Energy Technology Data Exchange (ETDEWEB)
Dishman, K.L.; Doolin, P.K.; Hoffman, J.F. (Ashland Petroleum Co., Ashland, KY (United States))
1993-07-01
A method of interconversion of dry sieve and laser light scattering particle size values has been developed for cracking catalysts. Values obtained by light scattering techniques were consistently larger than those obtained by dry sieve analysis. The differences were primarily due to lack of sphericity of the particles. The particle size distribution determined by light scattering techniques was based on an average particle diameter. Conversely, the sieve measured the smallest diameter of the particle which can pass through the opening. Microscopic examination of commercial cracking catalysts confirmed their nonuniformity. The sphericity of the catalyst particles decreased as particle size increased. Therefore, the divergence between the laser light scattering and dry sieving value became greater as the catalyst particle size increased.
Blood cell counting and classification by nonflowing laser light scattering method
Yang, Ye; Zhang, Zhenxi; Yang, Xinhui; Jiang, Dazong; Yeo, Joon Hock
1999-11-01
A new non-flowing laser light scattering method for counting and classifying blood cells is presented. A linear charge- coupled device with 1024 elements is used to detect the scattered light intensity distribution of the blood cells. A pinhole plate is combined with the CCD to compete the focusing of the measurement system. An isotropic sphere is used to simulate the blood cell. Mie theory is used to describe the scattering of blood cells. In order to inverse the size distribution of blood cells from their scattered light intensity distribution, Powell method combined with precision punishment method is used as a dependent model method for measurement red blood cells and blood plates. Non-negative constraint least square method combined with Powell method and precision punishment method is used as an independent model for measuring white blood cells. The size distributions of white blood cells and red blood cells, and the mean diameter of red blood cells are measured by this method. White blood cells can be divided into three classes: lymphocytes, middle-sized cells and neutrocytes according to their sizes. And the number of blood cells in unit volume can also be measured by the linear dependence of blood cells concentration on scattered light intensity.
Short-pulsed laser transport in two-dimensional scattering media by natural element method.
Zhang, Yong; Yi, Hong-Liang; Xie, Ming; Tan, He-Ping
2014-04-01
The natural element method (NEM) is extended to solve transient radiative transfer (TRT) in two-dimensional semitransparent media subjected to a collimated short laser irradiation. The least-squares (LS) weighted residuals approach is employed to spatially discretize the transient radiative heat transfer equation. First, for the case of the refractive index matched boundary, LSNEM solutions to TRT are validated by comparison with results reported in the literature. Effects of the incident angle on time-resolved signals of transmittance and reflectance are investigated. Afterward, the accuracy of this algorithm for the case of the refractive index mismatched boundary is studied. Finally, the LSNEM is extended to study the TRT in a two-dimensional semitransparent medium with refractive index discontinuity irradiated by the short pulse laser. The effects of scattering albedo, optical thickness, scattering phase function, and refractive index on transmittance and reflectance signals are investigated. Several interesting trends on the time-resolved signals are observed and analyzed.
Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.
2007-04-24
A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.
Development of density measurement method of negative ion in plasmas using laser Thomson scattering
Yamagata, Yukihiko; Saiho, Hiroatsu; Uchino, Kiichiro; Muraoka, Katsunori
2004-09-01
Measurements of negative ion density in plasmas have been an important subject for many years. We have proposed a new method to measure the negative ion density in plasmas using laser Thomson scattering (LTS), and successfully measured O^- ion density in an radio frequency inductively coupled plasma [1]. In order to ensure the reliability of this technique and to estimate the accuracy, we have measured O^- ion density in the same experimental conditions using the second (SHG) and third harmonics (THG) of a Nd:YAG laser as different laser sources. The LTS spectra measured at pure argon plasma (500 W, 20 mTorr) fitted in a straight line well in both SHG and THG cases. As for the plasma at 500 W in 20 mTorr with Ar/O_2=95%/5%, a clear bump in LTS spectra, which is caused by photo-detached electrons, was observed below 0.9 eV for the SHG case and 2 eV for the case, as predicted by a difference between the electron affinity of O^- ion and the laser photon energy. The electron temperatures, the electron densities and the O^- ion densities, which were obtained from the spectral shape and intensity of both LTS spectra, were in agreement each other within an experimental error. [1] M. Noguchi, K. Ariga, T. Hirao, P. Suanpoot, Y. Yamagata, K. Uchino, K. Muraoka, Plasma Sources Sci. Technol., 11 (2002) 57.
Castellini, P.; Stroppa, L.; Paone, N.
2012-05-01
The paper presents the laser sheet scattered light technique, a fast optical non contact method for measuring internal stress distribution over a cross section of flat glass specimens, designed for closed loop control of glass tempering furnaces. The technique is an evolution of the scattered light method for flat glass residual stress analysis and allows a full thickness stress profile to be measured with a single shot acquisition across a glass plate without any contact. A linearly polarized laser sheet, shaped into a thin plane of parallel light beams, enters orthogonally to the side of the flat glass illuminating its full thickness. Light sheet is orthogonal to the glass surface and travels parallel to it. Stress induced birefringence through the glass affects light polarization, thus scattered light intensity detected at 90° with respect to the polarization of the incident light appears spatially modulated in intensity. A camera aligned orthogonal to the laser light polarization collects an image of fringes whose shape is digitally analyzed to measure the thickness stress state. The paper describes the development of this technique by recalling the scattered light method, then describing its automation by scanning a collimated beam across the glass thickness and finally by showing that the scan method can be substituted by the light sheet method. Light sheet method provides a full field non contact stress measurement across the glass thickness, thus allowing for a fast inspection method, suitable for industrial use. Flat glass items for industrial use have bevelled edges; this does not allow measurements close to glass surface. To solve this limit, experimental data are extrapolated by a symmetrical polynomial fitting and imposing a zero integral to the stress profile. Results on surface stress measured by the laser sheet scattered method are in agreement with those of the automated light scattered method and show a fair agreement with measurement by an
Laser light scattering basic principles and practice
Chu, Benjamin
1994-01-01
Geared toward upper-level undergraduate and graduate students, this text introduces the interdisciplinary area of laser light scattering, focusing chiefly on theoretical concepts of quasielastic laser scattering.
Bäckström, C.; Irvine, S. J. C.; Barrioz, V.
2003-02-01
During metalorganic vapor phase epitaxy (MOVPE) growth of layers of CdS/CdTe, two different sets of data has been extracted in situ at normal incidence, with only a narrow optical access to the sample, using a charge coupled device (CCD) array as the detector. When growing CdTe on Si (0 0 1) in a 2″ single wafer reactor, the growth rate was determined through reflectance interferometry, and film roughness through scattering measurements. A dual wavelength method has been used, where the wavelengths have been chosen to match the CCD detector elements for green and red light in an Agilent HDCS1000 CCD-array. The second wavelength has been used to correct for the absorption/scattering extinction problem of single wavelength interferometry. The relative high intensity of the laser light relative to the ambient minimised the need for filtering of ambient light. The result has been a very simple and robust instrument. The blue light pixels were used for ambient light correction, but could be used for blue laser light detection. The interferograms have been recorded by simple integration of the imaging data sets. The growth rate for both wavelengths was 0.83 nm/s. Through creating a diffused laser spot on a surface, and correlating this to the initial state, roughness data were also accessible. Roughness could be determined quantitatively through correlating scattering data from the interferograms with AFM micrographs of the samples.
Method for pulse control in a laser including a stimulated brillouin scattering mirror system
Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.
2007-10-23
A laser system, such as a master oscillator/power amplifier system, comprises a gain medium and a stimulated Brillouin scattering SBS mirror system. The SBS mirror system includes an in situ filtered SBS medium that comprises a compound having a small negative non-linear index of refraction, such as a perfluoro compound. An SBS relay telescope having a telescope focal point includes a baffle at the telescope focal point which blocks off angle beams. A beam splitter is placed between the SBS mirror system and the SBS relay telescope, directing a fraction of the beam to an alternate beam path for an alignment fiducial. The SBS mirror system has a collimated SBS cell and a focused SBS cell. An adjustable attenuator is placed between the collimated SBS cell and the focused SBS cell, by which pulse width of the reflected beam can be adjusted.
Nakadate, Hiromichi; Sekizuka, Eiichi; Minamitani, Haruyuki
We aimed to study the validity of a new analytical approach that reflected the phase from platelet activation to the formation of small platelet aggregates. We hoped that this new approach would enable us to use the particle-counting method with laser-light scattering to measure platelet aggregation in healthy controls and in diabetic patients without complications. We measured agonist-induced platelet aggregation for 10 min. Agonist was added to the platelet-rich plasma 1 min after measurement started. We compared the total scattered light intensity from small aggregates over a 10-min period (established analytical approach) and that over a 2-min period from 1 to 3 min after measurement started (new analytical approach). Consequently platelet aggregation in diabetics with HbA1c ≥ 6.5% was significantly greater than in healthy controls by both analytical approaches. However, platelet aggregation in diabetics with HbA1c < 6.5%, i.e. patients in the early stages of diabetes, was significantly greater than in healthy controls only by the new analytical approach, not by the established analytical approach. These results suggest that platelet aggregation as detected by the particle-counting method using laser-light scattering could be applied in clinical examinations by our new analytical approach.
Kamataki, K.; Morita, Y.; Shiratani, M.; Koga, K.; Uchida, G.; Itagaki, N.
2012-04-01
We have developed a simple in-situ method for measuring the size distribution (the mean size (mean diameter) and size dispersion) of nano-particles generated in reactive plasmas using the 2 dimensional laser light scattering (2DLLS) method. The principle of the method is based on thermal coagulation of the nano-particles, which occurs after the discharge is turned off, and the size and density of the nano-particles can then be deduced. We first determined the 2D spatial distribution of the density and size of the nano-particles in smaller particle size (a few nm) range than ones deduced from the conventional 2DLLS method. From this 2D dataset, we have for the first time been able to determine the size distribution of nano-particles generated in a reactive plasma without ex-situ measurements.
Thomson scattering from laser plasmas
Energy Technology Data Exchange (ETDEWEB)
Moody, J D; Alley, W E; De Groot, J S; Estabrook, K G; Glenzer, S H; Hammer, J H; Jadaud, J P; MacGowan, B J; Rozmus, W; Suter, L J; Williams, E A
1999-01-12
Thomson scattering has recently been introduced as a fundamental diagnostic of plasma conditions and basic physical processes in dense, inertial confinement fusion plasmas. Experiments at the Nova laser facility [E. M. Campbell et al., Laser Part. Beams 9, 209 (1991)] have demonstrated accurate temporally and spatially resolved characterization of densities, electron temperatures, and average ionization levels by simultaneously observing Thomson scattered light from ion acoustic and electron plasma (Langmuir) fluctuations. In addition, observations of fast and slow ion acous- tic waves in two-ion species plasmas have also allowed an independent measurement of the ion temperature. These results have motivated the application of Thomson scattering in closed-geometry inertial confinement fusion hohlraums to benchmark integrated radiation-hydrodynamic modeling of fusion plasmas. For this purpose a high energy 4{omega} probe laser was implemented recently allowing ultraviolet Thomson scattering at various locations in high-density gas-filled hohlraum plasmas. In partic- ular, the observation of steep electron temperature gradients indicates that electron thermal transport is inhibited in these gas-filled hohlraums. Hydrodynamic calcula- tions which include an exact treatment of large-scale magnetic fields are in agreement with these findings. Moreover, the Thomson scattering data clearly indicate axial stagnation in these hohlraums by showing a fast rise of the ion temperature. Its timing is in good agreement with calculations indicating that the stagnating plasma will not deteriorate the implosion of the fusion capsules in ignition experiments.
Ren, Yatao; Qi, Hong; Yu, Xiaoying; Ruan, Liming
2017-04-01
This study examined the feasibility of using a secondary optimization technique and forward-angle-scattering method to retrieve optical constants (or complex refractive indices) and particle size distribution (PSD) simultaneously. In this work, two continuous wave lasers of different wavelengths were applied to irradiate the participating samples, and the scattered light of samples with different acceptance angles was obtained. First, the scattered signals within different acceptance angles were calculated by solving the radiative transfer equation. Then, the complex refractive index and PSD were retrieved simultaneously by applying quantum particle swarm optimization. However, the estimated results of PSD were inaccurate. Thus, a secondary optimization, which using the directional radiative intensity as input, was performed to improve the accuracy of PSD based on the first optimization process. Four commonly used kinds of monomodal PSD functions, i.e., the Rosin-Rammler, standard Normal, Logarithmic Normal, and Junge distribution, were retrieved. All results showed that the proposed technique can estimate the complex refractive index and PSD accurately.
Energy Technology Data Exchange (ETDEWEB)
Dolmashkin, A A; Dubrovskii, V A; Zabenkov, I V [V.I.Razumovsky Saratov State Medical University, Saratov (Russian Federation)
2012-05-31
The possibility is demonstrated to determine the human blood group by recording the scattering of laser radiation with the help of the digital imaging method. It is experimentally shown that the action of a standing ultrasound wave leads to acceleration of the agglutination reaction of red blood cells, to formation of larger immune complexes of red blood cells, and, as a consequence, to acceleration of their sedimentation. In the absence of agglutination of red blood cells the ultrasound does not enhance the relevant processes. This difference in the results of ultrasound action on the mixture of blood and serum allows a method of blood typing to be offered. Theoretical modelling of the technique of the practical blood typing, carried out on the basis of the elastic light scattering theory, agrees well with the experimental results, which made it possible to plan further improvement of the proposed method. The studies of specific features of sedimentation of red blood cells and their immune complexes were aimed at the optimisation of the sample preparation, i.e., at the search for such experimental conditions that provide the maximal resolution of the method and the device for registering the reaction of red blood cells agglutination. The results of the study may be used in designing the instrumentation for blood group assessment in humans.
Polarization-selectable cavity locking method for generation of laser Compton scattered γ-rays.
Kosuge, Atsushi; Mori, Michiaki; Okada, Hajime; Hajima, Ryoichi; Nagashima, Keisuke
2014-03-24
Nowadays, generation of energy-tunable, monochromatic γ-rays is needed to establish a nondestructive assay method of nuclear fuel materials. The γ-rays are generated by collision of laser photons stored in a cavity and relativistic electrons. We propose a configuration of an enhancement cavity capable of performing polarization control fabricated by a combination of a four-mirror ring cavity with a small spot inside a cavity and a three-mirror of reflective optics as an image inverter for polarization-selectable γ-rays. The image inverter introduces a phase shift of specific polarization which can be used to generate an error signal to lock an optical cavity at a resonance condition.
Study of engineering surfaces using laser-scattering techniques
Indian Academy of Sciences (India)
C Babu Rao; Baldev Raj
2003-06-01
Surface roughness parameters are described. Various surface characterization techniques are reviewed brieﬂy. Interaction of light with the surface is discussed. Laser-scattering methods to characterise the surface are detailed. Practical cases, where laser-scattering methods have provided useful information about surface characteristics, are illustrated.
Matsumoto, Shigeaki
2008-01-01
Tiny dew droplets deposited on a copper plate were controlled constantly by a developed control technique using scattered laser light for studying initial dropwise condensation. The technique employs proportional control combined with shifting movement by an integrator. The droplets were controlled for 60 min at almost constant diameters in a range from only a few micrometers to tens of micrometers and were almost hemispherical in the initial condensation at room temperature.
Laser Pulsing in Linear Compton Scattering
Krafft, Geoffrey; Deitrick, Kirsten; Terzic, Balsa; Kelmar, R; Hodges, Todd; Melnitchouk, W; Delayen, Jean
2016-01-01
Previous work on calculating energy spectra from Compton scattering events has either neglected considering the pulsed structure of the incident laser beam, or has calculated these effects in an approximate way subject to criticism. In this paper, this problem has been reconsidered within a linear plane wave model for the incident laser beam. By performing the proper Lorentz transformation of the Klein-Nishina scattering cross section, a spectrum calculation can be created which allows the electron beam energy spread and emittance effects on the spectrum to be accurately calculated, essentially by summing over the emission of each individual electron. Such an approach has the obvious advantage that it is easily integrated with a particle distribution generated by particle tracking, allowing precise calculations of spectra for realistic particle distributions in collision. The method is used to predict the energy spectrum of radiation passing through an aperture for the proposed Old Dominion University inverse...
Laser scattering measurement for laser removal of graffiti
Tearasongsawat, Watcharawee; Kittiboonanan, Phumipat; Luengviriya, Chaiya; Ratanavis, Amarin
2015-07-01
In this contribution, a technical development of the laser scattering measurement for laser removal of graffiti is reported. This study concentrates on the removal of graffiti from metal surfaces. Four colored graffiti paints were applied to stainless steel samples. Cleaning efficiency was evaluated by the laser scattering system. In this study, an angular laser removal of graffiti was attempted to examine the removal process under practical conditions. A Q-switched Nd:YAG laser operating at 1.06 microns with the repetition rate of 1 Hz was used to remove graffiti from stainless steel samples. The laser fluence was investigated from 0.1 J/cm2 to 7 J/cm2. The laser parameters to achieve the removal effectiveness were determined by using the laser scattering system. This study strongly leads to further development of the potential online surface inspection for the removal of graffiti.
Robust authentication through stochastic femtosecond laser filament induced scattering surfaces
Zhang, Haisu; Tzortzakis, Stelios
2016-05-01
We demonstrate a reliable authentication method by femtosecond laser filament induced scattering surfaces. The stochastic nonlinear laser fabrication nature results in unique authentication robust properties. This work provides a simple and viable solution for practical applications in product authentication, while also opens the way for incorporating such elements in transparent media and coupling those in integrated optical circuits.
Pulsed Laser Nonlinear Thomson Scattering for General Scattering Geometries
Energy Technology Data Exchange (ETDEWEB)
Geoffrey Krafft; A. Doyuran; James Rosenzweig
2005-05-01
In a recent paper it has been shown that single electron Thomson backscatter calculations can be performed including the effects of pulsed high intensity lasers. In this paper we present a more detailed treatment of the problem and present results for more general scattering geometries. In particular, we present new results for 90 degree Thomson scattering. Such geometries have been increasingly studied as X-ray sources of short-pulse radiation. Also, we present a clearer physical basis for these different cases.
Laser pulsing in linear Compton scattering
Krafft, G. A.; Johnson, E.; Deitrick, K.; Terzić, B.; Kelmar, R.; Hodges, T.; Melnitchouk, W.; Delayen, J. R.
2016-12-01
Previous work on calculating energy spectra from Compton scattering events has either neglected considering the pulsed structure of the incident laser beam, or has calculated these effects in an approximate way subject to criticism. In this paper, this problem has been reconsidered within a linear plane wave model for the incident laser beam. By performing the proper Lorentz transformation of the Klein-Nishina scattering cross section, a spectrum calculation can be created which allows the electron beam energy spread and emittance effects on the spectrum to be accurately calculated, essentially by summing over the emission of each individual electron. Such an approach has the obvious advantage that it is easily integrated with a particle distribution generated by particle tracking, allowing precise calculations of spectra for realistic particle distributions "in collision." The method is used to predict the energy spectrum of radiation passing through an aperture for the proposed Old Dominion University inverse Compton source. Many of the results allow easy scaling estimates to be made of the expected spectrum.
The polarization effect of a laser in multiphoton Compton scattering
Liang, Guo-Hua; Lü, Qing-Zheng; Teng, Ai-Ping; Li, Ying-Jun
2014-05-01
The multiphoton Compton scattering in a high-intensity laser beam is studied by using the laser-dressed quantum electrodynamics (QED) method, which is a non-perturbative theory for the interaction between a plane electromagnetic field and a charged particle. In order to analyze in the real experimental condition, a Lorentz transformation for the cross section of this process is derived between the laboratory frame and the initial rest frame of electrons. The energy of the scattered photon is analyzed, as well as the cross sections for different laser intensities and polarizations and different electron velocities. The angular distribution of the emitted photon is investigated in a special velocity of the electron, in which for a fixed number of absorbed photons, the electron energy will not change after the scattering in the lab frame. We obtain the conclusion that higher laser intensities suppress few-laser-photon absorption and enhance more-laser-photon absorption. A comparison between different polarizations is also made, and we find that the linearly polarized laser is more suitable to generate nonlinear Compton scattering.
Directory of Open Access Journals (Sweden)
Yu. V. Golubenko
2014-01-01
Full Text Available Nanoparticles of metals possess a whole series of features, concerned with it’s sizes, this leads to appearing or unusual electromagnetic and optical properties, which are untypical for particulates.An extended method of receiving nanoparticles by means of laser radiation is pulse laser ablation of hard targets in liquid medium.Varying the parameters of laser radiation, such as wavelength of laser radiation, energy density, etc., we can operate the size and shape of the resultant particles.The greatest trend of application in medicine have the nanoparticles of iron, copper, silver, silicon, magnesium, gold and zinc.The subject matter in this work is nanoparticles of copper and gold, received by means of laser ablation of hard targets in liquid medium.The aim of exploration, represented in the article, is the estimation of application of the dynamic light scattering method for determination of the range of nanoparticles sizes in the colloidal solution.For studying of the laser ablation process was chosen the second harmonic of Nd:YAG laser with the wavelength of 532 nm. Special attention was spared for the description of the experiment technique of receiving of nanoparticles.As the liquid medium ethanol and distillation water were used.For exploration of the received colloidal system have been used the next methods: DLS, transmission electron microscopy (TEM and scanning electron microscopy (SEM.The results of measuring by DLS method showed that colloidal solution of the copper in the ethanol is the steady system. Copper nanoparticle’s size reaches 200 nm and is staying in the same size for some time.Received system from the gold’s nanoparticles is polydisperse, unsteady and has a big range of the nanoparticle’s sizes. This fact was confirmed by means of photos, got from the TEM FEI Tecnai G2F20 + GIF and SEM Helios NanoLab 660. The range of the gold nanoparticle’s sizes is from 5 to 60 nm. So, it has been proved that the DLS method is
Rough scattering made by laser on metal and semiconductor surfaces
Shandybina, Galina D.
1994-10-01
Diffraction on metal and semiconductor surfaces during the process of laser irradiation is interesting for microelectronics, power optics and elements of measuring technology. We also present experimental data in changing dynamics of diffuse reflection of copper and bronze mirrors and silicon polished plates during laser irradiation. The impulse of laser radiation from neodymium glass lasts 4 ms. There could be seen the intense reversible increase of diffusion scattering and at the same time decrease of specular component of reflection during laser influence on metal and the appearance of precisely expressed unreturn scattering reflexes during irradiation of semiconductor plates long before the melting threshold. We conduct the quantitative measurements of target thermo-deformation, local deformation of heterogeneities and laser induced effects of the surface with the help of the impulse two-beam interferometry method by indirect measurements of temperature in laser radiation zone. We also established the connection between the dynamic change of scattering of metal and semiconductor with the nature of deformation, such as thermo-deformation of the whole irradiation zone, local deformation of heterogeneities of the surface and defects generated by laser. A physical model of laser induced surface roughness, confirmed by mathematical calculations in the thermoelastic approach, will be also discussed.
Maeda, S.; Sakamoto, K.; Fukuzawa, T.; Shiratani, M.; Watanabe, Y.
1998-10-01
A high sensitive photon-counting laser-light-scattering (PCLLS) method for detection of nano-particles formed in processing plasmas is developed to get information on nucleation and subsequent initial growth of particles. Two different methods are employed to deduce particle-size and -density from time evolution of LLS intensity after turning off the discharge. In one method, size of particles is deduced from their diffusion after turning off the discharge and their density is obtained using the size and absolute LLS intensity.^1. In the other method, density of particles is deduced from their coagulation after turning off the discharge and their size is obtained using the density and absolute LLS intensity. Results obtained by both the methods agree fairly well with each other. Using the developed method, we demonstrate detection of small particles down to a few nm in size and find the corresponding particle density is above 10^10 cm-3 even in low pressure silane rf discharges of low rf power, which are commonly used to deposit high quality a-Si:H films^1M. Shiratani and Y. Watanabe, Rev. Laser Eng. Vol. 26, No. 6 (1998) in press.
Peak intensity measurement of relativistic lasers via nonlinear Thomson scattering
Har-Shemesh, Omri
2011-01-01
The measurement of peak laser intensities exceeding $10^{20}\\;\\text{W/cm$^2$}$ is in general a very challenging task. We suggest a simple method to accurately measure such high intensities up to about $10^{23}\\,\\text{W/cm$^2$}$, by colliding a beam of ultrarelativistic electrons with the laser pulse. The method exploits the specific features of the angular distribution of the radiation emitted by ultrarelativistic electrons via nonlinear Thomson scattering. Initial electron energies well within the reach of laser wake-field accelerators are required, allowing in principle for an all-optical setup. Accuracies of the order of 10% are envisaged.
Electron scattering by molecules. II - Experimental methods and data
Trajmar, S.; Chutjian, A.; Register, D. F.
1983-01-01
Experimental techniques for measuring electron-molecule collision cross sections are briefly summarized. A survey of the available experimental cross section data is presented. The emphasis here is on elastic scattering, rotational, vibrational and electronic excitations, total electron scattering, and momentum transfer in the few eV to few hundred eV impact energy range. Reference is made to works concerned with high energy electron scattering, innershell and multi-electron excitations, conicidence methods and electron scattering in laser fields.
HeNe-laser light scattering by human dental enamel
Zijp, [No Value; tenBosch, JJ; Groenhuis, RAJ
1995-01-01
Knowledge of the optical properties of tooth enamel and an understanding of the origin of these properties are necessary for the development of new optical methods for caries diagnosis and the measurement of tooth color. We measured the scattering intensity functions for HeNe-laser light of 80- to 1
Miniature instrumentation for laser light scattering experiments
Brown, Robert G. W.
1989-01-01
Traditional optical systems for photon correlation spectroscopy and laser anemometry have relied upon physically large and fairly expensive lasers, bulk-optics such as lenses of a few inches diameter, large mechanical mounts and carefully selected, fragile and bulky photon counting photomultiplier detectors. In some cases, experimental fluid dynamics at a desired position in a flow, perhaps deep inside complex machinery, is physically impossible or very difficult. Similar problems exist with photon correlation spectroscopy, e.g., remote and heterodyne experiments. Various optical and electro optical components were investigated and characterized with the aim of replacing existing photon correlation laser spectroscopy and anemometry techniques in miniaturized form, and with significant cost reduction. Very recently, a range of miniature, modular light scattering systems were constructed from little solid state optical and electro optical components, and experimentally verified measurement performance comparable to standard lab photon correlation spectroscopy and laser anemometry equipment.
Predicting the strength of sawn wood by tracheid laser scattering
National Research Council Canada - National Science Library
Brännström, Mattias; Manninen, Janne; Oja, Johan
2008-01-01
An industrial laser light scattering scanner, designed to detect the spiral grain angle of logs by the light scattering along the grain, was used on two large samples of Norway spruce (Picea abies (var. Karst...
Dynamic light scattering on bioconjugated laser generated gold nanoparticles.
Zimbone, Massimo; Baeri, Pietro; Calcagno, Lucia; Musumeci, Paolo; Contino, Annalinda; Barcellona, Maria Luisa; Bonaventura, Gabriele
2014-01-01
Gold nanoparticles (AuNPs) conjugated to DNA are widely used for biomedical targeting and sensing applications. DNA functionalization is easily reached on laser generated gold nanoparticles because of their unique surface chemistry, not reproducible by other methods. In this context, we present an extensive investigation concerning the attachment of DNA to the surface of laser generated nanoparticles using Dynamic Light Scattering and UV-Vis spectroscopy. The DNA conjugation is highlighted by the increase of the hydrodynamic radius and by the UV-Vis spectra behavior. Our investigation indicates that Dynamic Light Scattering is a suitable analytical tool to evidence, directly and qualitatively, the binding between a DNA molecule and a gold nanoparticle, therefore it is ideal to monitor changes in the conjugation process when experimental conditions are varied.
Dynamic light scattering on bioconjugated laser generated gold nanoparticles.
Directory of Open Access Journals (Sweden)
Massimo Zimbone
Full Text Available Gold nanoparticles (AuNPs conjugated to DNA are widely used for biomedical targeting and sensing applications. DNA functionalization is easily reached on laser generated gold nanoparticles because of their unique surface chemistry, not reproducible by other methods. In this context, we present an extensive investigation concerning the attachment of DNA to the surface of laser generated nanoparticles using Dynamic Light Scattering and UV-Vis spectroscopy. The DNA conjugation is highlighted by the increase of the hydrodynamic radius and by the UV-Vis spectra behavior. Our investigation indicates that Dynamic Light Scattering is a suitable analytical tool to evidence, directly and qualitatively, the binding between a DNA molecule and a gold nanoparticle, therefore it is ideal to monitor changes in the conjugation process when experimental conditions are varied.
Broadband Brillouin Scatter from CO2-Laser-Target Interactions
Mitchel, G. R.; Grek, B.; Johnston, T. W.; Pépin, H.; Church, P.; Lavigne, P.; Martin, F.; Décoste, R.
1982-05-01
Light scattered near the incident wavelength from CO2 laser-solid target interactions in oblique incidence shows the spectral signature of Brillouin scattering both in the backward and in the near specular directions. This instability is apparently seeded by broadband scatter from the critical density surface and then amplified in the underdense plasma. 60% of the incident light is scattered, and the Brillouin contribution to total scatter may be large if the source is also large.
High-Power Laser Pulse Recirculation for Inverse Compton Scattering-Produced Gamma-Rays
Energy Technology Data Exchange (ETDEWEB)
Jovanovic, I; Shverdin, M; Gibson, D; Brown, C
2007-04-17
Inverse Compton scattering of high-power laser pulses on relativistic electron bunches represents an attractive method for high-brightness, quasi-monoenergetic {gamma}-ray production. The efficiency of {gamma}-ray generation via inverse Compton scattering is severely constrained by the small Thomson scattering cross section. Furthermore, repetition rates of high-energy short-pulse lasers are poorly matched with those available from electron accelerators, resulting in low repetition rates for generated {gamma}-rays. Laser recirculation has been proposed as a method to address those limitations, but has been limited to only small pulse energies and peak powers. Here we propose and experimentally demonstrate an alternative method for laser pulse recirculation that is uniquely capable of recirculating short pulses with energies exceeding 1 J. Inverse Compton scattering of recirculated Joule-level laser pulses has a potential to produce unprecedented peak and average {gamma}-ray brightness in the next generation of sources.
Thomson scattering from laser induced plasma in air
Energy Technology Data Exchange (ETDEWEB)
Dzierzega, K; Mendys, A [Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Krakow (Poland); Pellerin, S; Thouin, E [GREMI - site de Bourges, Universite d' Orleans, rue Gaston Berger BP 4043, 18028 Bourges (France); Travaille, G; Bousquet, B; Canioni, L [Centre de Physique Moleculaire Optique et Hertzienne, Universite Bordeaux I, 351 Cours de la Liberation, 33405 Talence CEDEX (France); Pokrzywka, B, E-mail: krzysztof.dzierzega@uj.edu.p [Mt. Suhora Observatory, Pedagogical University of Cracow, ul. Podchorazych 2, 30-084 Krakow (Poland)
2010-05-01
The laser induced plasma in air produced by 6 ns, 532 nm Nd:YAG pulses with 25 mJ energy was studied using the Thomson scattering method and plasma imaging techniques. Plasma images and Thomson scattered spectra were registered at delay times ranging from 150 ns to 1 {mu}s after the breakdown pulses. The electron density and temperature, as determined in the core of the plasma plume, were found to decrease from 7.4 x 10{sup 17} cm{sup -3} to about 1.03 x 10{sup 17} cm{sup -3} and from 100 900 K to 22 700 K. The highly elevated electron temperatures are the result of plasma heating by the second, probe pulse in the Thomson scattering experiments.
Eigenstates of Laser-Assisted Scattering in a Noninertial Frame
Institute of Scientific and Technical Information of China (English)
FENG Zi-Min; LI Shu-Min
2005-01-01
In a rotating noninertial frame, we investigate the eigenstates of the time-dependent problem for electronnucleus scattering assisted by a circularly polarized laser field. Numerical results of probability distribution, quantum potential, and current density are discussed. An approximate expression of scattering cross section for low laser frequency is given.
Energy Technology Data Exchange (ETDEWEB)
Noda, S.; Onodera, K.; Kamitakahara, Y.; Onuma, Y. [Toyohashi University of Technology, Aichi (Japan)
1997-02-25
The new seeding method of MgO scattering particles based on a laser sheet method was developed, and the near-field structure of jet diffusion flame was studied. This method adds MgO particles (0.2-1.0{mu}m in size) produced by oxidation reaction as scattering particles through combustion of a Mg ribbon in a passage. Since this seeding method of scattering particles can add extreme-densely particles, this method is applicable to not only laser sheet visualization but also laser Doppler velocimeter and concentration measurement. In non-combustion jet formed over a contraction nozzle, coherent vortices are formed in the near field within nearly 8000 in Reynolds number, and the coherent vortices enhance mixing of fuel and air in the process of their linear and nonlinear growth. In the case over 8000 in Reynolds number, the small-scale short-lifetime coherent vortices are formed in the initial development stage of mixed layers, and the whole jet is dominated by irregular turbulent mixing after collapse of the coherent vortices. 14 refs., 8 figs., 1 tab.
Photon Acceleration of Laser-plasma Based on Compton Scattering
Institute of Scientific and Technical Information of China (English)
HAO Dong-shan; XIE Hong-jun
2006-01-01
The one-dimensional electron density disturbance is studied by using the inelastic collision model of the relativity electron and photon group, the relativity theory, the momentum equation and the continuity equation, which is generated by a driving laser pulse and scattered laser pulse propagating through a tenuous plasma, and the electron density disturbance is closely associated with the incident laser and scattering laser. The electron plasma wave(EPW)is formed by the propagation of the electron density disturbance. Owing to the action of EPW, the increasing of the frequency of the photons in the incident laser pulses that there is a distance with the driving laser pulses is studied by using optical metric. The results show that it is possible that the photon will gain higher energy from the EPW when photon number is decreased and one-photon Compton scattering enters, the photon will be accelerated.
Electron-atom scattering in a circularly polarized laser field
Cionga, Aurelia; Zloh, Gabriela; 10.1103/PhysRevA.61.063417
2013-01-01
We consider electron-atom scattering in a circularly polarized laser field at sufficiently high electron energies, permitting to describe the scattering process by the first order Born approximation. Assuming the radiation field has sufficiently moderate intensities, the laser-dressing of the hydrogen target atom in its ground state will be treated in second order perturbation theory. Within this approximation scheme, it is shown that the nonlinear differential cross sections of free-free transitions do neither depend on the {\\it dynamical phase} $\\phi$ of the radiative process nor on the {\\it helicity} of the circularly polarized laser light. Relations to the corresponding results for linear laser polarization are established.
Laser light scattering in a laser-induced argon plasma: Investigations of the shock wave
Energy Technology Data Exchange (ETDEWEB)
Pokrzywka, B. [Obserwatorium Astronomiczne na Suhorze, Uniwersytet Pedagogiczny, ulica Podchorazych 2, 30-084 Krakow (Poland); Mendys, A., E-mail: agata.mendys@uj.edu.pl [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Dzierzega, K.; Grabiec, M. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Pellerin, S. [GREMI, site de Bourges, Universite d' Orleans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France)
2012-08-15
Shock wave produced by a laser induced spark in argon at atmospheric pressure was examined using Rayleigh and Thomson scattering. The spark was generated by focusing a laser pulse from the second harmonic ({lambda} = 532 nm) of a nanosecond Nd:YAG laser using an 80 mm focal length lens, with a fluence of 2 kJ{center_dot}cm{sup -2}. Images of the spark emission were recorded for times between 30 ns and 100 {mu}s after the laser pulse in order to characterize its spatial evolution. The position of the shock wave at several instants of its evolution and for several plasma regions was determined from the Rayleigh-scattered light of another nanosecond Nd:YAG laser (532 nm, 40 J{center_dot}cm{sup -2} fluence). Simultaneously, Thomson scattering technique was applied to determine the electron density and temperature in the hot plasma core. Attempts were made to describe the temporal evolution of the shock wave within a self-similar model, both by the simple Sedov-Taylor formula as well as its extension deduced by de Izarra. The temporal radial evolution of the shock position is similar to that obtained within theory taking into account the counter pressure of the ambient gas. Density profiles just behind the shock front are in qualitative agreement with those obtained by numerically solving the Euler equations for instantaneous explosion at a point with counter pressure. - Highlights: Black-Right-Pointing-Pointer We investigated shock wave evolution by Rayleigh scattering method. Black-Right-Pointing-Pointer 2D map of shockwave position for several times after plasma generation is presented. Black-Right-Pointing-Pointer Shock wave evolution is not satisfactorily described within self-similar models. Black-Right-Pointing-Pointer Evolution of shock position similar to theory taking into account counter pressure. Black-Right-Pointing-Pointer Density profile behind the shock similar to numerical solution of Euler equations.
Mott scattering of polarized electrons in a strong laser field
Manaut, B; Attaourti, Y
2004-01-01
We present analytical and numerical results of the relativistic calculation of the transition matrix element $S_{fi}$ and differential cross section for Mott scattering of initially polarized Dirac particles (electrons) in the presence of strong laser field with linear polarization. We use exact Dirac-Volkov wave functions to describe the dressed electrons and the collision process is treated in the first Born approximation. The influence of the laser field on the degree of polarization of the scattered electron is reported.
Laser-Assisted Elastic Electron Scattering from Argon
Institute of Scientific and Technical Information of China (English)
HU Qiu-Bo; SUN Jin-Feng
2009-01-01
The second Born approximation (SBA) theory is applied to the study of electron-atom scattering in the presence of a CO2 laser field. The absolute differential cross sections of e-At scattering are calculated with multiphoton exchange in two special scattering geometries G1 (for small-angle scattering) and G2. For geometry G1, compared with the results of two different model potentials for electron elastic scattering by atoms, it is found that electronatom polarization potential plays an important role in laser-assisted electron-atom scattering. Some calculational results in geometries G2 are given. Our results are found to be better than other theoretical results as compared with the experimental data in geometries G1 and G2.
Laser Thomson scattering in a pulsed atmospheric arc discharge
Sommers, Bradley; Adams, Steven
2015-09-01
Laser scattering measurements, including Rayleigh, Raman, and Thomson scattering have been performed on an atmospheric pulsed arc discharge. Such laser scattering techniques offer a non-invasive diagnostic to measure gas temperature, electron temperature, and electron density in atmospheric plasma sources, particularly those with feature sizes approaching 1 mm. The pulsed discharge is ignited in a pin to pin electrode geometry using a 6 kV pulse with 10 ns duration. The electrodes are housed in a glass vacuum chamber filled with argon gas. The laser signal is produced by a Nd:Yag laser supply, repetitively pulsed at 10 Hz and frequency quadrupled to operate at 266 nm. The scattered laser signal is imaged onto a triple grating spectrometer, which is used to suppress the Rayleigh scatter signal in order to measure the low amplitude Thomson and Raman signals. Preliminary results include measurements of electron temperature and electron density in the plasma column taken during the evolution of the discharge. The laser system is also used to measure the Rayleigh scattering signal, which provides space and time resolved measurements of gas temperature in the arc discharge.
Thomson scattering of polarized photons in an intense laser beam
Energy Technology Data Exchange (ETDEWEB)
Byung Yunn
2006-02-21
We present a theoretical analysis of the Thomson scattering of linearly and circularly polarized photons from a pulsed laser by electrons. The analytical expression for the photon distribution functions presented in this paper should be useful to designers of Thomson scattering experiments.
Enhanced light scattering in Si nanostructures produced by pulsed laser irradiation
Energy Technology Data Exchange (ETDEWEB)
Sberna, P. M.; Scapellato, G. G.; Boninelli, S.; Miritello, M.; Crupi, I.; Bruno, E.; Privitera, V.; Simone, F.; Mirabella, S. [MATIS IMM-CNR and Dipartimento di Fisica e Astronomia, Università di Catania, via S. Sofia 64, 95123 Catania (Italy); Piluso, N. [IMM-CNR, VIII strada 5, 95121 Catania (Italy)
2013-11-25
An innovative method for Si nanostructures (NS) fabrication is proposed, through nanosecond laser irradiation (λ = 532 nm) of thin Si film (120 nm) on quartz. Varying the laser energy fluences (425–1130 mJ/cm{sup 2}) distinct morphologies of Si NS appear, going from interconnected structures to isolated clusters. Film breaking occurs through a laser-induced dewetting process. Raman scattering is enhanced in all the obtained Si NS, with the largest enhancement in interconnected Si structures, pointing out an increased trapping of light due to multiple scattering. The reported method is fast, scalable and cheap, and can be applied for light management in photovoltaics.
Electron Scattering by Ar Atoms in a Laser Field
Institute of Scientific and Technical Information of China (English)
ZHANG Sheng-Hai; QIAN Xing-Zhong; JIANG Yu-Hai; SUN Jin-Feng
2000-01-01
The differentialcross sections of electron-Ar atom scattering for free-free transition with one and two photons absorption in the presence of CO2 laser field is obtained by the second Born approximation, the direction of laser polarization being perpendicular to the change of electron momentum. Compared with the more recent available experimental data, the present results are very good.
Plasma Jet Interaction with Thomson Scattering Probe Laser
Byvank, Tom; Banasek, Jacob; Potter, William; Kusse, Bruce
2016-10-01
Thomson scattering systems can diagnose plasma temperatures and velocities. When probing a plasma jet with the Thomson scattering laser, we observe a laser-plasma interaction that inputs energy into the plasma jet. The absorbed energy causes a bubble of low density ( 5*1017 cm-2) in the jet (unperturbed 1018 cm-2). A pulsed power machine (1 MA peak current, 100 ns rise time) with a radial foil (15 μm thick Al) configuration generates the plasma jet. We compare the effects of using 10 J and 1 J laser energies, for which the 10 J laser is a larger perturbation. We discuss how the interaction affects the Thomson scattering temperature and velocity measurements. Work supported by National Nuclear Security Administration (NNSA) Stewardship Sciences Academic Programs under Department of Energy (DOE) Cooperative Agreement DE-NA0001836 and National Science Foundation (NSF) Grant PHY-1102471.
Investigations of laser-induced plasma in argon by Thomson scattering
Energy Technology Data Exchange (ETDEWEB)
Mendys, A., E-mail: agata.mendys@uj.edu.pl [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Dzierzega, K.; Grabiec, M. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, ulica Reymonta 4, 30-059 Krakow (Poland); Pellerin, S. [GREMI - site de Bourges, Universite d' Orleans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France); Pokrzywka, B. [Obserwatorium Astronomiczne na Suhorze, Uniwersytet Pedagogiczny, ulica Podchorazych 2, 30-084 Krakow (Poland); Travaille, G.; Bousquet, B. [Centre de Physique Moleculaire Optique et Hertzienne, Universite Bordeaux 1, 351 Cours de la Liberation, 33405 Talence CEDEX (France)
2011-09-15
The Thomson scattering method was applied to quantify the electron number density and temperature of a laser spark formed in argon. The laser spark was generated by focusing a 15 mJ beam from the second harmonic ({lambda}{sub L} = 532 nm) of a nanosecond Nd:YAG laser with an 80 mm focal length lens. Images of the spark emission were obtained for times between 1 ns and 20 {mu}s after the laser pulse in order to characterize its spatial evolution. The electron density and temperature for the core of the plasma plume at different instants of its evolution were determined from the Thomson scattered spectra of another nanosecond Nd:YAG laser (532 nm, 10 to 60 mJ/pulse). In the time interval between 400 ns and 10 {mu}s between the laser induced plasma and Thomson scattering probe pulses, we found n{sub e} and T{sub e} to decrease from 4.3 Multiplication-Sign 10{sup 23} m{sup -3} to 2.4 Multiplication-Sign 10{sup 22} m{sup -3} and from 50 700 K to 11 100 K, respectively. Special care was paid to the plasma disturbance by the probe laser pulse in Thomson scattering experiments due to absorption of laser photons by electrons through the inverse bremsstrahlung process.
Development of 3D control of a tiny dew droplet by scattered laser light
Matsumoto, Shigeaki
2009-06-01
In order to study dropwise condensation on a metal plate, the method for controlling a tiny dew droplet deposited on a copper plate has been developed by using scattered laser light. The method employed the proportional control combined with shifting movement by an integrator to control the intensity of the scattered laser light constantly. Also, the control simulation of the method has been developed to confirm the usefulness of the method and the simulated three-dimensional shape of controlled dew droplet was obtained with the control action. A tiny thin dew droplet, of which the diameter was of handreds micrometers and the mass was about 10-7 g, was controlled in the atmosphere at room temperature for 60 minutes at the preset level of the intensity of scattered laser light and the three-dimensional shape of the controlled dew droplet was shown from the interference fringes.
Raman forward scattering of high-intensity chirped laser pulses
Energy Technology Data Exchange (ETDEWEB)
Schroeder, C.B.; Esarey, E.; Shadwick, B.A.; Leemans, W.P.
2002-06-23
Raman forward scattering of a high-intensity, short-duration, frequency-chirped laser pulse propagating in an underdense plasma is examined. The growth of the direct forward scattered light is calculated for a laser pulse with a linear frequency chirp in various spatio-temporal regimes. This includes a previously undescribed regime of strongly-coupled four-wave nonresonant interaction, which is important for relativistic laser intensities. In all regimes of forward scattering, it is shown that the growth rate increases (decreases) for positive (negative) frequency chirp. The effect of chirp on the growth rate is relatively minor, i.e., a few percent chirp yields few percent changes in the growth rates. Relation of these results to recent experiments is discussed.
Deharak, B. A.; Savich, J. L.; Roberts, H. M.; Brown, E. G.; McGill, M. R.; Kim, B. N.; Weaver, C. M.; Martin, N. L. S.
2016-05-01
We have conducted a series of Monte Carlo simulations of laser assisted free-free scattering experiments. The simulations make use of Kroll-Watson approximation to account for the effects of the laser field on the scattering process. The parameters for these simulations are believed to mimic the experimental conditions of the work reported by Wallbank and Holmes, particularly the target number density. The simulations account for the effects multiple scattering (i.e., the scattering of a single incident electron from multiple target atoms). We present a comparison of the results of these simulations to the experimental results of Wallbank and Holmes. This work was supported by the National Science Foundation under Grants Nos. PHY-0855040 (NLSM) and PHY-1402899 (BAd).
Kotkin, G L; Telnov, V I
2003-01-01
In a number of papers an attractive method of laser polarization of electrons (positrons) at storage rings or linear colliders have been proposed. We show that these suggestions are incorrect and based on errors in simulation of multiple Compton scattering and in calculation of the Compton spin-flip cross sections. We argue that the equilibrium polarization in this method is zero.
Design of an embedded sensor system for measuring laser scattering on blood cells
Iosifidis, C.; Katsaliaki, K.; Kollensperger, P.; Kiziroglou, M. E.
2017-05-01
In this paper, a sensor system architecture for laboratory and in-vivo light scattering studies on blood cells is presented. It aims at correlating Mie scattering to compositional and physiological information of blood cells towards a non-invasive blood-cell counting sensor. An overview of previously reported experimental techniques on light scattering from blood cells is presented. State-of-the-art methods such as differential pulse measurements, vessel pressure optimization identified as promising for enhancing the scattering signal in such measurements. Indicative simulations of Mie scattering by blood cells are presented, illustrating the potential for distinguishing among cells and identifying size distribution. A prototype sensor system based on a 640-660 nm laser light source and a photo diode array is implemented and programmed to obtain mean amplitude and scattering angle measurements.
Zabarylo, U.; Minet, O.
2010-01-01
Investigations on the application of optical procedures for the diagnosis of rheumatism using scattered light images are only at the beginning both in terms of new image-processing methods and subsequent clinical application. For semi-automatic diagnosis using laser light, the multispectral scattered light images are registered and overlapped to pseudo-coloured images, which depict diagnostically essential contents by visually highlighting pathological changes.
Collective Thomson Scattering from Laser-Produced Plasmas
Institute of Scientific and Technical Information of China (English)
白波; 郑坚; 俞昌旋; 刘万东; 蒋小华; 袁晓东; 郑志坚; 徐冰; 向勇; 赵春茁
2001-01-01
Time-resolved Thomson scattering was successfully performed to diagnose the parameters (ZTe, Ue and Ui) of laser-produced gold plasma. The results show that the collisionless dynamic form factor is accurate enough to be used for reducing the plasma parameters from the experimental data.
Arbitrarily shaped scatterer by moment method
Shu, Yongze; Ma, Feng
1988-12-01
The calculation of radar cross section (RCS) for an arbitrarily shaped and perfectly conducting scatterer with small electric size has been studied by moment method. The starting point of this paper is the reaction integral equation (RIE). Polygonal plates are used to construct models of realistic structures and to segment every plate into modes automatically. Overlap modes can be obtained between the connecting intersecting plates. The piecewise-sinusoidal modes have been chosen as expansion and testing functions. From RIE, the matrix equation IZ = V can be derived. The scattering field and RCS of the scatterer can be obtained. The method has advantages of simplicity and flexibility of input, versatility, and accuracy. The calculating results of RCS for a few scatterers with different shapes, including a realistic rocket, have been given. The results are in good agreement with those published abroad.
INVERSE SCATTERING PROBLEMS BY SINGULAR SOURCE METHODS
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
The inverse scattering problems are to detect the property of obstacles from the measurements outside the obstacles. One of important research areas in this topic is the recovery of boundary property for impenetrable obstacles. In this paper, we would like to give a brief review about the recently developed singular source methods. There are three different methods in this category, namely, linear sampling method, pointsource method and probe method. We also present some recent new results about the probe method.
Supercontinuum Light Sources for Hyperspectral Subsurface Laser Scattering
DEFF Research Database (Denmark)
Nielsen, Otto Højager Attermann; Dahl, Anders Lindbjerg; Larsen, Rasmus;
2011-01-01
A materials structural and chemical composition influences its optical scattering properties. In this paper we investigate the use of subsurface laser scattering (SLS) for inferring structural and chemical information of food products. We have constructed a computer vision system based on a super......A materials structural and chemical composition influences its optical scattering properties. In this paper we investigate the use of subsurface laser scattering (SLS) for inferring structural and chemical information of food products. We have constructed a computer vision system based...... on a supercontinuum laser light source and an Acousto- Optic Tunable Filter (AOTF) to provide a collimated light source, which can be tuned to any wavelength in the range from 480 to 900 nm. We present the newly developed hyperspectral vision system together with a proof-of-principle study of its ability...... to discriminate between dairy products with either similar chemical or structural composition. The combined vision system is a new way for industrial food inspection allowing non-intrusive online process inspection of parameters that is hard with existing technology....
Direct methods of analyzing diffuse scattering
Energy Technology Data Exchange (ETDEWEB)
Georgopoulos, P.; Cohen, J.B.
1979-07-01
Methods of analysis of diffuse scattering have now reached the stage where thee are well tested and documented standard procedures for a variety of materials, and software, for both x-rays and neutrons. These methods and their meaning Are briefly reviewed.
Impulsive rotational Raman scattering of N2 by a remote "air laser" in femtosecond laser filament
Ni, Jielei; Zhang, Haisu; Zeng, Bin; Yao, Jinping; Li, Guihua; Jing, Chenrui; Xie, Hongqiang; Xu, Huailiang; Cheng, Ya; Xu, Zhizhan
2014-01-01
We report on experimental realization of impulsive rotational Raman scattering from neutral nitrogen molecules in a femtosecond laser filament using an intense self-induced white-light seeding "air laser" generated during the filamentation of an 800 nm Ti: Sapphire laser in nitrogen gas. The impulsive rotational Raman fingerprint signals are observed with a maximum conversion efficiency of ~0.8%. Our observation provides a promising way of remote identification and location of chemical species in atmosphere by rotational Raman scattering of molecules.
Online monitoring of food processes using subsurface laser scattering
DEFF Research Database (Denmark)
Carstensen, Jens Michael; Møller, Flemming
Online monitoring of physical parameters during food production is not a trivial task, but promising results can often be obtained with Subsurface Laser Scattering (SLS). The first SLS instruments are on the market today, and studies are needed to asses the potential of the technology. SLS can...... monitor particle changes and gelation formation in a fast and non-invasive manner during production of most food products. SLS is correlated to classical particle sizing parameters, i.e. size, number of light scatters and refractive index, as well as sensoric parameters like mouthfeel. The background...
Development of laser beam injection system for the Edge Thomson Scattering (ETS) in ITER
Yatsuka, E.; Hatae, T.; Suitoh, S.; Ohara, M.; Hagita, K.; Inoue, K.; Bassan, M.; Walsh, M.; Itami, K.
2016-01-01
This paper focuses on the design and development of the laser injection system for the ITER Edge Thomson Scattering system (ETS). The ITER ETS achieves a temporal resolution of 100 Hz by firing two 50 Hz laser beams alternatively. The use of dual lasers enables us to perform the Thomson scattering measurements at a temporal resolution of 50 Hz in case that one of the laser systems stops functioning. A new type of beam combiner was developed to obtain a single beam that is collinear and fixed linearly polarized from two laser beams using a motor-driven rotating half-wave plate. The rotating half-wave plate method does not induce misalignment even if the rotating mechanism malfunctions. The combined beam is relayed from the diagnostic hall to the plasma using mirror optics and is absorbed at the beam dump integrated on the inner blanket. The beam alignment system was designed to direct the laser beam onto the center of the beam dump head. The beam position at the beam dump is monitored by four alignment laser beams which propagate parallel to the diagnostic Nd:YAG laser beam and imaging systems installed outside the diagnostic port.
Feasibility of Using Integrated Cavity Output Spectroscopy (ICOS) for Laser Scattering Research
Sotelo, Emily
2012-10-01
ICOS is proving to be a successful method for accurately measuring the atmospheric absorbance of a laser beam in a simulated environment. It was hypothesized that ICOS could be sensitive enough to accurately measure Rayleigh scattering. If feasible, it would mean that instead of having to conduct open range propagation experiments, scattering losses could be determined using a small, controlled test bed. This would be advantageous because it is cumbersome to propagate a laser beam a long distance in open space, as most other methods require. This study, done by Emily Sotelo as a student intern at the Air Force Research Laboratory, will be applied to the ongoing research of the scalability potential of the DPAL laser.
Laser-induced speckle scatter patterns in Bacillus colonies
Directory of Open Access Journals (Sweden)
Huisung eKim
2014-10-01
Full Text Available Label-free bacterial colony phenotyping technology called BARDOT (BActerial Rapid Detection using Optical scattering Technology provided successful classification of several different bacteria at the genus, species, and serovar level. Recent experiments with colonies of Bacillus species provided strikingly different characteristics of elastic light scatter (ELS patterns, which were comprised of random speckles compared to other bacteria, which are dominated by concentric rings and spokes. Since this laser-based optical sensor interrogates the whole volume of the colony, 3-D information of micro- and macro-structures are all encoded in the far-field scatter patterns. Here, we present a theoretical model explaining the underlying mechanism of the speckle formation by the colonies from Bacillus species. Except for Bacillus polymyxa, all Bacillus spp. produced random bright spots on the imaging plane, which presumably dependent on the cellular and molecular organization and content within the colony. Our scatter model-based analysis revealed that colony spread resulting in variable surface roughness can modify the wavefront of the scatter field. As the center diameter of the Bacillus spp. colony grew from 500 μm to 900 μm, average speckles area decreased 2-fold and the number of small speckles increased 7-fold. In conclusion, as Bacillus colony grows, the average speckle size in the scatter pattern decreases and the number of smaller speckle increases due to the swarming growth characteristics of bacteria within the colony.
Laser pulse-shape dependence of Compton scattering
Titov, Alexander I; Shibata, Takuya; Hosaka, Atsushi; Takabe, Hideaki
2014-01-01
Compton scattering of short and ultra short (sub-cycle) laser pulses off mildly relativistic electrons is considered within a QED framework. The temporal shape of the pulse is essential for the differential cross section as a function of the energy of the scattered photon at fixed observation angle. The partly integrated cross section is sensitive to the non-linear dynamics resulting in a large enhancement of the cross section for short and, in particular, for ultra-short flat-top pulse envelopes which can reach several orders of magnitude, as compared with the case of a long pulse. Such effects can be studied experimentally and must be taken into account in Monte-Carlo/transport simulations of %$e^+e^-$ pair production in the interaction of electrons and photons in a strong laser field.
