Ge X-ray Research Articles

Time-resolved X-ray diffraction diagnostic development for the National Ignition Facility.

We present the development of an experimental platform that can collect four frames of x-ray diffraction data along a single line of sight during laser-driven, dynamic-compression experiments at the National Ignition Facility. The platform is comprised of a diagnostic imager built around ultrafast sensors with a 2-ns integration time, a custom target assembly that serves also to shield the imager, and a 10-ns duration, quasi-monochromatic x-ray source produced by laser-generated plasma. We demonstrate the performance with diffraction data for Pb ramp compressed to 150GPa and illuminated by a Ge x-ray source that produces ∼7 × 1011, 10.25-keV photons/ns at the 400μm diameter sample.

Ionization disequilibrium in K- and L-shell ions

Time-gated Sc K-shell and Ge L-shell spectra are presented from a range of characterized thermodynamic states spanning ion densities of 1019–1020cm−3 and plasma temperatures around 2000 eV. For the higher densities studied and temperatures from 1000 to 3000 eV, the Sc and Ge x-ray emission spectra are consistent with steady-state calculations from the modern atomic kinetics model SCRAM. At the lower ion densities achieved through plasma expansion, however, the model calculations require a higher plasma temperature to reproduce the observed Ge spectrum. We attribute this to ionization disequilibrium of the Sc because the ionization time scales exceed the hydrodynamic timescale when the inferred temperatures diverge.

Using GEANT4 Monte Carlo simulations to resolve low energy [formula omitted]-ray spectra: The study of [formula omitted] decay using a broad energy HPGe detector

Within the present work a peak analysis and unfolding method for low energy γ-ray spectroscopy is presented. This method can be used to facilitate the determination of the peak integral of a photopeak, when Ge X-ray escape peaks contaminate the latter and in parallel the source activity and the emission rate of the recorded photons which produce the escape peaks are unknown. It is based on extensive Monte Carlo simulations of the spectra by taking the full advantage of power and accuracy provided by the GEANT4 simulation toolkit.

Important roles of native-oxides on the electronic band offsets at Ge-oxide/Ge(0 0 1) heterojunction in ambient environment

Metal/semiconductor-oxide interface is a major focus in condensed matter physics due to its rich fundamental properties and potential novel electronic applications. Our understanding of the impact of native oxide on metal/semiconductor-oxide interface (e.g. Ge) remains nonetheless elusive. Herein, we address this by purposefully exposing a clean Ge(001) surface to ambient environment (up to 600 days). The extend of Ge oxidation and binding energy (BE) shifts in the core-levels of Ge X-ray photoelectron peaks (Ge3d and Ge2p3/2) are found to correlate directly with the GeOx/Ge (x ≤ 2) atomic composition. A universal scaling in the band offsets at the GeOx/Ge heterojunction with increasing Ge-oxide content is established independent of oxidation time. A maximum upward band bending of ~0.6 eV is observed in the electronic band structure, which can be attributed to the presence of Ge valence states (Ge1+, Ge2+, Ge3+, Ge4+) at the GeOx/Ge junction formed during oxidation. Our results exemplify the importance of native oxide on semiconductor in determining the fundamental properties of semiconductor-oxide interfaces.

Epidemiologic, Clinical and Radiological Aspects of Male Urethral Strictures at the Ngaoundéré Regional Hospital

