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A fusion technique which combines two different types of sensory data for 3-D modeling of a navigation space is presented. The sensory data is generated by a vision camera and a laser scanner. The problem of different resolutions for these sensory data was solved by reduced image resolution, fusion of different data, and use of a fuzzy image segmentation technique.

A fusion technique which combines two different types of sensory data for 3-D modeling of a navigation space is presented. The sensory data is generated by a vision camera and a laser scanner. The problem of different resolutions for these sensory data was solved by reduced image resolution, fusion of different data, and use of a fuzzy image segmentation technique.

A fusion technique which combines two different types of sensory data for 3-D modeling of a navigation space is presented. The sensory data is generated by a vision camera and a laser scanner. The problem of different resolutions for these sensory data was solved by reduced image resolution, fusion of different data, and use of a fuzzy image segmentation technique.

Pulsed laser communication systems have been proposed which work through all types of clouds. Predicting the performance of such systems requires a knowledge of the statistics of the spatial, angular and temporal spreading of pulses by clouds. Current models are particularly weak in predicting pulse transmission/reflection when the transmitter is near the horizon with respect to the receiver. A database consisting of the probability of cloud pattern types has been developed to be used with a database of cloud pattern properties. Together these two databases are used to predict system performance statistics for operational scenarios. In the future, real-time operational planning for message delivery will require short term predictions of cloud fields and their effects on performance. Models of reflection of pulses from clouds, as well as transmission through them are needed to make accurate evaluations of the probability of interception and disclosure of receiver or transmitter position. Reprints.

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In this project we investigate the impact of the maritime environment on the propagation of laser beams. This study primarily uses data collected at the Naval Academy with the goal of quantifying the correlation between the statistics of the environmental parameters and the statistics of laser beam intensity at the target. The project has two parts to it: 1) we present a computational analysis of different probability density function approximation techniques; and 2) we introduce preliminary steps towards developing a stochastic model for the maritime laser beam propagation. In the first part of this work we apply three mathematical methods to construct the probability density function of the data: i) the Kernel Density Estimator (KDE) method, ii) the Barakat Method using lower-order moments, and iii) the Bayesian Mixture Model. We compare and contrast the features of the three approximation techniques, first in the context of a synthetic data whose true pdf is known, and next in the context of the laser data. In the second task, we analyze how a complex medium causes the photons of the laser light to behave differently than if they were acting in freespace, by focusing on the stochastic behavior that our data exhibits. We develop a stochastic paraxial wave equation in order to have a mathematical model capable of accepting statistical parameters from the atmosphere as input to allow us to investigate the statistical properties of light intensity at a specified target.

Scattering calculations using a more detailed model of the multimode laser beam in the forward-scattering spectrometer probe (FSSP) were carried out by using a recently developed extension to Mie scattering theory. From this model, new calibration curves for the FSSP were calculated. The difference between the old calibration curves and the new ones is small for droplet diameters less than 10 micrometers, but the difference increases to approximately 10% at diameters of 50 micrometers. When using glass beads to calibrate the FSSP, calibration errors can be minimized, by using glass beads of many different diameters, over the entire range of the FSSP. If the FSSP is calibrated using one-diameter glass beads, then the new formalism is necessary to extrapolate the calibration over the entire range.

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Efficient control of a laser welding process requires the reliable prediction of process behavior. A statistical method of field modeling, based on normalized RBFNN, can be successfully used to predict the spatiotemporal dynamics of surface optical activity in the laser welding process. In this article we demonstrate how to optimize RBFNN to maximize prediction quality. Special attention is paid to the structure of sample vectors, which represent the bridge between the field distributions in the past and future.

An analytical expression for approximating the time-dependent thermal focal length in finite solid state laser rods was derived. The analysis is based on the temperature variation of the material refractive index caused by optical pumping of these rods. Several quantities were found to be relevant to this analysis. These quantities were the specific thermal profiles of the rods, type of optical pumping employed, type of cooling scheme employed (side and end-cooling parameters), and the specific material characteristics of the rods. The Thermal Lensing Model was formulated using the geometric ray tracing approach. The focal lengths are then approximated, by calculating the phase shift in the index of refraction, as the different rays of an incident plane wave are tracked through a lens-like crystal medium. The approach also applies in the case of Gaussian or parabolic pump beams. It is shown that the prediction of thermal focal length is in good quantitative agreement with experimentally obtained data.