Nonlinear scattering in hard tissue studied with ultrashort laser pulses
Energy Technology Data Exchange (ETDEWEB)
Eichler, J. [Technische Fachhochschule Berlin, Univ. of Applied Sciences (Germany); Kim, B.M. [Yonsei Univ., Wonjoo, Kangwon-Do (Korea)
2002-07-01
The back-scattered spectrum of ultrashort laser pulses (800 nm, 0.2 ps) was studied in human dental and other hard tissues in vitro below the ablation threshold. Frequency doubled radiation (SHG), frequency tripled radiation and two-photon fluorescence were detected. The relative yield for these processes was measured for various pulse energies. The dependence of the SHG signal on probe thickness was determined in forward and back scattering geometry. SHG is sensitive to linear polarization of the incident laser radiation. SHG in human teeth was studied in vitro showing larger signals in dentin than in cementum and enamel. In carious areas no SHG signal could be detected. Possible applications of higher harmonic radiation for diagnostics and microscopy are discussed. (orig.)
Nonline-of-sight laser gated viewing of scattered photons
Laurenzis, Martin; Velten, Andreas
2014-02-01
Laser gated viewing is a prominent sensing technology for optical imaging in harsh environments and can be applied for vision through fog, smoke, and other degraded environmental conditions as well as for the vision through sea water in submarine operation. A direct imaging of nonscattered photons (or ballistic photons) is limited in range and performance by the free optical path length, i.e., the length in which a photon can propagate without interaction with scattering particles or object surfaces. The imaging and analysis of scattered photons can overcome these classical limitations and it is possible to realize a nonline-of-sight imaging. The spatial and temporal distributions of scattered photons can be analyzed by means of computational optics and their information of the scenario can be restored. In particular, the information outside the line of sight or outside the visibility range is of high interest. We demonstrate nonline-of-sight imaging with a laser gated viewing system and different illumination concepts (point and surface scattering sources).
Diode Laser Velocity Measurements by Modulated Filtered Rayleigh Scattering
Mach, J. J.; Varghese, P. L.; Jagodzinski, J. J.
1999-01-01
The ability of solid-state lasers to be tuned in operating frequency at MHz rates by input current modulation, while maintaining a relatively narrow line-width, has made them useful for spectroscopic measurements. Their other advantages include low cost, reliability, durability, compact size, and modest power requirements, making them a good choice for a laser source in micro-gravity experiments in drop-towers and in flight. For their size, they are also very bright. In a filtered Rayleigh scattering (FRS) experiment, a diode laser can be used to scan across an atomic or molecular absorption line, generating large changes in transmission at the resonances for very small changes in frequency. The hyperfine structure components of atomic lines of alkali metal vapors are closely spaced and very strong, which makes such atomic filters excellent candidates for sensitive Doppler shift detection and therefore for high-resolution velocimetry. In the work we describe here we use a Rubidium vapor filter, and work with the strong D(sub 2) transitions at 780 nm that are conveniently accessed by near infrared diode lasers. The low power output of infrared laser diodes is their primary drawback relative to other laser systems commonly used for velocimetry. However, the capability to modulate the laser frequency rapidly and continuously helps mitigate this. Using modulation spectroscopy and a heterodyne detection scheme with a lock-in amplifier, one can extract sub-microvolt signals occurring at a specific frequency from a background that is orders of magnitude stronger. The diode laser modulation is simply achieved by adding a small current modulation to the laser bias current. It may also be swept repetitively in wavelength using an additional lower frequency current ramp.
Thomson scattering in high-intensity chirped laser pulses
Energy Technology Data Exchange (ETDEWEB)
Holkundkar, Amol R., E-mail: amol.holkundkar@pilani.bits-pilani.ac.in [Department of Physics, Birla Institute of Technology and Science, Pilani, Rajasthan 333031 (India); Harvey, Chris, E-mail: christopher.harvey@chalmers.se; Marklund, Mattias, E-mail: mattias.marklund@chalmers.se [Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden)
2015-10-15
We consider the Thomson scattering of an electron in an ultra-intense laser pulse. It is well known that at high laser intensities, the frequency and brilliance of the emitted radiation will be greatly reduced due to the electron losing energy before it reaches the peak field. In this work, we investigate the use of a small frequency chirp in the laser pulse in order to mitigate this effect of radiation reaction. It is found that the introduction of a negative chirp means the electron enters a high frequency region of the field while it still has a large proportion of its original energy. This results in a significant enhancement of the frequency and intensity of the emitted radiation as compared to the case without chirping.
Energy Technology Data Exchange (ETDEWEB)
Nikitin, Sergei Yu; Kormacheva, M A; Priezzhev, A V; Lugovtsov, Andrei E
2013-01-31
We have theoretically studied the effect of difference in particle shapes on the appearance of the diffraction pattern, which arises in the scattering of a laser beam on a dilute suspension of erythrocytes in an ectacytometer. We have proposed data processing algorithms allowing one to estimate the red blood cell shape parameter variance under conditions of laser ectacytometry. The conclusions of the theoretical analysis are verified experimentally. (laser methods in biology)
HT-7 Multipoint Nd Laser Thomson Scattering Apparatus
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A compact, low cost, multipoint Thomson scattering diagnostic system for HT-7 superconducting tokamak has been in operation since 1999. Its capability of measuring electron temperatures is in the range of 200 eV to 2 keV at a density of a few times 1012 cm-3, with a spatial resolution of 2.4 cm for 5 spatial points and a temporal resolution of 1 ms～1 s for 8 time points. The main components of the diagnostic system include a 20～25 J Nd:glass laser with 35 ns pulse width (8 pulses per burst), a KDP frequency-doubling unit, spherical mirrors of multipass input optical system, a wide-angle collection objective, a bandpass glass filter for reducing the stray light to zero, a f/2.5 polychromator, a fiberglass collimator, a photomultiplier's box with electronic preamplifier, high gain and high signal/noise ratio, CAMAC data acquisition and so on.The multipass optical system has been successful at increasing the quantity of scattered photons by passing the probing laser beam 10 times through the plasma under investigation. The HT7 Thomson scattering diagnostic has provided successfully the information on two-dimensional electron temperature in the plasma of HT-7 tokamak with LHCD and IBW.
LASER BIOLOGY AND MEDICINE: Light scattering study of rheumatoid arthritis
Beuthan, J.; Netz, U.; Minet, O.; Klose, Annerose D.; Hielscher, A. H.; Scheel, A.; Henniger, J.; Müller, G.
2002-11-01
The distribution of light scattered by finger joints is studied in the near-IR region. It is shown that variations in the optical parameters of the tissue (scattering coefficient μs, absorption coefficient μa, and anisotropy factor g) depend on the presence of the rheumatoid arthritis (RA). At the first stage, the distribution of scattered light was measured in diaphanoscopic experiments. The convolution of a Gaussian error function with the scattering phase function proved to be a good approximation of the data obtained. Then, a new method was developed for the reconstruction of distribution of optical parameters in the finger cross section. Model tests of the quality of this reconstruction method show good results.
Simulation of laser bistatic two-dimensional scattering imaging about lambertian cylinders
Gong, Yanjun; Li, Lang; Wang, Mingjun; Gong, Lei
2016-10-01
This paper deals with the simulation of laser bi-static scattering imaging about lambertian cylinders. Two-dimensional imaging of a target can reflect the shape of the target and material property on the surface of the target. Two-dimensional imaging has important significance for target recognition. Simulations results of laser bi-static two-dimensional scattering imaging of some cylinders are given. The laser bi-static scattering imaging of cylinder, whose surface material with diffuse lambertian reflectance, is given in this paper. The scattering direction of laser bi-static scattering imaging is arbitrary direction. The scattering direction of backward two-dimensional scattering imaging is at opposite direction of the incident direction of laser. The backward two-dimensional scattering imaging is special case of bi-static two dimensional scattering imaging. The scattering intensity of a micro-element on the target could be obtained based on the laser radar equation. The intensity is related to local angle of incidence, local angle of scattering and the infinitesimal area on the surface of cylinder. According to the incident direction of incident laser and normal of infinitesimal area, the local incidence angle can be calculated. According to the scattering direction and normal of infinitesimal area, the local angle of scattering can be calculated. Through surface integration and the introduction of the rectangular function, we can get the intensity of imaging unit on the imaging surface, and then get mathematical model of bi-static laser two dimensional scattering imaging about lambert cylinder. From the results given, one can see that the simulation results of laser bi-static scattering about lambert cylinder is correct.
Multiple Scattering Methods in Casimir Calculations
Milton, Kimball A
2007-01-01
Multiple scattering formulations have been recently rediscovered as a method of studying the quantum vacuum or Casimir interactions between distinct bodies. The methods are hardly new, but increased computing power and advances in understanding allow us to extract information efficiently. Here we review the method in the simple context of $\\delta$-function potentials, so-called semitransparent bodies. (In the limit of strong coupling, a semitransparent boundary becomes a Dirichlet one.) After applying the method to rederive the Casimir force between two semitransparent plates and the Casimir self-stress on a semitransparent sphere, we obtain expressions for the Casimir energies between disjoint parallel semitransparent cylinders and between disjoint semitransparent spheres. Simplifications occur for weak and strong coupling. In particular, after performing a power series expansion in the ratio of the radii of the objects to the separation between them, we are able to sum the weak-coupling expansions exactly t...
High order Nystrom method for acoustic scattering
Chen, Kun; Yang, Siming; Song, Jiming; Roberts, Ron
2015-03-01
While high frequency approximation methods are widely used to solve flaw scattering in ultrasonic nondestructive evaluation, full wave approaches based on integral equations have great potentials due to their high accuracy. In this work, boundary integral equations for acoustic wave scattering are solved using high order Nyström method. Compared with boundary elements method, it features the coincidence of the samples for interpolation basis and quadrature, which makes the far-field interaction free from numerical integration. The singular integral is dealt with using the Duffy transformation, while efficient singularity subtraction techniques are employed to evaluate the near singular integrals. This approach has the ease to go high order so highly accurate results can be obtained with fewer unknowns and faster convergence, and it is also amenable to incorporate fast algorithms like the multi-level fast multi-pole algorithm. The convergence of the approach for different orders of elements and interpolation basis functions is investigated. Numerical results are shown to validate this approach.
Broadband Brillouin scatter from CO/sub 2/-laser--target interactions
Energy Technology Data Exchange (ETDEWEB)
Mitchel, G.R.; Grek, B.; Johnston, T.W.; Pepin, H.; Church, P.; Lavigne, P.; Martin, F.; Decoste, R.
1982-05-24
Light scattered near the incident wavelength from CO/sub 2/ laser--solid target interactions in oblique incidence shows the spectral signature of Brillouin scattering both in the backward and in the near specular directions. This instability is apparently seeded by broadband scatter from the critical density surface and then amplified in the underdense plasma. 60% of the incident light is scattered, and the Brillouin contribution to total scatter may be large if the source is also large.
Mandel'shtam-Brillouin scattering of laser light as a remote sensing tool.
Daniels, A.
1972-01-01
The mathematical relations regarding the intensity of scattered light are derived. The nature of density inhomogeneities in air is discussed together with scattering due to moving isothermal pressure fluctuations, the spectral distribution of scattering from static isobaric density fluctuations, and applications of Mandel'shtam-Brillouin (M-B) scattering to atmospheric sensing. It is concluded that M-B scattering of laser light from the atmosphere has an outstanding potential for remote atmospheric sensing.
Register, D. F.; Trajmar, S.; Fineman, M. A.; Poe, R. T.; Csanak, G.; Jensen, S. W.
1983-01-01
Differential (in angle) electron scattering experiments on laser-excited Ba-138 1P were carried out at 30- and 100-eV impact energies. The laser light was linearly polarized and located in the scattering plane. The superelastic scattering signal was measured as a function of polarization direction of the laser light with respect to the scattering plane. It was found at low electron scattering angles that the superelastic scattering signal was asymmetric to reflection of the polarization vector with respect to the scattering plane. This is in contradiction with theoretical predictions. An attempt was made to pinpoint the reason for this observation, and a detailed investigation of the influence of experimental conditions on the superelastic scattering was undertaken. No explanation for the asymmetry has as yet been found.
Organic random lasers in the weak-scattering regime
Polson, R C; 10.1103/PhysRevB.71.045205
2005-01-01
We used the ensemble-averaged power Fourier transform (PFT) of random laser emission spectra over the illuminated area to study random lasers with coherent feedback in four different disordered organic gain media in the weak scattering regime, where the light mean free path, l* is much larger than the emission wavelength. The disordered gain media include a pi -conjugated polymer film, an opal photonic crystal infiltrated with a laser dye (rhodamine 6G; R6G) having optical gain in the visible spectral range, a suspension of titania balls in R6G solution, and biological tissues such as chicken breast infiltrated with R6G. We show the existence of universality among the random resonators in each gain medium that we tested, in which at the same excitation intensity a dominant random cavity is excited in different parts of the sample. We show a second universality when scaling the average PFT of the four different media by l*; we found that the dominant cavity in each disordered gain medium scales with l *. The e...
Determination of liquid-liquid critical point composition using 90∘ laser light scattering
Williamson, J. Charles; Brown, Allison M.; Helvie, Elise N.; Dean, Kevin M.
2016-04-01
Despite over a century of characterization efforts, liquid-liquid critical point compositions are difficult to identify with good accuracy. Reported values vary up to 10% for even well-studied systems. Here, a technique is presented for high-precision determination of the critical composition of a partially miscible binary liquid system. Ninety-degree laser light-scattering intensities from single-phase samples are analyzed using an equation derived from nonclassical power laws and the pseudospinodal approximation. Results are reported for four liquid-liquid systems (aniline + hexane, isobutyric acid + water, methanol + cyclohexane, and methanol + carbon disulfide). Compared to other methods, the 90∘ light-scattering approach has a strong dependence on composition near the critical point, is less affected by temperature fluctuations, and is insensitive to the presence of trace impurities in the samples. Critical compositions found with 90∘ light scattering are precise to the parts-per-thousand level and show long-term reproducibility.
Determination of liquid-liquid critical point composition using 90^{∘} laser light scattering.
Williamson, J Charles; Brown, Allison M; Helvie, Elise N; Dean, Kevin M
2016-04-01
Despite over a century of characterization efforts, liquid-liquid critical point compositions are difficult to identify with good accuracy. Reported values vary up to 10% for even well-studied systems. Here, a technique is presented for high-precision determination of the critical composition of a partially miscible binary liquid system. Ninety-degree laser light-scattering intensities from single-phase samples are analyzed using an equation derived from nonclassical power laws and the pseudospinodal approximation. Results are reported for four liquid-liquid systems (aniline + hexane, isobutyric acid + water, methanol + cyclohexane, and methanol + carbon disulfide). Compared to other methods, the 90^{∘} light-scattering approach has a strong dependence on composition near the critical point, is less affected by temperature fluctuations, and is insensitive to the presence of trace impurities in the samples. Critical compositions found with 90^{∘} light scattering are precise to the parts-per-thousand level and show long-term reproducibility.
Optical scattering methods applicable to drops and bubbles
Marston, Philip L.
1990-01-01
An overview of optical scattering properties of drops and bubbles is presented. The properties lead to unconventional methods for optically monitoring the size or shape of a scatterer and are applicable to acoustically levitated objects. Several of the methods are applicable to the detection and measurement of small amplitude oscillations. Relevant optical phenomena include: (1) rainbows; (2) diffraction catastrophes from spheroids; (3) critical angle scattering; (4) effects of coatings; (5) glory scattering; and (6) optical levitation.
Fernández-Oliveras, Alicia; Carrasco, Irene M.; Ghinea, Razvan; Pérez, María M.; Rubiño, Manuel
2012-06-01
Understanding the behaviour of light propagation in biological materials is essential for biomedical engineering and its applications. Among the key optical properties of biological media is the angular distribution of the scattered light, characterized by the average cosine of the scattering angle, called the scattering anisotropy coefficient (g). The value of g can be determined by experimentally irradiating the material with a laser beam and making angular-scattering measurements in a goniometer. In this work, an experimental technique was used to determine g by means of goniometric measurements of the laser light scattered off two different dental-resin composites (classified as nano and hybrid). To assess the accuracy of the experimental method, a Mie theory-based computational model was used. Independent measurements were used to determine some of the required input parameters for computation of the theoretical model. The g values estimated with the computational method (nano-filled: 0.9399; hybrid: 0.8975) and the values calculated with the experimental method presented (nano-filled: 0.98297 +/- 0.00021; hybrid: 0.95429 +/- 0.00014) agreed well for both dental resins, with slightly higher experimental values. The higher experimental values may indicate that the scattering particle causes more narrow-angle scattering than does a perfect sphere of equal volume, assuming that with more spherical scattering particles the scattering anisotropy coefficient increases. Since g represents the angular distribution of the scattered light, values provided by both the experimental and the computational methods show a strongly forward-directed scattering in the dental resins studied, more pronounced in the nano-filled composite than in the hybrid composite.
Narrowband inverse Compton scattering x-ray sources at high laser intensities
Seipt, D; Surzhykov, A; Fritzsche, S
2014-01-01
Narrowband x- and gamma-ray sources based on the inverse Compton scattering of laser pulses suffer from a limitation of the allowed laser intensity due to the onset of nonlinear effects that increase their bandwidth. It has been suggested that laser pulses with a suitable frequency modulation could compensate this ponderomotive broadening and reduce the bandwidth of the spectral lines, which would allow to operate narrowband Compton sources in the high-intensity regime. In this paper we, therefore, present the theory of nonlinear Compton scattering in a frequency modulated intense laser pulse. We systematically derive the optimal frequency modulation of the laser pulse from the scattering matrix element of nonlinear Compton scattering, taking into account the electron spin and recoil. We show that, for some particular scattering angle, an optimized frequency modulation completely cancels the ponderomotive broadening for all harmonics of the backscattered light. We also explore how sensitive this compensation ...
Etxebarria, J; Ortega, J; Folcia, C L; Sanz-Enguita, G; Aramburu, I
2015-04-01
We have studied the degradation process of the laser emission in a cholesteric liquid crystal laser. We have found that there exists a negative correlation between the laser efficiency and the amount of light scattered by the liquid-crystal sample in the illuminated area. The growth of scattering is attributed to the appearance of small imperfections generated in the sample as a result of certain thermal processes that involve the dye molecules. The scattering implies an increase of the coefficient of distributed losses, which is the main response of the rise of the laser threshold.
Analysis of random laser scattering pulse signals with lognormal distribution
Institute of Scientific and Technical Information of China (English)
Yan Zhen-Gang; Bian Bao-Min; Wang Shou-Yu; Lin Ying-Lu; Wang Chun-Yong; Li Zhen-Hua
2013-01-01
The statistical distribution of natural phenomena is of great significance in studying the laws of nature.In order to study the statistical characteristics of a random pulse signal,a random process model is proposed theoretically for better studying of the random law of measured results.Moreover,a simple random pulse signal generation and testing system is designed for studying the counting distributions of three typical objects including particles suspended in the air,standard particles,and background noise.Both normal and lognormal distribution fittings are used for analyzing the experimental results and testified by chi-square distribution fit test and correlation coefficient for comparison.In addition,the statistical laws of three typical objects and the relations between them are discussed in detail.The relation is also the non-integral dimension fractal relation of statistical distributions of different random laser scattering pulse signal groups.
Scattering effect in radiative heat transfer during selective laser sintering of polymers
Liu, Xin; Boutaous, M'hamed; Xin, Shihe
2016-10-01
The aim of this work is to develop an accurate model to simulate the selective laser sintering (SLS) process, in order to understand the multiple phenomena occurring in the material and to study the influence of each parameter on the quality of the sintered parts. A numerical model, coupling radiative and conductive heat transfers in a polymer powder bed providing a local temperature field, is proposed. To simulate the polymer sintering by laser heating as in additive manufacturing, a double-lines scanning of a laser beam over a thin layer of polymer powder is studied. An effective volumetric heat source, using a modified Monte Carlo method, is estimated from laser radiation scattering and absorption in a semi-transparent polymer powder bed. In order to quantify the laser-polymer interaction, the heating and cooling of the material is modeled and simulated with different types heat sources by both finite elements method (FEM) and discrete elements method (DEM). To highlight the importance of introducing a semi-transparent behavior of such materials and in order to validate our model, the results are compared with works taken from the literature.
Scattering Amplitudes via Algebraic Geometry Methods
DEFF Research Database (Denmark)
Søgaard, Mads
This thesis describes recent progress in the understanding of the mathematical structure of scattering amplitudes in quantum field theory. The primary purpose is to develop an enhanced analytic framework for computing multiloop scattering amplitudes in generic gauge theories including QCD without...... Feynman diagrams. The study of multiloop scattering amplitudes is crucial for the new era of precision phenomenology at the Large Hadron Collider (LHC) at CERN. Loop-level scattering amplitudes can be reduced to a basis of linearly independent integrals whose coefficients are extracted from generalized...
Experiment of X-ray Generations Using Laser-Compton Scattering at LINAC of SINAP
Institute of Scientific and Technical Information of China (English)
PAN Qiang-yan; XU Wang; LUO Wen; FAN Gong-tao; Yang Li-feng; Fan Guang-wei; LI Yong-jiang; XU Ben-ji; SHI Xiang-chun; LIN Guo-qiang; YAN Zhe; XU Yi; CHEN Jing-gen; GUO Wei; WANG Hong-wei; WANG Cheng-bin; XU Jia-qiang; Ma Yu-gang; CAI Xiang-zhou; ZHAO Ming-hua; SHEN Wen-qing
2009-01-01
Laser Compton scattering(LCS) can generate X-rays or y-rays with high brightness and easy controlled polarization by applying high-peak-power laser pulses to relativistic electron bunches.One of the most promising approaches to short pulsed X-ray sources is the laser synchrotron source.It is based on LCS between picoseconds relativistic electron bunches and picoseconds laser pulses.A project of Shanghai laser electron gamma source with LCS method has been proposed on Shanghai synchrotron radiation facility.Before that,a prototype has been developed in the beamline of the linear accelerator at the Shanghai Institute of Applied Physics,Chinese Academy of Sciences.The LCS experiment was carried out by using the 107 MeV,5 Hz,1 ns,0.1 nC electron bunches from the linear accelerator and the 18 ns,10 MW peak power,Nd:YAG laser pulses.In this communication,we describe the details and report the first results of this experiment.
Shiraya, Tomoyasu; Kato, Satoshi; Minami, Keiichiro; Miyata, Kazunori
2017-02-01
The aim of this study was to experimentally examine the changes in the transmittances of photocoagulation lasers when surface light scattering increases in AcrySof intraocular lenses (IOLs). SA60AT IOLs (Alcon) were acceleratingly aging for 0, 3, 5, and 10 years to simulate surface light scattering, and the surface light-scattering intensities of both IOL surfaces were measured using a Scheimpflug photographer. The powers of laser beams that passed from a laser photocoagulator through the aged IOLs were measured at 532, 577, and 647 nm. Changes in the laser power and transmittance with the years of aging and the intensities of surface light scattering were examined. Although the intensity of surface light scattering increased with the years of aging, the laser power did not change with the years of aging (P > 0.30, Kruskal-Wallis test). There were no significant changes in the laser transmittance with the years of aging or the laser wavelength (P > 0.30 and 0.57, respectively). The intensity of surface light scattering revealed no significant association with the laser transmittance at any wavelength (P > 0.37, liner regression). The increases in the surface light scattering of the AcrySof IOLs would not influence retinal photocoagulation treatments for up to 10 years after implantation.
Focussing effects in laser-electron Thomson scattering
Harvey, C; Holkundkar, A R
2016-01-01
We study the effects of laser pulse focussing on the spectral properties of Thomson scattered radiation. Modelling the laser as a paraxial beam we find that, in all but the most extreme cases of focussing, the temporal envelope has a much bigger effect on the spectrum than the focussing itself. For the case of ultra-short pulses where the paraxial model is no longer valid, we adopt a sub-cycle vector beam description of the field. It is found that the emission harmonics are blue shifted and broaden out in frequency space as the pulse becomes shorter. Additionally the carrier envelope phase becomes important, resulting in an angular asymmetry in the spectrum. We then use the same model to study the effects of focussing beyond the limit where the paraxial expansion is valid. It is found that fields focussed to sub-wavelength spot sizes produce spectra that are qualitatively similar to those from sub-cycle pulses due to the shortening of the pulse with focussing. Finally, we study high-intensity fields and find ...
Beam Diagnostics for Laser Undulator Based on Compton Backward Scattering
Kuroda, R
2005-01-01
A compact soft X-ray source is required in various research fields such as material and biological science. The laser undulator based on Compton backward scattering has been developed as a compact soft X-ray source for the biological observation at Waseda University. It is performed in a water window region (250eV - 500 eV) using the interaction between 1047 nm Nd:YLF laser (10ps FWHM) and about 5 MeV high quality electron beam (10ps FWHM) generated from rf gun system. The range of X-ray energy in the water window region has K-shell absorption edges of Oxygen, Carbon and Nitrogen, which mainly constitute of living body. Since the absorption coefficient of water is much smaller than the protein's coefficient in this range, a dehydration of the specimens is not necessary. To generate the soft X-ray pulse stably, the electron beam diagnostics have been developed such as the emittance measurement using double slit scan technique, the bunch length measurement using two frequency analysis technique. In this confere...
Ionization Induced Scattering of Femtosecond Intense Laser Pulses in Cluster Plasmas
Institute of Scientific and Technical Information of China (English)
Wang Xiangxin; Wang Cheng; Liu Jiansheng; Li Shaohui; Ni Guoquan
2005-01-01
The 45° scattering of a femtosecond (60 fs) intense laser pulse with a 20 nm FWHM (the full width at half maximum) spectrum centered at 790 nm has been studied experimentally while focused in argon clusters at intensity ～ 1016 W/cra2. Scattering spectra under different backing pressures and laser-plasma interaction lengths were obtained, which showed spectral blueshifting, beam refraction and complex modulation. These ionization-induced effects reveal the modulation of laser pulses propagating in plasmas and the existing obstacle in laser cluster interaction at high laser intensity and high electron density.
LIGHT SOURCE: TW Laser system for Thomson scattering X-ray light source at Tsinghua University
Yan, Li-Xm; Du, Ying-Chao; Du, Qiang; Li, Ren-Kai; Hua, Jian-Fei; Huang, Wen-Hui; Tang, Chuan-Xiang
2009-06-01
A TW (Tera Watt) laser system based on Ti:sapphire mainly for the Tsinghua Thomson scattering X-ray light source (TTX) is being built. Both UV (ultraviolet) laser pulse for driving the photocathode radio-frequency (RF) gun and the IR (infrared) laser pulse as the electron-beam-scattered-light are provided by the system. Efforts have also been made in laser pulse shaping and laser beam transport to optimize the high-brightness electron beam production by the photocathode RF gun.
TW Laser system for Thomson scattering X-ray light source at Tsinghua University
Institute of Scientific and Technical Information of China (English)
YAN Li-Xin; DU Ying-Chao; DU Qiang; LI Ren-Kai; HUA Jian-Fei; HUANG Wen-Hui; TANG Chuan-Xiang
2009-01-01
A TW(Tera Watt)laser system based on Ti:sapphire mainly for the Tsinghua Thomson scattering X-ray light source(TTX)is being built.Both UV(ultraviolet)laser pulse for driving the photocathode radiofrequency(RF)gun and the IR(infrared)laser pulse as the electron-beam-scattered-light are provided by the system.Efforts have also been made in laser pulse shaping and laser beam transport to optimize the high-brightness electron beam production by the photocathode RF gun.
Modifying molecular scattering from rough solid surfaces using ultrashort laser pulses
Khodorkovsky, Yuri; Averbukh, Ilya Sh
2012-01-01
We consider solid surface scattering of molecules that were subject to strong non-resonant ultrashort laser pulses just before hitting the surface. The pulses modify the rotational states of the molecules, causing their field free alignment, or a rotation with a preferred sense. We show that field-free laser-induced molecular alignment leads to correlations between the scattering angle and the sense of rotation of the scattered molecules. Moreover, by controlling the sense of laser induced unidirectional molecular rotation, one may affect the scattering angle of the molecules. This provides a new means for separation of mixtures of molecules (such as isotopes and nuclear-spin isomers) by laser controlled surface scattering.
Coherent methods in X-ray scattering
Energy Technology Data Exchange (ETDEWEB)
Gorobtsov, Oleg
2017-05-15
X-ray radiation has been used to study structural properties of materials for more than a hundred years. Construction of extremely coherent and bright X-ray radiation sources such as free electron lasers (FELs) and latest generationstorage rings led to rapid development of experimental methods relying on high radiation coherence. These methods allow to perform revolutionary studies in a wide range of fields from solid state physics to biology. In this thesis I focus on several important problems connected with the coherent methods. The first part considers applications of dynamical diffraction theory on crystals to studies with coherent X-ray radiation. It presents the design of a high-resolution spectrometer for free electron lasers that should allow to resolve spectral structure of individual FEL pulses. The spectrometer is based on the principle of dynamical diffraction focusing. The knowledge of individual FEL pulse spectra is necessary for understanding FEL longitudinal coherence. In the same part I present quasi-kinematical approximation to dynamical theory which allows to treat analytically phase effects observed in X-ray coherent imaging on nanocrystals. These effects may play a big role when methods such as ptychography are used to study crystalline samples. The second part deals with measurements of FEL coherence properties using intensity - intensity interferometry. Results of several experiments performed at FELs FLASH and LCLS are revealed in this section. I have developed models and theories to explain the behavior observed in experiments on FLASH. These models allowed to extract information about external positional jitter of FEL pulses and secondary beams present in FEL radiation. In the LCLS experiment the Hanbury Brown and Twiss type interferometry was performed on Bragg peaks from colloidal crystal. This did not require additional measurements without the sample and information was extracted directly from diffraction patterns. Therefore intensity
Laser bistatic two-dimensional scattering imaging simulation of lambert cone
Gong, Yanjun; Zhu, Chongyue; Wang, Mingjun; Gong, Lei
2015-11-01
This paper deals with the laser bistatic two-dimensional scattering imaging simulation of lambert cone. Two-dimensional imaging is called as planar imaging. It can reflect the shape of the target and material properties. Two-dimensional imaging has important significance for target recognition. The expression of bistatic laser scattering intensity of lambert cone is obtained based on laser radar eauqtion. The scattering intensity of a micro-element on the target could be obtained. The intensity is related to local angle of incidence, local angle of scattering and the infinitesimal area on the cone. According to the incident direction of laser, scattering direction and normal of infinitesimal area, the local incidence angle and scattering angle can be calculated. Through surface integration and the introduction of the rectangular function, we can get the intensity of imaging unit on the imaging surface, and then get Lambert cone bistatic laser two-dimensional scattering imaging simulation model. We analyze the effect of distinguishability, incident direction, observed direction and target size on the imaging. From the results, we can see that the scattering imaging simulation results of the lambert cone bistatic laser is correct.
Combined laser ultrasonics, laser heating, and Raman scattering in diamond anvil cell system
Zinin, Pavel V.; Prakapenka, Vitali B.; Burgess, Katherine; Odake, Shoko; Chigarev, Nikolay; Sharma, Shiv K.
2016-12-01
We developed a multi-functional in situ measurement system under high pressure equipped with a laser ultrasonics (LU) system, Raman device, and laser heating system (LU-LH) in a diamond anvil cell (DAC). The system consists of four components: (1) a LU-DAC system (probe and pump lasers, photodetector, and oscilloscope) and DAC; (2) a fiber laser, which is designed to allow precise control of the total power in the range from 2 to 100 W by changing the diode current, for heating samples; (3) a spectrometer for measuring the temperature of the sample (using black body radiation), fluorescence spectrum (spectrum of the ruby for pressure measurement), and Raman scattering measurements inside a DAC under high pressure and high temperature (HPHT) conditions; and (4) an optical system to focus laser beams on the sample and image it in the DAC. The system is unique and allows us to do the following: (a) measure the shear and longitudinal velocities of non-transparent materials under HPHT; (b) measure temperature in a DAC under HPHT conditions using Planck's law; (c) measure pressure in a DAC using a Raman signal; and (d) measure acoustical properties of small flat specimens removed from the DAC after HPHT treatment. In this report, we demonstrate that the LU-LH-DAC system allows measurements of velocities of the skimming waves in iron at 2580 K and 22 GPa.
Combined laser ultrasonics, laser heating, and Raman scattering in diamond anvil cell system.
Zinin, Pavel V; Prakapenka, Vitali B; Burgess, Katherine; Odake, Shoko; Chigarev, Nikolay; Sharma, Shiv K
2016-12-01
We developed a multi-functional in situ measurement system under high pressure equipped with a laser ultrasonics (LU) system, Raman device, and laser heating system (LU-LH) in a diamond anvil cell (DAC). The system consists of four components: (1) a LU-DAC system (probe and pump lasers, photodetector, and oscilloscope) and DAC; (2) a fiber laser, which is designed to allow precise control of the total power in the range from 2 to 100 W by changing the diode current, for heating samples; (3) a spectrometer for measuring the temperature of the sample (using black body radiation), fluorescence spectrum (spectrum of the ruby for pressure measurement), and Raman scattering measurements inside a DAC under high pressure and high temperature (HPHT) conditions; and (4) an optical system to focus laser beams on the sample and image it in the DAC. The system is unique and allows us to do the following: (a) measure the shear and longitudinal velocities of non-transparent materials under HPHT; (b) measure temperature in a DAC under HPHT conditions using Planck's law; (c) measure pressure in a DAC using a Raman signal; and (d) measure acoustical properties of small flat specimens removed from the DAC after HPHT treatment. In this report, we demonstrate that the LU-LH-DAC system allows measurements of velocities of the skimming waves in iron at 2580 K and 22 GPa.
Yashkir, Yuri
2006-04-01
We present a new computer numerical model of the phase-conjugate laser, utilizing an intra-cavity Stimulated Brillouin Scattering (SBS) element. The modelled laser system includes the active laser crystal which is placed between the output coupler mirror and a stimulated Brillouin scattering cell. The numerical model includes a set of rate equations for the active crystal inverse population, and for the photon density inside the laser cavity. The SBS backscattering model is based on a reduced set of coupled equations for electromagnetic fields for two waves (a pump wave and an SBS wave) propagating in opposite directions. The numerical integration of the set of equations simulates in detail the temporal dynamics of the laser. A wide range of realistic system parameters was numerically investigated. Different laser regimes (from a quasi -CW mode to a Q-switched mode) were numerically tested. The method of numerical modelling of such laser system can be efficiently used for an optimal laser design.
Energy Technology Data Exchange (ETDEWEB)
Mendys, A., E-mail: agata.mendys@uj.edu.pl [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagielloński, ul. Reymonta 4, 30-059 Kraków (Poland); Kański, M. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagielloński, ul. Reymonta 4, 30-059 Kraków (Poland); Farah-Sougueh, A. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagielloński, ul. Reymonta 4, 30-059 Kraków (Poland); GREMI — site de Bourges, Université d' Orléans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France); Pellerin, S. [GREMI — site de Bourges, Université d' Orléans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France); Pokrzywka, B. [Obserwatorium Astronomiczne na Suhorze, Uniwersytet Pedagogiczny, ul. Podchorażych 2, 30-084 Kraków (Poland); Dzierżęga, K. [Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagielloński, ul. Reymonta 4, 30-059 Kraków (Poland)
2014-06-01
A laser Thomson scattering method was applied to investigate the local Saha–Boltzmann equilibrium in aluminum laser-induced plasma. Plasma was created in ambient air using 4.5 ns pulses from a Nd:YAG laser at 532 nm, focused on an Al target. Spatially resolved measurements, performed for the time interval between 600 ns and 3 μs, show electron density and temperature to decrease from 3.4 × 10{sup 23} m{sup −3} to 0.5 × 10{sup 23} m{sup −3} and from 61,000 K to 13,000 K in the plasma core. The existence of local thermodynamic equilibria in the plasma was verified by comparing the rates of the collisional to radiative processes (the McWhirter criterion), as well as relaxation times and diffusion lengths of different plasma species, with the appropriate rate of electron density evolution and its gradients at given, experimentally determined, electron temperatures. We found these criteria to be much easier to satisfy for metallic plasma species than for nitrogen. The criteria are also easier to satisfy in the plasma core of higher electron density. - Highlights: • Laser Thomson scattering method was applied to investigate aluminum laser-induced plasma. • Spatio-temporal evolution of electron temperature and density was determined. • Three criteria for existence of local thermodynamic equilibrium were verified. • Criteria are much easier to satisfy for metallic plasma species than for nitrogen. • Criteria are easier to satisfy at earlier times and in the plasma core.
Multi-Parameter Scattering Sensor and Methods
Greenberg, Paul S. (Inventor); Fischer, David G. (Inventor)
2016-01-01
Methods, detectors and systems detect particles and/or measure particle properties. According to one embodiment, a detector for detecting particles comprises: a sensor for receiving radiation scattered by an ensemble of particles; and a processor for determining a physical parameter for the detector, or an optimal detection angle or a bound for an optimal detection angle, for measuring at least one moment or integrated moment of the ensemble of particles, the physical parameter, or detection angle, or detection angle bound being determined based on one or more of properties (a) and/or (b) and/or (c) and/or (d) or ranges for one or more of properties (a) and/or (b) and/or (c) and/or (d), wherein (a)-(d) are the following: (a) is a wavelength of light incident on the particles, (b) is a count median diameter or other characteristic size parameter of the particle size distribution, (c) is a standard deviation or other characteristic width parameter of the particle size distribution, and (d) is a refractive index of particles.
Modal Ring Method for the Scattering of Electromagnetic Waves
Baumeister, Kenneth J.; Kreider, Kevin L.
1993-01-01
The modal ring method for electromagnetic scattering from perfectly electric conducting (PEC) symmetrical bodies is presented. The scattering body is represented by a line of finite elements (triangular) on its outer surface. The infinite computational region surrounding the body is represented analytically by an eigenfunction expansion. The modal ring method effectively reduces the two dimensional scattering problem to a one-dimensional problem similar to the method of moments. The modal element method is capable of handling very high frequency scattering because it has a highly banded solution matrix.
Scattering Amplitudes via Algebraic Geometry Methods
Søgaard, Mads; Damgaard, Poul Henrik
This thesis describes recent progress in the understanding of the mathematical structure of scattering amplitudes in quantum field theory. The primary purpose is to develop an enhanced analytic framework for computing multiloop scattering amplitudes in generic gauge theories including QCD without Feynman diagrams. The study of multiloop scattering amplitudes is crucial for the new era of precision phenomenology at the Large Hadron Collider (LHC) at CERN. Loop-level scattering amplitudes can be reduced to a basis of linearly independent integrals whose coefficients are extracted from generalized unitarity cuts. We take advantage of principles from algebraic geometry in order to extend the notion of maximal cuts to a large class of two- and three-loop integrals. This allows us to derive unique and surprisingly compact formulae for the coefficients of the basis integrals. Our results are expressed in terms of certain linear combinations of multivariate residues and elliptic integrals computed from products of ...
Zhidkov, A; Bulanov, S S; Hosokai, T; Koga, J; Kodama, R
2013-01-01
Non-linear cascade scattering of intense, tightly focused laser pulses by relativistic electrons is studied numerically in the classical approximation including the radiation damping for the quantum parameter hwx-ray/E<1 and an arbitrary radiation parameter Kai. The electron energy loss, along with its side scattering by the ponderomotive force, makes the scattering in the vicinity of high laser field nearly impossible at high electron energies. The use of a second, co-propagating laser pulse as a booster is shown to solve this problem.
Electron Scattering from Freely Moveable spin-$\\frac{1}{2}$ fermion in Strong Laser Field
Liu, Ai-Hua
2014-01-01
We study the electron scatter from the freely movable spin-$\\frac{1}{2}$ particle in the presence of a linearly polarized laser field in the first Born approximation. The dressed state of electrons is described by a time-dependent wave function derived from a perturbation treatment (of the laser field). With the aid of numerical results we explore the dependencies of the differential cross section on the laser field properties such as the strength, the frequency, as well as on the electron-impact energy, etc. Due to the targets are movable, the DCS of this process reduced comparing to the Mott scattering, especially in small scattering angles.
Energy Technology Data Exchange (ETDEWEB)
Feit, M D; Kozlowski, M R; Rubenchik, A M; Sheehan, L; Wu, Z L
1999-12-22
Laser modulated scattering (LMS) is introduced as a non-destructive evaluation tool for defect inspection and characterization of optical surfaces and thin film coatings. This technique is a scatter sensitive version of the well-known photothermal microscopy (PTM) technique. It allows simultaneous measurement of the DC and AC scattering signals of a probe laser beam from an optical surface. By comparison between the DC and AC scattering signals, one can differentiate absorptive defects from non-absorptive ones. This paper describes the principle of the LMS technique and the experimental setup, and illustrates examples on using LMS as a tool for nondestructive evaluation of high quality optics.
Stimulated Raman scattering of light absorbing media excited by ultrashort laser pulses
Marchevskiy, F. N.; Strizhevskiy, V. L.; Feshchenko, V. P.
1985-01-01
The fluctuation-dissipation theory of spontaneous and stimulated vibration Raman scattering is worked out taking into account the dissipation losses at frequencies of laser pump and scattering radiation. General expressions are found, which describe the absolute intensities and shape, energy and duration of scattered pulses in terms of the parameters of the medium and the the input laser pulses. The general regularities are analyzed in detail. Conditions are found for the realization of spontaneous or stimulated Raman scattering and its dependence on absorption, pulse duration and other parameters of the problem.
Optical Extinction Measurements of Laser Side-Scatter During Tropical Storm Colin
Lane, John E.; Kasparis, Takis; Metzger, Philip; Michaelides, Silas
2017-01-01
A side-scatter imaging (SSI) technique using a 447 nm, 500 mW laser and a Nikon D80 camera was tested at Kennedy Space Center, Florida during the passing of a rain band associated with Tropical Storm Colin. The June 6, 2016, 22:00 GMT rain event was intense but short-lived owing to the strong west-to-east advection of the rain band. An effort to validate the optical extinction measurement was conducted by setting up a line of three tipping rain gauges along an 80 m east-west path and below the laser beam. Differences between tipping bucket measurements were correlated to the extinction coefficient profile along the lasers path, as determined by the SSI measurement. In order to compare the tipping bucket to the optical extinction data, a Marshall-Palmer DSD model was assumed. Since this was a daytime event, the laser beam was difficult to detect in the camera images, pointing out an important limitation of SSI measurements: the practical limit of DSD density that can be effectively detected and analyzed under daylight conditions using this laser and camera, corresponds to a fairly moderate rainfall rate on the order of 20 mmh (night measurements achieve a much improved sensitivity). The SSI analysis model under test produced promising results, but in order to use the SSI method for routine meteorological studies, improvements to the math model will be required.
A fiber-laser-based stimulated Raman scattering spectral microscope
Nose, Keisuke; Ozeki, Yasuyuki; Kishi, Tatsuya; Sumimura, Kazuhiko; Kanematsu, Yasuo; Itoh, Kazuyoshi
2013-02-01
Stimulated Raman scattering (SRS) spectral microscopy is a powerful technique for label-free biological imaging because it allows us to distinguish chemical species with overlapping Raman bands. Here we present an SRS spectral microscope based only on fiber lasers (FL's), which offer the possibilities of downsizing and simplification of the system. A femtosecond figure-8 Er-FL at a repetition rate of 54.4 MHz is used to generate pump pulses. After amplified by an Er doped fiber amplifier, Er-FL pulses are spectrally compressed to 2-ps second harmonic pulses. For generating Stokes pulses, a femtosecond Yb-FL pulses at a repetition rate of 27.2 MHz is used. Then these lasers are synchronized by a phase locked loop, which consists of a two-photon absorption photodetector, a loop filter, a phase modulator in the Er- FL cavity, and a piezo electric transducer in the Yb-FL cavity. The intensity noise of pump pulses is reduced by the collinear balanced detection (CBD) technique based on delay-and-add fiber lines. Experimentally, we confirmed that the intensity noise level of probe pulses was close to the shot noise limit. The Stokes pulses are introduced to a wavelength tunable band pass filter (BPF), which consists of a galvanomirror scanner, a 4-f optical system, a reflection grating, and a collimator. This system is able to scan the wavenumber from 2850 cm-1 to 3100 cm-1 by tuning the BPF. We succeeded in the spectral imaging of a mixture of polystyrene beads and poly(methyl methacrylate) beads.
Pulse temporal compression by two-stage stimulated Brillouin scattering and laser-induced breakdown
Liu, Zhaohong; Wang, Yulei; Wang, Hongli; Bai, Zhenxu; Li, Sensen; Zhang, Hengkang; Wang, Yirui; He, Weiming; Lin, Dianyang; Lu, Zhiwei
2017-06-01
A laser pulse temporal compression technique combining stimulated Brillouin scattering (SBS) and laser-induced breakdown (LIB) is proposed in which the leading edge of the laser pulse is compressed using SBS, and the low intensity trailing edge of the laser pulse is truncated by LIB. The feasibility of the proposed scheme is demonstrated by experiments in which a pulse duration of 8 ns is compressed to 170 ps. Higher compression ratios and higher efficiency are expected under optimal experimental conditions.
Stimulated Brillouin Scattering Suppression in Fiber Amplifiers via Chirped Diode Lasers
2011-09-01
1.55-µm diode laser at 1014 Hz/s using a phase-locked loop and a fiber -optic Michelson interferometer (9). The chirp has now been extended to 5×1015...diode lasers. By incorporating a fiber interferometer , the technique has been extended to chirp a (single) laser diode at 1015 Hz/s in an extremely...Stimulated Brillouin Scattering Suppression in Fiber Amplifiers via Chirped Diode Lasers by Jeffrey O. White, George Rakuljic, and Carl E
An Improved Hybrid Method for Inverse Obstacle Scattering Problems
Institute of Scientific and Technical Information of China (English)
LIU JUAN; MA FU-MING
2011-01-01
An improved hybrid method is introduced in this paper as a numerical method to reconstruct the scatterer by far-field pattern for just one incident direction with unknown physical properties of the scatterer.The improved hybrid method inherits the idea of the hybrid method by Kress and Serranho which is a combination of Newton and decomposition method,and it improves the hybrid method by introducing a general boundary condition.The numerical experiments show the feasibility of this method.
A Laser Scanning Tracking Method
Xu, Gaoyue; Hu, Baoli; Wang, Jiangping
1988-04-01
In this paper, a new tracking approach, a laser scanning tracking method (LSTM) is proposed. The LSTM has been designed to track a cylindrical retroreflective target mounted on the object, which makes plane motion. The retroreflector pasted by scotchlite reflective sheeting (mad. in 3M ,0.) i s located by scanning a laser beam in holizontal. When the retroreflector is struck, its position that is azimuth is read by microcomputer and the aiming device is servocontrolled by microcomputer according to this azimuth immediately. This is a step-by-step tracking method. The time of servo-reponse is less than one millisecona in actual tests. The angular accuracy is less than 0.5 milliradian. The track angular velocity is greater than one radian/second.
Makhoute, A.; Agueny, H.; Dubois, A.; Ajana, I.; Taoutioui, A.
2016-04-01
We report a detailed analysis of electron-helium scattering in the presence of a laser field; focusing on the elastic process of helium atoms from the ground state 11 S. The process under investigation is dealt with a nonperturbative approach using the Volkov wave function to describe the incident and scattered electrons, while the laser-target interaction is treated by using the Floquet method. The interaction of the incident electron with the atomic target is treated within the first Born approximation. Our results are perfectly consistent with the experimental data of DeHarak et al and with the Kroll-Watson approximation results for both one and two photon emission. We have investigated the effect of nonresonant and near resonant laser field on the electron-helium elastic collision process. It was found that the differential cross section is sensitive to the intensity and the frequency of the laser field. In the case of a non resonant laser field, dressing effects are important at small scattering angles. For a near-resonant laser photon energy, those effects are strongly reduced in the forward direction.
Andreev, A A; Zhidkov, A G; Uesaka, M; Kinoshita, K; Platonov, K Yu
2002-09-01
The light scattered backward from a target illuminated by ultraintense laser pulses carries important information about the nonlinear laser-plasma interaction. We analyze the usefulness of this information by plasma corona analysis with the help of an analytical model we developed, and particle-in-cell simulation. The spectrum of scattered light is shown to be shifted, to be broadened, and to be modulated, in comparison with the initial laser spectrum, and the spectral shift is an indicator of laser pulse contrast ratio.
CO2 laser collective Thomson scattering diagnostics on the HT-7 tokamak
Institute of Scientific and Technical Information of China (English)
李亚东; 李建刚; 毛剑珊
2004-01-01
A CW CO2 laser collective Thomson scattering diagnostics was developed to measure plasma density fluctuations on the HT-7 tokamak. The design and construction of CO2 laser scattering apparatus is described. The laser source is a continuous-wave CO2 laser with a cavity length of 1.9 m and a power output of about 10 W at 10.6 μm. The k-resolution of the system is △k ≈ 3.2 cm-1. The preliminary data from the diagnostic is presented.
Directory of Open Access Journals (Sweden)
Samuel P. Hernandez-Rivera
2013-03-01
Full Text Available Gold and silver nanoparticles (NPs were prepared in water, acetonitrile and isopropanol by laser ablation methodologies. The average characteristic (longer size of the NPs obtained ranged from 3 to 70 nm. 4-Aminobenzebethiol (4-ABT was chosen as the surface enhanced Raman scattering (SERS probe molecule to determine the optimum irradiation time and the pH of aqueous synthesis of the laser ablation-based synthesis of metallic NPs. The synthesized NPs were used to evaluate their capacity as substrates for developing more analytical applications based on SERS measurements. A highly energetic material, TNT, was used as the target compound in the SERS experiments. The Raman spectra were measured with a Raman microspectrometer. The results demonstrate that gold and silver NP substrates fabricated by the methods developed show promising results for SERS-based studies and could lead to the development of micro sensors.
Experimental investigation on wake profile detection based on laser scattering by bubbles
Institute of Scientific and Technical Information of China (English)
Liping Su; Weijiang Zhao; Xiaoyong Hu; Deming Ren; Xizhan Liu
2007-01-01
@@ The optical system for detecting wake profiles based on laser backscattering by bubbles at 180° is reported, in which the monostatic optical geometry is adopted and the power density estimation is used to process bubble scattering signal.
Energy Technology Data Exchange (ETDEWEB)
Yao, Jie, E-mail: yjie2@uh.edu [Department of Mechanical Engineering, University of Houston, Houston, Texas 77204 (United States); Lesage, Anne-Cécile; Hussain, Fazle [Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409 (United States); Bodmann, Bernhard G. [Department of Mathematics, University of Houston, Houston, Texas 77204 (United States); Kouri, Donald J. [Department of Physics, University of Houston, Houston, Texas 77204 (United States)
2014-12-15
The reversion of the Born-Neumann series of the Lippmann-Schwinger equation is one of the standard ways to solve the inverse acoustic scattering problem. One limitation of the current inversion methods based on the reversion of the Born-Neumann series is that the velocity potential should have compact support. However, this assumption cannot be satisfied in certain cases, especially in seismic inversion. Based on the idea of distorted wave scattering, we explore an inverse scattering method for velocity potentials without compact support. The strategy is to decompose the actual medium as a known single interface reference medium, which has the same asymptotic form as the actual medium and a perturbative scattering potential with compact support. After introducing the method to calculate the Green’s function for the known reference potential, the inverse scattering series and Volterra inverse scattering series are derived for the perturbative potential. Analytical and numerical examples demonstrate the feasibility and effectiveness of this method. Besides, to ensure stability of the numerical computation, the Lanczos averaging method is employed as a filter to reduce the Gibbs oscillations for the truncated discrete inverse Fourier transform of each order. Our method provides a rigorous mathematical framework for inverse acoustic scattering with a non-compact support velocity potential.
Laser-induced synthesis of metal-carbon materials for implementing surface-enhanced Raman scattering
Kucherik, A.; Arakelian, S.; Vartanyan, T.; Kutrovskaya, S.; Osipov, A.; Povolotskaya, A.; Povolotskii, A.; Man'shina, A.
2016-08-01
Metal-carbon materials exhibiting surface-enhanced Raman scattering have been synthesized by laser irradiation of colloidal systems consisting of carbon and noble metal nanoparticles. The dependence of the Raman scattering intensity on the material composition and laser irradiation conditions has been investigated. The possibility of recording the Raman spectrum of organic dye rhodamine 6G, deposited in amount of 10-6 M on the substrate obtained from a colloidal solution is demonstrated.
Observation of Thomson Scattering off Entropy Waves in a Laser-Produced Plasma
Institute of Scientific and Technical Information of China (English)
ZHENG Jian; BAI Bo; LIU Wan-Dong; YU Chang-Xuan; JIANG Xiao-Hua; YUAN Xiao-Dong; LI Wen-Hong; ZHENG Zhi-Jian
2001-01-01
A new feature in the Thomson scattering spectrum is observed from a laser-produced aluminium plasma, which may be the Thomson scattering off entropy waves in the plasma. Such a feature is only observable when the energy of the heater beam is low enough.
Energy Technology Data Exchange (ETDEWEB)
Fluck, R; Wegner, P; Sheehan, L; Hackel, L A
2000-12-22
We built a bi-directional scatter diagnostics to measure and quantify losses due to scattering and absorption of harmonic conversion crystals (DKDP) for the National Ignition Facility (NIF). The main issues to be addressed are (1) amount of total energy reaching the target if the target hole was {+-}200 {micro}rad in size, (2) distribution of energy inside the target hole, (3) collateral damage of other optics by scattered light. The scatter diagnostics enables angle-resolved measurements at 351 nm, and is capable of both near specular transmission and large angle scatter measurements. In the near specular setup, the transmission can be measured within {+-}65 {micro}rad up to {+-}60 mrad acceptance angle. A silicon photo detector and a scientific-grade CCD camera provide total energy and energy distribution. A linear swing arm detection system enables large angle scatter measurements of 360{sup o}, in principal, with step sizes as small as 0.01{sup o} and different collection angle ranging between 1 and 20 mad. In this paper, scatter effects from laser damage and final finishing process of DKDP are discussed.
A direct sampling method for inverse electromagnetic medium scattering
Ito, Kazufumi
2013-09-01
In this paper, we study the inverse electromagnetic medium scattering problem of estimating the support and shape of medium scatterers from scattered electric/magnetic near-field data. We shall develop a novel direct sampling method based on an analysis of electromagnetic scattering and the behavior of the fundamental solution. It is applicable to a few incident fields and needs only to compute inner products of the measured scattered field with the fundamental solutions located at sampling points. Hence, it is strictly direct, computationally very efficient and highly robust to the presence of data noise. Two- and three-dimensional numerical experiments indicate that it can provide reliable support estimates for multiple scatterers in the case of both exact and highly noisy data. © 2013 IOP Publishing Ltd.
Buică, Gabriela
2017-01-01
We theoretically study the influence of laser polarization in inelastic scattering of electrons by hydrogen atoms in the presence of a circularly polarized laser field in the domain of field strengths below 107 V/cm and high projectile energies. A semi-perturbative approach is used in which the interaction of the projectile electrons with the laser field is described by Gordon-Volkov wave functions, while the interaction of the hydrogen atom with the laser field is described by first-order time-dependent perturbation theory. A closed analytical solution is derived in laser-assisted inelastic electron-hydrogen scattering for the 1 s → nl excitation cross section which is valid for both circular and linear polarizations. For the excitation of the n=2 levels simple analytical expressions of differential cross section are derived for laser-assisted inelastic scattering in the perturbative domain, and the differential cross sections by the circularly and linearly polarized laser fields and their ratios for one- and two-photon absorption are calculated as a function of the scattering angle. Detailed numerical results for the angular dependence and the resonance structure of the differential cross sections are discussed for the 1 s → 4 l excitations of hydrogen in a circularly polarized laser field.