Background: Urethral stricture is a disabling condition that remains prevalent due to the upsurge of sexually transmitted infections and traumatic lesions of the urethra during trauma of the pelvis in humans. Objective: Describe the epidemiological, clinical and radiological presentations of male urethral strictures. Method: It was a cross-sectional and descriptive study during a one-year period from January to December 2017 including all male patients presenting for a urethrocystography examination, at the Ngaoundere Radiology and Medical Imaging Center who agreed to participate. The urethrocystography technique depended on patient’s condition and was either retrograde, anterograde, or following intravenous urography. The examinations were performed with GE X-ray equipment using Kodak Dry View CRs. The interpretation was performed by a radiologist with at least five years of experience. The variables studied were age, clinic, history, uretrocystography technique and results. The data were collected using a previously established data sheet and processed with Sphinx Plus2 V5 and Microsoft Excel 2010 software. Results: 39 patients were enrolled in this study; the average age of our patients was 43.8 years with extremes of 4 and 76 years. The 50 - 60 age group (30.7%) was the most affected. Infection (53.9%) and trauma (23.1%) were the most common etiologies; dysuria (38.5%) and diminution of urinary flow (30.8%) were the most patient’s complaint. Retrograde urethrocystography (66.7%) was the most performed technic. Minimal bleeding in 46.2% of patients was the most common incident during urethrocystography; 76.9% of patients had a difficult urination and 7.7% an impassable urethral meatus. After interpretation, 84.6% of patients had urethral stenosis, which was associated with bladder diverticula (23%) and fistulas (15.3%). The stenosis was seated on membranous urethra (81.8%), tight type (45.4%), short (66.7%) and single (81.8%). The post-void residue was significant in 84.6% of cases and not significant in 15.4% of cases. 15.3% of the urethrocystographies were normal. Conclusion: Urethral stenosis in Ngaoundere mainly affects young adult; the main etiology is infectious, very often unique, short, and tight and the membranous urethra is the seat of predilection. Hence, to reduce the extent of pathology with its functional consequences and its impact on the socio-professional life in our context, the focus should be on sexually transmitted infectious.

Investigation of the Low Temperature / High Temperature Approach to Produce Si0.5Ge0.5 and Pure Ge Strain Relaxed Buffers

We have checked whether or not the Low Temperature / High Temperature approach used for pure Ge growth on Si yielded high quality Si0.5Ge0.5 Strain-Relaxed Buffers (SRBs) that could serve afterwards as templates for thick Ge layers. We had, as soon as the Si0.48Ge0.52 layers grown at 550°C plastically relaxed, a surface roughening which was not recovered by the 850°C growth of Si0.5Ge0.5 (rms roughness: 5 nm). Thickening it with Ge at 750°C and using a Thermal Cycling yielded a slight surface roughness decrease, however (down to 4 nm). The HT Si0.5Ge0.5 and pure Ge layers were slightly tensile strained. This was due to thermal expansion coefficient differences between Si and SiGe (Ge) coming into play during the cooling-down to room temperature. We had otherwise used the Ayers’ theory in order to transform the full widths at half maximum of SiGe and Ge X-Ray Diffraction omega scans into Threading Dislocations Densities. We would then have, for 60° misfit dislocations in our stacks, the following values: 3.5x108 cm-2 in annealed 1.7 µm thick Si0.5Ge0.5 SRBs and 1.6x108 cm-2 in the 1.3 µm thick Ge layers on top. Those values were definitely higher than those in 1.4 µm thick, cyclically annealed pure Ge layers grown directly on Si and in the top part of ~ 6 µm thick Si0.5Ge0.5 linearly graded virtual substrates.

Accuracy of a dose map method assessed in clinical and anthropomorphic phantom situations using Gafchromic films.

A dose map method has been integrated on GE x-ray angiographic systems to provide an indication of the local dose distributed on a patient envelope representative of individual patient shapes. Tests have been performed to assess the accuracy of the method by using Gafchromic XR-RV3 films in an anthropomorphic phantom situation and in a clinical situation. Dose values inside different exposed areas have been compared between the film and the dose map method. The dose map results show a good visual agreement for the anthropomorphic phantom situation, and the local doses agreed within better than 15 % compared with the Gafchromic films in both situations.