The mathematical modeling of reaction systems for chemical generation of atomic iodine is presented. This process can be applied in the chemical oxygen-iodine laser (COIL), where it can save a substantial part of energy of singlet oxygen and so increase the laser output power. The parametric study of the production of atomic fluorine and subsequently atomic iodine in dependence on the pressure and dilution with inert gas was made. The calculation of the interaction between produced atomic iodine and singlet oxygen was made with four different mixing/reacting schemes.

New Mexico State University (NMSU) proposed acquisition of equipment to establish an integrated system for laser-assisted, non-intrusive experimentation and data-driven reduced-order modeling of multidisciplinary phenomena in structural and fluid dynamics. The system consists of three components: (i) a 1D scanning laser vibrometer for structural vibration tests; (ii) a 3D particle image velocimetry (PIV) system for experimental fluid dynamics; and (iii) a 3D scanner for computational mesh data. All these three components have been acquired and installed respectively in the designated laboratories, and are currently tested to build up an integrated system as proposed. This integrated system assists the PI and key personnel in promoting a novel systematic methodology for data-driven (yet physics-based) reduced-order models of strongly nonlinear, unsteady, multidisciplinary and multiscale dynamics by means of analytical / empirical decomposition methods. The experimental system has been utilized to promote STEM education at NMSU by encouraging students participation in research-oriented projects. The courses that benefited include ME 456 Experimental Modal Analysis, AE 447 / ME510 Aero/Fluids Laboratory, and ME 533 Computational Fluid Dynamics.

Laser-induced fluorescence (LIF) has been applied to the quantitative measurement of nitric oxide (NO) in premixed, laminar, high-pressure flames. Their chemistry was also studied using three current kinetics schemes to determine the predictive capabilities of each mechanism with respect to NO concentrations. The flames studied were low-temperature (1600 less than T less than 1850K) C2H6/O2/N2 and C2H6/O2/N2 flames, and high temperature (2100 less than T less than 2300K) C2H6/O2/N2 flames. Laser-saturated fluorescence (LSF) was initially used to measure the NO concentrations. However, while the excitation transition was well saturated at atmospheric pressure, the fluorescence behavior was basically linear with respect to laser power at pressures above 6 atm. Measurements and calculations demonstrated that the fluorescence quenching rate variation is negligible for LIF measurements of NO at a given pressure. Therefore, linear LIF was used to perform quantitative measurements of NO concentration in these high-pressure flames. The transportability of a calibration factor from one set of flame conditions to another also was investigated by considering changes in the absorption and quenching environment for different flame conditions. The feasibility of performing LIF measurements of (NO) in turbulent flames was studied; the single-shot detection limit was determined to be 2 ppm.

A terrain modeling algorithm that would reconstruct the sensed ground images formed by the triangulation scheme, and classify as unsafe any terrain feature that would pose a hazard to a roving vehicle is described. This modeler greatly reduces quantization errors inherent in a laser/sensing system through the use of a thinning algorithm. Dual filters are employed to separate terrain steps from the general landscape, simplifying the analysis of terrain features. A crosspath analysis is utilized to detect and avoid obstacles that would adversely affect the roll of the vehicle. Computer simulations of the rover on various terrains examine the performance of the modeler.

With the advent of lasers as weapons, it is necessary to understand how a laser propagates through a complex medium. For the U.S. Navy, the complexity of a maritime environment imposes particular challenges for laser propagation due to high concentrations of water vapor and high probabilities of liquid water in the form of fog, rain, or sea spray along the beam path. Although considerable research has gone into characterizing the maritime environment and simulating laser propagation through water vapor and turbulence, the interactions between a high energy laser (HEL) and liquid water are poorly understood. A project is taking place in the U.S. Naval Academys Directed Energy Research Center to investigate the interaction of a high energy laser and single water droplets. An HEL is used to irradiate droplets of water, and the droplet shape and size, the infrared radiation from the droplet, and the transmitted beam profile are measured and recorded. To control the droplet shape, it will be levitated using a commercial ultrasonic levitator, where the drop is held in place at a node by the pressure from a standing sound wave. The results of this experiment will provide an understanding of the coupled interaction between an HEL and a water droplet.

The potential application of the laser-induced fluorescence method for determining number densities and temperatures of gas species is investigated through computer modeling of the detailed relaxation of laser-excited molecular and atomic-molecular systems. The rate equation models for a sodium-diatomic molecular system and a single diatomic molecule system are explained and applied to the case of sodium-nitrogen and pure carbon monoxide.