Meyer, William V.; Tscharnuter, Walther W.; Macgregor, Andrew D.; Dautet, Henri; Deschamps, Pierre; Boucher, Francois; Zuh, Jixiang; Tin, Padetha; Rogers, Richard B.; Ansari, Rafat R.
1994-01-01
Recent advancements in laser light scattering hardware are described. These include intelligent single card correlators; active quench/active reset avalanche photodiodes; laser diodes; and fiber optics which were used by or developed for a NASA advanced technology development program. A space shuttle experiment which will employ aspects of these hardware developments is previewed.
Design of a Polarised Positron Source Based on Laser Compton Scattering
Araki, S; Honda, Y; Kurihara, Y; Kuriki, M; Okugi, T; Omori, T; Taniguchi, T; Terunuma, N; Urakawa, J; Artru, X; Chevallier, M; Strakhovenko, V M; Bulyak, E; Gladkikh, P; Mönig, K; Chehab, R; Variola, A; Zomer, F; Guiducci, S; Raimondi, Pantaleo; Zimmermann, Frank; Sakaue, K; Hirose, T; Washio, M; Sasao, N; Yokoyama, H; Fukuda, M; Hirano, K; Takano, M; Takahashi, T; Sato, H; Tsunemi, A; Gao, J; Soskov, V
2005-01-01
We describe a scheme for producing polarised positrons at the ILC from polarised X-rays created by Compton scattering of a few-GeV electron beam off a CO2 or YAG laser. This scheme is very energy effective using high finesse laser cavities in conjunction with an electron storage ring.
A time domain sampling method for inverse acoustic scattering problems
Guo, Yukun; Hömberg, Dietmar; Hu, Guanghui; Li, Jingzhi; Liu, Hongyu
2016-06-01
This work concerns the inverse scattering problems of imaging unknown/inaccessible scatterers by transient acoustic near-field measurements. Based on the analysis of the migration method, we propose efficient and effective sampling schemes for imaging small and extended scatterers from knowledge of time-dependent scattered data due to incident impulsive point sources. Though the inverse scattering problems are known to be nonlinear and ill-posed, the proposed imaging algorithms are totally "direct" involving only integral calculations on the measurement surface. Theoretical justifications are presented and numerical experiments are conducted to demonstrate the effectiveness and robustness of our methods. In particular, the proposed static imaging functionals enhance the performance of the total focusing method (TFM) and the dynamic imaging functionals show analogous behavior to the time reversal inversion but without solving time-dependent wave equations.
Demonstration of X-ray Thomson Scattering on Shenguang-Ⅱ Laser Facility
Institute of Scientific and Technical Information of China (English)
胡广月; 张小丁; 郑坚; 雷安乐; 沈百飞; 徐至展; 张继彦; 杨家敏; 杨国洪; 韦敏习; 李军; 丁永坤
2012-01-01
X-ray Thomson scattering technique for diagnosing dense plasma was demonstrated on Shenguang-Ⅱ laser facility. Laser plasma x-ray source of titanium He-a lines (-4.75 keV), generated by laser beam (1.5 kJ/527 nm/2 ns) heated titanium thin foil, was used as x-ray probe beam. The x-ray probe was then scattered by cold CH foam column of 1 g/cm^3 density. The scattered radiation at 90° was diffracted by polyethylene terephthalate (PET) crystal and recorded on x-ray charge-coupled device. Well-defined scattering spectra were obtained with good signal to noise ratio.
A two-stage method for inverse medium scattering
Ito, Kazufumi
2013-03-01
We present a novel numerical method to the time-harmonic inverse medium scattering problem of recovering the refractive index from noisy near-field scattered data. The approach consists of two stages, one pruning step of detecting the scatterer support, and one resolution enhancing step with nonsmooth mixed regularization. The first step is strictly direct and of sampling type, and it faithfully detects the scatterer support. The second step is an innovative application of nonsmooth mixed regularization, and it accurately resolves the scatterer size as well as intensities. The nonsmooth model can be efficiently solved by a semi-smooth Newton-type method. Numerical results for two- and three-dimensional examples indicate that the new approach is accurate, computationally efficient, and robust with respect to data noise. © 2012 Elsevier Inc.
A patient-specific scatter artifacts correction method
Zhao, Wei; Niu, Kai; Schafer, Sebastian; Royalty, Kevin; Chen, Guang-Hong
2015-01-01
This paper provides a fast and patient-specific scatter artifact correction method for cone-beam computed tomography (CBCT) used in image-guided interventional procedures. Due to increased irradiated volume of interest in CBCT imaging, scatter radiation has increased dramatically compared to 2D imaging, leading to a degradation of image quality. In this study, we propose a scatter artifact correction strategy using an analytical convolution-based model whose free parameters are estimated using a rough estimation of scatter profiles from the acquired cone-beam projections. It was evaluated using Monte Carlo simulations with both monochromatic and polychromatic X-ray sources. The results demonstrated that the proposed method significantly reduced the scatter-induced shading artifacts and recovered CT numbers.
Thomson Scattering Process in Laser-Produced Plasmas
Institute of Scientific and Technical Information of China (English)
YU Quan-Zhi; JIANG Xiao-Hua; LI Wen-Hong; LIU Shen-Ye; ZHENG Zhi-Jian; ZHANG Jie; LI Yu-Tong; ZHENG Jun; YAN Fei; LU Xin; WANG Zhe-Bin; ZHENG Jian; YU Chang-Xuan
2005-01-01
@@ We present the evolutions of the electron temperature and plasma expansion velocity with Thomson scattering experiment. The observed time-resolved ion-acoustic image is reproduced by a numerical code which couples the Thomson scattering theory with the output parameters of the one-dimensional hydrocode MEDUSA.
Method for measuring multiple scattering corrections between liquid scintillators
Verbeke, J. M.; Glenn, A. M.; Keefer, G. J.; Wurtz, R. E.
2016-07-01
A time-of-flight method is proposed to experimentally quantify the fractions of neutrons scattering between scintillators. An array of scintillators is characterized in terms of crosstalk with this method by measuring a californium source, for different neutron energy thresholds. The spectral information recorded by the scintillators can be used to estimate the fractions of neutrons multiple scattering. With the help of a correction to Feynman's point model theory to account for multiple scattering, these fractions can in turn improve the mass reconstruction of fissile materials under investigation.
A direct sampling method to an inverse medium scattering problem
Ito, Kazufumi
2012-01-10
In this work we present a novel sampling method for time harmonic inverse medium scattering problems. It provides a simple tool to directly estimate the shape of the unknown scatterers (inhomogeneous media), and it is applicable even when the measured data are only available for one or two incident directions. A mathematical derivation is provided for its validation. Two- and three-dimensional numerical simulations are presented, which show that the method is accurate even with a few sets of scattered field data, computationally efficient, and very robust with respect to noises in the data. © 2012 IOP Publishing Ltd.
Barnes, Michael; Dudbridge, Michael; Duckett, Tom
2012-01-01
This paper introduces novel non-contact methods for detecting faults in heat seals of food packages. Two alternative imaging technologies are investigated; laser scatter imaging and polarised light stress images. After segmenting the seal area from the rest of the respective image, a classifier is trained to detect faults in different regions of the seal area using features extracted from the pixels in the respective region. A very large set of candidate features, based on statistical informa...
R12 hydrate formation kinetics based on laser light scattering technique
Institute of Scientific and Technical Information of China (English)
孙长宇; 陈光进; 郭天民
2003-01-01
A circulating flow system consisting of a transparent U-bend flow loop, a mixing tank and a laser granulometer was set up for studying the kinetics hydrate formation and the pressure is up to 4 MPa. Refrigerant CCl2F2 (R12) hydrate formation experiments were performed using laser light scattering method at 277.1 K and pressures of 0.24 and 0.32 MPa. The liquid flow rates were in the range of 300-1400 L/h. The size distribution and density of R12 hydrate particles in pure water were measured using a laser granulometer. Experimental results show that the size of hydrate particles increases sharply at the initial stage and approaches gradually to a stable size. The hydrate particle concentration in the aqueous phase increases with pressure and circulating liquid flow rate. Based on the material balance, the mathematical model among gas consumption, average hydrate particle size and shading ratio has been established. The calculated results using the mathematical model accord well with the experimental gas consumption data.
Evolution of Elastic X-ray Scattering in Laser-Shocked Warm Dense Li
Energy Technology Data Exchange (ETDEWEB)
Kugland, N L; Gregori, G; Bandyopadhyay, S; Brenner, C; Brown, C; Constantin, C; Glenzer, S H; Khattak, F; Kritcher, A L; Niemann, C; Otten, A; Pasley, J; Pelka, A; Roth, M; Spindloe, C; Riley, D
2009-06-02
We have studied the dynamics of warm dense Li with near-elastic x-ray scattering. Li foils were heated and compressed using shock waves driven by 4 ns long laser pulses. Separate 1 ns long laser pulses were used to generate a bright source of 2.96 keV Cl Ly-{alpha} photons for x-ray scattering, and the spectrum of scattered photons was recorded at a scattering angle of 120{sup o} using a HOPG crystal operated in the von Hamos geometry. A variable delay between the heater and backlighter laser beams measured the scattering time evolution. Comparison with radiation hydrodynamics simulations shows that the plasma is highly coupled during the first several nanoseconds, then relaxes to a moderate coupling state at later times. Near-elastic scattering amplitudes have been successfully simulated using the screened one-component plasma model. Our main finding is that the near-elastic scattering amplitudes are quite sensitive to the mean ionization state {bar Z}, and by extension to the choice of ionization model in the radiation-hydrodynamics simulations used to predict plasma properties within the shocked Li.
Nonlinear Propagation of Coupling Optical Pulse under Compton Scattering in Laser Medium
Institute of Scientific and Technical Information of China (English)
HAO Dong-shan; ZHANG Xiao-fu
2006-01-01
After considering Kerr nonlinear effect,group velocity dispersion of host and gain distribution of active particle in laser amplifying medium,a basic equation describing propagation of the coupling optical pulse under the multi-photon nonlinear Compton scattering in the laser amplifying medium has been deduced. Besides,the profile and power spectrum of a picosecond-level super-Gaussian coupling pulse in the laser amplifying medium have been discussed when its central frequency coincides with the gain peak frequency of the laser amplifying medium.
Guseva, N. P.; Maximova, Irina S.; Romanov, Sergey V.; Shubochkin, L. P.; Tatarintsev, Sergey N.
1991-05-01
Recently a great deal of attention has been given to the investigation artificial lipid liposomes, due to their application as "containers" for directed transport of biologically active compounds into particular cells, organs and tissues for prophylaxis and therapy of infectious diseases. The use of traditional methods of liposome investigation, such as sedimentation, electrophoresis and chromatography is impeded by low liposome resistivity to different deformations. In conjunction with this, optical methods of laser light scattering are promising as they allow nondisturbing, precise and quick investigations. This paper describes the investigation of vesicle systems prepared from egg lecithin of Serva Corporation and their complexes with the capsular antigen of the plague microbe. The capsular antigen Fl was obtained from EV plague microbe grown at 37° C on Huttinger agar. Fl was isolated by gel-filtration on ASA-22 followed by freeze drying of the preparation. Angular dependences of polarized radiation scattering were measured for several liposome suspension samples in a saline solution before and after the interaction with the plague microbe capsular antigen. The aim of the investigation was to analyze the nature of mutual antigen arrangement in a liposome and to develop methods for measuring its inclusion percentage.
Laser-induced speckle scatter patterns in Bacillus colonies
Kim, Huisung; Singh, Atul K.; Arun K Bhunia; Bae, Euiwon
2014-01-01
Label-free bacterial colony phenotyping technology called BARDOT (Bacterial Rapid Detection using Optical scattering Technology) provided successful classification of several different bacteria at the genus, species, and serovar level. Recent experiments with colonies of Bacillus species provided strikingly different characteristics of elastic light scatter (ELS) patterns, which were comprised of random speckles compared to other bacteria, which are dominated by concentric rings and spokes. S...
Laser-induced speckle scatter patterns in Bacillus colonies
Huisung eKim; Singh, Atul K.; Arun K Bhunia; Euiwon eBae
2014-01-01
Label-free bacterial colony phenotyping technology called BARDOT (BActerial Rapid Detection using Optical scattering Technology) provided successful classification of several different bacteria at the genus, species, and serovar level. Recent experiments with colonies of Bacillus species provided strikingly different characteristics of elastic light scatter (ELS) patterns, which were comprised of random speckles compared to other bacteria, which are dominated by concentric rings and spokes. S...
Elastic scattering of positronium: Application of the confined variational method
Zhang, Junyi
2012-08-01
We demonstrate for the first time that the phase shift in elastic positronium-atom scattering can be precisely determined by the confined variational method, in spite of the fact that the Hamiltonian includes an unphysical confining potential acting on the center of mass of the positron and one of the atomic electrons. As an example, we study the S-wave elastic scattering for the positronium-hydrogen scattering system, where the existing 4% discrepancy between the Kohn variational calculation and the R-matrix calculation is resolved. © Copyright EPLA, 2012.
Laser diagnostics in combustion. Elastic scattering and picosecond laser-induced fluorescence
Energy Technology Data Exchange (ETDEWEB)
Ossler, Frederik
1999-05-01
Elastic scattering and the Lorenz-Mie (LM) theory in particular is used for the characterization of sub-micron- and micron-sized droplets of organic fuels in sprays and aerosols. Calculations on the Lorenz-Mie theory show that backward-sideward scattered visible radiation can be used for unambiguous detection of ensembles of homogeneous droplets of organic substances with diameters around 1 micrometer (size parameter between 2 and 6). A backward feature in the polarization ratio appears with a value considerably higher than one, on the opposite to the case of the rainbow observed for larger droplets. A comparison between measurements and LM calculations showed that a large amount of droplets in aerosols and well-atomized sprays were smaller than one micrometer in diameter. The LM theory was also used to characterize different size groups in a burning spray. A 3 - D technique based on a picosecond laser and a streak camera was demonstrated for measurements of fast and turbulent biphase flows. The entire 3 - D information was obtained within a time-span of less than 15 nanoseconds. A 2 - D technique for lifetime measurements based on a picosecond laser and a streak camera has been demonstrated on static objects. An analysis indicates that the technique may be applied to measurements of lifetimes around or below one picosecond employing femtosecond lasers and femtosecond streak-cameras. The technique may in principle be used to study dynamic systems when two detectors are used. Fluorescence lifetime measurements on hydrogen and oxygen atoms in flames at atmospheric pressure demonstrate the need of lasers with suiting spectral properties such as jitter and linewidth and the need of detectors with high sensitivity in the near IR in the case of oxygen atoms. The fluorescence lifetimes of gas phase acetone and 3-pentanone at 266 nm excitation wavelength have been measured for mixtures with nitrogen and air at temperatures between 323 and 723 K and pressures between 0
Laser diagnostics in combustion: Elastic scattering and picosecond laser-induced fluorescence
Ossler, Frederik E.
Elastic scattering and the Lorenz-Mie (LM) theory in particular is used for the characterization of submicron- and micron-sized droplets of organic fuels in sprays and aerosols. Calculations on the Lorenz-Mie theory show that backward-sideward scattered visible radiation can be used for unambiguous detection of ensembles of homogeneous droplets of organic substances with diameters around 1 micrometer (size parameter between 2 and 6). A backward feature in the polarization ratio appears with a value considerably higher than one, on the opposite to the case of the rainbow observed for larger droplets. A comparison between measurements and LM calculations showed that a large amount of droplets in aerosols and well-atomized sprays were smaller than one micrometer in diameter. The LM theory was also used to characterize different size groups in a burning spray. A 3-D technique based on a picosecond laser and a streak camera was demonstrated for measurements of fast and turbulent biphase flows. The entire 3-D information was obtained within a time-span of less than 15 nanoseconds. A 2-D technique for lifetime measurements based on a picosecond laser and a streak camera has been demonstrated on static objects. An analysis indicates that the technique may be applied to measurements of lifetimes around or below one picosecond employing femtosecond lasers and femtosecond streak-cameras. The technique may in principle be used to study dynamic systems when two detectors are used. Fluorescence lifetime measurements on hydrogen and oxygen atoms in flames at atmospheric pressure demonstrate the need of lasers with suiting spectral properties such as jitter and linewidth and the need of detectors with high sensitivity in the near IR in the case of oxygen atoms. The fluorescence lifetimes of gas phase acetone and 3- pentanone at 266 nm excitation wavelength have been measured for mixtures with nitrogen and air at temperatures between 323 and 723 K and pressures between 0.01 and 10
Finite-basis-set expansion methods for scattering problems
Energy Technology Data Exchange (ETDEWEB)
Ladanyi, K.; Levay, P.; Apagyi, B.
1988-10-01
A wide variety of finite-basis-set expansion methods is applied to electron--hydrogen-atom scattering in the static-exchange approximation. All these methods are based on the Lippmann-Schwinger formalism. A careful analysis of the numerical results is presented with the aim of selecting efficient approaches to the solution of realistic electron-atom (and electron-molecule) scattering problems. The results show that the efficiency of the expansion methods may depend sensitively on the characteristics of the interaction terms. Some difficulties of the simple method of moments are pointed out. A particular least-squares method is proposed to avoid the spurious singularities encountered in applications of the Schwinger variational method to singlet scattering processes.
Ma, Shufen; Liu, Haiguang
2016-04-01
X-ray free-electron lasers generate intense femtosecond X-ray pulses, so that high-resolution structure determination becomes feasible from noncrystalline samples, such as single particles or single molecules. At the moment, the orientation of sample particles cannot be precisely controlled, and consequently the unknown orientation needs to be recovered using computational algorithms. This delays the model reconstruction until all the scattering patterns have been re-oriented, which often entails a long elapse of time and until the completion of the experiment. The scattering patterns from single particles or multiple particles can be summed to form a virtual powder diffraction pattern, and the low-resolution region, corresponding to the small-angle X-ray scattering (SAXS) regime, can be analysed using existing SAXS methods. This work presents a pipeline that converts single-particle data sets into SAXS data, from which real-time model reconstruction is achieved using the model retrieval approach implemented in the software package SASTBX [Liu, Hexemer & Zwart (2012). J. Appl. Cryst.45, 587-593]. To illustrate the applications, two case studies are presented with real experimental data sets collected at the Linac Coherent Light Source.
Non-Linear Compton Scattering of Ultrashort and Ultraintense Laser Pulses
Seipt, D
2010-01-01
The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed, which is independent of the considered pulse shape and pulse length. A broad distribution of scatted photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thu...
Low-threshold GaN thin-film random laser through the weak scattering feedback
Zhu, Hai; Chen, Anqi; Wu, Yanyan; Ji, Xu; He, Yiting; Qiu, Zhiren; Tang, Zikang; Yu, Siufung
2017-02-01
Room temperature random lasing is demonstrated from a GaN epitaxy film with defect pits that result from growth imperfection. The optical coherence feedback is attributed to the formation of closed-loop paths of light through the scattering effect of the defect pits, which can avoid the difficulty of fabricating an artificial cavity. The random lasing action was also investigated through near and far-field patterns that imaged onto the CCD camera. In addition, the angle distribution of the laser beam was illustrated by use of an angle-resolved spectrometer. The lasing threshold, based on the weak scattering diffusive mode of GaN, is about one order of magnitude lower than that strong scattering random laser (RL). Hence, the results in this paper represent a low-cost technique to realize GaN-based laser diodes without the fabrication difficulty of cavity facets that result from the hardness of the sapphire substrate.
Modulated method for efficient, narrow-bandwidth, laser Compton X-ray and gamma-ray sources
Energy Technology Data Exchange (ETDEWEB)
Barty, Christopher P. J.
2017-07-11
A method of x-ray and gamma-ray generation via laser Compton scattering uses the interaction of a specially-formatted, highly modulated, long duration, laser pulse with a high-frequency train of high-brightness electron bunches to both create narrow bandwidth x-ray and gamma-ray sources and significantly increase the laser to Compton photon conversion efficiency.
Far-infrared laser scattering in the ACT-I toroidal device
Energy Technology Data Exchange (ETDEWEB)
Goree, J.; Mansfield, D.K.; Ono, M.; Wong, K.L.
1984-12-01
A far-infrared laser scattering diagnostic has been built for the ACT-I toroidal device. The optical system uses a passively stabilized 447-..mu..m CH/sub 3/I laser. A polyethylene etalon is the beam splitter. The vacuum windows are plastic (TPX), which we found has the vacuum property Q 6.5 x 10/sup -9/ torr-liter/sec/cm/sup 2/. Using paraboloidal and ellipsoidal mirrors for detection optics improves the signal strength and allows a better rf enclosure design for the detector. The diagnostic was tested by scattering from an ion Bernstein wave, a technique which can be used for ion temperature diagnostics.
Energy Technology Data Exchange (ETDEWEB)
Eversole, D. [University of Texas at Austin, Department of Biomedical Engineering, Austin, TX (United States); University of Texas at Austin, Center for Nanomaterials, Austin, TX (United States); Luk' yanchuk, B. [Data Storage Institute, Agency for Science, Technology and Research, Singapore (Singapore); Ben-Yakar, A. [University of Texas at Austin, Department of Biomedical Engineering, Austin, TX (United States); University of Texas at Austin, Center for Nanomaterials, Austin, TX (United States); University of Texas at Austin, Department of Mechanical Engineering, Austin, TX (United States)
2007-11-15
We present the fabrication of nanostructures ablated on silicon(100) by the plasmonic scattering of 780 nm, 220 fs laser pulses in the near-field of gold nanospheres. We take advantage of the enhanced plasmonic scattering of ultrashort laser light in the particle near-field to ablate well-defined nanocraters. Gold nanospheres of 150 nm diameter are deposited onto a silicon surface and irradiated with a single laser pulse. We studied the effect of laser polarization on the morphology of ablated nanostructures and estimated the minimum fluence for plasmonic nanoablation. When the polarization of the incident radiation is directed at a 45 angle into the substrate surface, a near-field enhancement of 23.1{+-}7.6 is measured, reducing the required silicon ablation fluence from 191{+-}14 mJ/cm{sup 2} to 8.2{+-}2.9 mJ/cm{sup 2}. Enhancements are also measured for laser polarizations parallel to the substrate surface when the substrate is angled 0 and 45 to the incident irradiation, giving enhancements of 6.9{+-}0.6 and 4.1{+-}1.3, respectively. Generated nanocrater morphologies show a direct imprint of the particle dipolar scattering region, as predicted in our theoretical calculations. The measured near-field enhancement values agree well with the maximum field enhancements obtained in our calculations. The agreement between theory and measurements supports that the nanocraters are indeed formed by the enhanced plasmonic scattering in the near-field of the nanoparticles. (orig.)
Development of fiber lasers and devices for coherent Raman scattering microscopy
Lamb, Erin Stranford
As ultrafast laser technology has found expanding application in machining, spectroscopy, microscopy, surgery, and numerous other areas, the desire for inexpensive and robust laser sources has grown. Until recently, nonlinear effects in fiber systems due to the tight confinement of the light in the core have limited their performance. However, with advances in managing nonlinearity through pulse propagation physics and the use of large core fibers, the performance of fiber lasers can compete with that of their solid-state counterparts. As specific applications, such as coherent Raman scattering microscopy, emerge that stand to benefit from fiber technology, new performance challenges in areas such as laser noise are anticipated. This thesis studies nonlinear pulse propagation in fiber lasers and fiber parametric devices. Applications of dissipative solitons and self-similar pulse propagation to low-repetition rate oscillators that have the potential to simplify short-pulse amplification schemes will be examined. The rest of this thesis focuses on topics relevant to fiber laser development for coherent Raman scattering microscopy sources. Coherent pulse division and recombination inside the laser cavity will be introduced as an energy-scaling mechanism and demonstrated for a fiber soliton laser. The relative intensity noise properties of mode-locked fiber lasers, with a particular emphasis on normal dispersion lasers, will be explored in simulation and experiment. A fiber optical parametric oscillator will be studied in detail for low noise frequency conversion of picosecond pulses, and its utility for coherent Raman imaging will be demonstrated. Spectral compression of femtosecond pulses is used to generate picosecond pulses to pump this device, and this technique provides a route to future noise reduction in the system. Furthermore, this device forms a multimodal source capable of providing the picosecond pulses for coherent Raman scattering microscopy and the
Shape recognition of acoustic scatterers using the singularity expansion method
Cao, Pei; Wu, Jiu Hui
2017-03-01
Acoustic target recognition for two-dimensional (2D) acoustic scatterers is investigated using the singularity expansion method (SEM). Based on the Watson transformation series of the scattering field, the SEM poles can be calculated and their physical interpretation given, along with the exact normal mode for any acoustic scattering problem. Typical oscillatory phenomena appear as a series of damped sinusoidal signals in the time domain and as a standing-wave distribution in the space. These external oscillation modes are associated with the SEM poles. We note that the positions of these poles in the complex frequency plane are uniquely determined by the shape and flexible characteristics of the target regardless of the waveforms and positions of the incident signals. We then infer that SEM poles can be used as the characteristic parameters for target shape recognition. The relationship between the positions of SEM poles and the geometrical characters of 2D scatterers has been established not only for cylinders but also for other general 2D scatterers. The new method and the related calculation results provide an effective way to perform shape recognition using an acoustic scattering field, with potential applications in non-destructive testing and acoustic imaging.
Development of a YAG laser system for the edge Thomson scattering system in ITER.
Hatae, T; Yatsuka, E; Hayashi, T; Yoshida, H; Ono, T; Kusama, Y
2012-10-01
A prototype YAG laser system for the edge Thomson scattering system in ITER has been newly developed. Performance of the laser amplifier was improved by using flow tubes made of samarium-doped glass; the small signal gain reached 20 at its maximum. As a result, an output energy of 7.66 J at 100 Hz was successfully achieved, and the performance exceeded the target performance (5 J, 100 Hz).
Electron-Helium Scattering in a Bichromatic Laser Field in the Second-Order Born Approximation
Institute of Scientific and Technical Information of China (English)
ZHOU Bin; LI Shu-Min
2009-01-01
@@ The elastic scattering of electrons in atomic helium assisted by a bichromatic laser field is investigated in the second order Born approximation. The target atom is approximated by a simple screening potential. The dependence of the differential cross section on the relative phase between the two laser components is calculated, and compared with the recent results of first order Born approximation [Sun J F, Liang M C and Zhu Z L 2007Chin. Phys. Lett. 24 2572].
Widely tunable linear-cavity multiwavelength fiber laser with distributed Brillouin scattering
Institute of Scientific and Technical Information of China (English)
M. Ajiya; M. H. Al-Mansoori; M. A. Mahdi
2011-01-01
We demonstrate a multiple wavelength Brillouin/erbium fiber laser in a linear cavity configuration. The laser cavity is made up of a fiber loop mirror on one end of the resonator and a virtual mirror generated from the distributed stimulated Brillouin scattering effect on the other end. Due to the weak reflectivity provided by the virtual mirror, self-lasing cavity modes are completely suppressed from the laser cavity. At Brillouin pump and 1480-nm pump powers of 2 and 130 mW, respectively, 11 channels of the demonstrated laser with an average total power of 7.13 dBm can freely be tuned over a span of 37-nm wavelength from 1530 to 1567 nm.%@@ We demonstrate a multiple wavelength Brillouin/erbium fiber laser in a linear cavity configuration.The laser cavity is made up of a fiber loop mirror on one end of the resonator and a virtual mirror generated from the distributed stimulated Brillouin scattering effect on the other end.Due to the weak reflectivity provided by the virtual mirror, self-lasing cavity modes are completely suppressed from the laser cavity.At Brillouin pump and 1480-nm pump powers of 2 and 130 mW, respectively, 11 channels of the demonstrated laser with an average total power of 7.13 dBm can freely be tuned over a span of 37-nm wavelength from 1530 to 1567 nm.
A microfluidic laser scattering sensor for label-free detection of waterborne pathogens
Wei, Huang; Yang, Limei; Li, Feng
2016-10-01
A microfluidic-based multi-angle laser scattering (MALS) sensor capable of acquiring scattering pattern of single particle is demonstrated. The size and relative refractive index (RI) of polystyrene (PS) microspheres were deduced with accuracies of 60 nm and 0.001 by analyzing the scattering patterns. We measured scattering patterns of waterborne parasites i.e., cryptosporidium parvum (c.parvum) and giardia lamblia (g.lamblia), and some other representative species in 1 L water within 1 hour, and the waterborne parasites were identified with accuracy better than 96% by classification of distinctive scattering patterns with a support-vector-machine (SVM) algorithm. The system provides a promising tool for label-free and rapid detection of waterborne parasites.
Strong-field QED processes in short laser pulses. One- and two-photon Compton scattering
Energy Technology Data Exchange (ETDEWEB)
Seipt, Daniel
2012-12-20
The purpose of this thesis is to advance the understanding of strong-field QED processes in short laser pulses. The processes of non-linear one-photon and two-photon Compton scattering are studied, that is the scattering of photons in the interaction of relativistic electrons with ultra-short high-intensity laser pulses. These investigations are done in view of the present and next generation of ultra-high intensity optical lasers which are supposed to achieve unprecedented intensities of the order of 10{sup 24} W/cm{sup 2} and beyond, with pulse lengths in the order of some femtoseconds. The ultra-high laser intensity requires a non-perturbative description of the interaction of charged particles with the laser field to allow for multi-photon interactions, which is beyond the usual perturbative expansion of QED organized in powers of the fine structure constant. This is achieved in strong-field QED by employing the Furry picture and non-perturbative solutions of the Dirac equation in the presence of a background laser field as initial and final state wave functions, as well as the laser dressed Dirac-Volkov propagator. The primary objective is a realistic description of scattering processes with regard to the finite laser pulse duration beyond the common approximation of infinite plane waves, which is made necessary by the ultra-short pulse length of modern high-intensity lasers. Non-linear finite size effects are identified, which are a result of the interplay between the ultra-high intensity and the ultra-short pulse length. In particular, the frequency spectra and azimuthal photon emission spectra are studied emphasizing the differences between pulsed and infinite laser fields. The proper description of the finite temporal duration of the laser pulse leads to a regularization of unphysical infinities (due to the infinite plane-wave description) of the laser-dressed Dirac-Volkov propagator and in the second-order strong-field process of two-photon Compton
Xin, Qi; Zhi Ling, Hou; Jian Long, Tian; Zhu, Yu
2006-08-01
The aim was to develop a simple and rapid method for determination of fat and protein content in milk. Based on the laser light scattering theory, the ratio of the scattered light (at 90±0.05° scattering angles) intensity to the transmitted light intensity, which is called scattered-transmitted-ratio method, is adopted as the optical parameter representing the milk fat content and the protein content. In this way, the influence of the fluctuation of the power of the light source is eliminated and the accuracy of determination is improved accordingly. The system we use is real-time and can satisfy the challenging requirements of dairy farming. Results of this study indicate the feasibility of using this technology for fresh milk fat and protein analysis. The fat contents and protein contents of 50 milk samples determined by this method were consistent with the values obtained by the reference methods based on Rose-Gottlieb method and Kjeldahl determination of N method. In this paper, the operating principle of the instrument is introduced and the influence of the environmental conditions, such as the homogenization pressure and homogenization temperature, etc. on the result of the test is analyzed. Through data analysis, the concrete schemes for testing the fat using the curve fitting and testing the protein using the surface fitting technique are determined. Finally, the difference from the reference values of the test is discussed.
Reduced Brillouin scattering from multiline CO2 laser interaction with a plasma
Giles, R.; Fedosejevs, R.; Offenberger, A. A.
1982-08-01
Experimental verification of reduced stimulated Brillouin scattering (SBS) is reported for multiline CO2 laser radiation interacting with high-density plasma. For long-pulse (40-nsec) irradiation SBS was observed to decrease from 15% to a negligible level when the spectrum of the incident laser pulse was changed from 1 to 2 or more well-separated frequencies. Results for both long- and short-pulse multiline laser conditions are in general accord with the expected behavior for varying Δωγ0, where Δω is the frequency separation and γ0 is the homogeneous growth rate.
Numerical methods for analyzing electromagnetic scattering
Lee, S. W.; Lo, Y. T.; Chuang, S. L.; Lee, C. S.
1985-01-01
Attenuation properties of the normal modes in an overmoded waveguide coated with a lossy material were analyzed. It is found that the low-order modes, can be significantly attenuated even with a thin layer of coating if the coating material is not too lossy. A thinner layer of coating is required for large attenuation of the low-order modes if the coating material is magnetic rather than dielectric. The Radar Cross Section (RCS) from an uncoated circular guide terminated by a perfect electric conductor was calculated and compared with available experimental data. It is confirmed that the interior irradiation contributes to the RCS. The equivalent-current method based on the geometrical theory of diffraction (GTD) was chosen for the calculation of the contribution from the rim diffraction. The RCS reduction from a coated circular guide terminated by a PEC are planned schemes for the experiments are included. The waveguide coated with a lossy magnetic material is suggested as a substitute for the corrugated waveguide.
Fuentes-Edfuf, Yasser; Garcia-Lechuga, Mario; Puerto, Daniel; Florian, Camilo; Garcia-Leis, Adianez; Sanchez-Cortes, Santiago; Solis, Javier; Siegel, Jan
2017-07-04
Periodic structures of alternating amorphous-crystalline fringes have been fabricated in silicon using repetitive femtosecond laser exposure (800 nm wavelength and 120 fs duration). The method is based on the interference of the incident laser light with far- and near-field scattered light, leading to local melting at the interference maxima, as demonstrated by femtosecond microscopy. Exploiting this strategy, lines of highly regular amorphous fringes can be written. The fringes have been characterized in detail using optical microscopy combined modelling, which enables a determination of the three-dimensional shape of individual fringes. 2D micro-Raman spectroscopy reveals that the space between amorphous fringes remains crystalline. We demonstrate that the fringe period can be tuned over a range of 410 nm - 13 µm by changing the angle of incidence and inverting the beam scan direction. Fine control over the lateral dimensions, thickness, surface depression and optical contrast of the fringes is obtained via adjustment of pulse number, fluence and spot size. Large-area, highly homogeneous gratings composed of amorphous fringes with micrometer width and millimeter length can readily be fabricated. The here presented fabrication technique is expected to have applications in the fields of optics, nanoelectronics, and mechatronics and should be applicable to other materials.
Lasering in a Waveguide with Scatterers in Diameter 20 nm
Institute of Scientific and Technical Information of China (English)
LIU Chun-Xu; LIU Jun-Ye; ZHANG Jia-Hua; DOU Kai
2004-01-01
We report random lasing achieved in a MEH-PPV/glass waveguide with the TiO2 scatterers in diameter 20nm that is significantly smaller than submicrometre of TiO2 scatterers in the films or suspensions previously reported on random lasing. The spectral lines are dramatically narrowed by almost two orders of magnitude compared with those excited by a xenon lamp. The amplified spontaneous emission is identified as the dominant mechanism in our system. Light localization might be achieved in a broad class of random materials based on the features of the mean free path l* = 5.4 × 105 nm, kl* > 1 and the Thouless number 6.73 × 10-5 with k being the wave number.
Nonlinear images of scatterers in chirped pulsed laser beams
Institute of Scientific and Technical Information of China (English)
Hu Yong-Hua; Wang You-Wen; Wen Shuang-Chun; Fan Dian-Yuan
2010-01-01
The bandwidth and the duration of incident pulsed beam are proved to play important roles in modifying the nonlinear image of amplitude-type scatterer.It is found that the initially positive chirp-type bandwidth can suppress the nonlinear image,while the negative one can enhance it,and that both effects are inversely proportional to the incident pulse duration.Numerical simulations further demonstrate that the location of nonlinear image is at the conjugate plane of the scatterer and that,for negatively pre-chirped pulsed beam,the nonlinear image peak intensity can be higher than that in the corresponding monochromatic case under certain conditions.Moreover the effect of group velocity dispersion on nonlinear image is found to be similar to that of chirp-type bandwidth.
Variational methods in electron-atom scattering theory
Nesbet, Robert K
1980-01-01
The investigation of scattering phenomena is a major theme of modern physics. A scattered particle provides a dynamical probe of the target system. The practical problem of interest here is the scattering of a low energy electron by an N-electron atom. It has been difficult in this area of study to achieve theoretical results that are even qualitatively correct, yet quantitative accuracy is often needed as an adjunct to experiment. The present book describes a quantitative theoretical method, or class of methods, that has been applied effectively to this problem. Quantum mechanical theory relevant to the scattering of an electron by an N-electron atom, which may gain or lose energy in the process, is summarized in Chapter 1. The variational theory itself is presented in Chapter 2, both as currently used and in forms that may facilitate future applications. The theory of multichannel resonance and threshold effects, which provide a rich structure to observed electron-atom scattering data, is presented in Cha...
Spin dynamics in Kapitza-Dirac scattering of electrons from bichromatic laser fields
Dellweg, Matthias M; Müller, Carsten
2016-01-01
Kapitza-Dirac scattering of nonrelativistic electrons from counterpropagating bichromatic laser waves of linear polarization i s studied. The focus lies on the electronic spin dynamics in the Bragg regime when the laser fields possess a frequency ratio of two. To this end, the time-dependent Pauli equation is solved numerically, both in coordinate space and momentum space. Our numerical results are corroborated by analytical derivations. We demonstrate that, for certain incident electron momenta, the scattering crucially relies on the electron spin which undergo es characteristic Rabi-like oscillations. A parameter regime is identified where the Rabi oscillations reach maximum amplitude. We also briefly discuss spin-dependent Kapitza-Dirac scattering of protons.
The second Born approximation in electron-helium scattering in a Nd-YAG laser field
Energy Technology Data Exchange (ETDEWEB)
Khalil, D.; Makhoute, A.; Rahali, G.; Zitane, M. [Universite Moulay Ismail, UFR de Physique Atomique, Moleculaire et Optique Appliquee, Faculte des Sciences (Morocco); Rahali, G.; Makhoute, A. [The Abdus Salam International Centre for Theoretical Physics, Trieste (Italy); Maquet, A. [Universite Pierre et Marie Curie, Lab. de Chimie Physique, Matiere et Rayonnement, 75 - Paris (France)
2007-02-15
The dynamics of laser-assisted elastic collisions in helium is studied using the second-order Born approximation. Detailed calculations of the scattering amplitudes are performed by using the Sturmian basis expansion. Differential cross sections for elastic scattering with the net absorption/emission of up to two photons are calculated for collision energies of 5 eV, 10 eV, and 20 eV. We discuss the influence of the low-energy electrons on the differential cross section (DCS) as a function of the scattering angle for selected choices of the laser frequency and the number of photons exchanged between the external field and electron-helium system. (authors)
X-ray Thomson scattering measurements from hohlraum-driven spheres on the OMEGA laser
Saunders, A. M.; Jenei, A.; Döppner, T.; Falcone, R. W.; Kraus, D.; Kritcher, A.; Landen, O. L.; Nilsen, J.; Swift, D.
2016-11-01
X-ray Thomson scattering (XRTS) is a powerful diagnostic for probing warm and hot dense matter. We present the design and results of the first XRTS experiments with hohlraum-driven CH2 targets on the OMEGA laser facility at the Laboratory for Laser Energetics in Rochester, NY. X-rays seen directly from the XRTS x-ray source overshadow the elastic scattering signal from the target capsule but can be controlled in future experiments. From the inelastic scattering signal, an average plasma temperature is inferred that is in reasonable agreement with the temperatures predicted by simulations. Knowledge gained in this experiment shows a promising future for further XRTS measurements on indirectly driven OMEGA targets.
Photon generation by laser-Compton scattering at the KEK-ATF
Miyoshi, Shuhei; Araki, Sakae; Funahashi, Yoshisato; Hirose, Tachishige; Honda, Yosuke; Kuriki, Masao; Li, Xiao; Okugi, Toshiyuki; Omori, Tsunehiko; Pei, Guoxi; Sakaue, Kazuyuki; Shimizu, Hirotaka; Takahashi, Tohru; Terunuma, Nobuhiro; Urakawa, Junji; Ushio, Yasuaki; Washio, Masakazu
2010-01-01
We performed a photon generation experiment by laser-Compton scattering at the KEK-ATF, aiming to develop a Compton based polarized positron source for linear colliders. In the experiment, laser pulses with a 357 MHz repetition rate were accumulated and their power was enhanced by up to 250 times in the Fabry-Perot optical resonant cavity. We succeeded in synchronizing the laser pulses and colliding them with the 1.3 GeV electron beam in the ATF ring while maintaining the laser pulse accumulation in the cavity. As a result, we observed 26.0 +/- 0.1 photons per electron-laser pulse crossing, which corresponds to a yield of 10^8 photons in a second.
Institute of Scientific and Technical Information of China (English)
梁善勇†; 王江安; 宗思光; 吴荣华; 马治国; 王晓宇; 王乐东
2013-01-01
It is the research foundation of ship wake detection by laser and new-generation optical homing torpedo to investigate the influence of multiple scattering effect on light scattering intensity and polarization characteristics of the ship wake bubbles. The simulation model of laser back-scattering detection by ship wake bubbles is based on vector Monte Carlo method, and the multiple scattering mechanism is studied. The influences of multiple scattering effect and the bubble density in ship wake on the light scattering intensity and polarization characteristics of echo signal are analyzed. The echo photon polarization contribution reception method and the echo signal polarization statistical method are proposed to solve the problem that the low photon return probability cannot form the echo energy in the system with small receiver field of view. These methods are based on the basic idea of the particle collision importance sampling and the traditional energy receiving method. The polarization detection experimental platform for the simulated wake bubbles is built and the accuracy of the simulation results is verified in experiment. The consistence of the experimental and simulation results shows that the bubble distance and density information can be characterized by echo intensity, polarization information and the echo signal intensity, and the polarization characteristics can be used to detect and distinguish the ship wake bubbles, or even a low density wake bubbles with high precision.% 研究多重散射效应对舰船尾流气泡群光散射强度和偏振特征的影响是舰船光尾流探测以及新型光自导鱼雷研究的基础。基于矢量Monte Carlo方法建立了舰船尾流气泡群激光后向探测仿真模型，重点研究了尾流气泡群的多重散射机理，分析了多重散射效应、尾流气泡群密度对回波信号强度和偏振特征的影响规律。基于粒子碰撞重要性抽样的基本思想，在传统能量接收
Benchmarking the inelastic neutron scattering soil carbon method
The herein described inelastic neutron scattering (INS) method of measuring soil carbon was based on a new procedure for extracting the net carbon signal (NCS) from the measured gamma spectra and determination of the average carbon weight percent (AvgCw%) in the upper soil layer (~8 cm). The NCS ext...
Chen, Junchi; Su, Hongpeng; Peng, Yujie; Guo, Xiaoyang; Wang, Zhanshan; Leng, Yuxin
2017-01-01
A modified polarized beam combination technique is proposed for preserving the temporal waveforms of stimulated Raman scattering. 1064 nm pre-pulse pumping lasers prior to the main pumping laser with a delay time are generated and injected into a Ba(NO3)2 Raman medium to excite the crystal firstly. The influences of pre-pulse lasers with various energy levels on the temporal shapes of Raman lasers are investigated, and it is demonstrated that the temporal waveforms of the Raman laser are distorted once the energies of the pre-pulse are below and above the required energy for preserving the temporal shapes of Stokes radiation. It is also discovered that the temporal shape of the 1197 nm Raman laser cannot be perfectly preserved if the energy of the 1064 nm main laser is too low or the relative delay time is too large. Moreover, the optical conversion efficiency and Stokes laser energy obtained under pumping lasers with single and double intensity peaks are compared.
Halo-independent methods for inelastic dark matter scattering
Bozorgnia, Nassim; Schwetz, Thomas; Zupan, Jure
2013-01-01
We present halo-independent methods to analyze the results of dark matter direct detection experiments assuming inelastic scattering. We focus on the annual modulation signal reported by DAMA/LIBRA and present three different halo-independent tests. First, we compare it to the upper limit on the unmodulated rate from XENON100 using (a) the trivial requirement that the amplitude of the annual modulation has to be smaller than the bound on the unmodulated rate, and (b) a bound on the annual modulation amplitude based on an expansion in the Earth's velocity. The third test uses the special predictions of the signal shape for inelastic scattering and allows for an internal consistency check of the data without referring to any astrophysics. We conclude that a strong conflict between DAMA/LIBRA and XENON100 in the framework of spin-independent inelastic scattering can be established independently of the local properties of the dark matter halo.
Spatial resolution with a CO sub 2 laser scattering experiment on TORE SUPRA
Energy Technology Data Exchange (ETDEWEB)
Laviron, C.; Devynck, P.; Garbet, X.; Payan, J.; Saha, S.K. (CEA Centre d' Etudes Nucleaires de Cadarache, 13 - Saint-Paul-les-Durance (France)); Truc, A.; Quemeneur, A.; Hennequin, P.; Gresillon, D.; Gervais, F. (Ecole Polytechnique, 91 - Palaiseau (France). Lab. de Physique des Milieux Ionises)
1991-01-01
The ALTAIR diagnostic has been developed to analyse the density fluctuations with wavelength between 0.2 and 2 cm in the tokamak TORE SUPRA. These fluctuations are measured by coherent Thomson scattering of a CO{sub 2} laser beam. The localisation of the fluctuations is an important aspect in a scattering experiment in a tokamak. For small scattering angles ({proportional to}1 mrad) the transverse resolution is excellent: The diameter of the beam (5cm) is very small compared to the diamter of the plasma (160cm). Conversely, there is no resolution along the observation direction because the length of the scattering volume is larger than the diameter of the plasma. (orig.).
Spatial resolution with a CO{sub 2} laser scattering experiment on TORE SUPRA
Energy Technology Data Exchange (ETDEWEB)
Laviron, C.; Devynck, P.; Garbet, X.; Payan, J.; Saha, S.K. [Association Euratom-CEA, Centre d`Etudes Nucleaires de Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. de Recherches sur la Fusion Controlee; Truc, A.; Quemeneur, A.; Hennequin, P.; Gresillon, D.; Gervais, F. [Ecole Polytechnique, 91 - Palaiseau (France). Lab. de Physique des Milieux Ionises
1991-12-31
The ALTAIR diagnostic has been developed to analyse the density fluctuations with wavelength between 0.2 and 2 cm in the tokamak TORE SUPRA. These fluctuations are measured by coherent Thomson scattering of a CO{sub 2} laser beam. The localisation of the fluctuations is an important aspect in a scattering experiment in a tokamak. For small scattering angles ({approx} 1 mrad) the transverse resolution is excellent; the diameter of the beam (5cm) is very small compared to the diameter of the plasma (160cm). Conversely, there is no resolution along the observation direction because the length of the scattering volume is larger than the diameter of the plasma. If we take into account the helicity of the magnetic field lines in the tokamak, adding the fact that the turbulence wave vector is mainly perpendicular to these field lines, some resolution can be obtained along the direction of the beam.
Thomson scattering from near-solid density plasmas using soft x-ray free electron lasers
Höll, A
2006-01-01
We propose a collective Thomson scattering experiment at the VUV free electron laser facility at DESY (FLASH) which aims to diagnose warm dense matter at near-solid density. The plasma region of interest marks the transition from an ideal plasma to a correlated and degenerate many-particle system and is of current interest, e.g. in ICF experiments or laboratory astrophysics. Plasma diagnostic of such plasmas is a longstanding issue. The collective electron plasma mode (plasmon) is revealed in a pump-probe scattering experiment using the high-brilliant radiation to probe the plasma. The distinctive scattering features allow to infer basic plasma properties. For plasmas in thermal equilibrium the electron density and temperature is determined from scattering off the plasmon mode.
Thomson scattering from near-solid density plasmas using soft x-ray free electron lasers
Energy Technology Data Exchange (ETDEWEB)
Holl, A; Bornath, T; Cao, L; Doppner, T; Dusterer, S; Forster, E; Fortmann, C; Glenzer, S H; Gregori, G; Laarmann, T; Meiwes-Broer, K H; Przystawik, A; Radcliffe, P; Redmer, R; Reinholz, H; Ropke, G; Thiele, R; Tiggesbaumker, J; Toleikis, S; Truong, N X; Tschentscher, T; Uschmann, I; Zastrau, U
2006-11-21
We propose a collective Thomson scattering experiment at the VUV free electron laser facility at DESY (FLASH) which aims to diagnose warm dense matter at near-solid density. The plasma region of interest marks the transition from an ideal plasma to a correlated and degenerate many-particle system and is of current interest, e.g. in ICF experiments or laboratory astrophysics. Plasma diagnostic of such plasmas is a longstanding issue. The collective electron plasma mode (plasmon) is revealed in a pump-probe scattering experiment using the high-brilliant radiation to probe the plasma. The distinctive scattering features allow to infer basic plasma properties. For plasmas in thermal equilibrium the electron density and temperature is determined from scattering off the plasmon mode.
Bito, Kotatsu; Okuno, Masanari; Kano, Hideaki; Leproux, Philippe; Couderc, Vincent; Hamaguchi, Hiro-o.
2013-06-01
We have developed a three-pulse non-degenerate multiplex coherent Raman microspectroscopic system using a white-light laser source. The fundamental output (1064 nm) of a Nd:YAG laser is used for the pump radiation with the white-light laser output (1100-1700 nm) for the Stokes radiation to achieve broadband multiplex excitations of vibrational coherences. The second harmonic (532 nm) of the same Nd:YAG laser is used for the probe radiation. Thanks to the large wavelength difference between the pump and probe radiations, coherent anti-Stokes Raman scattering (CARS) and coherent Stokes Raman scattering (CSRS) can be detected simultaneously. Simultaneous detection of CARS and CSRS enables us to obtain information on the electronic resonance effect that affects differently the CARS and CSRS signals. Simultaneous analysis of the CARS and CSRS signals provides us the imaginary part of χ(3) without introducing any arbitrary parameter in the maximum entropy method (MEM).
Martin, Chris; Ben-Yakar, Adela
2016-11-01
Ultrafast laser surgery of tissue requires precise knowledge of the tissue's optical properties to control the extent of subsurface ablation. Here, we present a method to determine the scattering lengths, ℓs, and fluence thresholds, Fth, in multilayered and turbid tissue by finding the input energies required to initiate ablation at various depths in each tissue layer. We validated the method using tissue-mimicking phantoms and applied it to porcine vocal folds, which consist of an epithelial (ep) layer and a superficial lamina propia (SLP) layer. Across five vocal fold samples, we found ℓ=51.0±3.9 μm, F=1.78±0.08 J/cm2, ℓ=26.5±1.6 μm, and F=1.14±0.12 J/cm2. Our method can enable personalized determination of tissue optical properties in a clinical setting, leading to less patient-to-patient variability and more favorable outcomes in operations, such as femto-LASIK surgery.
Energy Technology Data Exchange (ETDEWEB)
Rehman, Haseeb ur; Lee, Jiyoung; Kim, Yonghee [KAIST, Daejeon (Korea, Republic of)
2015-10-15
This paper also presents sensitivity analysis to yield the maximum possible photo-transmutation rates. In general the possibility of radionuclide transmutation using photo-neutron reaction is evaluated in this work. In this paper a detailed methodology to calculate transmutation reaction rates using Laser Induced Bremsstrahlung (LIB) and Laser Compton Scattering (LCS) has been discussed. The methodology was validated by comparing the calculated reaction rates against published data in publically accessed literatures. In the second half of the paper, the authors present a novel concept to narrow down the LCS photon spectrum to an energy range that matches with the resonance region of a particular radionuclide. This is particularly useful considering hazardous waste is usually a mix of different isotopes. As such, being able to tune the LCS photon into any narrow energy range so as to selectively transmute any particular isotope of interest in the hazardous waste mixture would be very desirable. LCS spectrum is highly sensitive to the electron beam energy, laser power, laser luminosity and Compton backscattering angle. From the results it is quite evident that LCS is much better option for the radionuclide transmutation as reaction rates for the LCS is much higher than LIB method even for very small laser power. It can be seen even for the optimistic reaction rate calculations with Bremsstrahlung method reaction rate is much lower than LCS case for 10 Hz repetition rate. If repetition rate of laser 100 Hz then LIB reaction rate has the same order of the magnitude as the reaction rate via LCS. Higher Laser Powers can yield very high transmutation rates.
Hirst, Evan; Thompson, Oliver; Andrews, Mike
2013-02-01
The retina/choroid structure is an example of a complex biological target featuring highly perfused tissues and vessel flows both near the surface and at some depth. Laser speckle imaging can be used to image blood flows but static scattering paths present a problem for extracting quantifiable data. The speckle contrast is artificially increased by any residual specular reflection and light paths where no moving scatterers are encountered. Here we present results from phantom experiments demonstrating that the static and dynamic contributions to laser speckle contrast can be separated when camera exposures of varying duration are used. The stationary contrast parameter follows the thickness and strength of the overlying scatterer while the dynamic proportion of the scatter resulting from vessel flows and Brownian motion is unchanged. The importance of separating the two scatter components is illustrated by in vivo measurements from a scarred human retina, where the effect of the un-perfused scar tissue can be decoupled from the dynamic speckle from the intact tissue beneath it.
Determining Complex Structures using Docking Method with Single Particle Scattering Data
Directory of Open Access Journals (Sweden)
Haiguang Liu
2017-04-01
Full Text Available Protein complexes are critical for many molecular functions. Due to intrinsic flexibility and dynamics of complexes, their structures are more difficult to determine using conventional experimental methods, in contrast to individual subunits. One of the major challenges is the crystallization of protein complexes. Using X-ray free electron lasers (XFELs, it is possible to collect scattering signals from non-crystalline protein complexes, but data interpretation is more difficult because of unknown orientations. Here, we propose a hybrid approach to determine protein complex structures by combining XFEL single particle scattering data with computational docking methods. Using simulations data, we demonstrate that a small set of single particle scattering data collected at random orientations can be used to distinguish the native complex structure from the decoys generated using docking algorithms. The results also indicate that a small set of single particle scattering data is superior to spherically averaged intensity profile in distinguishing complex structures. Given the fact that XFEL experimental data are difficult to acquire and at low abundance, this hybrid approach should find wide applications in data interpretations.
Simple synchronization technique of a mode-locked laser for Laser-Compton scattering γ-ray source
Mori, Michiaki; Kosuge, Atsushi; Kiriyama, Hiromitsu; Hajima, Ryoichi; Kondo, Kiminori
2016-06-01
We propose a simple and effective synchronization technique between a reference electrical oscillator and a mode-locked laser for a narrowband picosecond Laser-Compton scattering γ-ray source by using a commercial-based 1-chip frequency synthesizer, which is widely used in radio communication. The mode-locked laser has been successfully synchronized in time with a jitter of 180 fs RMS for 10 Hz-100 kHz bandwidth. A good stability of 640 μHz at 80 MHz repetition rate for 10 h operation has also been confirmed. We discuss in detail the design and performance of this technique (in terms of timing jitter, stability, and validity).
Tiutiunnyk, A.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. M.; Restrepo, R. L.; Ungan, F.; Martínez-Orozco, J. C.; Kasapoglu, E.; Duque, C. A.
2017-02-01
In this work we shall present a study of inelastic light scattering involving inter-subband electron transitions in coupled GaAs-(Ga,Al)As quantum wells. Calculations include the electron related Raman differential cross section and Raman gain. The effects of an external nonresonant intense laser field are used in order to tune these output properties. The confined electron states will be described by means of a diagonalization procedure within the effective mass and parabolic band approximations. It is shown that the application of the intense laser field can produce values of the intersubband electron Raman gain above 400 cm-1. The system proposed here is an alternative choice for the development of AlxGa1-xAs semiconductor laser diodes that can be tuned via an external nonresonant intense laser field.
Davies, Emlyn J; Nimmo-Smith, W Alex M; Agrawal, Yogesh C; Souza, Alejandro J
2011-12-05
The use of laser diffraction is now common practice for the determination of an in situ particle size distribution in the marine environment. However, various imaging techniques have shown that particles vary greatly in shape, leading to uncertainty in the response of laser diffraction instruments when subjected to this diverse range of complex particles. Here we present a novel integrated system which combines both digital in-line holography and a LISST-100 type C, to simultaneously record in-focus images of artificial and natural particles with their small-angle forward scattering signature. The system will allow for further development of a reliable alternative to Mie Theory when using laser diffraction for the in situ measurement of complex suspended particles. A more detailed knowledge of the performance of laser diffraction when subjected to the wide variety of complex particles found in the marine environment will then be possible.