Systematic studies of Si and Ge hemispherical concave wafers prepared by plastic deformation

Si and Ge hemispherical concave wafers can be prepared by plastic deformation using Si and Ge single- and polycrystal wafers. Deformation regions in which such Si and Ge hemispherical wafers can be obtained by high-temperature plastic deformation were systematically studied. The deformation regions in which well-shaped Si concave wafers can be obtained were studied for (1 0 0), (1 1 1), and polycrystal Si. It was found that Si (1 1 1) crystal wafers can be more easily deformed to a perfect hemispherical shape than (1 0 0) wafers because of the crystallographic symmetry. Si hemispherical wafers with a small radius of 25 mm can be perfectly deformed when 0.5-mm-thick Si (1 1 1) crystal wafers are used. Ge hemispherical wafers with a radius of 100 mm can be perfectly deformed when 0.5-mm-thick Ge crystal wafers are used. Ge hemispherical concave wafers with a perfect shape can be more easily obtained using Ge (1 1 1) wafers than (1 0 0) wafers. According to these results, the deformation behavior of Ge wafers is very similar to that of Si wafers at a normalized pressing temperature. As both the radius and the load on Si and Ge hemispherical wafers increase, thicker Si and Ge wafers can be used to obtain hemispherical wafers with a perfect shape. The dislocation density in the shaped wafers markedly decreases as the pressing temperature and hemisphere radius increase. Thus, it is suggested that Si and Ge shaped wafers are of sufficient quality and have the high potential for use as several types of lens such as those in Si and Ge X-ray monochromators.

Studies on Ne-like Ge X-ray laser driven by a 2ω nanosecond laser

Generally, it is more suitable for studies on Ne-like X-ray laser by using fundamental frequency laser as driving beam than by frequency doubling. However, many huge laser facilities built for ICF research are usually designed for doubling and trebling of laser frequency, and they are unfit for use as fundamental frequency laser. We simulated the Ne-like Ge X-ray laser making use of JB19 codes, respectively in the case of doubled and trebled frequency diving. The results indicated that the higher power output of Ne-like Ge X-ray laser is also obtained when driven by doubled frequency laser. However the required output of driving laser beam was 3.3 times that in the case of the fundamental. Any way it presents a direction of studying Ne-like X-ray laser with huge laser facilities in the future. A preliminary experimental study has proved this point.

In-air micro-PIGE measurement system for fluorine analysis of the tooth

An in-air micro-PIGE and micro-PIXE measurement system for fluorine analysis of tooth have been developed at the Wakasa Wan Energy Research Center. A proton microbeam is extracted through a thin silicon nitride window into the air and used to irradiate a tooth sample mounted on a sample stage set in air. Gamma-rays from a 19F(p, αγ) 16O reaction and characteristic X-rays are detected with a BGO detector and a Ge X-ray detector, simultaneously. The sample stage and beam scanner allow us to analyze the tooth sample over a range of 20 mm at maximum. Spot sizes of a proton beams in air at an energy of 2.5 MeV was 4 μm, in the case of a distance between the silicon nitride window and the sample of 0.2 mm and 13 μm in the case of 1.7 mm. Fluorine analysis was performed over an area of about 3 mm × 3 mm of the tooth sample. One- and two-dimensional distributions of fluorine and calcium were obtained successfully. Quantitative analysis was also performed using data for measurements of reference materials Ca 10(PO 4) 6(OH) 2−2 x F 2 x .

Simulations of a Ne-like Ge X-ray laser and comparison with experiments in RFNC-VNIIEF

The results of 3D simulations of the laboratory Ne-like Ge x-ray laser in RFNC-VNIIEF are in good agreement with the experimental data. Calculations show that considerable rise of brightness and transverse coherence length can be achieved under half-cavity conditions.

Calculation of coincidence summing corrections for X-ray peaks and for sum peaks with X-ray contributions

In this paper, features of the gamma-ray spectra in the presence of important contributions of X-rays to coincidence summing effects are studied. The experimental results concerning the sum peaks with various X-ray combinations as well as the Ge X-ray escape peaks present in the spectrum of a 133Ba point source measured with an n-type detector are in good agreement with the values computed using the GESPECOR software.

