Laser Interferometry Method Research Articles

Mechanoluminescent Film Sensor for Visualizing Ultrasonic Power Distribution

The measurement of the ultrasonic output power emission from transducers is a very important subject because strong ultrasonic power may be harmful to human health during medical diagnosis and therapy. Conventional techniques for measuring ultrasonic power such as radiation force balance method and calorimetry method provides no information on power distribution, laser interferometry method is very expensive and time-consuming. We have demonstrated in previous research that the mechanoluminescent (ML) film can be used as a sensor for visualizing the ultrasonic power distribution of a transducer with a frequency of 20 MHz. In this research, the ultrasonic power distribution of a transducer with a frequency of 6 MHz was also visualized. The results suggest that this method can be used for visualizing the ultrasonic power distribution of transducers with a wide range of frequency.

Laser interferometer for measuring the mass velocity of condensed substances in shock-wave experiments on the TWAC-ITEP proton-radiographic facility

The results of development of a laser interferometer designed for measuring the mass velocity of condensed substances in shock-wave experiments in the field of high-energy-density physics are presented. The interferometer is incorporated in the measuring complex of the TWAC-ITEP proton-radiographic facility. The developed laser system allows measurements of the velocity of free surfaces of samples in shock-wave experiments with an error no worse than 10 m/s for the entire range of velocities attained experimentally. The time resolution of measurements is limited by the response speed of the used PMTs and amounts to 2.5 ns. Combined investigations of shock-wave loading of metal targets and scabbing-fracture and jet-formation processes on free metal surfaces were performed by the proton-radiography and laser-interferometry methods.

Using of laser-interferential methods for analysis the strain-stress state of concrete sleepers

The article is dealt with the results of research of the reinforced concrete element by means of the laser interferometry method.

A light-erosion method for high-pressure dust-gas-plasma flows generation

A light-erosion method for generating high-pressure dust-gas-plasma flows during ultraviolet (λ = 213 nm) laser ablation of a polymeric matrix ((C2F4)n) containing dust particles (thin-wall borosilicate glass microspheres with a ∼15- to 80-μm diameter d) is described. The carrying-out of the dust particles by ionized vapors of the substance of the target matrix, their space-time localization in the gas-plasma flow in a period Δτ ∼ 15–75 μs after the laser exposure up to the further spatial separation of the vaporized substance of the target matrix and the dust particle cloud is recorded by laser interferometry and shadow photography methods. The importance of certain selection of the matrix-dust system for realizing the light-erosion method for generating dust-gas-plasma flows, in particular laser exposure conditions, is shown. When condensed media with a low ionization potential (Al, Ce) are used as a dust component, the proposed method for generating heterogeneous gas-plasma flows can be efficient for their further heating by coherent radiation.

Stark broadening of the hydrogen H γ spectral line at moderately low plasma electron densities

The usage of the hydrogen H γ spectral line for plasma diagnostics, based on Stark broadening at moderately low electron densities (of the order of 10 15 cm −3), is experimentally tested and analyzed. As a plasma source, a low-pressure pulsed arc operating in a He–H gas mixture was used. In this electron density range, the Stark broadening of low-order Balmer lines is small, but the broadening of the higher-order members is considerable. Plasma electron densities were deduced from the halfwidth (FWHM) of the measured H γ profiles in conjunction with the available theoretical results. Further comparison among the electron density values obtained independently using a laser interferometry method and the shape of the He I 4471 Å spectral line was also performed. Upon authors knowledge this is the first study of H γ spectral line undertaken in this way.