Zhidkov, A.; Masuda, S.; Bulanov, S. S.; Koga, J.; Hosokai, T.; Kodama, R.
2014-05-01
Nonlinear cascade scattering of intense, tightly focused laser pulses by relativistic electrons is studied numerically in the classical approximation including radiation damping for the quantum parameter ⟨ℏωxray⟩/ɛ <1 and an arbitrary radiation parameter χ. The electron's energy loss, along with its being scattered to the side by the ponderomotive force, makes scattering in the vicinity of a high laser field nearly impossible at high electron energies. The use of a second, copropagating laser pulse as a booster is shown to partially solve this problem.
Structured x-ray beams from twisted electrons by inverse Compton scattering of laser light
Seipt, D; Fritzsche, S
2014-01-01
The inverse Compton scattering of laser light on high-energetic twisted electrons is investigated with the aim to construct spatially structured x-ray beams. In particular, we analyze how the properties of the twisted electrons, such as the topological charge and aperture angle of the electron Bessel beam, affects the energy and angular distribution of scattered x-rays. We show that with suitably chosen initial twisted electron states one can synthesize tailor-made x-ray beam profiles with a well-defined spatial structure, in a way not possible with ordinary plane-wave electron beams.
Sentinel lymph node detection by an optical method using scattered photons
Tellier, Franklin; Ravelo, Rasata; Simon, Hervé; Chabrier, Renée; Steibel, Jérôme; Poulet, Patrick
2010-01-01
We present a new near infrared optical probe for the sentinel lymph node detection, based on the recording of scattered photons. A two wavelengths setup was developed to improve the detection threshold of an injected dye: the Patent Blue V dye. The method used consists in modulating each laser diode at a given frequency. A Fast Fourier Transform of the recorded signal separates both components. The signal amplitudes are used to compute relative Patent Blue V concentration. Results on the probe using phantoms model and small animal experimentation exhibit a sensitivity threshold of 3.2 µmol/L, which is thirty fold better than the eye visible threshold. PMID:21258517
HERMITE SCATTERED DATA FITTING BY THE PENALIZED LEAST SQUARES METHOD
Institute of Scientific and Technical Information of China (English)
Tianhe Zhou; Danfu Han
2009-01-01
Given a set of scattered data with derivative values. If the data is noisy or there is an extremely large number of data, we use an extension of the penalized least squares method of von Golitschek and Schumaker[Serdica, 18 (2002), pp.1001-1020]to fit the data. We show that the extension of the penalized least squares method produces a unique spline to fit the data. Also we give the error bound for the extension method. Some numerical examples are presented to demonstrate the effectiveness of the proposed method.
Near-infraed scattering method for fabric thermal comfort
Directory of Open Access Journals (Sweden)
Gao Shou-Wei
2014-01-01
Full Text Available Wetting behavior of a clothing assembly plays an important role in thermophysiological body comfort. The instruments and methods utilised for testing purposes should adequately quantify wetting parameters of fabric thermal comfort. The surface conductivity method has been used to for moisture management testing in fabrics, but that method cannot give the detailed information for fiber-liquid interaction. With the new near-infrared scattering method, the wetting mechanism is introduced and interpreted through liquid transfer process from an infinite liquid reservoir. Wetting results from two kinds of fabrics show the difference in fabric thermal comfort.
Study on effective laser cleaning method to remove carbon layer from a gold surface
Singh, Amol; Choubey, A. K.; Modi, Mohammed H.; Upadhyaya, B. N.; Lodha, G. S.
2013-03-01
Hydrocarbon cracking and carbon contamination is a common problem in soft x-ray Synchrotron Radiation (SR) beamlines. Carbon contamination on optics is known to absorb and scatter radiation close to the C K-edge (284 eV) spectral region. The purpose of this work is to study and develop a laser cleaning method that can effectively remove the carbon contaminations without damaging the underneath gold-coated optics. The laser cleaning process is a non-contact, accurate, efficient and safe. Nd:YAG laser of 100 ns pulse duration is used for carbon cleaning. The effect of laser pulse duration, laser fluence, number of laser passes, angle of incidence and spot overlapping on the cleaning performance is studied. Cleaning effect and subsequent film quality after laser irradiation is analyzed using x-ray photoelectron spectroscopy (XPS) and soft x-ray reflectivity (SXR) techniques.
Method for forming electrically charged laser targets
Goodman, Ronald K.; Hunt, Angus L.
1979-01-01
Electrically chargeable laser targets and method for forming such charged targets in order to improve their guidance along a predetermined desired trajectory. This is accomplished by the incorporation of a small amount of an additive to the target material which will increase the electrical conductivity thereof, and thereby enhance the charge placed upon the target material for guidance thereof by electrostatic or magnetic steering mechanisms, without adversely affecting the target when illuminated by laser energy.
Visualizing a protein quake with time-resolved X-ray scattering at a free-electron laser
DEFF Research Database (Denmark)
Arnlund, David; Johansson, Linda C.; Wickstrand, Cecilia;
2014-01-01
We describe a method to measure ultrafast protein structural changes using time-resolved wide-angle X-ray scattering at an X-ray free-electron laser. We demonstrated this approach using multiphoton excitation of the Blastochloris viridis photosynthetic reaction center, observing an ultrafast global...... conformational change that arises within picoseconds and precedes the propagation of heat through the protein. This provides direct structural evidence for a 'protein quake': the hypothesis that proteins rapidly dissipate energy through quake-like structural motions....
Scattering from finite size methods in lattice QCD
Feng, Xu; Renner, Dru B
2009-01-01
Using two flavors of maximally twisted mass fermions, we calculate the S-wave pion-pion scattering length in the isospin I=2 channel and the P-wave pion-pion scattering phase in the isospin I=1 channel. In the former channel, the lattice calculations are performed at pion masses ranging from 270 MeV to 485 MeV. We use chiral perturbation theory at next-to-leading order to extrapolate our results. At the physical pion mass, we find m_pi a_pipi(I=2)=-0.04385(28)(38) for the scattering length. In the latter channel, the calculation is currently performed at a single pion mass of 391 MeV. Making use of finite size methods, we evaluate the scattering phase in both the center of mass frame and the moving frame. The effective range formula is employed to fit our results, from which the rho resonance mass and decay width are evaluated.
Surface-enhanced Raman scattering in femtosecond laser-nanostructured Ag substrate
Energy Technology Data Exchange (ETDEWEB)
Dai Ye; He Min; Yan Xiaona; Ma Guohong [Department of Physics, Shanghai University, Shanghai 200444 (China); Lu Bo, E-mail: yedai@shu.edu.cn [Instrumental Analysis and Research Center, Shanghai University, Shanghai 200444 (China)
2011-02-01
We demonstrate that a surface-enhanced Raman scattering (SERS) substrate could be directly fabricated on the surface of Ag film by femtosecond laser micromachining. According to the morphology observation by SEM, an amount of nanoparticles, nanoprotrusions, and nanospikes were found to form in the ablation region and the density and size distribution of these Ag nanoparticles depended possibly on the incident laser intensity. Additionally, a large area of nanostructured region was produced by fast line scanning, and an enhancement factor of {approx}10{sup 5} was obtained in this region after the sample was soaked in the rhodamine 6G solution for 30 min.
Detection of dust grains vibrations with a laser heterodyne receiver of scattered light
Energy Technology Data Exchange (ETDEWEB)
Serozhkin, Yuriy [V. Lashkaryov Institute of Semiconductor Physics, 41, Nauky Prospect, Kyiv 03028 (Ukraine)], E-mail: yuriy.serozhkin@zeos.net; Kollyukh, Olexiy; Venger, Yevgen [V. Lashkaryov Institute of Semiconductor Physics, 41, Nauky Prospect, Kyiv 03028 (Ukraine)
2008-05-15
We present the results of measurement of grains vibrations under external action in gas and liquid with a laser heterodyne receiver of scattered radiation. For investigation of dynamic characteristics of particles we made the laser heterodyne receiver with sensitivity about 2x10{sup -17} W/Hz and source of probing with radiation power 1 mW. In our pilot experiments, measurement of vibration amplitude of nanoparticles in gas (cigarette smoke) and microparticles in fluid (toothpaste in water) was made. We measured values of vibration amplitudes about 20-30 nm.
Stray-light suppression with high-collection efficiency in laser light-scattering experiments
Deilamian, K.; Gillaspy, J. D.; Kelleher, D. E.
1992-01-01
An optical system is described for collecting a large fraction of fluorescent light emitted isotropically from a cylindrical interaction region. While maintaining an overall detection efficiency of 9 percent, the system rejects, by more than 12 orders of magnitude, incident laser light along a single axis that intersects the interaction region. Such a system is useful for a wide variety of light-scattering experiments in which high-collection efficiency is desirable, but in which light from an incident laser beam must be rejected without resorting to spectral filters.
The second Born approximation of electron-argon elastic scattering in a Bichromatic laser field
Zhou, Bin; Wen, Da-Yong
2013-01-01
We study the elastic scattering of atomic argon by electron in the presence of a bichromatic laser field in the second Born approximation. The target atom is approximated by a simple screening potential and the continuum states of the impinging and emitting electrons are described as Volkov states. We evaluate the S-matrix elements numerically. The dependence of differential cross section on the relative phase between the two laser components is presented. The results obtained in the first and second Born approximation are compared and analysed.
Efficient Surface Enhanced Raman Scattering substrates from femtosecond laser based fabrication
Parmar, Vinod; Kanaujia, Pawan K.; Bommali, Ravi Kumar; Vijaya Prakash, G.
2017-10-01
A fast and simple femtosecond laser based methodology for efficient Surface Enhanced Raman Scattering (SERS) substrate fabrication has been proposed. Both nano scaffold silicon (black silicon) and gold nanoparticles (Au-NP) are fabricated by femtosecond laser based technique for mass production. Nano rough silicon scaffold enables large electromagnetic fields for the localized surface plasmons from decorated metallic nanoparticles. Thus giant enhancement (approximately in the order of 104) of Raman signal arises from the mixed effects of electron-photon-phonon coupling, even at nanomolar concentrations of test organic species (Rhodamine 6G). Proposed process demonstrates the low-cost and label-less application ability from these large-area SERS substrates.
Artyukov, I. A.; Dyachkov, N. V.; Feshchenko, R. M.; Polunina, A. V.; Popov, N. L.; Shvedunov, V. I.; Vinogradov, A. V.
2017-05-01
It was medical applications that stimulated F. Carrol in the early 1990s to start the research of on relativistic Thomson scattering X-ray sources, as a part of the infrastructure of the future society. The possibility to use such a source in interventional cardiology is discussed in this paper. The replacement of X-ray tube by relativistic Thomson scattering Xray source is predicted to lower the patient radiation dose by a factor of 3 while image quality remains the same. The required general characteristics of accelerator and laser units are found. They can be reached by existing technology. A semiempirical method for simulation of medical and technical parameters of interventional coronary angiography systems is suggested.
Zhang, Lisheng; Fang, Yan; Zhang, Pengxiang
2008-01-01
The highly ordered anodic aluminum oxide (AAO) template was fabricated using aluminum anodizing in electrolytes with two-step method, which apertures were about 50-80nm. The nickel nanowires with about 40-70nm in diameter was prepared on the AAO template by laser-MBE (molecular beam epitaxy). And high quality Raman spectra of SudanII were obtained on the glass covered with the nickel nanowires. On the nickel nanowires there are both surface enhanced Raman scattering (SERS) and tip enhanced Raman scattering (TERS). The new observations not only enlarge the range of SERS applications, but also imply a possible new enhancement mechanism. Otherwise the Raman and SERS frequencies of SudanII molecule were calculated using, respectively, DFT and B3PW91.
Method for laser spot welding monitoring
Manassero, Giorgio
1994-09-01
As more powerful solid state laser sources appear on the market, new applications become technically possible and important from the economical point of view. For every process a preliminary optimization phase is necessary. The main parameters, used for a welding application by a high power Nd-YAG laser, are: pulse energy, pulse width, repetition rate and process duration or speed. In this paper an experimental methodology, for the development of an electrooptical laser spot welding monitoring system, is presented. The electromagnetic emission from the molten pool was observed and measured with appropriate sensors. The statistical method `Parameter Design' was used to obtain an accurate analysis of the process parameter that influence process results. A laser station with a solid state laser coupled to an optical fiber (1 mm in diameter) was utilized for the welding tests. The main material used for the experimental plan was zinc coated steel sheet 0.8 mm thick. This material and the related spot welding technique are extensively used in the automotive industry, therefore, the introduction of laser technology in production line will improve the quality of the final product. A correlation, between sensor signals and `through or not through' welds, was assessed. The investigation has furthermore shown the necessity, for the modern laser production systems, to use multisensor heads for process monitoring or control with more advanced signal elaboration procedures.
Advanced methods for scattering amplitudes in gauge theories
Energy Technology Data Exchange (ETDEWEB)
Peraro, Tiziano
2014-09-24
We present new techniques for the evaluation of multi-loop scattering amplitudes and their application to gauge theories, with relevance to the Standard Model phenomenology. We define a mathematical framework for the multi-loop integrand reduction of arbitrary diagrams, and elaborate algebraic approaches, such as the Laurent expansion method, implemented in the software Ninja, and the multivariate polynomial division technique by means of Groebner bases.
Transformation optics simulation method for stimulated Brillouin scattering
Zecca, Roberto; Smith, David R; Larouche, Stéphane
2016-01-01
We develop a novel approach to enable the full-wave simulation of stimulated Brillouin scattering and related phenomena in a frequency-domain, finite-element environment. The method uses transformation optics techniques to implement a time-harmonic coordinate transform that reconciles the different frames of reference used by electromagnetic and mechanical finite-element solvers. We show how this strategy can be successfully applied to bulk and guided systems, comparing the results with the predictions of established theory.
Electron-Helium Scattering in Free-Free Transitions in a Bichromatic Laser Field
Institute of Scientific and Technical Information of China (English)
SUN Jin-Feng; LIANG Ming-Chao; ZHU Zun-Lue
2007-01-01
Theoretical calculation of the differential cross section (DCS) for elastic electron-helium scattering in the presence of a bichromatic CO2 laser field is carried out in the first Born approximation with a simple screening electric potential. The two components of the laser field have the frequencies ω and 2ω, which are out of phase by an arbitrary scale ψ. The variations of the differential cross section as a function of the phase angle ψ in the domain 0°≤ψ≤360° are presented. We discuss the influence of the number of photons exchanged on the phase-dependence effect. Moreover, for different scattering angles and incident electron energies, the DCS has outstanding differences. These illustrate that the two parameters have important effects on the differential cross section and the screening electric potential is effective.
A deeper look into magnetic nanostructures using advanced scattering methods
Indian Academy of Sciences (India)
T H Brückel; E Kentzinger; S Mattauch; A Paul; U Rücker; J Voigt
2008-11-01
Magnetic thin film systems and laterally patterned magnetic media are the basis of spintronic devices for information technology. In this contribution, we will show that neutron scattering under grazing incidence with polarization analysis is able to provide unique depth resolved information on magnetization, magnetic correlations and magne-tization dynamics relevant for basic and applied research on nanostructured magnetic materials. It is well established that specular neutron reflectivity with polarization analysis from thin film systems and multilayers provides layer-resolved information on interface rough-ness and on the laterally averaged magnetization. Off-specular diffuse scattering with polarization analysis gives access to lateral correlations, i.e. the detailed interface morphology, the magnetic order of nanoscale objects (stripes or islands), the magnetic fluctuations or domain structure. Depending on the scattering geometry – reflectometry or grazing incidence small angle neutron scattering (GISANS) – correlations on lateral length scales from the nanometer up to the 100 micrometer range become accessible. Close to total reflection, kinematical scattering theory breaks down and dynamical effects have to be taken into account. Simulations in the distorted wave Born approximation (DWBA) allow one to extract quantitative parameters for a statistical model description. On several examples we will demonstrate the power of the method – from the magnetic fluctuations in remanent sputtered films via the magnetic structure of rare earth multilayers with competing interactions to the remagnetization process of exchange bias systems or the domain structures of laterally patterned giant magnetoresistance multilayers. Finally we will give an outlook on what will be possible on next generation instruments such as the magnetism reflectometer MARIA of the Juelich Centre for Neutron Science (JCNS) at FRM-II.
Muon's anomalous magnetic moment effects on laser assisted Coulomb scattering process
Taj, S; Idrissi, M El; Attaourti, Y; Oufni, L
2012-01-01
Laser assisted Coulomb scattering by relativistic electron and heavy electron (muon) is studied by using Salamin waves (Salamin 1993) in the Weak Field Approximation (WFA). Both electron and muon are described by the Dirac equation, with the anomalous magnetic moment effects fully included. The generalization of this paper to heavy electron (muon) gives interesting insights as to how the mass affects the magnitude of the differential cross sections. No significant difference in the muon's DCS with and without AMM effects was detected.
Zhang, Yan; Zhang, Wenqi; Wang, Lin; Wang, Feng; Yang, Haifeng
2017-01-01
We reported a simple and fast method to prepare a composite material of polydopamine (PDA) adlayer covered cubic AgCl core, which was inlaid with Ag nanoparticles (NPs), shortly named as AgCl/PDA/AgNPs. The resultant AgCl/PDA/AgNPs could be employed as surface-enhanced Raman scattering (SERS) substrate for in-situ detection and the SERS activity could be further greatly improved due to the production of more AgNPs upon laser irradiation. With 4-mercaptopyridine (4-Mpy) as the probe molecule, the enhancement factor could reach 107. Additionally, such SERS substrate shows good reproducibility with relative standard deviation of 7.32% and long term stability (after storage for 100 days under ambient condition, SERS intensity decay is less than 25%). In-situ elevating SERS activity of AgCl/PDA/AgNPs induced by laser may be beneficial to sensitive analysis in practical fields.
Energy Technology Data Exchange (ETDEWEB)
Dzierzega, K.; Mendys, A.; Zawadzki, W. [Marian Smoluchowski Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Krakow (Poland); Pokrzywka, B. [Mt. Suhora Observatory, Pedagogical University of Cracow, ul. Podchorazych 2, 30-084 Krakow (Poland); Pellerin, S. [GREMI, site de Bourges, Universite d' Orleans, CNRS, rue Gaston Berger BP 4043, 18028 Bourges (France)
2013-04-01
Thomson and Rayleigh scattering methods were applied to quantify the electron and heavy particle temperatures, as well as electron number density, in a laser spark in helium at atmospheric pressure. Plasma was created using 4.5 ns, 25 mJ pulses from Nd:YAG laser at 532 nm. Measurements, performed for the time interval between 20 ns and 800 ns after breakdown, show electron density and temperature to decrease from 7.8 Multiplication-Sign 10{sup 23} m{sup -3} to 2.6 Multiplication-Sign 10{sup 22} m{sup -3} and from 95 900 K to 10 350 K, respectively. At the same time, the heavy particle temperature drops from only 47 000 K down to 4100 K which indicates a two temperature plasma out of local isothermal equilibrium.
Institute of Scientific and Technical Information of China (English)
S. H. Kim
2009-01-01
We derive the cross section of scattering through the three-quantum interaction of an electron with the incident laser field, the emitted photon, and an axial electrostatic field produced by the magnetic wiggler in the magnetic wiggler acting as the sole zeroth-order perturbing classical field in the first free-electron laser (FEL). In the derivation, we apply quantum-wiggler electrodynamics (QWD). We find that this scattering predominates the usual two-quantum scattering. The output power of spontaneous free-electron two-quantum Stark emission driven by the above electrostatic field attenuated by the three-quantum scattering agrees within a factor of 10 with the measured power in the case of the first FEL.
Correction of optical absorption and scattering variations in Laser Speckle Rheology measurements.
Hajjarian, Zeinab; Nadkarni, Seemantini K
2014-03-24
Laser Speckle Rheology (LSR) is an optical technique to evaluate the viscoelastic properties by analyzing the temporal fluctuations of backscattered speckle patterns. Variations of optical absorption and reduced scattering coefficients further modulate speckle fluctuations, posing a critical challenge for quantitative evaluation of viscoelasticity. We compare and contrast two different approaches applicable for correcting and isolating the collective influence of absorption and scattering, to accurately measure mechanical properties. Our results indicate that the numerical approach of Monte-Carlo ray tracing (MCRT) reliably compensates for any arbitrary optical variations. When scattering dominates absorption, yet absorption is non-negligible, diffusing wave spectroscopy (DWS) formalisms perform similar to MCRT, superseding other analytical compensation approaches such as Telegrapher equation. The computational convenience of DWS greatly simplifies the extraction of viscoelastic properties from LSR measurements in a number of chemical, industrial, and biomedical applications.
Modeling of laser light scattering in a medium with spherical particles
Larionova, Nadezhda L.; Maksimova, Irina L.
2001-05-01
Laser light radiation scattered by the system of spheres with various parameters was theoretically investigated by using of the Mie theory of electromagnetic scattering by a single sphere. The calculations were performed for systems of particles whose coordinates were specifically realized in random fashion according to the specified probabilities defined by the approximation of hard spheres. The parameters of model are the same as in the eye lense biotissue and were carried out by using of medical data about internal structure of men lens and some animals. In general the studied model presents the system of homogeneous spherical particles which are randomly distributed in the layer of thickness. We study the optical properties such as scattering effective cross-section and function of correlation in different models.
Intricate Plasma-Scattered Images and Spectra of Focused Femtosecond Laser Pulses
Ooi, C. H. Raymond; Talib, Md. Ridzuan
2016-08-01
We report on some interesting phenomena in the focusing and scattering of femtosecond laser pulses in free space that provide insights on intense laser plasma interactions. The scattered image in the far field is analyzed and the connection with the observed structure of the plasma at the focus is discussed. We explain the physical mechanisms behind the changes in the colorful and intricate image formed by scattering from the plasma for different compressions, as well as orientations of plano-convex lens. The laser power does not show significant effect on the images. The pulse repetition rate above 500 Hz can affect the image through slow dynamics The spectrum of each color in the image shows oscillatory peaks due to interference of delayed pulse that correlate with the plasma length. Spectral lines of atomic species are identified and new peaks are observed through the white light emitted by the plasma spot. We find that an Ar gas jet can brighten the white light of the plasma spot and produce high resolution spectral peaks. The intricate image is found to be extremely sensitive and this is useful for applications in sensing microscale objects.
Gupta, D. N.; Yadav, Pinki; Jang, D. G.; Hur, M. S.; Suk, H.; Avinash, K.
2015-05-01
Stimulated Raman scattering of a laser in plasmas with energetic drifting electrons was investigated by analyzing the growth of interacting waves during the Raman scattering process. The Langmuir wave and scattered electromagnetic sideband wave grow initially and are dampened after attaining a maximum level that indicates a periodic exchange of energy between the pump wave and the daughter waves. The presence of energetic drifting electrons in the laser-produced plasma influences the stimulated Raman scattering process. The plasma wave generated by Raman scattering may be influenced by the energetic electrons, which enhance the growth rate of the instability. Our results show that the presence of energetic (hot) drifting electrons in a plasma has an important effect on the evolution of the interacting waves. This phenomenon is modeled via two-dimensional particle-in-cell simulations of the propagation and interaction of the laser under Raman instability.
Development of new methods for studying nanostructures using neutron scattering
Energy Technology Data Exchange (ETDEWEB)
Pynn, Roger [Indiana Univ., Bloomington, IN (United States)
2016-03-18
The goal of this project was to develop improved instrumentation for studying the microscopic structures of materials using neutron scattering. Neutron scattering has a number of advantages for studying material structure but suffers from the well-known disadvantage that neutrons’ ability to resolve structural details is usually limited by the strength of available neutron sources. We aimed to overcome this disadvantage using a new experimental technique, called Spin Echo Scattering Angle Encoding (SESAME) that makes use of the neutron’s magnetism. Our goal was to show that this innovation will allow the country to make better use of the significant investment it has recently made in a new neutron source at Oak Ridge National Laboratory (ORNL) and will lead to increases in scientific knowledge that contribute to the Nation’s technological infrastructure and ability to develop advanced materials and technologies. We were successful in demonstrating the technical effectiveness of the new method and established a baseline of knowledge that has allowed ORNL to start a project to implement the method on one of its neutron beam lines.
A Quantitative Vainberg Method for Black Box Scattering
Galkowski, Jeffrey
2017-01-01
We give a quantitative version of Vainberg's method relating pole free regions to propagation of singularities for black box scatterers. In particular, we show that there is a logarithmic resonance free region near the real axis of size {τ} with polynomial bounds on the resolvent if and only if the wave propagator gains derivatives at rate {τ}. Next we show that if there exist singularities in the wave trace at times tending to infinity which smooth at rate {τ}, then there are resonances in logarithmic strips whose width is given by {τ}. As our main application of these results, we give sharp bounds on the size of resonance free regions in scattering on geometrically nontrapping manifolds with conic points. Moreover, these bounds are generically optimal on exteriors of nontrapping polygonal domains.
Lower hybrid wave resonance cone detection via CO/sub 2/ laser scattering
Energy Technology Data Exchange (ETDEWEB)
Wurden, G.A.; Wong, K.L.; Ono, M.
1984-04-01
Lower hybrid waves are studied in the Princeton ACT-I steady-state toroidal plasma device using a radially scanning CO/sub 2/ laser scattering system with both amplitude and phase sensitive detection techniques. Clearly defined resonance cones launched from external electrostatic antennas are seen to disappear as the plasma density is raised. Scaling of LHW laser signal with RF power in the presence of resonance cones shows nonlinearities associated with RF induced changes in the effective laser scattering volume. Absolute fluctuation level estimates suggest this occurs when e PHI/T/sub e/ greater than or equal to 1. Wavefront curvature effects can cause a complete loss of resonance cone laser signals, even though probes indicate that cones are still present. Measurements of the wave k/sub perpendicular/-spectrum in the plasma show direct evidence for electron Landau filtering of the original wave k/sub parallel/-spectrum launched from the antenna at the plasma edge, and strong dependence on antenna phasing. Finally, frequency shifts and loss of the resonance cone signal are associated with high levels of plasma density edge turbulence.
Zijlstra, Peter; Chon, James W M; Gu, Min
2009-07-28
We present the first measurements of laser induced melting and reshaping of single gold nanorods. Using a combination of white light scattering spectroscopy and electron microscopy we find a melting energy of 260 fJ for nanorods with an average size of 92 x 30 nm. Contrary to previous reports on ensembles of nanorods, this melting energy corresponds well to the theoretical prediction of 225 fJ. We observe a gradual shape change from a long and thin rod to a shorter and wider rod, which eventually collapses into a sphere when enough laser energy is deposited. We also observe that higher aspect ratio particles are thermodynamically less stable, leading to a greater reduction of the aspect ratio at lower laser pulse energy densities.
Laser Thomson scattering diagnostics of non-equilibrium high pressure plasmas
Energy Technology Data Exchange (ETDEWEB)
Muraoka, K.; Uchino, K.; Bowden, M.D.; Noguchi, Y. [Kyushu Univ., Fukuoka (Japan). Interdisciplinary Graduate School of Engineering Sciences
2001-07-01
For various applications of non-equilibrium high pressure plasmas, knowledge of electron properties, such as electron density, electron temperature and/or electron energy distribution function (eedf), is prerequisite for any rational approach to understanding physical and chemical processes occurring in the plasmas. For this purpose, laser Thomson scattering has been successfully applied for the first time to measure the electron properties in plasmas for excimer laser pumping and in microdischarges. Although this diagnostic technique is well established for measurements in high temperature plasmas, its applications to these glow discharge plasmas have had various inherent difficulties, such as a presence of high density neutral particles (>10{sup 21} m{sup -3}) in the excimer laser pumping discharges and an extremely small plasma size (<0.1 mm) and the presence of nearby walls for microdischarges. These difficulties have been overcome and clear signals have been obtained. The measured results are presented and their implications in the respective discharge phenomena are discussed.
Institute of Scientific and Technical Information of China (English)
Gao Fei; Yamada Ryoko; Watanabe Mitsuo; Liu Hua-Feng
2009-01-01
Hamamatsu SHR74000 is a newly designed full three-dimensional(3D)whole body positron emission tomography (PET)scanner with small crystal size and large field of view(FOV).With the improvement of sensitivity,the scatter events increase significantly at the same time,especially for large objects.Monte Carlo simulations help US to understand the scatter phenomena and provide good references for scatter correction.In this paper,we introduce an effective scatter correction method based on single scatter simulation for the new PET scanner,which accounts for the full 3D scatter correction.With the results from Monte Carlo simulations,we implement a new scale method with special concentration on scatter events from outside the axial FOV and multiple scatter events.The effects of scatter correction are investigated and evaluated by phantom experiments;the results show good improvements in quantitative accuracy and contrast of the images,even for large objects.
Energy Technology Data Exchange (ETDEWEB)
Cvejić, M., E-mail: marko.cvejic@ipb.ac.rs, E-mail: krzysztof.dzierzega@uj.edu.pl [Institute of Physics, University of Belgrade, P.O. Box 68, 11080 Belgrade (Serbia); Faculty of Physics, Weizmann Institute of Science, Rehovot 7610001 (Israel); Dzierżęga, K., E-mail: marko.cvejic@ipb.ac.rs, E-mail: krzysztof.dzierzega@uj.edu.pl; Pięta, T. [M. Smoluchowski Institute of Physics, Jagellonian University, ul. Łojasiewicza 11, 30-348 Kraków (Poland)
2015-07-13
We have studied isothermal equilibrium in the laser-induced plasma from aluminum pellets in argon at pressure of 200 mbar by using a method which combines the standard laser Thomson scattering and analysis of the H{sub α}, Stark-broadened, line profiles. Plasma was created using 4.5 ns, 4 mJ pulses from a Nd:YAG laser at 1064 nm. While electron density and temperature were determined from the electron feature of Thomson scattering spectra, the heavy particle temperature was obtained from the H{sub α} full profile applying computer simulation including ion-dynamical effects. We have found strong imbalance between these two temperatures during entire plasma evolution which indicates its non-isothermal character. At the same time, according to the McWhirter criterion, the electron density was high enough to establish plasma in local thermodynamic equilibrium.
A finite difference method of solving anisotropic scattering problems
Barkstrom, B. R.
1976-01-01
A new method of solving radiative transfer problems is described including a comparison of its speed with that of the doubling method, and a discussion of its accuracy and suitability for computations involving variable optical properties. The method uses a discretization in angle to produce a coupled set of first-order differential equations which are integrated between discrete depth points to produce a set of recursion relations for symmetric and anti-symmetric angular sums of the radiation field at alternate depth points. The formulation given here includes depth-dependent anisotropic scattering, absorption, and internal sources, and allows arbitrary combinations of specular and non-Lambertian diffuse reflection at either or both boundaries. Numerical tests of the method show that it can return accurate emergent intensities even for large optical depths. The method is also shown to conserve flux to machine accuracy in conservative atmospheres
An effective method for incoherent scattering radar's detecting ability evaluation
Lu, Ziqing; Yao, Ming; Deng, Xiaohua
2016-06-01
Ionospheric incoherent scatter radar (ISR), which is used to detect ionospheric electrons and ions, generally, has megawatt class transmission power and hundred meter level antenna aperture. The crucial purpose of this detecting technology is to get ionospheric parameters by acquiring the autocorrelation function and power spectrum of the target ionospheric plasma echoes. Whereas the ISR's echoes are very weak because of the small radar cross section of its target, estimating detecting ability will be significantly instructive and meaningful for ISR system design. In this paper, we evaluate the detecting ability through signal-to-noise ratio (SNR). The soft-target radar equation is deduced to be applicable to ISR, through which we use data from International Reference Ionosphere model to simulate signal-to-noise ratio (SNR) of echoes, and then comparing the measured SNR from European Incoherent Scatter Scientific Association and Advanced Modular Incoherent Scatter Radar with the simulation. The simulation results show good consistency with the measured SNR. For ISR, the topic of this paper is the first comparison between the calculated SNR and radar measurements; the detecting ability can be improved through increasing SNR. The effective method for ISR's detecting ability evaluation provides basis for design of radar system.
New method of beam bunching in free-ion lasers
Energy Technology Data Exchange (ETDEWEB)
Bessonov, E.G. [Lebedev Physics Institute, Moscow (Russian Federation)
1995-12-31
An effective ion beam bunching method is suggested. This method is based on a selective interaction of line spectrum laser light (e.g. axial mode structure light) with non-fully stripped ion beam cooled in a storage rings, arranging the ion beam in layers in radial direction of an energy-longitudinal coordinate plane and following rotation of the beam at the right angle after switching on the RF cavity or undulator grouper/buncher. Laser cooling of the ion beam can be used at this position after switching off the resonator to decrease the energy spread caused by accelerating field of the resonator. A relativistic multilayer ion mirror will be produced this way. Both monochromatic laser beams and intermediate monochromaticity and bandwidth light sources of spontaneous incoherent radiation can be used for production of hard and high power electromagnetic radiation by reflection from this mirror. The reflectivity of the mirror is rather high because of the cross-section of the backward Rayleigh scattering of photon light by non-fully stripped relativistic ions ({approximately}{lambda}{sup 2}) is much greater ({approximately} 10{divided_by}15 orders) then Thompson one ({approximately} r{sub e}{sup 2}). This position is valid even in the case of non-monochromatic laser light ({Delta}{omega}/{omega} {approximately} 10{sup -4}). Ion cooling both in longitudinal plane and three-dimensional radiation ion cooling had been proposed based on this observation. The using of these cooling techniques will permit to store high current and low emittance relativistic ion beams in storage rings. The bunched ion beam can be used in ordinary Free-Ion Lasers as well. After bunching the ion beam can be extracted from the storage ring in this case. Storage rings with zero momentum compaction function will permit to keep bunching of the ion beam for a long time.
Greeley, A.; Kurtz, N. T.; Shappirio, M.; Neumann, T.; Cook, W. B.; Markus, T.
2014-12-01
Existing visible light laser altimeters such as ATM (Airborne Topographical Mapper) with NASA's Operation IceBridge and NASA's MABEL (Multiple Altimeter Beam Experimental Lidar; a simulator for NASA's ICESat-2 mission) are providing scientists with a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Measuring how these surfaces evolve in the face of a rapidly changing climate requires the utmost attention to detail in the design and calibration of these instruments, as well as understanding the changing optical properties of these surfaces. As single photon counting lidars, MABEL and NASA's ATLAS (Advanced Topographic Laser Altimeter System) on the upcoming ICESat-2 mission provide fundamentally different information compared with waveform lidars such as ATM, or GLAS (Geoscience Laser Altimeter System) on NASA's previous ICESat-1 mission. By recording the travel times of individual photons, more detailed information about the surface, and potentially the subsurface, are available and must be considered in elevation retrievals from the observed photon cloud. Here, we investigate possible sources of uncertainty associated with monochromatic visible light scattering in subsurface snow, which may affect the precision and accuracy of elevation estimates. We also explore the capacity to estimate snow grain size in near surface snow using experimental visible light laser data obtained in laboratory experiments.
Bond, Tiziana C.; Miles, Robin; Davidson, James C.; Liu, Gang Logan
2014-07-22
Methods for fabricating nanoscale array structures suitable for surface enhanced Raman scattering, structures thus obtained, and methods to characterize the nanoscale array structures suitable for surface enhanced Raman scattering. Nanoscale array structures may comprise nanotrees, nanorecesses and tapered nanopillars.
Energy Technology Data Exchange (ETDEWEB)
Bond, Tiziana C; Miles, Robin; Davidson, James; Liu, Gang Logan
2015-11-03
Methods for fabricating nanoscale array structures suitable for surface enhanced Raman scattering, structures thus obtained, and methods to characterize the nanoscale array structures suitable for surface enhanced Raman scattering. Nanoscale array structures may comprise nanotrees, nanorecesses and tapered nanopillars.
Bragg-Scattering Four-Wave Mixing in Nonlinear Fibers with Intracavity Frequency-Shifted Laser Pumps
Directory of Open Access Journals (Sweden)
Katarzyna Krupa
2012-01-01
Full Text Available We experimentally study four-wave mixing in highly nonlinear fibers using two independent and partially coherent laser pumps and a third coherent signal. We focus our attention on the Bragg-scattering frequency conversion. The two pumps were obtained by amplifying two Intracavity frequency-shifted feedback lasers working in a continuous wave regime.
Method for using polarization gating to measure a scattering sample
Energy Technology Data Exchange (ETDEWEB)
Baba, Justin S.
2015-08-04
Described herein are systems, devices, and methods facilitating optical characterization of scattering samples. A polarized optical beam can be directed to pass through a sample to be tested. The optical beam exiting the sample can then be analyzed to determine its degree of polarization, from which other properties of the sample can be determined. In some cases, an apparatus can include a source of an optical beam, an input polarizer, a sample, an output polarizer, and a photodetector. In some cases, a signal from a photodetector can be processed through attenuation, variable offset, and variable gain.
Kannaiyan, Kamalakannan; Banda, Manoj Venkata Krishna; Vaidyanathan, Aravind
2016-06-01
An experimental technique is carried out to demonstrate the measurement of planar Sauter Mean Diameter (SMD or D32) distribution in a liquid centered swirl coaxial injector (LCSC) using simultaneous measurements of Mie scattering, Planar Laser-Induced Fluorescence (PLIF) and Laser diffraction technique (LDT). Here water is used as the test fluid with addition of optimized quantities of the organic dye (Rhodamine 6 g) for PLIF measurements. Experiments are carried out at three experimental conditions with momentum flux ratios of 6.25, 12.14, and 19.95 respectively. Experiments are carried out to study the effect of dye concentration in LDT. LDT (line of sight) is corrected for multiple scattering effects. The SMD distribution obtained from Liquid Sheet Drop Sizing (LSDS) technique is calibrated using LDT (Malvern particle analyzer) that utilizes the principle of diffraction; the results obtained from both the methods are compared and analyzed using the respective histograms. The variations in the distribution of droplet diameter along the axial and radial locations in the spray field are also studied in detail.
Robust scatter correction method for cone-beam CT using an interlacing-slit plate
Huang, Kuidong; Zhang, Dinghua; Zhang, Hua; Shi, Wenlong
2015-01-01
Cone-beam computed tomography (CBCT) has been widely used in medical imaging and industrial nondestructive testing, but the presence of scattered radiation will cause significant reduction of image quality. In this article, a robust scatter correction method for CBCT using an interlacing-slit plate (ISP) is carried out for convenient practice. Firstly, a Gaussian filtering method is proposed to compensate the missing data of the inner scatter image, and simultaneously avoid too-large values of calculated inner scatter and smooth the inner scatter field. Secondly, an interlacing-slit scan without detector gain correction is carried out to enhance the practicality and convenience of the scatter correction method. Finally, a denoising step for scatter-corrected projection images is added in the process flow to control the noise amplification. The experimental results show that the improved method can not only make the scatter correction more robust and convenient, but also achieve a good quality of scatter-corre...
Near specular scatter analysis method with a new goniophotometer
Meyen, Stephanie; Sutter, Florian; Heller, Peter
2014-09-01
The challenge of improving component quality and reducing cost has focused the attention of the solar thermal power industry on reliable component characterization methods. Since the reflector plays a key role in the energy conversion chain, the analysis of its reflectance properties has become a lively discussed issue in recent years. State of the art measurement instruments for specular reflectance do not give satisfying results, because they do not resolve sufficiently the near specular scatter of possible low cost mirror material candidates. The measurement of the BRDF offers a better solution than the traditional approach of placing a detector in the specular reflected beam path. However, due to the requirement of high angular resolution in the range of 1 mrad (0.057°) or better and the challenge of measuring high dynamic differences between the specular peak and the scatter signal, typical commercial scanning goniophotometers capable of this are rare. These instruments also face the disadvantages of impractically long acquisition times and, to reach the high angular resolution, occupy a large space (several meters side length). We have taken on the appealing idea of a parallel imaging goniophotometer and designed a prototype based on this principle. A mirrored ellipsoid is used to redirect the reflected light coming from a sample towards a camera with a fisheye lens. This way the complete light distribution is captured simultaneously. A key feature allows the distinction of the high intensity specular peak and the low intensity scatter. In this article we explain the prototype design and demonstrate its functionality based on comparison measurements done with a commercial scanning goniophotometer. We identify limitations related in part to the concept and in part to the specific prototype and suggest improvements. Finally we conclude that the concept is well suitable for the analysis of near specular scatter of mirror materials, although less adequate for
ULTRA-BRIGHT X-RAY GENERATION USING INVERSE COMPTON SCATTERING OF PICOSECOND CO(2) LASER PLUSES.
Energy Technology Data Exchange (ETDEWEB)
TSUNEMI,A.; ENDO,A.; POGORELSKY,I.; BEN-ZVI,I.; KUSCHE,K.; SKARITKA,J.; YAKIMENKO,V.; HIROSE,T.; URAKAWA,J.; OMORI,T.; WASHIO,M.; LIU,Y.; HE,P.; CLINE,D.
1999-03-01
Laser-Compton scattering with picosecond CO{sub 2} laser pulses is proposed for generation of high-brightness x-rays. The interaction chamber has been developed and the experiment is scheduled for the generation of the x-rays of 4.7 keV, 10{sup 7} photons in 10-ps pulse width using 50-MeV, 0.5-nC relativistic electron bunches and 6 GW CO{sub 2} laser.
Laser Plasma Instability (LPI) Driven Light Scattering Measurements with Nike KrF Laser
Oh, J.; Weaver, J. L.; Kehne, D. M.; Obenschain, S. P.; McLean, E. A.; Lehmberg, R. H.
2008-11-01
With the short wavelength (248 nm), large bandwidth (1˜2 THz), and ISI beam smoothing, Nike KrF laser is expected to have higher LPI thresholds than observed at other laser facilities. Previous measurements using the Nike laser [J. L. Weaver et al, Phys. Plasmas 14, 056316 (2007)] showed no LPI evidence from CH targets up to I˜2x10^15 W/cm^2. For further experiments to detect LPI excitation, Nike capabilities have been extended to achieve higher laser intensities by tighter beam focusing and higher power pulses. This talk will present results of a recent LPI experiment with the extended Nike capabilities focusing on light emission data in spectral ranges relevant to the Raman (SRS) and Two-Plasmon Decay (TPD) instabilities. The primary diagnostics were time-resolved spectrometers with an absolute-intensity-calibrated photodiode array in (0.4˜0.8)φ0 and a streak camera near 0.5φ0. The measurements were conducted at laser intensities of 10^15˜10^16 W/cm^2 on planar targets of CH solids and RF foams.
Influence of the intensity gradient upon HHG from free electrons scattered by an intense laser beam
Li, Ankang; Ren, Na; Wang, Pingxiao; Zhu, Wenjun; Li, Xiaoya; Hoehn, Ross; Kais, Sabre
2013-01-01
When an electron is scattered by a tightly-focused laser beam in vacuum, the intensity gradient is a critical factor to influence the electron dynamics, for example, the electron energy exchange with the laser fields as have been explored before [P.X.Wang et al.,J. Appl. Phys. 91, 856 (2002]. In this paper, we have further investigated its influence upon the electron high-harmonic generation (HHG) by treating the spacial gradient of the laser intensity as a ponderomotive potential. Based upon perturbative QED calculations, it has been found that the main effect of the intensity gradient is the broadening of the originally line HHG spectra. A one-to-one relationship can be built between the beam width and the corresponding line width. Hence this finding may provides us a promising way to measure the beam width of intense lasers in experiments. In addition, for a laser pulse, we have also studied the different influences from transverse and longitudinal intensity gradients upon HHG.
Shimizu, H.; Kobayasi, T.; Inaba, H.
1979-01-01
A method of remote measurement of the particle size and density distribution of water droplets was developed. In this method, the size of droplets is measured from the Mie scattering parameter which is defined as the total-to-backscattering ratio of the laser beam. The water density distribution is obtained by a combination of the Mie scattering parameter and the extinction coefficient of the laser beam. This method was examined experimentally for the mist generated by an ultrasonic mist generator and applied to clouds containing rain and snow. Compared with the conventional sampling method, the present method has advantages of remote measurement capability and improvement in accuracy.
The FN method for anisotropic scattering in neutron transport theory: the critical slab problem.
Gülecyüz, M. C.; Tezcan, C.
1996-08-01
The FN method which has been applied to many physical problems for isotropic and anisotropic scattering in neutron transport theory is extended for problems for extremely anisotropic scattering. This method depends on the Placzek lemma and the use of the infinite medium Green's function. Here the Green's function for extremely anisotropic scattering which was expressed as a combination of the Green's functions for isotropic scattering is used to solve the critical slab problem. It is shown that the criticality condition is in agreement with the one obtained previously by reducing the transport equation for anisotropic scattering to isotropic scattering and solving using the FN method.
The structure of alkali silicate gel by total scattering methods
Benmore, C.J.
2010-06-01
The structure of the alkali silicate gel (ASR) collected from the galleries of Furnas Dam in Brazil was determined by a pair distribution function (PDF) analysis of high energy X-ray diffraction data. Since this method is relatively new to concrete structure analysis a detailed introduction on the PDF method is given for glassy SiO2. The bulk amorphous structure of the dam material is confirmed as no Bragg peaks are observed in the scattered intensity. The real space results show that the local structure of the amorphous material is similar to kanemite (KHSi2O5:3H2O) however the long range layer structure of the crystal is broken up in the amorphous state, so that ordering only persists of the length scale of a few polyhedra. The silicate layer structure is a much more disordered than predicted by molecular dynamics models. The X-ray results are consistent with the molecular dynamics model of Kirkpatrick et al. (2005) [1] which predicts that most of the water resides in pores within the amorphous network rather than in layers. The total scattering data provide a rigorous basis against which other models may also be tested. © 2010.
Spatial structure and coherence properties of Brillouin scatter from CO2 laser-target interaction
Mitchel, G. R.; Grek, B.; Johnston, T. W.; Pépin, H.; Church, P.; Martin, F.
1982-05-01
The spatial structure and coherence properties of 10.6-μm light scattered from CO2 laser-target interactions in oblique incidence show many unexpected features. It is found that the Brillouin backscatter is neither a phase conjugate nor a ray retrace of the incident beam. Rather, it shows a preference for scattering directions other than those exactly antiparallel to the incident beam, apparently related to the angular distribution of the scattering source and also of the plasma corona that serves as the Brillouin amplifying medium. As well, the backscatter phasefront is strongly perturbed with respect to the incident phasefront. This is an indication of turbulence in the corona and/or memory of the structure in the source that is then amplified. Small-scale structures seen in the reimaged backscatter are due to phase perturbation and cannot be simply interpreted as geometric images of a (filamented) source. The phasefront of light that is scattered obliquely from the plasma is much more coherent.
Stimulated Raman Scattering and Nonlinear Focusing of High-Power Laser Beams Propagating in Water
Hafizi, B; Penano, J R; Gordon, D F; Jones, T G; Helle, M H; Kaganovich, D
2015-01-01
The physical processes associated with propagation of a high-power (power > critical power for self-focusing) laser beam in water include nonlinear focusing, stimulated Raman scattering (SRS), optical breakdown and plasma formation. The interplay between nonlinear focusing and SRS is analyzed for cases where a significant portion of the pump power is channeled into the Stokes wave. Propagation simulations and an analytical model demonstrate that the Stokes wave can re-focus the pump wave after the power in the latter falls below the critical power. It is shown that this novel focusing mechanism is distinct from cross-phase focusing. While discussed here in the context of propagation in water, the gain-focusing phenomenon is general to any medium supporting nonlinear focusing and stimulated forward Raman scattering.
Indian Academy of Sciences (India)
M Sivanantham; B V R Tata
2010-12-01
Polyacrylamide (PAAm) hydrogels immersed in water and aqueous NaCl solutions were investigated for their structure and dynamics using static and quasi-elastic laser light scattering (QELS) techniques. Ensemble-averaged electric field correlation function (, ) obtained from the non-ergodic analysis of intensity-autocorrelation function for PAAm gel immersed in water and in 5 M NaCl showed an exponential decay to a plateau with an initial decay followed by saturation at long times. The value of the plateau was found to depend on NaCl concentration and was higher than that of water. Collective diffusion coefficient, , of the polymer network of the hydrogel immersed in water and in different concentrations of NaCl was determined by analysing (, ). The measured diffusion coefficient showed linear decrease with increase in concentration of NaCl. The characteristic network parameters were obtained by analyzing (, ) with harmonically bound Brownian particle model and from static light scattering studies.
Stimulated Brillouin scattering of laser in semiconductor plasma embedded with nano-sized grains
Energy Technology Data Exchange (ETDEWEB)
Sharma, Giriraj, E-mail: grsharma@gmail.com [SRJ Government Girls’ College, Neemuch (M P) (India); Dad, R. C. [Government P G College, Mandsaur (M P) (India); Ghosh, S. [School of Studies in Physics, Vikram University, Ujjain, (M P) (India)
2015-07-31
A high power laser propagating through semiconductor plasma undergoes Stimulated Brillouin scattering (SBS) from the electrostrictively generated acoustic perturbations. We have considered that nano-sized grains (NSGs) ions are embedded in semiconductor plasma by means of ion implantation. The NSGs are bombarded by the surrounding plasma particles and collect electrons. By considering a negative charge on the NSGs, we present an analytically study on the effects of NSGs on threshold field for the onset of SBS and Brillouin gain of generated Brillouin scattered mode. It is found that as the charge on the NSGs builds up, the Brillouin gain is significantly raised and the threshold pump field for the onset of SBS process is lowered.
Generation of 9 MeV γ-rays by all-laser-driven Compton scattering with second-harmonic laser light.
Liu, Cheng; Golovin, Grigory; Chen, Shouyuan; Zhang, Jun; Zhao, Baozhen; Haden, Daniel; Banerjee, Sudeep; Silano, Jack; Karwowski, Hugon; Umstadter, Donald
2014-07-15
Gamma-ray photons with energy >9 MeV were produced when second-harmonic-generated laser light (3 eV) inverse-Compton-scattered from a counterpropagating relativistic (~450 MeV) laser-wakefield-accelerated electron beam. Two laser pulses from the same laser system were used: one to accelerate electrons and one to scatter. Since the two pulses play very different roles in the γ-ray generation process, and thus have different requirements, a novel laser system was developed. It separately and independently optimized the optical properties of the two pulses. This approach also mitigated the deleterious effects on beam focusing that generally accompany nonlinear optics at high peak-power levels.
Scanning coherent scattering methods for actinic EUV mask inspection
Ekinci, Y.; Helfenstein, P.; Rajeev, R.; Mochi, I.; Mohacsi, I.; Gobrecht, J.; Yoshitake, S.
2016-10-01
Actinic mask inspection for EUV lithography with targeted specifications of resolution, sensitivity, and throughput remains a big hurdle for the successful insertion of EUVL into high volume manufacturing and effective solutions are needed to address this. We present a method for actinic mask inspection based on scanning coherent scattering microscopy. In this method, the mask is scanned with an EUV beam of relatively small spot size and the scattered light is recorded with a pixel detector. Customized algorithms reconstruct the aerial image by iteratively solving the phaseproblem using over-determined diffraction data gathered by scanning across the specimen with a finite illumination. This approach provides both phase and amplitude of actinic aerial images of the mask with high resolution without the need to use high NA (numerical aperture) lenses. Futher, we describe a reflective mode EUV mask scanning lensless imaging tool (RESCAN), which was installed at the XIL-II beamline and later at the SIM beamline of the Swiss Light Source and show reconstructed aerial images down to 10 nm (on-wafer) resolution. As a complementary method, the a-priori knowledge of the sample is employed to identify potential defect sites by analyzing the diffraction patterns. In this method, the recorded diffraction patterns are compared with the die or database data (i.e. previously measured or calculated diffraction data from the defect-free mask layout respectively) and their difference is interpreted as the defect signal. Dynamic software filtering helps to suppress the strong diffraction from defect-free structures and allows registration of faint defects with high sensitivity. Here, we discuss the basic principles of these Fourier domain techniques and its potential for actinic mask inspection with high signal-to-noise ratio and high throughput.
[Evaluation of molecular weights of hyaluronate preparations by multi-angle laser light scattering].
Yomota, Chikako
2003-01-01
Hyaluronate (HA), a glycosaminoglycan polysaccharide, has been used for osteoarthritis, periartritis of the shoulder and rheumatoid arthritis by intraarticular administration, and in ophthalmic surgery such as anterior segment surgery, and eye lotion. In this study, the molecular weight (Mw) of HA preparations were estimated by size-exclusion chromatography (SEC) system consisted of a refractometer (RI) and a multi-angle laser light scattering (MALS). From the results, it has been clarified that a successful characterization of HA samples with Mw up to 2 - 3 x 10(6) g/mol was possible by multidetector system.
Thomson scattering measurement of a shock in laser-produced counter-streaming plasmas
Energy Technology Data Exchange (ETDEWEB)
Morita, T.; Kuramitsu, Y.; Moritaka, T. [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Sakawa, Y.; Takabe, H. [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Graduate School of Science, Osaka University, 1-1 Machikane-yama, Toyonaka, Osaka 560-0043 (Japan); Tomita, K.; Nakayama, K.; Inoue, K.; Uchino, K. [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1, Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Ide, T.; Tsubouchi, K. [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Nishio, K.; Ide, H.; Kuwada, M. [Graduate School of Science, Osaka University, 1-1 Machikane-yama, Toyonaka, Osaka 560-0043 (Japan)
2013-09-15
We report the first direct measurement of temporally and spatially resolved plasma temperatures at a shock as well as its spatial structure and propagation in laser-produced counter-streaming plasmas. Two shocks are formed in counter-streaming collisionless plasmas early in time, and they propagate opposite directions. This indicates the existence of counter-streaming collisionless flows to keep exciting the shocks, even though the collisional effects increase later in time. The shock images are observed with optical diagnostics, and the upstream and downstream plasma parameters of one of the shocks are measured using Thomson scattering technique.
Michel, Sébastien; Courjaud, Antoine; Mottay, Eric; Finot, Christophe; Dudley, John; Rigneault, Hervé
2011-02-01
We perform multiplex coherent anti-Stokes Raman scattering (CARS) micro-spectroscopy with a picosecond pulsed laser and a broadband supercontinuum (SC) generated in photonic crystal fiber. CARS signal stability is achieved using an active fiber coupler that avoids thermal and mechanical drifts. We obtain multiplex CARS spectra for test liquids in the 600-2000 cm(-1) spectral range. In addition we investigate the polarization dependence of the CARS spectra when rotating the pump beam linear polarization state relative to the linearly polarized broad stokes SC. From these polarization measurements we deduce the Raman depolarization ratio, the resonant versus nonresonant contribution, the Raman resonance frequency, and the linewidth.
Ramírez-García, Gonzalo; d'Orlyé, Fanny; Gutiérrez-Granados, Silvia; Martínez-Alfaro, Minerva; Mignet, Nathalie; Richard, Cyrille; Varenne, Anne
2015-12-01
Zinc gallate nanoparticles doped with chromium (III) (ZnGa1.995O4:Cr0.005) are innovative persistent luminescence materials with particular optical properties allowing their use for in vivo imaging. They can be excited in the tissue transparency window by visible photons and emit light for hours after the end of the excitation. This allows to observe the probe without any time constraints and without autofluorescence signals produced by biological tissues. Modification of the surface of these nanoparticles is essential to be colloidally stable not only for cell targeting applications but also for proper distribution in living organisms. The use of different methods for controlling and characterizing the functionalization process is imperative to better understand the subsequent interactions with biological elements. This work explores for the first time the characterization and optimization of a classic functionalization sequence, starting with hydroxyl groups (ZGO-OH) at the nanoparticle surface, followed by an aminosilane-functionalization intermediate stage (ZGO-NH2) before PEGylation (ZGO-PEG). Dynamic light scattering and laser doppler electrophoresis were used in combination with capillary electrophoresis to characterize the nanoparticle functionalization processes and control their colloidal and chemical stability. The hydrodynamic diameter, zeta potential, electrophoretic mobility, stability over time and aggregation state of persistent luminescence nanoparticles under physiological-based solution conditions have been studied for each functional state. Additionally, a new protocol to improve ZGO-NH2 stability based on a thermal treatment to complete covalent binding of (3-aminopropyl) triethoxysilane onto the particle surface has been optimized. This thorough control increases our knowledge on these nanoparticles for subsequent toxicological studies and ultimately medical application.
