Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

NASA Astrophysics Data System (ADS)

Hansen, E. C.; Barnak, D. H.; Betti, R.; Campbell, E. M.; Chang, P.-Y.; Davies, J. R.; Glebov, V. Yu; Knauer, J. P.; Peebles, J.; Regan, S. P.; Sefkow, A. B.

2018-05-01

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1D code LILAC was used to model the central region of the implosion, and results were compared to 2D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysis shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.

Computational Simulation of Thermal and Spattering Phenomena and Microstructure in Selective Laser Melting of Inconel 625

NASA Astrophysics Data System (ADS)

Özel, Tuğrul; Arısoy, Yiğit M.; Criales, Luis E.

Computational modelling of Laser Powder Bed Fusion (L-PBF) processes such as Selective laser Melting (SLM) can reveal information that is hard to obtain or unobtainable by in-situ experimental measurements. A 3D thermal field that is not visible by the thermal camera can be obtained by solving the 3D heat transfer problem. Furthermore, microstructural modelling can be used to predict the quality and mechanical properties of the product. In this paper, a nonlinear 3D Finite Element Method based computational code is developed to simulate the SLM process with different process parameters such as laser power and scan velocity. The code is further improved by utilizing an in-situ thermal camera recording to predict spattering which is in turn included as a stochastic heat loss. Then, thermal gradients extracted from the simulations applied to predict growth directions in the resulting microstructure.

Modeling multi-GeV class laser-plasma accelerators with INF&RNO

NASA Astrophysics Data System (ADS)

Benedetti, Carlo; Schroeder, Carl; Bulanov, Stepan; Geddes, Cameron; Esarey, Eric; Leemans, Wim

2016-10-01

Laser plasma accelerators (LPAs) can produce accelerating gradients on the order of tens to hundreds of GV/m, making them attractive as compact particle accelerators for radiation production or as drivers for future high-energy colliders. Understanding and optimizing the performance of LPAs requires detailed numerical modeling of the nonlinear laser-plasma interaction. We present simulation results, obtained with the computationally efficient, PIC/fluid code INF&RNO (INtegrated Fluid & paRticle simulatioN cOde), concerning present (multi-GeV stages) and future (10 GeV stages) LPA experiments performed with the BELLA PW laser system at LBNL. In particular, we will illustrate the issues related to the guiding of a high-intensity, short-pulse, laser when a realistic description for both the laser driver and the background plasma is adopted. Work Supported by the U.S. Department of Energy under contract No. DE-AC02-05CH11231.

Algorithm for loading shot noise microbunching in multi-dimensional, free-electron laser simulation codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fawley, William M.

We discuss the underlying reasoning behind and the details of the numerical algorithm used in the GINGER free-electron laser(FEL) simulation code to load the initial shot noise microbunching on the electron beam. In particular, we point out that there are some additional subtleties which must be followed for multi-dimensional codes which are not necessary for one-dimensional formulations. Moreover, requiring that the higher harmonics of the microbunching also be properly initialized with the correct statistics leads to additional complexities. We present some numerical results including the predicted incoherent, spontaneous emission as tests of the shot noise algorithm's correctness.

LATIS3D: The Goal Standard for Laser-Tissue-Interaction Modeling

NASA Astrophysics Data System (ADS)

London, R. A.; Makarewicz, A. M.; Kim, B. M.; Gentile, N. A.; Yang, T. Y. B.

2000-03-01

The goal of this LDRD project has been to create LATIS3D-the world's premier computer program for laser-tissue interaction modeling. The development was based on recent experience with the 2D LATIS code and the ASCI code, KULL. With LATIS3D, important applications in laser medical therapy were researched including dynamical calculations of tissue emulsification and ablation, photothermal therapy, and photon transport for photodynamic therapy. This project also enhanced LLNL's core competency in laser-matter interactions and high-energy-density physics by pushing simulation codes into new parameter regimes and by attracting external expertise. This will benefit both existing LLNL programs such as ICF and SBSS and emerging programs in medical technology and other laser applications. The purpose of this project was to develop and apply a computer program for laser-tissue interaction modeling to aid in the development of new instruments and procedures in laser medicine.

Simulation of Laser Cooling and Trapping in Engineering Applications

NASA Technical Reports Server (NTRS)

Ramirez-Serrano, Jaime; Kohel, James; Thompson, Robert; Yu, Nan; Lunblad, Nathan

2005-01-01

An advanced computer code is undergoing development for numerically simulating laser cooling and trapping of large numbers of atoms. The code is expected to be useful in practical engineering applications and to contribute to understanding of the roles that light, atomic collisions, background pressure, and numbers of particles play in experiments using laser-cooled and -trapped atoms. The code is based on semiclassical theories of the forces exerted on atoms by magnetic and optical fields. Whereas computer codes developed previously for the same purpose account for only a few physical mechanisms, this code incorporates many more physical mechanisms (including atomic collisions, sub-Doppler cooling mechanisms, Stark and Zeeman energy shifts, gravitation, and evanescent-wave phenomena) that affect laser-matter interactions and the cooling of atoms to submillikelvin temperatures. Moreover, whereas the prior codes can simulate the interactions of at most a few atoms with a resonant light field, the number of atoms that can be included in a simulation by the present code is limited only by computer memory. Hence, the present code represents more nearly completely the complex physics involved when using laser-cooled and -trapped atoms in engineering applications. Another advantage that the code incorporates is the possibility to analyze the interaction between cold atoms of different atomic number. Some properties that cold atoms of different atomic species have, like cross sections and the particular excited states they can occupy when interacting with each other and light fields, play important roles not yet completely understood in the new experiments that are under way in laboratories worldwide to form ultracold molecules. Other research efforts use cold atoms as holders of quantum information, and more recent developments in cavity quantum electrodynamics also use ultracold atoms to explore and expand new information-technology ideas. These experiments give a hint on the wide range of applications and technology developments that can be tackled using cold atoms and light fields. From more precise atomic clocks and gravity sensors to the development of quantum computers, there will be a need to completely understand the whole ensemble of physical mechanisms that play a role in the development of such technologies. The code also permits the study of the dynamic and steady-state operations of technologies that use cold atoms. The physical characteristics of lasers and fields can be time-controlled to give a realistic simulation of the processes involved such that the design process can determine the best control features to use. It is expected that with the features incorporated into the code it will become a tool for the useful application of ultracold atoms in engineering applications. Currently, the software is being used for the analysis and understanding of simple experiments using cold atoms, and for the design of a modular compact source of cold atoms to be used in future research and development projects. The results so far indicate that the code is a useful design instrument that shows good agreement with experimental measurements (see figure), and a Windows-based user-friendly interface is also under development.

Diagnostics of Particles emitted from a Laser generated Plasma: Experimental Data and Simulations

NASA Astrophysics Data System (ADS)

Costa, Giuseppe; Torrisi, Lorenzo

2018-01-01

The charge particle emission form laser-generated plasma was studied experimentally and theoretically using the COMSOL simulation code. The particle acceleration was investigated using two lasers at two different regimes. A Nd:YAG laser, with 3 ns pulse duration and 1010 W/cm2 intensity, when focused on solid target produces a non-equilibrium plasma with average temperature of about 30-50 eV. An Iodine laser with 300 ps pulse duration and 1016 W/cm2 intensity produces plasmas with average temperatures of the order of tens keV. In both cases charge separation occurs and ions and electrons are accelerated at energies of the order of 200 eV and 1 MeV per charge state in the two cases, respectively. The simulation program permits to plot the charge particle trajectories from plasma source in vacuum indicating how they can be deflected by magnetic and electrical fields. The simulation code can be employed to realize suitable permanent magnets and solenoids to deflect ions toward a secondary target or detectors, to focalize ions and electrons, to realize electron traps able to provide significant ion acceleration and to realize efficient spectrometers. In particular it was applied to the study two Thomson parabola spectrometers able to detect ions at low and at high laser intensities. The comparisons between measurements and simulation is presented and discussed.

Kinetic modeling of x-ray laser-driven solid Al plasmas via particle-in-cell simulation

NASA Astrophysics Data System (ADS)

Royle, R.; Sentoku, Y.; Mancini, R. C.; Paraschiv, I.; Johzaki, T.

2017-06-01

Solid-density plasmas driven by intense x-ray free-electron laser (XFEL) radiation are seeded by sources of nonthermal photoelectrons and Auger electrons that ionize and heat the target via collisions. Simulation codes that are commonly used to model such plasmas, such as collisional-radiative (CR) codes, typically assume a Maxwellian distribution and thus instantaneous thermalization of the source electrons. In this study, we present a detailed description and initial applications of a collisional particle-in-cell code, picls, that has been extended with a self-consistent radiation transport model and Monte Carlo models for photoionization and K L L Auger ionization, enabling the fully kinetic simulation of XFEL-driven plasmas. The code is used to simulate two experiments previously performed at the Linac Coherent Light Source investigating XFEL-driven solid-density Al plasmas. It is shown that picls-simulated pulse transmissions using the Ecker-Kröll continuum-lowering model agree much better with measurements than do simulations using the Stewart-Pyatt model. Good quantitative agreement is also found between the time-dependent picls results and those of analogous simulations by the CR code scfly, which was used in the analysis of the experiments to accurately reproduce the observed K α emissions and pulse transmissions. Finally, it is shown that the effects of the nonthermal electrons are negligible for the conditions of the particular experiments under investigation.

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, E. C.; Barnak, D. H.; Betti, R.

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1-D code LILAC was used to model the central region of the implosion, and results were compared to 2-D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysismore » shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.« less

Measuring implosion velocities in experiments and simulations of laser-driven cylindrical implosions on the OMEGA laser

DOE PAGES

Hansen, E. C.; Barnak, D. H.; Betti, R.; ...

2018-04-04

Laser-driven magnetized liner inertial fusion (MagLIF) on OMEGA involves cylindrical implosions, a preheat beam, and an applied magnetic field. Initial experiments excluded the preheat beam and magnetic field to better characterize the implosion. X-ray self-emission as measured by framing cameras was used to determine the shell trajectory. The 1-D code LILAC was used to model the central region of the implosion, and results were compared to 2-D simulations from the HYDRA code. Post-processing of simulation output with SPECT3D and Yorick produced synthetic x-ray images that were used to compare the simulation results with the x-ray framing camera data. Quantitative analysismore » shows that higher measured neutron yields correlate with higher implosion velocities. The future goal is to further analyze the x-ray images to characterize the uniformity of the implosions and apply these analysis techniques to integrated laser-driven MagLIF shots to better understand the effects of preheat and the magnetic field.« less

Laser beam coupling with capillary discharge plasma for laser wakefield acceleration applications

NASA Astrophysics Data System (ADS)

Bagdasarov, G. A.; Sasorov, P. V.; Gasilov, V. A.; Boldarev, A. S.; Olkhovskaya, O. G.; Benedetti, C.; Bulanov, S. S.; Gonsalves, A.; Mao, H.-S.; Schroeder, C. B.; van Tilborg, J.; Esarey, E.; Leemans, W. P.; Levato, T.; Margarone, D.; Korn, G.

2017-08-01

One of the most robust methods, demonstrated to date, of accelerating electron beams by laser-plasma sources is the utilization of plasma channels generated by the capillary discharges. Although the spatial structure of the installation is simple in principle, there may be some important effects caused by the open ends of the capillary, by the supplying channels etc., which require a detailed 3D modeling of the processes. In the present work, such simulations are performed using the code MARPLE. First, the process of capillary filling with cold hydrogen before the discharge is fired, through the side supply channels is simulated. Second, the simulation of the capillary discharge is performed with the goal to obtain a time-dependent spatial distribution of the electron density near the open ends of the capillary as well as inside the capillary. Finally, to evaluate the effectiveness of the beam coupling with the channeling plasma wave guide and of the electron acceleration, modeling of the laser-plasma interaction was performed with the code INF&RNO.

FDTD method for laser absorption in metals for large scale problems.

PubMed

Deng, Chun; Ki, Hyungson

2013-10-21

The FDTD method has been successfully used for many electromagnetic problems, but its application to laser material processing has been limited because even a several-millimeter domain requires a prohibitively large number of grids. In this article, we present a novel FDTD method for simulating large-scale laser beam absorption problems, especially for metals, by enlarging laser wavelength while maintaining the material's reflection characteristics. For validation purposes, the proposed method has been tested with in-house FDTD codes to simulate p-, s-, and circularly polarized 1.06 μm irradiation on Fe and Sn targets, and the simulation results are in good agreement with theoretical predictions.

The numerical simulation tool for the MAORY multiconjugate adaptive optics system

NASA Astrophysics Data System (ADS)

Arcidiacono, C.; Schreiber, L.; Bregoli, G.; Diolaiti, E.; Foppiani, I.; Agapito, G.; Puglisi, A.; Xompero, M.; Oberti, S.; Cosentino, G.; Lombini, M.; Butler, R. C.; Ciliegi, P.; Cortecchia, F.; Patti, M.; Esposito, S.; Feautrier, P.

2016-07-01

The Multiconjugate Adaptive Optics RelaY (MAORY) is and Adaptive Optics module to be mounted on the ESO European-Extremely Large Telescope (E-ELT). It is an hybrid Natural and Laser Guide System that will perform the correction of the atmospheric turbulence volume above the telescope feeding the Multi-AO Imaging Camera for Deep Observations Near Infrared spectro-imager (MICADO). We developed an end-to-end Monte- Carlo adaptive optics simulation tool to investigate the performance of a the MAORY and the calibration, acquisition, operation strategies. MAORY will implement Multiconjugate Adaptive Optics combining Laser Guide Stars (LGS) and Natural Guide Stars (NGS) measurements. The simulation tool implement the various aspect of the MAORY in an end to end fashion. The code has been developed using IDL and use libraries in C++ and CUDA for efficiency improvements. Here we recall the code architecture, we describe the modeled instrument components and the control strategies implemented in the code.

Load management strategy for Particle-In-Cell simulations in high energy particle acceleration

NASA Astrophysics Data System (ADS)

Beck, A.; Frederiksen, J. T.; Dérouillat, J.

2016-09-01

In the wake of the intense effort made for the experimental CILEX project, numerical simulation campaigns have been carried out in order to finalize the design of the facility and to identify optimal laser and plasma parameters. These simulations bring, of course, important insight into the fundamental physics at play. As a by-product, they also characterize the quality of our theoretical and numerical models. In this paper, we compare the results given by different codes and point out algorithmic limitations both in terms of physical accuracy and computational performances. These limitations are illustrated in the context of electron laser wakefield acceleration (LWFA). The main limitation we identify in state-of-the-art Particle-In-Cell (PIC) codes is computational load imbalance. We propose an innovative algorithm to deal with this specific issue as well as milestones towards a modern, accurate high-performance PIC code for high energy particle acceleration.

Simulations of the plasma dynamics in high-current ion diodes

NASA Astrophysics Data System (ADS)

Boine-Frankenheim, O.; Pointon, T. D.; Mehlhorn, T. A.

Our time-implicit fluid/Particle-In-Cell (PIC) code DYNAID [1]is applied to problems relevant for applied- B ion diode operation. We present simulations of the laser ion source, which will soon be employed on the SABRE accelerator at SNL, and of the dynamics of the anode source plasma in the applied electric and magnetic fields. DYNAID is still a test-bed for a higher-dimensional simulation code. Nevertheless, the code can already give new theoretical insight into the dynamics of plasmas in pulsed power devices.

Modeling Laser-Driven Laboratory Astrophysics Experiments Using the CRASH Code

NASA Astrophysics Data System (ADS)

Grosskopf, Michael; Keiter, P.; Kuranz, C. C.; Malamud, G.; Trantham, M.; Drake, R.

2013-06-01

Laser-driven, laboratory astrophysics experiments can provide important insight into the physical processes relevant to astrophysical systems. The radiation hydrodynamics code developed by the Center for Radiative Shock Hydrodynamics (CRASH) at the University of Michigan has been used to model experimental designs for high-energy-density laboratory astrophysics campaigns on OMEGA and other high-energy laser facilities. This code is an Eulerian, block-adaptive AMR hydrodynamics code with implicit multigroup radiation transport and electron heat conduction. The CRASH model has been used on many applications including: radiative shocks, Kelvin-Helmholtz and Rayleigh-Taylor experiments on the OMEGA laser; as well as laser-driven ablative plumes in experiments by the Astrophysical Collisionless Shocks Experiments with Lasers (ACSEL) collaboration. We report a series of results with the CRASH code in support of design work for upcoming high-energy-density physics experiments, as well as comparison between existing experimental data and simulation results. This work is funded by the Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616, by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-FG52-09NA29548, and by the National Laser User Facility Program, grant number DE-NA0000850.

Computationally efficient methods for modelling laser wakefield acceleration in the blowout regime

NASA Astrophysics Data System (ADS)

Cowan, B. M.; Kalmykov, S. Y.; Beck, A.; Davoine, X.; Bunkers, K.; Lifschitz, A. F.; Lefebvre, E.; Bruhwiler, D. L.; Shadwick, B. A.; Umstadter, D. P.; Umstadter

2012-08-01

Electron self-injection and acceleration until dephasing in the blowout regime is studied for a set of initial conditions typical of recent experiments with 100-terawatt-class lasers. Two different approaches to computationally efficient, fully explicit, 3D particle-in-cell modelling are examined. First, the Cartesian code vorpal (Nieter, C. and Cary, J. R. 2004 VORPAL: a versatile plasma simulation code. J. Comput. Phys. 196, 538) using a perfect-dispersion electromagnetic solver precisely describes the laser pulse and bubble dynamics, taking advantage of coarser resolution in the propagation direction, with a proportionally larger time step. Using third-order splines for macroparticles helps suppress the sampling noise while keeping the usage of computational resources modest. The second way to reduce the simulation load is using reduced-geometry codes. In our case, the quasi-cylindrical code calder-circ (Lifschitz, A. F. et al. 2009 Particle-in-cell modelling of laser-plasma interaction using Fourier decomposition. J. Comput. Phys. 228(5), 1803-1814) uses decomposition of fields and currents into a set of poloidal modes, while the macroparticles move in the Cartesian 3D space. Cylindrical symmetry of the interaction allows using just two modes, reducing the computational load to roughly that of a planar Cartesian simulation while preserving the 3D nature of the interaction. This significant economy of resources allows using fine resolution in the direction of propagation and a small time step, making numerical dispersion vanishingly small, together with a large number of particles per cell, enabling good particle statistics. Quantitative agreement of two simulations indicates that these are free of numerical artefacts. Both approaches thus retrieve the physically correct evolution of the plasma bubble, recovering the intrinsic connection of electron self-injection to the nonlinear optical evolution of the driver.

Kinetic Monte Carlo simulations for transient thermal fields: Computational methodology and application to the submicrosecond laser processes in implanted silicon.

PubMed

Fisicaro, G; Pelaz, L; Lopez, P; La Magna, A

2012-09-01

Pulsed laser irradiation of damaged solids promotes ultrafast nonequilibrium kinetics, on the submicrosecond scale, leading to microscopic modifications of the material state. Reliable theoretical predictions of this evolution can be achieved only by simulating particle interactions in the presence of large and transient gradients of the thermal field. We propose a kinetic Monte Carlo (KMC) method for the simulation of damaged systems in the extremely far-from-equilibrium conditions caused by the laser irradiation. The reference systems are nonideal crystals containing point defect excesses, an order of magnitude larger than the equilibrium density, due to a preirradiation ion implantation process. The thermal and, eventual, melting problem is solved within the phase-field methodology, and the numerical solutions for the space- and time-dependent thermal field were then dynamically coupled to the KMC code. The formalism, implementation, and related tests of our computational code are discussed in detail. As an application example we analyze the evolution of the defect system caused by P ion implantation in Si under nanosecond pulsed irradiation. The simulation results suggest a significant annihilation of the implantation damage which can be well controlled by the laser fluence.

co2amp: A software program for modeling the dynamics of ultrashort pulses in optical systems with CO 2 amplifiers

DOE PAGES

Polyanskiy, Mikhail N.

2015-01-01

We describe a computer code for simulating the amplification of ultrashort mid-infrared laser pulses in CO 2 amplifiers and their propagation through arbitrary optical systems. This code is based on a comprehensive model that includes an accurate consideration of the CO 2 active medium and a physical optics propagation algorithm, and takes into account the interaction of the laser pulse with the material of the optical elements. Finally, the application of the code for optimizing an isotopic regenerative amplifier is described.

Implementation of Hydrodynamic Simulation Code in Shock Experiment Design for Alkali Metals

NASA Astrophysics Data System (ADS)

Coleman, A. L.; Briggs, R.; Gorman, M. G.; Ali, S.; Lazicki, A.; Swift, D. C.; Stubley, P. G.; McBride, E. E.; Collins, G.; Wark, J. S.; McMahon, M. I.

2017-10-01

Shock compression techniques enable the investigation of extreme P-T states. In order to probe off-Hugoniot regions of P-T space, target makeup and laser pulse parameters must be carefully designed. HYADES is a hydrodynamic simulation code which has been successfully utilised to simulate shock compression events and refine the experimental parameters required in order to explore new P-T states in alkali metals. Here we describe simulations and experiments on potassium, along with the techniques required to access off-Hugoniot states.

Capturing atmospheric effects on 3D millimeter wave radar propagation patterns

NASA Astrophysics Data System (ADS)

Cook, Richard D.; Fiorino, Steven T.; Keefer, Kevin J.; Stringer, Jeremy

2016-05-01

Traditional radar propagation modeling is done using a path transmittance with little to no input for weather and atmospheric conditions. As radar advances into the millimeter wave (MMW) regime, atmospheric effects such as attenuation and refraction become more pronounced than at traditional radar wavelengths. The DoD High Energy Laser Joint Technology Offices High Energy Laser End-to-End Operational Simulation (HELEEOS) in combination with the Laser Environmental Effects Definition and Reference (LEEDR) code have shown great promise simulating atmospheric effects on laser propagation. Indeed, the LEEDR radiative transfer code has been validated in the UV through RF. Our research attempts to apply these models to characterize the far field radar pattern in three dimensions as a signal propagates from an antenna towards a point in space. Furthermore, we do so using realistic three dimensional atmospheric profiles. The results from these simulations are compared to those from traditional radar propagation software packages. In summary, a fast running method has been investigated which can be incorporated into computational models to enhance understanding and prediction of MMW propagation through various atmospheric and weather conditions.

Simulation study of terahertz radiation generation by circularly polarized laser pulses propagating in axially magnetized plasma

NASA Astrophysics Data System (ADS)

Saroch, Akanksha; Jha, Pallavi

2017-12-01

This paper deals with a two-dimensional simulation study of terahertz radiation emission in the wake of circularly polarized laser pulses propagating in uniformly magnetized plasma, using the XOOPIC code. The external magnetic field is applied along the direction of propagation of the laser pulse. It is seen that linearly polarized terahertz radiation is emitted off-axis, along the propagation direction, in plasma. This emitted radiation is also seen to be transmitted in vacuum. Simulation studies reveal that no such radiation is generated on-axis for the given configuration.

PIC Simulation of Laser Plasma Interactions with Temporal Bandwidths

NASA Astrophysics Data System (ADS)

Tsung, Frank; Weaver, J.; Lehmberg, R.

2015-11-01

We are performing particle-in-cell simulations using the code OSIRIS to study the effects of laser plasma interactions in the presence of temperal bandwidths under conditions relevant to current and future shock ignition experiments on the NIKE laser. Our simulations show that, for sufficiently large bandwidth, the saturation level, and the distribution of hot electrons, can be effected by the addition of temporal bandwidths (which can be accomplished in experiments using smoothing techniques such as SSD or ISI). We will show that temporal bandwidth along play an important role in the control of LPI's in these lasers and discuss future directions. This work is conducted under the auspices of NRL.

Simulations of Foils Irradiated by Finite Laser Spots

NASA Astrophysics Data System (ADS)

Phillips, Lee

2006-10-01

Recent proposed designs (Obenchain et al., Phys. Plasmas 13 056320 (2006)) for direct-drive ICF targets for energy applications involve high implosion velocities with lower laser energies combined with higher irradiances. The use of high irradiances increases the likelihood of deleterious laser plasma instabilities (LPI) that may lead, for example, to the generation of fast electrons. The proposed use of a 248 nm KrF laser is expected to minimize LPI, and this is being studied by experiments on NRL's NIKE laser. Here we report on simulations aimed at designing and interpreting these experiments. The 2d simulations employ a modification of the FAST code to ablate plasma from CH and DT foils using laser pulses with arbitrary spatial and temporal profiles. These include the customary hypergaussian NIKE profile, gaussian profiles, and combinations of these. The simulations model the structure of the ablating plasma and the absorption of the laser light, providing parameters for design of the experiment and indicating where the relevant LPI (two-plasmon, Raman) may be observed.

Simulations of Large-Area Electron Beam Diodes

NASA Astrophysics Data System (ADS)

Swanekamp, S. B.; Friedman, M.; Ludeking, L.; Smithe, D.; Obenschain, S. P.

1999-11-01

Large area electron beam diodes are typically used to pump the amplifiers of KrF lasers. Simulations of large-area electron beam diodes using the particle-in-cell code MAGIC3D have shown the electron flow in the diode to be unstable. Since this instability can potentially produce a non-uniform current and energy distribution in the hibachi structure and lasing medium it can be detrimental to laser efficiency. These results are similar to simulations performed using the ISIS code.(M.E. Jones and V.A. Thomas, Proceedings of the 8^th) International Conference on High-Power Particle Beams, 665 (1990). We have identified the instability as the so called ``transit-time" instability(C.K. Birdsall and W.B. Bridges, Electrodynamics of Diode Regions), (Academic Press, New York, 1966).^,(T.M. Antonsen, W.H. Miner, E. Ott, and A.T. Drobot, Phys. Fluids 27), 1257 (1984). and have investigated the role of the applied magnetic field and diode geometry. Experiments are underway to characterize the instability on the Nike KrF laser system and will be compared to simulation. Also some possible ways to mitigate the instability will be presented.

Analysis of direct-drive capsule compression experiments on the Iskra-5 laser facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gus'kov, S. Yu.; Demchenko, N. N.; Zhidkov, N. V.

2010-09-15

We have analyzed and numerically simulated our experiments on the compression of DT-gas-filled glass capsules under irradiation by a small number of beams on the Iskra-5 facility (12 beams) at the second harmonic of an iodine laser ({lambda} = 0.66 {mu}m) for a laser pulse energy of 2 kJ and duration of 0.5 ns in the case of asymmetric irradiation and compression. Our simulations include the construction of a target illumination map and a histogram of the target surface illumination distribution; 1D capsule compression simulations based on the DIANA code corresponding to various target surface regions; and 2D compression simulationsmore » based on the NUTCY code corresponding to the illumination conditions. We have succeeded in reproducing the shape of the compressed region at the time of maximum compression and the reduction in neutron yield (compared to the 1D simulations) to the experimentally observed values. For the Iskra-5 conditions, we have considered targets that can provide a more symmetric compression and a higher neutron yield.« less

LIDAR pulse coding for high resolution range imaging at improved refresh rate.

PubMed

Kim, Gunzung; Park, Yongwan

2016-10-17

In this study, a light detection and ranging system (LIDAR) was designed that codes pixel location information in its laser pulses using the direct- sequence optical code division multiple access (DS-OCDMA) method in conjunction with a scanning-based microelectromechanical system (MEMS) mirror. This LIDAR can constantly measure the distance without idle listening time for the return of reflected waves because its laser pulses include pixel location information encoded by applying the DS-OCDMA. Therefore, this emits in each bearing direction without waiting for the reflected wave to return. The MEMS mirror is used to deflect and steer the coded laser pulses in the desired bearing direction. The receiver digitizes the received reflected pulses using a low-temperature-grown (LTG) indium gallium arsenide (InGaAs) based photoconductive antenna (PCA) and the time-to-digital converter (TDC) and demodulates them using the DS-OCDMA. When all of the reflected waves corresponding to the pixels forming a range image are received, the proposed LIDAR generates a point cloud based on the time-of-flight (ToF) of each reflected wave. The results of simulations performed on the proposed LIDAR are compared with simulations of existing LIDARs.

Systematic design and three-dimensional simulation of X-ray FEL oscillator for Shanghai Coherent Light Facility

NASA Astrophysics Data System (ADS)

Li, Kai; Deng, Haixiao

2018-07-01

The Shanghai Coherent Light Facility (SCLF) is a quasi-continuous wave hard X-ray free electron laser facility, which is currently under construction. Due to the high repetition rate and high-quality electron beams, it is straightforward to consider X-ray free electron laser oscillator (XFELO) operation for the SCLF. In this paper, the main processes for XFELO design, and parameter optimization of the undulator, X-ray cavity, and electron beam are described. A three-dimensional X-ray crystal Bragg diffraction code, named BRIGHT, was introduced for the first time, which can be combined with the GENESIS and OPC codes for the numerical simulations of the XFELO. The performance of the XFELO of the SCLF is investigated and optimized by theoretical analysis and numerical simulation.

Time-resolved x-ray spectra from laser-generated high-density plasmas

NASA Astrophysics Data System (ADS)

Andiel, U.; Eidmann, Klaus; Witte, Klaus-Juergen

2001-04-01

We focused frequency doubled ultra short laser pulses on solid C, F, Na and Al targets, K-shell emission was systematically investigated by time resolved spectroscopy using a sub-ps streak camera. A large number of laser shots can be accumulated when triggering the camera with an Auston switch system at very high temporal precision. The system provides an outstanding time resolution of 1.7ps accumulating thousands of laser shots. The time duration of the He-(alpha) K-shell resonance lines was observed in the range of (2-4)ps and shows a decrease with the atomic number. The experimental results are well reproduced by hydro code simulations post processed with an atomic kinetics code.