Splitting of X-ray diffraction peak in (Ge:SiO2)/SiO2 multilayers

(Ge:SiO 2 )/SiO 2 multilayers were fabricated for exploring the influence of the stress on the structure of Ge nanocrystals. When annealed at 800 °C, the multilayers show a clear splitting (fine structure) of the Ge (220) X-ray diffraction peak and have a preferred orientation. Similar effects cannot take place in the multilayers annealed at higher or lower temperature. Analyses of Raman scattering, X-ray diffraction spectroscopy, and transmission electron microscope observations suggest that the observed phenomena arise from compressive stress exerted on Ge nanocrystals, which is induced by the confinement of both the SiO 2 matrix in the cosputtered layer and neighboring SiO 2 layers. The stress may cause an orthorhombic distortion of the diamond structure of bulk Ge. This will lead to the disappearance of the (111) and (311) diffraction peaks and the splitting of the (220) peak. This kind of (Ge:SiO 2 )/SiO 2 multilayers enables us to control the sizes of the Ge crystallites and enhance the stress, and is thus promising in forming new nanocrystal structures.

Splitting of X-ray diffraction peak in (Ge:SiO 2)/SiO 2 multilayers

(Ge:SiO 2)/SiO 2 multilayers were fabricated for exploring the influence of the stress on the structure of Ge nanocrystals. When annealed at 800 °C, the multilayers show a clear splitting (fine structure) of the Ge (220) X-ray diffraction peak and have a preferred orientation. Similar effects cannot take place in the multilayers annealed at higher or lower temperature. Analyses of Raman scattering, X-ray diffraction spectroscopy, and transmission electron microscope observations suggest that the observed phenomena arise from compressive stress exerted on Ge nanocrystals, which is induced by the confinement of both the SiO 2 matrix in the cosputtered layer and neighboring SiO 2 layers. The stress may cause an orthorhombic distortion of the diamond structure of bulk Ge. This will lead to the disappearance of the (111) and (311) diffraction peaks and the splitting of the (220) peak. This kind of (Ge:SiO 2)/SiO 2 multilayers enables us to control the sizes of the Ge crystallites and enhance the stress, and is thus promising in forming new nanocrystal structures.

Evaluation of low-energy tailing parameters of a HPGe X-ray detector to be used in GUPIX software library for PIXE analysis

Accurate description of the response function of X-ray detectors is important for quantitative PIXE analysis. For analytical description of low-energy tailing in PIXE spectra, the GUPIX approach was used, i.e. a combination of Hypermate type functions. The low-energy tailing parameters of a low-energy high purity germanium X-ray detector in the region 1.3–9.2 keV was determined by systematic fitting of X-ray spectra from thin MicroMatter standards. Except for the main Gaussian peak and germanium escape peaks, one shelf, one truncated shelf, one exponential function and KMM radiative Auger feature was applied to fit the spectral data collected with this low-energy Ge X-ray detector. The overall trend of different tail parameters shows similar characteristic as those for Si(Li) X-ray detectors used in this energy range, i.e. very strong tailing at low X-ray energies and a rapid fall off with increasing X-ray energy. The fitted parameters, as a function of X-ray energy, were then incorporated into the GUPIX library for PIXE analysis.

Escape of photoelectrons and Compton‐scattered photons from an HPGe detector

AbstractThe response function of a planar HPGe detector due to escape of photoelectrons and Compton‐scattered photons was studied for a point source with 59.5 keV energy. It was shown that both mechanisms, in addition to Ge x‐ray escape, leading to partial deposition of energy, could be observed in the same experiment. A Monte Carlo program was used to investigate these components of the response function. The results indicate that although the escape of scattered photons and Ge x‐rays are of the same magnitude, the escape of photoelectrons plays a more important role in the efficiency of a detector. Copyright © 2003 John Wiley & Sons, Ltd.