The Satellite Survivability Module (SSM) is an end-to-end, physics-based, performance prediction model for directed energy engagement of orbiting spacecraft. Two engagement types are currently supported: laser engagement of the focal plane array of an imaging spacecraft and Radio Frequency (RF) engagement of spacecraft components. For laser engagements, the user creates a spacecraft, its optical system, any protection techniques used by the optical system, a laser threat, and an atmosphere through which the laser will pass. For RF engagements, the user creates a spacecraft (as a set of subsystem components), any protection techniques, and an RF source. SSM then models the engagement and its impact on the spacecraft using four impact levels: degradation, saturation, damage, and destruction. Protection techniques, if employed, will mitigate engagement effects. SSM currently supports two laser and three RF protection techniques. SSM allows the user to create and implement a variety of what if scenarios. Satellites can be placed in a variety of orbits. Threats can be placed anywhere on the Earth. Satellites and threats can be mixed and matched to examine possibilities. Protection techniques for a particular spacecraft can be turned on or off individually and can be arranged in any order to simulate more complicated protection schemes. Results can be displayed as 2-D or 3-D visualizations, or as textual reports.

A fusion technique which combines two different types of sensory data for 3-D modeling of a navigation space is presented. The sensory data is generated by a vision camera and a laser scanner. The problem of different resolutions for these sensory data was solved by reduced image resolution, fusion of different data, and use of a fuzzy image segmentation technique.

The SERDP statement of need that led to this research project focuses on a requirement for better models of the mechanisms of soot formation in combustion. Soot and its combustion precursors present human health hazards. In the case of Army fighting vehicles, such as those powered by diesel engines, it is of interest to achieve the maximum possible power density. One way to do this is to run at high fuel/oxidizer ratios. However, this gives rise to high soot pollutant emissions. While they are important, health issues of the soot are not the only issue and are not the utmost concern during battle. High soot emission levels in combat vehicles may give rise to large target signatures, thus adversely affecting survivability. In the report of the SERDP-sponsored June 1999 American Academy of Environmental Engineers Air Quality Workshop [1], a major conclusion is that chemical kinetics and aerosol dynamics governing formation and control of PM (particulate material such as soot) and associated HAPs (Hazardous Air Pollutants, such as PAH, Polycyclic Aromatic Hydrocarbons, which are precursors of soot) is a primary area needing research. The report goes on to state that models which use presently available mechanisms are in need of refinements to achieve agreement with experiments and predictive capabilities. A fundamental understanding of the factors and detailed chemistry that govern the formation and destruction of soot and its precursors is important for the identification of control methods. This project centered upon the chemical kinetics mechanism. For several decades there has been a controversy in soot formation whether ion or free radical mechanisms dominate the early, nucleation stages of the process starting with molecules containing only one or a few carbon atoms; of course, one or the other may dominate under a variety of conditions. Nucleation mechanisms involving ions have fallen into disfavor in the eyes of many researchers.

We report on a simple one-dimensional model developed for the fluid dynamics and chemical kinetics in the chemical oxygen iodine laser (COIL). Two different I2 dissociation mechanisms are tested against the performance of a COIL device in our laboratory. The two dissociation mechanisms chosen are the celebrated mechanism of Heidner and the newly suggested mechanism of Heaven. The gain calculated using Heaven's dissociation mechanism is much lower than the measured one. Employing Heidner's mechanism, a surprisingly good agreement is obtained between the measured and calculated gain and temperature over a wide range of the flow parameters. Other predictions of the model (larger mixing efficiency and higher temperature with a leak opened downstream of the resonator and gain decrease along the flow) are also in agreement with the experimental observations.

We report on a simple one-dimensional model developed for the fluid dynamics and chemical kinetics in the chemical oxygen iodine laser (COIL). Two different I2 dissociation mechanisms are tested against the performance of a COIL device in our laboratory. The two dissociation mechanisms chosen are the celebrated mechanism of Heidner and the newly suggested mechanism of Heaven. The gain calculated using Heaven's dissociation mechanism is much lower than the measured one. Employing Heidner's mechanism, a surprisingly good agreement is obtained between the measured and calculated gain and temperature over a wide range of the flow parameters. Other predictions of the model (larger mixing efficiency and higher temperature with a leak opened downstream of the resonator and gain decrease along the flow) are also in agreement with the experimental observations.