Opacplot2: Enabling tabulated EoS and opacity compatibility for HEDLP simulations with the FLASH code

NASA Astrophysics Data System (ADS)

Laune, Jordan; Tzeferacos, Petros; Feister, Scott; Fatenejad, Milad; Yurchak, Roman; Flocke, Norbert; Weide, Klaus; Lamb, Donald

2017-10-01

Thermodynamic and opacity properties of materials are necessary to accurately simulate laser-driven laboratory experiments. Such data are compiled in tabular format since the thermodynamic range that needs to be covered cannot be described with one single theoretical model. Moreover, tabulated data can be made available prior to runtime, reducing both compute cost and code complexity. This approach is employed by the FLASH code. Equation of state (EoS) and opacity data comes in various formats, matrix-layouts, and file-structures. We discuss recent developments on opacplot2, an open-source Python module that manipulates tabulated EoS and opacity data. We present software that builds upon opacplot2 and enables easy-to-use conversion of different table formats into the IONMIX format, the native tabular input used by FLASH. Our work enables FLASH users to take advantage of a wider range of accurate EoS and opacity tables in simulating HELP experiments at the National Laser User Facilities.

LIDAR TS for ITER core plasma. Part II: simultaneous two wavelength LIDAR TS

NASA Astrophysics Data System (ADS)

Gowers, C.; Nielsen, P.; Salzmann, H.

2017-12-01

We have shown recently, and in more detail at this conference (Salzmann et al) that the LIDAR approach to ITER core TS measurements requires only two mirrors in the inaccessible port plug area of the machine. This leads to simplified and robust alignment, lower risk of mirror damage by plasma contamination and much simpler calibration, compared with the awkward and vulnerable optical geometry of the conventional imaging TS approach, currently under development by ITER. In the present work we have extended the simulation code used previously to include the case of launching two laser pulses, of different wavelengths, simultaneously in LIDAR geometry. The aim of this approach is to broaden the choice of lasers available for the diagnostic. In the simulation code it is assumed that two short duration (300 ps) laser pulses of different wavelengths, from an Nd:YAG laser are launched through the plasma simultaneously. The temperature and density profiles are deduced in the usual way but from the resulting combined scattered signals in the different spectral channels of the single spectrometer. The spectral response and quantum efficiencies of the detectors used in the simulation are taken from catalogue data for commercially available Hamamatsu MCP-PMTs. The response times, gateability and tolerance to stray light levels of this type of photomultiplier have already been demonstrated in the JET LIDAR system and give sufficient spatial resolution to meet the ITER specification. Here we present the new simulation results from the code. They demonstrate that when the detectors are combined with this two laser, LIDAR approach, the full range of the specified ITER core plasma Te and ne can be measured with sufficient accuracy. So, with commercially available detectors and a simple modification of a Nd:YAG laser similar to that currently being used in the design of the conventional ITER core TS design mentioned above, the ITER requirements can be met.

Detailed numerical simulations of laser cooling processes

NASA Technical Reports Server (NTRS)

Ramirez-Serrano, J.; Kohel, J.; Thompson, R.; Yu, N.

2001-01-01

We developed a detailed semiclassical numerical code of the forces applied on atoms in optical and magnetic fields to increase the understanding of the different roles that light, atomic collisions, background pressure, and number of particles play in experiments with laser cooled and trapped atoms.

Validation of a Laser-Ray Package in an Eulerian Code

NASA Astrophysics Data System (ADS)

Bradley, Paul; Hall, Mike; McKenty, Patrick; Collins, Tim; Keller, David

2014-10-01

A laser-ray absorption package was recently installed in the RAGE code by the Laboratory for Laser Energetics (LLE). In this presentation, we describe our use of this package to implode Omega 60 beam symmetric direct drive capsules. The capsules have outer diameters of about 860 microns, CH plastic shell thicknesses between 8 and 32 microns, DD or DT gas fills between 5 and 20 atmospheres, and a 1 ns square pulse of 23 to 27 kJ. These capsule implosions were previously modeled with a calibrated energy source in the outer layer of the capsule, where we matched bang time and burn ion temperature well, but the simulated yields were two to three times higher than the data. We will run simulations with laser ray energy deposition to the experiments and the results to the yield and spectroscopic data. Work performed by Los Alamos National Laboratory under Contract DE-AC52-06NA25396 for the National Nuclear Security Administration of the U.S. Department of Energy.

Modeling laser-driven electron acceleration using WARP with Fourier decomposition

DOE PAGES

Lee, P.; Audet, T. L.; Lehe, R.; ...

2015-12-31

WARP is used with the recent implementation of the Fourier decomposition algorithm to model laser-driven electron acceleration in plasmas. Simulations were carried out to analyze the experimental results obtained on ionization-induced injection in a gas cell. The simulated results are in good agreement with the experimental ones, confirming the ability of the code to take into account the physics of electron injection and reduce calculation time. We present a detailed analysis of the laser propagation, the plasma wave generation and the electron beam dynamics.

Modeling laser-driven electron acceleration using WARP with Fourier decomposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, P.; Audet, T. L.; Lehe, R.

WARP is used with the recent implementation of the Fourier decomposition algorithm to model laser-driven electron acceleration in plasmas. Simulations were carried out to analyze the experimental results obtained on ionization-induced injection in a gas cell. The simulated results are in good agreement with the experimental ones, confirming the ability of the code to take into account the physics of electron injection and reduce calculation time. We present a detailed analysis of the laser propagation, the plasma wave generation and the electron beam dynamics.

Simulation of the hohlraum for a laser facility of Megajoule scale

NASA Astrophysics Data System (ADS)

Chizhkov, M. N.; Kozmanov, M. Y. U.; Lebedev, S. N.; Lykov, V. A.; Rykovanova, V. V.; Seleznev, V. N.; Selezneva, K. I.; Stryakhnina, O. V.; Shestakov, A. A.; Vronskiy, A. V.

2010-08-01

2D calculations of the promising laser hohlraums were performed with using of the Sinara computer code. These hohlraums are intended for achievement of indirectly-driven thermonuclear ignition at laser energy above 1 MJ. Two calculation variants of the laser assembly with the form close to a rugby ball were carried out: with laser entrance hole shields and without shields. Time dependent hohlraum radiation temperature and x-ray flux asymmetry on a target were obtained.

3D MHD Simulations of Laser Plasma Guiding in Curved Magnetic Field

NASA Astrophysics Data System (ADS)

Roupassov, S.; Rankin, R.; Tsui, Y.; Capjack, C.; Fedosejevs, R.

1999-11-01

The guiding and confinement of laser produced plasma in a curved magnetic field has been investigated numerically. These studies were motivated by experiments on pulsed laser deposition of diamond-like films [1] in which a 1kG magnetic field in a curved solenoid geometry was utilized to steer a carbon plasma around a curved trajectory and thus to separate it from unwanted macroparticles produced by the laser ablation. The purpose of the modeling was to characterize the plasma dynamics during the propagation through the magnetic guide field and to investigate the effect of different magnetic field configurations. A 3D curvilinear ADI code developed on the basis of an existing Cartesian code [2] was employed to simulate the underlying resistive one-fluid MHD model. Issues such as large regions of low background density and nonreflective boundary conditions were addressed. Results of the simulations in a curved guide field will be presented and compared to experimental results. [1] Y.Y. Tsui, D. Vick and R. Fedosejevs, Appl. Phys. Lett. 70 (15), pp. 1953-57, 1997. [2] R. Rankin, and I. Voronkov, in "High Performance Computing Systems and Applications", pp. 59-69, Kluwer AP, 1998.

Controlling Laser Plasma Instabilities Using Temporal Bandwidth

NASA Astrophysics Data System (ADS)

Tsung, Frank; Weaver, J.; Lehmberg, R.

2016-10-01

We are performing particle-in-cell simulations using the code OSIRIS to study the effects of laser plasma interactions in the presence of temporal bandwidth under conditions relevant to current and future experiments on the NIKE laser. Our simulations show that, for sufficiently large bandwidth (where the inverse bandwidth is comparable with the linear growth time), the saturation level, and the distribution of hot electrons, can be effected by the addition of temporal bandwidths (which can be accomplished in experiments using beam smoothing techniques such as ISI). We will quantify these effects and investigate higher dimensional effects such as laser speckles. This work is supported by DOE and NRL.

Terahertz Free Electron Laser: Design, Simulation and Analysis

DTIC Science & Technology

2014-12-01

34 1. GINGER ...and Combination Magnets .........................................72 a. GINGER Results...wavelength using GINGER FEL code for the Niowave FEL parameters. ...............................................................................40

Design of welding parameters for laser welding of thin-walled stainless steel tubes using numerical simulation

NASA Astrophysics Data System (ADS)

Nagy, M.; Behúlová, M.

2017-11-01

Nowadays, the laser technology is used in a wide spectrum of applications, especially in engineering, electronics, medicine, automotive, aeronautic or military industries. In the field of mechanical engineering, the laser technology reaches the biggest increase in the automotive industry, mainly due to the introduction of automation utilizing 5-axial movements. Modelling and numerical simulation of laser welding processes has been exploited with many advantages for the investigation of physical principles and complex phenomena connected with this joining technology. The paper is focused on the application of numerical simulation to the design of welding parameters for the circumferential laser welding of thin-walled exhaust pipes from theAISI 304 steel for automotive industry. Using the developed and experimentally verified simulation model for laser welding of tubes, the influence of welding parameters including the laser velocity from 30 mm.s-1 to 60 mm.s-1 and the laser power from 500 W to 1200 W on the temperature fields and dimensions of fusion zone was investigated using the program code ANSYS. Based on obtained results, the welding schedule for the laser beam welding of thin-walled tubes from the AISI 304 steel was suggested.

Modeling of bubble dynamics in relation to medical applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amendt, P.A.; London, R.A.; Strauss, M.

1997-03-12

In various pulsed-laser medical applications, strong stress transients can be generated in advance of vapor bubble formation. To better understand the evolution of stress transients and subsequent formation of vapor bubbles, two-dimensional simulations are presented in channel or cylindrical geometry with the LATIS (LAser TISsue) computer code. Differences with one-dimensional modeling are explored, and simulated experimental conditions for vapor bubble generation are presented and compared with data. 22 refs., 8 figs.

Research on laser marking speed optimization by using genetic algorithm.

PubMed

Wang, Dongyun; Yu, Qiwei; Zhang, Yu

2015-01-01

Laser Marking Machine is the most common coding equipment on product packaging lines. However, the speed of laser marking has become a bottleneck of production. In order to remove this bottleneck, a new method based on a genetic algorithm is designed. On the basis of this algorithm, a controller was designed and simulations and experiments were performed. The results show that using this algorithm could effectively improve laser marking efficiency by 25%.

Interaction of laser beams with magnetized substance in a strong magnetic field

NASA Astrophysics Data System (ADS)

Kuzenov, V. V.

2018-03-01

Laser-driven magneto-inertial fusion assumed plasma and magnetic flux compression by quasisymmetric laser-driven implosion of magnetized target. We develop a 2D radiation magnetohydrodynamic code and a formulation for the one-fluid two-temperature equations for simulating compressible non-equilibrium magnetized target plasma. Laser system with pulse radiation with 10 ns duration is considered for numerical experiments. A numerical study of a scheme of magnetized laser-driven implosion in the external magnetic field is carried out.

HASEonGPU-An adaptive, load-balanced MPI/GPU-code for calculating the amplified spontaneous emission in high power laser media

NASA Astrophysics Data System (ADS)

Eckert, C. H. J.; Zenker, E.; Bussmann, M.; Albach, D.

2016-10-01

We present an adaptive Monte Carlo algorithm for computing the amplified spontaneous emission (ASE) flux in laser gain media pumped by pulsed lasers. With the design of high power lasers in mind, which require large size gain media, we have developed the open source code HASEonGPU that is capable of utilizing multiple graphic processing units (GPUs). With HASEonGPU, time to solution is reduced to minutes on a medium size GPU cluster of 64 NVIDIA Tesla K20m GPUs and excellent speedup is achieved when scaling to multiple GPUs. Comparison of simulation results to measurements of ASE in Y b 3 + : Y AG ceramics show perfect agreement.

Modeling Laboratory Astrophysics Experiments in the High-Energy-Density Regime Using the CRASH Radiation-Hydrodynamics Model

NASA Astrophysics Data System (ADS)

Grosskopf, M. J.; Drake, R. P.; Trantham, M. R.; Kuranz, C. C.; Keiter, P. A.; Rutter, E. M.; Sweeney, R. M.; Malamud, G.

2012-10-01

The radiation hydrodynamics code developed by the Center for Radiative Shock Hydrodynamics (CRASH) at the University of Michigan has been used to model experimental designs for high-energy-density physics campaigns on OMEGA and other high-energy laser facilities. This code is an Eulerian, block-adaptive AMR hydrodynamics code with implicit multigroup radiation transport and electron heat conduction. CRASH model results have shown good agreement with a experimental results from a variety of applications, including: radiative shock, Kelvin-Helmholtz and Rayleigh-Taylor experiments on the OMEGA laser; as well as laser-driven ablative plumes in experiments by the Astrophysical Collisionless Shocks Experiments with Lasers (ACSEL), collaboration. We report a series of results with the CRASH code in support of design work for upcoming high-energy-density physics experiments, as well as comparison between existing experimental data and simulation results. This work is funded by the Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616, by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-FG52-09NA29548, and by the National Laser User Facility Program, grant number DE-NA0000850.

Assessing the Effects of Data Compression in Simulations Using Physically Motivated Metrics

DOE PAGES

Laney, Daniel; Langer, Steven; Weber, Christopher; ...

2014-01-01

This paper examines whether lossy compression can be used effectively in physics simulations as a possible strategy to combat the expected data-movement bottleneck in future high performance computing architectures. We show that, for the codes and simulations we tested, compression levels of 3–5X can be applied without causing significant changes to important physical quantities. Rather than applying signal processing error metrics, we utilize physics-based metrics appropriate for each code to assess the impact of compression. We evaluate three different simulation codes: a Lagrangian shock-hydrodynamics code, an Eulerian higher-order hydrodynamics turbulence modeling code, and an Eulerian coupled laser-plasma interaction code. Wemore » compress relevant quantities after each time-step to approximate the effects of tightly coupled compression and study the compression rates to estimate memory and disk-bandwidth reduction. We find that the error characteristics of compression algorithms must be carefully considered in the context of the underlying physics being modeled.« less

Relativistic Eulerian Vlasov simulations of the amplification of seed pulses by Brillouin backscattering in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shoucri, M., E-mail: Shoucri.Magdi@ireq.ca; Matte, J.-P.; Vidal, F.

We apply an Eulerian Vlasov code to study the amplification by Brillouin scattering of a short seed laser pulse by a long pump laser pulse in an underdense plasma. The stimulated Brillouin backscattering interaction is the coupling of the pump and seed electromagnetic waves propagating in opposite directions, and the ion plasma wave. The code solves the one-dimensional relativistic Vlasov-Maxwell set of equations. Large amplitude ion waves are generated. In the simulations we present, the density plateau of the plasma is n{sub e}=0.3 n{sub c} (n{sub c} is the critical density), which excludes spurious stimulated Raman scattering amplification (which can occurmore » only if n{sub e}« less

Three dimensional particle-in-cell simulations of electron beams created via reflection of intense laser light from a water target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ngirmang, Gregory K., E-mail: ngirmang.1@osu.edu; Orban, Chris; Feister, Scott

We present 3D Particle-in-Cell (PIC) modeling of an ultra-intense laser experiment by the Extreme Light group at the Air Force Research Laboratory using the Large Scale Plasma (LSP) PIC code. This is the first time PIC simulations have been performed in 3D for this experiment which involves an ultra-intense, short-pulse (30 fs) laser interacting with a water jet target at normal incidence. The laser-energy-to-ejected-electron-energy conversion efficiency observed in 2D(3v) simulations were comparable to the conversion efficiencies seen in the 3D simulations, but the angular distribution of ejected electrons in the 2D(3v) simulations displayed interesting differences with the 3D simulations' angular distribution;more » the observed differences between the 2D(3v) and 3D simulations were more noticeable for the simulations with higher intensity laser pulses. An analytic plane-wave model is discussed which provides some explanation for the angular distribution and energies of ejected electrons in the 2D(3v) simulations. We also performed a 3D simulation with circularly polarized light and found a significantly higher conversion efficiency and peak electron energy, which is promising for future experiments.« less

Summary Report of Working Group 2: Computation

NASA Astrophysics Data System (ADS)

Stoltz, P. H.; Tsung, R. S.

2009-01-01

The working group on computation addressed three physics areas: (i) plasma-based accelerators (laser-driven and beam-driven), (ii) high gradient structure-based accelerators, and (iii) electron beam sources and transport [1]. Highlights of the talks in these areas included new models of breakdown on the microscopic scale, new three-dimensional multipacting calculations with both finite difference and finite element codes, and detailed comparisons of new electron gun models with standard models such as PARMELA. The group also addressed two areas of advances in computation: (i) new algorithms, including simulation in a Lorentz-boosted frame that can reduce computation time orders of magnitude, and (ii) new hardware architectures, like graphics processing units and Cell processors that promise dramatic increases in computing power. Highlights of the talks in these areas included results from the first large-scale parallel finite element particle-in-cell code (PIC), many order-of-magnitude speedup of, and details of porting the VPIC code to the Roadrunner supercomputer. The working group featured two plenary talks, one by Brian Albright of Los Alamos National Laboratory on the performance of the VPIC code on the Roadrunner supercomputer, and one by David Bruhwiler of Tech-X Corporation on recent advances in computation for advanced accelerators. Highlights of the talk by Albright included the first one trillion particle simulations, a sustained performance of 0.3 petaflops, and an eight times speedup of science calculations, including back-scatter in laser-plasma interaction. Highlights of the talk by Bruhwiler included simulations of 10 GeV accelerator laser wakefield stages including external injection, new developments in electromagnetic simulations of electron guns using finite difference and finite element approaches.

Summary Report of Working Group 2: Computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stoltz, P. H.; Tsung, R. S.

2009-01-22

The working group on computation addressed three physics areas: (i) plasma-based accelerators (laser-driven and beam-driven), (ii) high gradient structure-based accelerators, and (iii) electron beam sources and transport [1]. Highlights of the talks in these areas included new models of breakdown on the microscopic scale, new three-dimensional multipacting calculations with both finite difference and finite element codes, and detailed comparisons of new electron gun models with standard models such as PARMELA. The group also addressed two areas of advances in computation: (i) new algorithms, including simulation in a Lorentz-boosted frame that can reduce computation time orders of magnitude, and (ii) newmore » hardware architectures, like graphics processing units and Cell processors that promise dramatic increases in computing power. Highlights of the talks in these areas included results from the first large-scale parallel finite element particle-in-cell code (PIC), many order-of-magnitude speedup of, and details of porting the VPIC code to the Roadrunner supercomputer. The working group featured two plenary talks, one by Brian Albright of Los Alamos National Laboratory on the performance of the VPIC code on the Roadrunner supercomputer, and one by David Bruhwiler of Tech-X Corporation on recent advances in computation for advanced accelerators. Highlights of the talk by Albright included the first one trillion particle simulations, a sustained performance of 0.3 petaflops, and an eight times speedup of science calculations, including back-scatter in laser-plasma interaction. Highlights of the talk by Bruhwiler included simulations of 10 GeV accelerator laser wakefield stages including external injection, new developments in electromagnetic simulations of electron guns using finite difference and finite element approaches.« less

On FAST3D simulations of directly-driven inertial-fusion targets with high-Z layers for reducing laser imprint and surface non-uniformity growth

NASA Astrophysics Data System (ADS)

Bates, Jason; Schmitt, Andrew; Klapisch, Marcel; Karasik, Max; Obenschain, Steve

2013-10-01

Modifications to the FAST3D code have been made to enhance its ability to simulate the dynamics of plastic ICF targets with high-Z overcoats. This class of problems is challenging computationally due in part to plasma conditions that are not in a state of local thermodynamic equilibrium and to the presence of mixed computational cells containing more than one material. Recently, new opacity tables for gold, palladium and plastic have been generated with an improved version of the STA code. These improved tables provide smoother, higher-fidelity opacity data over a wider range of temperature and density states than before, and contribute to a more accurate treatment of radiative transfer processes in FAST3D simulations. Furthermore, a new, more efficient subroutine known as ``MMEOS'' has been installed in the FAST3D code for determining pressure and temperature equilibrium conditions within cells containing multiple materials. We will discuss these topics, and present new simulation results for high-Z planar-target experiments performed recently on the NIKE Laser Facility. Work supported by DOE/NNSA.

Research on Laser Marking Speed Optimization by Using Genetic Algorithm

PubMed Central

Wang, Dongyun; Yu, Qiwei; Zhang, Yu

2015-01-01

Laser Marking Machine is the most common coding equipment on product packaging lines. However, the speed of laser marking has become a bottleneck of production. In order to remove this bottleneck, a new method based on a genetic algorithm is designed. On the basis of this algorithm, a controller was designed and simulations and experiments were performed. The results show that using this algorithm could effectively improve laser marking efficiency by 25%. PMID:25955831

Convergence of the Ponderomotive Guiding Center approximation in the LWFA

NASA Astrophysics Data System (ADS)

Silva, Thales; Vieira, Jorge; Helm, Anton; Fonseca, Ricardo; Silva, Luis

2017-10-01

Plasma accelerators arose as potential candidates for future accelerator technology in the last few decades because of its predicted compactness and low cost. One of the proposed designs for plasma accelerators is based on Laser Wakefield Acceleration (LWFA). However, simulations performed for such systems have to solve the laser wavelength which is orders of magnitude lower than the plasma wavelength. In this context, the Ponderomotive Guiding Center (PGC) algorithm for particle-in-cell (PIC) simulations is a potent tool. The laser is approximated by its envelope which leads to a speed-up of around 100 times because the laser wavelength is not solved. The plasma response is well understood, and comparison with the full PIC code show an excellent agreement. However, for LWFA, the convergence of the self-injected beam parameters, such as energy and charge, was not studied before and has vital importance for the use of the algorithm in predicting the beam parameters. Our goal is to do a thorough investigation of the stability and convergence of the algorithm in situations of experimental relevance for LWFA. To this end, we perform simulations using the PGC algorithm implemented in the PIC code OSIRIS. To verify the PGC predictions, we compare the results with full PIC simulations. This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant agreement No 653782.

Higher-order harmonics coupling in different free-electron laser codes

NASA Astrophysics Data System (ADS)

Giannessi, L.; Freund, H. P.; Musumeci, P.; Reiche, S.

2008-08-01

The capability for simulation of the dynamics of a free-electron laser including the higher-order harmonics in linear undulators exists in several existing codes as MEDUSA [H.P. Freund, S.G. Biedron, and S.V. Milton, IEEE J. Quantum Electron. 27 (2000) 243; H.P. Freund, Phys. Rev. ST-AB 8 (2005) 110701] and PERSEO [L. Giannessi, Overview of Perseo, a system for simulating FEL dynamics in Mathcad, < http://www.jacow.org>, in: Proceedings of FEL 2006 Conference, BESSY, Berlin, Germany, 2006, p. 91], and has been recently implemented in GENESIS 1.3 [See < http://www.perseo.enea.it>]. MEDUSA and GENESIS also include the dynamics of even harmonics induced by the coupling through the betatron motion. In addition MEDUSA, which is based on a non-wiggler averaged model, is capable of simulating the generation of even harmonics in the transversally cold beam regime, i.e. when the even harmonic coupling arises from non-linear effects associated with longitudinal particle dynamics and not to a finite beam emittance. In this paper a comparison between the predictions of the codes in different conditions is given.

Reduced 3d modeling on injection schemes for laser wakefield acceleration at plasma scale lengths

NASA Astrophysics Data System (ADS)

Helm, Anton; Vieira, Jorge; Silva, Luis; Fonseca, Ricardo

2017-10-01

Current modelling techniques for laser wakefield acceleration (LWFA) are based on particle-in-cell (PIC) codes which are computationally demanding. In PIC simulations the laser wavelength λ0, in μm-range, has to be resolved over the acceleration lengths in meter-range. A promising approach is the ponderomotive guiding center solver (PGC) by only considering the laser envelope for laser pulse propagation. Therefore only the plasma skin depth λp has to be resolved, leading to speedups of (λp /λ0) 2. This allows to perform a wide-range of parameter studies and use it for λ0 <<λp studies. We present the 3d version of a PGC solver in the massively parallel, fully relativistic PIC code OSIRIS. Further, a discussion and characterization of the validity of the PGC solver for injection schemes on the plasma scale lengths, such as down-ramp injection, magnetic injection and ionization injection, through parametric studies, full PIC simulations and theoretical scaling, is presented. This work was partially supported by Fundacao para a Ciencia e Tecnologia (FCT), Portugal, through Grant No. PTDC/FIS-PLA/2940/2014 and PD/BD/105882/2014.

Kinetic Modeling of Ultraintense X-ray Laser-Matter Interactions

NASA Astrophysics Data System (ADS)

Royle, Ryan; Sentoku, Yasuhiko; Mancini, Roberto

2016-10-01

Hard x-ray free-electron lasers (XFELs) have had a profound impact on the physical, chemical, and biological sciences. They can produce millijoule x-ray laser pulses just tens of femtoseconds in duration with more than 1012 photons each, making them the brightest laboratory x-ray sources ever produced by several orders of magnitude. An XFEL pulse can be intensified to 1020 W/cm2 when focused to submicron spot sizes, making it possible to isochorically heat solid matter well beyond 100 eV. These characteristics enable XFELs to create and probe well-characterized warm and hot dense plasmas of relevance to HED science, planetary science, laboratory astrophysics, relativistic laser plasmas, and fusion research. Several newly developed atomic physics models including photoionization, Auger ionization, and continuum-lowering have been implemented in a particle-in-cell code, PICLS, which self-consistently solves the x-ray transport, to enable the simulation of the non-LTE plasmas created by ultraintense x-ray laser interactions with solid density matter. The code is validated against the results of several recent experiments and is used to simulate the maximum-intensity x-ray heating of solid iron targets. This work was supported by DOE/OFES under Contract No. DE-SC0008827.

Implementation of a 3D version of ponderomotive guiding center solver in particle-in-cell code OSIRIS

NASA Astrophysics Data System (ADS)

Helm, Anton; Vieira, Jorge; Silva, Luis; Fonseca, Ricardo

2016-10-01

Laser-driven accelerators gained an increased attention over the past decades. Typical modeling techniques for laser wakefield acceleration (LWFA) are based on particle-in-cell (PIC) simulations. PIC simulations, however, are very computationally expensive due to the disparity of the relevant scales ranging from the laser wavelength, in the micrometer range, to the acceleration length, currently beyond the ten centimeter range. To minimize the gap between these despair scales the ponderomotive guiding center (PGC) algorithm is a promising approach. By describing the evolution of the laser pulse envelope separately, only the scales larger than the plasma wavelength are required to be resolved in the PGC algorithm, leading to speedups in several orders of magnitude. Previous work was limited to two dimensions. Here we present the implementation of the 3D version of a PGC solver into the massively parallel, fully relativistic PIC code OSIRIS. We extended the solver to include periodic boundary conditions and parallelization in all spatial dimensions. We present benchmarks for distributed and shared memory parallelization. We also discuss the stability of the PGC solver.

Power-law scaling of plasma pressure on laser-ablated tin microdroplets

NASA Astrophysics Data System (ADS)

Kurilovich, Dmitry; Basko, Mikhail M.; Kim, Dmitrii A.; Torretti, Francesco; Schupp, Ruben; Visschers, Jim C.; Scheers, Joris; Hoekstra, Ronnie; Ubachs, Wim; Versolato, Oscar O.

2018-01-01

The measurement of the propulsion of metallic microdroplets exposed to nanosecond laser pulses provides an elegant method for probing the ablation pressure in a dense laser-produced plasma. We present the measurements of the propulsion velocity over three decades in the driving Nd:YAG laser pulse energy and observe a near-perfect power law dependence. Simulations performed with the RALEF-2D radiation-hydrodynamic code are shown to be in good agreement with the power law above a specific threshold energy. The simulations highlight the importance of radiative losses which significantly modify the power of the pressure scaling. Having found a good agreement between the experiment and the simulations, we investigate the analytic origins of the obtained power law and conclude that none of the available analytic theories is directly applicable for explaining our power exponent.

Experimental and computational laser tissue welding using a protein patch.

PubMed

Small, W; Heredia, N J; Maitland, D J; Eder, D C; Celliers, P M; Da Silva, L B; London, R A; Matthews, D L

1998-01-01

An in vitro study of laser tissue welding mediated with a dye-enhanced protein patch was conducted. Fresh sections of porcine aorta were used for the experiments. Arteriotomies were treated using an indocyanine green dye-enhanced collagen patch activated by an 805-nm continuous-wave fiber-delivered diode laser. Temperature histories of the surface of the weld site were obtained using a hollow glass optical fiber-based two-color infrared thermometer. The experimental effort was complemented by simulations with the LATIS (LAser-TISsue) computer code, which uses coupled Monte Carlo, thermal transport, and mass transport models. Comparison of simulated and experimental thermal data indicated that evaporative cooling clamped the surface temperature of the weld site below 100 °C. For fluences of approximately 200 J/cm2, peak surface temperatures averaged 74°C and acute burst strengths consistently exceeded 0.14×106 dyn/cm (hoop tension). The combination of experimental and simulation results showed that the inclusion of water transport and evaporative losses in the computer code has a significant impact on the thermal distributions and hydration levels throughout the tissue volume. The solid-matrix protein patch provided a means of controllable energy delivery and yielded consistently strong welds. © 1998 Society of Photo-Optical Instrumentation Engineers.