Hajjarian, Zeinab; Nadkarni, Seemantini K.
2013-01-01
Biological fluids fulfill key functionalities such as hydrating, protecting, and nourishing cells and tissues in various organ systems. They are capable of these versatile tasks owing to their distinct structural and viscoelastic properties. Characterizing the viscoelastic properties of bio-fluids is of pivotal importance for monitoring the development of certain pathologies as well as engineering synthetic replacements. Laser Speckle Rheology (LSR) is a novel optical technology that enables mechanical evaluation of tissue. In LSR, a coherent laser beam illuminates the tissue and temporal speckle intensity fluctuations are analyzed to evaluate mechanical properties. The rate of temporal speckle fluctuations is, however, influenced by both optical and mechanical properties of tissue. Therefore, in this paper, we develop and validate an approach to estimate and compensate for the contributions of light scattering to speckle dynamics and demonstrate the capability of LSR for the accurate extraction of viscoelastic moduli in phantom samples and biological fluids of varying optical and mechanical properties. PMID:23705028
Bryukvina, L. I.; Pestryakov, E. V.; Kirpichnikov, A. V.; Martynovich, E. F.
2014-11-01
Modification of sodium fluoride crystal lattice by means of femtosecond laser pulses with λmax=800 nm, energy 0.5 mJ, duration 30 fs and repetition rate 1 kHz has been considered in the paper. Effective formation of simple and complex aggregate color centers and light scattering nanodefects in the channel of a laser beam in NaF crystal have been shown for the first time. Dependences of color centers concentration on the distance between the channel center and its periphery and along the channel have been presented. Influence of external focusing on color centers creation has been revealed. Explanations of the observed phenomena have been presented on the basis of nonlinear processes taking place under the effect of high-intensity femtosecond pulses.
Development of Thomson scattering system on Shenguang-III prototype laser facility
Energy Technology Data Exchange (ETDEWEB)
Gong, Tao [CAS Key Laboratory of Geospace Environment and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Li, Zhichao; Jiang, Xiaohua; Ding, Yongkun, E-mail: ding-yk@vip.sina.com; Yang, Dong; Wang, Zhebin; Wang, Fang; Li, Ping; Liu, Shenye; Jiang, Shaoen [Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang, Sichuan 621900 (China); Hu, Guangyue; Zhao, Bin [CAS Key Laboratory of Geospace Environment and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Zheng, Jian, E-mail: jzheng@ustc.edu.cn [CAS Key Laboratory of Geospace Environment and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240 (China)
2015-02-15
A Thomson scattering diagnostic system, using a 263 nm laser as the probe beam, is designed and implemented on Shenguang-III prototype laser facility. The probe beam is provided by an additional beam line completed recently. The diagnostic system allows simultaneous measurements of both ion feature and red-shifted electron feature from plasmas in a high-temperature (≥2 keV) and high-density (≥10{sup 21} cm{sup −3}) regime. Delicate design is made to satisfy the requirements for successful detection of the electron feature. High-quality ion feature spectra have already been diagnosed via this system in recent experiments with gas-filled hohlraums.
Delivery of picosecond lasers in multimode fibers for coherent anti-Stokes Raman scattering imaging.
Wang, Zhiyong; Yang, Yaliang; Luo, Pengfei; Gao, Liang; Wong, Kelvin K; Wong, Stephen T C
2010-06-07
We investigated the possibility of using standard commercial multimode fibers (MMF), Corning SMF28 fibers, to deliver picosecond excitation lasers for coherent anti-Stokes Raman scattering (CARS) imaging. We theoretically and/or experimentally analyzed issues associated with the fiber delivery, such as dispersion length, walk-off length, nonlinear length, average threshold power for self-phase modulations, and four-wave mixing (FWM). These analyses can also be applied to other types of fibers. We found that FWM signals are generated in MMF, but they can be filtered out using a long-pass filter for CARS imaging. Finally, we demonstrated that MMF can be used for delivery of picosecond excitation lasers in the CARS imaging system without any degradation of image quality.
Feasibility of Strong and Quasi-Monochromatic Gamma-Ray Generation by the Laser Compton Scattering
Energy Technology Data Exchange (ETDEWEB)
Lee, Jiyoung; Rehman, Haseeb ur; Kim, Yonghee [KAIST, Daejeon (Korea, Republic of)
2015-10-15
This is because LCS γ-rays are energy-tunable, quasi-monochromatic, and beam-like. The photon intensity of the mono-chromatic LCS gamma-ray should be high or strong for efficient and high transmutation rate. It was recently reported that a so-called energy-recovery linac system is able to produce a very high-intensity LCS photons in the order of approximately 1013 photons/s economically. It however did not evaluate quality of the LCS photon beam although a quasi-monoenergetic LCS beam is of huge importance in the photo-nuclear transmutation reactions. It is upon this observation that this paper was prepared. Specifically, this work attempts to quantify intensity of the quasi-monochromatic LCS beam from the said linac system. In addition, this paper aims to discuss general characteristics of the LCS photon, and possible approaches to increase its intensity. This paper presents essential characteristics of the laser Compton scattering (LCS) in terms of its photon energy, cross-section and photon intensity. By using different combinations of electron energy, laser energy and scattering angle, we can effectively generate high-intensity and highly-chromatic LCS gamma-rays. Our preliminary analyses indicate that, in view of Compton cross-section, higher-energy photon can be better generated by increasing the electron energy rather than increasing the laser energy. However, in order to maximize the intensity of monochromatic beam, the laser energy should be maximized for a targeted LCS photon energy.
Photovoltaic structures having a light scattering interface layer and methods of making the same
Energy Technology Data Exchange (ETDEWEB)
Liu, Xiangxin; Compaan, Alvin D.; Paudel, Naba Raj
2015-10-13
Photovoltaic (PV) cell structures having an integral light scattering interface layer configured to diffuse or scatter light prior to entering a semiconductor material and methods of making the same are described.
Underwater laser fabrication method and device
Energy Technology Data Exchange (ETDEWEB)
Okazaki, Yuki; Ito, Arata; Sano, Yuji; Mukai, Naruhiko; Aoki, Nobutada; Konagai, Chikara [Toshiba Corp., Kawasaki, Kanagawa (Japan); Kikunaga, Muneyoshi
1996-08-13
The present invention concerns an underwater laser fabrication method which comprises irradiating laser beams having a visible wavelength at high power and of short pulse to the surface of structural components immersed in coolants to improve residual stresses on the surface of the materials of the structural components and eliminate cracks or remove cruds. Laser beams having a visible wavelength and a pulse width of not greater than 100n sec are irradiated to the materials on the surface of inner structural components of a reactor under the conditions of a peak power of from 0.1 to 10GW/cm{sup 2} per 1 pulse, and overlapping ratio of irradiation beams of not less than 100%, to improve the residual stresses on the surface of the materials of the structural components and form them into compressed stresses. Then, the irradiation is conducted while monitoring the state to remove crackings by abrasion. Further, the stresses on the surface of the materials after removing crackings are improved. In the present invention, since the laser beams, namely, visible rays can be transmitted directly under water, the operation can be conducted directly in coolants. Therefore, it is not necessary to drain coolants in the reactor before the operation. Further, reduction in an operator`s radiation exposure can be expected. (T.M.)
Laser: a Tool for Optimization and Enhancement of Analytical Methods
Energy Technology Data Exchange (ETDEWEB)
Preisler, Jan [Iowa State Univ., Ames, IA (United States)
1997-01-01
In this work, we use lasers to enhance possibilities of laser desorption methods and to optimize coating procedure for capillary electrophoresis (CE). We use several different instrumental arrangements to characterize matrix-assisted laser desorption (MALD) at atmospheric pressure and in vacuum. In imaging mode, 488-nm argon-ion laser beam is deflected by two acousto-optic deflectors to scan plumes desorbed at atmospheric pressure via absorption. All absorbing species, including neutral molecules, are monitored. Interesting features, e.g. differences between the initial plume and subsequent plumes desorbed from the same spot, or the formation of two plumes from one laser shot are observed. Total plume absorbance can be correlated with the acoustic signal generated by the desorption event. A model equation for the plume velocity as a function of time is proposed. Alternatively, the use of a static laser beam for observation enables reliable determination of plume velocities even when they are very high. Static scattering detection reveals negative influence of particle spallation on MS signal. Ion formation during MALD was monitored using 193-nm light to photodissociate a portion of insulin ion plume. These results define the optimal conditions for desorbing analytes from matrices, as opposed to achieving a compromise between efficient desorption and efficient ionization as is practiced in mass spectrometry. In CE experiment, we examined changes in a poly(ethylene oxide) (PEO) coating by continuously monitoring the electroosmotic flow (EOF) in a fused-silica capillary during electrophoresis. An imaging CCD camera was used to follow the motion of a fluorescent neutral marker zone along the length of the capillary excited by 488-nm Ar-ion laser. The PEO coating was shown to reduce the velocity of EOF by more than an order of magnitude compared to a bare capillary at pH 7.0. The coating protocol was important, especially at an intermediate pH of 7.7. The increase of p
Laser: a Tool for Optimization and Enhancement of Analytical Methods
Energy Technology Data Exchange (ETDEWEB)
Preisler, Jan
1997-01-01
In this work, we use lasers to enhance possibilities of laser desorption methods and to optimize coating procedure for capillary electrophoresis (CE). We use several different instrumental arrangements to characterize matrix-assisted laser desorption (MALD) at atmospheric pressure and in vacuum. In imaging mode, 488-nm argon-ion laser beam is deflected by two acousto-optic deflectors to scan plumes desorbed at atmospheric pressure via absorption. All absorbing species, including neutral molecules, are monitored. Interesting features, e.g. differences between the initial plume and subsequent plumes desorbed from the same spot, or the formation of two plumes from one laser shot are observed. Total plume absorbance can be correlated with the acoustic signal generated by the desorption event. A model equation for the plume velocity as a function of time is proposed. Alternatively, the use of a static laser beam for observation enables reliable determination of plume velocities even when they are very high. Static scattering detection reveals negative influence of particle spallation on MS signal. Ion formation during MALD was monitored using 193-nm light to photodissociate a portion of insulin ion plume. These results define the optimal conditions for desorbing analytes from matrices, as opposed to achieving a compromise between efficient desorption and efficient ionization as is practiced in mass spectrometry. In CE experiment, we examined changes in a poly(ethylene oxide) (PEO) coating by continuously monitoring the electroosmotic flow (EOF) in a fused-silica capillary during electrophoresis. An imaging CCD camera was used to follow the motion of a fluorescent neutral marker zone along the length of the capillary excited by 488-nm Ar-ion laser. The PEO coating was shown to reduce the velocity of EOF by more than an order of magnitude compared to a bare capillary at pH 7.0. The coating protocol was important, especially at an intermediate pH of 7.7. The increase of p
The Quantum Inverse Scattering Method for Hubbard-like Models
Martins, M J
1997-01-01
This work is concerned with various aspects of the formulation of the quantum inverse scattering method for the one-dimensional Hubbard model. We first establish the essential tools to solve the eigenvalue problem for the transfer matrix of the classical ``covering'' Hubbard model within the algebraic Bethe Ansatz framework. The fundamental commutation rules exhibit a hidden 6-vertex symmetry which plays a crucial role in the whole algebraic construction. Next we apply this formalism to study the SU(2) highest weights properties of the eigenvectors and the solution of a related coupled spin model with twisted boundary conditions. The machinery developed in this paper is applicable to many other models, and as an example we present the algebraic solution of the Bariev XY coupled model.
Laser light scattering from silicon particles generated in an argon diluted silane plasma
Qin, Y.; Bilik, N.; Kortshagen, U. R.; Aydil, E. S.
2016-03-01
We conducted laser light scattering (LLS) measurements in a 13.56 MHz capacitively coupled dusty plasma maintained in silane and argon to study the spatial distribution of silicon nanoparticles and nanoparticle agglomerates. Specifically, we focused on the temporal evolution of their spatial distribution in the plasma as a function of pressure and power. We observed three distinct types of temporal evolution behavior of the nanoparticle dust cloud in the plasma and classified these into three regimes based on pressure and power. Each regime features a distinct pattern in laser light scattering measurements. At low pressures (˜80-100 mTorr) and high powers (˜40-60 W) we observed periodically repeating expansions and contractions of a continuous dust cloud for the first time. Dust voids, which have been reported before, were also observed at high pressures (˜100-150 mTorr) and low powers (˜20-40 W) in the center of the plasma. A mechanism is proposed to explain the observed dynamics of the nanoparticles. The balance between the ion drag force and electrostatic forces and their dependence on particle size are hypothesized to be the dominant factors that determine the nanoparticle cloud dynamics.
Reiss, N.; Schotland, R. M.
1973-01-01
A remote sensing technique is described which utilizes elastic scattering and rotational Raman scattering of laser light in the atmosphere to obtain soundings of turbidity, transmissivity and density. A scheme is devised whereby, through selective weighting of the rotational Raman lines, the effect of atmospheric temperature structure may be eliminated. The close spectral proximity of the elastic and Raman-scattered signals, combined with the fact that the Raman scattering is quite weak, produces special requirements for the spectroscopic and light-gathering components of a rotational Raman laser radar system. These requirements are investigated. A computation of typical signal-to-noise ratios is made. It is shown that daytime signal-to-noise ratios greater than 10 db are to be expected for observation heights of 5 km and below. For nighttime work, 10 db signal-to-noise ratios are achievable to altitudes as high as 15 km.
Combined effects of scattering and absorption on laser speckle contrast imaging
Khaksari, Kosar; Kirkpatrick, Sean J.
2016-07-01
Several variables may affect the local contrast values in laser speckle contrast imaging (LSCI), irrespective of relative motion. It has been suggested that the optical properties of the moving fluid and surrounding tissues can affect LSCI values. However, a detailed study of this has yet to be presented. In this work, we examined the combined effects of the reduced scattering and absorption coefficients on LSCI. This study employs fluid phantoms with different optical properties that were developed to mimic whole blood with varying hematocrit levels. These flow phantoms were imaged with an LSCI system developed for this study. The only variable parameter was the optical properties of the flowing fluid. A negative linear relationship was seen between the changes in contrast and changes in reduced scattering coefficient, absorption coefficient, and total attenuation coefficient. The change in contrast observed due to an increase in the scattering coefficient was greater than what was observed with an increase in the absorption coefficient. The results indicate that optical properties affect contrast values and that they should be considered in the interpretation of LSCI data.
Leavesley, Silas; Bayraktar, Bülent; Venkatapathi, Murugesan; Hirleman, E. Dan; Bhunia, Arun K.; Robinson, J. Paul; Hassler, Richard; Smith, Linda; Rajwa, Bartek
2007-02-01
Traditional biological and chemical methods for pathogen identification require complicated sample preparation for reliable results. Optical scattering technology has been used for identification of bacterial cells in suspension, but with only limited success. Our published reports have demonstrated that scattered light based identification of Listeria colonies growing on solid surfaces is feasible with proper pattern recognition tools. Recently we have extended this technique to classification of other bacterial genera including, Salmonella, Bacillus, and Vibrio. Our approach may be highly applicable to early detection and classification of pathogens in food-processing industry and in healthcare. The unique scattering patterns formed by colonies of different species are created through differences in colony microstructure (on the order of wavelength used), bulk optical properties, and the macroscopic morphology. While it is difficult to model the effect on scatter-signal patterns owing to the microstructural changes, the influence of bulk optical properties and overall shape of colonies can be modeled using geometrical optics. Our latest research shows that it is possible to model the scatter pattern of bacterial colonies using solid-element optical modeling software (TracePro), and theoretically assess changes in macro structure and bulk refractive indices. This study allows predicting the theoretical limits of resolution and sensitivity of our detection and classification methods. Moreover, quantification of changes in macro morphology and bulk refractive index provides an opportunity to study the response of colonies to various reagents and antibiotics.
Sun, Wenbo; Hu, Yongxiang; Weimer, Carl; Ayers, Kirk; Baize, Rosemary R.; Lee, Tsengdar
2017-02-01
Electromagnetic (EM) beams with orbital angular momentum (OAM) may have great potential applications in communication technology and in remote sensing of the Earth-atmosphere system and outer planets. Study of their interaction with optical lenses and dielectric or metallic objects, or scattering of them by particles in the Earth-atmosphere system, is a necessary step to explore the advantage of the OAM EM beams. In this study, the 3-dimensional (3D) scattered-field (SF) finite-difference time domain (FDTD) technique with the convolutional perfectly matched layer (CPML) absorbing boundary conditions (ABC) is applied to calculate the scattering of the purely azimuthal (the radial mode number is assumed to be zero) Laguerre-Gaussian (LG) beams with the OAM by dielectric particles. We found that for OAM beam's interaction with dielectric particles, the forward-scattering peak in the conventional phase function (P11) disappears, and light scattering peak occurs at a scattering angle of 15° to 45°. The disappearance of forward-scattering peak means that, in laser communications most of the particle-scattered noise cannot enter the receiver, thus the received light is optimally the original OAM-encoded signal. This feature of the OAM beam also implies that in lidar remote sensing of the atmospheric particulates, most of the multiple-scattering energy will be off lidar sensors, and this may result in an accurate profiling of particle layers in the atmosphere or in the oceans by lidar, or even in the ground when a ground penetration radar (GPR) with the OAM is applied. This far-field characteristics of the scattered OAM light also imply that the optical theorem, which is derived from plane-parallel wave scattering case and relates the forward scattering amplitude to the total cross section of the scatterer, is invalid for the scattering of OAM beams by dielectric particles.
A schlieren method for ultra-low angle light scattering measurements
Brogioli, D; Giglio, M; Giglio, Marzio
2003-01-01
We describe a self calibrating optical technique that allows to perform absolute measurements of scattering cross sections for the light scattered at extremely small angles. Very good performances are obtained by using a very simple optical layout similar to that used for the schlieren method, a technique traditionally used for mapping local refraction index changes. The scattered intensity distribution is recovered by a statistical analysis of the random interference of the light scattered in a half-plane of the scattering wave vectors and the main transmitted beam. High quality data can be obtained by proper statistical accumulation of scattered intensity frames, and the static stray light contributions can be eliminated rigorously. The potentialities of the method are tested in a scattering experiment from non equilibrium fluctuations during a free diffusion experiment. Contributions of light scattered from length scales as long as Lambda=1 mm can be accurately determined.
Li, Daojing; Li, Lei; Chen, Hao; Tang, Dingyuan; Zhao, Luming
2015-01-01
We report on the observation of both stable dissipative solitons and noise-like pulses with the presence of strong Raman scattering in a relatively short all-normal-dispersion Yb-doped fiber laser. We show that Raman scattering can be filtered out by intracavity filter. Furthermore, by appropriate intracavity polarization control, the Raman effect can be utilized to generate broadband noise-like pulses (NLPs) with bandwidth up to 61.4 nm. To the best of our knowledge, this is the broadest NLP achieved in all-normal-dispersion fiber lasers
Energy Technology Data Exchange (ETDEWEB)
Wu, Benny
2012-04-05
We report on time-resolved coherent x-ray scattering experiments of laser induced magnetization dynamics in Co/Pd multilayers with a high repetition rate optical pump x-ray probe setup. Starting from a multi-domain ground state, the magnetization is uniformly reduced after excitation by an intense 50 fs laser pulse. Using the normalized time correlation, we study the magnetization recovery on a picosecond timescale. The dynamic scattering intensity is separated into an elastic portion at length scales above 65 nm which retains memory of the initial domain magnetization, and a fluctuating portion at smaller length scales corresponding to domain boundary motion during recovery.
Zhang, C M
2007-01-01
The stationary phase point (SPP) method in one-dimensional case is introduced to treat the diffractive scintillation. From weak scattering, where the SPP number N=1, to strong scattering (N$\\gg$1), via transitional scattering regime (N$\\sim$2,3), we find that the modulation index of intensity experiences the monotonically increasing from 0 to 1 with the scattering strength, characterized by the ratio of Fresnel scale $\\rf$ to diffractive scale $\\rdiff$.
Modeling of electromagnetic scattering by thin cylinders using Pattern Equation Method
Demin, D. B.; Kleev, A. I.; Kyurkchan, A. G.
2017-01-01
To solve the problem related to scattering by a perfectly conducting thin cylinder, approximate approach was developed based on use of Pattern Equation Method (PEM). Explicit formulas were obtained for total scattering cross-section applicable for cylindric scatterers of complex shape. It is shown that calculation accuracy controlled by calculating the balance of power flows for incident and scattered waves (checking the accomplishment of optical theorem) is quite sufficient for practice.
Gamma-ray scatter methods applied to industrial measurement systems
Energy Technology Data Exchange (ETDEWEB)
Holstad, Marie Bueie
2004-09-01
Throughout the work presented in this dissertation it has been confirmed that the use of scattered gamma-radiation is a complex but useful tool in industrial measurement science. Scattered radiation has shown to be useful both when traditional measurement principles cannot be used (Chapter 4) and when more information about a system is needed than what is obtained with transmission measurements (Chapter 6). All three main projects (Chapters 4, 5 and 6) confirm that the sensitivity and accuracy of systems based on scattered gamma-radiation depends strongly on the geometry of the setup and that that presence of multiple scattered radiation makes the problems complex. Chapter 4 shows that multiple scattered gamma-radiation can be used for detection of changes in density where the dimensions are too large to use transmitted radiation. There is, however, an upper limit on the thickness of the absorbing medium also when scattered radiation is utilized. As seen in Chapter 5, multiple scattered gamma-radiation can in principle also be used in level gauges with very compact measurement geometries. The main challenges are the sensitivity to interfaces between materials with similar densities and low count rate. These challenges could not be overcome for level measurements in gravitational separator tanks. The results presented in Chapter 6 show that it is feasible to combine transmission and scatter measurements to characterize produced water in the oil and gas industry. (Author)
Thomson scattering system on the TEXTOR tokamak using a multi-pass laser beam configuration
Energy Technology Data Exchange (ETDEWEB)
Kantor, M Yu; Donne, A J H; Jaspers, R; Van der Meiden, H J [FOM-Institute for Plasma Physics Rijnhuizen , Association EURATOM-FOM, PO Box 1207, 3430 BE Nieuwegein (Netherlands)], E-mail: m.kantor@fz-juelich.de
2009-05-15
The main challenge for the Thomson scattering (TS) diagnostic on the TEXTOR tokamak is the detailed study of fast plasma events at a high spatial resolution and a high repetition rate of the measurements. The diagnostic uses intra-cavity probing of the plasma with a repetitively pulsed ruby laser and a fast CMOS camera as detectors. Since 2004, the TS system on TEXTOR has been gradually and systematically enhanced for the measurements of fast plasma events. For that it has recently been upgraded to obtain a multi-pass configuration. Two spherical mirrors have been installed that force the laser beam to probe the plasma a specified number of times before it is directed back into the laser medium. The diagnostics with the upgraded probing system have achieved the measurement accuracy of 3% for the electron temperature and 1.5% for the electron density at <1 cm spatial resolution and 3 x 10{sup 19} m{sup -3} plasma density and can measure at 5 kHz during an interval up to 8 ms. This makes it possible to detect, amongst others, fine structures of magnetic islands and variations of the edge pedestal in the ELMy limiter H-mode.
Thomson scattering system on the TEXTOR tokamak using a multi-pass laser beam configuration
Kantor, M Yu; Donné, A J H; Jaspers, R; van der Meiden, H J; TEXTOR Team
2009-05-01
The main challenge for the Thomson scattering (TS) diagnostic on the TEXTOR tokamak is the detailed study of fast plasma events at a high spatial resolution and a high repetition rate of the measurements. The diagnostic uses intra-cavity probing of the plasma with a repetitively pulsed ruby laser and a fast CMOS camera as detectors. Since 2004, the TS system on TEXTOR has been gradually and systematically enhanced for the measurements of fast plasma events. For that it has recently been upgraded to obtain a multi-pass configuration. Two spherical mirrors have been installed that force the laser beam to probe the plasma a specified number of times before it is directed back into the laser medium. The diagnostics with the upgraded probing system have achieved the measurement accuracy of 3% for the electron temperature and 1.5% for the electron density at <1 cm spatial resolution and 3 × 1019 m-3 plasma density and can measure at 5 kHz during an interval up to 8 ms. This makes it possible to detect, amongst others, fine structures of magnetic islands and variations of the edge pedestal in the ELMy limiter H-mode.
Development of the so-called third stage laser Thomson scattering diagnostics of plasmas
Muraoka, Katsunori; Yamagata, Yukihiko; Hisano, Taishi; Uchino, Kiichirou; Miyazaki, Koichi
2003-10-01
In the recent review article,^1) we indicated that the incoherent laser Thomson scattering (LTS) diagnostics of plasmas for measurements of electron densities and temperatures (or more generally EEDFs) be classified as having evolved from the first stage where a whole Thomson spectrum be obtained during a single laser pulse from plasmas having electron density of above 10^18 m-3, through the second stage where data accumulation be prerequisite for ne below 10^18 m-3, and to the third stage where a strong suppression of stray light in addition to the data accumulation be necessary to measure at an extremely small size of less than 100 μm near to material surfaces. The third stage LTS was first demonstrated for a PDP (plasma display panel)-like discharge three years ago employing a triple grating polychromator. In order to further expand its applicable ranges, we are pursuing a more general approach by taking into account such factors as laser divergence, stray light suppression and other aspects. The present status is presented. 1) K. Muraoka, K. Uchino, Y. Yamagata, Y. Noguchi, M. Mansour, P. Suanpoot, S. Narishige, and M. Noguchi, Plasma Sources Sci. Technol. 11 (2002) A143.
Cahyadi, Harsono; Iwatsuka, Junichi; Minamikawa, Takeo; Niioka, Hirohiko; Araki, Tsutomu; Hashimoto, Mamoru
2013-09-01
We develop a coherent anti-Stokes Raman scattering (CARS) microscopy system equipped with a tunable picosecond laser for high-speed wavelength scanning. An acousto-optic tunable filter (AOTF) is integrated in the laser cavity to enable wavelength scanning by varying the radio frequency waves applied to the AOTF crystal. An end mirror attached on a piezoelectric actuator and a pair of parallel plates driven by galvanometer motors are also introduced into the cavity to compensate for changes in the cavity length during wavelength scanning to allow synchronization with another picosecond laser. We demonstrate fast spectral imaging of 3T3-L1 adipocytes every 5 cm-1 in the Raman spectral region around 2850 cm-1 with an image acquisition time of 120 ms. We also demonstrate fast switching of Raman shifts between 2100 and 2850 cm-1, corresponding to CD2 symmetric stretching and CH2 symmetric stretching vibrations, respectively. The fast-switching CARS images reveal different locations of recrystallized deuterated and nondeuterated stearic acid.
On the Coulomb effect in laser-assisted proton scattering by a stationary atomic nucleus
Hrour, E.; Taj, S.; Chahboune, A.; El Idrissi, M.; Manaut, B.
2017-06-01
In the framework of the first Born approximation, we investigate the scenario where in addition to a laser field, a nuclear Coulomb field is also present to affect a proton. We work in the approximation in which the proton is considered to be a structureless spin 1/2 Dirac particle with a mass m p . Furthermore, in the laboratory system, the fixed nucleus is treated as a point-like Coulomb potential. In the presence of a laser field, and taking into account the Coulomb effect, the proton will be described by distorted Dirac-Volkov wave functions. The introduction of the Coulomb effect to both the incident and scattered proton will enhance the relativistic differential cross sections (RDCSs). Regarding the physical picture, it is found that for the various kinetic energies of the incident proton, the Coulomb effect can be neglected at high kinetic energies in this particular geometry. Therefore, Dirac-Volkov states are largely sufficient to describe the laser-dressed protons. The behavior of the various RDCSs versus the atomic number Z is also presented.
Methods and apparatus for transparent display using scattering nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Hsu, Chia Wei; Qiu, Wenjun; Zhen, Bo; Shapira, Ofer; Soljacic, Marin
2017-06-14
Transparent displays enable many useful applications, including heads-up displays for cars and aircraft as well as displays on eyeglasses and glass windows. Unfortunately, transparent displays made of organic light-emitting diodes are typically expensive and opaque. Heads-up displays often require fixed light sources and have limited viewing angles. And transparent displays that use frequency conversion are typically energy inefficient. Conversely, the present transparent displays operate by scattering visible light from resonant nanoparticles with narrowband scattering cross sections and small absorption cross sections. More specifically, projecting an image onto a transparent screen doped with nanoparticles that selectively scatter light at the image wavelength(s) yields an image on the screen visible to an observer. Because the nanoparticles scatter light at only certain wavelengths, the screen is practically transparent under ambient light. Exemplary transparent scattering displays can be simple, inexpensive, scalable to large sizes, viewable over wide angular ranges, energy efficient, and transparent simultaneously.
Methods and apparatus for transparent display using scattering nanoparticles
Hsu, Chia Wei; Qiu, Wenjun; Zhen, Bo; Shapira, Ofer; Soljacic, Marin
2016-05-10
Transparent displays enable many useful applications, including heads-up displays for cars and aircraft as well as displays on eyeglasses and glass windows. Unfortunately, transparent displays made of organic light-emitting diodes are typically expensive and opaque. Heads-up displays often require fixed light sources and have limited viewing angles. And transparent displays that use frequency conversion are typically energy inefficient. Conversely, the present transparent displays operate by scattering visible light from resonant nanoparticles with narrowband scattering cross sections and small absorption cross sections. More specifically, projecting an image onto a transparent screen doped with nanoparticles that selectively scatter light at the image wavelength(s) yields an image on the screen visible to an observer. Because the nanoparticles scatter light at only certain wavelengths, the screen is practically transparent under ambient light. Exemplary transparent scattering displays can be simple, inexpensive, scalable to large sizes, viewable over wide angular ranges, energy efficient, and transparent simultaneously.
Total internal reflection laser tools and methods
Energy Technology Data Exchange (ETDEWEB)
Zediker, Mark S.; Faircloth, Brian O.; Kolachalam, Sharath K.; Grubb, Daryl L.
2016-02-02
There is provided high power laser tools and laser heads that utilize total internal reflection ("TIR") structures to direct the laser beam along a laser beam path within the TIR structure. The TIR structures may be a TIR prism having its hypotenuse as a TIR surface.
Total internal reflection laser tools and methods
Energy Technology Data Exchange (ETDEWEB)
Zediker, Mark S.; Faircloth, Brian O.; Kolachalam, Sharath K.; Grubb, Daryl L.
2016-02-02
There is provided high power laser tools and laser heads that utilize total internal reflection ("TIR") structures to direct the laser beam along a laser beam path within the TIR structure. The TIR structures may be a TIR prism having its hypotenuse as a TIR surface.
Energy Technology Data Exchange (ETDEWEB)
Shidahara, Miho; Kato, Takashi; Kawatsu, Shoji; Yoshimura, Kumiko; Ito, Kengo [National Center for Geriatrics and Gerontology Research Institute, Department of Brain Science and Molecular Imaging, Obu, Aichi (Japan); Watabe, Hiroshi; Kim, Kyeong Min; Iida, Hidehiro [National Cardiovascular Center Research Institute, Department of Investigative Radiology, Suita (Japan); Kato, Rikio [National Center for Geriatrics and Gerontology, Department of Radiology, Obu (Japan)
2005-10-01
An image-based scatter correction (IBSC) method was developed to convert scatter-uncorrected into scatter-corrected SPECT images. The purpose of this study was to validate this method by means of phantom simulations and human studies with {sup 99m}Tc-labeled tracers, based on comparison with the conventional triple energy window (TEW) method. The IBSC method corrects scatter on the reconstructed image I{sub AC}{sup {mu}}{sup b} with Chang's attenuation correction factor. The scatter component image is estimated by convolving I{sub AC}{sup {mu}}{sup b} with a scatter function followed by multiplication with an image-based scatter fraction function. The IBSC method was evaluated with Monte Carlo simulations and {sup 99m}Tc-ethyl cysteinate dimer SPECT human brain perfusion studies obtained from five volunteers. The image counts and contrast of the scatter-corrected images obtained by the IBSC and TEW methods were compared. Using data obtained from the simulations, the image counts and contrast of the scatter-corrected images obtained by the IBSC and TEW methods were found to be nearly identical for both gray and white matter. In human brain images, no significant differences in image contrast were observed between the IBSC and TEW methods. The IBSC method is a simple scatter correction technique feasible for use in clinical routine. (orig.)
Deng, B H; Kinley, J S; Knapp, K; Feng, P; Martinez, R; Weixel, C; Armstrong, S; Hayashi, R; Longman, A; Mendoza, R; Gota, H; Tuszewski, M
2014-11-01
A two-chord far infrared (FIR) laser polarimeter for high speed sub-degree Faraday rotation measurements in the C-2 field reversed configuration experiment is described. It is based on high power proprietary FIR lasers with line width of about 330 Hz. The exceptionally low intrinsic instrument phase error is characterized with figures of merit. Significant toroidal magnetic field with rich dynamics is observed. Simultaneously obtained density fluctuation spectra by far forward scattering are presented.
HIGH-ORDER NYSTR(``O)M METHOD FOR THE EFIE OF EM SCATTERING PROBLEMS
Institute of Scientific and Technical Information of China (English)
Zhang Xiaojuan
2004-01-01
Nystrom method is a new method for solving electromagnetic scattering problems.This paper gives the detailed description on high-order Nystrom method used for the electric field integral equation of electromagnetic scattering problems. The numerical solutions of two examples are correct compared with Method Of Moment(MOM).
Energy Technology Data Exchange (ETDEWEB)
Ruehrnschopf, Ernst-Peter; Klingenbeck, Klaus [Siemens AG, Healthcare Sector, Imaging and Therapy Division, Forchheim (Germany)
2011-07-15
Since scattered radiation in cone-beam volume CT implies severe degradation of CT images by quantification errors, artifacts, and noise increase, scatter suppression is one of the main issues related to image quality in CBCT imaging. The aim of this review is to structurize the variety of scatter suppression methods, to analyze the common structure, and to develop a general framework for scatter correction procedures. In general, scatter suppression combines hardware techniques of scatter rejection and software methods of scatter correction. The authors emphasize that scatter correction procedures consist of the main components scatter estimation (by measurement or mathematical modeling) and scatter compensation (deterministic or statistical methods). The framework comprises most scatter correction approaches and its validity also goes beyond transmission CT. Before the advent of cone-beam CT, a lot of papers on scatter correction approaches in x-ray radiography, mammography, emission tomography, and in Megavolt CT had been published. The opportunity to avail from research in those other fields of medical imaging has not yet been sufficiently exploited. Therefore additional references are included when ever it seems pertinent. Scatter estimation and scatter compensation are typically intertwined in iterative procedures. It makes sense to recognize iterative approaches in the light of the concept of self-consistency. The importance of incorporating scatter compensation approaches into a statistical framework for noise minimization has to be underscored. Signal and noise propagation analysis is presented. A main result is the preservation of differential-signal-to-noise-ratio (dSNR) in CT projection data by ideal scatter correction. The objective of scatter compensation methods is the restoration of quantitative accuracy and a balance between low-contrast restoration and noise reduction. In a synopsis section, the different deterministic and statistical methods are
Inverse Scattering Method and Soliton Solution Family for String Effective Action
Institute of Scientific and Technical Information of China (English)
GAO Ya-Jun
2009-01-01
A modified Hauser-Ernst-type linear system is established and used to develop an inverse scattering method for solving the motion equations of the string effective action describing the coupled gravity, dilaton and Kalb-Ramond fields. The reduction procedures in this inverse scattering method are found to be fairly simple, which makes the proposed inverse scattering method applied fine and effective. As an application, a concrete family of soliton solutions for the considered theory is obtained.
Deformation of the J-matrix method of scattering
Alhaidari, A. D.
2002-01-01
We construct nonrelativistic J-matrix theory of scattering for a system whose reference Hamiltonian is enhanced by one-parameter linear deformation to account for nontrivial physical effects that could be modeled by a singular ground state coupling.
Computational method for the quantum Hamilton-Jacobi equation: one-dimensional scattering problems.
Chou, Chia-Chun; Wyatt, Robert E
2006-12-01
One-dimensional scattering problems are investigated in the framework of the quantum Hamilton-Jacobi formalism. First, the pole structure of the quantum momentum function for scattering wave functions is analyzed. The significant differences of the pole structure of this function between scattering wave functions and bound state wave functions are pointed out. An accurate computational method for the quantum Hamilton-Jacobi equation for general one-dimensional scattering problems is presented to obtain the scattering wave function and the reflection and transmission coefficients. The computational approach is demonstrated by analysis of scattering from a one-dimensional potential barrier. We not only present an alternative approach to the numerical solution of the wave function and the reflection and transmission coefficients but also provide a computational aspect within the quantum Hamilton-Jacobi formalism. The method proposed here should be useful for general one-dimensional scattering problems.
Bangaru, S.
2011-02-01
This paper reports the thermoluminescence (TL), optical absorption and other laser Raman scattering studies performed on terbium-doped KI crystals γ-irradiated at room temperature. Photoluminescence studies confirm the presence of terbium ions in the KI matrix in their trivalent form. Formation of V3- and Z1-centres on F-bleaching of γ-irradiated crystals was observed. The characteristic emission due to Tb3+ ions in the spectral distribution under optically stimulated emission and TL emission confirms the participation of the Tb3+ ions in the recombination process. The Raman bands were identified as the totally symmetric vibration modes of f.c.c. species KI:Tb3+.
Cao, Xuan; Feng, Jingjing; Pan, Qi; Xiong, Bin; He, Yan; Yeung, Edward S
2017-03-07
Understanding the heterogeneous distribution of the physical and chemical properties of plasmonic metal nanoparticles is fundamentally important to their basic and applied research. Traditionally, they are obtained either indirectly via bulk spectroscopic measurements plus electron microscopic characterizations or through single molecule/particle imaging of nanoparticles immobilized on planar substrates. In this study, by using light-sheet scattering microscopy with a supercontinuum white laser, highly sensitive imaging of individual metal nanoparticles (MNPs) flowing inside a capillary, driven by either pressure or electric field, was achieved for the first time. We demonstrate that single plasmonic nanoparticles with different size or chemical modification could be differentiated through their electrophoretic mobility in a few minutes. This technique could potentially be applied to high throughput characterization and evaluation of single metal nanoparticles as well as their dynamic interactions with various local environments.
Intense X-ray sources based on compton scattering in laser electron storage rings
Gladkikh, P I; Karnaukhov, I M
2002-01-01
The main problem of the designing of intense X-ray sources based on Compton scattering in laser-electron storage ring is associated with large steady-state electron beam energy spread. In paper the principles of the development of compact storage ring lattice with large RF-acceptance and negligible chromatic effects at interaction point are considered. The storage ring with electron beam energy over the range 100-400 MeV that allows generating intense VUV from bending magnets, X-ray up to 280 keV with rate up to 10 sup 1 sup 4 photons/s and gamma-beam up to 2.8 MeV for neutron generation on beryllium target is proposed.
Ultrafast laser-induced melting and ablation studied by time-resolved diffuse X-ray scattering
Directory of Open Access Journals (Sweden)
Meyer zu Heringdorf F.
2013-03-01
Full Text Available Time-resolved diffuse X-ray scattering with 50 fs, 9.5 keV X-ray pulses from the Linear Coherent Light Source was used to study the structural dynamics in materials undergoing rapid melting and ablation after fs laser excitation.
Joo, H
1999-01-01
Recent test results indicated drawbacks associated with the simple exponential attenuation method (SEAM) as currently applied to neutron radiography measurements to determine vapor fractions in a hydrogenous two-phase flow in a metallic conduit. The scattering component of the neutron beam intensity exiting the flow system is not adequately accounted for by SEAM, and this leads to inaccurate results. To properly account for the scattering effect, a neutron scattering probability method (SPM) is developed. The method applies a neutron-hydrogen scattering kernel to scattered thermal neutrons that leave the incident beam in narrow conduits but eventually show up elsewhere in the measurements. The SPM has been tested with known vapor (void) distributions within an acrylic disk and a water/vapor channel. The vapor (void) fractions deduced by SPM are in good agreement with the known exact values. Details of the scattering correction method and the test results are discussed.
Free-electron laser based resonant inelastic X-ray scattering on molecules and liquids
Energy Technology Data Exchange (ETDEWEB)
Kunnus, Kristjan, E-mail: kkunnus@stanford.edu [Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam (Germany); Schreck, Simon; Föhlisch, Alexander [Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam (Germany)
2015-10-15
Highlights: • Femtosecond time-resolved RIXS can be used to follow charge, spin and structural dynamics of dilute solute molecules in solution. • Ultrashort X-ray pulses allow probing of highly radiation sensitive states of matter. • Nonlinear X-ray probes provide an enhanced selectivity and sensitivity as well as a path to control radiation damage and increase the photon yields in RIXS experiments. - Abstract: The unprecedented beam properties of free-electron laser based X-ray sources enable novel resonant inelastic X-ray scattering (RIXS) experiments. Femtosecond time-resolved RIXS can be used to follow charge, spin and structural dynamics of dilute solute molecules in solution. Ultrashort X-ray pulses allow probing of highly radiation sensitive states of matter such as the metastable phase of supercooled liquid water. Nonlinear X-ray probes like amplified spontaneous emission and stimulated resonant X-ray scattering provide an enhanced selectivity and sensitivity as well as a path to control radiation damage and increase the photon yields in RIXS experiments.
SU-E-I-08: Investigation of Deconvolution Methods for Blocker-Based CBCT Scatter Estimation
Energy Technology Data Exchange (ETDEWEB)
Zhao, C; Jin, M [University of Texas at Arlington, Arlington, TX (United States); Ouyang, L; Wang, J [UT Southwestern Medical Center at Dallas, Dallas, TX (United States)
2015-06-15
Purpose: To investigate whether deconvolution methods can improve the scatter estimation under different blurring and noise conditions for blocker-based scatter correction methods for cone-beam X-ray computed tomography (CBCT). Methods: An “ideal” projection image with scatter was first simulated for blocker-based CBCT data acquisition by assuming no blurring effect and no noise. The ideal image was then convolved with long-tail point spread functions (PSF) with different widths to mimic the blurring effect from the finite focal spot and detector response. Different levels of noise were also added. Three deconvolution Methods: 1) inverse filtering; 2) Wiener; and 3) Richardson-Lucy, were used to recover the scatter signal in the blocked region. The root mean square error (RMSE) of estimated scatter serves as a quantitative measure for the performance of different methods under different blurring and noise conditions. Results: Due to the blurring effect, the scatter signal in the blocked region is contaminated by the primary signal in the unblocked region. The direct use of the signal in the blocked region to estimate scatter (“direct method”) leads to large RMSE values, which increase with the increased width of PSF and increased noise. The inverse filtering is very sensitive to noise and practically useless. The Wiener and Richardson-Lucy deconvolution methods significantly improve scatter estimation compared to the direct method. For a typical medium PSF and medium noise condition, both methods (∼20 RMSE) can achieve 4-fold improvement over the direct method (∼80 RMSE). The Wiener method deals better with large noise and Richardson-Lucy works better on wide PSF. Conclusion: We investigated several deconvolution methods to recover the scatter signal in the blocked region for blocker-based scatter correction for CBCT. Our simulation results demonstrate that Wiener and Richardson-Lucy deconvolution can significantly improve the scatter estimation
The Brief Introduction of Different Laser Diagnostics Methods Used in Aeroengine Combustion Research
Directory of Open Access Journals (Sweden)
Fei Xing
2016-01-01
Full Text Available Combustion test diagnosis has always been one of the most important technologies for the development of aerospace engineering. The traditional methods of measurement have been unable to meet the requirements of accurate capture of the flow field in the development process of the aeroengine combustor. Therefore, the development of high-precision measurement and diagnostic techniques to meet the needs of the aeroengine combustor design is imperative. Laser diagnostics techniques developed quickly in the past several years. They are used to measure the parameters of the combustion flow field such as velocity, temperature, and components concentration with high space and time resolution and brought no disturbance. Planar laser-induced fluorescence, coherent anti-Stokes Raman scattering, tunable diode laser absorption spectroscopy, and Raman scattering were introduced systemically in this paper. After analysis of their own advantages and disadvantages, the authors considered validated Raman scattering system and Tunable Diode Laser Absorption Tomography are more suitable for research activities on aeroengine combustion systems.
Energy Technology Data Exchange (ETDEWEB)
Bito, Kotatsu [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Analytical Science Research Laboratories, Kao Corporation, 2606 Akabane, Ichikai-Machi, Haga-Gun, Tochigi 321-3497 (Japan); Okuno, Masanari [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Kano, Hideaki [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tenodai, Tsukuba, Ibaraki 305-8573 (Japan); Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Leproux, Philippe [Institut de Recherche XLIM, UMR CNRS No. 7252, 123 Avenue Albert Thomas, 87060 Limoges Cedex (France); LEUKOS, ESTER Technopole, 1 Avenue d’Ester, 87069 Limoges Cedex (France); Couderc, Vincent [Institut de Recherche XLIM, UMR CNRS No. 7252, 123 Avenue Albert Thomas, 87060 Limoges Cedex (France); Hamaguchi, Hiro-o, E-mail: hhama@nctu.edu.tw [Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Institute of Molecular Science and Department of Applied Chemistry, National Chiao Tung University, 1001 Ta Hsueh Road, Hsinchu 300, Taiwan (China)
2013-06-20
Highlights: ► We have developed a simultaneous measurement system of CARS and CSRS. ► We can obtain information on the electronic resonance effect with the measurement. ► The simultaneous measurement provides us with more reliable spectral information. - Abstract: We have developed a three-pulse non-degenerate multiplex coherent Raman microspectroscopic system using a white-light laser source. The fundamental output (1064 nm) of a Nd:YAG laser is used for the pump radiation with the white-light laser output (1100–1700 nm) for the Stokes radiation to achieve broadband multiplex excitations of vibrational coherences. The second harmonic (532 nm) of the same Nd:YAG laser is used for the probe radiation. Thanks to the large wavelength difference between the pump and probe radiations, coherent anti-Stokes Raman scattering (CARS) and coherent Stokes Raman scattering (CSRS) can be detected simultaneously. Simultaneous detection of CARS and CSRS enables us to obtain information on the electronic resonance effect that affects differently the CARS and CSRS signals. Simultaneous analysis of the CARS and CSRS signals provides us the imaginary part of χ{sup (3)} without introducing any arbitrary parameter in the maximum entropy method (MEM)
METHOD AND SYSTEM FOR LASER WELDING
DEFF Research Database (Denmark)
2008-01-01
The invention relates to laser welding of at least two adjacent, abutting or overlapping work pieces in a welding direction using multiple laser beams guided to a welding region, wherein at least two of the multiple laser beams are coupled into the welding region so as to form a melt and at least...
Lara, O
1995-01-01
continued fractions are now in progress. It is well known that multichannel effects strongly influence the low-energy electron scattering by atoms and molecules. Nevertheless, the inclusion of such effects on the calculations of scattering cross sections remains a considerable task for the area researches due to the complexity of the problem. In the present study we aim to develop a new theoretical method which can be efficiently applied to the multichannel scattering studies. Two new theoretical formalisms namely the Multichannel sup - C-Functional Method have been proposed. Both methods were developed on the base of well-known distorted-wave method combined with Schwinger variational principle. In addition, an integrative method proposed by Horacek and Sasakawa in 1983, the method of continued fractions is adapted by the first time to multichannel scatterings. Numerical test of these three methods were carried out through applications to solve the multichannel scattering problems involving the interaction o...
Jagodzinski, Jeremy James
2007-12-01
The development to date of a diode-laser based velocimeter providing point-velocity-measurements in unseeded flows using molecular Rayleigh scattering is discussed. The velocimeter is based on modulated filtered Rayleigh scattering (MFRS), a novel variation of filtered Rayleigh scattering (FRS), utilizing modulated absorption spectroscopy techniques to detect a strong absorption of a relatively weak Rayleigh scattered signal. A rubidium (Rb) vapor filter is used to provide the relatively strong absorption; alkali metal vapors have a high optical depth at modest vapor pressures, and their narrow linewidth is ideally suited for high-resolution velocimetry. Semiconductor diode lasers are used to generate the relatively weak Rayleigh scattered signal; due to their compact, rugged construction diode lasers are ideally suited for the environmental extremes encountered in many experiments. The MFRS technique utilizes the frequency-tuning capability of diode lasers to implement a homodyne detection scheme using lock-in amplifiers. The optical frequency of the diode-based laser system used to interrogate the flow is rapidly modulated about a reference frequency in the D2-line of Rb. The frequency modulation is imposed on the Rayleigh scattered light that is collected from the probe volume in the flow under investigation. The collected frequency modulating Rayleigh scattered light is transmitted through a Rb vapor filter before being detected. The detected modulated absorption signal is fed to two lock-in amplifers synchronized with the modulation frequency of the source laser. High levels of background rejection are attained since the lock-ins are both frequency and phase selective. The two lock-in amplifiers extract different Fourier components of the detected modulated absorption signal, which are ratioed to provide an intensity normalized frequency dependent signal from a single detector. A Doppler frequency shift in the collected Rayleigh scattered light due to a change
Stimulated Raman scattering in hydrogen by ultrashort laser pulse in the keV regime
Bachau, H.; Dondera, M.
2016-04-01
This letter addresses the problem of stimulated Raman excitation of a hydrogen atom submitted to an ultrashort and intense laser pulse in the keV regime. The pulse central frequency ω of 55 a.u. (about 1.5 keV) is in the weakly relativistic regime, ω ≤ c/a0 (c is the speed of light in vacuum and a 0 the Bohr radius) and the pulse duration is τ ≈ 18.85 a.u. (about 456 attoseconds). We solve the corresponding time-dependent Schrödinger equation (TDSE) using a spectral approach, retardation (or nondipole) effects are included up to O(1/c) , breaking the conservation of the magnetic quantum number m and forcing the resolution of the TDSE in a three-dimensional space. Due to the laser bandwidth, which is of the order of the ionization potential of hydrogen, stimulated Raman scattering populates nlm excited states (n and l are the principal and azimuthal quantum numbers, respectively). The populations of these excited states are calculated and analyzed in terms of l and m quantum numbers, this showing the contributions of the retardation effects and their relative importance.
Stimulated Raman scattering in helium with soft-x-ray laser radiation
Fill, E. E.; van Enk, S. J.; Zhang, Jian; Lambropoulos, P.
1996-12-01
We report calculations for stimulated Raman scattering (SRS) with pump photons from a soft-x-ray laser. The Raman transitions from the 1 1S0 ground state to the 2 1S0 and 3 1S0 metastable states of helium at 20.6 and 22.9 eV, respectively, are considered. We calculate χ(3) for pump photons with an energy close to the autoionizing resonances (2s2p)1P at 60.15 eV and (sp,23+)1P at 63.66 eV. SRS gain coefficients are derived for x-ray laser lines in close resonance with the autoionizing levels, viz., the 3p(3/2,3/2)2-->3s(3/2,1/2)1 transition in neonlike selenium (λ=20.64 nm) and the analogous transition in neonlike bromine (λ=19.47 nm). It is shown that the Raman gain coefficient with experimentally realistic parameters is significant and that a high gain length product can be achieved even with pump intensities below 1011 W/cm2.
Institute of Scientific and Technical Information of China (English)
ZHENG Jing-hua; HAO Xiao-fei; HAO Dong-shan
2004-01-01
Using the single particle theory and the non-flexibility collision model of electron and photon, the influence of the uncaptured electrons on the energy conversion efficiency of multi-photon nonlinear Compton scattering in the extra stationary laser-plasma is investigated. It shows that in extra stationary laser-plasma,the uncaptured electrons make the Δω of the scattering frequency of the multi-photon Compton fall down with the increases of the incident radiation electron speed,the materials of the incident collision of electron and photon, and the number of the photons which work with the electrons at the same time. Under the modulation of the uncaptured electrons to the laser field, the energy conversion efficiency between electrons and photons will fall down with the increase of the electron incident radiation speed, using the low-power electrons for incident source, the loss can be efficiently reduced.
Benabid, F.; Notcutt, M.; Ju, L.; Blair, D. G.
1999-10-01
We present the level of noise induced by Rayleigh-scattered light from sapphire test mass, the limit of scattering loss on build-up power inside the interferometer and finally the tolerable absorption loss in order to meet the specification of the interferometer sensitivity. The results show that the Rayleigh scattering induced noise remains below h˜10 -25 Hz -1/2 and a higher tolerance on the absorption level in sapphire substrate compared with silica substrate.
Barborica, A.; Mihailescu, I. N.; Teodorescu, V. S.
1994-03-01
We introduce a theoretical analysis of the temporal and spatial evolution of the surface topography of solids following interference between incident and scattered pulsed laser beams. The essential role played by the nonlinear delayed feedback in the laser-radiation-surface system is considered. We show that it finally determines the surface topography evolution from pulse to pulse. In order to complete the analysis, numerical calculations have been conducted under the hypothesis of strong attenuation of laser radiation into the sample and of a limited heat diffusion during the action of a laser pulse. We predict an evolution from very simple to complex (chaotic) structures under multiple-pulse-laser irradiation of solid surfaces. This evolution is determined by some key irradiation parameters; initial surface microrelief, incident laser intensity, and the number of applied laser pulses. Experiments were performed in order to check the main predictions of the theoretical analysis. The system of transversal excited atmospheric pressure-CO2 laser radiation (λ=10.6 μm)-interacting with fused silica was chosen as appropriate for performing test experiments. Optical microscopy studies of laser-treated zones evidenced special modifications of the surface topography in good accordance with the conclusions following from the theoretical analysis. The theoretical analysis is also in good agreement with some available data from the literature, at the same time providing a coherent interpretation of previously unexplained behaviors.
Relativistic mirrors in laser plasmas (analytical methods)
Bulanov, S. V.; Esirkepov, T. Zh; Kando, M.; Koga, J.
2016-10-01
Relativistic flying mirrors in plasmas are realized as thin dense electron (or electron-ion) layers accelerated by high-intensity electromagnetic waves to velocities close to the speed of light in vacuum. The reflection of an electromagnetic wave from the relativistic mirror results in its energy and frequency changing. In a counter-propagation configuration, the frequency of the reflected wave is multiplied by the factor proportional to the Lorentz factor squared. This scientific area promises the development of sources of ultrashort x-ray pulses in the attosecond range. The expected intensity will reach the level at which the effects predicted by nonlinear quantum electrodynamics start to play a key role. We present an overview of theoretical methods used to describe relativistic flying, accelerating, oscillating mirrors emerging in intense laser-plasma interactions.
Application of numerical methods to planetary radiowave scattering
Simpson, Richard A.; Tyler, G. Leonard
1987-01-01
Existing numerical techniques for the solution of scattering problems were investigated to determine those which might be applicable to planetary surface studies, with the goal of improving the interpretation of radar data from Venus, Mars, the Moon, and icy satellites. The general characteristics of the models are described along with computational concerns. In particular, the Numerical Electrogmatics Code (NEC) developed at the Lawrence Livermore Laboratory is discussed. Though not developed for random rough surfaces, the NEC contains elements which may be generalized and which could be valuable in the study of scattering by planetary surfaces.
Schomerus, H; Patra, M; Beenakker, C W J
1999-01-01
The quantum-limited linewidth of a laser cavity is enhanced above the Schawlow-Townes value by the Petermann factor K, due to the non-orthogonality of the cavity modes. We derive the relation between the Petermann factor and the residues of poles of the scattering matrix and investigate the statistical properties of the Petermann factor for cavities in which the radiation is scattered chaotically. For a single scattering channel we determine the complete probability distribution of K and find that the average Petermann factor $$ depends non-analytically on the area of the opening, and greatly exceeds the most probable value. For an arbitrary number N of scattering channels we calculate $$ as a function of the decay rate $\\Gamma$ of the lasing mode. We find for $N\\gg 1$ that for typical values of $\\Gamma$ the average Petermann factor $\\propto \\sqrt{N}\\gg 1$ is parametrically larger than unity.
