The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Raynald Gauvin - One of the best experts on this subject based on the ideXlab platform.
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inverse modeling for quantitative x ray microanalysis applied to 2d heterogeneous materials
Ultramicroscopy, 2020Co-Authors: Yu Yuan, Hendrix Demers, Nicolas Brodusch, Xianglong Wang, Raynald GauvinAbstract:Abstract Current quantitative X-Ray microanalysis methods are only available for homogeneous materials. This paper presents a newly developed inverse modeling algorithm to determine both the structure and composition of two-dimensional (2D) heterogeneous materials from a series of X-Ray intensity measurements under different beam energies and beam positions. It utilizes an iterative process of forward modeling to determine the optimal specimen to minimize the relative differences between the simulated and experimental Characteristic X-Ray intensities. The Monte Carlo method is used for the forward modeling to predict the X-Ray radiation for a given specimen and experimental setup. Several examples of applications are presented for different types of samples with one-dimensional (1D) and 2D structures, in which the simulated X-Ray intensities from phantom samples are used as input. Most of the results obtained from our algorithm agree well with the phantom samples. Some discrepancies are found for the voxels located at deeper depths of the 2D samples. And the discrepancies may be attributed to errors from the Monte Carlo simulations and from the variation of the X-Ray range with beam energy. As a proof-of-concept work, this paper confirms the feasibility of our inverse modeling algorithm applied to 2D heterogeneous materials.
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The f-Ratio Method for X-Ray Microanalysis in the SEM
Field Emission Scanning Electron Microscopy, 2017Co-Authors: Nicolas Brodusch, Hendrix Demers, Raynald GauvinAbstract:Quantitative X-Ray microanalysis of bulk samples is usually obtained by measuring the Characteristic X-Ray intensities of each element in a sample and in a corresponding standard of known composition.
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development of a new quantitative x ray microanalysis method for electron microscopy
Microscopy and Microanalysis, 2010Co-Authors: Paula Horny, Eric Lifshin, Helen Campbell, Raynald GauvinAbstract:Quantitative X-Ray microanalysis of thick samples is usually performed by measuring the Characteristic X-Ray intensities of each element in a sample and in corresponding standards. The ratio of the measured intensities from the unknown material to that from the standard is related to the concentration using the ZAF or ϕ(ρz) equations. Under optimal conditions, accuracies approaching 1% are possible. However, all the experimental conditions must remain the same during the sample and standard measurements. This is not possible with cold field emission scanning electron microscopes (FE-SEMs) where beam current can fluctuate around 5% in its stable regime. Very little work has been done on variable beam current conditions (Griffin, B.J. & Nockolds, C.E., Scanning 13, 307-312, 1991), and none relating to cold FE-SEM applications. To address this issue, a new method was developed using a single spectral measurement. It is similar in approach to the Cliff-Lorimer method developed for the analytical transmission electron microscope. However, corrections are made for X rays generated from thick specimens using the ratio of the Characteristic X-Ray intensities of two elements in the same material. The proposed method utilizes the ratio of the intensity of a Characteristic X-Ray normalized by the sum of X-Ray intensities of all the elements measured for the sample, which should also reduce the amplitude of error propagation. Uncertainties in the physical parameters of X-Ray generation are corrected using a calibration factor that must be previously acquired or calculated. As an example, when this method was applied to the calculation of the composition of Au-Cu National Institute of Standards and Technology standards measured with a cold field emission source SEM, relative accuracies better than 5% were obtained.
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a method to measure the effective gas path length in the environmental or variable pressure scanning electron microscope
Scanning, 2002Co-Authors: Raynald Gauvin, Brendan Griffin, C E Nockolds, M R Phillips, David C JoyAbstract:A simple method is described to determine the effective gas path length when incident electrons scatter in the gas above the specimen. This method is based on the measurement of a Characteristic X-Ray line emitted from a region close to the incident beam. From various experimental measurements performed on various microscopes, it is shown that the effective gas path length may increase with the chamber pressure and that it is also often dependent of the type of X-Ray bullet.
Habib Zaidi - One of the best experts on this subject based on the ideXlab platform.