The effect of dopants on laser imprint mitigation

NASA Astrophysics Data System (ADS)

Phillips, Lee; Gardner, John H.; Bodner, Stephen E.; Colombant, Denis; Dahlburg, Jill

1999-11-01

An intact implosion of a pellet for direct-drive ICF requires that the perturbations imprinted by the laser be kept below some threshold. We report on simulations of targets that incorporate very small concentrations of a high-Z dopant in the ablator, to increase the electron density in the ablating plasma, causing the laser to be absorbed far enough from the solid ablator to achieve a substantial degree of thermal smoothing. These calculations were performed using NRL's FAST radiation hydrodynamics code(J.H. Gardner, A.J. Schmitt, et al., Phys. Plasmas) 5, 1935 (1998), incorporating the flux-corrected transport algorithm and opacities generated by an STA code, with non-LTE radiation transport based on the Busquet method.

Simulation of the main physical processes in remote laser penetration with large laser spot size

DOE PAGES

Khairallah, S. A.; Anderson, A.; Rubenchik, A. M.; ...

2015-04-10

A 3D model is developed to simulate remote laser penetration of a 1mm Aluminum metal sheet with large laser spot size (~3x3cm²), using the ALE3D multi-physics code. The model deals with the laser-induced melting of the plate and the mechanical interaction between the solid and the melted part through plate elastic-plastic response. The effect of plate oscillations and other forces on plate rupture, the droplet formation mechanism and the influence of gravity and high laser power in further breaking the single melt droplet into many more fragments are analyzed. In the limit of low laser power, the numerical results matchmore » the available experiments. The numerical approach couples mechanical and thermal diffusion to hydrodynamics melt flow and accounts for temperature dependent material properties, surface tension, gravity and vapor recoil pressure.« less

Three-Dimensional Hydrodynamic Simulations of OMEGA Implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.

2016-10-01

The effects of large-scale (with Legendre modes less than 30) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming) and target offset, mount, and layers nonuniformities were investigated using three-dimensional (3-D) hydrodynamic simulations. Simulations indicate that the performance degradation in cryogenic implosions is caused mainly by the target offsets ( 10 to 20 μm), beampower imbalance (σrms 10 %), and initial target asymmetry ( 5% ρRvariation), which distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of the stagnated target. The ion temperature inferred from the width of simulated neutron spectra are influenced by bulk fuel motion in the distorted hot spot and can result in up to 2-keV apparent temperature increase. Similar temperature variations along different lines of sight are observed. Simulated x-ray images of implosion cores in the 4- to 8-keV energy range show good agreement with experiments. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires reducing large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing high-efficient mid-adiabat (α = 4) implosion designs that mitigate cross-beam energy transfer (CBET) and suppress short-wavelength Rayleigh-Taylor growth. These simulations use a new low-noise 3-D Eulerian hydrodynamic code ASTER. Existing 3-D hydrodynamic codes for direct-drive implosions currently miss CBET and noise-free ray-trace laser deposition algorithms. ASTER overcomes these limitations using a simplified 3-D laser-deposition model, which includes CBET and is capable of simulating the effects of beam-power imbalance, beam mispointing, mistiming, and target offset. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

OSCAR a Matlab based optical FFT code

NASA Astrophysics Data System (ADS)

Degallaix, Jérôme

2010-05-01

Optical simulation softwares are essential tools for designing and commissioning laser interferometers. This article aims to introduce OSCAR, a Matlab based FFT code, to the experimentalist community. OSCAR (Optical Simulation Containing Ansys Results) is used to simulate the steady state electric fields in optical cavities with realistic mirrors. The main advantage of OSCAR over other similar packages is the simplicity of its code requiring only a short time to master. As a result, even for a beginner, it is relatively easy to modify OSCAR to suit other specific purposes. OSCAR includes an extensive manual and numerous detailed examples such as simulating thermal aberration, calculating cavity eigen modes and diffraction loss, simulating flat beam cavities and three mirror ring cavities. An example is also provided about how to run OSCAR on the GPU of modern graphic cards instead of the CPU, making the simulation up to 20 times faster.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lanier, Nicholas Edward

We have completed implementation of a laser package in LANL's principal AGEX design code, Cassio. Although we have greatly improved our target characterization and uncertainty quantification, we remain unable to satisfactorily simulate the NIF Pleiades data.

Exploring Ultrahigh-Intensity Laser-Plasma Interaction Physics with QED Particle-in-Cell Simulations

NASA Astrophysics Data System (ADS)

Luedtke, S. V.; Yin, L.; Labun, L. A.; Albright, B. J.; Stark, D. J.; Bird, R. F.; Nystrom, W. D.; Hegelich, B. M.

2017-10-01

Next generation high-intensity lasers are reaching intensity regimes where new physics-quantum electrodynamics (QED) corrections to otherwise classical plasma dynamics-becomes important. Modeling laser-plasma interactions in these extreme settings presents a challenge to traditional particle-in-cell (PIC) codes, which either do not have radiation reaction or include only classical radiation reaction. We discuss a semi-classical approach to adding quantum radiation reaction and photon production to the PIC code VPIC. We explore these intensity regimes with VPIC, compare with results from the PIC code PSC, and report on ongoing work to expand the capability of VPIC in these regimes. This work was supported by the U.S. DOE, Los Alamos National Laboratory Science program, LDRD program, NNSA (DE-NA0002008), and AFOSR (FA9550-14-1-0045). HPC resources provided by TACC, XSEDE, and LANL Institutional Computing.

Laser Blow-Off Impurity Injection Experiments at the HSX Stellarator

NASA Astrophysics Data System (ADS)

Castillo, J. F.; Bader, A.; Likin, K. M.; Anderson, D. T.; Anderson, F. S. B.; Kumar, S. T. A.; Talmadge, J. N.

2017-10-01

Results from the HSX laser blow-off experiment are presented and compared to a synthetic diagnostic implemented in the STRAHL impurity transport modeling code in order to measure the impurity transport diffusivity and convective velocity. A laser blow-off impurity injection system is used to rapidly deposit a small, controlled quantity of aluminum into the confinement volume. Five AXUV photodiode arrays are used to take time-resolved measurements of the impurity radiation. The spatially one-dimensional impurity transport code STRAHL is used to calculate a time-dependent plasma emissivity profile. Modeled intensity signals calculated from a synthetic diagnostic code provide direct comparison between plasma simulation and experimental results. An optimization algorithm with impurity transport coefficients acting as free parameters is used to fit the model to experimental data. This work is supported by US DOE Grant DE-FG02-93ER54222.

Numerical simulation of a battlefield Nd:YAG laser

NASA Astrophysics Data System (ADS)

Henriksson, Markus; Sjoqvist, Lars; Uhrwing, Thomas

2005-11-01

A numeric model has been developed to identify the critical components and parameters in improving the output beam quality of a flashlamp pumped Q-switched Nd:YAG laser with a folded Porro-prism resonator and polarization output coupling. The heating of the laser material and accompanying thermo-optical effects are calculated using the finite element partial differential equations package FEMLAB allowing arbitrary geometries and time distributions. The laser gain and the cavity are modeled with the physical optics simulation code GLAD including effects such as gain profile, thermal lensing and stress-induced birefringence, the Pockels cell rise-time and component aberrations. The model is intended to optimize the pumping process of an OPO providing radiation to be used for ranging, imaging or optical countermeasures.

A nonlocal electron conduction model for multidimensional radiation hydrodynamics codes

NASA Astrophysics Data System (ADS)

Schurtz, G. P.; Nicolaï, Ph. D.; Busquet, M.

2000-10-01

Numerical simulation of laser driven Inertial Confinement Fusion (ICF) related experiments require the use of large multidimensional hydro codes. Though these codes include detailed physics for numerous phenomena, they deal poorly with electron conduction, which is the leading energy transport mechanism of these systems. Electron heat flow is known, since the work of Luciani, Mora, and Virmont (LMV) [Phys. Rev. Lett. 51, 1664 (1983)], to be a nonlocal process, which the local Spitzer-Harm theory, even flux limited, is unable to account for. The present work aims at extending the original formula of LMV to two or three dimensions of space. This multidimensional extension leads to an equivalent transport equation suitable for easy implementation in a two-dimensional radiation-hydrodynamic code. Simulations are presented and compared to Fokker-Planck simulations in one and two dimensions of space.

Simulation study of 3-5 keV x-ray conversion efficiency from Ar K-shell vs. Ag L-shell targets on the National Ignition Facility laser

NASA Astrophysics Data System (ADS)

Kemp, G. E.; Colvin, J. D.; Fournier, K. B.; May, M. J.; Barrios, M. A.; Patel, M. V.; Scott, H. A.; Marinak, M. M.

2015-05-01

Tailored, high-flux, multi-keV x-ray sources are desirable for studying x-ray interactions with matter for various civilian, space and military applications. For this study, we focus on designing an efficient laser-driven non-local thermodynamic equilibrium 3-5 keV x-ray source from photon-energy-matched Ar K-shell and Ag L-shell targets at sub-critical densities (˜nc/10) to ensure supersonic, volumetric laser heating with minimal losses to kinetic energy, thermal x rays and laser-plasma instabilities. Using Hydra, a multi-dimensional, arbitrary Lagrangian-Eulerian, radiation-hydrodynamics code, we performed a parameter study by varying initial target density and laser parameters for each material using conditions readily achievable on the National Ignition Facility (NIF) laser. We employ a model, benchmarked against Kr data collected on the NIF, that uses flux-limited Lee-More thermal conductivity and multi-group implicit Monte-Carlo photonics with non-local thermodynamic equilibrium, detailed super-configuration accounting opacities from Cretin, an atomic-kinetics code. While the highest power laser configurations produced the largest x-ray yields, we report that the peak simulated laser to 3-5 keV x-ray conversion efficiencies of 17.7% and 36.4% for Ar and Ag, respectively, occurred at lower powers between ˜100-150 TW. For identical initial target densities and laser illumination, the Ag L-shell is observed to have ≳10× higher emissivity per ion per deposited laser energy than the Ar K-shell. Although such low-density Ag targets have not yet been demonstrated, simulations of targets fabricated using atomic layer deposition of Ag on silica aerogels (˜20% by atomic fraction) suggest similar performance to atomically pure metal foams and that either fabrication technique may be worth pursuing for an efficient 3-5 keV x-ray source on NIF.

Investigation of CSRZ code in FSO communication

NASA Astrophysics Data System (ADS)

Zhang, Zhike; Chang, Mingchao; Zhu, Ninghua; Liu, Yu

2018-02-01

A cost-effective carrier-suppressed return-to-zero (CSRZ) code generation scheme is proposed by employing a directly modulated laser (DML) module operated at 1.5 μm wavelength. Furthermore, the performance of CSRZ code signal in free-space optical (FSO) link transmission is studied by simulation. It is found from the results that the atmospheric turbulence can deteriorate the transmission performance. However, due to have lower average transmit power and higher spectrum efficient, CSRZ code signal can obtain better amplitude suppression ratio compared to the Non-return-to-zero (NRZ) code.

Controlling Laser Plasma Instabilities Using Temporal Bandwidths Under Shock Ignition Relevant Conditions

NASA Astrophysics Data System (ADS)

Tsung, Frank; Weaver, J.; Lehmberg, R.

2017-10-01

We are performing particle-in-cell simulations using the code OSIRIS to study the effects of laser plasma interactions in the presence of temporal bandwidth under plasma conditions relevant to experiments on the Nike laser with induced spatial incoherence (ISI). With ISI, the instantaneous laser intensity can be 3-4 times larger than the average intensity, leading to the excitation of additional TPD modes and producing electrons with larger angular spread. In our simulations, we observe that although ISI can increase the interaction regions for short bursts of time, time-averaged (over many pico-seconds) laser plasma interactions can be reduced by a factor of 2 in systems with sufficiently large bandwidths (where the inverse bandwidth is comparable with the linear growth time). We will quantify these effects and investigate higher dimensional effects such as laser speckles and the effects of Coulomb collisions. Work supported by NRL, NNSA, and NSF.

Effects of non-local electron transport in one-dimensional and two-dimensional simulations of shock-ignited inertial confinement fusion targets

NASA Astrophysics Data System (ADS)

Marocchino, A.; Atzeni, S.; Schiavi, A.

2014-01-01

In some regions of a laser driven inertial fusion target, the electron mean-free path can become comparable to or even longer than the electron temperature gradient scale-length. This can be particularly important in shock-ignited (SI) targets, where the laser-spike heated corona reaches temperatures of several keV. In this case, thermal conduction cannot be described by a simple local conductivity model and a Fick's law. Fluid codes usually employ flux-limited conduction models, which preserve causality, but lose important features of the thermal flow. A more accurate thermal flow modeling requires convolution-like non-local operators. In order to improve the simulation of SI targets, the non-local electron transport operator proposed by Schurtz-Nicolaï-Busquet [G. P. Schurtz et al., Phys. Plasmas 7, 4238 (2000)] has been implemented in the DUED fluid code. Both one-dimensional (1D) and two-dimensional (2D) simulations of SI targets have been performed. 1D simulations of the ablation phase highlight that while the shock profile and timing might be mocked up with a flux-limiter; the electron temperature profiles exhibit a relatively different behavior with no major effects on the final gain. The spike, instead, can only roughly be reproduced with a fixed flux-limiter value. 1D target gain is however unaffected, provided some minor tuning of laser pulses. 2D simulations show that the use of a non-local thermal conduction model does not affect the robustness to mispositioning of targets driven by quasi-uniform laser irradiation. 2D simulations performed with only two final polar intense spikes yield encouraging results and support further studies.

The APS SASE FEL : modeling and code comparison.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biedron, S. G.

A self-amplified spontaneous emission (SASE) free-electron laser (FEL) is under construction at the Advanced Photon Source (APS). Five FEL simulation codes were used in the design phase: GENESIS, GINGER, MEDUSA, RON, and TDA3D. Initial comparisons between each of these independent formulations show good agreement for the parameters of the APS SASE FEL.

Two-dimensional simulation of high-power laser-surface interaction

NASA Astrophysics Data System (ADS)

Goldman, S. Robert; Wilke, Mark D.; Green, Ray E.; Busch, George E.; Johnson, Randall P.

1998-09-01

For laser intensities in the range of 108 - 109 W/cm2, and pulse lengths of order 10 microseconds or longer, we have modified the inertial confinement fusion code Lasnex to simulate gaseous and some dense material aspects of the laser-matter interaction. The unique aspect of our treatment consists of an ablation model which defines a dense material-vapor interface and then calculates the mass flow across this interface. The model treats the dense material as a rigid two-dimensional mass and heat reservoir suppressing all hydrodynamic motion in the dense material. The computer simulations and additional post-processors provide predictions for measurements including impulse given to the target, pressures at the target interface, electron temperatures and densities in the vapor-plasma plume region, and emission of radiation from the target. We will present an analysis of some relatively well diagnosed experiments which have been useful in developing our modeling. The simulations match experimentally obtained target impulses, pressures at the target surface inside the laser spot, and radiation emission from the target to within about 20%. Hence our simulational technique appears to form a useful basis for further investigation of laser-surface interaction in this intensity, pulse-width range.

Laser program annual report, 1979

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coleman, L.W.; Strack, J.R.

1980-03-01

This volume contains four sections that covers the areas of target design, target fabrication, diagnostics, and experiments. Section 3 reports on target design activities, plasma theory and simulation, code development, and atomic theory. Section 4 presents the accomplishments of the target fabrication group, and Section 5 presents results of diagnostic developments and applications for the year. The results of laser-target experiments are presented. (MOW)

Recent Developments in the VISRAD 3-D Target Design and Radiation Simulation Code

NASA Astrophysics Data System (ADS)

Macfarlane, Joseph; Golovkin, Igor; Sebald, James

2017-10-01

The 3-D view factor code VISRAD is widely used in designing HEDP experiments at major laser and pulsed-power facilities, including NIF, OMEGA, OMEGA-EP, ORION, Z, and LMJ. It simulates target designs by generating a 3-D grid of surface elements, utilizing a variety of 3-D primitives and surface removal algorithms, and can be used to compute the radiation flux throughout the surface element grid by computing element-to-element view factors and solving power balance equations. Target set-up and beam pointing are facilitated by allowing users to specify positions and angular orientations using a variety of coordinates systems (e.g., that of any laser beam, target component, or diagnostic port). Analytic modeling for laser beam spatial profiles for OMEGA DPPs and NIF CPPs is used to compute laser intensity profiles throughout the grid of surface elements. VISRAD includes a variety of user-friendly graphics for setting up targets and displaying results, can readily display views from any point in space, and can be used to generate image sequences for animations. We will discuss recent improvements to conveniently assess beam capture on target and beam clearance of diagnostic components, as well as plans for future developments.

Modeling of induction-linac based free-electron laser amplifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jong, R.A.; Fawley, W.M.; Scharlemann, E.T.

We describe the modeling of an induction-linac based free-electron laser (IFEL) amplifier for producing multimegawatt levels of microwave power. We have used the Lawrence Livermore National Laboratory (LLNL) free-electron laser simulation code, FRED, and the simulation code for sideband calculations, GINGER for this study. For IFEL amplifiers in the frequency range of interest (200 to 600 GHz), we have devised a wiggler design strategy which incorporates a tapering algorithm that is suitable for free-electron laser (FEL) systems with moderate space-charge effects and that minimizes spontaneous noise growth at frequencies below the fundamental, while enhancing the growth of the signal atmore » the fundamental. In addition, engineering design considerations of the waveguide wall loading and electron beam fill factor in the waveguide set limits on the waveguide dimensions, the wiggler magnet gap spacing, the wiggler period, and the minimum magnetic field strength in the tapered region of the wiggler. As an example, we shall describe an FEL amplifier designed to produce an average power of about 10 MW at a frequency of 280 GHz to be used for electron cyclotron resonance heating of tokamak fusion devices. 17 refs., 4 figs.« less

Properties of laser-produced GaAs plasmas measured from highly resolved X-ray line shapes and ratios

NASA Astrophysics Data System (ADS)

Seely, J. F.; Fein, J.; Manuel, M.; Keiter, P.; Drake, P.; Kuranz, C.; Belancourt, Patrick; Ralchenko, Yu.; Hudson, L.; Feldman, U.

2018-03-01

The properties of hot, dense plasmas generated by the irradiation of GaAs targets by the Titan laser at Lawrence Livermore National Laboratory were determined by the analysis of high resolution K shell spectra in the 9 keV to 11 keV range. The laser parameters, such as relatively long pulse duration and large focal spot, were chosen to produce a steady-state plasma with minimal edge gradients, and the time-integrated spectra were compared to non-LTE steady state spectrum simulations using the FLYCHK and NOMAD codes. The bulk plasma streaming velocity was measured from the energy shifts of the Ga He-like transitions and Li-like dielectronic satellites. The electron density and the electron energy distribution, both the thermal and the hot non-thermal components, were determined from the spectral line ratios. After accounting for the spectral line broadening contributions, the plasma turbulent motion was measured from the residual line widths. The ionization balance was determined from the ratios of the He-like through F-like spectral features. The detailed comparison of the experimental Ga spectrum and the spectrum simulated by the FLYCHK code indicates two significant discrepancies, the transition energy of a Li-like dielectronic satellite (designated t) and the calculated intensity of a He-like line (x), that should lead to improvements in the kinetics codes used to simulate the X-ray spectra from highly-charged ions.

Volkov basis for simulation of interaction of strong laser pulses and solids

NASA Astrophysics Data System (ADS)

Kidd, Daniel; Covington, Cody; Li, Yonghui; Varga, Kálmán

2018-01-01

An efficient and accurate basis comprised of Volkov states is implemented and tested for time-dependent simulations of interactions between strong laser pulses and crystalline solids. The Volkov states are eigenstates of the free electron Hamiltonian in an electromagnetic field and analytically represent the rapidly oscillating time-dependence of the orbitals, allowing significantly faster time propagation than conventional approaches. The Volkov approach can be readily implemented in plane-wave codes by multiplying the potential energy matrix elements with a simple time-dependent phase factor.

Simulated Performance of the Wisconsin Superconducting Electron Gun

DOE Office of Scientific and Technical Information (OSTI.GOV)

R.A. Bosch, K.J. Kleman, R.A. Legg

2012-07-01

The Wisconsin superconducting electron gun is modeled with multiparticle tracking simulations using the ASTRA and GPT codes. To specify the construction of the emittance-compensation solenoid, we studied the dependence of the output bunch's emittance upon the solenoid's strength and field errors. We also evaluated the dependence of the output bunch's emittance upon the bunch's initial emittance and the size of the laser spot on the photocathode. The results suggest that a 200-pC bunch with an emittance of about one mm-mrad can be produced for a free-electron laser.

Flyer Target Acceleration and Energy Transfer at its Collision with Massive Targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borodziuk, S.; Kasperczuk, A.; Pisarczyk, T.

2006-01-15

Numerical modelling was aimed at simulation of successive events resulting from interaction of laser beam-single and double targets. It was performed by means of the 2D Lagrangian hydrodynamics code ATLANT-HE. This code is based on one-fluid and two-temperature model of plasma with electron and ion heat conductivity considerations. The code has an advanced treatment of laser light propagation and absorption. This numerical modelling corresponds to the experiment, which was carried out with the use of the PALS facility. Two types of planar solid targets, i.e. single massive Al slabs and double targets consisting of 6 {mu}m thick Al foil andmore » Al slab were applied. The targets were irradiated by the iodine laser pulses of two wavelengths: 1.315 and 0.438 {mu}m. A pulse duration of 0.4 ns and a focal spot diameter of 250 {mu}m at a laser energy of 130 J were used. The numerical modelling allowed us to obtain a more detailed description of shock wave propagation and crater formation.« less

Introduction to the Laser-HANE Experiment and Summary of Low-Pressure Interaction Results.

DTIC Science & Technology

1984-02-22

NUMBER ORGANIZATION Efi .FFUcablej Defense Nuclear Agency r____________________ S. ADDRESS IC0lY.7f ande~ ZIP Code# 10. SOURCE O FUNDING NOS. PROGRAM...of Atmospheric Effects (RAAE), initiated a laser-target HANE-simulation experiment at the Naval Research Laboratory in early 1982. The objective of...The experiment involves focusing beams from the NRL-Pharos II Nd-laser (1.05 ljm wavelength) onto a small (< 1 rmm dia, few-microns thick foil ) solid

Laser-driven planar Rayleigh-Taylor instability experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glendinning, S.G.; Weber, S.V.; Bell, P.

1992-08-24

We have performed a series of experiments on the Nova Laser Facility to examine the hydrodynamic behavior of directly driven planar foils with initial perturbations of varying wavelength. The foils were accelerated with a single, frequency doubled, smoothed and temporally shaped laser beam at 0.8{times}10{sup 14} W/cm{sup 2}. The experiments are in good agreement with numerical simulations using the computer codes LASNEX and ORCHID which show growth rates reduced to about 70% of classical for this nonlinear regime.

Simulate what is measured: next steps towards predictive simulations (Conference Presentation)

NASA Astrophysics Data System (ADS)

Bussmann, Michael; Kluge, Thomas; Debus, Alexander; Hübl, Axel; Garten, Marco; Zacharias, Malte; Vorberger, Jan; Pausch, Richard; Widera, René; Schramm, Ulrich; Cowan, Thomas E.; Irman, Arie; Zeil, Karl; Kraus, Dominik

2017-05-01

Simulations of laser matter interaction at extreme intensities that have predictive power are nowadays in reach when considering codes that make optimum use of high performance compute architectures. Nevertheless, this is mostly true for very specific settings where model parameters are very well known from experiment and the underlying plasma dynamics is governed by Maxwell's equations solely. When including atomic effects, prepulse influences, radiation reaction and other physical phenomena things look different. Not only is it harder to evaluate the sensitivity of the simulation result on the variation of the various model parameters but numerical models are less well tested and their combination can lead to subtle side effects that influence the simulation outcome. We propose to make optimum use of future compute hardware to compute statistical and systematic errors rather than just find the mots optimum set of parameters fitting an experiment. This requires to include experimental uncertainties which is a challenge to current state of the art techniques. Moreover, it demands better comparison to experiments as inclusion of simulating the diagnostic's response becomes important. We strongly advocate the use of open standards for finding interoperability between codes for comparison studies, building complete tool chains for simulating laser matter experiments from start to end.

Synchrotron Radiation Workshop (SRW)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chubar, O.; Elleaume, P.

2013-03-01

"Synchrotron Radiation Workshop" (SRW) is a physical optics computer code for calculation of detailed characteristics of Synchrotron Radiation (SR) generated by relativistic electrons in magnetic fields of arbitrary configuration and for simulation of the radiation wavefront propagation through optical systems of beamlines. Frequency-domain near-field methods are used for the SR calculation, and the Fourier-optics based approach is generally used for the wavefront propagation simulation. The code enables both fully- and partially-coherent radiation propagation simulations in steady-state and in frequency-/time-dependent regimes. With these features, the code has already proven its utility for a large number of applications in infrared, UV, softmore » and hard X-ray spectral range, in such important areas as analysis of spectral performances of new synchrotron radiation sources, optimization of user beamlines, development of new optical elements, source and beamline diagnostics, and even complete simulation of SR based experiments. Besides the SR applications, the code can be efficiently used for various simulations involving conventional lasers and other sources. SRW versions interfaced to Python and to IGOR Pro (WaveMetrics), as well as cross-platform library with C API, are available.« less

Simulation of the excitation of quasi-plane wake waves in a plasma by a resonant sequence of laser pulses with a variable envelope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalinnikova, E. I.; Levchenko, V. D.

2008-04-15

Results are presented from full-scale numerical simulations of the excitation of wake waves by a sequence of weakly relativistic laser pulses in a subcritical plasma. Computations were carried out with a 2D3V version of the SUR-CA code that is based on the local-recursive nonlocal-asynchronous algorithm of the particle-in-cell method. The parameters of a train of laser pulses were chosen to correspond to the resonant excitation of the wake field. The curvature of the envelope of the pulses was chosen to depend on the number of the pulse in the train. Numerical simulations showed that there are plane waves during themore » first period of the plasma wave behind the pulse train.« less

Simulations of the interaction of intense petawatt laser pulses with dense Z-pinch plasmas : final report LDRD 39670.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welch, Dale Robert; MacFarlane, Joseph John; Mehlhorn, Thomas Alan

We have studied the feasibility of using the 3D fully electromagnetic implicit hybrid particle code LSP (Large Scale Plasma) to study laser plasma interactions with dense, compressed plasmas like those created with Z, and which might be created with the planned ZR. We have determined that with the proper additional physics and numerical algorithms developed during the LDRD period, LSP was transformed into a unique platform for studying such interactions. Its uniqueness stems from its ability to consider realistic compressed densities and low initial target temperatures (if required), an ability that conventional PIC codes do not possess. Through several testmore » cases, validations, and applications to next generation machines described in this report, we have established the suitability of the code to look at fast ignition issues for ZR, as well as other high-density laser plasma interaction problems relevant to the HEDP program at Sandia (e.g. backlighting).« less

Effects of the plasma profiles on photon and pair production in ultrahigh intensity laser solid interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Y. X.; Jin, X. L., E-mail: jinxiaolin@uestc.edu.cn; Yan, W. Z.

The model of photon and pair production in strong field quantum electrodynamics is implemented into our 1D3V particle-in-cell code with Monte Carlo algorithm. Using this code, the evolution of the particles in ultrahigh intensity laser (∼10{sup 23} W/cm{sup 2}) interaction with aluminum foil target is observed. Four different initial plasma profiles are considered in the simulations. The effects of initial plasma profiles on photon and pair production, energy spectra, and energy evolution are analyzed. The results imply that one can set an optimal initial plasma profile to obtain the desired photon distributions.

Progress on 3-D ICF simulations and Ray-Traced Power Deposition Method

NASA Astrophysics Data System (ADS)

Schmitt, Andrew J.; Fyfe, David E.

2016-10-01

We have performed 3D simulations of Omega-scale and NIF-scale spherical direct-drive targets with the massively parallel fastrad3d code. Of particular interest is the robustness of the targets to the low mode perturbations impressed on the target by the laser system and how it compares to the influence of the perturbations produced by laser imprinting. As part of this simulation capability, we have upgraded our smoothed 3D raytrace package to run in spherical geometry. This package, which connects rays to form bundles and performs power deposition calculations on the bundles, can decrease laser absorption noise while using fewer rays and less message passing. This model produces both the imprint and the low-mode asymmetry drive that we are interested in here. We show recent simulation results of directly-driven targets using conventional ignition drive, and report on the influences of the two sources - low mode asymmetry and laser imprint - as the pellet conditions (e.g. adiabat) are varied. Work supported by DoE/NNSA.

Simulation of radiation in laser produced plasmas

NASA Astrophysics Data System (ADS)

Colombant, D. G.; Klapisch, M.; Deniz, A. V.; Weaver, J.; Schmitt, A.