Binding and biological properties of lipopolysaccharide Proteus vulgaris O25 (48/57)–chitosan complexes

In this study the negatively charged Proteus vulgaris O25 LPS was chosen for studying interaction with polycationic chitosan. The complex formation of LPS with chitosan was demonstrated using gradient centrifugation and laser interferometry method. The presented results have shown that laser interferometry method is sensitive enough for LPS–chitosan interaction studies. The changing in the ultra structure of LPS during binding with chitosan was observed by electronic microscope. The interaction of P. vulgaris O25 LPS with chitosan was shown to modulate significantly the biological activities of LPS. The toxicity of P. vulgaris O25 LPS decreased 10-fold after forming complexes with chitosan at injection to mice in the similar concentration of endotoxin. The complex LPS–chitosan was less effective than LPS alone in Limulus amabocyte lysate assay. Induction of TNF biosynthesis by LPS–chitosan complex was found to be 65% lower than that by parent LPS at concentration of 100 ng/ml.

Pinched Plasma Study in a Filippov-Type Plasma Focus “Dena”

A characteristic feature of physical processes occurring in pinched plasma is their tendency to generate thermal and nonthermal emissions. In this case, the roles played by plasma compression dynamics such as pinch formation, pinch disruption, expansion, etc., are predominant. In this paper, first, we present some of the experimental results concerning the thermal and nonthermal neutron emissions. Then, a new approach based on some theoretical assumptions and the experimental data for which the pinched plasma density evolution was studied are introduced. In the new approach, the compression dynamics are divided into two phases: plasma compression (thermal) and plasma expansion (nonthermal). For each phase, electron distribution functions such as a parabolic and a hyperbolic are attributed, respectively. Assuming a maximum electron density for each phase and an Abel integral equation (used in laser interferometry method), the fringe density maps in a new Filippov-type plasma focus ldquoDenardquo (25 kV, 288 muF , and 90 kJ) operating in deuterium gas were obtained in the approximation of low collision frequencies.

Piezoelectric coefficients of PMN-0.29PT single crystals in the temperature range of phase transitions

The temperature dependencies of piezoelectric coefficients d 33 and d 31 for Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 multi-domain single crystals, poled in [001]-direction, were investigated. The two samples had x- and y-axes identical with crystallographic [100] and [010] directions respectively, and the second two samples with [−110] and [110] directions. The laser interferometry method was used for the piezoelectrically induced displacement measurement. Piezoelectric coefficients were similar for all samples at room temperature and were roughly d 31 = −550 pC/N and d 33 = 1,100 pC/N. Very high increase of coefficients to values about d 31 = −2,100 pC/N and d 33 = 3,900 pC/N was observed below temperature of the first phase transition 101 °C. The coefficients exhibited only negligible frequency dependence at room temperature. But coefficient increases of about 10–30% as were observed at temperatures about 98 °C for 1 Hz applied field frequency in comparison to values received at 1 kHz. The second phase transition to cubic phase was observed at the temperature 124 °C. The temperature dependencies of dielectric and piezoelectric coefficients were compared too.

Diffusion boundary layers during electrodialysis

A laser interferometry method for direct measurements of thicknesses of diffusion boundary layers is described. The method is employed to explore electromembrane processes. Thicknesses of diffusion boundary layers at below and above limiting diffusion current densities are measured and compared with theoretical values. It is shown that the diffusion boundary layers in narrow channels of electrodialyzer sections overlap one another at high current densities. This radically alters traditional notions concerning the diffusion boundary layer. An interpretation for variations in the thickness of a diffusion boundary layer at current densities in excess of the limiting diffusion current density is given.

Precise Determination of Thermal Expansion Coefficients Observed in 4H-SiC Single Crystals

The coefficient of thermal expansion (CTE) of SiC single crystals is important, in particular, for both designing device assembly and controlling stress distributions in heteroepitaxial thin film structures grown onto SiC substrates. We have performed very precise measurements of the CTEs for SiC single crystals comprising of single 4H polytype PVT-grown in NIPPON Steel Corporation for a temperature range from 123 K to 473 K using a laser interferometry method. This method allows us to directly measure the temperature dependent variation in thermal expansion of the crystal volume with much higher accuracy, and enables us to straightforwardly obtain practical information of CTE data. Furthermore in order to discuss the CTE behavior for a wider temperature range the CTEs at higher temperatures up to 1573 K have been also measured using dilatometer method. The CTE obtained for a nitrogen-doped 4H-SiC single crystal increases continuously from 0.8 ppm/K to 3.1 ppm/K for temperatures of 273 K and 423 K respectively, and further increases to 5.4 ppm/K at 1273 K. We conclude from our data that the CTE variations are likely to be almost independent of the crystal axis directions of SiC from 123 K up to 1573 K.

