Development of a compact XRF probe using a ring‐type secondary target

Recently, on‐site analysis is being performed in many fields, and the use of compact instruments is required. In this article, we developed a compact x‐ray fluorescence (XRF) probe using a ring‐type secondary target. Employing the ring‐type target, coaxial optical geometry (irradiation and detection) could be achieved. We applied this probe to standard steel materials and standard solutions. In addition, a solid sample in solution was directly measured. As an application of the XRF probe, the monitoring of a chemical reaction was demonstrated that enabled observation of an increase in metallic ions. Copyright © 2008 John Wiley & Sons, Ltd.     

A confocal set‐up for micro‐XRF and XAFS experiments using diamond‐anvil cells

A confocal set‐up is presented that improves micro‐XRF and XAFS experiments with high‐pressure diamond‐anvil cells (DACs). In this experiment a probing volume is defined by the focus of the incoming synchrotron radiation beam and that of a polycapillary X‐ray half‐lens with a very long working distance, which is placed in front of the fluorescence detector. This set‐up enhances the quality of the fluorescence and XAFS spectra, and thus the sensitivity for detecting elements at low concentrations. It efficiently suppresses signal from outside the sample chamber, which stems from elastic and inelastic scattering of the incoming beam by the diamond anvils as well as from excitation of fluorescence from the body of the DAC.     

Transient Lamb waves: comparison between theory and experiment

This paper presents an experimental investigation of the generation of transient Lamb waves inside an immersed plate by a time limited signal. The transient Lamb waves are the solutions of the characteristic equation of the plate for complex frequency and real slowness, in contrast to the leaky Lamb waves, for which the slowness is complex and the frequency is real. By using a large transducer in agreement with the real slowness assumption, the excitation of these transient Lamb waves is observed experimentally both in reflection and transmission for a tone burst excitation. Particular attention is paid to the A0 mode for which the amplitude increases exponentially in time. As a result, the total reflected waveform contains in this case a transient contribution, coming from the generation of the A0 mode, that precedes the forced regime. It is shown that there is a very good agreement between the theoretical and the experimental time exponential amplitude variations of the transient Lamb waves. For the A0 mode, the transient signal is qualitatively explained by a group velocity higher than the phase velocity.     

Longitudinal parametric oscillation in photorefractive sillenites: comparison between theory and experiment

By using an alternative setup for photorefractive parametric oscillation in which wave mixing between the recording beams is avoided it has become possible to make more detailed comparisons with the space-charge wave theory. In the present paper we compare the experimental features of longitudinal parametric oscillation observed in a crystal of Bi₁₂SiO₂₀ with the theoretical predictions. Received: 24 November 1998 / Revised version: 13 January 1999 / Published online: 7 April 1999     

Polariton luminescence and additional boundary conditions: comparison between theory and experiment

Polariton luminescence spectra in semiconductors have been calculated as a function of temperature and impurity trapping rates using a two branch polariton model. Typically, the theoretical spectra show two structures: a peak near the transverse exciton energy and a shoulder near the longitudinal exciton energy. While the lower energy peak is relatively insensitive to the choice of additional boundary conditions (ABC), the higher energy shoulder strongly depends on ABC. The theoretical curves obtained with Pekar's ABC are in quantitative agreement with experimental spectra reported in CdS, CdSe and CuCl. However, significant discrepancies between theory and experiment are found in GaAs and ZnTe.     

Spectrum of three-dimensional photonic quantum-ring microdisk cavities: comparison between theory and experiment

The spectrum of a three-dimensional Rayleigh-Fabry-Perot microdisk cavity of a photonic quantum-ring laser is analyzed for angle-dependent emission modes. It is shown that joint consideration of the Fabry-Perot resonance condition and the whispering-gallery mode boundary condition explains the emitting angles and spectral distribution of the cavity modes well.     

Stability of the parametrically excited damped inverted pendulum: theory and experiment

The parametrically driven, damped, inverted pendulum can be dynamically stabilized in particular regions of the parameter space. The impact of damping on dynamic stabilization can be stabilizing or destabilizing depending on the location in parameter space (i.e., drive frequency and amplitude). Floquet analysis and numerical simulations were used to determine the stable regions. An experiment was conducted that verifies the model. Physical explanations and simple bounding approximations are provided to summarize findings. The utility of the highly damped pendulum results are illustrated by drawing the analogy to dynamic stabilization of the Rayleigh-Taylor instability: it permits ready demonstration that dynamic stabilization is impossible in that system absent surface tension.     

Directed motion for delta-kicked atoms with broken symmetries: comparison between theory and experiment

We report an experimental investigation of momentum diffusion in the delta-function kicked rotor where time symmetry is broken by a two-period kicking cycle and spatial symmetry by an alternating linear potential. We exploit this, and a technique involving a moving optical potential, to create an asymmetry in the momentum diffusion that is due to the classical chaotic diffusion. This represents a realization of a type of Hamiltonian quantum ratchet.     

Absorption and subsequent emission saturation of two-photon excited materials: theory and experiment

The saturation of two-photon absorption and the subsequent photoluminescence of matter under ultrafast laser pulse excitation are studied. For this purpose the experimental results of using two organic conjugated polymers as model substances are discussed theoretically. One model is based on the commonly used hyperbolic approach, whereas the new theory introduced correctly describes the saturation in two-photon spectroscopy and fits the experiment closely. The new model permits microscopic analysis of the absorption saturation process and makes possible an estimate of the two-photon absorption coefficient from the saturation intensity.     