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monte carlo simulation of x ray spectra in diagnostic radiology and mammography using mcnp4c
Physics in Medicine and Biology, 2004Co-Authors: M Shahriari, Saeed Sarkar, M Adib, Habib ZaidiAbstract:The general purpose Monte Carlo N-particle radiation transport computer code (MCNP4C) was used for the simulation of X-Ray spectra in diagnostic radiology and mammography. The electrons were transported until they slow down and stop in the target. Both bremsstrahlung and Characteristic X-Ray production were considered in this work. We focus on the simulation of various target/filter combinations to investigate the effect of tube voltage, target material and filter thickness on X-Ray spectra in the diagnostic radiology and mammography energy ranges. The simulated X-Ray spectra were compared with experimental measurements and spectra calculated by IPEM report number 78. In addition, the anode heel effect and off-axis X-Ray spectra were assessed for different anode angles and target materials and the results were compared with EGS4-based Monte Carlo simulations and measured data. Quantitative evaluation of the differences between our Monte Carlo simulated and comparison spectra was performed using student's t-test statistical analysis. Generally, there is a good agreement between the simulated X-Ray and comparison spectra, although there are systematic differences between the simulated and reference spectra especially in the K-Characteristic X-Rays intensity. Nevertheless, no statistically significant differences have been observed between IPEM spectra and the simulated spectra. It has been shown that the difference between MCNP simulated spectra and IPEM spectra in the low energy range is the result of the overestimation of Characteristic photons following the normalization procedure. The transmission curves produced by MCNP4C have good agreement with the IPEM report especially for tube voltages of 50 kV and 80 kV. The systematic discrepancy for higher tube voltages is the result of systematic differences between the corresponding spectra.
Kazuyoshi Takayama - One of the best experts on this subject based on the ideXlab platform.
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k edge angiography utilizing a tungsten plasma x ray generator in conjunction with gadolinium based contrast media
Radiation Physics and Chemistry, 2006Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Takashi Inoue, Akira Ogawa, Shigehiro Sato, Kazuyoshi Takayama, Yasuomi Hayasi, Jun OnagawaAbstract:Abstract The tungsten plasma flash X-Ray generator is useful in order to perform high-speed enhanced K-edge angiography using cone beams because K-series Characteristic X-Rays from the tungsten target are absorbed effectively by gadolinium-based contrast media. In the flash X-Ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash X-Rays are produced by the discharging. The X-Ray tube is a demountable diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current were approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the Characteristic X-Ray intensities of tungsten K α lines increased. The K α lines were clean, and hardly any bremsstrahlung rays were detected. The X-Ray pulse widths were approximately 110 ns, and the time-integrated X-Ray intensity had a value of approximately 0.35 mGy at 1.0 m from the X-Ray source with a charging voltage of 80 kV. Angiography was performed using a film-less computed radiography (CR) system and gadolinium-based contrast media. In angiography of non-living animals, we observed fine blood vessels of approximately 100 μm with high contrasts.
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Characteristic x ray generator utilizing angle dependence of bremsstrahlung x ray distribution
Japanese Journal of Applied Physics, 2006Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Takashi Inoue, Akira Ogawa, Shigehiro Sato, Kazuyoshi Takayama, Jun OnagawaAbstract:This generator consists of the following components: a constant high-voltage power supply, a filament power supply, a turbomolecular pump, and an X-Ray tube. The X-Ray tube is a demountable diode which is connected to the turbomolecular pump and consists of the following major devices: a molybdenum rod target, a tungsten hairpin cathode (filament), a focusing (Wehnelt) electrode, a polyethylene terephthalate X-Ray window 0.25 mm in thickness, and a stainless-steel tube body. In the X-Ray tube, the positive high voltage is applied to the anode (target) electrode, and the cathode is connected to the tube body (ground potential). In this experiment, the tube voltage applied was from 22 to 36 kV, and the tube current was regulated to within 100 µA by the filament temperature. The exposure time is controlled in order to obtain optimum X-Ray intensity. The electron beams from the cathode are converged to the target by the focusing electrode, and clean K-series Characteristic X-Rays are produced through the focusing electrode without using a filter. The X-Ray intensity was 26.6 µGy/s at 1.0 m from the X-Ray source with a tube voltage of 30 kV and a tube current of 100 µA, and quasi-monochromatic radiography was performed using a computed radiography system.