DEFF Research Database (Denmark)
Larsen, Niels Vesterdal
2007-01-01
This report documents the implementation of Method of Auxiliary Sources techniques developed for smooth scatterers and wire scatterers. The work was done in the course of the PhD project "Electronically Steerable Antennas for Satellite Communication" where the techniques were employed to investig......This report documents the implementation of Method of Auxiliary Sources techniques developed for smooth scatterers and wire scatterers. The work was done in the course of the PhD project "Electronically Steerable Antennas for Satellite Communication" where the techniques were employed...
Robust scatter correction method for cone-beam CT using an interlacing-slit plate
Huang, Kui-Dong; Xu, Zhe; Zhang, Ding-Hua; Zhang, Hua; Shi, Wen-Long
2016-06-01
Cone-beam computed tomography (CBCT) has been widely used in medical imaging and industrial nondestructive testing, but the presence of scattered radiation will cause significant reduction of image quality. In this article, a robust scatter correction method for CBCT using an interlacing-slit plate (ISP) is carried out for convenient practice. Firstly, a Gaussian filtering method is proposed to compensate the missing data of the inner scatter image, and simultaneously avoid too-large values of calculated inner scatter and smooth the inner scatter field. Secondly, an interlacing-slit scan without detector gain correction is carried out to enhance the practicality and convenience of the scatter correction method. Finally, a denoising step for scatter-corrected projection images is added in the process flow to control the noise amplification The experimental results show that the improved method can not only make the scatter correction more robust and convenient, but also achieve a good quality of scatter-corrected slice images. Supported by National Science and Technology Major Project of the Ministry of Industry and Information Technology of China (2012ZX04007021), Aeronautical Science Fund of China (2014ZE53059), and Fundamental Research Funds for Central Universities of China (3102014KYJD022)
Aubry, Alexandre
2009-01-01
We present an imaging technique particularly suited to the detection of a target embedded in a strongly scattering medium. Classical imaging techniques based on the Born approximation fail in this kind of configuration because of multiply scattered echoes and aberration distorsions. The experimental set up we consider uses an array of programmable transmitters/receivers. A target is placed behind a scattering medium. The impulse responses between all array elements are measured and form a matrix. The core of the method is to separate the single-scattered echo of the target from the multiple scattering background. This is possible because of a deterministic coherence along the antidiagonals of the array response matrix, which is typical of single scattering. Once this operation is performed, target detection is achieved by applying the DORT method (French acronym for decomposition of the time reversal operator). Experimental results are presented in the case of wide-band ultrasonic waves around 3 MHz. A 125-el...
Energy Technology Data Exchange (ETDEWEB)
Francoeur, Mathieu [Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40506 (United States); Rousse, Daniel R [Department of Mathematics, Computer Sciences, and Engineering, Universite du Quebec a Rimouski, Levis, PQ G6V 8R9 (Canada)
2007-09-21
Optical tomography (OT) is a promising non-intrusive characterization technique of absorbing and scattering media that uses transmitted and/or reflected signals of samples irradiated with visible or near-infrared light. The quality of OT techniques is directly related to the accuracy of their forward models due to the use of inversion algorithms. In this paper, forward models for transient OT approaches are investigated. The system under study involves a one-dimensional absorbing and scattering medium illuminated by a short laser pulse; this problem is solved using a discrete ordinates-finite volume (DO-FV) method in both time and frequency domain. Previous works have shown that time-domain approaches coupled with first order spatial interpolation schemes cannot represent the physics of the problem adequately as transmitted fluxes emerge before the minimal physical time required to leave the medium. In this work, the Van Leer and Superbee flux limiters, combined with the second order Lax-Wendroff scheme, are used in an attempt to prevent this. Results show that despite significant improvement, flux limiters fail to completely eliminate the physically unrealistic behaviour. On the other hand, results for transmittance obtained from the frequency-based method are accurate, without physically unrealistic behaviours at early time periods. The frequency-dependent approach is however computationally expensive, since it requires approximately five times more computational time than its temporal counterpart when used as a forward model for transient OT. On the other hand, the great advantages of the frequency-based approach is that limited windows of temporal signals can be calculated efficiently (in transient OT), and it can also be used as a forward model for steady-state, frequency-based and transient OT techniques.
Box, M. A.; Deepak, A.
1981-01-01
The propagation of photons in a medium with strongly anisotropic scattering is a problem with a considerable history. Like the propagation of electrons in metal foils, it may be solved in the small-angle scattering approximation by the use of Fourier-transform techniques. In certain limiting cases, one may even obtain analytic expressions. This paper presents some of these results in a model-independent form and also illustrates them by the use of four different phase-function models. Sample calculations are provided for comparison purposes
Energy Technology Data Exchange (ETDEWEB)
Robbins, D.J.; Cullis, A.G.; Pidduck, A.J. (Royal Signals and Radar Establishment, Malvern (United Kingdom))
Elastic scattering of laser light has been used to monitor surface topography in real time during growth of Si{sub 1-x}Ge{sub x} heterostructures. Large increases in scattered intensity were caused by surface height fluctuations in the alloy layers which, after growth, could be imaged in cross section by transmission electron microscopy and in plan view by scanning optical microscopy. For pseudomorphic alloy layers (x = 0.19 {plus minus} 0.01) grown at 750C the surface height fluctuations were periodic, the wavelength of approximately 270 nm giving strong laser scattering. Plan view transmission electron micrographs on such a layer showed periodic strain fluctuations with the same wavelength, whereas an equivalent layer grown at 610C showed strain fluctuations which were irregular in shape and spatial distribution. The intensity of light scattered from the surface of this layer was much lower. Thick alloy layers grown beyond the critical thickness for appearance of misfit dislocations showed strong scatter which increased more quickly in intensity at higher growth temperature.
An Analytical Method of Auxiliary Sources Solution for Plane Wave Scattering by Impedance Cylinders
DEFF Research Database (Denmark)
Larsen, Niels Vesterdal; Breinbjerg, Olav
2004-01-01
Analytical Method of Auxiliary Sources solutions for plane wave scattering by circular impedance cylinders are derived by transformation of the exact eigenfunction series solutions employing the Hankel function wave transformation. The analytical Method of Auxiliary Sources solution thus obtained...
Directory of Open Access Journals (Sweden)
Zhenxu Bai
2016-01-01
Full Text Available A high beam quality hundred picoseconds single-longitudinal-mode (SLM laser is demonstrated based on stimulated Brillouin scattering (SBS pulse compression and aberration compensation. Flash-lamp-pumped Q-switched Nd3+:Y3Al5O12 (Nd:YAG SLM laser with Cr4+:Y3Al5O12 (Cr4+:YAG as a saturable absorber is used as the seed source. By combining master-oscillator-power-amplifier (MOPA, a compact single-cell with FC-770 as working medium is generated as pulse compressor. The 7.8 ns SLM laser is temporally compressed to about 450 ps, and 200 mJ energy is obtained at 1064 nm without optical damage. The energy stability is better than 3% with beam quality factor M2 less than 1.8, which makes this laser system an attractive source for scientific and industrial applications.
Zhang, Yu-Yin; Yoshizaki, Takuo; Nishida, Keiya
2000-11-01
The droplets and vapor distributions in a fuel spray were imaged by a dual-wavelength laser absorption scattering technique. 1,3-dimethylnaphthalene, which has physical properties similar to those of Diesel fuel, strongly absorbs the ultraviolet light near the fourth harmonic (266 nm) of a Nd:YAG laser but is nearly transparent to the visible light near the second harmonic (532 nm) of a Nd:YAG laser. Therefore, droplets and vapor distributions in a Diesel spray can be visualized by an imaging system that uses a Nd:YAG laser as the incident light and 1,3-dimethylnaphthalene as the test fuel. For a quantitative application consideration, the absorption coefficients of dimethylnapthalene vapor at different temperatures and pressures were examined with an optical spectrometer. The findings of this study suggest that this imaging technique has great promise for simultaneously obtaining quantitative information of droplet density and vapor concentration in Diesel fuel spray.
Zhang, Y Y; Yoshizaki, T; Nishida, K
2000-11-20
The droplets and vapor distributions in a fuel spray were imaged by a dual-wavelength laser absorption-scattering technique. 1,3-dimethylnaphthalene, which has physical properties similar to those of Diesel fuel, strongly absorbs the ultraviolet light near the fourth harmonic (266 nm) of a Nd:YAG laser but is nearly transparent to the visible light near the second harmonic (532 nm) of a Nd:YAG laser. Therefore, droplets and vapor distributions in a Diesel spray can be visualized by an imaging system that uses a Nd:YAG laser as the incident light and 1,3-dimethylnaphthalene as the test fuel. For a quantitative application consideration, the absorption coefficients of dimethylnapthalene vapor at different temperatures and pressures were examined with an optical spectrometer. The findings of this study suggest that this imaging technique has great promise for simultaneously obtaining quantitative information of droplet density and vapor concentration in Diesel fuel spray.
Analysis of Scattering from Archival Pulsar Data using a CLEAN-based Method
Tsai, -Wei, Jr.; Simonetti, John H.; Kavic, Michael
2017-02-01
In this work, we adopted a CLEAN-based method to determine the scatter time, τ, from archived pulsar profiles under both the thin screen and uniform medium scattering models and to calculate the scatter time frequency scale index α, where τ \\propto {ν }α . The value of α is ‑4.4, if a Kolmogorov spectrum of the interstellar medium turbulence is assumed. We deconvolved 1342 profiles from 347 pulsars over a broad range of frequencies and dispersion measures. In our survey, in the majority of cases the scattering effect was not significant compared to pulse profile widths. For a subset of 21 pulsars scattering at the lowest frequencies was large enough to be measured. Because reliable scatter time measurements were determined only for the lowest frequency, we were limited to using upper limits on scatter times at higher frequencies for the purpose of our scatter time frequency slope estimation. We scaled the deconvolved scatter time to 1 GHz assuming α =-4.4 and considered our results in the context of other observations which yielded a broad relation between scatter time and dispersion measure.
Using inverse scattering methods to study inter-nucleus potentials
MacIntosh, R S
1998-01-01
It is now straightforward to carry out S-matrix to potential inversion over a very wide range of energies and for a wide range of projectile-target combinations. Inversion is possible in many cases involving spin. IP inversion also permits direct scattering data-to-potential inversion and furnishes powerful tools for the phenomenological analysis of nuclear scattering. The resulting single particle potentials exhibit various generic properties which challenge fundamental reaction theories as well as yield information on densities, provide input for reaction calculations. S-matrix to potential inversion is also a powerful tool for directly investigating theoretical processes which contribute to inter-nuclear potentials. Various studies have given insight into contributions to the dynamic polarisation potential (DPP) due to breakup processes and due to collective and reaction channel coupling and have also illuminated the role played by exchange processes in leading to non-locality and parity dependence of the ...
Institute of Scientific and Technical Information of China (English)
ZHOU Bin; LI Shu-Min
2010-01-01
@@ We study the elastic scattering of atomic argon by an electron in the presence of a bichromatic laser field in the second Born approximation.The target atom is approximated by a simple screening potential.We explore the dependences of the differential cross sections on the relative phase (φ) between the two components of the radiation field and discuss the influence of the number of photons exchanged on the phase-dependence effect.Moreover,for different scattering angles and incident electron energies,the differential cross sections are notably different.
The algebraic method of the scattering inverse problem solution under untraditional statements
Popushnoj, M N
2001-01-01
The algebraic method of the scattering inverse problem solution under untraditional statements is proposed consistently in this review, in the framework of which some quantum theory od scattering charged particles problem were researched afterwards. The inverse problem of scattering theory of charged particles on the complex plane of the Coulomb coupling constant (CCC) is considered. A procedure of interaction potential restoration is established for the case when the energy, orbital moment quadrate and CCC are linearly dependent. The relation between one-parametric problems of the potential scattering of charged particles is investigated
Eremin, Yuri; Wriedt, Thomas
2014-12-01
The Discrete Sources Method (DSM) has been modified to analyze polarized light scattering by an axial symmetric penetrable nanoparticle partially embedded into a substrate. The new numerical scheme of the DSM enables to consider scattering from such substrate defects as flat particles, mounds, pits and voids. A detailed description of the numerical scheme is provided. The developed computer model has been employed to investigate scattering from a shallow particle and pit. Simulation results corresponding to the Differential Scattering Cross-Section and the integral response for P/S polarized light are presented.
Modeling quantum mechanical scattering with continuous analogue of the newton method
Directory of Open Access Journals (Sweden)
Algirdas Deveikis
2013-09-01
Full Text Available Computational modelling of potential and resonant scattering for short range and Coulomb potentials was investigated in this study. The resonant scattering problem is formulated with the short range potential composed of a spherically symmetric square well and spherically symmetric square barrier. An iteration scheme of a continuous analogue of the Newton method for continuous spectral problem with correct asymptotic in uncoupled partial waves has been developed. The nonlinear representation of the scattering problem for the normalized radial Schrödinger equation is solved numerically using the difference sweep technique. The second order accuracy scheme developed allow to find scattering phases and wave functions as well as investigate their numerical evolution. The scattering phases and wave functions dependence on the scattering problem parameters have been studied.
A topographic parameter inversion method based on laser altimetry
Institute of Scientific and Technical Information of China (English)
HUANG ChunMing; ZHANG ShaoDong; CHEN Xi
2012-01-01
A topographic parameter inversion method based on laser altimetry is developed in this paper,which can be used to deduce the surface vertical profile and retrieve the topographic parameters within the laser footprints by analyzing and simulating return waveforms.This method comprises three steps.The first step is to build the numerical models for the whole measuring procedure of laser altimetry,construct digital elevation models for surfaces with different topographic parameters,and calculate return waveforms.The second step is to analyze the simulated return waveforms to obtain their characteristics parameters,summarize the effects of the topographic parameter variations on the characteristic parameters of simulated return waveforms,and analyze the observed return waveforms of laser altimeters to acquire their characteristic parameters at the same time.The last step is to match the characteristic parameters of the simulated and observed return waveforms,and deduce the topographic parameters within the laser footprint.This method can be used to retrieve the topographic parameters within the laser footprint from the observed return waveforms of spaceborne laser altimeters and to get knowledge about the surface altitude distribution within the laser footprint other than only getting the height of the surface encountered firstly by the laser beam,which extends laser altimeters' function and makes them more like radars.
Method and apparatus for enhancing laser absorption sensitivity
Webster, Christopher R. (Inventor)
1987-01-01
A simple optomechanical method and apparatus is described for substantially reducing the amplitude of unwanted multiple interference fringes which often limit the sensitivities of tunable laser absorption spectrometers. An exterior cavity is defined by partially transmissible surfaces such as a laser exit plate, a detector input, etc. That cavity is spoiled by placing an oscillating plate in the laser beam. For tunable diode laser spectroscopy in the mid-infrared region, a Brewster-plate spoiler allows the harmonic detection of absorptances of less than 10 to the -5 in a single laser scan. Improved operation is achieved without subtraction techniques, without complex laser frequency modulation, and without distortion of the molecular lineshape signal. The technique is applicable to tunable lasers operating from UV to IR wavelengths and in spectrometers which employ either short or long pathlengths, including the use of retroreflectors or multipass cells.
DEFF Research Database (Denmark)
Karamehmedovic, Mirza; Breinbjerg, Olav
2002-01-01
The Method of Auxiliary Sources (MAS) is applied to 3D scattering problems involving spherical impedance scatterers. The MAS results are compared with the reference spherical wave expansion (SWE) solution. It is demonstrated that good agreement is achieved between the MAS and SWE results....
La Budde, R. A.
1972-01-01
Sampling techniques have been used previously to evaluate Jacobian determinants that occur in classical mechanical descriptions of molecular scattering. These determinants also occur in the quasiclassical approximation. A new technique is described which can be used to evaluate Jacobian determinants which occur in either description. This method is expected to be valuable in the study of reactive scattering using the quasiclassical approximation.
The slab albedo problem for the triplet scattering kernel with modified F{sub N} method
Energy Technology Data Exchange (ETDEWEB)
Tuereci, Demet [Ministry of Education, 75th year Anatolia High School, Ankara (Turkey)
2016-12-15
One speed, time independent neutron transport equation for a slab geometry with the quadratic anisotropic scattering kernel is considered. The albedo and transmission factor are calculated by the modified F{sub N} method. The obtained numerical results are listed for different scattering coefficients.
Liu, Xiaodong
2017-08-01
A sampling method by using scattering amplitude is proposed for shape and location reconstruction in inverse acoustic scattering problems. Only matrix multiplication is involved in the computation, thus the novel sampling method is very easy and simple to implement. With the help of the factorization of the far field operator, we establish an inf-criterion for characterization of underlying scatterers. This result is then used to give a lower bound of the proposed indicator functional for sampling points inside the scatterers. While for the sampling points outside the scatterers, we show that the indicator functional decays like the bessel functions as the sampling point goes away from the boundary of the scatterers. We also show that the proposed indicator functional continuously depends on the scattering amplitude, this further implies that the novel sampling method is extremely stable with respect to errors in the data. Different to the classical sampling method such as the linear sampling method or the factorization method, from the numerical point of view, the novel indicator takes its maximum near the boundary of the underlying target and decays like the bessel functions as the sampling points go away from the boundary. The numerical simulations also show that the proposed sampling method can deal with multiple multiscale case, even the different components are close to each other.
The second Born approximation of electron–argon elastic scattering in a bichromatic laser ﬁeld
Indian Academy of Sciences (India)
Bin Zhou; Ming-Yang Zheng; Da-Yong Wen
2012-03-01
We study the elastic scattering of atomic argon by electron in the presence of a bichromatic laser ﬁeld in the second Born approximation. The target atom is approximated by a simple screening potential and the continuum states of the impinging and emitting electrons are described as Volkov states. We evaluate the S-matrix elements numerically. The dependence of differential cross-section on the relative phase between the two laser components is presented. The results obtained in the ﬁrst and second Born approximations are compared and analysed.
Efficient method for the calculation of dissipative quantum transport in quantum cascade lasers.
Greck, Peter; Birner, Stefan; Huber, Bernhard; Vogl, Peter
2015-03-09
We present a novel and very efficient method for calculating quantum transport in quantum cascade lasers (QCLs). It follows the nonequilibrium Green's function (NEGF) framework but sidesteps the calculation of lesser self-energies by replacing them by a quasi-equilibrium expression. This method generalizes the phenomenological Büttiker probe model by taking into account individual scattering mechanisms. It is orders of magnitude more efficient than a fully self-consistent NEGF calculation for realistic devices. We apply this method to a new THz QCL design which works up to 250 K - according to our calculations.
Filamentation and Forward Brillouin Scatter of Entire Smoothed and Aberrated Laser Beams
Energy Technology Data Exchange (ETDEWEB)
Still, C.H.; Berger, R.L.; Langdon, A.B.; Hinkel, D.E.; Williams, E.A.
1999-10-29
Laser-plasma interactions are sensitive to both the fine-scale speckle and the larger scale envelope intensity of the beam. For some time, simulations have been done on volumes taken from part of the laser beam cross-section, and the results from multiple simulations extrapolated to predict the behavior of the entire beam. However, extrapolation could very well miss effects of the larger scale structure on the fine-scale. The only definitive method is to simulate the entire beam. These very large calculations have been infeasible until recently, but they are now possible on massively parallel computers. Whole beam simulations show the dramatic difference in the propagation and break up of smoothed and aberrated beams.
Selection of Near Optimal Laser Cutting Parameters in CO2 Laser Cutting by the Taguchi Method
Directory of Open Access Journals (Sweden)
Miloš MADIĆ
2013-12-01
Full Text Available Identification of laser cutting conditions that are insensitive to parameter variations and noise is of great importance. This paper demonstrates the application of Taguchi method for optimization of surface roughness in CO2 laser cutting of stainless steel. The laser cutting experiment was planned and conducted according to the Taguchi’s experimental design using the L27 orthogonal array. Four laser cutting parameters such as laser power, cutting speed, assist gas pressure, and focus position were considered in the experiment. Using the analysis of means and analysis of variance, the significant laser cutting parameters were identified, and subsequently the optimal combination of laser cutting parameter levels was determined. The results showed that the cutting speed is the most significant parameter affecting the surface roughness whereas the influence of the assist gas pressure can be neglected. It was observed, however, that interaction effects have predominant influence over the main effects on the surface roughness.
Capotondi, Flavio; Pedersoli, Emanuele; Bencivenga, Filippo; Manfredda, Michele; Mahne, Nicola; Raimondi, Lorenzo; Svetina, Cristian; Zangrando, Marco; Demidovich, Alexander; Nikolov, Ivaylo; Danailov, Miltcho; Masciovecchio, Claudio; Kiskinova, Maya
2015-05-01
The Diffraction and Projection Imaging (DiProI) beamline at FERMI, the Elettra free-electron laser (FEL), hosts a multi-purpose station that has been opened to users since the end of 2012. This paper describes the core capabilities of the station, designed to make use of the unique features of the FERMI-FEL for performing a wide range of static and dynamic scattering experiments. The various schemes for time-resolved experiments, employing both soft X-ray FEL and seed laser IR radiation are presented by using selected recent results. The ongoing upgrade is adding a reflection geometry setup for scattering experiments, expanding the application fields by providing both high lateral and depth resolution.
Directory of Open Access Journals (Sweden)
O. N. Poklonskaya
2013-01-01
Full Text Available Results of measurements of Raman scattering at the room temperature in air in boron doped synthetic diamonds (five with boron concentrations 2·1017; 6·1017; 2·1018; 1,7·1019; 1·1020 cm–3 and one intentionally undoped are presented. The laser with wavelength 532 nm was used for Raman scattering excitation. Dependences of integral intensity and halfwidth of diamond Raman line with respect to the doping level are presented. In the geometrical optics approximation an expression for doped to undoped integral intensity ratio is obtained. Qualitative estimates of conductivity of the studied samples are conducted. The obtained results can be applied for mapping of near-surface laser radiation absorption coefficient of synthetic single crystal diamonds and for their quality control.
Raman scattering probe of ion-implanted and pulse laser annealed GaAs
Verma, Prabhat; Jain, K. P.; Abbi, S. C.
1996-04-01
We report Raman scattering studies of phosphorus-ion-implanted and subsequently pulse laser annealed (PLA) GaAs. The threshold value of implantation fluence for the disappearance of one-phonon modes in the Raman spectrum of ion-implanted GaAs sample is found to be greater than that for the two-phonon modes by an order of magnitude. The phonon correlation length decreases with increasing disorder. The lattice reconstruction process during PLA creates microcrystallites for incomplete annealing, whose sizes can be given by the phonon correlation lengths, and are found to increase with the annealing power density. The intensity ratio of the Raman spectra corresponding to the allowed longitudinal-optical (LO)-phonon mode to the forbidden transverse-optical (TO)-phonon mode, ILO/ITO, is used as a quantitative measure of crystallinity in the implantation and PLA processes. The threshold annealing power density is estimated to be 20 MW/cm2 for 70 keV phosphorus-ion-implanted GaAs at a fluence of 5×1015 ions/cm2. The localized vibrational mode of phosphorus is observed in PLA samples for fluences above 1×1015 ions/cm2.
Extreme ultraviolet resonant inelastic X-ray scattering (RIXS) at a seeded free-electron laser
Dell’Angela, M.; Hieke, F.; Malvestuto, M.; Sturari, L.; Bajt, S.; Kozhevnikov, I. V.; Ratanapreechachai, J.; Caretta, A.; Casarin, B.; Glerean, F.; Kalashnikova, A. M.; Pisarev, R. V.; Chuang, Y.-D.; Manzoni, G.; Cilento, F.; Mincigrucci, R.; Simoncig, A.; Principi, E.; Masciovecchio, C.; Raimondi, L.; Mahne, N.; Svetina, C.; Zangrando, M.; Passuello, R.; Gaio, G.; Prica, M.; Scarcia, M.; Kourousias, G.; Borghes, R.; Giannessi, L.; Wurth, W.; Parmigiani, F.
2016-12-01
In the past few years, we have been witnessing an increased interest for studying materials properties under non-equilibrium conditions. Several well established spectroscopies for experiments in the energy domain have been successfully adapted to the time domain with sub-picosecond time resolution. Here we show the realization of high resolution resonant inelastic X-ray scattering (RIXS) with a stable ultrashort X-ray source such as an externally seeded free electron laser (FEL). We have designed and constructed a RIXS experimental endstation that allowed us to successfully measure the d-d excitations in KCoF3 single crystals at the cobalt M2,3-edge at FERMI FEL (Elettra-Sincrotrone Trieste, Italy). The FEL-RIXS spectra show an excellent agreement with the ones obtained from the same samples at the MERIXS endstation of the MERLIN beamline at the Advanced Light Source storage ring (Berkeley, USA). We established experimental protocols for performing time resolved RIXS experiments at a FEL source to avoid X ray-induced sample damage, while retaining comparable acquisition time to the synchrotron based measurements. Finally, we measured and modelled the influence of the FEL mixed electromagnetic modes, also present in externally seeded FELs, and the beam transport with ~120 meV experimental resolution achieved in the presented RIXS setup.
Efficient method for scattering problems in open billiards: Theory and applications
Akguc, Gursoy B.; Seligman, Thomas H.
2006-12-01
We present an efficient method to solve scattering problems in two-dimensional open billiards with two leads and a complicated scattering region. The basic idea is to transform the scattering region to a rectangle, which will lead to complicated dynamics in the interior, but simple boundary conditions. The method can be specialized to closed billiards, and it allows the treatment of interacting particles in the billiard. We apply this method to quantum echoes measured recently in a microwave cavity, and indicate how it can be used for interacting particles.
An efficient method for scattering problems in open billiards: Theory and applications
Akguc, G B; Akguc, Gursoy B.; Seligman, Thomas H.
2006-01-01
We present an efficient method to solve scattering problems in two-dimensional open billiards with two leads and a complicated scattering region. The basic idea is to transform the scattering region to a rectangle, which will lead to complicated dynamics in the interior, but simple boundary conditions. The method can be specialized to closed billiards, and it allows the treatment of interacting particles in the billiard. We apply this method to quantum echoes measured recently in a microwave cavity, and indicate, how it can be used for interacting particles.
Finite element and finite difference methods in electromagnetic scattering
Morgan, MA
2013-01-01
This second volume in the Progress in Electromagnetic Research series examines recent advances in computational electromagnetics, with emphasis on scattering, as brought about by new formulations and algorithms which use finite element or finite difference techniques. Containing contributions by some of the world's leading experts, the papers thoroughly review and analyze this rapidly evolving area of computational electromagnetics. Covering topics ranging from the new finite-element based formulation for representing time-harmonic vector fields in 3-D inhomogeneous media using two coupled sca
Rubtsova, O A; Moro, A M
2008-01-01
The direct comparison of two different continuum discretization methods towards the solution of a composite particle scattering off a nucleus is presented. The first approach -- the Continumm-Discretized Coupled Channel method -- is based on the differential equation formalism, while the second one -- the Wave-Packet Continuum Discretization method -- uses the integral equation formulation for the composite-particle scattering problem. As benchmark calculations we have chosen the deuteron off \
Photo-transmutation of {sup 100}Mo to {sup 99}Mo with Laser-Compton Scattering Gamma-ray
Energy Technology Data Exchange (ETDEWEB)
Lee, Jiyoung; Rehman, Haseeb ur; Kim, Yonghee [KAIST, Daejeon (Korea, Republic of)
2016-10-15
This paper presents a photonuclear transmutation method using laser Compton scattering (LCS) gamma-ray beam. Potential production rate (reaction rate) of 99Mo using the photonuclear (γ,n) reaction is evaluated. Rigorous optimization of the LCS spectrum has also been performed to maximize production of the 99Mo. Cyclotron proton accelerators are used worldwide to produce many short-living medical isotopes. However, few are capable of producing Mo-99 and none are suitable for producing more than a small fraction of the required amounts. More than 90% of the world's demand of 99Mo is sourced from five nuclear reactors. Two of these reactors have already been decommissioned and the rest are more than 45 years old. Relatively short half-life of the parent 99Mo requires continuous re-supply to meet the requirements of medical industry. Therefore, there is an urgent need to produce the 99Mo and 99mTc isotopes by alternative ways. One such alternative is giant dipole resonance (GDR) based photonuclear transmutation of 100Mo to 99Mo. For 99Mo production with the LCS photons using GDR-based (γ,n) reaction, the gamma-ray energy should be around 15 MeV. This study indicates that optimization of LCS spectrum by varying the electron and laser energies within practical limits can enhance the transmutation of Mo-100 to M-99 quite significantly. It has been found that irradiation time should be rather short, e.g., less than 6 hours, to maximize the weekly production of Mo-99 in the GDR-based Mo-99 production facility using the LCS photons. The analysis shows that production of 99Mo using a high-performance LCS facility offers a potentially-promising alternative for the production of 99mTc.
Monitoring of the MBE growth processes of CdTe on InSb by laser light scattering
J. Huerta; M. López López; O. Zelaya Angel
1999-01-01
We have studied by Laser Light Scattering (LLS) the oxides surface desorption of InSb substrates, and the subsequentgrowth of CdTe layers by molecular beam epitaxy (MBE). LLS measurements allowed us to determine the criticaltemperature before surface degradation of InSb, which is not evidently noticed by reflection high energy electrondiffraction (RHEED). Surface defects appeared on substrates where this temperature was exceeded, as observed byscanning electron microscopy (SEM) and Atomic For...
Yashkir, Yu N.; Yashkir, O. V.
1991-11-01
An investigation is made of the generation of ultrashort pulses in a ring laser in the presence of intracavity nonlinear losses due to stimulated Raman scattering. A numerical analysis of the attractors of the problem is used in a study of typical lasing regimes: stable, unstable regular, and unstable irregular (optical turbulence). A change in the nonlinearity parameter reveals also "intermittence" regions. An analysis is made of the influence of feedback provided by the Stokes radiation on the localization of an instability region.
Li, Ping
2014-05-01
A scheme hybridizing discontinuous Galerkin time-domain (DGTD) and time-domain boundary integral (TDBI) methods for accurately analyzing transient electromagnetic scattering is proposed. Radiation condition is enforced using the numerical flux on the truncation boundary. The fields required by the flux are computed using the TDBI from equivalent currents introduced on a Huygens\\' surface enclosing the scatterer. The hybrid DGTDBI ensures that the radiation condition is mathematically exact and the resulting computation domain is as small as possible since the truncation boundary conforms to scatterer\\'s shape and is located very close to its surface. Locally truncated domains can also be defined around each disconnected scatterer additionally reducing the size of the overall computation domain. Numerical examples demonstrating the accuracy and versatility of the proposed method are presented. © 2014 IEEE.
System, Apparatus and Method Employing a Dual Head Laser
Coyle, Donald B. (Inventor); Stysley, Paul R. (Inventor); Poulios, Demetrios (Inventor)
2015-01-01
A system, apparatus and method employing a laser with a split-head, V-assembly gain material configuration. Additionally, the present invention is directed to techniques to better dissipate or remove unwanted energies in laser operations. The present invention is also directed to techniques for better collimated laser beams, with single spatial mode quality (TEM00), with improved efficiency, in extreme environments, such as in outer space.
Zeng, Jianhua; Chen, Lei; Dai, Qiaofeng; Lan, Sheng; Tie, Shaolong
2016-01-01
We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2-SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into ``coffee'' rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly revealed in the anti-Stokes hyper-Raman scattering. Apart from the strong anti-Stokes hyper-Raman scattering, Stokes hyper-Raman scattering with small Raman shifts was detected during the ablation process of thick MoS2 layers. It was also observed by slightly defocusing the excitation light. The detection of anti-Stokes hyper-Raman scattering may serve as a new technique for studying the Raman inactive vibration modes in nanomaterials.We proposed a scheme in which normal Raman scattering is coupled with hyper-Raman scattering for generating a strong anti-Stokes hyper-Raman scattering in nanomaterials by using femtosecond laser pulses. The proposal was experimentally demonstrated by using a single-layer MoS2 on a SiO2/Si substrate, a 17 nm-thick MoS2 on an Au/SiO2 substrate and a 9 nm-thick MoS2 on a SiO2-SnO2/Ag/SiO2 substrate which were confirmed to be highly efficient for second harmonic generation. A strong anti-Stokes hyper-Raman scattering was also observed in other nanomaterials possessing large second-order susceptibilities, such as silicon quantum dots self-assembled into ``coffee'' rings and tubular Cu-doped ZnO nanorods. In all the cases, many Raman inactive vibration modes were clearly
Membrane Characterization by Microscopic and Scattering Methods: Multiscale Structure
Directory of Open Access Journals (Sweden)
Philippe Moulin
2011-04-01
Full Text Available Several microscopic and scattering techniques at different observation scales (from atomic to macroscopic were used to characterize both surface and bulk properties of four new flat-sheet polyethersulfone (PES membranes (10, 30, 100 and 300 kDa and new 100 kDa hollow fibers (PVDF. Scanning Electron Microscopy (SEM with “in lens” detection was used to obtain information on the pore sizes of the skin layers at the atomic scale. White Light Interferometry (WLI and Atomic Force Microscopy (AFM using different scales (for WLI: windows: 900 × 900 µm2 and 360 × 360 µm2; number of points: 1024; for AFM: windows: 50 × 50 µm2 and 5 × 5 µm2; number of points: 512 showed that the membrane roughness increases markedly with the observation scale and that there is a continuity between the different scan sizes for the determination of the RMS roughness. High angular resolution ellipsometric measurements were used to obtain the signature of each cut-off and the origin of the scattering was identified as coming from the membrane bulk.
Membrane characterization by microscopic and scattering methods: multiscale structure.
Tamime, Rahma; Wyart, Yvan; Siozade, Laure; Baudin, Isabelle; Deumie, Carole; Glucina, Karl; Moulin, Philippe
2011-04-13
Several microscopic and scattering techniques at different observation scales (from atomic to macroscopic) were used to characterize both surface and bulk properties of four new flat-sheet polyethersulfone (PES) membranes (10, 30, 100 and 300 kDa) and new 100 kDa hollow fibers (PVDF). Scanning Electron Microscopy (SEM) with "in lens" detection was used to obtain information on the pore sizes of the skin layers at the atomic scale. White Light Interferometry (WLI) and Atomic Force Microscopy (AFM) using different scales (for WLI: windows: 900 × 900 µm2 and 360 × 360 µm2; number of points: 1024; for AFM: windows: 50 × 50 µm2 and 5 × 5 µm2; number of points: 512) showed that the membrane roughness increases markedly with the observation scale and that there is a continuity between the different scan sizes for the determination of the RMS roughness. High angular resolution ellipsometric measurements were used to obtain the signature of each cut-off and the origin of the scattering was identified as coming from the membrane bulk.
Schaeffer, D. B.; Constantin, C. G.; Bondarenko, A. S.; Everson, E. T.; Niemann, C.
2016-11-01
We present optical Thomson scattering results that image for the first time in a single measurement the spatial transition from collective to non-collective scattering. Data were taken in the Phoenix laser laboratory at the University of California, Los Angeles. The Raptor laser was used to ablate a carbon plasma, which was diagnosed with the frequency-doubled Phoenix laser serving as a Thomson scattering probe. Scattered light was collected from the laser plasma up to 10 cm from the target surface and up to 10 us after ablation, and imaged with high spatial and spectral resolutions. The results show a strong Thomson collective feature close to the target surface that smoothly transitions to a non-collective feature over several mm.
A simulation method for the study of laser transillumination of biological tissues.
Maarek, J M; Jarry, G; de Cosnac, B; Lansiart, A; Bui-Mong-Hung
1984-01-01
The Monte-Carlo method is employed to simulate the illumination of a blood slab by a continuous laser. It is assumed that the geometry of the medium is bidimensional and that scattering or absorption takes place only when a photon strikes a red blood cell. The parameters involved in the calculations concern the photons free path lengths between two collisions, the scattering angles and the absorption probability at collision. These parameters are assessed according to experimental or literature data. Fortran programs allow the computation of diffuse and collimated transmittances (Td and Tc, respectively), of transmittance measured with an optic fiber Tf and of reflectance R. The variations of Tc and Tf with blood thickness are in accordance with established laws. Moreover, measured and computed reflectances change with hematocrit ratio in a similar way. This work demonstrates that the Monte-Carlo method is a simple reliable tool which can be used to provide a realistic model of laser penetration in complex biological structures. Moreover, this method will permit investigations in laser tomo-spectrometry by providing a useful simulation of the interaction of ultrashort light pulses with biological media.
Li, Ping
2014-07-01
This paper presents an algorithm hybridizing discontinuous Galerkin time domain (DGTD) method and time domain boundary integral (BI) algorithm for 3-D open region electromagnetic scattering analysis. The computational domain of DGTD is rigorously truncated by analytically evaluating the incoming numerical flux from the outside of the truncation boundary through BI method based on the Huygens\\' principle. The advantages of the proposed method are that it allows the truncation boundary to be conformal to arbitrary (convex/ concave) scattering objects, well-separated scatters can be truncated by their local meshes without losing the physics (such as coupling/multiple scattering) of the problem, thus reducing the total mesh elements. Furthermore, low frequency waves can be efficiently absorbed, and the field outside the truncation domain can be conveniently calculated using the same BI formulation. Numerical examples are benchmarked to demonstrate the accuracy and versatility of the proposed method.
THE LIMITING ABSORPTION METHOD FOR A TRANSMISSION PROBLEM IN ACOUSTIC SCATTERING
Institute of Scientific and Technical Information of China (English)
Messaoud SOUILAH
2006-01-01
The limiting absorption principle is used to solve the scattering problem of time harmonic acoustic waves by penetrable objects in Sobolev spaces. The method is based on integral representation of the solution using the Green's kernel of the Helmholtz equation.
Efficient method for controlling the spatial coherence of a laser
Nixon, Micha; Friesem, Asher; Cao, Hui; Davidson, Nir
2013-01-01
An efficient method to tune the spatial coherence of a degenerate laser over a broad range with minimum variation in the total output power is presented. It is based on varying the diameter of a spatial filter inside the laser cavity. The number of lasing modes supported by the degenerate laser can be controlled from 1 to 320,000, with less than a 50% change in the total output power. We show that a degenerate laser designed for low spatial coherence can be used as an illumination source for speckle-free microscopy that is 9 orders of magnitude brighter than conventional thermal light.
Methods for Optimisation of the Laser Cutting Process
DEFF Research Database (Denmark)
Dragsted, Birgitte
This thesis deals with the adaptation and implementation of various optimisation methods, in the field of experimental design, for the laser cutting process. The problem in optimising the laser cutting process has been defined and a structure for at Decision Support System (DSS......) for the optimisation of the laser cutting process has been suggested. The DSS consists of a database with the currently used and old parameter settings. Also one of the optimisation methods has been implemented in the DSS in order to facilitate the optimisation procedure for the laser operator. The Simplex Method has...... been adapted in two versions. A qualitative one, that by comparing the laser cut items optimise the process and a quantitative one that uses a weighted quality response in order to achieve a satisfactory quality and after that maximises the cutting speed thus increasing the productivity of the process...
A Sodium laser guide star coupling efficiency measurement method
Lu, Feng; Xue, Suijian; Li, Yang-Peng; Jin, Kai; Otarola, Angel; Bo, Yong; Zuo, Jun-Wei; Bian, Qi; Wei, Kai; Hu, Jing-Yao
2016-01-01
Large telescope's adaptive optics (AO) system requires one or several bright artificial laser guide stars to improve its sky coverage. The recent advent of high power sodium laser is perfect for such application. However, besides the output power, other parameters of the laser also have significant impact on the brightness of the generated sodium laser guide star mostly in non-linear relationships. When tuning and optimizing these parameters it is necessary to tune based on a laser guide star generation performance metric. Although return photon flux is widely used, variability of atmosphere and sodium layer make it difficult to compare from site to site even within short time period for the same site. A new metric, coupling efficiency is adopted in our field tests. In this paper, we will introduce our method for measuring the coupling efficiency of a 20W class pulse sodium laser for AO application during field tests that were conducted during 2013-2015.
The Effect of Laser Treatment as a Weed Control Method
DEFF Research Database (Denmark)
Mathiassen, Solvejg K; Bak, Thomas; Christensen, Svend
2006-01-01
for weed control, however, require a systematic investigation of the relationship between energy density and the biological effect on different weed species, growth stages, etc. This paper investigates the effect of laser treatment directed towards the apical meristems of selected weed species...... chickweed), Tripleurospermum inodorum (scentless mayweed) and Brassica napus (oilseed rape). The experiment showed that laser treatment of the apical meristems caused significant growth reduction and in some cases had lethal effects on the weed species. The biological efficacy of the laser control method...... was related to wavelength, exposure time, spot size and laser power. The efficacy also varied between the weed species. The results indicate that the efficacy of laser treatments can be improved by a more precise pointing of the laser beam towards the apical meristems and optimisation of the energy density...
Stimulated Globular Scattering of Laser Radiation in Photonic Crystals: Temperature Dependences
Gorelik, V S; Tcherniega, N V; Vodchits, A I
2007-01-01
Stimulated globular scattering (SGS) characteristics (frequency shifts, threshold, conversion efficiency) have been studied in photonic crystals (synthetic opal matrices and opal nanocomposites) at different temperatures. Results have been compared with stimulated Raman scattering investigations in calcite single crystals. In both cases temperature lowering from +20 C to -196 C resulted in the stimulated scattering energy increase and its redistribution to the higher order components.
DEFF Research Database (Denmark)
Kristensen, Philip Trøst; Lodahl, Peter; Mørk, Jesper
2009-01-01
We present a multipole solution to the Lippmann-Schwinger equation for electromagnetic scattering in inhomogeneous geometries. The method is illustrated by calculating the Green’s function for a finite sized two-dimensional photonic crystal waveguide.......We present a multipole solution to the Lippmann-Schwinger equation for electromagnetic scattering in inhomogeneous geometries. The method is illustrated by calculating the Green’s function for a finite sized two-dimensional photonic crystal waveguide....
Institute of Scientific and Technical Information of China (English)
HAO Dong-shan; L(U) Jian
2005-01-01
The evolution of the electron phase orbits based on the multi-photon nonlinear Compton scattering with the high power laser-plasma is discussed by using Kroll-Morton-Rosenbluth theory. The random evolution of the un-captured electron phase orbits from periodicity to non-periodicity is found after the energy has been exchanged between the electron and photons. With the increase of the absorbed photon number n by an electron,this evolution will be more and more intense, while which is rapidly decreased with the enhancement of the collision non-flexibility ξ and their initial speeds of the electrons and photons, but this evolution is lower than that in the high power laser field. When the electrons are captured by the laser field, the evolution is finished, and the electrons will stably transport,and the photons don't provide the energy for these electrons any more.
Measuring long wavelength plasma density fluctuations by CO2 laser scattering (abstract)
Evans, D. E.
1985-05-01
Long wavelength density fluctuations can be observed by scattering even with a probe beam of much shorter wavelength provided the scattering angle is small enough. This paper is concerned with experiments in which the scattering angle is comparable with the probe beam divergence so the scattered and incident radiation never achieve spatial separation. Under these circumstances, the role of diffraction is preeminent and Fourier optics methods are used to describe the propagation of the beam, which is taken to be TEM00 mode Gaussian. Interaction between the probe beam and the plasma disturbance is described by refraction and no appeal is made to explicit scattering theory. Analysis of the effect of a monochromatic wave disturbance confined to a plane perpendicular to the probe beam (a plane grating in effect) reveals oscillations at the wave frequency induced on the probe with an intensity varying over the beam profile in a regular pattern symmetric about the beam axis. Detail of the pattern depends on the wavelength of the disturbance, its direction, and its axial position relative to a local beam waist. These oscillations are readily identified as due to radiation scattered by the plasma wave into diffraction orders, beating with the unperturbed part of the beam. Indeed, it can be shown1 that Fourier optics plus refraction produce almost the same result as conventional scattering theory,2 the small discrepancy being traceable to the neglect in the latter of incident beam wavefront curvature. The results of the two approaches coincide in the Fraunhofer limit. Computations of this sort have been confirmed by experiments using transducer-driven waves in air3 and by plasma experiments where the same regular patterns are observed from spontaneous plasma waves.4,5 Calculation suggests and experiments have demonstrated6 that additional information, such as the absolute direction of wave propagation, can be deduced from phase, measured with a multichannel detector array
Numerical simulation of bistatic scattering from fractal rough surface in the finite element method
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
By using the Monte Carlo method and numerical finite elementapproach, bistatic scattering from the fractal and Gaussian rough surfaces is studied. The difference between these two surfaces and their functional dependence on the surface parameters are discussed. Angular variation of bistatic scattering from the fractal surface is very significant, even for fairly smooth surface, whilst scattering from the Gaussian rough surface tends to the specular reflection. The slope of angular variation is linearly related with the fractal dimension. If an electrically_large target is placed over the rough surface, the fractal dimension inverted from bistatic scattering would be reduced. As the surfaces become very rough, scattering from different fractal and Gaussian surfaces would be not identified.
Laser filamentation mathematical methods and models
Lorin, Emmanuel; Moloney, Jerome
2016-01-01
This book is focused on the nonlinear theoretical and mathematical problems associated with ultrafast intense laser pulse propagation in gases and in particular, in air. With the aim of understanding the physics of filamentation in gases, solids, the atmosphere, and even biological tissue, specialists in nonlinear optics and filamentation from both physics and mathematics attempt to rigorously derive and analyze relevant non-perturbative models. Modern laser technology allows the generation of ultrafast (few cycle) laser pulses, with intensities exceeding the internal electric field in atoms and molecules (E=5x109 V/cm or intensity I = 3.5 x 1016 Watts/cm2 ). The interaction of such pulses with atoms and molecules leads to new, highly nonlinear nonperturbative regimes, where new physical phenomena, such as High Harmonic Generation (HHG), occur, and from which the shortest (attosecond - the natural time scale of the electron) pulses have been created. One of the major experimental discoveries in this nonlinear...
Huang, Wei; Yang, Limei; Lei, Lei; Li, Feng
2017-10-01
A microfluidic-based multi-angle laser scattering (MALS) system capable of acquiring scattering patterns of a single particle is designed and demonstrated. The system includes a sheathless nozzle microfluidic glass chip, and an on-chip MALS unit being in alignment with the nozzle exit in the chip. The size and relative refractive indices (RI) of polystyrene (PS) microspheres were deduced with accuracies of 60 nm and 0.002 by comparing the experimental scattering patterns with theoretical ones. We measured scattering patterns of waterborne parasites i.e., Cryptosporidium parvum (C.parvum) and Giardia lamblia (G. lamblia), and some other representative species suspended in deionized water at a maximum flow rate of 12 μL/min, and a maximum of 3000 waterborne parasites can be identified within one minute with a mean accuracy higher than 96% by classification of distinctive scattering patterns using a support-vector-machine (SVM) algorithm. The system provides a promising tool for label-free detection of waterborne parasites and other biological contaminants.
Energy Technology Data Exchange (ETDEWEB)
Blais, N.; Podgorsak, E.B. (Montreal General Hospital, PQ (Canada). Dept. of Medical Physics)
1992-10-01
A method for determining the kinetic energy of clinical electron beams is described, based on the measurement in air of the spatial spread of a pencil electron beam which is produced from the broad clinical electron beam. As predicted by the Fermi-Eyges theory, the dose distribution measured in air on a plane, perpendicular to the incident direction of the initial pencil electron beam, is Gaussian. The square of its spatial spread is related to the mass angular scattering power which in turn is related to the kinetic energy of the electron beam. The measured spatial spread may thus be used to determine the mass angular scattering power, which is then used to determine the kinetic energy of the electron beam from the known relationship between mass angular scattering power and kinetic energy. Energies obtained with the mass angular scattering power method agree with those obtained with the electron range method. (author).
Scattering cluster wave functions on the lattice using the adiabatic projection method
Rokash, Alexander; Elhatisari, Serdar; Lee, Dean; Epelbaum, Evgeny; Krebs, Hermann
2015-01-01
The adiabatic projection method is a general framework for studying scattering and reactions on the lattice. It provides a low-energy effective theory for clusters which becomes exact in the limit of large Euclidean projection time. Previous studies have used the adiabatic projection method to extract scattering phase shifts from finite periodic-box energy levels using L\\"uschers method. In this paper we demonstrate that scattering observables can be computed directly from asymptotic cluster wave functions. For a variety of examples in one and three spatial dimensions, we extract elastic phase shifts from asymptotic cluster standing waves corresponding to spherical wall boundary conditions. We find that this approach of extracting scattering wave functions from the adiabatic Hamiltonian to be less sensitive to small stochastic and systematic errors as compared with using periodic-box energy levels.
A method for determination mass absorption coefficient of gamma rays by Compton scattering.
El Abd, A
2014-12-01
A method was proposed for determination mass absorption coefficient of gamma rays for compounds, alloys and mixtures. It is based on simulating interaction processes of gamma rays with target elements having atomic numbers from Z=1 to Z=92 using the MCSHAPE software. Intensities of Compton scattered gamma rays at saturation thicknesses and at a scattering angle of 90° were calculated for incident gamma rays of different energies. The obtained results showed that the intensity of Compton scattered gamma rays at saturations and mass absorption coefficients can be described by mathematical formulas. These were used to determine mass absorption coefficients for compound, alloys and mixtures with the knowledge of their Compton scattered intensities. The method was tested by calculating mass absorption coefficients for some compounds, alloys and mixtures. There is a good agreement between obtained results and calculated ones using WinXom software. The advantages and limitations of the method were discussed.
Method of stabilizing a laser apparatus with wavelength converter
DEFF Research Database (Denmark)
2013-01-01
A method of controlling beam quality and stability of a laser apparatus, the laser apparatus comprising, a diode laser (10) providing first radiation of at least a first wavelength, and a frequency conversion unit (12) configured to frequency-convert the first radiation from the diode laser......) into the first section (222), a second contact (221) for injecting a second current (I2) into the second section (223), and means for controlling a temperature of the diode laser; wherein the method comprises monitoring a first parameter indicative of the power content of a dominant lobe of the first radiation......; iteratively determining a combination of respective values of the first current, the second current and the temperature at which combination of respective values the monitored first parameter and a stability parameter indicative of a fluctuation over time of the monitored first parameter each fulfils...
Kurata, Tomohiro; Oda, Shigeto; Kawahira, Hiroshi; Haneishi, Hideaki
2016-10-01
We have previously proposed an estimation method of intravascular oxygen saturation (SO_2) from the images obtained by sidestream dark-field (SDF) imaging (we call it SDF oximetry) and we investigated its fundamental characteristics by Monte Carlo simulation. In this paper, we propose a correction method for scattering by the tissue and performed experiments with turbid phantoms as well as Monte Carlo simulation experiments to investigate the influence of the tissue scattering in the SDF imaging. In the estimation method, we used modified extinction coefficients of hemoglobin called average extinction coefficients (AECs) to correct the influence from the bandwidth of the illumination sources, the imaging camera characteristics, and the tissue scattering. We estimate the scattering coefficient of the tissue from the maximum slope of pixel value profile along a line perpendicular to the blood vessel running direction in an SDF image and correct AECs using the scattering coefficient. To evaluate the proposed method, we developed a trial SDF probe to obtain three-band images by switching multicolor light-emitting diodes and obtained the image of turbid phantoms comprised of agar powder, fat emulsion, and bovine blood-filled glass tubes. As a result, we found that the increase of scattering by the phantom body brought about the decrease of the AECs. The experimental results showed that the use of suitable values for AECs led to more accurate SO_2 estimation. We also confirmed the validity of the proposed correction method to improve the accuracy of the SO_2 estimation.
Kurata, Tomohiro; Oda, Shigeto; Kawahira, Hiroshi; Haneishi, Hideaki
2016-12-01
We have previously proposed an estimation method of intravascular oxygen saturation (SO_2) from the images obtained by sidestream dark-field (SDF) imaging (we call it SDF oximetry) and we investigated its fundamental characteristics by Monte Carlo simulation. In this paper, we propose a correction method for scattering by the tissue and performed experiments with turbid phantoms as well as Monte Carlo simulation experiments to investigate the influence of the tissue scattering in the SDF imaging. In the estimation method, we used modified extinction coefficients of hemoglobin called average extinction coefficients (AECs) to correct the influence from the bandwidth of the illumination sources, the imaging camera characteristics, and the tissue scattering. We estimate the scattering coefficient of the tissue from the maximum slope of pixel value profile along a line perpendicular to the blood vessel running direction in an SDF image and correct AECs using the scattering coefficient. To evaluate the proposed method, we developed a trial SDF probe to obtain three-band images by switching multicolor light-emitting diodes and obtained the image of turbid phantoms comprised of agar powder, fat emulsion, and bovine blood-filled glass tubes. As a result, we found that the increase of scattering by the phantom body brought about the decrease of the AECs. The experimental results showed that the use of suitable values for AECs led to more accurate SO_2 estimation. We also confirmed the validity of the proposed correction method to improve the accuracy of the SO_2 estimation.
Energy Technology Data Exchange (ETDEWEB)
Bradley, K.S. [Univ. of California, Davis, CA (US)
1993-02-11
Despite the apparent simplicity of controlled fusion, there are many phenomena which have prevented its achievement. One phenomenon is laser-plasma instabilities. An investigation of one such instability, stimulated Brillouin scattering (SBS), is reported here. SBS is a parametric process whereby an electromagnetic wave (the parent wave) decays into another electromagnetic wave and an ion acoustic wave (the daughter waves). SBS impedes controlled fusion since it can scatter much or all of the incident laser light, resulting in poor drive symmetry and inefficient laser-plasma coupling. It is widely believed that SBS becomes convectively unstable--that is, it grows as it traverses the plasma. Though it has yet to be definitively tested, convective theory is often invoked to explain experimental observations, even when one or more of the theory`s assumptions are violated. In contrast, the experiments reported here not only obeyed the assumptions of the theory, but were also conducted in plasmas with peak densities well below quarter-critical density. This prevented other competing or coexisting phenomena from occurring, thereby providing clearly interpretable results. These are the first SBS experiments that were designed to be both a clear test of linear convective theory and pertinent to controlled fusion research. A crucial part of this series of experiments was the development of a new instrument, the Multiple Angle Time Resolving Spectrometer (MATRS). MATRS has the unique capability of both spectrally and temporally resolving absolute levels of scattered light at many angles simultaneously, and is the first of its kind used in laser-plasma experiments. A detailed comparison of the theoretical predictions and the experimental observations is made.
A new method for detecting pulse gamma ray with scattered electrons
Institute of Scientific and Technical Information of China (English)
Xia Liang-Bin; Ouyang Xiao-Ping; Wang Oun-Shu; Zang Ke-Jun; Tan Xin-Jian
2008-01-01
This paper describes a newly designed gamma pulse detector of current mode that uses the scattered electron method. Tungsten is used as the scattering target, an organic thin film scintillator ST401 is used to collect the scattered electrons. The spatial distribution of the electronic energy-flux density is studied by using the MCNP code. The optimization of the target and the thickness of the scintillator are also discussed. The results indicate that the energy response is relatively flat in the range of 0.4 to 5 MeV.
A variation iteration method for isotropic velocity-dependent potentials: Scattering case
Energy Technology Data Exchange (ETDEWEB)
Eed, H. [Applied Science Private University, Basic Science Department, Amman (Jordan)
2014-12-01
We propose a new approximation scheme to obtain analytic expressions for the Schroedinger equation with isotropic velocity-dependent potential to determine the scattering phase shift. In order to test the validity of our approach, we applied it to an exactly solvable model for nucleon-nucleon scattering. The results of the variation iteration method (VIM) formalism compare quite well with those of the exactly solvable model. The developed formalism can be applied in problems concerning pion-nucleon, nucleon-nucleon, and electron-atom scattering. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Morel, J.E.