1999-11-01

The radiation hydrodynamics code FAST1D(J.H.Gardner,A.J.Schmitt,J.P.Dahlburg,C.J.Pawley,S.E.Bodner,S.P.Obenschain,V.Serlin and Y.Aglitskiy,Phys. Plasmas,5,1935(1998)) was used directly (i.e. without postprocessor) to simulate radiation emitted from flat targets irradiated by the Nike laser, from 10^12 W/cm^2 to 10^13W/cm^2. We use enough photon groups to resolve spectral lines. Opacities are obtained from the STA code(A.Bar-Shalom,J.Oreg,M.Klapisch and T.Lehecka,Phys.Rev.E,59,3512(1999)), and non LTE effects are described with the Busquet model(M.Busquet,Phys.Fluids B,5,4191(1993)). Results are compared to transmission grating spectra in the range 100-600eV, and to time-resolved calibrated filtered diodes (spectral windows around 100, 180, 280 and 450 eV).

Laser Ray Tracing in a Parallel Arbitrary Lagrangian-Eulerian Adaptive Mesh Refinement Hydrocode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Masters, N D; Kaiser, T B; Anderson, R W

2009-09-28

ALE-AMR is a new hydrocode that we are developing as a predictive modeling tool for debris and shrapnel formation in high-energy laser experiments. In this paper we present our approach to implementing laser ray-tracing in ALE-AMR. We present the equations of laser ray tracing, our approach to efficient traversal of the adaptive mesh hierarchy in which we propagate computational rays through a virtual composite mesh consisting of the finest resolution representation of the modeled space, and anticipate simulations that will be compared to experiments for code validation.

Computer Modeling of Direct Metal Laser Sintering

NASA Technical Reports Server (NTRS)

Cross, Matthew

2014-01-01

A computational approach to modeling direct metal laser sintering (DMLS) additive manufacturing process is presented. The primary application of the model is for determining the temperature history of parts fabricated using DMLS to evaluate residual stresses found in finished pieces and to assess manufacturing process strategies to reduce part slumping. The model utilizes MSC SINDA as a heat transfer solver with imbedded FORTRAN computer code to direct laser motion, apply laser heating as a boundary condition, and simulate the addition of metal powder layers during part fabrication. Model results are compared to available data collected during in situ DMLS part manufacture.

First PIC simulations modeling the interaction of ultra-intense lasers with sub-micron, liquid crystal targets

NASA Astrophysics Data System (ADS)

McMahon, Matthew; Poole, Patrick; Willis, Christopher; Andereck, David; Schumacher, Douglass

2014-10-01

We recently introduced liquid crystal films as on-demand, variable thickness (50-5000 nanometers), low cost targets for intense laser experiments. Here we present the first particle-in-cell (PIC) simulations of short pulse laser excitation of liquid crystal targets treating Scarlet (OSU) class lasers using the PIC code LSP. In order to accurately model the target evolution, a low starting temperature and field ionization model are employed. This is essential as large starting temperatures, often used to achieve large Debye lengths, lead to expansion of the target causing significant reduction of the target density before the laser pulse can interact. We also present an investigation of the modification of laser pulses by very thin targets. This work was supported by the DARPA PULSE program through a grant from ARMDEC, by the US Department of Energy under Contract No. DE-NA0001976, and allocations of computing time from the Ohio Supercomputing Center.

Data acquisition and path selection decision making for an autonomous roving vehicle

NASA Technical Reports Server (NTRS)

Frederick, D. K.; Shen, C. N.; Yerazunis, S. W.

1976-01-01

Problems related to the guidance of an autonomous rover for unmanned planetary exploration were investigated. Topics included in these studies were: simulation on an interactive graphics computer system of the Rapid Estimation Technique for detection of discrete obstacles; incorporation of a simultaneous Bayesian estimate of states and inputs in the Rapid Estimation Scheme; development of methods for estimating actual laser rangefinder errors and their application to date provided by Jet Propulsion Laboratory; and modification of a path selection system simulation computer code for evaluation of a hazard detection system based on laser rangefinder data.

Simulation study of 3–5 keV x-ray conversion efficiency from Ar K-shell vs. Ag L-shell targets on the National Ignition Facility laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kemp, G. E., E-mail: kemp10@llnl.gov; Colvin, J. D.; Fournier, K. B.

2015-05-15

Tailored, high-flux, multi-keV x-ray sources are desirable for studying x-ray interactions with matter for various civilian, space and military applications. For this study, we focus on designing an efficient laser-driven non-local thermodynamic equilibrium 3–5 keV x-ray source from photon-energy-matched Ar K-shell and Ag L-shell targets at sub-critical densities (∼n{sub c}/10) to ensure supersonic, volumetric laser heating with minimal losses to kinetic energy, thermal x rays and laser-plasma instabilities. Using HYDRA, a multi-dimensional, arbitrary Lagrangian-Eulerian, radiation-hydrodynamics code, we performed a parameter study by varying initial target density and laser parameters for each material using conditions readily achievable on the National Ignition Facilitymore » (NIF) laser. We employ a model, benchmarked against Kr data collected on the NIF, that uses flux-limited Lee-More thermal conductivity and multi-group implicit Monte-Carlo photonics with non-local thermodynamic equilibrium, detailed super-configuration accounting opacities from CRETIN, an atomic-kinetics code. While the highest power laser configurations produced the largest x-ray yields, we report that the peak simulated laser to 3–5 keV x-ray conversion efficiencies of 17.7% and 36.4% for Ar and Ag, respectively, occurred at lower powers between ∼100–150 TW. For identical initial target densities and laser illumination, the Ag L-shell is observed to have ≳10× higher emissivity per ion per deposited laser energy than the Ar K-shell. Although such low-density Ag targets have not yet been demonstrated, simulations of targets fabricated using atomic layer deposition of Ag on silica aerogels (∼20% by atomic fraction) suggest similar performance to atomically pure metal foams and that either fabrication technique may be worth pursuing for an efficient 3–5 keV x-ray source on NIF.« less

Effects of Radiation Damping in Extreme Ultra-intense Laser-Plasma Interaction

NASA Astrophysics Data System (ADS)

Pandit, Rishi R.

Recent advances in the development of intense short pulse lasers are significant. Now it is available to access a laser with intensity 1021W/cm2 by focusing a petawatt class laser. In a few years, the intensity will exceed 1022W/cm2 , at which intensity electrons accelerated by the laser get energy more than 100 MeV and start to emit radiation strongly. Resultingly, the damping of electron motion can become large. In order to study this problem, we developed a code to solve a set of equations describing the evolution of a strong electromagnetic wave interacting with a single electron. Usually the equation of motion of an electron including radiation damping under the influence of electromagnetic fields is derived from the Lorentz-Dirac equation treating the damping as a perturbation. So far people had used the first order damping equation. This is because the second order term seems to be small and actually it is negligible under 1022W/cm2 intensity. The derivation of 2nd order equation is also complicated and challenging. We derived the second order damping equations for the first time and implemented in the code. The code was then tested via single particle motion in the extreme intensity laser. It was found that the 1st order damping term is reasonable up to the intensity 1022W/cm2, but the 2nd oder term becomes not negligible and comparable in magnitude to the first order term beyond 1023W/cm2. The radiation damping model was introduced using a one-dimensional particle-in-cell code (PIC), and tested in the laser-plasma interaction at extreme intensity. The strong damping of hot electrons in high energy tail was demonstrated in PIC simulations.

Lidar performance analysis

NASA Technical Reports Server (NTRS)

Spiers, Gary D.

1994-01-01

Section 1 details the theory used to build the lidar model, provides results of using the model to evaluate AEOLUS design instrument designs, and provides snapshots of the visual appearance of the coded model. Appendix A contains a Fortran program to calculate various forms of the refractive index structure function. This program was used to determine the refractive index structure function used in the main lidar simulation code. Appendix B contains a memo on the optimization of the lidar telescope geometry for a line-scan geometry. Appendix C contains the code for the main lidar simulation and brief instruction on running the code. Appendix D contains a Fortran code to calculate the maximum permissible exposure for the eye from the ANSI Z136.1-1992 eye safety standards. Appendix E contains a paper on the eye safety analysis of a space-based coherent lidar presented at the 7th Coherent Laser Radar Applications and Technology Conference, Paris, France, 19-23 July 1993.

Validation of non-local electron heat conduction model for radiation MHD simulation in magnetized laser plasma

NASA Astrophysics Data System (ADS)

Nagatomo, Hideo; Matsuo, Kazuki; Nicolai, Pilippe; Asahina, Takashi; Fujioka, Shinsuke

2017-10-01

In laser plasma physics, application of an external magnetic field is an attractive method for various research of high energy density physics including fast ignition. Meanwhile, in the high intense laser plasma the behavior of hot electron cannot be ignored. In the radiation hydrodynamic simulation, a classical electron conduction model, Spitzer-Harm model has been used in general. However the model has its limit, and modification of the model is necessary if it is used beyond the application limit. Modified SNB model, which considering the influence of magnetic field is applied to 2-D radiation magnetohydrodynamic code PINOCO. Some experiments related the non-local model are carried out at GXII, Osaka University. In this presentation, these experimental results are shown briefly. And comparison between simulation results considering the non-local electron heat conduction mode are discussed. This study was supported JSPS KAKENHI Grant No. 17K05728.

2D hydrodynamic simulations of a variable length gas target for density down-ramp injection of electrons into a laser wakefield accelerator

NASA Astrophysics Data System (ADS)

Kononenko, O.; Lopes, N. C.; Cole, J. M.; Kamperidis, C.; Mangles, S. P. D.; Najmudin, Z.; Osterhoff, J.; Poder, K.; Rusby, D.; Symes, D. R.; Warwick, J.; Wood, J. C.; Palmer, C. A. J.

2016-09-01

In this work, two-dimensional (2D) hydrodynamic simulations of a variable length gas cell were performed using the open source fluid code OpenFOAM. The gas cell was designed to study controlled injection of electrons into a laser-driven wakefield at the Astra Gemini laser facility. The target consists of two compartments: an accelerator and an injector section connected via an aperture. A sharp transition between the peak and plateau density regions in the injector and accelerator compartments, respectively, was observed in simulations with various inlet pressures. The fluid simulations indicate that the length of the down-ramp connecting the sections depends on the aperture diameter, as does the density drop outside the entrance and the exit cones. Further studies showed, that increasing the inlet pressure leads to turbulence and strong fluctuations in density along the axial profile during target filling, and consequently, is expected to negatively impact the accelerator stability.

A time domain simulation of a beam control system

NASA Astrophysics Data System (ADS)

Mitchell, J. R.

1981-02-01

The Airborne Laser Laboratory (ALL) is being developed by the Air Force to investigate the integration and operation of high energy laser components in a dynamic airborne environment and to study the propagation of laser light from an airborne vehicle to an airborne target. The ALL is composed of several systems; among these are the Airborne Pointing and Tracking System (APT) and the Automatic Alignment System (AAS). This report presents the results of performing a time domain dynamic simulation for an integrated beam control system composed of the APT and AAS. The simulation is performed on a digital computer using the MIMIC language. It includes models of the dynamics of the system and of disturbances. Also presented in the report are the rationales and developments of these models. The data from the simulation code is summarized by several plots. In addition results from massaging the data with waveform analysis packages are presented. The results are discussed and conclusions are drawn.

OSA Proceedings of the Topical Meeting (5th) on Short-Wave Length Coherent Radiation: Generation and Applications Held in Monterey, California on 8-10 April 1991. Volume 11

DTIC Science & Technology

1992-05-22

PIC simulation code to study several of the constraints imposed by plasma phenomena on the propagation of ultrashort high intensity laser pulses in...and radiation spectrum of free electrons in the focus of an ultrashort high intensity laser pulse is solved. Motion and radiation of electrons in a...higher harmonics. These studies are intended as a prelude to experiments with high intensity ultrashort laser pulses . To investigate the motion of

Analysis of the X-ray emission spectra of copper, germanium and rubidium plasmas produced at the Phelix laser facility

NASA Astrophysics Data System (ADS)

Comet, M.; Pain, J.-C.; Gilleron, F.; Piron, R.; Denis-Petit, D.; Méot, V.; Gosselin, G.; Morel, P.; Hannachi, F.; Gobet, F.; Tarisien, M.; Versteegen, M.

2017-03-01

We present the analysis of X-ray emission spectra of copper, germanium and rubidium plasmas measured at the Phelix laser facility. The laser intensity was around 6×1014 W.cm-2. The analysis is based on the hypothesis of an homogeneous plasma in local thermodynamic equilibrium using an effective temperature. This temperature is deduced from hydrodynamic simulations and collisional-radiative computations. Spectra are then calculated using the LTE opacity codes OPAMCDF and SCO-RCG and compared to experimental data.

Update on 2-D OMEGA Capsule Implosions

NASA Astrophysics Data System (ADS)

Bradley, Paul

2017-10-01

We have an upgraded laser energy deposition package in our AMR-Eulerian radiation-hydrodynamic code called RAGE. As part of our validation effort, we ran 2-D simulations for a series of OMEGA direct drive implosion capsules that have shell thickness ranging from 7.2 to 29.3 μm and different gas fills. These simulations include the effect of surface roughness, laser spot non-uniformity, the mounting stalk, and the glue spot. We examined the sensitivity of our simulated results to mesh resolution and mix model. Our simulated results compare well to the experimental yield, ion temperature, burn width, and x-ray size data. Work performed by Los Alamos National Laboratory under contract DE-AC52-06NA25396 for the National Nuclear Security Administration of the U.S. Department of Energy.

Three-dimensional simulation of free-electron laser harmonics with FRED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharp, W.M.; Scharlemann, E.T.; Fawley, W.M.

1989-11-20

FRED3D, a single-mode three-dimensional version of the FEL simulation code FRED, has been modified to follow the growth of signal components at the fundamental frequency and at even and odd harmonics. The Wiggle-averaged particle and field equations for this multi-mode formulation are derived here, and their implementation in FRED3D is discussed. 12 refs.

Kinetic Monte Carlo simulation of dopant-defect systems under submicrosecond laser thermal processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fisicaro, G.; Pelaz, Lourdes; Lopez, P.

2012-11-06

An innovative Kinetic Monte Carlo (KMC) code has been developed, which rules the post-implant kinetics of the defects system in the extremely far-from-the equilibrium conditions caused by the laser irradiation close to the liquid-solid interface. It considers defect diffusion, annihilation and clustering. The code properly implements, consistently to the stochastic formalism, the fast varying local event rates related to the thermal field T(r,t) evolution. This feature of our numerical method represents an important advancement with respect to current state of the art KMC codes. The reduction of the implantation damage and its reorganization in defect aggregates are studied as amore » function of the process conditions. Phosphorus activation efficiency, experimentally determined in similar conditions, has been related to the emerging damage scenario.« less

Non-local electron transport validation using 2D DRACO simulations

NASA Astrophysics Data System (ADS)

Cao, Duc; Chenhall, Jeff; Moll, Eli; Prochaska, Alex; Moses, Gregory; Delettrez, Jacques; Collins, Tim

2012-10-01

Comparison of 2D DRACO simulations, using a modified versionfootnotetextprivate communications with M. Marinak and G. Zimmerman, LLNL. of the Schurtz, Nicolai and Busquet (SNB) algorithmfootnotetextSchurtz, Nicolai and Busquet, ``A nonlocal electron conduction model for multidimensional radiation hydrodynamics codes,'' Phys. Plasmas 7, 4238(2000). for non-local electron transport, with direct drive shock timing experimentsfootnotetextT. Boehly, et. al., ``Multiple spherically converging shock waves in liquid deuterium,'' Phys. Plasmas 18, 092706(2011). and with the Goncharov non-local modelfootnotetextV. Goncharov, et. al., ``Early stage of implosion in inertial confinement fusion: Shock timing and perturbation evolution,'' Phys. Plasmas 13, 012702(2006). in 1D LILAC will be presented. Addition of an improved SNB non-local electron transport algorithm in DRACO allows direct drive simulations with no need for an electron conduction flux limiter. Validation with shock timing experiments that mimic the laser pulse profile of direct drive ignition targets gives a higher confidence level in the predictive capability of the DRACO code. This research was supported by the University of Rochester Laboratory for Laser Energetics.

Pulse position modulation for compact all-fiber vehicle laser rangefinder development

NASA Astrophysics Data System (ADS)

Mao, Xuesong; Cheng, Yongzhi; Xiong, Ying; Inoue, Daisuke; Kagami, Manabu

2017-10-01

We propose a method for developing small all-fiber vehicle laser rangefinders that is based on pulse position modulation (PPM) and data integration and present a theoretical study on its performance. Compared with spatial coupling, which is employed by most of the current commercial vehicle laser rangefinders, fiber coupling has the advantage that it can guide laser echoes into the interior of a car, so the electronic components following the photodiode can operate in a moderate-temperature environment. However, optical fibers have numerical apertures (NAs), which means that a laser beam from a receiving lens cannot be coupled into an optical fiber if its incident angle exceeds the critical value. Therefore, the effective size of the receiving lens is typically small since it is limited by its focal length and the NA of the fiber, causing the power of the laser echoes gathered by the receiving lens to be insufficient for performing target identification. Instead of increasing the peak transmitting laser power unrestrictedly, PPM and data integration effectively compensate for the low signal-to-noise ratio that results from the effective receiving lens size reduction. We validated the proposed method by conducting numerical simulations and performance analysis. Finally, we compared the proposed method with pseudorandom noise (PN) code modulation and found that, although the two methods perform equally well in single-target measurement scenarios, PPM is more effective than PN code modulation for multitarget measurement. In addition, PPM enables the transmission of laser beams with higher peak powers and requires less computation than PN code modulation does.

Quasi-real-time end-to-end simulations of ELT-scale adaptive optics systems on GPUs

NASA Astrophysics Data System (ADS)

Gratadour, Damien

2011-09-01

Our team has started the development of a code dedicated to GPUs for the simulation of AO systems at the E-ELT scale. It uses the CUDA toolkit and an original binding to Yorick (an open source interpreted language) to provide the user with a comprehensive interface. In this paper we present the first performance analysis of our simulation code, showing its ability to provide Shack-Hartmann (SH) images and measurements at the kHz scale for VLT-sized AO system and in quasi-real-time (up to 70 Hz) for ELT-sized systems on a single top-end GPU. The simulation code includes multiple layers atmospheric turbulence generation, ray tracing through these layers, image formation at the focal plane of every sub-apertures of a SH sensor using either natural or laser guide stars and centroiding on these images using various algorithms. Turbulence is generated on-the-fly giving the ability to simulate hours of observations without the need of loading extremely large phase screens in the global memory. Because of its performance this code additionally provides the unique ability to test real-time controllers for future AO systems under nominal conditions.

Large-scale 3D simulations of ICF and HEDP targets

NASA Astrophysics Data System (ADS)

Marinak, Michael M.

2000-10-01

The radiation hydrodynamics code HYDRA continues to be developed and applied to 3D simulations of a variety of targets for both inertial confinement fusion (ICF) and high energy density physics. Several packages have been added enabling this code to perform ICF target simulations with similar accuracy as two-dimensional codes of long-time historical use. These include a laser ray trace and deposition package, a heavy ion deposition package, implicit Monte Carlo photonics, and non-LTE opacities, derived from XSN or the linearized response matrix approach.(R. More, T. Kato, Phys. Rev. Lett. 81, 814 (1998), S. Libby, F. Graziani, R. More, T. Kato, Proceedings of the 13th International Conference on Laser Interactions and Related Plasma Phenomena, (AIP, New York, 1997).) LTE opacities can also be calculated for arbitrary mixtures online by combining tabular values generated by different opacity codes. Thermonuclear burn, charged particle transport, neutron energy deposition, electron-ion coupling and conduction, and multigroup radiation diffusion packages are also installed. HYDRA can employ ALE hydrodynamics; a number of grid motion algorithms are available. Multi-material flows are resolved using material interface reconstruction. Results from large-scale simulations run on up to 1680 processors, using a combination of massively parallel processing and symmetric multiprocessing, will be described. A large solid angle simulation of Rayleigh-Taylor instability growth in a NIF ignition capsule has resolved simultaneously the full spectrum of the most dangerous modes that grow from surface roughness. Simulations of a NIF hohlraum illuminated with the initial 96 beam configuration have also been performed. The effect of the hohlraum’s 3D intrinsic drive asymmetry on the capsule implosion will be considered. We will also discuss results from a Nova experiment in which a copper sphere is crushed by a planar shock. Several interacting hydrodynamic instabilities, including the Widnall instability, cause breakup of the resulting vortex ring.

Angular radiation temperature simulation for time-dependent capsule drive prediction in inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jing, Longfei; Yang, Dong; Li, Hang

2015-02-15

The x-ray drive on a capsule in an inertial confinement fusion setup is crucial for ignition. Unfortunately, a direct measurement has not been possible so far. We propose an angular radiation temperature simulation to predict the time-dependent drive on the capsule. A simple model, based on the view-factor method for the simulation of the radiation temperature, is presented and compared with the experimental data obtained using the OMEGA laser facility and the simulation results acquired with VISRAD code. We found a good agreement between the time-dependent measurements and the simulation results obtained using this model. The validated model was thenmore » used to analyze the experimental results from the Shenguang-III prototype laser facility. More specifically, the variations of the peak radiation temperatures at different view angles with the albedo of the hohlraum, the motion of the laser spots, the closure of the laser entrance holes, and the deviation of the laser power were investigated. Furthermore, the time-dependent radiation temperature at different orientations and the drive history on the capsule were calculated. The results indicate that the radiation temperature from “U20W112” (named according to the diagnostic hole ID on the target chamber) can be used to approximately predict the drive temperature on the capsule. In addition, the influence of the capsule on the peak radiation temperature is also presented.« less

pF3D Simulations of SBS and SRS in NIF Hohlraum Experiments

NASA Astrophysics Data System (ADS)

Langer, Steven; Strozzi, David; Amendt, Peter; Chapman, Thomas; Hopkins, Laura; Kritcher, Andrea; Sepke, Scott

2016-10-01

We present simulations of stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) for NIF experiments using high foot pulses in cylindrical hohlraums and for low foot pulses in rugby-shaped hohlraums. We use pF3D, a massively-parallel, paraxial-envelope laser plasma interaction code, with plasma profiles obtained from the radiation-hydrodynamics codes Lasnex and HYDRA. We compare the simulations to experimental data for SBS and SRS power and spectrum. We also show simulated SRS and SBS intensities at the target chamber wall and report the fraction of the backscattered light that passes through and misses the lenses. Work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. Release number LLNL-ABS-697482.

Final Report for DOE Grant Number DE-SC0001481

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liang, Edison

2013-12-02

This report covers research activities, major results and publications supported by DE-SC-000-1481. This project was funded by the DOE OFES-NNSA HEDLP program. It was a joint research program between Rice University and the University of Texas at Austin. The physics of relativistic plasmas was investigated in the context of ultra-intense laser irradiation of high-Z solid targets. Laser experiments using the Texas Petawatt Laser were performed in the summers of 2011, 2012 and 2013. Numerical simulations of laser-plasma interactions were performed using Monte Carlo and Particle-in-Cell codes to design and support these experiments. Astrophysical applications of these results were also investigated.

Computer modeling and simulation in inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCrory, R.L.; Verdon, C.P.

1989-03-01

The complex hydrodynamic and transport processes associated with the implosion of an inertial confinement fusion (ICF) pellet place considerable demands on numerical simulation programs. Processes associated with implosion can usually be described using relatively simple models, but their complex interplay requires that programs model most of the relevant physical phenomena accurately. Most hydrodynamic codes used in ICF incorporate a one-fluid, two-temperature model. Electrons and ions are assumed to flow as one fluid (no charge separation). Due to the relatively weak coupling between the ions and electrons, each species is treated separately in terms of its temperature. In this paper wemore » describe some of the major components associated with an ICF hydrodynamics simulation code. To serve as an example we draw heavily on a two-dimensional Lagrangian hydrodynamic code (ORCHID) written at the University of Rochester's Laboratory for Laser Energetics. 46 refs., 19 figs., 1 tab.« less

Modeling ICF With RAGE, BHR, And The New Laser Package

NASA Astrophysics Data System (ADS)

Cliche, Dylan; Welser-Sherrill, Leslie; Haines, Brian; Mancini, Roberto

2017-10-01

Inertial Confinement Fusion (ICF) is one method used to obtain thermonuclear burn through the either direct or indirect ablation of a millimeter-scale capsule with several lasers. Although progress has been made in theory, experiment, and diagnostics, the community has yet to reach ignition. A way of investigating this is through the use of high performance computer simulations of the implosion. RAGE is an advanced 1D, 2D, and 3D radiation adaptive grid Eulerian code used to simulate hydrodynamics of a system. Due to the unstable nature of two unequal densities accelerating into one another, it is important to include a turbulence model. BHR is a turbulence model which uses Reynolds-averaged Navier-Stokes (RANS) equations to model the mixing that occurs between the shell and fusion fuel material. Until recently, it was still difficult to model direct drive experiments because there was no laser energy deposition model in RAGE. Recently, a new laser energy deposition model has been implemented using the same ray tracing method as the Mazinisin laser package used at the OMEGA laser facility at the Laboratory for Laser Energetics (LLE) in Rochester, New York. Using the new laser package along with BHR for mixing allows us to more accurately simulate ICF implosions and obtain spatially and temporally resolved information (e.g. position, temperature, density, and mix concentrations) to give insight into what is happening inside the implosion.

Proton probing of a relativistic laser interaction with near-critical plasma

NASA Astrophysics Data System (ADS)

Willingale, Louise; Zulick, C.; Thomas, A. G. R.; Maksimchuk, A.; Krushelnick, K.; Nilson, P. M.; Stoeckl, C.; Sangster, T. C.; Nazarov, W.

2014-10-01

The Omega EP laser (1000 J in 10 ps pulses) was used to investigate a relativistic intensity laser interaction with near-critical density plasma using a transverse proton beam to diagnose the large electromagnetic fields generated. A very low density foam target mounted in a washer provided the near-critical density conditions. The fields from a scaled, two-dimensional particle-in-cell simulation were inputed into a particle-tracking code to create simulated proton probe images. This allows us to understand the origins of the complex features in the experimental images, including a rapidly expanding sheath field, evidence for ponderomotive channeling and fields at the foam-washer interface. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0002028.

Modeling and simulation of RF photoinjectors for coherent light sources

NASA Astrophysics Data System (ADS)

Chen, Y.; Krasilnikov, M.; Stephan, F.; Gjonaj, E.; Weiland, T.; Dohlus, M.

2018-05-01

We propose a three-dimensional fully electromagnetic numerical approach for the simulation of RF photoinjectors for coherent light sources. The basic idea consists in incorporating a self-consistent photoemission model within a particle tracking code. The generation of electron beams in the injector is determined by the quantum efficiency (QE) of the cathode, the intensity profile of the driving laser as well as by the accelerating field and magnetic focusing conditions in the gun. The total charge emitted during an emission cycle can be limited by the space charge field at the cathode. Furthermore, the time and space dependent electromagnetic field at the cathode may induce a transient modulation of the QE due to surface barrier reduction of the emitting layer. In our modeling approach, all these effects are taken into account. The beam particles are generated dynamically according to the local QE of the cathode and the time dependent laser intensity profile. For the beam dynamics, a tracking code based on the Lienard-Wiechert retarded field formalism is employed. This code provides the single particle trajectories as well as the transient space charge field distribution at the cathode. As an application, the PITZ injector is considered. Extensive electron bunch emission simulations are carried out for different operation conditions of the injector, in the source limited as well as in the space charge limited emission regime. In both cases, fairly good agreement between measurements and simulations is obtained.

Simulation of 2D Kinetic Effects in Plasmas using the Grid Based Continuum Code LOKI

NASA Astrophysics Data System (ADS)

Banks, Jeffrey; Berger, Richard; Chapman, Tom; Brunner, Stephan

2016-10-01

Kinetic simulation of multi-dimensional plasma waves through direct discretization of the Vlasov equation is a useful tool to study many physical interactions and is particularly attractive for situations where minimal fluctuation levels are desired, for instance, when measuring growth rates of plasma wave instabilities. However, direct discretization of phase space can be computationally expensive, and as a result there are few examples of published results using Vlasov codes in more than a single configuration space dimension. In an effort to fill this gap we have developed the Eulerian-based kinetic code LOKI that evolves the Vlasov-Poisson system in 2+2-dimensional phase space. The code is designed to reduce the cost of phase-space computation by using fully 4th order accurate conservative finite differencing, while retaining excellent parallel scalability that efficiently uses large scale computing resources. In this poster I will discuss the algorithms used in the code as well as some aspects of their parallel implementation using MPI. I will also overview simulation results of basic plasma wave instabilities relevant to laser plasma interaction, which have been obtained using the code.

Modeling Laboratory Astrophysics Experiments using the CRASH code

NASA Astrophysics Data System (ADS)

Trantham, Matthew; Drake, R. P.; Grosskopf, Michael; Bauerle, Matthew; Kruanz, Carolyn; Keiter, Paul; Malamud, Guy; Crash Team

2013-10-01

The understanding of high energy density systems can be advanced by laboratory astrophysics experiments. Computer simulations can assist in the design and analysis of these experiments. The Center for Radiative Shock Hydrodynamics (CRASH) at the University of Michigan developed a code that has been used to design and analyze high-energy-density experiments on OMEGA, NIF, and other large laser facilities. This Eulerian code uses block-adaptive mesh refinement (AMR) with implicit multigroup radiation transport and electron heat conduction. This poster/talk will demonstrate some of the experiments the CRASH code has helped design or analyze including: Radiative shocks experiments, Kelvin-Helmholtz experiments, Rayleigh-Taylor experiments, plasma sheet, and interacting jets experiments. This work is funded by the Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616, by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE-FG52-09NA29548, and by the National Laser User Facility Program, grant number DE-NA0000850.