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enhanced k edge angiography utilizing tantalum plasma x ray generator in conjunction with gadolinium based contrast media
Japanese Journal of Applied Physics, 2005Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Takashi Inoue, Akira Ogawa, Shigehiro Sato, Yasuomi Hayasi, Koji Kimura, Kazuyoshi TakayamaAbstract:The tantalum plasma flash X-Ray generator is useful for performing high-speed enhanced K-edge angiography using cone beams because K-series Characteristic X-Rays from the tantalum target are absorbed effectively by gadolinium-based contrast media. In the flash X-Ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash X-Rays are produced by the discharging. The X-Ray tube is a demountable cold-cathode diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current were approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the K-series Characteristic X-Ray intensities of cerium increased. The K lines were clean and intense, and hardly any bremsstrahlung rays were detected. The X-Ray pulse widths were approximately 100 ns, and the time-integrated X-Ray intensity had a value of approximately 300 µGy at 1.0 m from the X-Ray source with a charging voltage of 80 kV. Angiography was performed using a filmless computed radiography (CR) system and gadolinium-based contrast media. In the angiography of nonliving animals, we observed fine blood vessels of approximately 100 µm with high contrasts.
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quasi monochromatic flash x ray generator utilizing weakly ionized linear copper plasma
Review of Scientific Instruments, 2003Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Toshio Ichimaru, Kazuyoshi Takayama, Yasuomi Hayasi, Rudolf Germer, Hideaki IdoAbstract:In the plasma flash X-Ray generator, a 200 nF condenser is charged up to 50 kV by a power supply, and flash x rays are produced by the discharging. The X-Ray tube is a demountable triode with a trigger electrode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Target evaporation leads to the formation of weakly ionized linear plasma, consisting of copper ions and electrons, around the fine target, and intense Characteristic x rays are produced. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 20 kA. When the charging voltage was increased, the linear plasma formed, and the K-series Characteristic X-Ray intensities increased. The K lines were quite sharp and intense, and hardly any bremsstrahlung rays were detected at all. The X-Ray pulse widths were approximately 700 ns, and the time-integrated X-Ray intensity had a value of approximately 30 μC/kg at 1.0 m ...
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quasi monochromatic radiography using a high intensity quasi x ray laser generator
Medical Imaging 2002: Physics of Medical Imaging, 2002Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Toshio Ichimaru, Yasuomi Hayasi, Tatsumi Usuki, Koetsu Sato, Haruo Obara, Kazuyoshi TakayamaAbstract:High-intensity quasi-monochromatic X-Ray irradiation from the linear plasma target is described. The plasma X-Ray generator employs a high-voltage power supply, a low- impedance coaxial transmission line, a high-voltage condenser with a capacity of about 200 nF, a turbo-molecular pump, a thyristor pulse generator as a trigger device, and a flash X-Ray tube. The high-voltage main condenser is charged up to 55 kV by the power supply, and the electric charges in the condenser are discharged to the tube after triggering the cathode electrode. The flash X-Rays are then produced. The X-Ray tube is of a demountable triode that is connected to the turbo molecular pump with a pressure of approximately 1 mPa. As the electron flows from the cathode electrode are roughly converged to the molybdenum target by the electric field in the tube, the plasma X-Ray source, which consists of metal ions and electrons, forms by the target evaporating. Both the tube voltage and current displayed damped oscillations, and their peak values increased according to increases in the charging voltage. In the present work, the peak tube voltage was almost equal to the initial charging voltage of the main condenser, and the peak current was about 20 kA with a charging voltage of 55 kV. When the charging voltage was increased, the linear plasma X-Ray source formed, and the Characteristic X-Ray intensities of K-series lines increased. The quasi- monochromatic radiography was performed by as new film-less computed radiography system.
Eiichi Sato - One of the best experts on this subject based on the ideXlab platform.
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k edge angiography utilizing a tungsten plasma x ray generator in conjunction with gadolinium based contrast media
Radiation Physics and Chemistry, 2006Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Takashi Inoue, Akira Ogawa, Shigehiro Sato, Kazuyoshi Takayama, Yasuomi Hayasi, Jun OnagawaAbstract:Abstract The tungsten plasma flash X-Ray generator is useful in order to perform high-speed enhanced K-edge angiography using cone beams because K-series Characteristic X-Rays from the tungsten target are absorbed effectively by gadolinium-based contrast media. In the flash X-Ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash X-Rays are produced by the discharging. The X-Ray tube is a demountable diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current were approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the Characteristic X-Ray intensities of tungsten K α lines increased. The K α lines were clean, and hardly any bremsstrahlung rays were detected. The X-Ray pulse widths were approximately 110 ns, and the time-integrated X-Ray intensity had a value of approximately 0.35 mGy at 1.0 m from the X-Ray source with a charging voltage of 80 kV. Angiography was performed using a film-less computed radiography (CR) system and gadolinium-based contrast media. In angiography of non-living animals, we observed fine blood vessels of approximately 100 μm with high contrasts.