Measurements of mass flux are obtained in a vitiated supersonic ground test facility using a sensor based on line-of-sight (LOS) diode laser absorption of water vapor. Mass flux is determined from the product of measured velocity and density. The relative Doppler shift of an absorption transition for beams directed upstream and downstream in the flow is used to measure velocity. Temperature is determined from the ratio of absorption signals of two transitions (lambda(sub 1)=1349 nm and lambda(sub 2)=1341.5 nm) and is coupled with a facility pressure measurement to obtain density. The sensor exploits wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f) for large signal-to-noise ratios and normalization with the 1f signal for rejection of non-absorption related transmission fluctuations. The sensor line-of-sight is translated both vertically and horizontally across the test section for spatially-resolved measurements. Time-resolved measurements of mass flux are used to assess the stability of flow conditions produced by the facility. Measurements of mass flux are within 1.5% of the value obtained using a facility predictive code. The distortion of the WMS lineshape caused by boundary layers along the laser line-of-sight is examined and the subsequent effect on the measured velocity is discussed. A method for correcting measured velocities for flow non-uniformities is introduced and application of this correction brings measured velocities within 4 m/s of the predicted value in a 1630 m/s flow.

Laser beam propagation through the earth's atmosphere is influenced by absorption and scattering by ice crystals as occur in cirrus clouds. New instruments (cloudscopes) and laboratory chambers (thermal diffusion, fall tower) have been designed and built to characterize and simulate such crystals to measure absorption and scatter of laser beams. The cloudscope, deployed for aircraft or laboratory use, collects and video-records to crystals to provide a measure of their size, habit, concentration and also density by evaporating the particles after collection. This procedure also reveals their inner structure and the presence of any impurity. These investigations provide protocols for aircraft sampling and analysis of cirrus particles to be analyzed in real-time. This provides input for regional scale models of ice crystal evolution in terms of temperature, supersaturation and fall velocity, resulting in prediction of habits following growth, melt and evaporation and their likely optical properties.

Laser communication between satellites in the constellation and from the satellites to ground stations offers a gigantic data rate for the users. This principal advantage drives telecom companies to develop this technology to use it like a carrier signal, the most disadvantage of this technology is the need to very complicated pointing systems between the transmitter and the receiver due to a very small beam divergence, continually moving of satellites in orbits and the distance between the satellites (tens of thousands of kilometers). The laser beam suffers continuously from several factors like atmospheric turbulences, internal and external vibrations. All these factors lead to an increase in the bit errors rate and cause degradation in the communication quality. This paper deals with a new method of modelisation of external effects in transmission of signal light from a ground station to the satellite through atmospheric disturbances. Indeed, an in-depth investigation, of the influences of satellite vibrationsinlaser signal transmission between satellites constellation, has been conducted by studying the effect of the intensity of vibrations on the optical signal amplitude. Some solutions are proposed to improve the efficiency of optical satellites communications.

The coupled electromagnetic-thermo-mechanical response of RDX (cyclotrimethylene trinitramine)-polymer energetic aggregates under laser irradiation and high strain rate loads has been investigated to identify laser-induced hot spot formation and failure mechanisms at different physical scales. A computational approach was developed to investigate the coupled phenomena of high frequency electromagnetic (EM) wave propagation, laser heat absorption, thermal conduction, and inelastic dynamic thermomechanical deformation in heterogeneous energetic materials. The approach couples Maxwell's equations with a dislocation density-based crystal plasticity formulation with a nonlinear finite-element approach to predict and understand thermo-mechanical response due to the interrelated effects of dielectric heating, adiabatic heating, thermal decomposition, and heat conduction. The effects of heterogeneous microstructural characteristics, such as void distribution and spacing, grain morphologies and orientations, crystal-binder interactions, and dislocation densities were analyzed to determine their influence on hot spot formation and EM and mechanical energy localization. The effects of beam intensity, incident wavelength, material electromagnetic absorption coefficient, and the heterogeneous microstructure on spatial and temporal behavior and mechanisms of laser-induced hot spot formation were characterized and related to the thermo-mechanical response. Different mechanisms for hot spot initiation under dynamic laser and pressure loads were identified, which are a function of shear strain localization and laser heat absorption. The predictions indicate that hot spot formation was accelerated by higher absorption coefficients and by localized plastic deformations that occurred in areas of significant laser heating.

The coupled electromagnetic-thermo-mechanical response of RDX (cyclotrimethylene trinitramine)-polymer energetic aggregates under laser irradiation and high strain rate loads has been investigated to identify laser-induced hot spot formation and failure mechanisms at different physical scales. A computational approach was developed to investigate the coupled phenomena of high frequency electromagnetic (EM) wave propagation, laser heat absorption, thermal conduction, and inelastic dynamic thermomechanical deformation in heterogeneous energetic materials. The approach couples Maxwell's equations with a dislocation density-based crystal plasticity formulation with a nonlinear finite-element approach to predict and understand thermo-mechanical response due to the interrelated effects of dielectric heating, adiabatic heating, thermal decomposition, and heat conduction. The effects of heterogeneous microstructural characteristics, such as void distribution and spacing, grain morphologies and orientations, crystal-binder interactions, and dislocation densities were analyzed to determine their influence on hot spot formation and EM and mechanical energy localization. The effects of beam intensity, incident wavelength, material electromagnetic absorption coefficient, and the heterogeneous microstructure on spatial and temporal behavior and mechanisms of laser-induced hot spot formation were characterized and related to the thermo-mechanical response. Different mechanisms for hot spot initiation under dynamic laser and pressure loads were identified, which are a function of shear strain localization and laser heat absorption. The predictions indicate that hot spot formation was accelerated by higher absorption coefficients and by localized plastic deformations that occurred in areas of significant laser heating.