Thermoconvective instability during electrodialysis

A laser interferometry method is proposed for studying the instability of concentration fields during electrodialysis. It is shown that exceeding the limiting diffusion current density first gives rise to alternating oscillations and then to oscillations at the membrane whose ionogenic groups exhibit the lowest catalytic activity towards the water dissociation reaction. Thereafter, the auto-oscillation process extends over the whole solution volume in the compartments, and dissipative chaos is observed with a further increase in the current density. This instability is presumably a consequence of unevenly distributed heat sources, namely, the Joule heat and the heat of dissociation and recombination of water molecules.

Temperature dependence of piezoelectric coefficients of 0.71 Pb(Mg1/3Nb2/3)O3-0.29 PbTiO3piezoelectric single crystals

Piezoelectrically induced displacements were measured by the laser interferometry method for multidomain-engineered 0.71 Pb(Mg 1/3 Nb 2/3 )O 3 -0.29 PbTiO 3 single crystals in the temperature range 260 K-333 K. It was confirmed that this single crystal has large piezoelectric coefficients if the poling is done along the [001]-direction. Assuming an effective tetragonal symmetry, we determined the piezoelectric d 31 coefficient by measuring the displacement on (100) and (110) crystal faces. Coefficient d 31 =-611 pC/N was calculated for the [100]-direction at room temperature. Its value is higher at 330 K (-820 pC/N). Piezoelectric coefficient d 31 measured on a second sample in the [ 110]-direction exhibited a higher value than the previous one, about -808 pC/N at room temperature, - 1180 pC/N at 331 K and -605 pC/N at 262 K. Temperature dependencies of piezoelectric coefficient d 33 were also investigated. The second sample exhibits about 15% higher d 33 than the first one -1598 pC/N and 1390 pC/N at RT. This difference is 50% -2355 pC/N and 1600 pC/N at 331 K.

Comparison of laser interferometry and radiation force method of measuring ultrasonic power

The aim of this paper is to compare two different methods for the calculation of the ultrasonic output power of underwater transducers: the radiation force balance, which is the standard method, and the laser heterodyne interferometry, which is rather used to depict displacement or velocity distributions of the acoustic field. Here it is shown that the latter can also be used to calculate the acoustic time-average power with an uncertainty of about 22%, the radiation force balance giving an uncertainty of 12% (with 95% confidence). The interferometry experiments performed with two transducers working at 2.25 MHz and 8.25 MHz showed that they produce different acoustic fields (respectively Gaussian and Lorentz-sigmoidal distributions). Taking into account the acoustic field profiles, the acoustic time-average power from interferometry was calculated. It was found very similar to the time-average power measured with the radiation force balance in the plane-wave assumption.

Non-linear properties of PZT ceramics in the wide temperature range

The paper deals with measurements of non-linear properties of Pb(Zr x Ti 1− x )O 3 (PZT) type piezoelectric ceramics in the composition near to the morphotropic phase boundary (MPB). The hydrostatic piezoelectric coefficient d h was determined using the piezoelectric coefficients d 33 and d 31 obtained by resonance method. The temperature dependencies of d 33 and d 31 were compared with ones obtained by laser interferometry method. The differential hydrostatic coefficient d h,diff of PZT ceramics has been measured using a dynamic hydrostatic method. The influence of a DC bias electric field on d h,diff coefficient of a PZT ceramics was studied. Changes of the hydrostatic piezoelectric coefficients d h,diff caused by a bias electric field were observed at various temperatures.