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Characteristic x ray generator utilizing angle dependence of bremsstrahlung x ray distribution
Japanese Journal of Applied Physics, 2006Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Takashi Inoue, Akira Ogawa, Shigehiro Sato, Kazuyoshi Takayama, Jun OnagawaAbstract:This generator consists of the following components: a constant high-voltage power supply, a filament power supply, a turbomolecular pump, and an X-Ray tube. The X-Ray tube is a demountable diode which is connected to the turbomolecular pump and consists of the following major devices: a molybdenum rod target, a tungsten hairpin cathode (filament), a focusing (Wehnelt) electrode, a polyethylene terephthalate X-Ray window 0.25 mm in thickness, and a stainless-steel tube body. In the X-Ray tube, the positive high voltage is applied to the anode (target) electrode, and the cathode is connected to the tube body (ground potential). In this experiment, the tube voltage applied was from 22 to 36 kV, and the tube current was regulated to within 100 µA by the filament temperature. The exposure time is controlled in order to obtain optimum X-Ray intensity. The electron beams from the cathode are converged to the target by the focusing electrode, and clean K-series Characteristic X-Rays are produced through the focusing electrode without using a filter. The X-Ray intensity was 26.6 µGy/s at 1.0 m from the X-Ray source with a tube voltage of 30 kV and a tube current of 100 µA, and quasi-monochromatic radiography was performed using a computed radiography system.
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enhanced k edge angiography utilizing tantalum plasma x ray generator in conjunction with gadolinium based contrast media
Japanese Journal of Applied Physics, 2005Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Takashi Inoue, Akira Ogawa, Shigehiro Sato, Yasuomi Hayasi, Koji Kimura, Kazuyoshi TakayamaAbstract:The tantalum plasma flash X-Ray generator is useful for performing high-speed enhanced K-edge angiography using cone beams because K-series Characteristic X-Rays from the tantalum target are absorbed effectively by gadolinium-based contrast media. In the flash X-Ray generator, a 150 nF condenser is charged up to 80 kV by a power supply, and flash X-Rays are produced by the discharging. The X-Ray tube is a demountable cold-cathode diode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Since the electric circuit of the high-voltage pulse generator employs a cable transmission line, the high-voltage pulse generator produces twice the potential of the condenser charging voltage. At a charging voltage of 80 kV, the estimated maximum tube voltage and current were approximately 160 kV and 40 kA, respectively. When the charging voltage was increased, the K-series Characteristic X-Ray intensities of cerium increased. The K lines were clean and intense, and hardly any bremsstrahlung rays were detected. The X-Ray pulse widths were approximately 100 ns, and the time-integrated X-Ray intensity had a value of approximately 300 µGy at 1.0 m from the X-Ray source with a charging voltage of 80 kV. Angiography was performed using a filmless computed radiography (CR) system and gadolinium-based contrast media. In the angiography of nonliving animals, we observed fine blood vessels of approximately 100 µm with high contrasts.
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quasi monochromatic flash x ray generator utilizing weakly ionized linear copper plasma
Review of Scientific Instruments, 2003Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Toshio Ichimaru, Kazuyoshi Takayama, Yasuomi Hayasi, Rudolf Germer, Hideaki IdoAbstract:In the plasma flash X-Ray generator, a 200 nF condenser is charged up to 50 kV by a power supply, and flash x rays are produced by the discharging. The X-Ray tube is a demountable triode with a trigger electrode, and the turbomolecular pump evacuates air from the tube with a pressure of approximately 1 mPa. Target evaporation leads to the formation of weakly ionized linear plasma, consisting of copper ions and electrons, around the fine target, and intense Characteristic x rays are produced. At a charging voltage of 50 kV, the maximum tube voltage was almost equal to the charging voltage of the main condenser, and the peak current was about 20 kA. When the charging voltage was increased, the linear plasma formed, and the K-series Characteristic X-Ray intensities increased. The K lines were quite sharp and intense, and hardly any bremsstrahlung rays were detected at all. The X-Ray pulse widths were approximately 700 ns, and the time-integrated X-Ray intensity had a value of approximately 30 μC/kg at 1.0 m ...