Scattering calculations using a more detailed model of the multimode laser beam in the forward-scattering spectrometer probe (FSSP) were carried out by using a recently developed extension to Mie scattering theory. From this model, new calibration curves for the FSSP were calculated. The difference between the old calibration curves and the new ones is small for droplet diameters less than 10 micrometers, but the difference increases to approximately 10% at diameters of 50 micrometers. When using glass beads to calibrate the FSSP, calibration errors can be minimized, by using glass beads of many different diameters, over the entire range of the FSSP. If the FSSP is calibrated using one-diameter glass beads, then the new formalism is necessary to extrapolate the calibration over the entire range.

The design and performance of a photon counting, two-channel spectroscopic system using the 6-W, 448-nm line of a cw argon ion laser is described. The two channels are formed by use of cylindrical optics and special slit mirrors set up following the exit slit of a conventional double spectrometer. The system is capable of dynamic, simultaneous measurements of either the concentrations of two gas species in cold flow or the temperature and concentration of a single gas species, such as N2, in a flame. Measurements are accomplished by recording the intensities of two spontaneous rotational Raman lines with spectral bandwidths between 0.04 and 0.08 nm. Up to 4096 samples (or reads from each of the two channels) can be recorded by a dedicated minicomputer at rates up to 10 kHz. Studies of a CH4 diffusion flame at sampling rates of 20 to 100 Hz and a room-temperature, axisymmetric C02 jet at rates up to 2.0 kHz were carried out. Analysis of the data from these studies include mean and rms profiles, probability density functions (pdf's), power spectral density functions, autocorrelation functions, cross correlation functions, and determinations of skewness and kurtosis in the pdf's and the C02 fluctuations.

The aim of this work is to describe the physics-based simulation model of a custom 3D range laser scanner together with generic interface which offers the possibility for client applications to seamlessly interact with instances of the physical and virtual 3D range scanner. The physics-based virtual model of the 3D range scanner is realized in rigid body dynamics environment provided by Open Dynamics Engine (ODE) library. In order to simulate the stepper motor used in the real scanner, the joints are virtually constrained and motorized with the parameters obtained from real device. For rays modeling the ray-cast method is used. The incidence angle and the surface properties of the object hit by the rays are also taken into the consideration. The sensor noise that represents the uncertainty of the measure is also taken into account. We have also tried to mimic the internal sensor control logic. In order to verify the developed model and the interface architecture, a simple client application for 3D data acquisition is developed and connected through the same interface to both “physical” and “virtual” device. The results of the evaluation are also reported and discussed.

The topics covered include the following: (1) CO2 laser kinetics modeling; (2) gas lifetimes in pulsed CO2 lasers; (3) frequency chirp and laser pulse spectral analysis; (4) LAWS A' Design Study; and (5) discharge circuit components for LAWS. The appendices include LAWS Memos, computer modeling of pulsed CO2 lasers for lidar applications, discharge circuit considerations for pulsed CO2 lidars, and presentation made at the Code RC Review.

The Free Electron Laser (FEL) and Rail Gun are electric weapons which will require a significant amount of stored energy for operation. These types of weapons are ideal for use onboard an all-electric ship. An investigation is made of the effects these weapons will have on a proposed electrical system architecture using simulation modeling. Specifically, this thesis identifies possible design weaknesses and shows where further research and modeling is needed in order to ensure the proper integration of these electric weapons onboard an all-electric ship. The integration of these electric weapon systems with the power systems on electric ships will have an impact on naval operations. Several scenarios concerning specific naval missions are investigated using simulation software to understand the impact and limitations on the electric system using these new electric weapons.