Experimental study on thermal lensing of end-pumped solid-state lasers

A laser interferometry method of measuring the thermal lensing of end-pumped solid-state lasers is proposed. This method provides a way easy to be carried out is real-time, having no influence on laser system, with a high spatial resolution for diagnosing thermal lensing. By this method, thermal lensing of end-pumped Nd:YVO4 laser is studied in detail. And this work provide a means for studying the thermal effects of laser medium and designing lasers of this kind.

Measurements of heat flux distribution toward substrate by means of the LiNbO 3 interferometer, and electron density in a capacitively coupled rf discharge plasma

Measurement of temperature by the laser interferometry method with a LiNbO 3 substrate and determination of heat flux in capacitively coupled plasma (CCP) are described. This method is based on monitoring the variation on nature birefringence with temperature. The CCP is generated at 20 or 40 mm gap length, 100 mTorr argon gas pressure, and 250 cc/min gas flow with an rf input power of 100 W. The rf power is supplied to the lower electrodes through a L-type matching network containing a coupling capacitor and the upper electrode is grounded. The heat flux and electron density distribution possess the same peak characteristics around the maximal point of plasma density under the same experimental conditions. The average diffusion flux for electrons and ions can be calculated from the electron distribution and ambipolar diffusion coefficient. The axial and radial diffusion fluxes are 2.4 × 10 12 and 8.1 × 10 12 #/cm 2 s, respectively. Taking account of the electrode and side area, we find that the total axial flux is 10 times larger than the radial one.

Mutual Effect of Concentration Fields in Solutions of Deionization and Concentration Compartments during Electrodialysis with Ion-Exchange Membranes

The conjugated mass transfer processes in the neighboring compartments of an electrodialyzer are studied theoretically and experimentally. Dependences of the concentration fields, thicknesses of diffusion boundary layers, and maximum solution concentration in the flow on the geometric size, initial concentrations, and the electrolyte feed rate are obtained. A laser interferometry method is employed for experimental modeling and theory verification.

Application of Laser and Holographic Interferometry to Vibrational Investigations of Complex Three-Dimensional Constructions

Investigations of a pipeline of complex configuration made it possible to analyze the possibilities of laser and holographic interferometry methods in studies of strains of three-dimensional constructions under the effect of vibrational loads. The combined application of the holographic method of induced fringes, the method of recording the amplitude–frequency characteristics of object's vibrations using a laser interferometer, and the method of recording holographic interferograms averaged in time was considered. The most dangerous resonance frequencies and pipeline sections, in which its material is subjected to maximum stresses, were revealed.

Electrodialysis Kinetics by Laser Interferometry

A new approach to studying electromembrane systems by the laser interferometry method is proposed. Problems in the electrodialysis kinetics that had been solved by this method are reviewed. These include the determination of the size of diffusion boundary layers, the measurement of concentration profiles of solutions at a concentration polarization of ion-selective membranes in solutions of one and two components in isothermal and nonisothermal conditions, the verification of mathematical models for electrodialysis, and the measurement of local Sherwood numbers. A method for measuring concentration profiles in solutions at the interface with bodies of spherical symmetry following the imposition of a gradient of an electric potential on the system is offered. The results of studying the concentration polarization of an ion exchanger granules are analyzed.

116 レーザホログラフィ干渉による歯車歯面形状の高速検出の可能性について

Conventional method of laser interferometry is useful to know how a tooth flank has form deviation. But its method has a defect that it takes much time to process data of brightness intensity on CCD image sensor and the method can't be introduced in production line for the sake of optical instability of the measuring system. Therefore to detect a form deviation of a cylindrical involute gear tooth, a new measuring system is introduced. Possibility of rapid detection method of a tooth form by using laser holography is investigated.