Numerical studies of the use of thin high-Z layers for reducing laser imprint in direct-drive inertial-fusion targets

NASA Astrophysics Data System (ADS)

Bates, Jason; Schmitt, Andrew; Karasik, Max; Obenschain, Steve

2012-10-01

Using the FAST code, we present numerical studies of the effect of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of directly-driven inertial-confinement-fusion (ICF) targets. Previous experimental work on the NIKE Laser Facility at the U.S. Naval Research Laboratory demonstrated that the use of high-Z layers may be efficacious in reducing laser non-uniformities imprinted on the target during the start-up phase of the implosion. Such a reduction is highly desirable in a direct-drive ICF scenario because laser non-uniformities seed hydrodynamic instabilities that can amplify during the implosion process, prevent uniform compression and spoil high gain. One of the main objectives of the present work is to assess the utility of high-Z layers for achieving greater laser uniformity in polar-drive target designs planned for the National Ignition Facility. To address this problem, new numerical routines have recently been incorporated in the FAST code, including an improved radiation-transfer package and a three-dimensional ray-tracing algorithm. We will discuss these topics, and present initial simulation results for high-Z planar-target experiments planned on the NIKE Laser Facility later this year.

Study of transport phenomena in laser-driven, non- equilibrium plasmas in the presence of external magnetic fields

NASA Astrophysics Data System (ADS)

Kemp, G. Elijah; Mariscal, D. A.; Williams, G. J.; Blue, B. E.; Colvin, J. D.; Fears, T. M.; Kerr, S. M.; May, M. J.; Moody, J. D.; Strozzi, D. J.; Lefevre, H. J.; Klein, S. R.; Kuranz, C. C.; Manuel, M. J.-E.; Gautier, D. C.; Montgomery, D. S.

2017-10-01

We present experimental and simulation results from a study of thermal transport inhibition in laser-driven, mid-Z, non-equilibrium plasmas in the presence external magnetic fields. The experiments were performed at the Jupiter Laser Facility at LLNL, where x-ray spectroscopy, proton radiography, and Brillouin backscatter data were simultaneously acquired from sub-critical-density, Ti-doped silica aerogel foams driven by a 2 ω laser at 5 ×1014 W /cm2 . External B-field strengths up to 20 T (aligned antiparallel to the laser propagation axis) were provided by a capacitor-bank-driven Helmholtz coil. Pre-shot simulations with Hydra, a radiation-magnetohydrodyanmics code, showed increasing electron plasma temperature with increasing B-field strength - the result of thermal transport inhibition perpendicular to the B-field. The influence of this thermal transport inhibition on the experimental observables as a function of external field strength and target density will be shown and compared with simulations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344 and funded by LDRD project 17-ERD-027.

Numerical simulations of the optical gain of crystalline fiber doped by rare earth and transition ion

NASA Astrophysics Data System (ADS)

Daoui, A. K.; Boubir, B.; Adouane, A.; Demagh, N.; Ghoumazi, M.

2015-02-01

A fiber laser is a laser whose gain medium is a doped fiber, although lasers whose cavity is made wholly of fibers have also been called fiber lasers. The gain media in a fiber laser is usually fiber doped with rare-earth ions, such as erbium (Er), neodymium (Nd), ytterbium (Yb), thulium (Tm), or praseodymium (Pr), which is doped into the core of the optical fiber, similar to those used to transmit telecommunications signals. Fiber lasers find many applications in materials processing, including cutting, welding, drilling, and marking metal. To maximize their market penetration, it is necessary to increase their output power. In this work, we present a detailed study based on the numerical simulation using MATLAB, of one of the principal characteristics of a fiber laser doped with rare earth ions and transition ion. The gain depends on several parameters such as the length of the doped fiber, the density, the pump power, noise, etc.). The used program resolves the state equations in this context together with those governing the light propagation phenomena. The developed code can also be used to study the dynamic operating modes of a doped fiber laser.

Thermonuclear targets for direct-drive ignition by a megajoule laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bel’kov, S. A.; Bondarenko, S. V.; Vergunova, G. A.

2015-10-15

Central ignition of a thin two-layer-shell fusion target that is directly driven by a 2-MJ profiled pulse of Nd laser second-harmonic radiation has been studied. The parameters of the target were selected so as to provide effective acceleration of the shell toward the center, which was sufficient for the onset of ignition under conditions of increased hydrodynamic stability of the ablator acceleration and compression. The aspect ratio of the inner deuterium-tritium layer of the shell does not exceed 15, provided that a major part (above 75%) of the outer layer (plastic ablator) is evaporated by the instant of maximum compression.more » The investigation is based on two series of numerical calculations that were performed using one-dimensional (1D) hydrodynamic codes. The first 1D code was used to calculate the absorption of the profiled laser-radiation pulse (including calculation of the total absorption coefficient with allowance for the inverse bremsstrahlung and resonance mechanisms) and the spatial distribution of target heating for a real geometry of irradiation using 192 laser beams in a scheme of focusing with a cubo-octahedral symmetry. The second 1D code was used for simulating the total cycle of target evolution under the action of absorbed laser radiation and for determining the thermonuclear gain that was achieved with a given target.« less

Thermal behavior in single track during selective laser melting of AlSi10Mg powder

NASA Astrophysics Data System (ADS)

Wei, Pei; Wei, Zhengying; Chen, Zhen; He, Yuyang; Du, Jun

2017-09-01

A three-dimensional model was developed to simulate the radiation heat transfer in the AlSi10Mg packed bed. The volume of fluid method (VOF) was used to capture the free surface during selective laser melting (SLM). A randomly packed powder bed was obtained using discrete element method (DEM) in Particle Flow Code (PFC). The proposed model has demonstrated a high potential to simulate the selective laser melting process (SLM) with high accuracy. In this paper, the effect of the laser scanning speed and laser power on the thermodynamic behavior of the molten pool was investigated numerically. The results show that the temperature gradient and the resultant surface tension gradient between the center and the edge of the molten pool increase with decreasing the scanning speed or increasing the laser power, thereby intensifying the Marangoni flow and attendant turbulence within the molten pool. However, at a relatively high scanning speed, a significant instability may be generated in the molten pool. The perturbation and instability in the molten pool during SLM may result in an irregular shaped track.

MITHRA 1.0: A full-wave simulation tool for free electron lasers

NASA Astrophysics Data System (ADS)

Fallahi, Arya; Yahaghi, Alireza; Kärtner, Franz X.

2018-07-01

Free Electron Lasers (FELs) are a solution for providing intense, coherent and bright radiation in the hard X-ray regime. Due to the low wall-plug efficiency of FEL facilities, it is crucial and additionally very useful to develop complete and accurate simulation tools for better optimizing a FEL interaction. The highly sophisticated dynamics involved in a FEL process was the main obstacle hindering the development of general simulation tools for this problem. We present a numerical algorithm based on finite difference time domain/Particle in cell (FDTD/PIC) in a Lorentz boosted coordinate system which is able to fulfill a full-wave simulation of a FEL process. The developed software offers a suitable tool for the analysis of FEL interactions without considering any of the usual approximations. A coordinate transformation to bunch rest frame makes the very different length scales of bunch size, optical wavelengths and the undulator period transform to values with the same order. Consequently, FDTD/PIC simulations in conjunction with efficient parallelization techniques make the full-wave simulation feasible using the available computational resources. Several examples of free electron lasers are analyzed using the developed software, the results are benchmarked based on standard FEL codes and discussed in detail.

Simulation of guided-wave ultrasound propagation in composite laminates: Benchmark comparisons of numerical codes and experiment.

PubMed

Leckey, Cara A C; Wheeler, Kevin R; Hafiychuk, Vasyl N; Hafiychuk, Halyna; Timuçin, Doğan A

2018-03-01

Ultrasonic wave methods constitute the leading physical mechanism for nondestructive evaluation (NDE) and structural health monitoring (SHM) of solid composite materials, such as carbon fiber reinforced polymer (CFRP) laminates. Computational models of ultrasonic wave excitation, propagation, and scattering in CFRP composites can be extremely valuable in designing practicable NDE and SHM hardware, software, and methodologies that accomplish the desired accuracy, reliability, efficiency, and coverage. The development and application of ultrasonic simulation approaches for composite materials is an active area of research in the field of NDE. This paper presents comparisons of guided wave simulations for CFRP composites implemented using four different simulation codes: the commercial finite element modeling (FEM) packages ABAQUS, ANSYS, and COMSOL, and a custom code executing the Elastodynamic Finite Integration Technique (EFIT). Benchmark comparisons are made between the simulation tools and both experimental laser Doppler vibrometry data and theoretical dispersion curves. A pristine and a delamination type case (Teflon insert in the experimental specimen) is studied. A summary is given of the accuracy of simulation results and the respective computational performance of the four different simulation tools. Published by Elsevier B.V.

High-Pressure Gaseous Burner (HPGB) Facility Completed for Quantitative Laser Diagnostics Calibration

NASA Technical Reports Server (NTRS)

Nguyen, Quang-Viet

2002-01-01

A gas-fueled high-pressure combustion facility with optical access, which was developed over the last 2 years, has just been completed. The High Pressure Gaseous Burner (HPGB) rig at the NASA Glenn Research Center can operate at sustained pressures up to 60 atm with a variety of gaseous fuels and liquid jet fuel. The facility is unique as it is the only continuous-flow, hydrogen-capable, 60-atm rig in the world with optical access. It will provide researchers with new insights into flame conditions that simulate the environment inside the ultra-high-pressure-ratio combustion chambers of tomorrow's advanced aircraft engines. The facility provides optical access to the flame zone, enabling the calibration of nonintrusive optical diagnostics to measure chemical species and temperature. The data from the HPGB rig enables the validation of numerical codes that simulate gas turbine combustors, such as the National Combustor Code (NCC). The validation of such numerical codes is often best achieved with nonintrusive optical diagnostic techniques that meet these goals: information-rich (multispecies) and quantitative while providing good spatial and time resolution. Achieving these goals is a challenge for most nonintrusive optical diagnostic techniques. Raman scattering is a technique that meets these challenges. Raman scattering occurs when intense laser light interacts with molecules to radiate light at a shifted wavelength (known as the Raman shift). This shift in wavelength is unique to each chemical species and provides a "fingerprint" of the different species present. The facility will first be used to gather a comprehensive data base of laser Raman spectra at high pressures. These calibration data will then be used to quantify future laser Raman measurements of chemical species concentration and temperature in this facility and other facilities that use Raman scattering.

Modeling of Adaptive Optics-Based Free-Space Communications Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilks, S C; Morris, J R; Brase, J M

2002-08-06

We introduce a wave-optics based simulation code written for air-optic laser communications links, that includes a detailed model of an adaptive optics compensation system. We present the results obtained by this model, where the phase of a communications laser beam is corrected, after it propagates through a turbulent atmosphere. The phase of the received laser beam is measured using a Shack-Hartmann wavefront sensor, and the correction method utilizes a MEMS mirror. Strehl improvement and amount of power coupled to the receiving fiber for both 1 km horizontal and 28 km slant paths are presented.

Novel space-time trellis codes for free-space optical communications using transmit laser selection.

PubMed

García-Zambrana, Antonio; Boluda-Ruiz, Rubén; Castillo-Vázquez, Carmen; Castillo-Vázquez, Beatriz

2015-09-21

In this paper, the deployment of novel space-time trellis codes (STTCs) with transmit laser selection (TLS) for free-space optical (FSO) communication systems using intensity modulation and direct detection (IM/DD) over atmospheric turbulence and misalignment fading channels is presented. Combining TLS and STTC with rate 1 bit/(s · Hz), a new code design criterion based on the use of the largest order statistics is here proposed for multiple-input/single-output (MISO) FSO systems in order to improve the diversity order gain by properly chosing the transmit lasers out of the available L lasers. Based on a pairwise error probability (PEP) analysis, closed-form asymptotic bit error-rate (BER) expressions in the range from low to high signal-to-noise ratio (SNR) are derived when the irradiance of the transmitted optical beam is susceptible to moderate-to-strong turbulence conditions, following a gamma-gamma (GG) distribution, and pointing error effects, following a misalignment fading model where the effect of beam width, detector size and jitter variance is considered. Obtained results show diversity orders of 2L and 3L when simple two-state and four-state STTCs are considered, respectively. Simulation results are further demonstrated to confirm the analytical results.

Simulated Raman Spectral Analysis of Organic Molecules

NASA Astrophysics Data System (ADS)

Lu, Lu

The advent of the laser technology in the 1960s solved the main difficulty of Raman spectroscopy, resulted in simplified Raman spectroscopy instruments and also boosted the sensitivity of the technique. Up till now, Raman spectroscopy is commonly used in chemistry and biology. As vibrational information is specific to the chemical bonds, Raman spectroscopy provides fingerprints to identify the type of molecules in the sample. In this thesis, we simulate the Raman Spectrum of organic and inorganic materials by General Atomic and Molecular Electronic Structure System (GAMESS) and Gaussian, two computational codes that perform several general chemistry calculations. We run these codes on our CPU-based high-performance cluster (HPC). Through the message passing interface (MPI), a standardized and portable message-passing system which can make the codes run in parallel, we are able to decrease the amount of time for computation and increase the sizes and capacities of systems simulated by the codes. From our simulations, we will set up a database that allows search algorithm to quickly identify N-H and O-H bonds in different materials. Our ultimate goal is to analyze and identify the spectra of organic matter compositions from meteorites and compared these spectra with terrestrial biologically-produced amino acids and residues.

Front-end simulation of injector for terawatt accumulator.

PubMed

Kropachev, G N; Balabin, A I; Kolomiets, A A; Kulevoy, T V; Pershin, V I; Shumshurov, A V

2008-02-01

A terawatt accumulator (TWAC) accelerator/storage ring complex with the laser ion source is in progress at ITEP. The new injector I4 based on the radio frequency quadrupole (RFQ) and interdigital H-mode (IH) linear accelerator is under construction. The front end of the new TWAC injector consists of a laser ion source, an extraction system, and a low energy beam transport (LEBT). The KOBRA3-INP was used for the simulation and optimization of the ion source extraction system. The optimization parameter is the maximum brightness of the beam generated by the laser ion source. Also the KOBRA3-INP code was used for LEBT investigation. The LEBT based on electrostatic grid lenses is chosen for injector I4. The results of the extraction system and LEBT investigations for ion beam matching with RFQ are presented.

Simulations of Fuel Assembly and Fast-Electron Transport in Integrated Fast-Ignition Experiments on OMEGA

NASA Astrophysics Data System (ADS)

Solodov, A. A.; Theobald, W.; Anderson, K. S.; Shvydky, A.; Epstein, R.; Betti, R.; Myatt, J. F.; Stoeckl, C.; Jarrott, L. C.; McGuffey, C.; Qiao, B.; Beg, F. N.; Wei, M. S.; Stephens, R. B.

2013-10-01

Integrated fast-ignition experiments on OMEGA benefit from improved performance of the OMEGA EP laser, including higher contrast, higher energy, and a smaller focus. Recent 8-keV, Cu-Kα flash radiography of cone-in-shell implosions and cone-tip breakout measurements showed good agreement with the 2-D radiation-hydrodynamic simulations using the code DRACO. DRACO simulations show that the fuel assembly can be further improved by optimizing the compression laser pulse, evacuating air from the shell, and by adjusting the material of the cone tip. This is found to delay the cone-tip breakout by ~220 ps and increase the core areal density from ~80 mg/cm2 in the current experiments to ~500 mg/cm2 at the time of the OMEGA EP beam arrival before the cone-tip breakout. Simulations using the code LSP of fast-electron transport in the recent integrated OMEGA experiments with Cu-doped shells will be presented. Cu-doping is added to probe the transport of fast electrons via their induced Cu K-shell fluorescent emission. This material is based upon work supported by the Department of Energy National Nuclear Security Administration DE-NA0001944 and the Office of Science under DE-FC02-04ER54789.

Effect of initial phase on error in electron energy obtained using paraxial approximation for a focused laser pulse in vacuum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Kunwar Pal, E-mail: k-psingh@yahoo.com; Department of Physics, Shri Venkateshwara University, Gajraula, Amroha, Uttar Pradesh 244236; Arya, Rashmi

2015-09-14

We have investigated the effect of initial phase on error in electron energy obtained using paraxial approximation to study electron acceleration by a focused laser pulse in vacuum using a three dimensional test-particle simulation code. The error is obtained by comparing the energy of the electron for paraxial approximation and seventh-order correction description of the fields of Gaussian laser. The paraxial approximation predicts wrong laser divergence and wrong electron escape time from the pulse which leads to prediction of higher energy. The error shows strong phase dependence for the electrons lying along the axis of the laser for linearly polarizedmore » laser pulse. The relative error may be significant for some specific values of initial phase even at moderate values of laser spot sizes. The error does not show initial phase dependence for a circularly laser pulse.« less

3D Vectorial Time Domain Computational Integrated Photonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kallman, J S; Bond, T C; Koning, J M

2007-02-16

The design of integrated photonic structures poses considerable challenges. 3D-Time-Domain design tools are fundamental in enabling technologies such as all-optical logic, photonic bandgap sensors, THz imaging, and fast radiation diagnostics. Such technologies are essential to LLNL and WFO sponsors for a broad range of applications: encryption for communications and surveillance sensors (NSA, NAI and IDIV/PAT); high density optical interconnects for high-performance computing (ASCI); high-bandwidth instrumentation for NIF diagnostics; micro-sensor development for weapon miniaturization within the Stockpile Stewardship and DNT programs; and applications within HSO for CBNP detection devices. While there exist a number of photonics simulation tools on the market,more » they primarily model devices of interest to the communications industry. We saw the need to extend our previous software to match the Laboratory's unique emerging needs. These include modeling novel material effects (such as those of radiation induced carrier concentrations on refractive index) and device configurations (RadTracker bulk optics with radiation induced details, Optical Logic edge emitting lasers with lateral optical inputs). In addition we foresaw significant advantages to expanding our own internal simulation codes: parallel supercomputing could be incorporated from the start, and the simulation source code would be accessible for modification and extension. This work addressed Engineering's Simulation Technology Focus Area, specifically photonics. Problems addressed from the Engineering roadmap of the time included modeling the Auston switch (an important THz source/receiver), modeling Vertical Cavity Surface Emitting Lasers (VCSELs, which had been envisioned as part of fast radiation sensors), and multi-scale modeling of optical systems (for a variety of applications). We proposed to develop novel techniques to numerically solve the 3D multi-scale propagation problem for both the microchip laser logic devices as well as devices characterized by electromagnetic (EM) propagation in nonlinear materials with time-varying parameters. The deliverables for this project were extended versions of the laser logic device code Quench2D and the EM propagation code EMsolve with new modules containing the novel solutions incorporated by taking advantage of the existing software interface and structured computational modules. Our approach was multi-faceted since no single methodology can always satisfy the tradeoff between model runtime and accuracy requirements. We divided the problems to be solved into two main categories: those that required Full Wave Methods and those that could be modeled using Approximate Methods. Full Wave techniques are useful in situations where Maxwell's equations are not separable (or the problem is small in space and time), while approximate techniques can treat many of the remaining cases.« less

Laser manipulation of atomic and molecular flows

NASA Astrophysics Data System (ADS)

Lilly, Taylor C.

The continuing advance of laser technology enables a range of broadly applicable, laser-based flow manipulation techniques. The characteristics of these laser-based flow manipulations suggest that they may augment, or be superior to, such traditional electro-mechanical methods as ionic flow control, shock tubes, and small scale wind tunnels. In this study, methodology was developed for investigating laser flow manipulation techniques, and testing their feasibility for a number of aerospace, basic physics, and micro technology applications. Theories for laser-atom and laser-molecule interactions have been under development since the advent of laser technology. The theories have yet to be adequately integrated into kinetic flow solvers. Realizing this integration would greatly enhance the scaling of laser-species interactions beyond the realm of ultra-cold atomic physics. This goal was realized in the present study. A representative numerical investigation, of laser-based neutral atomic and molecular flow manipulations, was conducted using near-resonant and non-resonant laser fields. To simulate the laser interactions over a range of laser and flow conditions, the following tools were employed: a custom collisionless gas particle trajectory code and a specifically modified version of the Direct Simulation Monte Carlo statistical kinetic solver known as SMILE. In addition to the numerical investigations, a validating experiment was conducted. The experimental results showed good agreement with the numerical simulations when experimental parameters, such as finite laser line width, were taken into account. Several areas of interest were addressed: laser induced neutral flow steering, collimation, direct flow acceleration, and neutral gas heating. Near-resonant continuous wave laser, and non-resonant pulsed laser, interactions with cesium and nitrogen were simulated. These simulations showed trends and some limitations associated with these interactions, used for flow steering and collimation. The use of one of these interactions, the induced dipole force, was extended beyond a single Gaussian laser field. The interference patterns associated with counter-propagating laser fields, or "optical lattices," were shown to be capable of both direct species acceleration and gas heating. This study resulted in predictions for a continuous, resonant laser-cesium flow with accelerations of 106 m/s2. For this circumstance, a future straightforward proof of principle experiment has been identified. To demonstrate non-resonant gas heating, a series of pulsed optical lattices were simulated interacting with neutral non-polar species. An optimum time between pulses was identified as a function of the collisional relaxation time. Using the optimum time between pulses, molecular nitrogen simulations showed an increase in gas temperature from 300 K to 2470 K at 1 atm, for 50 successive optical lattice pulses. A second proof of principle experiment was identified for future investigation.

The ePLAS Code for Ignition Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mason, Rodney J

2012-09-20

Inertial Confinement Fusion (ICF) presents unique opportunities for the extraction of clean energy from Fusion. Intense lasers and particle beams can create and interact with such plasmas, potentially yielding sufficient energy to satisfy all our national needs. However, few models are available to help aid the scientific community in the study and optimization of such interactions. This project enhanced and disseminated the computer code ePLAS for the early understanding and control of Ignition in ICF. ePLAS is a unique simulation code that tracks the transport of laser light to a target, the absorption of that light resulting in the generationmore » and transport of hot electrons, and the heating and flow dynamics of the background plasma. It uses an implicit electromagnetic field-solving method to greatly reduce computing demands, so that useful target interaction studies can often be completed in 15 minutes on a portable 2.1 GHz PC. The code permits the rapid scoping of calculations for the optimization of laser target interactions aimed at fusion. Recent efforts have initiated the use of analytic equations of state (EOS), K-alpha image rendering graphics, allocatable memory for source-free usage, and adaption to the latest Mac and Linux Operating Systems. The speed and utility of ePLAS are unequaled in the ICF simulation community. This project evaluated the effects of its new EOSs on target heating, compared fluid and particle models for the ions, initiated the simultaneous use of both ion models in the code, and studied long time scale 500 ps hot electron deposition for shock ignition. ePLAS has been granted EAR99 export control status, permitting export without a license to most foreign countries. Beta-test versions of ePLAS have been granted to several Universities and Commercial users. The net Project was aimed at achieving early success in the laboratory ignition of thermonuclear targets and the mastery of controlled fusion power for the nation.« less

ICPP: Relativistic Plasma Physics with Ultra-Short High-Intensity Laser Pulses

NASA Astrophysics Data System (ADS)

Meyer-Ter-Vehn, Juergen

2000-10-01

Recent progress in generating ultra-short high-intensity laser pulses has opened a new branch of relativistic plasma physics, which is discussed in this talk in terms of particle-in-cell (PIC) simulations. These pulses create small plasma volumes of high-density plasma with plasma fields above 10^12 V/m and 10^8 Gauss. At intensities beyond 10^18 W/cm^2, now available from table-top systems, they drive relativistic electron currents in self-focussing plasma channels. These currents are close to the Alfven limit and allow to study relativistic current filamentation. A most remarkable feature is the generation of well collimated relativistic electron beams emerging from the channels with energies up to GeV. In dense matter they trigger cascades of gamma-rays, e^+e^- pairs, and a host of nuclear and particle processes. One of the applications may be fast ignition of compressed inertial fusion targets. Above 10^23 W/cm^2, expected to be achieved in the future, solid-density matter becomes relativistically transparent for optical light, and the acceleration of protons to multi-GeV energies is predicted in plasma layers less than 1 mm thick. These results open completely new perspectives for plasma-based accelerator schemes. Three-dimensional PIC simulations turn out to be the superior tool to explore the relativistic plasma kinetics at such intensities. Results obtained with the VLPL code [1] are presented. Different mechanisms of particle acceleration are discussed. Both laser wakefield and direct laser acceleration in plasma channels (by a mechanism similar to inverse free electron lasers) have been identified. The latter describes recent MPQ experimental results. [1] A. Pukhov, J. Plasma Physics 61, 425 - 433 (1999): Three-dimensional electromagnetic relativistic particle-in-cell code VLPL (Virtual Laser Plasma Laboratory).

Laser program annual report, 1980

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coleman, L.W.; Krupke, W.F.; Strack, J.R.

1981-06-01

Volume 2 contains five sections that cover the areas of target design, target fabrication, diagnostics, and fusion experiments. Section 3 reports on target design activities, plasma theory and simulation, code development, and atomic theory. Section 4 presents the accomplishments of the Target Fabrication Group, Section 5 contains the results of our diagnostics development, and Section 6 describes advances made in the management and analysis of experimental data. Finally, Section 7 in Volume 2 reports the results of laser target experiments conducted during the year.

Numerical study of core formation of asymmetrically driven cone-guided targets

DOE PAGES

Sawada, Hiroshi; Sakagami, Hitoshi

2017-09-22

Compression of a directly driven fast ignition cone-sphere target with a finite number of laser beams is numerically studied using a three-dimensional hydrodynamics code IMPACT-3D. The formation of a dense plasma core is simulated for 12-, 9-, 6-, and 4-beam configurations of the GEKKO XII laser. The complex 3D shapes of the cores are analyzed by elucidating synthetic 2D x-ray radiographic images in two orthogonal directions. Finally, the simulated x-ray images show significant differences in the core shape between the two viewing directions and rotation of the stagnating core axis in the top view for the axisymmetric 9- and 6-beammore » configurations.« less

Numerical study of core formation of asymmetrically driven cone-guided targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawada, Hiroshi; Sakagami, Hitoshi

Compression of a directly driven fast ignition cone-sphere target with a finite number of laser beams is numerically studied using a three-dimensional hydrodynamics code IMPACT-3D. The formation of a dense plasma core is simulated for 12-, 9-, 6-, and 4-beam configurations of the GEKKO XII laser. The complex 3D shapes of the cores are analyzed by elucidating synthetic 2D x-ray radiographic images in two orthogonal directions. Finally, the simulated x-ray images show significant differences in the core shape between the two viewing directions and rotation of the stagnating core axis in the top view for the axisymmetric 9- and 6-beammore » configurations.« less

Generation of bright attosecond x-ray pulse trains via Thomson scattering from laser-plasma accelerators.

PubMed

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.

Experimental characterization of an ultra-fast Thomson scattering x-ray source with three-dimensional time and frequency-domain analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuba, J; Slaughter, D R; Fittinghoff, D N

We present a detailed comparison of the measured characteristics of Thomson backscattered x-rays produced at the PLEIADES (Picosecond Laser-Electron Interaction for the Dynamic Evaluation of Structures) facility at Lawrence Livermore National Laboratory to predicted results from a newly developed, fully three-dimensional time and frequency-domain code. Based on the relativistic differential cross section, this code has the capability to calculate time and space dependent spectra of the x-ray photons produced from linear Thomson scattering for both bandwidth-limited and chirped incident laser pulses. Spectral broadening of the scattered x-ray pulse resulting from the incident laser bandwidth, perpendicular wave vector components in themore » laser focus, and the transverse and longitudinal phase space of the electron beam are included. Electron beam energy, energy spread, and transverse phase space measurements of the electron beam at the interaction point are presented, and the corresponding predicted x-ray characteristics are determined. In addition, time-integrated measurements of the x-rays produced from the interaction are presented, and shown to agree well with the simulations.« less

High harmonic generation in underdense plasmas by intense laser pulses with orbital angular momentum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mendonça, J. T., E-mail: josetitomend@gmail.com; Vieira, J., E-mail: jorge.vieira@ist.utl.pt

We study high harmonic generation produced by twisted laser pulses, with orbital angular momentum in the relativistic regime, for pulse propagation in underdense plasma. We consider fast time scale processes associated with an ultra-short pulse, where the ion motion can be neglected. We use both analytical models and numerical simulations using a relativistic particle-in-cell code. The present description is valid for relativistic laser intensities, when the normalized field amplitude is much larger than one, a ≫ 1. We also discuss two distinct processes associated with linear and circular polarization. Using both analytical solutions and particle-in-cell simulations, we are able tomore » show that, for laser pulses in a well defined Laguerre-Gauss mode, angular momentum conservation is observed during the process of harmonic generation. Intensity modulation of the harmonic spectrum is also verified, as imposed by the nonlinear time-scale for energy transfer between different harmonics.« less

Coupling of laser energy into plasma channels

NASA Astrophysics Data System (ADS)

Dimitrov, D. A.; Giacone, R. E.; Bruhwiler, D. L.; Busby, R.; Cary, J. R.; Geddes, C. G. R.; Esarey, E.; Leemans, W. P.