Nondestructive elemental depth profiling of Japanese lacquerware ‘Tamamushi‐nuri’ by confocal 3D‐XRF analysis in comparison with micro GE‐XRF

We have applied recently two XRF (micro x‐ray fluorescence) methods [micro‐Grazing Exit XRF (GE‐XRF) and confocal 3D‐XRF] to Japanese lacquerware ‘Tamamushi‐nuri.’ A laboratory grazing‐exit XRF (GE‐XRF) instrument was developed in combination with a micro‐XRF setup. A micro x‐ray beam was produced by a single capillary and a pinhole aperture. Elemental x‐ray images (2D images) obtained at different analyzing depths by micro GE‐XRF have been reported. However, it was difficult to directly obtain depth‐selective x‐ray spectra and 2D images. A 3D XRF instrument using two independent polycapillary x‐ray lenses and two x‐ray sources (Cr and Mo targets) was also applied to the same sample. 2D XRF images of a Japanese lacquerware showed specific distributions of elements at the different depths, indicating that ‘Tamamushi‐nuri’ lacquerware has a layered structure. The merits and disadvantages of both the micro GE‐XRF and confocal micro XRF methods are discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

A miniature X‐ray tube approach to measuring lead in bone using L‐XRF

Using a miniature X‐ray tube and silicon PiN diode detector, an approach to measuring lead (Pb) in bone phantoms was tested. The X‐ray tube was used to excite L‐line X‐ray fluorescence (L‐XRF) of lead in bone phantoms. The bone phantoms were made from plaster of Paris and dosed with varying quantities of lead. Phantoms were made in two sets with different shapes to model different bone surfaces. One set of bone phantoms was circular in cross‐section (2.5‐cm diameter), the other square in cross‐section (2.2 cm × 2.2 cm). Using an irradiation time of 180 s (real time), five trials were run for each bone phantom. Analysis was performed for both Lα and Lβ lead X‐rays. Based on these calibration trials, (3σ₀/slope) minimum detection limits of 7.4 ± 0.3 µg Pb g^?1 (circular cross‐section) and 8.6 ± 0.6 µg Pb g^?1 (square cross‐section) were determined for the bare bone phantoms. To simulate a more realistic in vivo scenario with soft tissue overlying bone, further trials were performed with a resin material placed between the experimental system and the bone phantom. For the square cross‐section bone phantoms, a layer of resin with a thickness of 1.2 mm was used, and a minimum detection limit of 17 ± 3 µg Pb g^?1 determined. For the circular cross‐section phantoms, a layer of resin with an average thickness of 2.7 mm was used. From these, a more realistic minimum detection limit for in vivo applications (43 ± 7 µg Pb g^?1) was determined. Copyright © 2011 John Wiley & Sons, Ltd.     

Auger and secondary electrons excited by backscattered electrons; An approach to quantitative analysis

The contribution of backscattered electrons (BE) to Auger electrons (AE) and secondary electrons (SE) was studied by depositing Be onto a polycrystalline or deposited Cu substrate. The effects of backscattering on SE and maximum escape depth of SE were obtained by using the so called δ-η method. This method was also applied to the AE and the effects of BE on AE were experimentally evaluated. The AE yield versus primary energy curve which was corrected for BE was compared with other experiments and theories and considerably good agreement was obtained. From this analysis, the excitation efficiencies of AE by primary electrons and by BE could also be obtained. The absolute AE yield of Be (KVV) was estimated by “area” measurements. The changes of plasma losses, the elastic peaks, the energy distribution of BE, and the true SE were also observed as a function of deposited film thickness, and the results are discussed.     

On low frequency sound transmission loss of double sidebranches: a comparison between theory and experiment

The sound power transmission losses of various sidebranches installed along a rectangular duct below the first cut-off frequency of the duct are studied experimentally. Special efforts are made to examine how accurately the plane-wave theory predicts the sound-power transmission loss. Four types of sidebranch impedance are established and their effects to the sound power transmission loss discussed. It is found that under the nonresonant conditions the plane-wave theory can give reasonable prediction when the branch separation is large or the original sound transmission loss of the corresponding single side-branch is weak. The theory always overestimates the sound transmission loss at resonant conditions but gives underestimation if the transmission loss is due to the noise breakout in the sidebranches, especially for short branch separation.     

Leak rate of seals: Effective-medium theory and comparison with experiment

Seals are extremely useful devices to prevent fluid leakage. We present an effective-medium theory of the leak rate of rubber seals, which is based on a recently developed contact mechanics theory. We compare the theory with experimental results for seals consisting of silicon rubber in contact with sandpaper and sand-blasted PMMA surfaces.     

Far-infrared electrodynamics of superconducting Nb: comparison of theory and experiment

Complex conductivity spectra of superconducting Nb are calculated from the first principles in the frequency region around the energy gap and compared with the experimental results. The raw experimental data obtained on thin films can be precisely described by these calculations.     

Semiempirical approach for standardless calibration in µ‐XRF spectrometry using capillary lenses

Quantitative µ‐XRF analysis based on standardless calibration is limited by the lack of information on the shape of the excitation spectrum resulting from using capillary lenses. The measurement of radiation scattered from a sample was used in combination with Monte Carlo simulation of radiation transport to estimate the energy spectral distribution of the excitation radiation. Further, a standardless calibration based on the fundamental parameter method implemented in the IAEA‐QXAS software package was carried out and verified for glass and fused ore certified reference materials. The accuracy and repeatability achieved are reported. Copyright © 2004 John Wiley & Sons, Ltd.