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quasi monochromatic radiography using a high intensity quasi x ray laser generator
Medical Imaging 2002: Physics of Medical Imaging, 2002Co-Authors: Eiichi Sato, Etsuro Tanaka, Hidezo Mori, Toshiaki Kawai, Toshio Ichimaru, Yasuomi Hayasi, Tatsumi Usuki, Koetsu Sato, Haruo Obara, Kazuyoshi TakayamaAbstract:High-intensity quasi-monochromatic X-Ray irradiation from the linear plasma target is described. The plasma X-Ray generator employs a high-voltage power supply, a low- impedance coaxial transmission line, a high-voltage condenser with a capacity of about 200 nF, a turbo-molecular pump, a thyristor pulse generator as a trigger device, and a flash X-Ray tube. The high-voltage main condenser is charged up to 55 kV by the power supply, and the electric charges in the condenser are discharged to the tube after triggering the cathode electrode. The flash X-Rays are then produced. The X-Ray tube is of a demountable triode that is connected to the turbo molecular pump with a pressure of approximately 1 mPa. As the electron flows from the cathode electrode are roughly converged to the molybdenum target by the electric field in the tube, the plasma X-Ray source, which consists of metal ions and electrons, forms by the target evaporating. Both the tube voltage and current displayed damped oscillations, and their peak values increased according to increases in the charging voltage. In the present work, the peak tube voltage was almost equal to the initial charging voltage of the main condenser, and the peak current was about 20 kA with a charging voltage of 55 kV. When the charging voltage was increased, the linear plasma X-Ray source formed, and the Characteristic X-Ray intensities of K-series lines increased. The quasi- monochromatic radiography was performed by as new film-less computed radiography system.
Dale E. Newbury - One of the best experts on this subject based on the ideXlab platform.
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electron excited x ray microanalysis at low beam energy almost always an adventure
Microscopy and Microanalysis, 2016Co-Authors: Dale E. Newbury, Nicholas W. M. RitchieAbstract:Scanning electron microscopy with energy-dispersive spectrometry has been applied to the analysis of various materials at low-incident beam energies, E 0 ≤5 keV, using peak fitting and following the measured standards/matrix corrections protocol embedded in the National Institute of Standards and Technology Desktop Spectrum Analyzer-II analytical software engine. Low beam energy analysis provides improved spatial resolution laterally and in-depth. The lower beam energy restricts the atomic shells that can be ionized, reducing the number of X-Ray peak families available to the analyst. At E 0 =5 keV, all elements of the periodic table except H and He can be measured. As the beam energy is reduced below 5 keV, elements become inaccessible due to lack of excitation of useful Characteristic X-Ray peaks. The shallow sampling depth of low beam energy microanalysis makes the technique more sensitive to surface compositional modification due to formation of oxides and other reaction layers. Accurate and precise analysis is possible with the use of appropriate standards and by accumulating high count spectra of unknowns and standards (>1 million counts integrated from 0.1 keV to E 0 ).
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measures for spectral quality in low voltage x ray microanalysis
Scanning, 2000Co-Authors: Dale E. NewburyAbstract:Characteristic X-Ray production with energetic electrons depends strongly on the overvoltage, the ratio of the incident beam energy to the critical excitation energy for the atomic species of interest. Low-voltage X-Ray microanalysis (beam energy < or = 5 keV) is especially susceptible to artifacts due to sample charging because the overvoltage is low and even slight charging can strongly affect peak intensities. The Duane-Hunt bremsstrahlung limit is a good diagnostic to detect sample charging. Dynamic charging effects, however, can influence spectra despite an apparently satisfactory Duane-Hunt limit. Dynamic charging effects must be examined by time series experiments, or through use of dynamic energy windows continuously measuring count rates placed across the spectrum. When charging is a problem, conductive surface coatings can eliminate the effects. When pristine surfaces must be examined without coating, the use of a conductive grid can control charging so that useful X-Ray spectra can be obtained.