2007-04-01

Diffractive spreading of a laser pulse imposes severe limitations on the acceleration length and maximum electron energy in the laser wake field accelerator (LWFA). Optical guiding of a laser pulse via plasma channels can extend the laser-plasma interaction distance over many Rayleigh lengths. Energy efficient coupling of laser pulses into and through plasma channels is very important for optimal LWFA performance. Results from simulation parameter studies on channel guiding using the particle-in-cell (PIC) code VORPAL [C. Nieter and J. R. Cary, J. Comput. Phys. 196, 448 (2004)] are presented and discussed. The effects that density ramp length and the position of the laser pulse focus have on coupling into channels are considered. Moreover, the effect of laser energy leakage out of the channel domain and the effects of tunneling ionization of a neutral gas on the guided laser pulse are also investigated. Power spectral diagnostics were developed and used to separate pump depletion from energy leakage. The results of these simulations show that increasing the density ramp length decreases the efficiency of coupling a laser pulse to a channel and increases the energy loss when the pulse is vacuum focused at the channel entrance. Then, large spot size oscillations result in increased energy leakage. To further analyze the coupling, a differential equation is derived for the laser spot size evolution in the plasma density ramp and channel profiles are simulated. From the numerical solution of this equation, the optimal spot size and location for coupling into a plasma channel with a density ramp are determined. This result is confirmed by the PIC simulations. They show that specifying a vacuum focus location of the pulse in front of the top of the density ramp leads to an actual focus at the top of the ramp due to plasma focusing, resulting in reduced spot size oscillations. In this case, the leakage is significantly reduced and is negligibly affected by ramp length, allowing for efficient use of channels with long ramps.

Simulations of laser-driven ion acceleration from a thin CH target

NASA Astrophysics Data System (ADS)

Park, Jaehong; Bulanov, Stepan; Ji, Qing; Steinke, Sven; Treffert, Franziska; Vay, Jean-Luc; Schenkel, Thomas; Esarey, Eric; Leemans, Wim; Vincenti, Henri

2017-10-01

2D and 3D computer simulations of laser driven ion acceleration from a thin CH foil using code WARP were performed. As the foil thickness varies from a few nm to μm, the simulations confirm that the acceleration mechanism transitions from the RPA (radiation pressure acceleration) to the TNSA (target normal sheath acceleration). In the TNSA regime, with the CH target thickness of 1 μ m and a pre-plasma ahead of the target, the simulations show the production of the collimated proton beam with the maximum energy of about 10 MeV. This agrees with the experimental results obtained at the BELLA laser facility (I 5 × 18 W / cm2 , λ = 800 nm). Furthermore, the maximum proton energy dependence on different setups of the initialization, i.e., different angles of the laser incidence from the target normal axis, different gradient scales and distributions of the pre-plasma, was explored. This work was supported by LDRD funding from LBNL, provided by the U.S. DOE under Contract No. DE-AC02-05CH11231, and used resources of the NERSC, a DOE office of Science User Facility supported by the U.S. DOE under Contract No. DE-AC02-05CH11231.

Nonlinear plasma wave models in 3D fluid simulations of laser-plasma interaction

NASA Astrophysics Data System (ADS)

Chapman, Thomas; Berger, Richard; Arrighi, Bill; Langer, Steve; Banks, Jeffrey; Brunner, Stephan

2017-10-01

Simulations of laser-plasma interaction (LPI) in inertial confinement fusion (ICF) conditions require multi-mm spatial scales due to the typical laser beam size and durations of order 100 ps in order for numerical laser reflectivities to converge. To be computationally achievable, these scales necessitate a fluid-like treatment of light and plasma waves with a spatial grid size on the order of the light wave length. Plasma waves experience many nonlinear phenomena not naturally described by a fluid treatment, such as frequency shifts induced by trapping, a nonlinear (typically suppressed) Landau damping, and mode couplings leading to instabilities that can cause the plasma wave to decay rapidly. These processes affect the onset and saturation of stimulated Raman and Brillouin scattering, and are of direct interest to the modeling and prediction of deleterious LPI in ICF. It is not currently computationally feasible to simulate these Debye length-scale phenomena in 3D across experimental scales. Analytically-derived and/or numerically benchmarked models of processes occurring at scales finer than the fluid simulation grid offer a path forward. We demonstrate the impact of a range of kinetic processes on plasma reflectivity via models included in the LPI simulation code pF3D. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

STUDIES OF A FREE ELECTRON LASER DRIVEN BY A LASER-PLASMA ACCELERATOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montgomery, A.; Schroeder, C.; Fawley, W.

A free electron laser (FEL) uses an undulator, a set of alternating magnets producing a periodic magnetic fi eld, to stimulate emission of coherent radiation from a relativistic electron beam. The Lasers, Optical Accelerator Systems Integrated Studies (LOASIS) group at Lawrence Berkeley National Laboratory (LBNL) will use an innovative laserplasma wakefi eld accelerator to produce an electron beam to drive a proposed FEL. In order to optimize the FEL performance, the dependence on electron beam and undulator parameters must be understood. Numerical modeling of the FEL using the simulation code GINGER predicts the experimental results for given input parameters. Amongmore » the parameters studied were electron beam energy spread, emittance, and mismatch with the undulator focusing. Vacuum-chamber wakefi elds were also simulated to study their effect on FEL performance. Energy spread was found to be the most infl uential factor, with output FEL radiation power sharply decreasing for relative energy spreads greater than 0.33%. Vacuum chamber wakefi elds and beam mismatch had little effect on the simulated LOASIS FEL at the currents considered. This study concludes that continued improvement of the laser-plasma wakefi eld accelerator electron beam will allow the LOASIS FEL to operate in an optimal regime, producing high-quality XUV and x-ray pulses.« less

Longitudinal space charge assisted echo seeding of a free-electron laser with laser-spoiler noise suppression

NASA Astrophysics Data System (ADS)

Hacker, Kirsten

2014-09-01

Seed lasers are employed to improve the temporal coherence of free-electron laser (FEL) light. However, when these seed pulses are short relative to the particle bunch, the noisy, temporally incoherent radiation from the unseeded electrons can overwhelm the coherent, seeded radiation. In this paper, a technique to seed a particle bunch with an external laser is presented in which a new mechanism to improve the contrast between coherent and incoherent free electron laser radiation is employed together with a novel, simplified echo-seeding method. The concept relies on a combination of longitudinal space charge wakes and an echo-seeding technique to make a short, coherent pulse of FEL light together with noise background suppression. Several different simulation codes are used to illustrate the concept with conditions at the soft x-ray free-electron laser in Hamburg, FLASH.

Status and future plans for open source QuickPIC

NASA Astrophysics Data System (ADS)

An, Weiming; Decyk, Viktor; Mori, Warren

2017-10-01

QuickPIC is a three dimensional (3D) quasi-static particle-in-cell (PIC) code developed based on the UPIC framework. It can be used for efficiently modeling plasma based accelerator (PBA) problems. With quasi-static approximation, QuickPIC can use different time scales for calculating the beam (or laser) evolution and the plasma response, and a 3D plasma wake field can be simulated using a two-dimensional (2D) PIC code where the time variable is ξ = ct - z and z is the beam propagation direction. QuickPIC can be thousand times faster than the normal PIC code when simulating the PBA. It uses an MPI/OpenMP hybrid parallel algorithm, which can be run on either a laptop or the largest supercomputer. The open source QuickPIC is an object-oriented program with high level classes written in Fortran 2003. It can be found at https://github.com/UCLA-Plasma-Simulation-Group/QuickPIC-OpenSource.git

Hydrocode and Molecular Dynamics modelling of uniaxial shock wave experiments on Silicon

NASA Astrophysics Data System (ADS)

Stubley, Paul; McGonegle, David; Patel, Shamim; Suggit, Matthew; Wark, Justin; Higginbotham, Andrew; Comley, Andrew; Foster, John; Rothman, Steve; Eggert, Jon; Kalantar, Dan; Smith, Ray

2015-06-01

Recent experiments have provided further evidence that the response of silicon to shock compression has anomalous properties, not described by the usual two-wave elastic-plastic response. A recent experimental campaign on the Orion laser in particular has indicated a complex multi-wave response. While Molecular Dynamics (MD) simulations can offer a detailed insight into the response of crystals to uniaxial compression, they are extremely computationally expensive. For this reason, we are adapting a simple quasi-2D hydrodynamics code to capture phase change under uniaxial compression, and the intervening mixed phase region, keeping track of the stresses and strains in each of the phases. This strain information is of such importance because a large number of shock experiments use diffraction as a key diagnostic, and these diffraction patterns depend solely on the elastic strains in the sample. We present here a comparison of the new hydrodynamics code with MD simulations, and show that the simulated diffraction taken from the code agrees qualitatively with measured diffraction from our recent Orion campaign.

Benchmarking of Computational Models for NDE and SHM of Composites

NASA Technical Reports Server (NTRS)

Wheeler, Kevin; Leckey, Cara; Hafiychuk, Vasyl; Juarez, Peter; Timucin, Dogan; Schuet, Stefan; Hafiychuk, Halyna

2016-01-01

Ultrasonic wave phenomena constitute the leading physical mechanism for nondestructive evaluation (NDE) and structural health monitoring (SHM) of solid composite materials such as carbon-fiber-reinforced polymer (CFRP) laminates. Computational models of ultrasonic guided-wave excitation, propagation, scattering, and detection in quasi-isotropic laminates can be extremely valuable in designing practically realizable NDE and SHM hardware and software with desired accuracy, reliability, efficiency, and coverage. This paper presents comparisons of guided-wave simulations for CFRP composites implemented using three different simulation codes: two commercial finite-element analysis packages, COMSOL and ABAQUS, and a custom code implementing the Elastodynamic Finite Integration Technique (EFIT). Comparisons are also made to experimental laser Doppler vibrometry data and theoretical dispersion curves.

The role of hot electrons in the dynamics of a laser-driven strong converging shock

DOE PAGES

Llor Aisa, E.; Ribeyre, X.; Duchateau, G.; ...

2017-11-30

Experiments on strong shock excitation in spherical plastic targets conducted at the Omega Laser Facility are interpreted with the radiation–hydrodynamics code CHIC to account for parametric instabilities excitation and hot-electron generation. The effects of hot electrons on the shock-pressure amplification and upstream preheat are analyzed. In this study, it is demonstrated that both effects contribute to an increase in shock velocity. Comparison of the measured laser reflectivity and shock flash time with numerical simulations make it possible to reconstitute the time history of the ablation and shock pressures. Finally, consequences of this analysis for the shock-ignition target design are discussed.

The role of hot electrons in the dynamics of a laser-driven strong converging shock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Llor Aisa, E.; Ribeyre, X.; Duchateau, G.

Experiments on strong shock excitation in spherical plastic targets conducted at the Omega Laser Facility are interpreted with the radiation–hydrodynamics code CHIC to account for parametric instabilities excitation and hot-electron generation. The effects of hot electrons on the shock-pressure amplification and upstream preheat are analyzed. In this study, it is demonstrated that both effects contribute to an increase in shock velocity. Comparison of the measured laser reflectivity and shock flash time with numerical simulations make it possible to reconstitute the time history of the ablation and shock pressures. Finally, consequences of this analysis for the shock-ignition target design are discussed.

Direct Laser Acceleration in Laser Wakefield Accelerators

NASA Astrophysics Data System (ADS)

Shaw, J. L.; Froula, D. H.; Marsh, K. A.; Joshi, C.; Lemos, N.

2017-10-01

The direct laser acceleration (DLA) of electrons in a laser wakefield accelerator (LWFA) has been investigated. We show that when there is a significant overlap between the drive laser and the trapped electrons in a LWFA cavity, the accelerating electrons can gain energy from the DLA mechanism in addition to LWFA. The properties of the electron beams produced in a LWFA, where the electrons are injected by ionization injection, have been investigated using particle-in-cell (PIC) code simulations. Particle tracking was used to demonstrate the presence of DLA in LWFA. Further PIC simulations comparing LWFA with and without DLA show that the presence of DLA can lead to electron beams that have maximum energies that exceed the estimates given by the theory for the ideal blowout regime. The magnitude of the contribution of DLA to the energy gained by the electron was found to be on the order of the LWFA contribution. The presence of DLA in a LWFA can also lead to enhanced betatron oscillation amplitudes and increased divergence in the direction of the laser polarization. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Numerical Simulation of Laser Ablative Shock Waves From Aluminum in Presence of Helium Gas At Different Ambient Pressures

NASA Astrophysics Data System (ADS)

Paturi, Prem Kiran; Durvasula, P. S. L. Kameswari; S, Sai Shiva; Acrhem, University Of Hyderabad Team

2017-06-01

A two dimensional comparative study of Laser Ablative Shock Wave into the Aluminum target in the presence of Helium gas at different ambient pressures over a range of 690 - 105 Pa performed using FLASH hydrodynamic codes will be presented. The irradiation of Aluminum target (thickness 2 mm and radius 3 mm) with a 7 ns laser pulse of energy 175 mJ, spot size of 150 µm on the target surface at a wavelength of 532 nm at normal incidence is simulated. Helium gas enclosed in a chamber of height 3 mm and width 3 mm. The electron-ion inverse bremsstrahlung absorption coefficient is considered in the laser energy deposition process. The simulation was performed over a duration of 1 μs. It was observed that an ablative shock is launched into the Helium gas for the pressures of 0.5 atm and above. However, for pressure less than the 0.5 atm the plasma expanded into the He gas upto 12ns and after which due to pressure equilibration with the surroundings and plume splitting shock wave is launched in to Al. Authors acknowledge funding from DRDO, India.

Numerical analysis of experiments on the generation of shock waves in aluminium under indirect (X-ray) action on the Iskra-5 facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bondarenko, S V; Dolgoleva, G V; Novikova, E A

The dynamics of laser and X-ray radiation fields in experiments with cylindrical converter boxes (illuminators), which had earlier been carried out on the Iskra-5 laser facility (the second harmonic of iodine laser radiation, {lambda} = 0.66 {mu}m) was investigated in a sector approximation using the SND-LIRA numerical technique. In these experiments, the X-ray radiation temperature in the box was determined by measuring the velocity of the shock wave generated in the sample under investigation, which was located at the end of the cylindrical illuminator. Through simulations were made using the SND-LIRA code, which took into account the absorption of lasermore » driver radiation at the box walls, the production of quasithermal radiation, as well as the formation and propagation of the shock wave in the sample under investigation. An analysis of the experiments permits determining the electron thermal flux limiter f: for f = 0.03 it is possible to match the experimental scaling data for X-ray in-box radiation temperature to the data of our simulations. The shock velocities obtained from the simulations are also consistent with experimental data. In particular, in the experiment with six laser beams (and a laser energy E{sub L} = 1380 J introduced into the box) the velocity of the shock front (determined from the position of a laser mark) after passage through a 50-{mu}m thick base aluminium layer was equal to 35{+-}1.6 km s{sup -1}, and in simulations to 36 km s{sup -1}. In the experiment with four laser beams (for E{sub L} = 850 J) the shock velocity (measured from the difference of transit times through the base aluminium layer and an additional thin aluminium platelet) was equal to 30{+-}3.6 km s{sup -1}, and in simulations to 30 km s{sup -1}. (interaction of laser radiation with matter)« less

Experimental benchmark for an improved simulation of absolute soft-x-ray emission from polystyrene targets irradiated with the Nike laser.

PubMed

Weaver, J L; Busquet, M; Colombant, D G; Mostovych, A N; Feldman, U; Klapisch, M; Seely, J F; Brown, C; Holland, G

2005-02-04

Absolutely calibrated, time-resolved spectral intensity measurements of soft-x-ray emission (hnu approximately 0.1-1.0 keV) from laser-irradiated polystyrene targets are compared to radiation-hydrodynamic simulations that include our new postprocessor, Virtual Spectro. This new capability allows a unified, detailed treatment of atomic physics and radiative transfer in nonlocal thermodynamic equilibrium conditions for simple spectra from low-Z materials as well as complex spectra from high-Z materials. The excellent agreement (within a factor of approximately 1.5) demonstrates the powerful predictive capability of the codes for the complex conditions in the ablating plasma. A comparison to data with high spectral resolution (E/deltaE approximately 1000) emphasizes the importance of including radiation coupling in the quantitative simulation of emission spectra.

Performance of the x-ray free-electron laser oscillator with crystal cavity

NASA Astrophysics Data System (ADS)

Lindberg, R. R.; Kim, K.-J.; Shvyd'Ko, Yu.; Fawley, W. M.

2011-01-01

Simulations of the x-ray free-electron laser (FEL) oscillator are presented that include the frequency-dependent Bragg crystal reflectivity and the transverse diffraction and focusing using the two-dimensional FEL code GINGER. A review of the physics of Bragg crystal reflectors and the x-ray FEL oscillator is made, followed by a discussion of its numerical implementation in GINGER. The simulation results for a two-crystal cavity and realistic FEL parameters indicate ˜109 photons in a nearly Fourier-limited, ps pulse. Compressing the electron beam to 100 A and 100 fs results in comparable x-ray characteristics for relaxed beam emittance, energy spread, and/or undulator parameters, albeit in a larger radiation bandwidth. Finally, preliminary simulation results indicate that the four-crystal FEL cavity can be tuned in energy over a range of a few percent.

Preliminary numerical investigation of bandwidth effects on CBET using the LPSE-CBET code

NASA Astrophysics Data System (ADS)

Bates, Jason; Myatt, Jason; Shaw, John; Weaver, James; Obenschain, Keith; Lehmberg, Robert; Obenschain, Steve

2016-10-01

Cross beam energy transfer (CBET) is a significant energy-loss mechanism for direct-drive implosions on the OMEGA laser facility. Recently, a working group that includes participants from the Laboratory for Laser Energetics (LLE) at the University of Rochester and the U.S. Naval Research Laboratory (NRL) was formed to investigate strategies for ameliorating the deleterious effects of CBET. As part of this collaboration, the wave-based code LPSE-CBET developed at LLE has been made available to researchers at NRL and is being used to study the feasibility of suppressing CBET through the enhancement of laser bandwidth by stimulated rotational Raman scattering (SRRS). In this poster, we present some preliminary results on this subject. In particular, we discuss initial efforts to evaluate mitigation levels of 4 discrete Stokes lines from SRRS in air and compare our findings with ray-based simulation results of wavelength shifted (-6Å ,0, +6Å) driver-lines on OMEGA. Work Supported by DoE/NNSA.

Spectroscopic diagnostics of tungsten-doped CH plasmas

NASA Astrophysics Data System (ADS)

Klapisch, M.; Colombant, D.; Lehecka, T.

1998-11-01

Spectra of CH with different concentrations of W dopant and laser intensities ( 2.5-10 x10^12 W/cm^2 ) were obtained at NRL with the Nike Laser. They were recorded in the 100-500 eV range with an XUV grating spectrometer. The hydrodynamic simulations are performed with the 1D code FAST1D(J. H. Gardner et al., Phys. Plasmas, 5, May (1998).) where non LTE effects are introduced by Busquet's model( M. Busquet, Phys. Fluids B, 5, 4191 (1993); M. Klapisch, A. Bar-Shalom, J. Oreg and D. Colombant, Phys. Plasmas, 5, May (1998).). They are then post-processed with TRANSPEC( O. Peyrusse, J. Quant. Spectrosc. Radiat. Transfer, 51, 281 (1994)), a time dependent collisional radiative code with radiation coupling. The necessary atomic data are obtained from the HULLAC code( M. Klapisch and A. Bar-Shalom, J. Quant. Spectrosc. Radiat. Transfer, 58, 687 (1997).). The post processing and diagnostics were performed on carbon lines and the results are compared with the experimental data.

Particle-in-Cell laser-plasma simulation on Xeon Phi coprocessors

NASA Astrophysics Data System (ADS)

Surmin, I. A.; Bastrakov, S. I.; Efimenko, E. S.; Gonoskov, A. A.; Korzhimanov, A. V.; Meyerov, I. B.

2016-05-01

This paper concerns the development of a high-performance implementation of the Particle-in-Cell method for plasma simulation on Intel Xeon Phi coprocessors. We discuss the suitability of the method for Xeon Phi architecture and present our experience in the porting and optimization of the existing parallel Particle-in-Cell code PICADOR. Direct porting without code modification gives performance on Xeon Phi close to that of an 8-core CPU on a benchmark problem with 50 particles per cell. We demonstrate step-by-step optimization techniques, such as improving data locality, enhancing parallelization efficiency and vectorization leading to an overall 4.2 × speedup on CPU and 7.5 × on Xeon Phi compared to the baseline version. The optimized version achieves 16.9 ns per particle update on an Intel Xeon E5-2660 CPU and 9.3 ns per particle update on an Intel Xeon Phi 5110P. For a real problem of laser ion acceleration in targets with surface grating, where a large number of macroparticles per cell is required, the speedup of Xeon Phi compared to CPU is 1.6 ×.

MPI parallelization of Vlasov codes for the simulation of nonlinear laser-plasma interactions

NASA Astrophysics Data System (ADS)

Savchenko, V.; Won, K.; Afeyan, B.; Decyk, V.; Albrecht-Marc, M.; Ghizzo, A.; Bertrand, P.

2003-10-01

The simulation of optical mixing driven KEEN waves [1] and electron plasma waves [1] in laser-produced plasmas require nonlinear kinetic models and massive parallelization. We use Massage Passing Interface (MPI) libraries and Appleseed [2] to solve the Vlasov Poisson system of equations on an 8 node dual processor MAC G4 cluster. We use the semi-Lagrangian time splitting method [3]. It requires only row-column exchanges in the global data redistribution, minimizing the total number of communications between processors. Recurrent communication patterns for 2D FFTs involves global transposition. In the Vlasov-Maxwell case, we use splitting into two 1D spatial advections and a 2D momentum advection [4]. Discretized momentum advection equations have a double loop structure with the outer index being assigned to different processors. We adhere to a code structure with separate routines for calculations and data management for parallel computations. [1] B. Afeyan et al., IFSA 2003 Conference Proceedings, Monterey, CA [2] V. K. Decyk, Computers in Physics, 7, 418 (1993) [3] Sonnendrucker et al., JCP 149, 201 (1998) [4] Begue et al., JCP 151, 458 (1999)

Interactive computer modeling of combustion chemistry and coalescence-dispersion modeling of turbulent combustion

NASA Technical Reports Server (NTRS)

Pratt, D. T.

1984-01-01

An interactive computer code for simulation of a high-intensity turbulent combustor as a single point inhomogeneous stirred reactor was developed from an existing batch processing computer code CDPSR. The interactive CDPSR code was used as a guide for interpretation and direction of DOE-sponsored companion experiments utilizing Xenon tracer with optical laser diagnostic techniques to experimentally determine the appropriate mixing frequency, and for validation of CDPSR as a mixing-chemistry model for a laboratory jet-stirred reactor. The coalescence-dispersion model for finite rate mixing was incorporated into an existing interactive code AVCO-MARK I, to enable simulation of a combustor as a modular array of stirred flow and plug flow elements, each having a prescribed finite mixing frequency, or axial distribution of mixing frequency, as appropriate. Further increase the speed and reliability of the batch kinetics integrator code CREKID was increased by rewriting in vectorized form for execution on a vector or parallel processor, and by incorporating numerical techniques which enhance execution speed by permitting specification of a very low accuracy tolerance.

View Factor and Radiation-Hydrodynamic Simulations of Gas-Filled Outer-Quad-Only Hohlraums at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Young, Christopher; Meezan, Nathan; Landen, Otto

2017-10-01

A cylindrical National Ignition Facility hohlraum irradiated exclusively by NOVA-like outer quads (44 .5° and 50° beams) is proposed to minimize laser plasma interaction (LPI) losses and avoid problems with propagating the inner (23 .5° and 30°) beams. Symmetry and drive are controlled by shortening the hohlraum, using a smaller laser entrance hole (LEH), beam phasing the 44 .5° and 50° beams, and correcting the remaining P4 asymmetry with a capsule shim. Ensembles of time-resolved view factor simulations help narrow the design space of the new configuration, with fine tuning provided by the radiation-hydrodynamic code HYDRA. Prepared by LLNL under Contract DE-AC52-07NA27344.

Experimental demonstration of laser imprint reduction using underdense foams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Delorme, B.; Casner, A.; CELIA, University of Bordeaux-CNRS-CEA, F-33400 Talence

2016-04-15

Reducing the detrimental effect of the Rayleigh-Taylor (RT) instability on the target performance is a critical challenge. In this purpose, the use of targets coated with low density foams is a promising approach to reduce the laser imprint. This article presents results of ablative RT instability growth measurements, performed on the OMEGA laser facility in direct-drive for plastic foils coated with underdense foams. The laser beam smoothing is explained by the parametric instabilities developing in the foam and reducing the laser imprint on the plastic (CH) foil. The initial perturbation pre-imposed by the means of a specific phase plate wasmore » shown to be smoothed using different foam characteristics. Numerical simulations of the laser beam smoothing in the foam and of the RT growth are performed with a suite of paraxial electromagnetic and radiation hydrodynamic codes. They confirmed the foam smoothing effect in the experimental conditions.« less

longitudinal space charge assisted echo seeding of a free electron laser

NASA Astrophysics Data System (ADS)

Hacker, Kirsten

2015-05-01

Seed lasers are employed to improve the temporal coherence of free-electron laser light. However, when seed pulses are short relative to the particle bunch, the noisy, temporally incoherent radiation from the un-seeded electrons can overwhelm the coherent, seeded radiation. In this paper a new seeding mechanism to improve the contrast between coherent and incoherent free electron laser radiation is employed together with a novel, simplified echo-seeding method. The concept relies on a combination of longitudinal space charge wakes and an echo-seeding technique to make a short, coherent pulse of FEL light together with noise background suppression. Several different simulation codes are used to illustrate the concept with conditions at the soft x-ray Free-electron LASer in Hamburg, FLASH. The impacts of coherent synchrotron radiation, intra beam scattering, and high peak current operation are investigated.

Two-dimensional Maxwell-Bloch simulation of quasi-π-pulse amplification in a seeded XUV laser

NASA Astrophysics Data System (ADS)

Larroche, O.; Klisnick, A.

2013-09-01

The amplification of high-order-harmonics (HOH) seed pulses in a swept-gain XUV laser is investigated through numerical simulations of the full set of Bloch and two-dimensional paraxial propagation equations with our code colax. The needed atomic data are taken from a hydrodynamics and collisional-radiative simulation in the case of a Ni-like Ag plasma created from the interaction of an infrared laser with a solid target and pumped in the transient regime. We show that the interplay of strong population inversion and diffraction or refraction due to the short transverse dimensions and steep density gradient of the active plasma can lead to the amplification of an intense, ultrashort, quasi-“π” pulse triggered by the incoming seed. By properly tuning the system geometry and HOH pulse parameters, we show that an ≃10 fs, 8×1012 W/cm2 amplified pulse can be achieved in a 3-mm-long Ni-like Ag plasma, with a factor of ≳10 intensity contrast with respect to the longer-lasting wake radiation and amplified spontaneous emission.

Investigation of the hydrodynamics and emission of a laser heated tamped high-Z target

NASA Astrophysics Data System (ADS)

Gray, William J.; Foord, Mark E.; Schneider, Marilyn B.; Barrios, Maria A.; Brown, Greg V.; Heeter, Robert F.; Jarrott, L. Charlie; Liedahl, Duane A.; Marley, Ed V.; Mauche, Chris W.; Widmann, Klaus

2018-06-01

We investigate the hydrodynamic expansion and x-ray emission of a laser-heated buried-layer target. This work is motivated by our interest in developing an experimental platform for probing plasma properties under relatively uniform conditions, such as ionization and equation of state. Targets consist of a few thousand angstrom-thick layer of material, embedded in a few microns of the tamper material (typically beryllium), which are irradiated on both sides by an intense few-nanosecond laser pulse. The expansion and emission of our target, composed of a homogeneous mixture of iron, vanadium, and gold, are simulated using the 2-D LASNEX code. Reasonable agreement is found with the time history of the x-ray emission traces (DANTE). Both experiments and simulations exhibit an interesting reduction in the radial size of the emission region with time, as measured using face-on imaging. This is shown to be due to the ablation of the beryllium tamper, which affects the radial confinement of the embedded target. Simulations using a larger diameter beryllium tamper are found to mitigate this effect, improving the one-dimensionality of the expansion.

Particle-in-cell/accelerator code for space-charge dominated beam simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

2012-05-08

Warp is a multidimensional discrete-particle beam simulation program designed to be applicable where the beam space-charge is non-negligible or dominant. It is being developed in a collaboration among LLNL, LBNL and the University of Maryland. It was originally designed and optimized for heave ion fusion accelerator physics studies, but has received use in a broader range of applications, including for example laser wakefield accelerators, e-cloud studies in high enery accelerators, particle traps and other areas. At present it incorporates 3-D, axisymmetric (r,z) planar (x-z) and transverse slice (x,y) descriptions, with both electrostatic and electro-magnetic fields, and a beam envelope model.more » The code is guilt atop the Python interpreter language.« less

Laser direct marking applied to rasterizing miniature Data Matrix Code on aluminum alloy

NASA Astrophysics Data System (ADS)

Li, Xia-Shuang; He, Wei-Ping; Lei, Lei; Wang, Jian; Guo, Gai-Fang; Zhang, Teng-Yun; Yue, Ting

2016-03-01

Precise miniaturization of 2D Data Matrix (DM) Codes on Aluminum alloy formed by raster mode laser direct part marking is demonstrated. The characteristic edge over-burn effects, which render vector mode laser direct part marking inadequate for producing precise and readable miniature codes, are minimized with raster mode laser marking. To obtain the control mechanism for the contrast and print growth of miniature DM code by raster laser marking process, the temperature field model of long pulse laser interaction with material is established. From the experimental results, laser average power and Q frequency have an important effect on the contrast and print growth of miniature DM code, and the threshold of laser average power and Q frequency for an identifiable miniature DM code are respectively 3.6 W and 110 kHz, which matches the model well within normal operating conditions. In addition, the empirical model of correlation occurring between laser marking parameters and module size is also obtained, and the optimal processing parameter values for an identifiable miniature DM code of different but certain data size are given. It is also found that an increase of the repeat scanning number effectively improves the surface finish of bore, the appearance consistency of modules, which has benefit to reading. The reading quality of miniature DM code is greatly improved using ultrasonic cleaning in water by avoiding the interference of color speckles surrounding modules.