Feasibility Study of Local Structure Analysis of Ultrathin Films by X-ray Fluorescence Holography

The feasibility of the determination of local atomic structure was tested by computing Ge X-ray fluorescence hologram patterns of a Ge film 3 atomic layers thick on a Si substrate. An atomic image obtained from a single-energy hologram pattern exhibits many small oscillations and a precise atomic image is difficult to evaluate. By summing plural images reconstructed from holograms obtained at several different energies, the final atomic image is improved due to the disappearance of the oscillations. The full-width at half-maximum of peaks of the atomic image reconstructed from six holograms calculated at 27.0–29.5 keV with 0.5 keV steps is 0.03 nm. This clearly demonstrates that the XFH method has strong potential as an experimental tool for evaluating the local atomic structure.

Measurement of Endodontic File Lengths: Calibrated Versus Uncalibrated Digital Images

This in vitro study compared the accuracy of file length measurements made on calibrated and uncalibrated direct digital images. Endodontic files of known lengths and ISO sizes were used in 10 single-rooted, relatively straight teeth within cadaver specimens. The crowns of the teeth were ground flat and an orthodontic wire of known length was secured to the coronal surface. This wire was placed mesiodistally and perpendicular to the root and served as the reference point for the file measurement and as a calibration reference length. A #20 file was hand-measured to a length that reached the apical third of each tooth. It was inserted and a radiographic image was secured. The instrument was remeasured three additional times at different lengths on the same tooth and reinserted before each image acquisition. Thus 40 digital images were acquired using a GE X-ray unit and a Schick Computed Dental Radiography (CDR) #2 sensor. These images were placed in random order, and an independent, blinded investigator determined the file lengths using on-screen calibrated and uncalibrated measurement of the CDR image with a straight-line and multiple-line measuring technique. The experimental measurements were compared with each other and with the known clinical measurements. A two-way analysis of variance indicated that there was a statistically significant difference showing that the calibrated measurements were more accurate than the uncalibrated measurements (p = 0.0001), and there was no significant difference between the straight-line and multiple-line measuring techniques (p = 0.14).

The new CSIRO–GEMOC nuclear microprobe: First results, performance and recent applications

A new nuclear microprobe (NMP) has been designed and built at the CSIRO featuring: (1) a quadrupole quintuplet lens system with a demagnification of 67 and 80 mm working distance; (2) a close detection geometry for Ge X-ray, 30% Ge γ-ray and particle detectors; (3) a high-quality normal-viewing microscope, coaxial with the beam; (4) computer-controlled beam-shaping and 5-axis sample stage; (5) scanning for imaging to > 5×2 mm 2 ; and (6) a vibration isolated mounting. Most design goals have been successfully achieved. On the first day of operation, a spot size of 1.3 μm was obtained at a beam current of 0.5 nA, suitable for fluid inclusion analysis and imaging. The spot size grows to just 1.8 μm at 8 nA (3 MeV protons) and 2 μm at 10 nA, despite the low brightness of our tandem accelerator ( 1.2 pA μm −2 mrad −2 MeV −1 ). This beam current is ideal for geological samples with PIXE detection limits down to 0.2 ppm (Br) achieved in silicates (39 ppb (Ge) in diamond at 22–25 nA) in quantitative, high resolution, trace element images.

Response function of a germanium detector to photon energies between 6 and 120 keV

We have developed a function to describe the response of an 8-cm 3 germanium detector to photon energies as low as 6 keV, going up to 120 keV. Detection effects like the Ge X-ray escape and Compton scattered photons in the neighborhood of the detector were treated. This study was based on the fit of analytic functions to the features of the experimental spectra, thus revealing the parameters and their dependence on the photon energy. Our response function has 13 parameters and its validity is shown by the reproduction of the parameter-generating spectra and through the independent fit of an 152Eu spectrum.