Currently, there is disagreement among existing methods of determining atmospheric water vapor concentration at dew-points below -40 C. A major source of error is wall effects which result from the necessity of bringing samples into the instruments. All of these instruments also have response times on the order of seconds. NASA Langley is developing a water vapor sensor which utilizes the absorption of the infrared radiation produced by a diode laser to estimate water vapor concentration. The laser beam is directed through an aircraft window to a retroreflector located on an engine. The reflected beam is detected by an infrared detector located near the laser. To maximize signal to noise, derivative signals are analyzed. By measuring the 2f/DC signal and correcting for ambient temperature, atmospheric pressure and air speed (which results in a Doppler shifting of the laser beam), the water vapor concentration can be retrieved. Since this is an in situ measurement there are no wall effects and measurements can be made at a rate of more than 20 per second. This allows small spatial variations of water vapor to be studied. In order to study the sensitivity of the instrument to variations in temperature and air speed, a computer program which generated the 2f, 3f, 4f, DC and 2f/DC signals of the instrument as a function of temperature, pressure and air speed was written. This model was used to determine the effect of errors in measurement of the temperature and air speed on the measured water vapor concentration. Future studies will quantify the effect of pressure measurement errors, which are expected to be very small. As a result of these studied, a retrieval algorithm has been formulated, and will be applied to data taken during the PEM-West atmospheric science field mission. Spectroscopic studies of the water vapor line used by the instrument will be used to refine this algorithm. To prepare for these studies, several lasers have been studied to determine their output frequency range and power.

A computational plasma aerodynamics model is developed to study the performance of a laser propelled Lightcraft. The computational methodology is based on a time-accurate, three-dimensional, finite-difference, chemically reacting, unstructured grid, pressure-based formulation. The underlying physics are added and tested systematically using a building-block approach. The physics modeled include non-equilibrium thermodynamics, non-equilibrium air-plasma finite-rate kinetics, specular ray tracing, laser beam energy absorption and refraction by plasma, non-equilibrium plasma radiation, and plasma resonance. A series of transient computations are performed at several laser pulse energy levels and the simulated physics are discussed and compared with those of tests and literatures. The predicted coupling coefficients for the Lightcraft compared reasonably well with those of tests conducted on a pendulum apparatus.

This article is from Optics Express , volume 18 . Abstract To better understand the limitations of high-resolution adaptive optics scanning laser ophthalmoscopy (AOSLO), we describe an imaging model that examines the smallest cone photoreceptors in the fovea of normal human subjects and analyze how different factors contribute to their resolution. The model includes basic optical factors such as wavelength and pupil size, and defines limits caused by source coherence which are specific to the AOSLO imaging modality as well as foveal cone structure. The details of the model, its implications for imaging, and potential techniques to circumvent the limitations are discussed in this paper.

The aim of this work is to describe the physics-based simulation model of a custom 3D range laser scanner together with generic interface which offers the possibility for client applications to seamlessly interact with instances of the physical and virtual 3D range scanner. The physics-based virtual model of the 3D range scanner is realized in rigid body dynamics environment provided by Open Dynamics Engine (ODE) library. In order to simulate the stepper motor used in the real scanner, the joints are virtually constrained and motorized with the parameters obtained from real device. For rays modeling the ray-cast method is used. The incidence angle and the surface properties of the object hit by the rays are also taken into the consideration. The sensor noise that represents the uncertainty of the measure is also taken into account. We have also tried to mimic the internal sensor control logic. In order to verify the developed model and the interface architecture, a simple client application for 3D data acquisition is developed and connected through the same interface to both “physical” and “virtual” device. The results of the evaluation are also reported and discussed.

The production of electron beam of high brightness and low emittance is critical for a variety of scientific and technological applications such as high power vacuum coherent radiation source such as microwave sources, free electron lasers (FEL) and electron imaging system. The focus is to have a robust cathode using field emission mechanism based on the process of electron tunneling from a metal's surface, which is also known as Fowler Nordheim (FN) law. When a laser is used to excite the electron emission, the mechanism is known as the Fowler- Dubridge (FD) model. In this project, we aim to improve the basic of fundamental understandings of the electron emission process (related to FN and FD models) by developing multi-dimensional (2D or 3D) models.

A theoretical model is developed for the interaction of intense femtosecond laser pulses with solid targets on the basis of the two-temperature equation of state for an irradiated substance. It allows the description of the dynamics of the plasma formation and expansion. Comparison of available experimental data on the amplitude and phase of the complex reflection coefficient of aluminum with the simulation results provides new information on the transport coefficients and absorption capacity of the strongly coupled Al plasma over a wide range of temperatures and pressures.