Surface 3D nanostructuring by tightly focused laser pulse: simulations by Lagrangian code and molecular dynamics

NASA Astrophysics Data System (ADS)

Inogamov, Nail A.; Zhakhovsky, Vasily V.

2016-02-01

There are many important applications in which the ultrashort diffraction-limited and therefore tightly focused laser pulses irradiates metal films mounted on dielectric substrate. Here we present the detailed picture of laser peeling and 3D structure formation of the thin (relative to a depth of a heat affected zone in the bulk targets) gold films on glass substrate. The underlying physics of such diffraction-limited laser peeling was not well understood previously. Our approach is based on a physical model which takes into consideration the new calculations of the two-temperature (2T) equation of state (2T EoS) and the two-temperature transport coefficients together with the coupling parameter between electron and ion subsystems. The usage of the 2T EoS and the kinetic coefficients is required because absorption of an ultrashort pulse with duration of 10-1000 fs excites electron subsystem of metal and transfers substance into the 2T state with hot electrons (typical electron temperatures 1-3 eV) and much colder ions. It is shown that formation of submicrometer-sized 3D structures is a result of the electron-ion energy transfer, melting, and delamination of film from substrate under combined action of electron and ion pressures, capillary deceleration of the delaminated liquid metal or semiconductor, and ultrafast freezing of molten material. We found that the freezing is going in non-equilibrium regime with strongly overcooled liquid phase. In this case the Stefan approximation is non-applicable because the solidification front speed is limited by the diffusion rate of atoms in the molten material. To solve the problem we have developed the 2T Lagrangian code including all this reach physics in. We also used the high-performance combined Monte- Carlo and molecular dynamics code for simulation of surface 3D nanostructuring at later times after completion of electron-ion relaxation.

Sheath field dynamics from time-dependent acceleration of laser-generated positrons

NASA Astrophysics Data System (ADS)

Kerr, Shaun; Fedosejevs, Robert; Link, Anthony; Williams, Jackson; Park, Jaebum; Chen, Hui

2017-10-01

Positrons produced in ultraintense laser-matter interactions are accelerated by the sheath fields established by fast electrons, typically resulting in quasi-monoenergetic beams. Experimental results from OMEGA EP show higher order features developing in the positron spectra when the laser energy exceeds one kilojoule. 2D PIC simulations using the LSP code were performed to give insight into these spectral features. They suggest that for high laser energies multiple, distinct phases of acceleration can occur due to time-dependent sheath field acceleration. The detailed dynamics of positron acceleration will be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344, and funded by LDRD 17-ERD-010.

Laser-Plasma Interaction Experiments at Direct-Drive Ignition-Relevant Plasma Conditions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Solodov, A. A.; Rosenberg, M. J.; Myatt, J. F.; Shaw, J. G.; Seka, W.; Epstein, R.; Short, R. W.; Follett, R. K.; Regan, S. P.; Froula, D. H.; Radha, P. B.; Michel, P.; Chapman, T.; Hohenberger, M.

2017-10-01

Laser-plasma interaction (LPI) instabilities, such as stimulated Raman scattering (SRS) and two-plasmon decay, can be detrimental for direct-drive inertial confinement fusion because of target preheat by the high-energy electrons they generate. The radiation-hydrodynamic code DRACO was used to design planar-target experiments at the National Ignition Facility that generated plasma and interaction conditions relevant to ignition direct-drive designs (IL 1015W/cm2 , Te > 3 keV, density gradient scale lengths of Ln 600 μm). Laser-energy conversion efficiency to hot electrons of 0.5% to 2.5% with temperature of 45 to 60 keV was inferred from the experiment when the laser intensity at the quarter-critical surface increased from 6 to 15 ×1014W/cm2 . LPI was dominated by SRS, as indicated by the measured scattered-light spectra. Simulations of SRS using the LPI code LPSE have been performed and compared with predictions of theoretical models. Implications for ignition-scale direct-drive experiments will be discussed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Reconstruction of Axial Energy Deposition in Magnetic Liner Inertial Fusion Based on PECOS Shadowgraph Unfolds Using the AMR Code FLASH

NASA Astrophysics Data System (ADS)

Adams, Marissa; Jennings, Christopher; Slutz, Stephen; Peterson, Kyle; Gourdain, Pierre; U. Rochester-Sandia Collaboration

2017-10-01

Magnetic Liner Inertial Fusion (MagLIF) experiments incorporate a laser to preheat a deuterium filled capsule before compression via a magnetically imploding liner. In this work, we focus on the blast wave formed in the fuel during the laser preheat component of MagLIF, where approximately 1kJ of energy is deposited in 3ns into the capsule axially before implosion. To model blast waves directly relevant to experiments such as MagLIF, we inferred deposited energy from shadowgraphy of laser-only experiments preformed at the PECOS target chamber using the Z-Beamlet laser. These energy profiles were used to initialize 2-dimensional simulations using by the adaptive mesh refinement code FLASH. Gradients or asymmetries in the energy deposition may seed instabilities that alter the fuel's distribution, or promote mix, as the blast wave interacts with the liner wall. The AMR capabilities of FLASH allow us to study the development and dynamics of these instabilities within the fuel and their effect on the liner before implosion. Sandia Natl Labs is managed by NTES of Sandia, LLC., a subsidiary of Honeywell International, Inc, for the U.S. DOEs NNSA under contract DE-NA0003525.

Computational modeling of stress transient and bubble evolution in short-pulse laser irradiated melanosome particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strauss, M.; Amendt, P.A.; London, R.A.

1997-03-04

Objective is to study retinal injury by subnanosecond laser pulses absorbed in the retinal pigment epithelium (RPE) cells. The absorption centers in the RPE cell are melanosomes of order 1 {mu}m radius. Each melanosome includes many melanin particles of 10-15 nm radius, which are the local absorbers of the laser light and generate a discrete structure of hot spots. This work use the hydrodynamic code LATIS (LAser-TISsue interaction modeling) and a water equation of state to first simulate the small melanin particle of 15 nm responsible for initiating the hot spot and the pressure field. A average melanosome of 1more » {mu}m scale is next simulated. Supersonic shocks and fast vapor bubbles are generated in both cases: the melanin scale and the melanosome scale. The hot spot induces a shock wave pressure than with a uniform deposition of laser energy. It is found that an absorption coefficient of 6000 -8000 cm{sup -1} can explain the enhanced shock wave emitted by the melanosome. An experimental and theoretical effort should be considered to identify the mechanism for generating shock wave enhancement.« less

Modeling Hohlraum-Based Laser Plasma Instability Experiments

NASA Astrophysics Data System (ADS)

Meezan, N. B.

2005-10-01

Laser fusion targets must control laser-plasma instabilities (LPI) in order to perform as designed. We present analyses of recent hohlraum LPI experiments from the Omega laser facility. The targets, gold hohlraums filled with gas or SiO2 foam, are preheated by several 3φ beams before an interaction beam (2φ or 3φ) is fired along the hohlraum axis. The experiments are simulated in 2-D and 3-D using the code hydra. The choice of electron thermal conduction model in hydra strongly affects the simulated plasma conditions. This work is part of a larger effort to systematically explore the usefulness of linear gain as a design tool for fusion targets. We find that the measured Raman and Brillouin backscatter scale monotonically with the peak linear gain calculated for the target; however, linear gain is not sufficient to explain all trends in the data. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.

Heating, Hydrodynamics, and Radiation From a Laser Heated Non-LTE High-Z Target

NASA Astrophysics Data System (ADS)

Gray, William; Foord, M. E.; Schneider, M. B.; Barrios, M. A.; Brown, G. V.; Heeter, R. F.; Jarrott, L. C.; Liedahl, D. A.; Marley, E. V.; Mauche, C. W.; Widmann, K.

2016-10-01

We present 2D R-z simulations that model the hydrodynamics and x-ray output of a laser heated, tamped foil, using the rad-hydro code LASNEX. The foil consists of a thin (2400 A) cylindrical disk of iron/vanadium/gold that is embedded in a thicker Be tamper. The simulations utilize a non-LTE detailed configuration (DCA) model, which generates the emission spectra. Simulated pinhole images are compared with data, finding qualitative agreement with the time-history of the face-on emission profiles, and exhibiting an interesting reduction in emission size over a few ns time period. Furthermore, we find that the simulations recover similar burn through times in both the target and Be tamper as measured by a time-dependent filtered x-ray detector (DANTE). Additional results and characterization of the experimental plasma will be presented. This work performed under the auspices of U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Extreme Physics

NASA Astrophysics Data System (ADS)

Colvin, Jeff; Larsen, Jon

2013-11-01

Acknowledgements; 1. Extreme environments: what, where, how; 2. Properties of dense and classical plasmas; 3. Laser energy absorption in matter; 4. Hydrodynamic motion; 5. Shocks; 6. Equation of state; 7. Ionization; 8. Thermal energy transport; 9. Radiation energy transport; 10. Magnetohydrodynamics; 11. Considerations for constructing radiation-hydrodynamics computer codes; 12. Numerical simulations; Appendix: units and constants, glossary of symbols; References; Bibliography; Index.

Simulations of radiation pressure ion acceleration with the VEGA Petawatt laser

NASA Astrophysics Data System (ADS)

Stockhausen, Luca C.; Torres, Ricardo; Conejero Jarque, Enrique

2016-09-01

The Spanish Pulsed Laser Centre (CLPU) is a new high-power laser facility for users. Its main system, VEGA, is a CPA Ti:Sapphire laser which, in its final phase, will be able to reach Petawatt peak powers in pulses of 30 fs with a pulse contrast of 1 :1010 at 1 ps. The extremely low level of pre-pulse intensity makes this system ideally suited for studying the laser interaction with ultrathin targets. We have used the particle-in-cell (PIC) code OSIRIS to carry out 2D simulations of the acceleration of ions from ultrathin solid targets under the unique conditions provided by VEGA, with laser intensities up to 1022 W cm-2 impinging normally on 20 - 60 nm thick overdense plasmas, with different polarizations and pre-plasma scale lengths. We show how signatures of the radiation pressure-dominated regime, such as layer compression and bunch formation, are only present with circular polarization. By passively shaping the density gradient of the plasma, we demonstrate an enhancement in peak energy up to tens of MeV and monoenergetic features. On the contrary linear polarization at the same intensity level causes the target to blow up, resulting in much lower energies and broader spectra. One limiting factor of Radiation Pressure Acceleration is the development of Rayleigh-Taylor like instabilities at the interface of the plasma and photon fluid. This results in the formation of bubbles in the spatial profile of laser-accelerated proton beams. These structures were previously evidenced both experimentally and theoretically. We have performed 2D simulations to characterize this bubble-like structure and report on the dependency on laser and target parameters.

Simulations of ion acceleration from ultrathin targets with the VEGA petawatt laser

NASA Astrophysics Data System (ADS)

Stockhausen, Luca C.; Torres, Ricardo; Conejero Jarque, Enrique

2015-05-01

The Spanish Pulsed Laser Centre (CLPU) is a new high-power laser facility for users. Its main system, VEGA, is a CPA Ti:Sapphire laser which, in its final phase, will be able to reach petawatt peak powers in pulses of 30 fs with a pulse contrast of 1 : 1010 at 1 ps. The extremely low level of pre-pulse intensity makes this system ideally suited for studying the laser interaction with ultrathin targets. We have used the particle-in-cell (PIC) code OSIRIS to carry out 2D simulations of the acceleration of ions from ultrathin solid targets under the unique conditions provided by VEGA, with laser intensities up to 1022Wcm-2 impinging normally on 5 - 40 nm thick overdense plasmas, with different polarizations and pre-plasma scale lengths. We show how signatures of the radiation pressure dominated regime, such as layer compression and bunch formation, are only present with circular polarization. By passively shaping the density gradient of the plasma, we demonstrate an enhancement in peak energy up to tens of MeV and monoenergetic features. On the contrary linear polarization at the same intensity level causes the target to blow up, resulting in much lower energies and broader spectra. One limiting factor of Radiation Pressure Acceleration is the development of Rayleigh-Taylor like instabilities at the interface of the plasma and photon fluid. This results in the formation of bubbles in the spatial profile of laser-accelerated proton beams. These structures were previously evidenced both experimentally and theoretically. We have performed 2D simulations to characterize this bubble-like structure and report on the dependency on laser and target parameters.

Threshold for electron self-injection in a nonlinear laser-plasma accelerator

NASA Astrophysics Data System (ADS)

Benedetti, Carlo; Schroeder, Carl; Esarey, Eric; Leemans, Wim

2012-10-01

The process of electron self-injection in the nonlinear bubble-wake generated by a short and intense laser pulse propagating in an uniform underdense plasma is investigated. A detailed analysis of particle orbit in the wakefield is performed by using reduced analytical models and numerical simulations carried out with the 2D cylindrical, envelope, ponderomotive, hybrid PIC/fluid code INF&RNO. In particular, we consider a wake generated by a frozen (non-evolving) laser driver traveling with a prescribed velocity, which then sets the properties of the wake, so the injection dynamics is decoupled from driver evolution but a realistic structure for the wakefield is retained. We investigate the dependence of the injection threshold on laser intensity, plasma temperature and wake velocity for a range of parameters of interest for current and future laser plasma accelerators. The phase-space properties of the injected particle bunch will also be discussed.

Two-Plasmon Decay Mitigation in Direct-Drive Inertial-Confinement-Fusion Experiments Using Multilayer Targets.

PubMed

Follett, R K; Delettrez, J A; Edgell, D H; Goncharov, V N; Henchen, R J; Katz, J; Michel, D T; Myatt, J F; Shaw, J; Solodov, A A; Stoeckl, C; Yaakobi, B; Froula, D H

2016-04-15

Multilayer direct-drive inertial-confinement-fusion targets are shown to significantly reduce two-plasmon decay (TPD) driven hot-electron production while maintaining high hydrodynamic efficiency. Implosion experiments on the OMEGA laser used targets with silicon layered between an inner beryllium and outer silicon-doped plastic ablator. A factor-of-5 reduction in hot-electron generation (>50  keV) was observed in the multilayer targets relative to pure CH targets. Three-dimensional simulations of the TPD-driven hot-electron production using a laser-plasma interaction code (lpse) that includes nonlinear and kinetic effects show good agreement with the measurements. The simulations suggest that the reduction in hot-electron production observed in the multilayer targets is primarily caused by increased electron-ion collisional damping.

Simulations of a FIR Oscillator with Large Slippage parameter at Jefferson Lab for FIR/UV pump-probe experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benson, Stephen V.; Campbell, L. T.; McNeil, B.W.T.

We previously proposed a dual FEL configuration on the UV Demo FEL at Jefferson Lab that would allow simultaneous lasing at FIR and UV wavelengths. The FIR source would be an FEL oscillator with a short wiggler providing diffraction-limited pulses with pulse energy exceeding 50 microJoules, using the exhaust beam from a UVFEL as the input electron beam. Since the UV FEL requires very short pulses, the input to the FIR FEL is extremely short compared to a slippage length and the usual Slowly Varying Envelope Approximation (SVEA) does not apply. We use a non-SVEA code to simulate this systemmore » both with a small energy spread (UV laser off) and with large energy spread (UV laser on).« less

Simulation Studies of the X-Ray Free-Electron Laser Oscillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindberg, R. R.; Shyd'ko, Y.; Kim, K.-J

Simulations of the x-ray free-electron laser (FEL) oscillator are presented that include transverse effects and realistic Bragg crystal properties with the two-dimensional code GINGER. In the present cases considered the radiation divergence is much narrower than the crystal acceptance, and the numerical algorithm can be simplified by ignoring the finite angular bandwidth of the crystal. In this regime GINGER shows that the saturated x-ray pulses have 109 photons and are nearly Fourier-limited with peak powers in excess of 1 MW. Wealso include preliminary results for a four-mirror cavity that can be tuned in wavelength over a few percent, with futuremore » plans to incorporate the full transverse response of the Bragg crystals into GINGER to more accurately model this tunable source.« less

Simulations of tungsten, tungsten-coated and tungsten-doped targets at low KrF laser intensities

NASA Astrophysics Data System (ADS)

Colombant, D.; Klapisch, M.; Lehecka, T.; Seely, J.; Schmitt, A.; Obenschain, S.

1998-11-01

High-Z coatings can be used to create X-rays to preheat the ablator, thus reducing the laser imprint and the R-T instability. Targets with tungsten coated on the surface or mixed with CH have recently been irradiated using Nike at intensities of a few 10^12W/cm^2, typical of the foot of a laser fusion pulse. The present simulations in 1D have been carried out to provide an interpretation of these experiments and to validate the code for radiation-preheated target designs(S. E. Bodner et al., Phys. Plasmas, 5, 1901 (1998).). All computations were performed in non-LTE(M. Busquet, Phys. Fluids B, 5, 4191 (1993); M. Klapisch, A. Bar-Shalom, J. Oreg and D. Colombant, Phys. Plasmas, 5, 1919 (1998).). Low resolution X-ray spectra obtained from on-line computations are compared to time-integrated experimental spectra between 100 eV and 500 eV. Agreements and differences between computations and experiments will be discussed.

Modeling of laser transmission contour welding process using FEA and DoE

NASA Astrophysics Data System (ADS)

Acherjee, Bappa; Kuar, Arunanshu S.; Mitra, Souren; Misra, Dipten

2012-07-01

In this research, a systematic investigation on laser transmission contour welding process is carried out using finite element analysis (FEA) and design of experiments (DoE) techniques. First of all, a three-dimensional thermal model is developed to simulate the laser transmission contour welding process with a moving heat source. The commercial finite element code ANSYS® multi-physics is used to obtain the numerical results by implementing a volumetric Gaussian heat source, and combined convection-radiation boundary conditions. Design of experiments together with regression analysis is then employed to plan the experiments and to develop mathematical models based on simulation results. Four key process parameters, namely power, welding speed, beam diameter, and carbon black content in absorbing polymer, are considered as independent variables, while maximum temperature at weld interface, weld width, and weld depths in transparent and absorbing polymers are considered as dependent variables. Sensitivity analysis is performed to determine how different values of an independent variable affect a particular dependent variable.

Three-Dimensional Simulations of Flat-Foil Laser-Imprint Experiments at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Shvydky, A.; Radha, P. B.; Rosenberg, M. J.; Anderson, K. S.; Goncharov, V. N.; Marozas, J. A.; Marshall, F. J.; McKenty, P. W.; Regan, S. P.; Sangster, T. C.; Hohenberger, M.; di Nicola, J. M.; Koning, J. M.; Marinak, M. M.; Masse, L.; Karasik, M.

2017-10-01

Control of shell nonuniformities imprinted by the laser and amplified by hydrodynamic instabilities in the imploding target is critical for the success of direct-drive ignition at the National Ignition Facility (NIF). To measure a level of imprint and its reduction by the NIF smoothing by spectral dispersion (SSD), we performed experiments that employed flat CH foils driven with a single NIF beam with either no SSD or the NIF indirect-drive SSD applied to the laser pulse. Face-on x-ray radiography was used to measure optical depth variations, from which the amplitudes of the foil areal-density modulations were obtained. Results of 3-D, radiation-hydrodynamic code HYDRA simulations of the growth of the imprint-seeded perturbations are presented and compared with the experimental data. This work was supported by the U.S. Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract Number DE-AC52-07NA27344.

A hybrid model of laser energy deposition for multi-dimensional simulations of plasmas and metals

NASA Astrophysics Data System (ADS)

Basko, Mikhail M.; Tsygvintsev, Ilia P.

2017-05-01

The hybrid model of laser energy deposition is a combination of the geometrical-optics ray-tracing method with the one-dimensional (1D) solution of the Helmholtz wave equation in regions where the geometrical optics becomes inapplicable. We propose an improved version of this model, where a new physically consistent criterion for transition to the 1D wave optics is derived, and a special rescaling procedure of the wave-optics deposition profile is introduced. The model is intended for applications in large-scale two- and three-dimensional hydrodynamic codes. Comparison with exact 1D solutions demonstrates that it can fairly accurately reproduce the absorption fraction in both the s- and p-polarizations on arbitrarily steep density gradients, provided that a sufficiently accurate algorithm for gradient evaluation is used. The accuracy of the model becomes questionable for long laser pulses simulated on too fine grids, where the hydrodynamic self-focusing instability strongly manifests itself.

Laser generated Ge ions accelerated by additional electrostatic field for implantation technology

NASA Astrophysics Data System (ADS)

Rosinski, M.; Gasior, P.; Fazio, E.; Ando, L.; Giuffrida, L.; Torrisi, L.; Parys, P.; Mezzasalma, A. M.; Wolowski, J.

2013-05-01

The paper presents research on the optimization of the laser ion implantation method with electrostatic acceleration/deflection including numerical simulations by the means of the Opera 3D code and experimental tests at the IPPLM, Warsaw. To introduce the ablation process an Nd:YAG laser system with repetition rate of 10 Hz, pulse duration of 3.5 ns and pulse energy of 0.5 J has been applied. Ion time of flight diagnostics has been used in situ to characterize concentration and energy distribution in the obtained ion streams while the postmortem analysis of the implanted samples was conducted by the means of XRD, FTIR and Raman Spectroscopy. In the paper the predictions of the Opera 3D code are compared with the results of the ion diagnostics in the real experiment. To give the whole picture of the method, the postmortem results of the XRD, FTIR and Raman characterization techniques are discussed. Experimental results show that it is possible to achieve the development of a micrometer-sized crystalline Ge phase and/or an amorphous one only after a thermal annealing treatment.

Experimental validation of thermodynamic mixture rules at extreme pressures and densities

NASA Astrophysics Data System (ADS)

Bradley, P. A.; Loomis, E. N.; Merritt, E. C.; Guzik, J. A.; Denne, P. H.; Clark, T. T.

2018-01-01

Accurate modeling of a mixed material Equation of State (EOS) at high pressures (˜1 to 100 Mbar) is critical for simulating inertial confinement fusion and high energy density systems. This paper presents a comparison of two mixing rule models to the experiment to assess their applicability in this regime. The shock velocities of polystyrene, aluminum, and nickel aluminide (NiAl) were measured at a shock pressure of ˜3 TPa (˜30 Mbar) on the Omega EP laser facility (Laboratory for Laser Energetics, University of Rochester, New York). The resultant shock velocities were compared to those derived from the RAGE (Eulerian) hydrodynamics code to validate various mixing rules used to construct an EOS for NiAl. The simulated shock transit time through the sample (Al or NiAl) matched the measurements to within the ±45ps measurement uncertainty. The law of partial volume (Amagat) and the law of partial pressure (Dalton) mixture rules provided equally good matches to the NiAl shock data. Other studies showed that the Amagat mixing rule is superior, and we recommend it since our results also show a satisfactory match. The comparable quality of the simulation to data for the Al and NiAl samples implies that a mixture rule can supply an EOS for plasma mixtures with adequate fidelity for simulations where mixing takes place, such as advective mix in an Eulerian code or when two materials are mixed together via diffusion, turbulence, or other physical processes.

Experimental validation of thermodynamic mixture rules at extreme pressures and densities

DOE PAGES

Bradley, Paul Andrew; Loomis, Eric Nicholas; Merritt, Elizabeth Catherine; ...

2018-01-19

Accurate modeling of a mixed material Equation of State (EOS) at high pressures (~1 to 100 Mbar) is critical for simulating inertial confinement fusion and high energy density systems. Here, this paper presents a comparison of two mixing rule models to the experiment to assess their applicability in this regime. The shock velocities of polystyrene, aluminum, and nickel aluminide (NiAl) were measured at a shock pressure of ~3 TPa (~30 Mbar) on the Omega EP laser facility (Laboratory for Laser Energetics, University of Rochester, New York). The resultant shock velocities were compared to those derived from the RAGE (Eulerian) hydrodynamicsmore » code to validate various mixing rules used to construct an EOS for NiAl. The simulated shock transit time through the sample (Al or NiAl) matched the measurements to within the ±45ps measurement uncertainty. The law of partial volume (Amagat) and the law of partial pressure (Dalton) mixture rules provided equally good matches to the NiAl shock data. Other studies showed that the Amagat mixing rule is superior, and we recommend it since our results also show a satisfactory match. In conclusion, the comparable quality of the simulation to data for the Al and NiAl samples implies that a mixture rule can supply an EOS for plasma mixtures with adequate fidelity for simulations where mixing takes place, such as advective mix in an Eulerian code or when two materials are mixed together via diffusion, turbulence, or other physical processes.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradley, Paul Andrew; Loomis, Eric Nicholas; Merritt, Elizabeth Catherine

Accurate modeling of a mixed material Equation of State (EOS) at high pressures (~1 to 100 Mbar) is critical for simulating inertial confinement fusion and high energy density systems. Here, this paper presents a comparison of two mixing rule models to the experiment to assess their applicability in this regime. The shock velocities of polystyrene, aluminum, and nickel aluminide (NiAl) were measured at a shock pressure of ~3 TPa (~30 Mbar) on the Omega EP laser facility (Laboratory for Laser Energetics, University of Rochester, New York). The resultant shock velocities were compared to those derived from the RAGE (Eulerian) hydrodynamicsmore » code to validate various mixing rules used to construct an EOS for NiAl. The simulated shock transit time through the sample (Al or NiAl) matched the measurements to within the ±45ps measurement uncertainty. The law of partial volume (Amagat) and the law of partial pressure (Dalton) mixture rules provided equally good matches to the NiAl shock data. Other studies showed that the Amagat mixing rule is superior, and we recommend it since our results also show a satisfactory match. In conclusion, the comparable quality of the simulation to data for the Al and NiAl samples implies that a mixture rule can supply an EOS for plasma mixtures with adequate fidelity for simulations where mixing takes place, such as advective mix in an Eulerian code or when two materials are mixed together via diffusion, turbulence, or other physical processes.« less

Electro-Thermal-Mechanical Simulation Capability Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, D

This is the Final Report for LDRD 04-ERD-086, 'Electro-Thermal-Mechanical Simulation Capability'. The accomplishments are well documented in five peer-reviewed publications and six conference presentations and hence will not be detailed here. The purpose of this LDRD was to research and develop numerical algorithms for three-dimensional (3D) Electro-Thermal-Mechanical simulations. LLNL has long been a world leader in the area of computational mechanics, and recently several mechanics codes have become 'multiphysics' codes with the addition of fluid dynamics, heat transfer, and chemistry. However, these multiphysics codes do not incorporate the electromagnetics that is required for a coupled Electro-Thermal-Mechanical (ETM) simulation. There aremore » numerous applications for an ETM simulation capability, such as explosively-driven magnetic flux compressors, electromagnetic launchers, inductive heating and mixing of metals, and MEMS. A robust ETM simulation capability will enable LLNL physicists and engineers to better support current DOE programs, and will prepare LLNL for some very exciting long-term DoD opportunities. We define a coupled Electro-Thermal-Mechanical (ETM) simulation as a simulation that solves, in a self-consistent manner, the equations of electromagnetics (primarily statics and diffusion), heat transfer (primarily conduction), and non-linear mechanics (elastic-plastic deformation, and contact with friction). There is no existing parallel 3D code for simulating ETM systems at LLNL or elsewhere. While there are numerous magnetohydrodynamic codes, these codes are designed for astrophysics, magnetic fusion energy, laser-plasma interaction, etc. and do not attempt to accurately model electromagnetically driven solid mechanics. This project responds to the Engineering R&D Focus Areas of Simulation and Energy Manipulation, and addresses the specific problem of Electro-Thermal-Mechanical simulation for design and analysis of energy manipulation systems such as magnetic flux compression generators and railguns. This project compliments ongoing DNT projects that have an experimental emphasis. Our research efforts have been encapsulated in the Diablo and ALE3D simulation codes. This new ETM capability already has both internal and external users, and has spawned additional research in plasma railgun technology. By developing this capability Engineering has become a world-leader in ETM design, analysis, and simulation. This research has positioned LLNL to be able to compete for new business opportunities with the DoD in the area of railgun design. We currently have a three-year $1.5M project with the Office of Naval Research to apply our ETM simulation capability to railgun bore life issues and we expect to be a key player in the railgun community.« less

Al 1s-2p absorption spectroscopy of shock-wave heating and compression in laser-driven planar foil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawada, H.; Regan, S. P.; Radha, P. B.

Time-resolved Al 1s-2p absorption spectroscopy is used to diagnose direct-drive, shock-wave heating and compression of planar targets having nearly Fermi-degenerate plasma conditions (T{sub e}{approx}10-40 eV, {rho}{approx}3-11 g/cm{sup 3}) on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. A planar plastic foil with a buried Al tracer layer was irradiated with peak intensities of 10{sup 14}-10{sup 15} W/cm{sup 2} and probed with the pseudocontinuum M-band emission from a point-source Sm backlighter in the range of 1.4-1.7 keV. The laser ablation process launches 10-70 Mbar shock waves into the CH/Al/CH target. The Al 1s-2p absorption spectramore » were analyzed using the atomic physic code PRISMSPECT to infer T{sub e} and {rho} in the Al layer, assuming uniform plasma conditions during shock-wave heating, and to determine when the heat front penetrated the Al layer. The drive foils were simulated with the one-dimensional hydrodynamics code LILAC using a flux-limited (f=0.06 and f=0.1) and nonlocal thermal-transport model [V. N. Goncharov et al., Phys. Plasmas 13, 012702 (2006)]. The predictions of simulated shock-wave heating and the timing of heat-front penetration are compared to the observations. The experimental results for a wide variety of laser-drive conditions and buried depths have shown that the LILAC predictions using f=0.06 and the nonlocal model accurately model the shock-wave heating and timing of the heat-front penetration while the shock is transiting the target. The observed discrepancy between the measured and simulated shock-wave heating at late times of the drive can be explained by the reduced radiative heating due to lateral heat flow in the corona.« less

Al 1s-2p Absorption Spectroscopy of Shock-Wave Heating and Compression in Laser-Driven Planar Foil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawada, H.; Regan, S.P.; Radha, P.B.