1981-01-01
A collocation method is developed for the solution of the one-dimensional neutron transport equation in slab geometry with both symmetric and polarly asymmetric scattering. For the symmetric scattering case, it is found that the collocation method offers a combination of some of the best characteristics of the finite-element and discrete-ordinates methods. For the asymmetric scattering case, it is found that the computational cost of cross-section data processing under the collocation approach can be significantly less than that associated with the discrete-ordinates approach. A general diffusion equation treating both symmetric and asymmetric scattering is developed and used in a synthetic acceleration algorithm to accelerate the iterative convergence of collocation solutions. It is shown that a certain type of asymmetric scattering can radically alter the asymptotic behavior of the transport solution and is mathematically equivalent within the diffusion approximation to particle transport under the influence of an electric field. The method is easily extended to other geometries and higher dimensions. Applications exist in the areas of neutron transport with highly anisotropic scattering (such as that associated with hydrogenous media), charged-particle transport, and particle transport in controlled-fusion plasmas. 23 figures, 6 tables.
Scattering Cross Section of Sound Waves by the Modal Element Method
Baumeister, Kenneth J.; Kreider, Kevin L.
1994-01-01
#he modal element method has been employed to determine the scattered field from a plane acoustic wave impinging on a two dimensional body. In the modal element method, the scattering body is represented by finite elements, which are coupled to an eigenfunction expansion representing the acoustic pressure in the infinite computational domain surrounding the body. The present paper extends the previous work by developing the algorithm necessary to calculate the acoustics scattering cross section by the modal element method. The scattering cross section is the acoustical equivalent to the Radar Cross Section (RCS) in electromagnetic theory. Since the scattering cross section is evaluated at infinite distance from the body, an asymptotic approximation is used in conjunction with the standard modal element method. For validation, the scattering cross section of the rigid circular cylinder is computed for the frequency range 0.1 is less than or equal to ka is less than or equal to 100. Results show excellent agreement with the analytic solution.
Hashimoto, Hiroshi; Kim, Min-Geun; Abe, Kazuhisa; Cho, Seonho
2013-10-01
This paper presents a level set-based topology optimization method for noise barriers formed from an assembly of scatterers. The scattering obstacles are modeled by elastic bodies arranged periodically along the wall. Due to the periodicity, the problem can be reduced to that in a unit cell. The interaction between the elastic scatterers and the acoustic field is described in the context of the level set analysis. The semi-infinite acoustic wave regions located on the both sides of the barrier are represented by impedance matrices. The objective function is defined by the energy transmission passing the barrier. The design sensitivity is evaluated analytically by the aid of adjoint equations. The dependency of the optimal profile on the stiffness of scatterers and on the target frequency band is examined. The feasibility of the developed optimization method is proved through numerical examples.
Laser coagulation; Laser eye surgery; Photocoagulation; Laser photocoagulation - diabetic eye disease; Laser photocoagulation - diabetic retinopathy; Focal photocoagulation; Scatter (or pan retinal) photocoagulation; Proliferative ...
Efficient method for transport simulations in quantum cascade lasers
Directory of Open Access Journals (Sweden)
Maczka Mariusz
2017-01-01
Full Text Available An efficient method for simulating quantum transport in quantum cascade lasers is presented. The calculations are performed within a simple approximation inspired by Büttiker probes and based on a finite model for semiconductor superlattices. The formalism of non-equilibrium Green’s functions is applied to determine the selected transport parameters in a typical structure of a terahertz laser. Results were compared with those obtained for a infinite model as well as other methods described in literature.
Efficient method for transport simulations in quantum cascade lasers
Maczka, Mariusz; Pawlowski, Stanislaw
2016-12-01
An efficient method for simulating quantum transport in quantum cascade lasers is presented. The calculations are performed within a simple approximation inspired by Büttiker probes and based on a finite model for semiconductor superlattices. The formalism of non-equilibrium Green's functions is applied to determine the selected transport parameters in a typical structure of a terahertz laser. Results were compared with those obtained for a infinite model as well as other methods described in literature.
Determination of in vitro simulated blood cell velocity by laser-Doppler with state space methods.
Ledbetter-Nelepovitz, C C; Rao, B D; Fronek, A
1991-03-01
In this paper a signal processing method based on an important tool of numerical analysis, the singular value decomposition (SVD), is used. This method is applied to the unprocessed output of a Laser-Doppler fluxmeter to obtain parameters that are more sensitive to blood velocity than to hematocrit. The SVD-based method utilizes the exponential shape of the frequency spectrum of the laser light scattered from the moving red blood cells and demonstrates an inverse relationship between the damping constant beta associated with the exponential shape and the blood velocity. This method was applied to samples of rat blood of several known hematocrit values that were rotated at different velocities on a turntable. The method extracted one dominant singular value from the spectra, indicating that the spectra can be modeled as a single exponential dominated by scatterings with a single moving red blood cell. A 68% change in inverse velocity resulted in a 50% change in the damping constant (hematocrit 29.5% vol). On the other hand, a 37% change in hematocrit resulted in a far smaller change in the damping constant beta of only 17%. Analysis of the extracted parameters shows that the damping constants are far more influenced by blood velocity than by blood hematocrit.
Rebollar, Esther; Sanz, Mikel; Pérez, Susana; Hernández, Margarita; Martín-Fabiani, Ignacio; Rueda, Daniel R; Ezquerra, Tiberio A; Domingo, Concepción; Castillejo, Marta
2012-12-05
We report on the fabrication of gold coated nanostructured polymer thin films and on their characterization as substrates for surface enhanced Raman spectroscopy (SERS). Laser induced periodic surface structures (LIPSS) were obtained on thin polymer films of poly(trimethylene terephthalate) (PTT) upon laser irradiation with the fourth harmonic of a Nd:YAG laser (266 nm, pulse duration 6 ns) resulting in a period close to the incident wavelength. The nanostructured polymer substrates were coated with a nanoparticle assembled gold layer by pulsed laser deposition using the fifth harmonic of a Nd:YAG laser (213 nm, pulse duration 15 ns). Different deposition times resulted in thicknesses from a few nanometres up to several tens of nanometres. Analysis by atomic force microscopy and grazing incident small angle X-ray scattering showed that gold coating preserved the LIPSS relief. The capabilities of the produced nanostructures as substrates for SERS have been investigated using benzenethiol as a test molecule. The SERS signal is substantially larger than that observed for a gold-coated flat substrate. Advantages of this new type of SERS substrates are discussed.
MRFD Method for Scattering From Three Dimensional Dielectric Bodies
Directory of Open Access Journals (Sweden)
A. F. Yagli
2011-09-01
Full Text Available A three-dimensional multiresolution frequency domain (MRFD method is established to compute bistatic radar cross sections of arbitrarily shaped dielectric objects. The proposed formulation is successfully verified by computing the bistatic radar cross sections of a dielectric sphere and a dielectric cube. Comparing the results to those obtained from the finite difference frequency domain (FDFD method simulations and analytic calculations, we demonstrated the computational time and memory advantages of MRFD method.
Lechleiter, Armin; Nguyen, Dinh Liem
2010-01-01
Scattering of acoustic waves from an inhomogeneous medium can be described by the Lippmann-Schwinger integral equation. For scattering problems in free space, Vainikko proposed a fast spectral solution method that exploits the convolution structure of this equation's integral operator by using the fast Fourier transform. In a planar 3--dimensional waveguide, the integral operator of the Lippmann-Schwinger integral equation fails to be a convolution. In this paper, we show that the separable s...
Method for fast computation of angular light scattering spectra from 2D periodic arrays
Pomplun, J; Zschiedrich, L; Gutsche, P; Schmidt, F
2016-01-01
An efficient numerical method for computing angle-resolved light scattering off periodic arrays is presented. The method combines finite-element discretization with a Schur complement solver. A significant speed-up of the computations in comparison to standard finite-element method computations is observed.
A Convergent Method of Auxiliary Sources for Two-Dimensional Impedance Scatterers With Edges
DEFF Research Database (Denmark)
Karamehmedovic, Mirza; Breinbjerg, Olav
2001-01-01
A modification to the Method of Auxiliary Sources (MAS) is introduced which renders the method operational for two-dimensional impedance scatterers with edges. The modification consists in letting the auxiliary surface converge to the scatterer physical surface for increasing number of auxiliary...... sources, whereby MAS approaches a surface integral equation (IE) method. Hereby, a systematic procedure for selecting the number and locations of the auxiliary sources is provided, and convergence of numerical results is obtained. The new method resulting from this modification thus combines the desirable...
Self-seeded single-frequency laser peening method
Dane, C. Brent; Hackel, Lloyd; Harris, Fritz B.
2009-08-11
A method of operating a laser to obtain an output pulse having a single wavelength, comprises inducing an intracavity loss into a laser resonator having an amount that prevents oscillation during a time that energy from the pump source is being stored in the gain medium. Gain is built up in the gain medium with energy from the pump source until formation of a single-frequency relaxation oscillation pulse in the resonator. Upon detection of the onset of the relaxation oscillation pulse, the intracavity loss is reduced, such as by Q-switching, so that the built-up gain stored in the gain medium is output from the resonator in the form of an output pulse at a single frequency. An electronically controllable output coupler is controlled to affect output pulse characteristics. The laser acts a master oscillator in a master oscillator power amplifier configuration. The laser is used for laser peening.
Luo, W; Yu, T P; Chen, M; Song, Y M; Zhu, Z C; Ma, Y Y; Zhuo, H B
2014-12-29
Generation of attosecond x-ray pulse attracts more and more attention within the advanced light source user community due to its potentially wide applications. Here we propose an all-optical scheme to generate bright, attosecond hard x-ray pulse trains by Thomson backscattering of similarly structured electron beams produced in a vacuum channel by a tightly focused laser pulse. Design parameters for a proof-of-concept experiment are presented and demonstrated by using a particle-in-cell code and a four-dimensional laser-Compton scattering simulation code to model both the laser-based electron acceleration and Thomson scattering processes. Trains of 200 attosecond duration hard x-ray pulses holding stable longitudinal spacing with photon energies approaching 50 keV and maximum achievable peak brightness up to 1020 photons/s/mm2/mrad2/0.1%BW for each micro-bunch are observed. The suggested physical scheme for attosecond x-ray pulse trains generation may directly access the fastest time scales relevant to electron dynamics in atoms, molecules and materials.
Lasing behavior in a liquid spherical dye laser containing highly scattering nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Taniguchi, H.; Nishiya, M.; Tanosaki, S. [Department of Electrical and Electronic Engineering, Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020 (Japan); Inaba, H. [Department of Electronics, Tohoku Institute of Technology, 35-1 Yagiyama, Kasumi-Cho, Taikaku-Ku, Sendai 982 (Japan)
1996-02-01
With the addition of scattering nanoparticles to dye-doped spherical droplets, lasing has been observed with well-defined thresholds in input{endash}output data. One-order or more magnitude enhancement of peak intensity from droplet emission has been obtained with certain (optimum) additive scattering particles compared with nonadditive scattering particles (neat dye-doped droplets). Characteristics of input{endash}output intensities, emission spectra (with wavelength shifts), and spectral linewidths are reported experimentally, depending on additive quantities of scattering nanoparticles. {copyright} {ital 1996 Optical Society of America.}
Analysis of Light Scattering by Nanoobjects on a Plane Surface via Discrete Sources Method
Eremina, Elena; Eremin, Yuri; Wriedt, Thomas
2012-12-01
In the last years light scattering by nanostructures is of interest in different areas of science and technology. Analysis of light scattered by nanostructures is an effective tool for a better understanding of their properties. In this work the Discrete Sources Method (DSM) is applied to model light scattering by nanoparticles on a surface. One of attractive features of the DSM is an ability to account for all the features of the modeled system, such as complex refractive index with frequency dispersion of particles and a substrate, scattering interaction of particle and an interface. To demonstrate the variety of possible applications for the DSM, we concentrated on two practical applications. First is light scattering by a nanorod on a surface, which requires the use of a general 3D version of the DSM. The second case discussed in this chapter is light scattering by a nanoshell, which allows the accounting for the axial symmetry of the problem and essential reduction of calculation time. In both cases light scattering characteristics and their dependence on nanostructure characteristics like size, symmetry, incident angle, particle orientation, refractive index and wavelength are analyzed and discussed.
Institute of Scientific and Technical Information of China (English)
Ren Xin-Cheng; Guo Li-Xin
2008-01-01
Electromagnetic scattering from a rough surface of layered medium is investigated, and the formulae of the scattering coefficients for different polarizations are derived using the small perturbation method. A rough surface with exponential correlation function is presented for describing a rough soil surface of layered medium, the formula of its scattering coefficient is derived by considering the spectrum of the rough surface with exponential correlation function; the curves of the bistatic scattering coefficient of HH polarization with variation of the scattering angle are obtained by numerical calculation. The influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the roughness surface parameters and the frequency of the incident wave on the bistatic scattering coefficient is discussed. Numerical results show that the influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the rms and the correlation length of the rough surface, and the frequency of the incident wave on the bistatic scattering coefficient is very complex.
Testing relativity again, laser, laser, laser, laser
Einstein, A.
2015-01-01
laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser, laser,
The Application of Improved Periodic Method for Scattering
Institute of Scientific and Technical Information of China (English)
SHAWei; WUXianliang; CHENMingsheng; SUNYufa
2005-01-01
Periodic Wavelets have found some applications to Method of moments (MoM) for Computational Electromagnetics. An improved method based on Fast Fourier transform (FFT) algorithm and Physical optics (PO) theory is presented in this paper. Through eliminating some superfluous periodic wavelet-basis functions,the dimensions and condition number of impedance matrix are reduced remarkably, thus makes fast and stable computation. Besides, speedy matrix filling and efficient matrix inversion also get desirable numerical results.
LASER METHODS IN MEDICINE: Light absorption in blood during low-intensity laser irradiation of skin
Barun, V. V.; Ivanov, A. P.
2010-06-01
An analytical procedure is proposed for describing optical fields in biological tissues inhomogeneous in the depth direction, such as human skin, with allowance for multiple scattering. The procedure is used to investigate the depth distribution of the optical power density in homogeneous and multilayer dermis when the skin is exposed to a laser beam. We calculate the absorbed laser power spectra for oxy- and deoxyhaemoglobin at different depths in relation to the absorption selectivity of these haemoglobin derivatives and the spectral dependence of the optical power density and demonstrate that the spectra vary considerably with depth. A simple exponential approximation is proposed for the depth distribution of the power density in the epidermis and dermis.
Solodov, Andrei; Malkin, Vladimir; Fisch, Nathaniel
2003-10-01
In backward Raman amplifiers (BRA), the pump laser pulse can be prematurely depleted through Raman scattering, seeded by the plasma noise, as the pump encounters plasma before reaching the counter-propagating seed pulse. It was shown previously that detuning of the Raman resonance, either by a plasma density gradient or a pump frequency chirp, can prevent the premature pump backscattering, even while the desired amplification of the seed pulse persists with a high efficiency. However, parasitic pump side-scattering is not automatically suppressed together with the parasitic backscattering, and might be even more dangerous for BRA. What we show here is that by combining the above two detuning mechanisms one can suppress parasitic pump side-scattering as well. Apart from the simplest counterpropagating geometry, we examine BRA for arbitrary angles between the directions of pump and seed propagation. We show that, by selecting an appropriate direction of the plasma density gradient, one can favorably minimize the detuning in the direction of the seed pulse propagation, while strongly suppressing the parasitic pump side-scattering in all the other directions. This work was supported in part by DOE and DARPA.
Energy Technology Data Exchange (ETDEWEB)
Jacobson, C. M., E-mail: cjacobson@wisc.edu; Borchardt, M. T.; Den Hartog, D. J.; Falkowski, A. F.; Morton, L. A.; Thomas, M. A. [Department of Physics, University of Wisconsin–Madison, 1150 University Avenue, Madison, Wisconsin 53706 (United States)
2016-11-15
The Thomson scattering diagnostic on the Madison Symmetric Torus (MST) records excessive levels of stray Nd:YAG laser light. Stray light saturates the 1064 nm spectral channel in all polychromators, which prevents absolute electron density measurements via Rayleigh scattering calibration. Furthermore, stray light contaminates adjacent spectral channels for r/a ≥ 0.75, which renders the diagnostic unable to make electron temperature measurements at these radii. In situ measurements of stray light levels during a vacuum vessel vent are used to identify stray light sources and strategies for reduction of stray light levels. Numerical modeling using Zemax OpticStudio supports these measurements. The model of the vacuum vessel and diagnostic includes synthetic collection optics to enable direct comparison of measured and simulated stray light levels. Modeling produces qualitatively similar stray light distributions to MST measurements, and quantifies the mitigation effects of stray light mitigation strategies prior to implementation.
Jacobson, C. M.; Borchardt, M. T.; Den Hartog, D. J.; Falkowski, A. F.; Morton, L. A.; Thomas, M. A.
2016-11-01
The Thomson scattering diagnostic on the Madison Symmetric Torus (MST) records excessive levels of stray Nd:YAG laser light. Stray light saturates the 1064 nm spectral channel in all polychromators, which prevents absolute electron density measurements via Rayleigh scattering calibration. Furthermore, stray light contaminates adjacent spectral channels for r/a ≥ 0.75, which renders the diagnostic unable to make electron temperature measurements at these radii. In situ measurements of stray light levels during a vacuum vessel vent are used to identify stray light sources and strategies for reduction of stray light levels. Numerical modeling using Zemax OpticStudio supports these measurements. The model of the vacuum vessel and diagnostic includes synthetic collection optics to enable direct comparison of measured and simulated stray light levels. Modeling produces qualitatively similar stray light distributions to MST measurements, and quantifies the mitigation effects of stray light mitigation strategies prior to implementation.
Application of the complex scaling method in solving three-body Coulomb scattering problem
Lazauskas, R.
2017-03-01
The three-body scattering problem in Coulombic systems is a widespread, yet unresolved problem using the mathematically rigorous methods. In this work this long-term challenge has been undertaken by combining distorted waves and Faddeev–Merkuriev equation formalisms in conjunction with the complex scaling technique to overcome the difficulties related with the boundary conditions. Unlike the common belief, it is demonstrated that the smooth complex scaling method can be applied to solve the three-body Coulomb scattering problem in a wide energy region, including the fully elastic domain and extending to the energies well beyond the atom ionization threshold. A newly developed method is used to study electron scattering on the ground states of hydrogen and positronium atoms as well as a {e}++{{H}}({n}=1)\\rightleftarrows {{p}}+{Ps}({n}=1) reaction. Where available, obtained results are compared with the experimental data and theoretical predictions, proving the accuracy and efficiency of the newly developed method.
Efficient methods to model the scattering of ultrasonic guided waves in 3D
Moreau, L.; Velichko, A.; Wilcox, P. D.
2010-03-01
The propagation of ultrasonic guided waves and their interaction with a defect is of interest to the nondestructive testing community. There is no general solution to the scattering problem and it is still an ongoing research topic. Due to the complexity of guided wave scattering problems, most existing models are related to the 2D case. However, thanks to the increase in computer calculation power, specific 3D problems can also be studied, with the help of numerical or semi-analytical methods. This paper describes two efficient methods aimed at modeling 3D scattering problems. The first method is the use of the Huygens' principle to reduce the size of finite element models. This principle allows the area of interest to be restricted to the very near field of the defect, for both the generation of the incident field and the modal decomposition of the scattered field. The second method consists of separating the 3D problem into two 2D problems for which the solutions are calculated and used to approximate the 3D solution. This can be used at low frequency-thickness products, where Lamb waves have a similar behavior to bulk waves. These two methods are presented briefly and compared on simple scattering cases.
A new method for calculating the scattered field by an arbitrary cross-sectional conducting cylinder
Ragheb, Hassan A.
2011-04-01
Scattering of a plane electromagnetic wave by an arbitrary cross-sectional perfectly conducting cylinder must be performed numerically. This article aims to present a new approach for addressing this problem, which is based on simulating the arbitrary cross-sectional perfectly conducting cylinder by perfectly conducting strips of narrow width. The problem is then turned out to calculate the scattered electromagnetic field from N conducting strips. The technique of solving such a problem uses an asymptotic method. This method is based on an approximate technique introduced by Karp and Russek (Karp, S.N., and Russek, A. (1956), 'Diffraction by a Wide Slit', Journal of Applied Physics, 27, 886-894.) for solving scattering by wide slit. The method is applied here for calculating the scattered field in the far zone for E-polarised incident waves (transverse magnetic (TM) with respect to z-axis) on a perfectly conducting cylinder with arbitrary cross-section. Numerical examples are introduced first for comparison to show the accuracy of the method. Other examples for well-known scattering by conducting cylinders are then introduced followed by new examples which can only be solved by numerical methods.
Bruining, J.; Fijnaut, H.M.
We have obtained a rotational diffusion coefficient of the 70S ribosome isolated from Escherichia-coli (MRE-600), from the depolarized light scattering spectrum measured by photon correlation spectroscopy. The intensity correlation function of depolarized scattered light contains contributions due
Bruining, J.; Fijnaut, H.M.
1975-01-01
We have obtained a rotational diffusion coefficient of the 70S ribosome isolated from Escherichia-coli (MRE-600), from the depolarized light scattering spectrum measured by photon correlation spectroscopy. The intensity correlation function of depolarized scattered light contains contributions due t
Separable approximation method for two-body relativistic scattering
Energy Technology Data Exchange (ETDEWEB)
Tandy, P.C.; Thaler, R.M.
1988-03-01
A method for defining a separable approximation to a given interaction within a two-body relativistic equation, such as the Bethe-Salpeter equation, is presented. The rank-N separable representation given here permits exact reproduction of the T matrix on the mass shell and half off the mass shell at N selected bound state and/or continuum values of the invariant mass. The method employed is a four-space generalization of the separable representation developed for Schroedinger interactions by Ernst, Shakin, and Thaler, supplemented by procedures for dealing with the relativistic spin structure in the case of Dirac particles.
Separable approximation method for two-body relativistic scattering
Tandy, P. C.; Thaler, R. M.
1988-03-01
A method for defining a separable approximation to a given interaction within a two-body relativistic equation, such as the Bethe-Salpeter equation, is presented. The rank-N separable representation given here permits exact reproduction of the T matrix on the mass shell and half off the mass shell at N selected bound state and/or continuum values of the invariant mass. The method employed is a four-space generalization of the separable representation developed for Schrödinger interactions by Ernst, Shakin, and Thaler, supplemented by procedures for dealing with the relativistic spin structure in the case of Dirac particles.
Method for partially coating laser diode facets
Dholakia, Anil R. (Inventor)
1990-01-01
Bars of integral laser diode devices cleaved from a wafer are placed with their p regions abutting and n regions abutting. A thin BeCu mask having alternate openings and strips of the same width as the end facets is used to mask the n region interfaces so that multiple bars can be partially coated over their exposed p regions with a reflective or partial reflective coating. The partial coating permits identification of the emitting facet from the fully coated back facet during a later device mounting procedure.
Splines and the Galerkin method for solving the integral equations of scattering theory
Brannigan, M.; Eyre, D.
1983-06-01
This paper investigates the Galerkin method with cubic B-spline approximants to solve singular integral equations that arise in scattering theory. We stress the relationship between the Galerkin and collocation methods.The error bound for cubic spline approximates has a convergence rate of O(h4), where h is the mesh spacing. We test the utility of the Galerkin method by solving both two- and three-body problems. We demonstrate, by solving the Amado-Lovelace equation for a system of three identical bosons, that our numerical treatment of the scattering problem is both efficient and accurate for small linear systems.
A new method for calculating the Glauber multiple scattering amplitude of composite particles
Zhang, Yu-Shun; Hu, Su-Fen; Yang, Chao-Yun; Liu, Ji-Feng
1997-11-01
The method for calculating the scattering of composite particles with several kinds of constituent is studied. The formulae are derived and the method for sorting all Glauber expansion terms into several classes is given. The method of the integration is different from that of Lin and co-workers (Lin Z J et al 1991 J. Phys. G: Nucl. Part. Phys. 17 1159) and its analytical expressions are introduced. We calculate the D - D, P - P, P - 0954-3899/23/11/005/img7 and 0954-3899/23/11/005/img8 - P elastic scatterings. These results are compared with the data.
Energy Technology Data Exchange (ETDEWEB)
Jing, Yuting; Wang, Huanwen; Chen, Xiao [Department of Chemistry, Tongji University, Shanghai 200092 (China); Wang, Xuefeng, E-mail: xfwang@tongji.edu.cn [Department of Chemistry, Tongji University, Shanghai 200092 (China); Wei, Huige [Integrated Composites Laboratory (ICL), Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710 (United States); Guo, Zhanhu, E-mail: zhanhu.guo@lamar.edu [Integrated Composites Laboratory (ICL), Dan F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710 (United States)
2014-10-15
Highlights: • Silver nanoparticles (NPs) were deposited on nickel hydroxide nanosheet (NS) arrays by pulsed laser deposition (PLD) for surface-enhanced Raman scattering (SERS) spectroscopy. • The Ag/Ni(OH){sub 2} composite film exhibits very high Raman scattering enhancement ability, possessing an enhancement factor as high as 5 × 10{sup 6}. • The enhancement ability of the substrate was strongly dependent on the size and interparticle gap of Ag NPs. • The 3D structure of Ni(OH){sub 2} NS arrays and the charge transfer of Ag NPs may be responsible for this high sensitivity Raman phenomenon. - Abstract: In the present work, silver nanoparticles (NPs) were deposited on nickel hydroxide nanosheet (NS) arrays by pulsed laser deposition (PLD) for surface-enhanced Raman scattering (SERS) spectroscopy. The effective high specific surface area with silver NPs decorated on the NS arrays was revealed by field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The microstructure and optical property of this three-dimensional (3D) substrate were investigated by X-ray diffraction (XRD) and UV–vis spectra, respectively. Using rhodamine 6G (R6G) as probe molecules with the concentration down to 10{sup −5} M, the Ag/Ni(OH){sub 2} composite film exhibits very high Raman scattering enhancement ability, possessing an enhancement factor as high as 5 × 10{sup 6}. It has been found that the enhancement ability of the substrate was strongly dependent on the size and interparticle gap of Ag NPs rather than the testing position on the film surface. In addition, the 3D structure of Ni(OH){sub 2} NS arrays and the charge transfer of Ag NPs may be responsible for this high sensitivity Raman phenomenon.
Method and apparatus for laser scribing glass sheet substrate coatings
Energy Technology Data Exchange (ETDEWEB)
Borgeson, Frank A.; Hanak, Joseph J.; Harju, Ricky S.; Helman, Norman L.; Hecht, Kenneth R.
2003-05-06
A method and apparatus (42) for laser scribing coatings on glass sheet substrates by conveying the substrate adjacent a laser source (83) that provides a pulsed laser beam (84) with a wavelength at a near-infrared fundamental frequency and having a frequency in the range of 50 to 100 kilohertz and a pulse duration in the range of 8 to 70 nanoseconds, and by reflecting the beam by an XYZ galvanometer controlled mirror system (90) toward an uncoated surface of the substrate for passage therethrough to the coating on the other surface to provide overlapping ablations through the coating and scribing at a speed of at least 1000 millimeters per second.
Method and apparatus for laser scribing glass sheet substrate coatings
Energy Technology Data Exchange (ETDEWEB)
Borgeson, Frank A.; Hanak, Joseph J.; Harju, Ricky S.; Harju, Karen M.; Helman, Norman L.; Hecht, Kenneth R.
2005-07-19
A method and apparatus (42) for laser scribing coatings on glass sheet substrates by conveying the substrate adjacent a laser source (83) that provides a pulsed laser beam (84) with a wavelength at a near-infrared fundamental frequency and having a frequency in the range of 50 to 100 kilohertz and a pulse duration in the range of 8 to 70 nanoseconds, and by reflecting the beam by an XYZ galvanometer controlled mirror system (90) toward an uncoated surface of the substrate for passage therethrough to the coating on the other surface to provide overlapping ablations through the coating and scribing at a speed of at least 1000 millimeters per second.
A method of manufacturing graduated substrates for a semiconductor laser
Energy Technology Data Exchange (ETDEWEB)
Yosikava, A.; Kadzumura, K.; Ota, K.; Sugino, T.; Vada, M.
1984-01-12
A method is patented for manufacturing a substrate with a graduated design for a semiconductor laser with a long service life and the necessary optical characteristics in a 1.5 micrometer spectral range. The laser is manufactured using a GaAs substrate with an active zone based on GaxAll-xAs. In order to achieve this goal, the active layer is equipped with a so called diffusion window whose diameter is chosen so that the threshold pumping current of the laser is less than 30 milliamperes.
Meinders, Melanie
2015-01-01
Inelastic back-scattering of stray light is a long-standing problem in high-sensitivity interferometric measurements and a potential limitation for advanced gravitational-wave detectors, in particular at sub-audio-band frequencies. The emerging parasitic interferences cannot be distinguished from a scientific signal via conventional single readout. In this work, we propose and demonstrate the subtraction of inelastic back-scatter signals by employing dual homodyne detection on the output light -- here -- of a table-top Michelson interferometer. The additional readout contains solely parasitic signals and is used to model the scatter source. Subtraction of the scatter signal reduces the noise spectral density and thus improves the measurement sensitivity. Our scheme is qualitatively different from the previously demonstrated vetoing of scatter signals and opens a new path for improving the sensitivity of future gravitational-wave detectors.
Kneipp, Janina; Li, Xiangting; Sherwood, Margaret; Panne, Ulrich; Kneipp, Harald; Stockman, Mark I; Kneipp, Katrin
2008-06-01
Nanoaggregates formed by metal spheres of different radii and interparticle distances represent finite, deterministic, self-similar systems that efficiently concentrate optical fields and act as "nanolenses". Here we verify experimentally the theoretical concept of nanolenses and explore their potential as enhancing nanostructures in surface enhanced Raman scattering (SERS). Self-similar structures formed by gold nanospheres of different sizes are generated by laser ablation from solid gold into water. These nanolenses exhibit SERS enhancement factors on the order of 10(9). The "chemically clean" preparation process provides several advantages over chemically prepared nanoaggregates and makes the stable and biocompatible gold nanolenses potent enhancing structures for various analytical and sensing applications.
Petrillo, V.; Chaikovska, I.; Ronsivalle, C.; Rossi, A. R.; Serafini, L.; Vaccarezza, C.
2013-01-01
We analyze the energy distribution of a relativistic electron beam after the Compton back-scattering by a counterpropagating laser field. The analysis is performed for parameters in the range of realistic X-γ sources, in the framework of the Quantum Electrodynamics, by means of the code CAIN. The results lead to the conclusion that, in the regime considered, the main effect is the initial formation of stripes, followed by the diffusion of the most energetic particles toward lower values in the longitudinal phase space, with a final increase of the electron energy bandwidth.
Liu, Jun; Zhang, Jun; Kobayashi, Takayoshi
2008-07-01
As broad as 12000 cm(-1) coherent anti-Stokes Raman scattering (CARS) light from ultraviolet to infrared was generated in a BBO crystal by using two crossing femtosecond laser pulses with 30% conversion efficiency. More than fifteenth-order anti-Stokes and second-order Stokes Raman sidebands were observed with nice Gaussian spatial mode. The effect of the crossing angle between two input beams on the spectrum and emitting angle of the Raman sidebands was studied in detail. Calculation shows that the phase-matching condition determines the frequencies and angles of the sidebands.
A setup for resonant inelastic soft x-ray scattering on liquids at free electron laser light sources
Energy Technology Data Exchange (ETDEWEB)
Kunnus, Kristjan; Schreck, Simon; Foehlisch, Alexander [Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Institut fuer Physik und Astronomie, Universitaet Potsdam, Karl-Liebknecht-Strasse 24/25, 14476 Potsdam (Germany); Rajkovic, Ivan; Quevedo, Wilson; Gruebel, Sebastian; Scholz, Mirko [IFG Structural Dynamics of (Bio)chemical Systems, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37070 Goettingen (Germany); Eckert, Sebastian; Beye, Martin; Suljoti, Edlira; Weniger, Christian; Wernet, Philippe [Institute for Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Kalus, Christian [Abteilung Betrieb Beschleuniger BESSYII, Helmholtz-Zentrum Berlin GmbH, Albert-Einstein-Strasse 15, 12489 Berlin (Germany); Nordlund, Dennis [Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Zhang, Wenkai; Hartsock, Robert W.; Gaffney, Kelly J. [PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Schlotter, William F.; Turner, Joshua J. [Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Kennedy, Brian [MAX-lab, PO Box 118, 221 00 Lund (Sweden); and others
2012-12-15
We present a flexible and compact experimental setup that combines an in vacuum liquid jet with an x-ray emission spectrometer to enable static and femtosecond time-resolved resonant inelastic soft x-ray scattering (RIXS) measurements from liquids at free electron laser (FEL) light sources. We demonstrate the feasibility of this type of experiments with the measurements performed at the Linac Coherent Light Source FEL facility. At the FEL we observed changes in the RIXS spectra at high peak fluences which currently sets a limit to maximum attainable count rate at FELs. The setup presented here opens up new possibilities to study the structure and dynamics in liquids.
Ferrari, Eugenio; Spezzani, Carlo; Fortuna, Franck; Delaunay, Renaud; Vidal, Franck; Nikolov, Ivaylo; Cinquegrana, Paolo; Diviacco, Bruno; Gauthier, David; Penco, Giuseppe; Ribič, Primož Rebernik; Roussel, Eleonore; Trovò, Marco; Moussy, Jean-Baptiste; Pincelli, Tommaso; Lounis, Lounès; Manfredda, Michele; Pedersoli, Emanuele; Capotondi, Flavio; Svetina, Cristian; Mahne, Nicola; Zangrando, Marco; Raimondi, Lorenzo; Demidovich, Alexander; Giannessi, Luca; De Ninno, Giovanni; Danailov, Miltcho Boyanov; Allaria, Enrico; Sacchi, Maurizio
2016-01-13
The advent of free-electron laser (FEL) sources delivering two synchronized pulses of different wavelengths (or colours) has made available a whole range of novel pump-probe experiments. This communication describes a major step forward using a new configuration of the FERMI FEL-seeded source to deliver two pulses with different wavelengths, each tunable independently over a broad spectral range with adjustable time delay. The FEL scheme makes use of two seed laser beams of different wavelengths and of a split radiator section to generate two extreme ultraviolet pulses from distinct portions of the same electron bunch. The tunability range of this new two-colour source meets the requirements of double-resonant FEL pump/FEL probe time-resolved studies. We demonstrate its performance in a proof-of-principle magnetic scattering experiment in Fe-Ni compounds, by tuning the FEL wavelengths to the Fe and Ni 3p resonances.
Bai, Zhenxu; Wang, Yulei; Lu, Zhiwei; Jiang, Li; Yuan, Hang; Liu, Zhaohong
2017-08-01
A hundred picosecond ultraviolet (UV) laser is demonstrated with a pulse duration of less than 200 ps and peak power of 0.6 GW. With a hundred picosecond stimulated Brillouin scattering compressed pulse as the fundamental light, the UV output at 355 nm is obtained by extra-cavity sum-frequency-mixing in two LiB3O5 crystals. Maximum UV energy was 100 mJ when the incident energy was 280 mJ, yielding an optical-to-optical efficiency of 35.7%. This result is of interest for the generation of high energy sub-nanosecond UV lasers which finds applications in shock ignition and industrial processing.
Operation and beam profiling of an up to 200 kHz pulse-burst laser for Thomson scattering
Energy Technology Data Exchange (ETDEWEB)
Young, W. C., E-mail: wcyoung2@wisc.edu; Den Hartog, D. J. [Department of Physics, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States)
2014-11-15
A new, high-repetition rate laser is in development for use on the Thomson scattering diagnostic on the Madison Symmetric Torus. The laser has been tested at a rate of 200 kHz in a pulse-burst operation, producing bursts of 5 pulses above 1.5 J each, while capable of bursts of 17 pulses at 100 kHz. A master oscillator-power amplifier architecture is used with a Nd:YVO{sub 4} oscillator, four Nd:YAG amplifiers, and a Nd:glass amplifier. A radial profile over the pulse sequence is measured by using a set of graphite apertures and an energy meter, showing a change in beam quality over a pulsing sequence.
Energy Technology Data Exchange (ETDEWEB)
Hack, Szabolcs [ELI-ALPS, ELI-HU Non-Profit Ltd., Dugonics tér 13, H-6720 Szeged (Hungary); Department of Theoretical Physics, University of Szeged, Tisza L. krt. 84-86, H-6720 Szeged (Hungary); Varró, Sándor [ELI-ALPS, ELI-HU Non-Profit Ltd., Dugonics tér 13, H-6720 Szeged (Hungary); Wigner Research Center for Physics, SZFI, PO Box 49, H-1525 Budapest (Hungary); Czirják, Attila [ELI-ALPS, ELI-HU Non-Profit Ltd., Dugonics tér 13, H-6720 Szeged (Hungary); Department of Theoretical Physics, University of Szeged, Tisza L. krt. 84-86, H-6720 Szeged (Hungary)
2016-02-15
We investigate nonlinear Thomson scattering as a source of high-order harmonic radiation with the potential to enable attosecond light pulse generation. We present a new analytic solution of the electron’s relativistic equations of motion in the case of a short laser pulse with a sine-squared envelope. Based on the single electron emission, we compute and analyze the radiated amplitude and phase spectrum for a realistic electron bunch, with special attention to the correct initial values. These results show that the radiation spectrum of an electron bunch in head-on collision with a sufficiently strong laser pulse of sine-squared envelope has a smooth frequency dependence to allow for the synthesis of attosecond light pulses.
Wave Scattering in Heterogeneous Media using the Finite Element Method
2016-10-21
impose absorbing boundary conditions. A Rayleigh-Ritz approximation has been developed to obtain the depth eigensolution. The depth modes have a...several absorbing or nonreflecting boundary condition have been developed . In the present study, following Fix and Marin (1978) and Vendhan et. al...propagation. The two well-known methods that have been developed to study acoustic waves in depth dependent waveguides are the fast-field technique and the
Kim, Haemin; Kang, Jeeun; Chang, Jin Ho
2014-05-01
Photothermal therapy is performed by delivering laser radiation into the target lesion containing tissue chromophores so as to induce localized heating. For high treatment efficacy, the laser wavelength should be selected to maximize the absorption of incident laser radiation in the tissue chromophores. However, even with the optimal laser wavelength, both the absorption and the scattering of laser energy in tissue openly hamper treatment efficacy in deep-lying lesions. To overcome the limitation, we propose a dual thermal therapeutic method in which both laser and acoustic energies are transmitted to increase therapeutic depth while maintaining high target selectivity of photothermal therapy. Through skin-mimicking phantom experiments, it was verified that the two different energies are complementary in elevation of tissue temperature, and the treatment depth using laser radiation is increased along with acoustic energy.
The phase-functions method and full cross-section of nucleon-nucleon scattering
Zhaba, V I
2016-01-01
For calculation of the single-channel nucleon-nucleon scattering a phase-functions method has been considered. Using a phase-functions method the following phase shifts of a nucleon-nucleon scattering are calculated numerically: nn (1S0-, 3P0-, 3P1-, 1D2-, 3F3- state), pp (1S0-, 3P0-, 3P1-, 1D2- state) and np (1S0-, 1P1-, 3P0-, 3P1-, 1D2-, 3D2- state). The calculations has been performed using realistic nucleon-nucleon potentials Nijmegen groups (NijmI, NijmII, Reid93) and potential Argonne v18. Obtained phase shifts are in good agreement with the results obtained in the framework of other methods. Using the obtained phase shifts we have calculated the full cross-section. Our results are in good agreement with those obtained by using known phases published in literature. The odds between calculations depending on a computational method of phases of scattering makes: 0,2-6,3% for pp- and 0,1-5,3% for np- scatterings (NijmI, NijmII), 0,1-4,1% for pp- and 0,1-0,4% for np- scatterings (Reid93), no more than 4,5% ...
Andriyash, I A; Malka, V; d'Humières, E; Balcou, Ph
2014-01-01
The scheme of the XUV/X-ray free electron laser based on the optical undulator created by two overlapped transverse laser beams is analyzed. A kinetic theoretical description and an ad hoc numerical model are developed to account for the finite energy spread, angular divergence and the spectral properties of the electron beam in the optical lattice. The theoretical findings are compared to the results of the one- and three-dimensional numerical modeling with the spectral free electron laser code PLARES.
Application of complex-scaling method for few-body scattering
Lazauskas, Rimantas
2011-01-01
Formalism based on complex-scaling method is developed for solving the few particle scattering problem by employing only trivial boundary conditions. Several applications are presented proving efficiency of the method in describing elastic and three-body break-up reactions for Hamiltonians which may include both short and long-range interaction.
Sica, R J; Haefele, A
2016-02-01
Lidar measurements of the atmospheric water vapor mixing ratio provide an excellent complement to radiosoundings and passive, ground-based remote sensors. Lidars are now routinely used that can make high spatial-temporal resolution measurements of water vapor from the surface to the stratosphere. Many of these systems can operate during the day and night, with operation only limited by clouds thick enough to significantly attenuate the laser beam. To enhance the value of these measurements for weather and climate studies, this paper presents an optimal estimation method (OEM) to retrieve the water vapor mixing ratio, aerosol optical depth profile, Ångstrom exponent, lidar constants, detector dead times, and measurement backgrounds from multichannel vibrational Raman-scatter lidars. The OEM retrieval provides the systematic uncertainties due to the overlap function, calibration factor, air density and Rayleigh-scatter cross sections, in addition to the random uncertainties of the retrieval due to measurement noise. The OEM also gives the vertical resolution of the retrieval as a function of height, as well as the height to which the contribution of the a priori is small. The OEM is applied to measurements made by the Meteoswiss Raman Lidar for Meteorological Observations (RALMO) in the day and night for clear and cloudy conditions. The retrieved water vapor mixing ratio is in excellent agreement with both the traditional lidar retrieval method and coincident radiosoundings.
Mie Light-Scattering Granulometer with an Adaptive Numerical Filtering Method. II. Experiments
Hespel, Laurent; Delfour, André; Guillame, Bernard
2001-02-01
A nephelometer is presented that theoretically requires no absolute calibration. This instrument is used for determining the particle-size distribution of various scattering media (aerosols, fogs, rocket exhausts, engine plumes, and the like) from angular static light-scattering measurements. An inverse procedure is used, which consists of a least-squares method and a regularization scheme based on numerical filtering. To retrieve the distribution function one matches the experimental data with theoretical patterns derived from Mie theory. The main principles of the inverse method are briefly presented, and the nephelometer is then described with the associated partial calibration procedure. Finally, the whole granulometer system (inverse method and nephelometer) is validated by comparison of measurements of scattering media with calibrated monodisperse or known size distribution functions.
Studies of Rigid Rotor-Rigid Surface Scattering in Dynamical Lie Algebraic Method
Institute of Scientific and Technical Information of China (English)
WANG Xiao-Yan; DING Shi-Liang
2004-01-01
The dynamical Lie algebraic method is used for the description of statistical mechanics of rotationally inelastic molecule-surface scattering. It can give the time-evolution operators about the low power of a+ and a by solving a set of coupled nonlinear differential equations. For considering the contribution of the high power of a+ and a, we use the Magnus formula. Thus, with the time-evolution operators we can get the statistical average values of the measurable quantities in terms of the density operator formalism in statistical mechanics. The method is applied to the scattering of N2 (rigid rotor) by a flat, rigid surface to illustrate its general procedure. The results demonstrate that the method is useful for describing the statistical dynamics of gas-surface scattering.
Nguyen, Jennifer; Hayakawa, Carole K; Mourant, Judith R; Venugopalan, Vasan; Spanier, Jerome
2016-05-01
We present a polarization-sensitive, transport-rigorous perturbation Monte Carlo (pMC) method to model the impact of optical property changes on reflectance measurements within a discrete particle scattering model. The model consists of three log-normally distributed populations of Mie scatterers that approximate biologically relevant cervical tissue properties. Our method provides reflectance estimates for perturbations across wavelength and/or scattering model parameters. We test our pMC model performance by perturbing across number densities and mean particle radii, and compare pMC reflectance estimates with those obtained from conventional Monte Carlo simulations. These tests allow us to explore different factors that control pMC performance and to evaluate the gains in computational efficiency that our pMC method provides.
DEFF Research Database (Denmark)
Lagerburg, Vera; de Nijs, Robin; Holm, Søren
2012-01-01
One of the main problems in quantification of single photon emission computer tomography imaging is scatter. In iodine-123 (I-123) imaging, both the primary 159 keV photons and photons of higher energies are scattered. In this experimental study, different scatter correction methods, based on ene...... on energy window subtraction, have been compared with each other....
Numerical simulation of bistatic scattering from fractal rough surface in the finite element method
Institute of Scientific and Technical Information of China (English)
LI; Zhongxin
2001-01-01
［1］Jin, Y. Q., Electromagnetic Scattering Modeling for Quantitative Remote Sensing, Singapore: World Scientific, 1994.［2］Axline, R. M., Fung, A. K., Numerical computation of scattering from a perfectly conducting random surface, IEEE Transactions on Antenna and Propagation, 1978, 26(3): 482.［3］Jin Ya-qiu, Li Gang, Detection of a scatter target over randomly rough surface by using angular correlation function in finite element approach, Waves in Random Media, 2000, 10(4): 273.［4］Lou, S. H., Tsang, L., Chan, C. H. et al., Application of the finite element method of Monte Carlo simulations of scattering of waves by random rough surfaces with the periodic boundary condition, Journal of Electromagnrtic Waves and Applications, 1991, 5(8): 835.［5］Jaggard, D. L., Sun, X., Scattering from fractally corrugated surfaces, Journal of the Optical Society of American A, 1990, 7(6): 1055.［6］Franceschetti, G., Migliaccio, M., Riccio, D., An electromagnetic fractal-based model for the study of fading, Radio Science, 1996, 13(6): 1749.［7］Guerin, C. A., Holschneider, M., Saillard, M., Electromagnetic scattering from multi-scale rough surfaces, Waves in Random Media, 1997, 7(3): 331.［8］Jaggard, D. L., Sun, X., Fractal surface scattering: A generalized Rayleigh solution, Journal of Applied Physics, 1990, 68(11): 5456.［9］Mattia, F., Backscattering properties of multi-scale rough surfaces, Journal of Electromagnetic Waves and Applications, 1999, 13: 493.［10］Savailis, S., Frangos, P., Jaggard, D. L. et al., Scattering from fractally corrugated surfaces with use of the extended boundary condition method, Journal of the Optical Society of American A, 1997, 14(2): 475.［11］Rouvier, S., Chenerie, I., Ultra wide band electromagnetic scattering of a fractal profiles, Radio Science, 1997, 32(2): 285.［12］Sanchez-Gil, J. A., Garcia-Ramon, J. V., Far-field intensity of electromagnetic waves scattered from random, self-affine fractal metal surfaces
Probing scattering resonances of Vogel's spirals with the Green's matrix spectral method.
Christofi, Aristi; Pinheiro, Felipe A; Dal Negro, Luca
2016-05-01
Using the rigorous Green's function spectral method, we systematically investigate the scattering resonances of different types of Vogel spiral arrays of point-like scatterers. By computing the distributions of eigenvalues of the Green's matrix and the corresponding eigenvectors, we obtain important physical information on the spatial nature of the optical modes, their lifetimes and spatial patterns, at small computational cost and for large-scale systems. Finally, we show that this method can be extended to the study of three-dimensional Vogel aperiodic metamaterials and aperiodic photonic structures that may exhibit a richer spectrum of localized resonances of direct relevance to the engineering of novel optical light sources and sensing devices.
Stability of Complex-Rotation Method on a Simple Resonant Scattering Problem
Institute of Scientific and Technical Information of China (English)
SHEN Li; WANG Lei; LIU Xiao-Jun; SHI Ting-Yun; LIU Hong-Ping
2008-01-01
@@ The stability of the complex-rotation method in B-spline basis for a simple atomic resonant scattering problem in free field is investigated. The numerical calculation shows that this method has a feature that the solution will not change in a wide range of rotation angle θ. Our determined scattering resonant energies and widths exactly coincide with the popularly accepted values. A new resonance is identified numerically although it is very broad.The norm of the complex eigenvalue, [E], is proposed to investigate and to evaluate the stability of the obtained complex eigenvalues.
Sukharevsky, Oleg I.; Vasilets, Vitaly A.; Nechitaylo, Sergey V.
2015-01-01
The calculation method for obtaining scattering characteristics of corner reflectors is proposed. The method allows calculating the radar cross-section of corner reflectors for arbitrary aspect angles. The method proposes separating the smooth part of reflectors and some neighborhood of their edges (including that of inner edges). The method accounts for multiple reflections between smooth parts of the reflector surface. In addition, the reflector surface can have a radar absorbing or dielect...
Sakata, Y.; Terasaki, N.; Nonaka, K.
2016-09-01
Fine-polishing techniques may cause micro-cracks under glass substrate surfaces. According to highly requirement from production field, a thermal stress-induced light scattering method (T-SILSM) was successfully developed for a non-contact inspection to detect the micro-cracks through changing in the intensity of light scattering accompanied by applying thermal stress at the responding position of the micro-cracks. In this study, in order to investigate that the origin of the measuring principle in microscopic order, a newly developed microscopic T-SILSM system with a rotation stage and a numerical simulation analysis were used to investigate the following; (1) the scattering points and surface in the micro-crack, (2) the stress concentration points in the micro-crack, and (3) the relationship between these information and the point in which intensity of the light scattering changes in the micro-crack through T-SILSM. Light scattering was observed at the responding position of the micro-crack with selectivity in the direction of laser irradiation even in the microscopic order. In addition, the position of the changes in the light scattering in was at both tips in the micro-crack, and it was consistent with the stress concentration point in the micro-crack. Therefore, it can be concluded that the intentional change in light scattering though T-SILSM is originated from light scattering at micro-crack and also from stress concentration and consecutive change in refractive index at both tips in micro-crack.
Frequency-dispersive method for improving broad-band SBS phase conjugation of Cr:LiSAF laser
Institute of Scientific and Technical Information of China (English)
Chuanwen Ge(葛传文); Weijun Zhang(张为俊)
2003-01-01
After passing through four dispersive-prisms, the Q-switched Cr:LiSAF laser with broad frequency band is focused into carbon disulfide (CS2) to produce backward stimulated Brillouin scattering (SBS). Our experimental results and illustrative analysis have shown that this frequency-dispersive method can efficiently reduce the broad-band SBS intensity threshold, compress its pulsewidth, and improve the beam quality.
Method for laser welding a fin and a tube
Energy Technology Data Exchange (ETDEWEB)
Fuerschbach, Phillip W. (Tijeras, NM); Mahoney, A. Roderick (Albuquerque, NM); Milewski, John O (Santa Fe, NM)
2001-01-01
A method of laser welding a planar metal surface to a cylindrical metal surface is provided, first placing a planar metal surface into approximate contact with a cylindrical metal surface to form a juncture area to be welded, the planar metal surface and cylindrical metal surface thereby forming an acute angle of contact. A laser beam, produced, for example, by a Nd:YAG pulsed laser, is focused through the acute angle of contact at the juncture area to be welded, with the laser beam heating the juncture area to a welding temperature to cause welding to occur between the planar metal surface and the cylindrical metal surface. Both the planar metal surface and cylindrical metal surface are made from a reflective metal, including copper, copper alloys, stainless steel alloys, aluminum, and aluminum alloys.
Apparatus, system, and method for laser-induced breakdown spectroscopy
Effenberger, Jr., Andrew J; Scott, Jill R; McJunkin, Timothy R
2014-11-18
In laser-induced breakdown spectroscopy (LIBS), an apparatus includes a pulsed laser configured to generate a pulsed laser signal toward a sample, a constructive interference object and an optical element, each located in a path of light from the sample. The constructive interference object is configured to generate constructive interference patterns of the light. The optical element is configured to disperse the light. A LIBS system includes a first and a second optical element, and a data acquisition module. The data acquisition module is configured to determine an isotope measurement based, at least in part, on light received by an image sensor from the first and second optical elements. A method for performing LIBS includes generating a pulsed laser on a sample to generate light from a plasma, generating constructive interference patterns of the light, and dispersing the light into a plurality of wavelengths.
Equivalent common path method in large-scale laser comparator
He, Mingzhao; Li, Jianshuang; Miao, Dongjing
2015-02-01
Large-scale laser comparator is main standard device that providing accurate, reliable and traceable measurements for high precision large-scale line and 3D measurement instruments. It mainly composed of guide rail, motion control system, environmental parameters monitoring system and displacement measurement system. In the laser comparator, the main error sources are temperature distribution, straightness of guide rail and pitch and yaw of measuring carriage. To minimize the measurement uncertainty, an equivalent common optical path scheme is proposed and implemented. Three laser interferometers are adjusted to parallel with the guide rail. The displacement in an arbitrary virtual optical path is calculated using three displacements without the knowledge of carriage orientations at start and end positions. The orientation of air floating carriage is calculated with displacements of three optical path and position of three retroreflectors which are precisely measured by Laser Tracker. A 4th laser interferometer is used in the virtual optical path as reference to verify this compensation method. This paper analyzes the effect of rail straightness on the displacement measurement. The proposed method, through experimental verification, can improve the measurement uncertainty of large-scale laser comparator.
Domain and range decomposition methods for coded aperture x-ray coherent scatter imaging
Odinaka, Ikenna; Kaganovsky, Yan; O'Sullivan, Joseph A.; Politte, David G.; Holmgren, Andrew D.; Greenberg, Joel A.; Carin, Lawrence; Brady, David J.
2016-05-01
Coded aperture X-ray coherent scatter imaging is a novel modality for ascertaining the molecular structure of an object. Measurements from different spatial locations and spectral channels in the object are multiplexed through a radiopaque material (coded aperture) onto the detectors. Iterative algorithms such as penalized expectation maximization (EM) and fully separable spectrally-grouped edge-preserving reconstruction have been proposed to recover the spatially-dependent coherent scatter spectral image from the multiplexed measurements. Such image recovery methods fall into the category of domain decomposition methods since they recover independent pieces of the image at a time. Ordered subsets has also been utilized in conjunction with penalized EM to accelerate its convergence. Ordered subsets is a range decomposition method because it uses parts of the measurements at a time to recover the image. In this paper, we analyze domain and range decomposition methods as they apply to coded aperture X-ray coherent scatter imaging using a spectrally-grouped edge-preserving regularizer and discuss the implications of the increased availability of parallel computational architecture on the choice of decomposition methods. We present results of applying the decomposition methods on experimental coded aperture X-ray coherent scatter measurements. Based on the results, an underlying observation is that updating different parts of the image or using different parts of the measurements in parallel, decreases the rate of convergence, whereas using the parts sequentially can accelerate the rate of convergence.
Phase retrieval with the reverse projection method in the presence of object's scattering
Wang, Zhili; Gao, Kun; Wang, Dajiang
2017-08-01
X-ray grating interferometry can provide substantially increased contrast over traditional attenuation-based techniques in biomedical applications, and therefore novel and complementary information. Recently, special attention has been paid to quantitative phase retrieval in X-ray grating interferometry, which is mandatory to perform phase tomography, to achieve material identification, etc. An innovative approach, dubbed ;Reverse Projection; (RP), has been developed for quantitative phase retrieval. The RP method abandons grating scanning completely, and is thus advantageous in terms of higher efficiency and reduced radiation damage. Therefore, it is expected that this novel method would find its potential in preclinical and clinical implementations. Strictly speaking, the reverse projection method is applicable for objects exhibiting only absorption and refraction. In this contribution, we discuss the phase retrieval with the reverse projection method for general objects with absorption, refraction and scattering simultaneously. Especially, we investigate the influence of the object's scattering on the retrieved refraction signal. Both theoretical analysis and numerical experiments are performed. The results show that the retrieved refraction signal is the product of object's refraction and scattering signals for small values. In the case of a strong scattering, the reverse projection method cannot provide reliable phase retrieval. Those presented results will guide the use of the reverse projection method for future practical applications, and help to explain some possible artifacts in the retrieved images and/or reconstructed slices.