This report is a summary of research activities funded by AFOSR Lab Task 13RXCOR. An integrated computational materials science and engineering (ICMSE) approach was used to investigate the role of fiber-matrix interfaces in controlling optical and thermal energy flow in structural composite materials subject to high energy laser irradiation. Modeling tools, including molecular dynamics and finite elements methods, were used to characterize optical and thermal transport at multiple length scales spanning from nanometers to millimeters. Advanced experimental characterization techniques were used to parameterize and validate these models. Two new experimental techniques were developed at AFRL as part of this project: lateral thermal transport measurements using scanning thermal microscopy (SThM), and microscale temperature sensing via gold nanorods. Modeling and experimental techniques are explained, and important considerations for future work are outlined. Peer-reviewed articles containing detailed results and analysis are included as an appendix.

A novel breathing sphere model was developed in order to make microscopic molecular dynamics simulations tractable for laser ablation. The results of the simulations have allowed us to distinguish between desorption and ablation, predict velocity distributions of ablated particles, predict the fluence dependence of the ablation yield, explain the forward peaked angular distributions and predict the acoustic pressure wave characteristics. Numerous favorable comparisons with experimental data have been made.

Up-to-date CO2 lasers are widely used in laser treatment of materials (drilling, welting, cutting). Technical achievements of laser methods both in Russia and abroad are limited and have been applied only for some types of ferrous metals until now (iron, steel, stainless steel, electrical steel). A number of works, cannot describe satisfactory the processes of gas-laser metal cutting, and this fact implies consideration of a great number of complex and interrelated processes.

A computational model for the propagation of laser radiation within cylindrical geometry is developed in C++. This model employs a finite difference technique to model the Pad approximant of the light propagation (Helmholtz) operator to solve the scalar Helmholtz equation obtained using the slowly-varying envelope formalism. This technique is capable of handling wide-angle propagation and refractive index variation while still maintaining numerical speed and simplicity. In addition, this model uses a non-linear map from the infinite physical space to a finite computational space to avoid spurious reflections from the computational window edge and improve computational efficiency. Also, the model depends solely on the spatial refractive index and hence can be coupled in a time-slicing scheme to an optical thermal model that can include linear and non-linear optical effects as well as capture thermal lensing. As an application of the model developed here, predicted irradiance at the retina of laser light incident on the human eye could be used to establish new maximum permissible exposure (MPE) limits.

This work dealt with the theoretical modeling and computation of photoionization, photoexcitation, radiative decay and radiative recombination processes for multielectron atoms and ions in plasmas. Such atomic processes lead to and influence lasing in x-ray lasers operating both in the soft and hard x ray regions. This research utilized a two-component, finite temperature, self consistent density functional method and demonstrated that this method is applicable for arbitrary plasma density and temperature and is capable of accurately treating multielectron ions of arbitrary Z. Electron collisional ionization and excitation processes were investigated. These processes are an important mechanism through which population inversion of ionic energy levels lead to lasing in the soft x-ray region. Previously theoretical calculations utilizing a semi-classical impact approximation have been performed. In many cases such a method is inadequate. Computations were carried out by electron impact ionization and excitation cross-sections and rate coefficients utilizing the distorted wave with exchange method. Keywords: Photoionization, Photoexcitation, Plasmas, Multielectron, Atoms.

The optical forces in optical tweezers can be robustly modeled over a broad range of parameters using generalsed Lorenz-Mie theory. We describe the procedure, and show how the combination of experimental measurement of properties of the trap coupled with computational modeling, can allow unknown parameters of the particle - in this case, the refractive index - to be determined.

We describe how a new framework for coupling a full-PIC algorithm with a reduced PIC algorithm has been implemented into the code OSIRIS. We show that OSIRIS with this new hybrid-PIC algorithm can efficiently and accurately model high energy density scenarios such as ion acceleration in laser-solid interactions and fast ignition of fusion targets. We model for the first time the full density range of a fast ignition target in a fully self-consistent hybrid-PIC simulation, illustrating the possibility of stopping the laser generated electron flux at the core region with relatively high efficiencies. Computational speedups greater than 1000 times are demonstrated, opening the way for full-scale multi-dimensional modeling of high energy density scenarios and for the guiding of future experiments.

We test numerical filamentation models against experimental data about the peak intensity and filament density in laser filaments. We show that the consideration of the higher-order Kerr effect (HOKE) improves the quantitative agreement without the need of adjustable parameters.

