a narrow energy range, the spatial collimation of x-ray beam by means of Kumakhov's half-lens and deflection it from a flat monochromator was perforemd. The block scheme of x-ray monochromator is described. Using the second half-lens, it is possible to focus monochromatic CuKα1 radiation. Such super-high monochromatization is reqruied for phase analysis of complex structures characterized by low symmetry.
At present x-ray compact tubes with pass-through anodes operating either in the pulse mode or in the direct voltage one are applied to the equipment for the shady microscopy, and the local XRF analysis. The report presents the calculated spectral intensity distributions of the bremsstrahlung versus the pass-through anode thickness. The spectral function of the bremsstrahlung Mo tube with the anode thickness over 100 microns is demosntrated to contract to the narrow energy interval lying near the characteristic anode radiation range. However under the same conditions the spectrum of the pulse Cu-anode tube tends to be dichromatic. The spectral distributions of the tube bremsstrahlung operating at the direct current and pulse voltage are compared.
This work was aimed at investigating the possibility of using low-power x-ray generators with pointed tube and magnetic focusing capabilities for the certification of a small-size x-ray lenses and to obtain high-density x-ray. X-ray micro-focal generator was created based on BS-13 transmission anode micro-focal tube. X-ray integral intesity from generator was established at different modes of operation, its operation stability was assessed. Application of this type fo x-ray generator was proven efficient to obtain quasi-parallel and convergent high-density x-ray via Kumakhov's optics.
This paper suggests the scheme of a diffractometer for phase and crystal structure analysis of inorganic matter, where the Kumakhov's capillary half-lens is used as the collimation system. Goniometer-free design of the diffractometer enables application of two x-ray tubes with different anodes and capillary half-lenses with registration of the diffraction picture. Along with the diffraction unit, the x-ray assembly includes a spectrometer unit providing for a quantitative analysis of the chemical composition in the same selected target area. Concurrent knowledge of the diffraction picture and chemical composition of an unknown matter narrows the field of search for phase composition and crystal structure via software and facilitates receipt of reliable information about the target.
The main component in the x-ray layout of the portable diffractometer is Kumakhov's focusing capillary lens with a certain x-ray convergence angle of ~1-3°, permitting a benchmark determination of a monocrystal plates crystallographic orientation using a PSD detector that registers diffraction reflection at ~5° takeoff angle. Since use is made of x-ray converging on the sample, it renders unnecessary to rotate crystal holder in search for maximum diffraction reflection. Dependence of the diffraction reflection's shape and width on the quality of monocrystal plate treatment during various technological operations, such as cutting, grinding, polishing, has been established.
Intensity distribution of Mo L x-rays at the half-lens exit was measured, as well as the parameters of the electron induced X-rays source were studied. The measurements have shown that efficiency of production of X-rays with 1.5-2 keV depends on electron energy and reaches its maximum within the electron energy range of 10 keV-15keV. Efficiency of K Al and L Mo x-rays production at the half-lens exit was studied, when excited by electron beam under rotating cylinder anode and flat stationary anode conditions. Measurement results are compared to the calculations and data of other experiments.
X-ray fluorescent spectrometer 'Focus M' wiht polycapillary optics is the modification of the spectrometer 'Focus 1' created at the Institue for Roentgen Optics in 1999. The device consists of three-coordinate movable table for fixing a sample, accessory filters, and optical microscope.
On the basis of Kumakhov's poly-cappillary half-lens and one-crystal spectrometer, a high aperture x-ray monochromator was developed featuring high angular and energy resolution. The resolution of ΔE approximately equal to 15 eV was obtained for quartz crystals with reflection. Application of poly-capillary half-lenses in x-ray diffractometry of perfect and defective crystals and x-ray absorption spectroscopy is discussed.
A new version of diffraction method for measuring the absolute values of intra-plane distances dhkl in crystals and epixtaxial films using Kumakhov's x-ray poly-capillary half-lenses was developed. An attachment attachment to general-purpose x-ray diffractometer MRD was develoepd to register diffractograms within the angle range between 0 ÷ 160° with error of Δhkl/d approximately 10-5. A method of precision dhkl measurement was verified using perfect quartz crystals.