Perfectly-matched-layer boundary integral equation method for wave scattering in a layered medium
Lu, Wangtao; Qian, Jianliang
2016-01-01
For scattering problems of time-harmonic waves, the boundary integral equation (BIE) methods are highly competitive, since they are formulated on lower-dimension boundaries or interfaces, and can automatically satisfy outgoing radiation conditions. For scattering problems in a layered medium, standard BIE methods based on the Green's function of the background medium must evaluate the expensive Sommefeld integrals. Alternative BIE methods based on the free-space Green's function give rise to integral equations on unbounded interfaces which are not easy to truncate, since the wave fields on these interfaces decay very slowly. We develop a BIE method based on the perfectly matched layer (PML) technique. The PMLs are widely used to suppress outgoing waves in numerical methods that directly discretize the physical space. Our PML-based BIE method uses the Green's function of the PML-transformed free space to define the boundary integral operators. The method is efficient, since the Green's function of the PML-tran...
The effective index method and its application to semiconductor lasers
DEFF Research Database (Denmark)
Buus, Jens
1982-01-01
By the effective index method a two-dimensional field problem is transformed to a problem for a one-dimensional effective waveguide. This method is applied to semiconductor lasers having a gradual lateral variation in the complex permittivity. For the special case of a parabolic variation...
Hagen, G; Vaagen, J S
2003-01-01
A generalized contour deformation method (GCDM) which combines complex rotation and translation in momentum space, is discussed. GCDM gives accurate results for bound, virtual (antibound), resonant and scattering states starting with a realistic nucleon-nucleon interaction. It provides a basis for full off-shell $t$-matrix calculations both for real and complex input energies. Results for both spectral structures and scattering amplitudes compare perfectly well with exact values for the separable Yamaguchi potential. Accurate calculation of virtual states in the Malfliet-Tjon and the realistic CD-Bonn nucleon-nucleon interactions are presented. GCDM is also a promising method for the computation of in-medium properties such as the resummation of particle-particle and particle-hole diagrams in infinite nuclear matter. Implications for in-medium scattering are discussed.
Liu, Zhengwen; Liu, Shaopu; Wang, Lei; Peng, Juanjuan; He, Youqiu
2009-09-01
In pH 6.6 Britton-Robinson buffer medium, the CdS quantum dots capped by thioglycolic acid could react with aminoglycoside (AGs) antibiotics such as neomycin sulfate (NEO) and streptomycin sulfate (STP) to form the large aggregates by virtue of electrostatic attraction and the hydrophobic force, which resulted in a great enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum scattering peak was located at 310 nm for RRS, 568 nm for SOS and 390 nm for FDS, respectively. The enhancements of scattering intensity (Δ I) were directly proportional to the concentration of AGs in a certain ranges. A new method for the determination of trace NEO and STP using CdS quantum dots probe was developed. The detection limits (3 σ) were 1.7 ng mL -1 (NEO) and 4.4 ng mL -1 (STP) by RRS method, were 5.2 ng mL -1 (NEO) and 20.9 ng mL -1 (STP) by SOS method and were 4.4 ng mL -1 (NEO) and 25.7 ng mL -1 (STP) by FDS method, respectively. The sensitivity of RRS method was the highest. The optimum conditions and influence factors were investigated. In addition, the reaction mechanism was discussed.
Oh, J.; Weaver, J. L.; Kehne, D. M.; Phillips, L. S.; Obenschain, S. P.; Serlin, V.; McLean, E. A.; Lehmberg, R. H.; Manka, C. K.
2009-11-01
With short wavelength (248 nm), large bandwidth (˜1 THz), and ISI beam smoothing, Nike KrF laser provides unique opportunities of LPI research for direct-drive inertial confinement fusion. Previous experiments at intensities (10^15˜10^16 W/cm^2) exceeded two-plasmon decay (TPD) instability threshold using 12 beam-lines of Nike laser.^a,b For further experiments to study LPI excitation in bigger plasma volumes, 44 Nike main beams have been used to produce plasmas with total laser energies up to 1 kJ of ˜350 psec FWHM pulses. This talk will present results of the recent LPI experiment focusing on light emission data in spectral ranges relevant to the Raman (SRS) and TPD instabilities. The primary diagnostics were time-resolved spectrometers with an absolute-intensity-calibrated photodiode array in (0.4˜0.8)φ0 and a streak camera near 0.5φ0. Blackbody temperature and expansion speed measurements of the plasmas were also made. The experiment was conducted at laser intensities of (1˜4)x10^15 W/cm^2 on solid planar CH targets. ^a J. L. Weaver, et al, NO4.14, APS DPP (2008) ^b J. Oh, et al, NO4.15, APS DPP (2008) * Work supported by DoE/NNSA and performed at Naval Research Laboratory.
Oh, Jaechul; Weaver, J. L.; Phillips, L.; Obenschain, S. P.; Schmitt, A. J.; Kehne, D. M.; Serlin, V.; Lehmberg, R. H.; McLean, E. A.; Manka, C. K.
2010-11-01
With short wavelength (248 nm), large bandwidth (1˜3 THz), and ISI beam smoothing, Nike KrF laser provides unique research opportunities and potential for direct-drive inertial confinement fusion. Previous Nike experiments observed two plasmon decay (TPD) driven signals from CH plasmas at the laser intensities above ˜2x10^15 W/cm^2 with total laser energies up to 1 kJ of ˜350 ps FWHM pulses. We have performed a further experiment with longer laser pulses (0.5˜4.0 ns FWHM) and will present combined results of the experiments focusing on light emission data in spectral ranges relevant to the Raman (SRS) and TPD instabilities. Time- or space-resolved spectral features of TPD were detected at different viewing angles and the absolute intensity calibrated spectra of thermal background were used to obtain blackbody temperatures in the plasma corona. The wave vector distribution in k-space of the participating TPD plasmons will be also discussed. These results show promise for the proposed direct-drive designs.
A new pulsed laser deposition technique: scanning multi-component pulsed laser deposition method.
Fischer, D; de la Fuente, G F; Jansen, M
2012-04-01
The scanning multi-component pulsed laser deposition (PLD) method realizes uniform depositions of desired coatings by a modified pulsed laser deposition process, preferably with a femto-second laser-system. Multi-component coatings (single or multilayered) are thus deposited onto substrates via laser induced ablation of segmented targets. This is achieved via horizontal line-scanning of a focused laser beam over a uniformly moving target's surface. This process allows to deposit the desired composition of the coating simultaneously, starting from the different segments of the target and adjusting the scan line as a function of target geometry. The sequence and thickness of multilayers can easily be adjusted by target architecture and motion, enabling inter/intra layer concentration gradients and thus functional gradient coatings. This new, simple PLD method enables the achievement of uniform, large-area coatings. Case studies were performed with segmented targets containing aluminum, titanium, and niobium. Under the laser irradiation conditions applied, all three metals were uniformly ablated. The elemental composition within the rough coatings obtained was fixed by the scanned area to Ti-Al-Nb = 1:1:1. Crystalline aluminum, titanium, and niobium were found to coexist side by side at room temperature within the substrate, without alloy formation up to 600 °C.
Identification of Molecular Laser Transitions Using the Finite Element Method
1995-12-01
Vibration Levels," Physical Review, Vol. 34, 1929 12 Arfken , George Mathematical Methods for Physicists. San Diego: Academic Press, Inc. 1985 13...unsolvable. Mathematical techniques such as the classical Rayleigh-Ritz method , variational calculus, and Galerkin’s weighted residuals method , much...AFIT/GAP/ENP/95D-14 IDENTIFICATION OF MOLECULAR LASER TRANSITIONS USING THE FINITE ELEMENT METHOD THESIS Matthew C. Smitham, Captain, USAF AFIT/GAP
Energy Technology Data Exchange (ETDEWEB)
Miranda, Javier; Cahill, T.A.; Morales, J.R. (California Univ., Davis, CA (United States). Crocker Nuclear Lab.); Aldape, F.; Flores M, J.; Diaz, R.V. (Instituto Nacional de Investigaciones Nucleares, Mexico City (Mexico))
1994-01-01
A study of the concentrations of elements present in atmospheric aerosols at two different sites in Mexico City was done with samples taken during September 1990 and February 1991. The samples were taken daily during 6 h periods (from 6:00 to 12:00 hr), using a Stacking Filter Unit (SFU) of the Davis design. This allowed the separation of particles with sizes ranging from 2.5 to 15 [mu]m (coarse mass), and smaller than 2.5 [mu]m (fine mass). Analyses of the samples with Proton Induced X-ray Emission (PIXE) gave information on elements heavier than Ne, Proton Elastic Scattering Analysis (PESA) on hydrogen contents, and the Laser Integrating Plate Method (LIPM) was used on the fine fraction to determine soot contents. Cluster Analysis is applied to the sample set in order to identify the emission sources of the elements. Additionally, the relationship to several meteorological variables is presented. (author).
DEFF Research Database (Denmark)
Zhang, Yang; Hansen, Hans Nørgaard; Tang, Peter T.
2013-01-01
In this article, laser-induced selective activation (LISA) for subsequent autocatalytic copper plating is performed by several types of industrial scale lasers, including a Nd:YAG laser, a UV laser, a fiber laser, a green laser, and a short pulsed laser. Based on analysis of all the laser-machine...
Characterization of nuclear graphite elastic properties using laser ultrasonic methods
Zeng, Fan W.; Han, Karen; Olasov, Lauren R.; Gallego, Nidia C.; Contescu, Cristian I.; Spicer, James B.
2015-05-01
Laser ultrasonic methods have been used to characterize the elastic behaviors of commercially-available and legacy nuclear graphites. Since ultrasonic techniques are sensitive to various aspects of graphite microstructure including preferred grain orientation, microcrack orientation and porosity, laser ultrasonics is a candidate technique for monitoring graphite degradation and structural integrity in environments expected in high-temperature, gas-cooled nuclear reactors. Aspects of materials texture can be assessed by studying ultrasonic wavespeeds as a function of propagation direction and polarization. Shear wave birefringence measurements, in particular, can be used to evaluate elastic anisotropy. In this work, laser ultrasonic measurements of graphite moduli have been made to provide insight into the relationship between the microstructures and the macroscopic stiffnesses of these materials. In particular, laser ultrasonic measurements have been made using laser line sources to produce shear waves with specific polarizations. By varying the line orientation relative to the sample, shear wave birefringence measurements have been recorded. Results from shear wave birefringence measurements show that an isostatically molded graphite, such as PCIB, behaves isotropically, while an extruded graphite, such as H-451, displays significant ultrasonic texture. Graphites have complicated microstructures that depend on the manufacturing processes used, and ultrasonic texture in these materials could originate from grain orientation and preferred microcrack alignment. Effects on material isotropy due to service related microstructural changes are possible and the ultimate aim of this work is to determine the degree to which these changes can be assessed nondestructively using laser ultrasonics measurements.
A practical calculational method for treating Coulomb scattering in momentum space
Energy Technology Data Exchange (ETDEWEB)
Elster, Ch. (Ohio Univ., Athens, OH (United States). Dept. of Physics and Astronomy); Liu, L.C. (Los Alamos National Lab., NM (United States)); Thaler, R.M. (Los Alamos National Lab., NM (United States) Case Western Reserve Univ., Cleveland, OH (United States). Dept. of Physics)
1993-12-01
An exact and practical numerical procedure for treating the Coulomb interaction in momentum-space calculations of elastic scattering of charged particles is presented. The method is tested for various interactions over a wide charge, energy and angular momentum range and found to be accurate. (Author).
Institute of Scientific and Technical Information of China (English)
Feng Lixin; Jia Niannian
2007-01-01
A new computational algorithm is introduced for solving scattering problem in periodic structure. The PML technique is used to deal with the difficulty on truncating the unbounded domain while the DSC algorithm is utilized for the spatial discretization. The present study reveals that the method is efficient for solving the problem.
Perego, R.C.
2004-01-01
Two novel neutron-based analytical techniques have been treated in this thesis, Neutron Resonance Capture Analysis (NRCA), employing a pulsed neutron source, and Neutron Incoherent Scattering (NIS), making use of a cold neutron source. With the NRCA method isotopes are identified by the isotopic-spe
Perego, R.C.
2004-01-01
Two novel neutron-based analytical techniques have been treated in this thesis, Neutron Resonance Capture Analysis (NRCA), employing a pulsed neutron source, and Neutron Incoherent Scattering (NIS), making use of a cold neutron source. With the NRCA method isotopes are identified by the
Transform method for laser speckle strain-rate measurements in biological tissues and biomaterials
Kirkpatrick, Sean J.
1999-03-01
Laser speckle strain measurements in biological tissues and some synthetic biomaterials, such as translucent dental composites and ceramics, are often complicated by the physical properties of the materials. For example, speckles generated by illuminating soft biological tissue with laser light are subject to rapid decorrelation due to the Brownian movement of water and scattering particles in the tissues and to cellular motions. In addition, the penetration of the laser beam into the tissue or translucent biomaterial results in multiple scattering and a complete depolarization of the speckle field. This may complicate the evaluation of the strain field when a force is applied to the material because the speckle pattern shift is providing information from the surface of the material as well as from the bulk sample, where the strains may or may not be the same as on the surface. This paper presents a variation of a speckle processing scheme originally called the `Transform Method' for evaluating both surface and bulk strain rates and total strains in biological tissues and translucent biomaterials. The method is not a correlation-based technique, but instead relies upon 2D frequency transforms of time series of 1D speckle pattern records stacked into 2D arrays. The method is insensitive to speckle field depolarization and, compared to correlation-based techniques, is relatively insensitive to speckle decorrelation. Strain rates and total in-plane strains were measured in both hard (cortical bone) and soft (artery segments) biological tissues and in translucent biomaterials (dental ceramics). Potential applications to medical diagnostics and biomaterials science are also discussed.
Amplification and generation of ultra-intense twisted laser pulses via stimulated Raman scattering
Vieira, J; Alves, E P; Fonseca, R A; Mendonça, J T; Bingham, R; Norreys, P; Silva, L O
2016-01-01
Twisted Laguerre-Gaussian lasers, with orbital angular momentum and characterised by doughnut shaped intensity profiles, provide a transformative set of tools and research directions in a growing range of fields and applications, from super-resolution microcopy and ultra-fast optical communications to quantum computing and astrophysics. The impact of twisted light is widening as recent numerical calculations provided solutions to long-standing challenges in plasma-based acceleration by allowing for high gradient positron acceleration. The production of ultrahigh intensity twisted laser pulses could then also have a broad influence on relativistic laser-matter interactions. Here we show theoretically and with ab-initio three-dimensional particle-in-cell simulations, that stimulated Raman backscattering can generate and amplify twisted lasers to Petawatt intensities in plasmas. This work may open new research directions in non-linear optics and high energy density science, compact plasma based accelerators and ...
Finite-volume Hamiltonian method for $\\pi\\pi$ scattering in lattice QCD
Wu, Jia-Jun; Leinweber, Derek B; Thomas, A W; Young, Ross D
2015-01-01
Within a formulation of $\\pi\\pi$ scattering, we investigate the use of the finite-volume Hamiltonian approach to resolving scattering observables from lattice QCD spectra. We consider spectra in the centre-of-mass and moving frames for both S- and P-wave cases. Furthermore, we investigate the multi-channel case. Here we study the use of the Hamiltonian framework as a parametrization that can be fit directly to lattice spectra. Through this method, the hadron properties, such as mass, width and coupling, can be directly extracted from the lattice spectra.
Buried Object Detection by an Inexact Newton Method Applied to Nonlinear Inverse Scattering
Directory of Open Access Journals (Sweden)
Matteo Pastorino
2012-01-01
Full Text Available An approach to reconstruct buried objects is proposed. It is based on the integral equations of the electromagnetic inverse scattering problem, written in terms of the Green’s function for half-space geometries. The full nonlinearity of the problem is exploited in order to inspect strong scatterers. After discretization of the continuous model, the resulting equations are solved in a regularization sense by means of a two-step inexact Newton algorithm. The capabilities and limitations of the method are evaluated by means of some numerical simulations.
Magnetic and structural properties of thin films and nanoparticles studied by scattering methods
Feygenson, M.
2007-01-01
The present work concerns the magnetic and structural proprieties of magnetic thin films and magnetic nanoparticles studied by scattering methods.The structural properties of epitaxially grown Fe/Cr/Fe trilayer were studied with anomalous x-ray scattering. Two different x-ray energies have been used; (i) one E$_1$=5985eV to match the maximum contrast of the Fe/Cr interface close to the Cr absorption K-edge and (ii) a second one E$_2$=6940eV where the Fe/Cr interface displays the lowest contra...
Energy Technology Data Exchange (ETDEWEB)
Tracy, M.D.
1993-01-08
Collective Thomson scattering from ion-acoustic waves at 266nm is used to obtain spatially resolved, two-dimensional electron density, sound speed, and radial drift profiles of a collisional laser plasma. An ultraviolet diagnostic wavelength minimizes the complicating effects of inverse bremsstrahlung and refractive turning in the coronal region of interest, where the electron densities approach n{sub c}/10. Laser plasmas of this type are important because they model some of the aspects of the plasmas found in high-gain laser-fusion pellets irradiated by long pulse widths where the laser light is absorbed mostly in the corona. The experimental results and LASNEX simulations agree within a percent standard deviation of 40% for the electron density and 50% for the sound speed and radial drift velocity. Thus it is shown that the hydrodynamics equations with classical coefficients and the numerical approximations in LASNEX are valid models of laser-heated, highly collisional plasmas. The versatility of Thomson scattering is expanded upon by extending existing theory with a Fokker-Planck based model to include plasmas that are characterized by (0 {le} k{sub ia}{lambda}{sub ii} {le} {infinity}) and ZT{sub e}/T{sub i}, where k{sub ia} is the ion- acoustic wave number, {lambda}{sub ii} is the ion-ion mean free path, Z is the ionization state of the plasma, and T{sub e}, T{sub i} are the electron and ion temperatures in electron volts respectively. The model is valid for plasmas in which the electrons are approximately collisionless, (k{sub ia}{lambda}{sub ei}, k{sub ia}{lambda}{sub ee} {ge} 1), and quasineutrality holds, ({alpha} {much_gt}1), where {alpha} = 1/k{lambda}{sub DE} and {lambda}{sub DE} is the electron Debye length. This newly developed model predicts the lineshape of the ion-acoustic Thomson spectra and when fit to experimental data provides a direct measurement of the relative thermal flow velocity between the electrons and ions.
Ivanov, D Y; Serbo, V G
2003-01-01
We consider emission of a photon by an electron in the field of a strong laser wave. Polarization effects in this process are important for a number of physical problems. We discuss a probability of this process for linearly polarized laser photons and for arbitrary polarization of all other particles. We obtain the complete set of functions which describe such a probability in a compact form.
Gu, Bo; Chen, Yubin; Wang, Zefeng
2016-11-01
We report here the detailed characteristics of 1.9 μm laser emission from hydrogen-filled hollow-core fiber by stimulated Raman scattering. A 6.5 m hydrogen-filled Ice-cream negative curvature hollow-core fiber is pumped with a high peak power, narrow linewidth, liner polarized subnanosecond pulsed 1064 nm microchip laser, generating pulsed 1908.5 nm vibrational Stokes wave. The linewidth of the pump laser and the vibrational Stokes wave is about 1 GHz and 2 GHz respectively. And the maximum Raman conversion quantum efficiency is about 48%. We also studied the pulse shapes of the pump laser and the vibrational Stokes wave. The polarization dependence of the vibrational and the rotational stimulated Raman scattering is also investigated. In addition, the beam profile of vibrational Stokes wave shows good quality, which may be taken advantage of in many applications.
Tokunaga, Kyoya; Fang, Yi-Cheng; Yokoyama, Hiroyuki; Ozeki, Yasuyuki
2016-03-01
We present a picosecond laser source based on a gain-switched laser diode (GS-LD) that can be applied to stimulated Raman scattering (SRS) microscopy. A 1.06-μm GS-LD was used to generate 14-ps pulses at a repetition rate of 38 MHz. The GS-LD was driven by 200-ps electrical pulses, which were triggered through a toggle flip-flop (T-FF). As a result, the GS-LD pulses were subharmonically synchronized to Ti:sapphire laser (TSL) pulses at a repetition rate of 76 MHz. We investigated the timing jitter of GS-LD pulses and found it to be less than 2.5 ps. We also show that the trigger delay can be less sensitive to the optical power of TSL pulses by controlling the threshold voltage of the T-FF. As a result, GS-LD pulses sufficiently overlapped with TSL pulses even when we scanned the wavelength of the TSL pulses. We demonstrate the SRS imaging of HeLa cells with GS-LD pulses and TSL pulses, proving that GS-LD is readily applicable to SRS microscopy as a compact and stable pulse source.
Soltanmoradi, Elmira; Shokri, Babak
2017-05-01
In this article, the electromagnetic wave scattering from plasma columns with inhomogeneous electron density distribution is studied by the Green's function volume integral equation method. Due to the ready production of such plasmas in the laboratories and their practical application in various technological fields, this study tries to find the effects of plasma parameters such as the electron density, radius, and pressure on the scattering cross-section of a plasma column. Moreover, the incident wave frequency influence of the scattering pattern is demonstrated. Furthermore, the scattering cross-section of a plasma column with an inhomogeneous collision frequency profile is calculated and the effect of this inhomogeneity is discussed first in this article. These results are especially used to determine the appropriate conditions for radar cross-section reduction purposes. It is shown that the radar cross-section of a plasma column reduces more for a larger collision frequency, for a relatively lower plasma frequency, and also for a smaller radius. Furthermore, it is found that the effect of the electron density on the scattering cross-section is more obvious in comparison with the effect of other plasma parameters. Also, the plasma column with homogenous collision frequency can be used as a better shielding in contrast to its inhomogeneous counterpart.
Rubtsova, O. A.; Kukulin, V. I.; Moro, A. M.
2008-09-01
The direct comparison of two different continuum discretization methods toward the solution of a composite particle scattering off a nucleus is presented. The first approach—the continuum-discretized coupled-channel method—is based on the differential equation formalism, while the second one—the wave-packet continuum discretization method—uses the integral equation formulation for the composite-particle scattering problem. As benchmark calculations, we have chosen the deuteron off Ni58 target scattering (as a realistic illustrative example) at three different incident energies: high, middle, and low. Clear nonvanishing effects of closed inelastic channels at small and intermediate energies are established. The elastic cross sections found in both approaches are very close to each other for all three considered energies.
Institute of Scientific and Technical Information of China (English)
SHA Wei; HUANG Zhi-Xiang; WU Xian-Liang; CHEN Ming-Sheng
2006-01-01
Using symplectic integrator propagator, a three-dimensional fourth-order symplectic finite difference time domain (SFDTD) method is studied, which is of the fourth order in both the time and space domains. The method is nondissipative and can save more memory compared with the traditional FDTD method. The total field and scattered field (TF-SF) technique is derived for the SFDTD method to provide the incident wave source conditions. The bistatic radar cross section (RCS) of a dielectric sphere is computed by using the SFDTD method for the first time. Numerical results suggest that the SFDTD algorithm acquires better stability and accuracy compared with the traditional FDTD method.
Time-step limits for a Monte Carlo Compton-scattering method
Energy Technology Data Exchange (ETDEWEB)
Densmore, Jeffery D [Los Alamos National Laboratory; Warsa, James S [Los Alamos National Laboratory; Lowrie, Robert B [Los Alamos National Laboratory
2008-01-01
Compton scattering is an important aspect of radiative transfer in high energy density applications. In this process, the frequency and direction of a photon are altered by colliding with a free electron. The change in frequency of a scattered photon results in an energy exchange between the photon and target electron and energy coupling between radiation and matter. Canfield, Howard, and Liang have presented a Monte Carlo method for simulating Compton scattering that models the photon-electron collision kinematics exactly. However, implementing their technique in multiphysics problems that include the effects of radiation-matter energy coupling typically requires evaluating the material temperature at its beginning-of-time-step value. This explicit evaluation can lead to unstable and oscillatory solutions. In this paper, we perform a stability analysis of this Monte Carlo method and present time-step limits that avoid instabilities and nonphysical oscillations by considering a spatially independent, purely scattering radiative-transfer problem. Examining a simplified problem is justified because it isolates the effects of Compton scattering, and existing Monte Carlo techniques can robustly model other physics (such as absorption, emission, sources, and photon streaming). Our analysis begins by simplifying the equations that are solved via Monte Carlo within each time step using the Fokker-Planck approximation. Next, we linearize these approximate equations about an equilibrium solution such that the resulting linearized equations describe perturbations about this equilibrium. We then solve these linearized equations over a time step and determine the corresponding eigenvalues, quantities that can predict the behavior of solutions generated by a Monte Carlo simulation as a function of time-step size and other physical parameters. With these results, we develop our time-step limits. This approach is similar to our recent investigation of time discretizations for the
Wahle, Chris W; Ross, David S; Thurston, George M
2013-09-28
We extend methods of solution of a light scattering partial differential equation for the free energy of mixing to apply to connected, isotropic ternary liquid composition domains that do not touch all three binary axes. To do so we mathematically analyze the problem of inferring needed Dirichlet boundary data, and solving for the free energy, with use of hypothetical static light scattering measurements that correspond to dielectric composition gradient vectors that have distinct directions. The physical idea behind the technique is that contrasting absorption properties of mixture components can result in such distinctly directed dielectric composition gradient vectors, due to their differing wavelength dependences of dielectric response. At suitably chosen wavelengths, contrasting light scattering efficiency patterns in the ternary composition triangle can then correspond to the same underlying free energy, and enlarge the scope of available information about the free energy, as shown here. We show how to use distinctly directed dielectric gradients to measure the free energy on both straight lines and curves within the ternary composition triangle, so as to provide needed Dirichlet conditions for light scattering partial differential equation solution. With use of Monte Carlo simulations of noisy light scattering data, we provide estimates of the overall system measurement time and sample spacing needed to determine the free energy to a desired degree of accuracy, for various angles between the assumed dielectric gradient vectors, and indicate how the measurement time depends on instrumental throughput parameters. The present analysis methods provide a way to use static light scattering to measure, directly, mixing free energies of many systems that contain such restricted liquid domains, including aqueous solutions of biological macromolecules, micellar mixtures and microemulsions, and many small molecule systems that are important in separation technology.
Laser spectroscopic methods as a means of determining water pollutants
Kubitz, Joerg; Uebel, Ulrieke; Anders, Angelika
1995-09-01
The suitability of laser-induced fluorescence spectroscopy was evaluated as a method for the in-situ detection of water contaminants. For example, lead thallium, cerium, benzene, pyrene, toluene, xylene, naphtalene, and anthracene were investigated. The absorption-, fluorescence-, and excitation-spectra of each contaminant were measured in distilled water, artificial seawater and natural seawater as the examination of pollution spectra, that has been described in literature so far, does not characterize the contaminants dissolution in water. The chosen polycyclic aromatic hydrocarbons (PAHs) and heavy metals were excited by means of a frequency doubled dye laser, the latter being pumped by an excimer laser or by a frequency tripled Nd:YAG laser. The laser emitted radiation in the range from 220 nm to 400 nm. The fluorescence signal was recorded in the 230 nm to 600 nm range. The detection limits were in the ppb-range for the PAHs and in the ppm to ppb range for the heavy metals. Computer- simulations were applied to analyze the spectra of pollutant mixtures. They displayed a superimposition of the individual spectra. Discrete components of a mixture could be distinguished using this method. Finally, the influence of dissolved organic matter was investigated.
Energy Technology Data Exchange (ETDEWEB)
Lavisse, L.; Jouvard, J.-M.; Girault, M.; Potin, V.; Andrzejewski, H.; Marco de Lucas, M. C.; Bourgeois, S. [Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 6303 CNRS-Universite de Bourgogne, 9 Avenue A. Savary, BP 47870-21078 Dijon Cedex (France); Le Garrec, J.-L.; Carles, S.; Mitchell, J. B. A. [Institut de Physique de Rennes, UMR 6251 CNRS-Universite de Rennes 1, 35042 Rennes Cedex (France); Hallo, L. [CEA CESTA, 15 Avenue des Sablieres CS 60001, 33116 Le Barp Cedex (France); Perez, J. [Synchrotron SOLEIL, L' Orme des Merisiers, Saint-Aubin, F-91192 Gif-sur-Yvette Cedex (France); Decloux, J. [Kaluti System, Optique et Laser, Centre Scientifique d' Orsay, 91400 Orsay (France)
2012-04-16
Small angle x-ray scattering was used to probe in-situ the formation of nanoparticles in the plasma plume generated by pulsed laser irradiation of a titanium metal surface under atmospheric conditions. The size and morphology of the nanoparticles were characterized as function of laser irradiance. Two families of nanoparticles were identified with sizes on the order of 10 and 70 nm, respectively. These results were confirmed by ex-situ transmission electron microscopy experiments.
Institute of Scientific and Technical Information of China (English)
TU; Mei; HUANG; Yaoxiong
2004-01-01
The laser light scattering technique for non-invasive in situ simultaneous measurements on elastic constants and viscosity coefficients of nematic liquid crystals is introduced. By measuring the autocorrelation function of the scattered light from nematic liquid crystals at different scattering angles, the splay and twist elastic constants K11 and K22 are obtained from the amplitudes of the autocorrelation function, and the viscosity coefficients of (Splay and (Twist are determined using the viscoelastic ratios K11/( Splay and K22/(Twist from the relaxation parameters of the two modes.
Schell, Stefan; Wilkens, Jan J
2010-10-01
Laser plasma acceleration can potentially replace large and expensive cyclotrons or synchrotrons for radiotherapy with protons and ions. On the way toward a clinical implementation, various challenges such as the maximum obtainable energy still remain to be solved. In any case, laser accelerated particles exhibit differences compared to particles from conventional accelerators. They typically have a wide energy spread and the beam is extremely pulsed (i.e., quantized) due to the pulsed nature of the employed lasers. The energy spread leads to depth dose curves that do not show a pristine Bragg peak but a wide high dose area, making precise radiotherapy impossible without an additional energy selection system. Problems with the beam quantization include the limited repetition rate and the number of accelerated particles per laser shot. This number might be too low, which requires a high repetition rate, or it might be too high, which requires an additional fluence selection system to reduce the number of particles. Trying to use laser accelerated particles in a conventional way such as spot scanning leads to long treatment times and a high amount of secondary radiation produced when blocking unwanted particles. The authors present methods of beam delivery and treatment planning that are specifically adapted to laser accelerated particles. In general, it is not necessary to fully utilize the energy selection system to create monoenergetic beams for the whole treatment plan. Instead, within wide parts of the target volume, beams with broader energy spectra can be used to simultaneously cover multiple axially adjacent spots of a conventional dose delivery grid as applied in intensity modulated particle therapy. If one laser shot produces too many particles, they can be distributed over a wider area with the help of a scattering foil and a multileaf collimator to cover multiple lateral spot positions at the same time. These methods are called axial and lateral
Bacteriological comparison of low anal fistula operated by ordinary methods and laser methods
Yang, Yuanrong; Xiong, Yigai
1996-09-01
Since 1989, 42 cases with low anal fistula were operated with laser and ordinary methods respectively. During the operation, secreted or charred tissues were extracted from the surface of the wound for bacteria culture. Experimental group (laser method): no bacteria were found in 24 cases operated by laser method. Control group (ordinary method): bacterial were found in 16 out of 18 cases operated by ordinary methods. The results of two different group showed that they had statistical difference for P anal fistula were operated by the laser, the neurotic carboatomic tissue can block blood vessel and prevent infection from spreading. The high temperature produced by the carboatomic action have enough ability to kill directly the bacteria living in the anal fistula.
DEFF Research Database (Denmark)
Saffman, Mark; Zoletnik, S.; Basse, Nils Plesner
2001-01-01
We describe and demonstrate a two-volume collective scattering system for localized measurements of plasma turbulence. The finite crossfield correlation length of plasma turbulence combined with spatial variations in the magnetic field direction are used to obtain spatially localized turbulence...
hp-finite element method for simulating light scattering from complex 3D structures
Burger, S; Pomplun, J; Herrmann, S; Schmidt, F
2015-01-01
Methods for solving Maxwell's equations are integral part of optical metrology and computational lithography setups. Applications require accurate geometrical resolution, high numerical accuracy and/or low computation times. We present a finite-element based electromagnetic field solver relying on unstructured 3D meshes and adaptive hp-refinement. We apply the method for simulating light scattering off arrays of high aspect-ratio nano-posts and FinFETs.
A FINITE ELEMENT METHOD WITH RECTANGULAR PERFECTLY MATCHED LAYERS FOR THE SCATTERING FROM CAVITIES
Institute of Scientific and Technical Information of China (English)
Deyue Zhang; Fuming Ma; Heping Dong
2009-01-01
We develop a finite element method with rectangular perfectly matched layers (PMLs) for the wave scattering from two-dimensional cavities. The unbounded computational domain is truncated to a bounded one by using of a rectangular perfectly matched layer at the open aperture. The PML parameters such as the thickness of the layer and the fictitious medium property are determined through sharp a posteriori error estimates. Numerical experiments are carried out to illustrate the competitive behavior of the proposed method.
Complex scaling method for three- and four-body scattering above the break-up thresholds
Lazauskas, Rimantas
2012-01-01
A formalism based on the complex-scaling method is presented to solve the few particle scattering problem in configuration space using bound state techniques with trivial boundary conditions. Several applications to A=3,4 systems are presented to demonstrate the efficiency of the method in computing elastic as well as break-up reactions with Hamiltonians including both short and long-range interaction.
Progress on hybrid finite element methods for scattering by bodies of revolution
Collins, Jeffery D.; Volakis, John L.
1992-01-01
Progress on the development and implementation of hybrid finite element methods for scattering by bodies of revolution are described. It was found that earlier finite element-boundary integral formulations suffered from convergence difficulties when applied to large and thin bodies of revolution. An alternative implementation is described where the finite element method is terminated with an absorbing termination boundary. In addition, an alternative finite element-boundary integral implementation is discussed for improving the convergence of the original code.
Xu, Kaichen; Zhang, Chentao; Zhou, Rui; Ji, Rong; Hong, Minghui
2016-05-16
Surface enhanced Raman spectroscopy (SERS) has drawn much research interest in the past decades as an efficient technique to detect low-concentration molecules. Among many technologies, which can be used to fabricate SERS substrates, laser ablation is a simple and high-speed method to produce large-area SERS substrates. This work investigates the angular texturing effect by dynamic laser ablation and its influence on SERS signals. By tuning the angle between the Si surface and laser irradiation, the distributions and sizes of laser induced hybrid micro/nano-structures are studied. By decorating with a silver film, plenty of hot spots can be created among these structures for SERS. It is found that when the incident laser angle is 15° at the laser fluence of 16.0 J/cm2, the SERS performance is well optimized. This work realizes antisymmetric distribution of nanoparticles deposited on Si surface, which provides a flexible tuning of the hybrid micro/nano-structures' fabrication with high controllability for practical applications.
Energy Technology Data Exchange (ETDEWEB)
Yin, L.; Albright, B. J.; Rose, H. A.; Montgomery, D. S.; Kline, J. L.; Bowers, K. J.; Bergen, B. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Kirkwood, R. K.; Michel, P. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
2013-01-15
Nonlinear physics governing the kinetic behavior of stimulated Raman scattering (SRS) in multi-speckled laser beams has been identified in the trapping regime over a wide range of k{lambda}{sub D} values (here k is the wave number of the electron plasma waves and {lambda}{sub D} is the Debye length) in homogeneous and inhomogeneous plasmas. Hot electrons from intense speckles, both forward and side-loss hot electrons produced during SRS daughter electron plasma wave bowing and filamentation, seed and enhance the growth of SRS in neighboring speckles by reducing Landau damping. Trapping-enhanced speckle interaction through transport of hot electrons, backscatter, and sidescatter SRS light waves enable the system of speckles to self-organize and exhibit coherent, sub-ps SRS bursts with more than 100% instantaneous reflectivity, resulting in an SRS transverse coherence width much larger than a speckle width and a SRS spectrum that peaks outside the incident laser cone. SRS reflectivity is found to saturate above a threshold laser intensity at a level of reflectivity that depends on k{lambda}{sub D}: higher k{lambda}{sub D} leads to lower SRS and the reflectivity scales as {approx}(k{lambda}{sub D}){sup -4}. As k{lambda}{sub D} and Landau damping increase, speckle interaction via sidescattered light and side-loss hot electrons decreases and the occurrence of self-organized events becomes infrequent, leading to the reduction of time-averaged SRS reflectivity. It is found that the inclusion of a moderately strong magnetic field in the laser direction can effectively control SRS by suppressing transverse speckle interaction via hot electron transport.
Method for laser spectroscopy of metastable pionic helium atoms
Energy Technology Data Exchange (ETDEWEB)
Hori, M., E-mail: Masaki.Hori@mpq.mpg.de; Sótér, A.; Aghai-Khozani, H. [Max-Planck-Institut für Quantenoptik (Germany); Barna, D. [CERN (Switzerland); Dax, A. [Paul Scherrer Institut (Switzerland); Hayano, R. S.; Murakami, Y.; Yamada, H. [University of Tokyo, Department of Physics (Japan)
2015-08-15
The PiHe collaboration is currently attempting to carry out laser spectroscopy of metastable pionic helium atoms using the high-intensity π{sup −} beam of the ring cyclotron facility of the Paul Scherrer Institute. These atoms are heretofore hypothetical three-body Coulomb systems each composed of a helium nucleus, a π{sup −} occupying a Rydberg state, and an electron occupying the 1s ground state. We briefly review the proposed method by which we intend to detect the laser spectroscopic signal. This complements our experiments on metastable antiprotonic helium atoms at CERN.
Kubelka, Jan
2009-04-01
Many important biochemical processes occur on the time-scales of nanoseconds and microseconds. The introduction of the laser temperature-jump (T-jump) to biophysics more than a decade ago opened these previously inaccessible time regimes up to direct experimental observation. Since then, laser T-jump methodology has evolved into one of the most versatile and generally applicable methods for studying fast biomolecular kinetics. This perspective is a review of the principles and applications of the laser T-jump technique in biophysics. A brief overview of the T-jump relaxation kinetics and the historical development of laser T-jump methodology is presented. The physical principles and practical experimental considerations that are important for the design of the laser T-jump experiments are summarized. These include the Raman conversion for generating heating pulses, considerations of size, duration and uniformity of the temperature jump, as well as potential adverse effects due to photo-acoustic waves, cavitation and thermal lensing, and their elimination. The laser T-jump apparatus developed at the NIH Laboratory of Chemical Physics is described in detail along with a brief survey of other laser T-jump designs in use today. Finally, applications of the laser T-jump in biophysics are reviewed, with an emphasis on the broad range of problems where the laser T-jump methodology has provided important new results and insights into the dynamics of the biomolecular processes.
Kashima, Susumu; Nishihara, Minoru; Takemoto, Yoshihiro; Osawa, Toshihiko
1990-09-01
The laser scattering characteristics from tissue microvasculature have been made clear by means of theoretical and experimental approaches. Our results show that the integrated intensity of the power spectrum correlates linearly with the volume of red blood cells in a given tissue provided the average collision number (\\bar{m}) between photons and moving red blood cells is less than unity. Also, the integrated intensity of the power spectrum is proportional to tissue blood volume if the density of red blood cells in blood (hematocrit) is constant.
Studies of oxide-based thin-layered heterostructures by X-ray scattering methods
Energy Technology Data Exchange (ETDEWEB)
Durand, O. [Thales Research and Technology France, Route Departementale 128, F-91767 Palaiseau Cedex (France)]. E-mail: olivier.durand@thalesgroup.com; Rogers, D. [Nanovation SARL, 103 bis rue de Versailles 91400 Orsay (France); Universite de Technologie de Troyes, 10-12 rue Marie Curie, 10010 (France); Teherani, F. Hosseini [Nanovation SARL, 103 bis rue de Versailles 91400 Orsay (France); Andrieux, M. [LEMHE, ICMMOCNRS-UMR 8182, Universite d' Orsay, Batiment 410, 91410 Orsay (France); Modreanu, M. [Tyndall National Institute, Lee Maltings, Prospect Row, Cork (Ireland)
2007-06-04
Some X-ray scattering methods (X-ray reflectometry and Diffractometry) dedicated to the study of thin-layered heterostructures are presented with a particular focus, for practical purposes, on the description of fast, accurate and robust techniques. The use of X-ray scattering metrology as a routinely working non-destructive testing method, particularly by using procedures simplifying the data-evaluation, is emphasized. The model-independent Fourier-inversion method applied to a reflectivity curve allows a fast determination of the individual layer thicknesses. We demonstrate the capability of this method by reporting X-ray reflectometry study on multilayered oxide structures, even when the number of the layers constitutive of the stack is not known a-priori. Fast Fourier transform-based procedure has also been employed successfully on high resolution X-ray diffraction profiles. A study of the reliability of the integral-breadth methods in diffraction line-broadening analysis applied to thin layers, in order to determine coherent domain sizes, is also reported. Examples from studies of oxides-based thin-layers heterostructures will illustrate these methods. In particular, X-ray scattering studies performed on high-k HfO{sub 2} and SrZrO{sub 3} thin-layers, a (GaAs/AlOx) waveguide, and a ZnO thin-layer are reported.
A method of laser micro-polishing for metallic surface using UV nano-second pulse and CW lasers
Jang, Pong-Ryol; Ji, Kum-Hyok; Kim, Nam-Chol
2014-01-01
During laser micro-polishing, the constant control of laser energy density is a key technology to improve the surface roughness. In this paper, a method which controls the energy density of UV(ultraviolet) pulse laser in real time with the control of CW(continuous wave) laser spot size in laser micro-polishing for metallic surface was presented. The experimental and analytical considerations of several influence factors such as laser spot size, fusion zone and focal offset were investigated. In addition, using a laser micro-polishing system manufactured with this method, the laser micro-polishing experiments on the two different surface shapes of stainless steel 316L were conducted. For the inclined or curved surface, the surface roughness improvements of up to 56.4% and 57.3% were respectively obtained, and the analysis of the results were discussed.
Institute of Scientific and Technical Information of China (English)
Wang Rui; Guo Li-Xin; Ma Jun; Wu Zhen-Sen
2009-01-01
A current based hybrid method(HM)is proposed which combines the method of moment(MOM)with the Kirchhoff approximation(KA)for the analysis of scattering interaction between a two-dimensional(2D)infinitely long conducting target with arbitrary cross section and a one-dimensional(1D)Ganssian rough surface.The electromagnetic scattering region in the HM is split into KA region and MOM region.The electric field integral equation(EFIE)in MOM region(target)is derived,the computational time of the HM depends mainly on the number of unknowns of the target.The bistatic scattering coefficient for the infinitely long cylinder above the rough surface with Gaussian roughness spectrum is calculated,and the numerical results are compared and verified with those obtained by the conventional MOM,which shows the high efficiency of the HM.Finally,the influence of the size,location of the target,the rms height and correlation length of the rough surface on the bistatic scattering coefficient with different polarizations is discussed in detail.
Institute of Scientific and Technical Information of China (English)
DUAN Hui; LIU Zhong-Fang; LIU Shao-Pu; KONG Ling
2008-01-01
Heated in a boiling water bath, penicillin antibiotics such as amoxicillin, ampicillin, sodium cloxacillin, sodium carbenicillin and sodium benzylpenicillin could react with K3[Fe(CN)6] to form combined products in a dilute HCl medium.As a result, resonance Rayleigh scattering (RRS) intensity was enhanced greatly and new RRS spectra appeared.The maximum scattering wavelengths of the five combined products are all located at 330 nm.The scattered intensity increments (△I) of the combined products are directly proportional to the concentrations of the antibiotics in a certain range.The methods exhibit high sensitivity, and the detection limits for the five penicillin antibiotics are between 4.61 and 5.62 ng·mL-1.The spectral characteristics of RRS and the optimum reaction conditions were investigated.The mechanism of reaction and the reasons for the enhancement of resonance light scattering were discussed.The effects of coexisting substances have been examined, and the results indicated that the method had a good selectivity.It can be applied to the determination of penicillin antibiotics in capsule, tablet, human serum and urine samples.
Material measurement method based on femtosecond laser plasma shock wave
Zhong, Dong; Li, Zhongming
2017-03-01
The acoustic emission signal of laser plasma shock wave, which comes into being when femtosecond laser ablates pure Cu, Fe, and Al target material, has been detected by using the fiber Fabry-Perot (F-P) acoustic emission sensing probe. The spectrum characters of the acoustic emission signals for three kinds of materials have been analyzed and studied by using Fourier transform. The results show that the frequencies of the acoustic emission signals detected from the three kinds of materials are different. Meanwhile, the frequencies are almost identical for the same materials under different ablation energies and detection ranges. Certainly, the amplitudes of the spectral character of the three materials show a fixed pattern. The experimental results and methods suggest a potential application of the plasma shock wave on-line measurement based on the femtosecond laser ablating target by using the fiber F-P acoustic emission sensor probe.
Ivanov, D Y; Serbo, V G
2003-01-01
We consider emission of a photon by an electron in the field of a strong laser wave. Polarization effects in this process are important for a number of physical problems. We discuss a probability of this process for circularly polarized laser photons and for arbitrary polarization of all other particles. We obtain the complete set of functions which describe such a probability in a compact covariant form. Besides, we discuss an application of the obtained formulas to the problem of electron -> photon conversion at photon-photon and photon-electron colliders.
Geant4 simulations on Compton scattering of laser photons on relativistic electrons
Energy Technology Data Exchange (ETDEWEB)
Filipescu, D. [Extreme Light Infrastructure - Nuclear Physics, str. Atomistilor nr. 407, Bucharest-Magurele, P.O.BOX MG6, Romania and National Institute for Physics and Nuclear Engineering Horia Hulubei, str. Atomistilor nr. 407 (Romania); Utsunomiya, H. [Department of Physics, Konan University, Okamoto 8-9-1, Higashinada, Kobe 658-8501 (Japan); Gheorghe, I.; Glodariu, T. [National Institute for Physics and Nuclear Engineering Horia Hulubei, str. Atomistilor nr. 407 (Romania); Tesileanu, O. [Extreme Light Infrastructure - Nuclear Physics, str. Atomistilor nr. 407, Bucharest-Magurele, P.O.BOX MG6 (Romania); Shima, T.; Takahisa, K. [Research Center for Nuclear Physics, Osaka University, Suita, Osaka 567-0047 (Japan); Miyamoto, S. [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Kouto, Kamigori, Hyogo 678-1205 (Japan)
2015-02-24
Using Geant4, a complex simulation code of the interaction between laser photons and relativistic electrons was developed. We implemented physically constrained electron beam emittance and spacial distribution parameters and we also considered a Gaussian laser beam. The code was tested against experimental data produced at the γ-ray beam line GACKO (Gamma Collaboration Hutch of Konan University) of the synchrotron radiation facility NewSUBARU. Here we will discuss the implications of transverse missallignments of the collimation system relative to the electron beam axis.
Bakhlanov, S. V.; Bazlov, N. V.; Derbin, A. V.; Drachnev, I. S.; Kayunov, A. S.; Muratova, V. N.; Semenov, D. A.; Unzhakov, E. V.
2016-06-01
In this paper we present a method of scintillation detector energy calibration using the gamma-rays. The technique is based on the Compton scattering of gamma-rays in a scintillation detector and subsequent photoelectric absorption of the scattered photon in the Ge-detector. The novelty of this method is that the source of gamma rays, the germanium and scintillation detectors are immediately arranged adjacent to each other. The method presents an effective solution for the detectors consisting of a low atomic number materials, when the ratio between Compton effect and photoelectric absorption is large and the mean path of gamma-rays is comparable to the size of the detector. The technique can be used for the precision measurements of the scintillator light yield dependence on the electron energy.
Bakhlanov, S V; Derbin, A V; Drachnev, I S; Kayunov, A S; Muratova, V N; Semenov, D A; Unzhakov, E V
2016-01-01
In this paper we present a method of scintillation detector energy calibration using the gamma-rays. The technique is based on the Compton scattering of gamma-rays in a scintillation detector and subsequent photoelectric absorption of the scattered photon in the Ge-detector. The novelty of this method is that the source of gamma rays, the germanium and scintillation detectors are immediately arranged adjacent to each other. The method presents an effective solution for the detectors consisting of a low atomic number materials, when the ratio between Compton effect and photoelectric absorption is large and the mean path of gamma-rays is comparable to the size of the detector. The technique can be used for the precision measurements of the scintillator light yield dependence on the electron energy.
Energy Technology Data Exchange (ETDEWEB)
Bakhlanov, S.V. [St.Petersburg Nuclear Physics Institute, National Research Center “Kurchatov Institute”, Gatchina 188300 (Russian Federation); Bazlov, N.V. [Saint-Petersburg State University, Universitetskaja nab. 7/9, Saint-Petersburg 199034 (Russian Federation); Derbin, A.V., E-mail: derbin@pnpi.spb.ru [St.Petersburg Nuclear Physics Institute, National Research Center “Kurchatov Institute”, Gatchina 188300 (Russian Federation); Drachnev, I.S. [St.Petersburg Nuclear Physics Institute, National Research Center “Kurchatov Institute”, Gatchina 188300 (Russian Federation); GranSasso Science Institute, INFN, L' Aquila (AQ) I-67100 (Italy); Kayunov, A.S.; Muratova, V.N.; Semenov, D.A.; Unzhakov, E.V. [St.Petersburg Nuclear Physics Institute, National Research Center “Kurchatov Institute”, Gatchina 188300 (Russian Federation)
2016-06-11
In this paper we present a method of scintillation detector energy calibration using the gamma-rays. The technique is based on the Compton scattering of gamma-rays in a scintillation detector and subsequent photoelectric absorption of the scattered photon in the Ge-detector. The novelty of this method is that the source of gamma rays, the germanium and scintillation detectors are immediately arranged adjacent to each other. The method presents an effective solution for the detectors consisting of a low atomic number materials, when the ratio between Compton effect and photoelectric absorption is large and the mean path of gamma-rays is comparable to the size of the detector. The technique can be used for the precision measurements of the scintillator light yield dependence on the electron energy.
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
Using a polarization method, the scattering problem for a two-dimensional inclusion embedded in infinite piezoelectric/piezomagnetic matrices is investigated. To achieve the purpose, the polarization method for a two-dimensional piezoelectric/piezo-magnetic "comparison body" is formulated. For simple harmonic motion, kernel of the polarization method reduces to a 2-D time-harmonic Green's function, which is ob-tained using the Radon transform. The expression is further simplified under condi-tions of low frequency of the incident wave and small diameter of the inclusion. Some analytical expressions are obtained. The analytical solutions for generalized piezoelec-tric/piezomagnetic anisotropic composites are given followed by simplified results for piezoelectric composites. Based on the latter results, two numerical results are provided for an elliptical cylindrical inclusion in a PZT-5H-matrix, showing the effect of different factors including size, shape, material properties, and piezoelectricity on the scattering cross-section.
New method for diagnosing cast compactness based on laser ultrasonography
Directory of Open Access Journals (Sweden)
P. Swornowski
2010-01-01
Full Text Available Technologically advanced materials, such as alloys of aluminum, nickel or titanium are currently used increasingly often in significantly loaded components utilized in the aviation industry, among others in the construction of jet turbine engine blades. The article presents a method for diagnosing the condition of the inside of cast blades with the use of laser ultrasonography. The inspection is based on finding hidden flaws with a size of between 10 and 30μm. Laser ultrasonography offers a number of improvements over the non-destructive methods used so far, e.g. the possibility to diagnose the cast on a selected depth, high signal-to-noise ratio and good sensitivity. The article includes a brief overview of non-destructive inspection methods used in foundry engineering and sample results of inspecting the inner structure of a turbo jet engine blade using the method described in the article.
Plane wave method for elastic wave scattering by a heterogeneous fracture
Energy Technology Data Exchange (ETDEWEB)
Nakagawa, Seiji; Nihei, Kurt T.; Myer, Larry R.
2003-02-21
A plane-wave method for computing the three-dimensional scattering of propagating elastic waves by a planar fracture with heterogeneous fracture compliance distribution is presented. This method is based upon the spatial Fourier transform of the seismic displacement-discontinuity (SDD) boundary conditions (also called linear slip interface conditions), and therefore, called the wave-number-domain SDD method (wd-SDD method). The resulting boundary conditions explicitly show the coupling between plane waves with an incident wave number component (specular component) and scattered waves which do not follow Snell's law (nonspecular components) if the fracture is viewed as a planar boundary. For a spatially periodic fracture compliance distribution, these boundary conditions can be cast into a linear system of equations that can be solved for the amplitudes of individual wave modes and wave numbers. We demonstrate the developed technique for a simulated fracture with a stochastic (correlated) surface compliance distribution. Low- and high-frequency solutions of the method are also compared to the predictions by low-order Born series in the weak and strong scattering limit.
Discrete ordinates transport methods for problems with highly forward-peaked scattering
Energy Technology Data Exchange (ETDEWEB)
Pautz, S.D.
1998-04-01
The author examines the solutions of the discrete ordinates (S{sub N}) method for problems with highly forward-peaked scattering kernels. He derives conditions necessary to obtain reasonable solutions in a certain forward-peaked limit, the Fokker-Planck (FP) limit. He also analyzes the acceleration of the iterative solution of such problems and offer improvements to it. He extends the analytic Fokker-Planck limit analysis to the S{sub N} equations. This analysis shows that in this asymptotic limit the S{sub N} solution satisfies a pseudospectral discretization of the FP equation, provided that the scattering term is handled in a certain way (which he describes) and that the analytic transport solution satisfies an analytic FP equation. Similar analyses of various spatially discretized S{sub N} equations reveal that they too produce solutions that satisfy discrete FP equations, given the same provisions. Numerical results agree with these theoretical predictions. He defines a multidimensional angular multigrid (ANMG) method to accelerate the iterative solution of highly forward-peaked problems. The analyses show that a straightforward application of this scheme is subject to high-frequency instabilities. However, by applying a diffusive filter to the ANMG corrections he is able to stabilize this method. Fourier analyses of model problems show that the resulting method is effective at accelerating the convergence rate when the scattering is forward-peaked. The numerical results demonstrate that these analyses are good predictors of the actual performance of the ANMG method.
Energy Technology Data Exchange (ETDEWEB)
Horikawa, K.; Miyamoto, S.; Mochizuki, T.; Amano, S. [University of Hyogo, Hyogo 678-1205 (Japan); Li, D.; Imasaki, K.; Izawa, Y. [Institute for Laser Technology, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan); Ogata, K. [Osaka University, 1-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Chiba, S. [Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Japan Atomic Energy Agency, Shirakata-Shirane 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); Hayakawa, T., E-mail: hayakawa.takehito@jaea.go.jp [Japan Atomic Energy Agency, Shirakata-Shirane 2-4, Tokai-mura, Ibaraki 319-1195 (Japan); National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan)
2014-10-07
In 1957, Agodi predicted that the neutron angular distribution in (γ, n) reactions with a 100% linearly polarized γ-ray beam for dipole excitation should be anisotropic and universally described by the simple function of a+b⋅cos(2ϕ) at the polar angle θ=90°, where ϕ is the azimuthal angle. However, this prediction has not been experimentally confirmed in over half a century. We have verified experimentally this angular distribution in the (γ, n) reaction for {sup 197}Au, {sup 127}I, and natural Cu targets using linearly polarized laser Compton scattering γ-rays. The result suggests that the (γ{sup →}, n) reaction is a novel tool to study nuclear physics in the giant dipole resonance region.
Hajireza, Parsin; Forbrich, Alexander; Zemp, Roger
2014-02-01
In this paper a multi-wavelength optical-resolution photoacoustic microscopy (OR-PAM) system using stimulated Raman scattering is demonstrated for both phantom and in vivo imaging. A 1-ns pulse width ytterbium-doped fiber laser is coupled into a single-mode polarization maintaining fiber. Discrete Raman-shifted wavelength peaks extending to nearly 800 nm are generated with pulse energies sufficient for OR-PAM imaging. Bandpass filters are used to select imaging wavelengths. A dual-mirror galvanometer system was used to scan the focused outputs across samples of carbon fiber networks, 200μm dye-filled tubes, and Swiss Webster mouse ears. Photoacoustic signals were collected in transmission mode and used to create maximum amplitude projection C-scan images. Double dye experiments and in vivo oxygen saturation estimation confirmed functional imaging potential.