This thesis addresses two primary concerns relating to Directed Energy (DE) models and tests: need for more use of Design of Experiment (DOE) in structuring DE models and tests, and lack of modeling atmospheric variability in High Energy Laser (HEL) weapon system propagation models and tests. To address these concerns we use a DOE factorial design to capture main, interaction, and non-linear effects between modeled weapon design and environmental factors in a well defined simulated Air-to-Ground HEL engagement scenario. The scenario modeled considers a B1-B aircraft in the 2022 timeframe equipped with an HEL weapon, irradiating a ground target from 30K feet altitude. The High Energy Laser End-to-End Operational Simulation (HELEEOS), developed by the AFIT Center for Directed Energy (CDE), is used to model HEL propagation. Atmospheric variability is incorporated by using input from the Laser Environmental Effects Definition and Reference (LEEDER) model based on randomly selected daily meteorological data (METAR) for a specific geographic location. Results clearly indicate the practical significance of a number of HEL weapon design and environmental factors, to include a number of previously unidentified interactions and non-linear effects, on the final energy delivered to a target for our modeled scenario.

Flow in a pressurized, vapor condensation (PVC) boron nitride nanotube (BNNT) production rig is modeled. A laser provides a thermal energy source to the tip of a boron ber bundle in a high pressure nitrogen chamber causing a plume of boron-rich gas to rise. The buoyancy driven flow is modeled as a mixture of thermally perfect gases (B, B2, N, N2, BN) in either thermochemical equilibrium or chemical nonequilibrium assuming steady-state melt and vaporization from a 1 mm radius spot at the axis of an axisymmetric chamber. The simulation is intended to define the macroscopic thermochemical environment from which boron-rich species, including nanotubes, condense out of the plume. Simulations indicate a high temperature environment (T > 4400K) for elevated pressures within 1 mm of the surface sufficient to dissociate molecular nitrogen and form BN at the base of the plume. Modifications to Program LAURA, a finite-volume based solver for hypersonic flows including coupled radiation and ablation, are described to enable this simulation. Simulations indicate that high pressure synthesis conditions enable formation of BN vapor in the plume that may serve to enhance formation of exceptionally long nanotubes in the PVC process.

Flow in a pressurized, vapor condensation (PVC) boron nitride nanotube (BNNT) production rig is modeled. A laser provides a thermal energy source to the tip of a boron ber bundle in a high pressure nitrogen chamber causing a plume of boron-rich gas to rise. The buoyancy driven flow is modeled as a mixture of thermally perfect gases (B, B2, N, N2, BN) in either thermochemical equilibrium or chemical nonequilibrium assuming steady-state melt and vaporization from a 1 mm radius spot at the axis of an axisymmetric chamber. The simulation is intended to define the macroscopic thermochemical environment from which boron-rich species, including nanotubes, condense out of the plume. Simulations indicate a high temperature environment (T > 4400K) for elevated pressures within 1 mm of the surface sufficient to dissociate molecular nitrogen and form BN at the base of the plume. Modifications to Program LAURA, a finite-volume based solver for hypersonic flows including coupled radiation and ablation, are described to enable this simulation. Simulations indicate that high pressure synthesis conditions enable formation of BN vapor in the plume that may serve to enhance formation of exceptionally long nanotubes in the PVC process.

The results of a survey of pressure-broadening data in the literature, pertaining to species present in H2-F2 chemical lasers are described. Pressure-broadened linewidths of the HF vibration/rotation transitions were found to depend strongly on the vibrational and rotational quantum numbers, as well as on the perturbing species. The experimental data were incorporated into a rate equation model of the pulsed H2-F2 laser; where experimental data were unavailable, theoretical values were used. The calculations made from this model demonstrate the importance of including such detailed pressure-broadening information. Recent experimental results of Kwok and Cohen for HF V yeilds R, T deactivation were also included in the model and were taken to be a multiquantum process. Comparisons of model predictions for pulse energy and pulse duration with several atmospheric-pressure laser measurements showed good agreement. (Author)

This thesis developed a finite element solution of the Schrodinger wave equation. This technique is used by a computer program to calculate the energy levels and wave functions of a diatomic molecular for a particular potential energy model. The potential energy model is a function of a set of parameters which a non-linear minimization routine varies before solving the wave equation. This is done in an iterative manner until the calculated energy levels agree in a least squares sense with the observed energy levels. Then the transition probabilities (Franck-Condon factors) between the wave functions are calculated by another program developed for this thesis. Finally, two programs were written to determine the energy levels observed in spectroscopic data. One uses Dunham coefficients and the Dunham equation while the second uses a least square fit to the data directly. The four programs were tested and appear to work correctly. The numeric solutions were compared with the analytic solutions of the single harmonic oscillator. Originator-supplied keywords include: Franck-Condon factors, Diatomic molecules, Molecular vibration, Schrodinger equation, and Numerical analysis.