Time-resolved Al 1s-2p absorption spectroscopy is used to diagnose direct-drive, shock-wave heating and compression of planar targets having nearly Fermi-degenerate plasma conditions (Te ~ 10–40 eV, rho ~ 3–11 g/cm^3) on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. A planar plastic foil with a buried Al tracer layer was irradiated with peak intensities of 10^14–10^15 W/cm^2 and probed with the pseudocontinuum M-band emission from a point-source Sm backlighter in the range of 1.4–1.7 keV. The laser ablation process launches 10–70 Mbar shock waves into the CH/Al/CH target. The Al 1s-2p absorption spectra weremore » analyzed using the atomic physic code PRISMSPECT to infer Te and rho in the Al layer, assuming uniform plasma conditions during shock-wave heating, and to determine when the heat front penetrated the Al layer. The drive foils were simulated with the one-dimensional hydrodynamics code LILAC using a flux-limited (f =0.06 and f =0.1) and nonlocal thermal-transport model [V. N. Goncharov et al., Phys. Plasmas 13, 012702 (2006)]. The predictions of simulated shock-wave heating and the timing of heat-front penetration are compared to the observations. The experimental results for a wide variety of laser-drive conditions and buried depths have shown that the LILAC predictions using f = 0.06 and the nonlocal model accurately model the shock-wave heating and timing of the heat-front penetration while the shock is transiting the target. The observed discrepancy between the measured and simulated shock-wave heating at late times of the drive can be explained by the reduced radiative heating due to lateral heat flow in the corona.« less

LLE review. Quarterly report, January 1994--March 1994, Volume 58

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simon, A.

1994-07-01

This volume of the LLE Review, covering the period Jan - Mar 1994, contains articles on backlighting diagnostics; the effect of electron collisions on ion-acoustic waves and heat flow; using PIC code simulations for analysis of ultrashort laser pulses interacting with solid targets; creating a new instrument for characterizing thick cryogenic layers; and a description of a large-aperture ring amplifier for laser-fusion drivers. Three of these articles - backlighting diagnostics; characterizing thick cryogenic layers; and large-aperture ring amplifier - are directly related to the OMEGA Upgrade, now under construction. Separate abstracts have been prepared for articles from this report.

Near-field phase-change recording using a GaN laser diode

NASA Astrophysics Data System (ADS)

Kishima, Koichiro; Ichimura, Isao; Yamamoto, Kenji; Osato, Kiyoshi; Kuroda, Yuji; Iida, Atsushi; Saito, Kimihiro

2000-09-01

We developed a 1.5-Numerical-Aperture optical setup using a GaN blue-violet laser diode. We used a 1.0 mm-diameter super-hemispherical solid immersion lens, and optimized a phase-change disk structure including the cover layer by the method of MTF simulation. The disk surface was polished by tape burnishing technique. An eye-pattern of (1-7)-coded data at the linear density of 80 nm/bit was demonstrated on the phase-change disk below a 50 nm gap height, which was realized through our air-gap servo mechanism.

Laser-plasma interactions with a Fourier-Bessel particle-in-cell method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andriyash, Igor A., E-mail: igor.andriyash@gmail.com; LOA, ENSTA ParisTech, CNRS, Ecole polytechnique, Université Paris-Saclay, 828 bd des Maréchaux, 91762 Palaiseau cedex; Lehe, Remi

A new spectral particle-in-cell (PIC) method for plasma modeling is presented and discussed. In the proposed scheme, the Fourier-Bessel transform is used to translate the Maxwell equations to the quasi-cylindrical spectral domain. In this domain, the equations are solved analytically in time, and the spatial derivatives are approximated with high accuracy. In contrast to the finite-difference time domain (FDTD) methods, that are used commonly in PIC, the developed method does not produce numerical dispersion and does not involve grid staggering for the electric and magnetic fields. These features are especially valuable in modeling the wakefield acceleration of particles in plasmas.more » The proposed algorithm is implemented in the code PLARES-PIC, and the test simulations of laser plasma interactions are compared to the ones done with the quasi-cylindrical FDTD PIC code CALDER-CIRC.« less

Improvement of signal to noise ratio of time domain mutliplexing fiber Bragg grating sensor network with Golay complementary codes

NASA Astrophysics Data System (ADS)

Elgaud, M. M.; Zan, M. S. D.; Abushagur, A. G.; Bakar, A. Ashrif A.

2017-07-01

This paper reports the employment of autocorrelation properties of Golay complementary codes (GCC) to enhance the performance of the time domain multiplexing fiber Bragg grating (TDM-FBG) sensing network. By encoding the light from laser with a stream of non-return-to-zero (NRZ) form of GCC and launching it into the sensing area that consists of the FBG sensors, we have found that the FBG signals can be decoded correctly with the autocorrelation calculations, confirming the successful demonstration of coded TDM-FBG sensor network. OptiGrating and OptiSystem simulators were used to design customized FBG sensors and perform the coded TDM-FBG sensor simulations, respectively. Results have substantiated the theoretical dependence of SNR enhancement on the code length of GCC, where the maximum SNR improvement of about 9 dB is achievable with the use of 256 bits of GCC compared to that of 4 bits case. Furthermore, the GCC has also extended the strain exposure up to 30% higher compared to the maximum of the conventional single pulse case. The employment of GCC in the TDM-FBG sensor system provides overall performance enhancement over the conventional single pulse case, under the same conditions.

Numerical modeling of pulsed laser-material interaction and of laser plume dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Qiang; Shi, Yina

2015-03-10

We have developed two-dimensional Arbitrary Lagrangian Eulerian (ALE) code which is used to study the physical processes, the plasma absorption, the crater profile, and the temperature distribution on metallic target and below the surface. The ALE method overcomes problems with Lagrangian moving mesh distortion by mesh smoothing and conservative quantities remapping from Lagrangian mesh to smoothed one. A new second order accurate diffusion solver has been implemented for the thermal conduction and radiation transport on distorted mesh. The results of numerical simulation of pulsed laser ablation are presented. The influences of different processes, such as time evolution of the surfacemore » temperature, interspecies interactions (elastic collisions, recombination-dissociation reaction), interaction with an ambient gas are examined. The study presents particular interest for the analysis of experimental results obtained during pulsed laser ablation.« less

Flash Kα radiography of laser-driven solid sphere compression for fast ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawada, H.; Lee, S.; Shiroto, T.

2016-06-20

Time-resolved compression of a laser-driven solid deuterated plastic sphere with a cone was measured with flash Kα x-ray radiography. A spherically converging shockwave launched by nanosecond GEKKO XII beams was used for compression while a flash of 4.51 keV Ti Kα x-ray backlighter was produced by a high-intensity, picosecond laser LFEX (Laser for Fast ignition EXperiment) near peak compression for radiography. Areal densities of the compressed core were inferred from two-dimensional backlit x-ray images recorded with a narrow-band spherical crystal imager. The maximum areal density in the experiment was estimated to be 87 ± 26 mg/cm 2. Lastly, the temporalmore » evolution of the experimental and simulated areal densities with a 2-D radiation-hydrodynamics code is in good agreement.« less

Flash Kα radiography of laser-driven solid sphere compression for fast ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sawada, H.; Lee, S.; Nagatomo, H.

2016-06-20

Time-resolved compression of a laser-driven solid deuterated plastic sphere with a cone was measured with flash Kα x-ray radiography. A spherically converging shockwave launched by nanosecond GEKKO XII beams was used for compression while a flash of 4.51 keV Ti Kα x-ray backlighter was produced by a high-intensity, picosecond laser LFEX (Laser for Fast ignition EXperiment) near peak compression for radiography. Areal densities of the compressed core were inferred from two-dimensional backlit x-ray images recorded with a narrow-band spherical crystal imager. The maximum areal density in the experiment was estimated to be 87 ± 26 mg/cm{sup 2}. The temporal evolution of the experimental andmore » simulated areal densities with a 2-D radiation-hydrodynamics code is in good agreement.« less

Bunch modulation in LWFA blowout regime

NASA Astrophysics Data System (ADS)

Vyskočil, Jiří; Klimo, Ondřej; Vieira, Jorge; Korn, Georg

2015-05-01

Laser wakefield acceleration (LWFA) is able to produce high quality electron bunches interesting for many applications ranging from coherent light sources to high energy physics. The blow-out regime of LWFA provides excellent accelerating structure able to maintain small transverse emittance and energy spread of the accelerating electron beam if combined with localised injection. A modulation of the back of a self-injected electron bunch in the blowout regime of Laser Wakefield Acceleration appears 3D Particle-in-Cell simulations with the code OSIRIS. The shape of the modulation is connected to the polarization of the driving laser pulse, although the wavelength of the modulation is longer than that of the pulse. Nevertheless a circularly polarized laser pulse leads to a corkscrew-like modulation, while in the case of linear polarization, the modulation lies in the polarization plane.

Development of Eulerian Code Modeling for ICF Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradley, Paul A.

2014-02-27

One of the most pressing unexplained phenomena standing in the way of ICF ignition is understanding mix and how it interacts with burn. Experiments were being designed and fielded as part of the Defect-Induced Mix Experiment (DIME) project to obtain data about the extent of material mix and how this mix influenced burn. Experiments on the Omega laser and National Ignition Facility (NIF) provided detailed data for comparison to the Eulerian code RAGE1. The Omega experiments were able to resolve the mix and provide “proof of principle” support for subsequent NIF experiments, which were fielded from July 2012 through Junemore » 2013. The Omega shots were fired at least once per year between 2009 and 2012. RAGE was not originally designed to model inertial confinement fusion (ICF) implosions. It still lacks lasers, so the code has been validated using an energy source. To test RAGE, the simulation output is compared to data and by means of postprocessing tools that were developed. Here, the various postprocessing tools are described with illustrative examples.« less

Design and construction of a DC high-brightness laser driven electron gun

NASA Astrophysics Data System (ADS)

Zhao, K.; Geng, R. L.; Wang, L. F.; Zhang, B. C.; Yu, J.; Wang, T.; Wu, G. F.; Song, J. H.; Chen, J. E.

1996-02-01

A DC high-brightness laser driven photoemissive electron gun is being developed at Peking University, in order to produce 50-100 ps electron bunches of high quality. The gun consists of a photocathode preparation chamber and a DC acceleration cavity. Different ways of fabricating photocathodes, such as chemical vapor deposition, ion beam implantation and ion beam enhanced deposition, can be adopted. The acceleration gap is designed with the aid of simulation codes EGUN and POISSON. The laser system is a mode-locked Nd-YAG oscillator proceeded by an amplifier at 10 Hz repetition rate, which can deliver three different wavelengths (1064/532/266 nm). The combination of a superconducting cavity with the photocathode preparation chamber is also discussed in this paper.

Numerical optimization of a picosecond pulse driven Ni-like Nb x-ray laser at 20.3 nm

NASA Astrophysics Data System (ADS)

Lu, X.; Zhong, J. Y.; Li, Y. J.; Zhang, J.

2003-07-01

Detailed simulations of a Ni-like Nb x-ray laser pumped by a nanosecond prepulse followed by a picosecond main pulse are presented. The atomic physics data are obtained using the Cowan code [R. D. Cowan, The Theory of Atomic Structure and Spectra (University of California Press, Berkeley, CA, 1981)]. The optimization calculations are performed in terms of the intensity of prepulse and the time delay between the prepulse and the main pulse. A high gain over 150 cm-1 is obtained for the optimized drive pulse configuration. The ray-tracing calculations suggest that the total pump energy for a saturated x-ray laser can be reduced to less than 1 J.

PCTDSE: A parallel Cartesian-grid-based TDSE solver for modeling laser-atom interactions

NASA Astrophysics Data System (ADS)

Fu, Yongsheng; Zeng, Jiaolong; Yuan, Jianmin

2017-01-01

We present a parallel Cartesian-grid-based time-dependent Schrödinger equation (TDSE) solver for modeling laser-atom interactions. It can simulate the single-electron dynamics of atoms in arbitrary time-dependent vector potentials. We use a split-operator method combined with fast Fourier transforms (FFT), on a three-dimensional (3D) Cartesian grid. Parallelization is realized using a 2D decomposition strategy based on the Message Passing Interface (MPI) library, which results in a good parallel scaling on modern supercomputers. We give simple applications for the hydrogen atom using the benchmark problems coming from the references and obtain repeatable results. The extensions to other laser-atom systems are straightforward with minimal modifications of the source code.

Dynamics of electron injection and acceleration driven by laser wakefield in tailored density profiles

DOE PAGES

Lee, Patrick; Maynard, G.; Audet, T. L.; ...

2016-11-16

The dynamics of electron acceleration driven by laser wakefield is studied in detail using the particle-in-cell code WARP with the objective to generate high-quality electron bunches with narrow energy spread and small emittance, relevant for the electron injector of a multistage accelerator. Simulation results, using experimentally achievable parameters, show that electron bunches with an energy spread of ~11% can be obtained by using an ionization-induced injection mechanism in a mm-scale length plasma. By controlling the focusing of a moderate laser power and tailoring the longitudinal plasma density profile, the electron injection beginning and end positions can be adjusted, while themore » electron energy can be finely tuned in the last acceleration section.« less

Laser plasma interaction on rugby hohlraum on the Omega Laser Facility: Comparisons between cylinder, rugby, and elliptical hohlraums

NASA Astrophysics Data System (ADS)

Masson-Laborde, P. E.; Monteil, M. C.; Tassin, V.; Philippe, F.; Gauthier, P.; Casner, A.; Depierreux, S.; Neuville, C.; Villette, B.; Laffite, S.; Seytor, P.; Fremerye, P.; Seka, W.; Teychenné, D.; Debayle, A.; Marion, D.; Loiseau, P.; Casanova, M.

2016-02-01

Gas-filled rugby-shaped hohlraums have demonstrated high performances compared to a classical similar diameter cylinder hohlraum with a nearly 40% increase of x-ray drive, 10% higher measured peak drive temperature, and an increase in neutron production. Experimental comparisons have been done between rugby, cylinder, and elliptical hohlraums. The impact of these geometry differences on the laser plasma instabilities is examined. Using comparisons with hydrodynamic simulations carried out with the code FCI2 and postprocessed by Piranah, we have been able to reproduce the stimulated Raman and Brillouin scattering spectrum of the different beams. Using a methodology based on a statistical analysis for the gain calculations, we show that the behavior of the laser plasma instabilities in rugby hohlraums can be reproduced. The efficiency of laser smoothing techniques to mitigate these instabilities are discussed, and we show that while rugby hohlraums exhibit more laser plasma instabilities than cylinder hohlraum, the latter can be mitigated in the case of an elliptical hohlraum.

Research for the jamming mechanism of high-frequency laser to the laser seeker

NASA Astrophysics Data System (ADS)

Zheng, Xingyuan; Zhang, Haiyang; Wang, Yunping; Feng, Shuang; Zhao, Changming

2013-08-01

High-frequency laser will be able to enter the enemy laser signal processing systems without encoded identification and a copy. That makes it one of the research directions of new interference sources. In order to study the interference mechanism of high-frequency laser to laser guided weapons. According to the principle of high-frequency laser interference, a series of related theoretical models such as a semi-active laser seeker coded identification model, a time door model, multi-signal processing model and a interference signal modulation processing model are established. Then seeker interfere with effective 3σ criterion is proposed. Based on this, the study of the effect of multi-source interference and signal characteristics of the effect of high repetition frequency laser interference are key research. According to the simulation system testing, the results show that the multi-source interference and interference signal frequency modulation can effectively enhance the interference effect. While the interference effect of the interference signal amplitude modulation is not obvious. The research results will provide the evaluation of high-frequency laser interference effect and provide theoretical references for high-frequency laser interference system application.

Hydrodynamics simulations of 2{omega} laser propagation in underdense gasbag plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meezan, N.B.; Divol, L.; Marinak, M.M.

2004-12-01

Recent 2{omega} laser propagation and stimulated Raman backscatter (SRS) experiments performed on the Helen laser have been analyzed using the radiation-hydrodynamics code HYDRA [M. M. Marinak, G. D. Kerbel, N. A. Gentile, O. Jones, D. Munro, S. Pollaine, T. R. Dittrich, and S. W. Haan, Phys. Plasmas 8, 2275 (2001)]. These experiments utilized two diagnostics sensitive to the hydrodynamics of gasbag targets: a fast x-ray framing camera (FXI) and a SRS streak spectrometer. With a newly implemented nonlocal thermal transport model, HYDRA is able to reproduce many features seen in the FXI images and the SRS streak spectra. Experimental andmore » simulated side-on FXI images suggest that propagation can be explained by classical laser absorption and the resulting hydrodynamics. Synthetic SRS spectra generated from the HYDRA results reproduce the details of the experimental SRS streak spectra. Most features in the synthetic spectra can be explained solely by axial density and temperature gradients. The total SRS backscatter increases with initial gasbag fill density up to {approx_equal}0.08 times the critical density, then decreases. Data from a near-backscatter imaging camera show that severe beam spray is not responsible for the trend in total backscatter. Filamentation does not appear to be a significant factor in gasbag hydrodynamics. The simulation and analysis techniques established here can be used in ongoing experimental campaigns on the Omega laser facility and the National Ignition Facility.« less

A Non Local Electron Heat Transport Model for Multi-Dimensional Fluid Codes

NASA Astrophysics Data System (ADS)

Schurtz, Guy

2000-10-01

Apparent inhibition of thermal heat flow is one of the most ancient problems in computational Inertial Fusion and flux-limited Spitzer-Harm conduction has been a mainstay in multi-dimensional hydrodynamic codes for more than 25 years. Theoretical investigation of the problem indicates that heat transport in laser produced plasmas has to be considered as a non local process. Various authors contributed to the non local theory and proposed convolution formulas designed for practical implementation in one-dimensional fluid codes. Though the theory, confirmed by kinetic calculations, actually predicts a reduced heat flux, it fails to explain the very small limiters required in two-dimensional simulations. Fokker-Planck simulations by Epperlein, Rickard and Bell [PRL 61, 2453 (1988)] demonstrated that non local effects could lead to a strong reduction of heat flow in two dimensions, even in situations where a one-dimensional analysis suggests that the heat flow is nearly classical. We developed at CEA/DAM a non local electron heat transport model suitable for implementation in our two-dimensional radiation hydrodynamic code FCI2. This model may be envisionned as the first step of an iterative solution of the Fokker-Planck equations; it takes the mathematical form of multigroup diffusion equations, the solution of which yields both the heat flux and the departure of the electron distribution function to the Maxwellian. Although direct implementation of the model is straightforward, formal solutions of it can be expressed in convolution form, exhibiting a three-dimensional tensor propagator. Reduction to one dimension retrieves the original formula of Luciani, Mora and Virmont [PRL 51, 1664 (1983)]. Intense magnetic fields may be generated by thermal effects in laser targets; these fields, as well as non local effects, will inhibit electron conduction. We present simulations where both effects are taken into account and shortly discuss the coupling strategy between them.

Simulations and measurements of hot-electron generation driven by the multibeam two-plasmon-decay instability

NASA Astrophysics Data System (ADS)

Follett, R. K.; Myatt, J. F.; Shaw, J. G.; Michel, D. T.; Solodov, A. A.; Edgell, D. H.; Yaakobi, B.; Froula, D. H.

2017-10-01

Multibeam experiments relevant to direct-drive inertial confinement fusion show the importance of nonlinear saturation mechanisms in the common-wave two-plasmon-decay (TPD) instability. Planar-target experiments on the OMEGA laser used hard x-ray measurements to study the influence of the linear common-wave growth rate on TPD-driven hot-electron production in two drive-beam configurations and over a range of overlapped laser intensities from 3.6 to 15.2 × 1014 W/cm2. The beam configuration with the larger linear common-wave growth rate had a lower intensity threshold for the onset of hot-electron production, but the linear growth rate made no significant impact on hot-electron production at high intensities. The experiments were modeled in 3-D using a hybrid code LPSE (laser plasma simulation environment) that combines a wave solver with a particle tracker to self-consistently calculate the electron velocity distribution and evolve electron Landau damping. Good quantitative agreement was obtained between the simulated and measured hot-electron distributions using a novel technique to account for macroscopic spatial and temporal variations that were present in the experiments.

Cryogenic THD and DT layer implosions with high density carbon ablators in near-vacuum hohlraums

DOE PAGES

Meezan, N. B.; Berzak Hopkins, L. F.; Le Pape, S.; ...

2015-06-02

High Density Carbon (HDC or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a DT layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a THD layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightlymore » oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 x 10¹⁵ neutrons, 40% of the 1D simulated yield.« less

Computational Modeling of Semiconductor Dynamics at Femtosecond Time Scales

NASA Technical Reports Server (NTRS)

Agrawal, Govind P.; Goorjian, Peter M.

1998-01-01

The main objective of the Joint-Research Interchange NCC2-5149 was to develop computer codes for accurate simulation of femtosecond pulse propagation in semiconductor lasers and semiconductor amplifiers [I]. The code should take into account all relevant processes such as the interband and intraband carrier relaxation mechanisms and the many-body effects arising from the Coulomb interaction among charge carriers [2]. This objective was fully accomplished. We made use of a previously developed algorithm developed at NASA Ames [3]-[5]. The new algorithm was tested on several problems of practical importance. One such problem was related to the amplification of femtosecond optical pulses in semiconductors. These results were presented in several international conferences over a period of three years. With the help of a postdoctoral fellow, we also investigated the origin of instabilities that can lead to the formation of femtosecond pulses in different kinds of lasers. We analyzed the occurrence of absolute instabilities in lasers that contain a dispersive host material with third-order nonlinearities. Starting from the Maxwell-Bloch equations, we derived general multimode equations to distinguish between convective and absolute instabilities. We find that both self-phase modulation and intensity-dependent absorption can dramatically affect the absolute stability of such lasers. In particular, the self-pulsing threshold (the so-called second laser threshold) can occur at few times the first laser threshold even in good-cavity lasers for which no self-pulsing occurs in the absence of intensity-dependent absorption. These results were presented in an international conference and published in the form of two papers.

Laser beam propagation through bulk nonlinear media: Numerical simulation and experiment

NASA Astrophysics Data System (ADS)

Kovsh, Dmitriy I.

This dissertation describes our efforts in modeling the propagation of high intensity laser pulses through optical systems consisting of one or multiple nonlinear elements. These nonlinear elements can be up to 103 times thicker than the depth of focus of the laser beam, so that the beam size changes drastically within the medium. The set of computer codes developed are organized in a software package (NLO_BPM). The ultrafast nonlinearities of the bound-electronic n2 and two-photon absorption as well as time dependent excited-state, free-carrier and thermal nonlinearities are included in the codes for modeling propagation of picosecond to nanosecond pulses and pulse trains. Various cylindrically symmetric spatial distributions of the input beam are modeled. We use the cylindrical symmetry typical of laser outputs to reduce the CPU and memory requirements making modeling a real- time task on PC's. The hydrodynamic equations describing the rarefaction of the medium due to heating and electrostriction are solved in the transient regime to determine refractive index changes on a nanosecond time scale. This effect can be simplified in some cases by an approximation that assumes an instantaneous expansion. We also find that the index change obtained from the photo-acoustic equation overshoots its steady-state value once the ratio between the pulse width and the acoustic transit time is greater than unity. We numerically study the sensitivity of the closed- aperture Z-scan experiment to nonlinear refraction for various input beam profiles. If the beam has a ring structure with a minimum (or zero) on axis in the far field, the sensitivity of Z-scan measurements can be increased by up to one order of magnitude. The linear propagation module integrated with the nonlinear beam propagation codes allows the simulation of typical experiments such as Z-scan and optical limiting experiments. We have used these codes to model the performance of optical limiters. We study two of the most promising limiter designs: the monolithic self-protective semiconductor limiter (MONOPOL) and a multi-cell tandem limiter based on a liquid solution of reverse saturable absorbing organic dye. The numerical outputs show good agreement with experimental results up to input energies where nonlinear scattering becomes significant.

Diagnosis of energy transport in iron buried layer targets using an extreme ultraviolet laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shahzad, M.; Culfa, O.; Rossall, A. K.

2015-02-15

We demonstrate the use of extreme ultra-violet (EUV) laboratory lasers in probing energy transport in laser irradiated solid targets. EUV transmission through targets containing a thin layer of iron (50 nm) encased in plastic (CH) after irradiation by a short pulse (35 fs) laser focussed to irradiances 3 × 10{sup 16} Wcm{sup −2} is measured. Heating of the iron layer gives rise to a rapid decrease in EUV opacity and an increase in the transmission of the 13.9 nm laser radiation as the iron ionizes to Fe{sup 5+} and above where the ion ionisation energy is greater than the EUV probe photon energy (89 eV).more » A one dimensional hydrodynamic fluid code HYADES has been used to simulate the temporal variation in EUV transmission (wavelength 13.9 nm) using IMP opacity values for the iron layer and the simulated transmissions are compared to measured transmission values. When a deliberate pre-pulse is used to preform an expanding plastic plasma, it is found that radiation is important in the heating of the iron layer while for pre-pulse free irradiation, radiation transport is not significant.« less

Two-plasmon decay mitigation in direct-drive inertial-confinement-fusion experiments using multilayer targets

DOE PAGES

Follett, R. K.; Delettrez, J. A.; Edgell, D. H.; ...

2016-04-15

Multilayer direct-drive inertial-confinement-fusion (ICF) targets are shown to significantly reduce two-plasmon-decay (TPD) driven hot-electron production while maintaining high hydrodynamic efficiency. Implosion experiments on the OMEGA Laser used targets with silicon layered between an inner beryllium and outer silicon-doped plastic ablator. A factor of five reduction in hot-electron generation (> 50 keV) was observed in the multilayer targets relative to pure CH targets. Three-dimensional simulations of the TPD driven hot-electron production using a laser-plasma interaction code (LPSE) that includes nonlinear and kinetic effects show excellent agreement with the measurements. As a result, the simulations suggest that the reduction in hot-electron productionmore » observed in the multilayer targets is primarily due to increased electron-ion collisional damping.« less

Modeling of microstructure evolution in direct metal laser sintering: A phase field approach

NASA Astrophysics Data System (ADS)

Nandy, Jyotirmoy; Sarangi, Hrushikesh; Sahoo, Seshadev

2017-02-01

Direct Metal Laser Sintering (DMLS) is a new technology in the field of additive manufacturing, which builds metal parts in a layer by layer fashion directly from the powder bed. The process occurs within a very short time period with rapid solidification rate. Slight variations in the process parameters may cause enormous change in the final build parts. The physical and mechanical properties of the final build parts are dependent on the solidification rate which directly affects the microstructure of the material. Thus, the evolving of microstructure plays a vital role in the process parameters optimization. Nowadays, the increase in computational power allows for direct simulations of microstructures during materials processing for specific manufacturing conditions. In this study, modeling of microstructure evolution of Al-Si-10Mg powder in DMLS process was carried out by using a phase field approach. A MATLAB code was developed to solve the set of phase field equations, where simulation parameters include temperature gradient, laser scan speed and laser power. The effects of temperature gradient on microstructure evolution were studied and found that with increase in temperature gradient, the dendritic tip grows at a faster rate.

Beam dynamics simulations of the injector for a compact THz source

NASA Astrophysics Data System (ADS)

Li, Ji; Pei, Yuan-Ji; Shang, Lei; Feng, Guang-Yao; Hu, Tong-Ning; Chen, Qu-Shan; Li, Cheng-Long

2014-08-01

Terahertz radiation has broad application prospects due to its ability to penetrate deep into many organic materials without the damage caused by ionizing radiations. A free electron laser (FEL)-based THz source is the best choice to produce high-power radiation. In this paper, a 14 MeV injector is introduced for generating high-quality beam for FEL, is composed of an EC-ITC RF gun, compensating coils and a travelling-wave structure. Beam dynamics simulations have been done with ASTRA code to verify the design and to optimize parameters. Simulations of the operating mode at 6 MeV have also been executed.

Measurements and non-local thermodynamic equilibrium modeling of mid-Z plasma emission

NASA Astrophysics Data System (ADS)

Jacquet, L.; Primout, M.; Kaiser, P.; Clouët, J. F.; Girard, F.; Villette, B.; Reverdin, C.; Oudot, G.

2015-12-01

The x-ray yields from laser-irradiated thin foils of iron, copper, zinc, and germanium have been measured in the soft and multi-keV x-ray ranges at the OMEGA laser at the Laboratory for Laser Energetics. The incident laser power had a pre-pulse to enhance the x-ray emission of a 1 ns flat-top main pulse. The experimental results have been compared with post-shot simulations performed with the two-dimensional radiation-hydrodynamics code FCI2. A new non-local thermodynamic equilibrium model, NOO-RAD, have been incorporated into FCI2. In this approach, the plasma ionization state is in-line calculated by the atomic physics NOHEL package. In the soft x-ray bands, both simulations using RADIOM [M. Busquet, Phys. Fluids B 5, 4191 (1993)] and NOO-RAD clearly over-predict the powers and energies measured by a broad-band spectrometer. In one case (the iron foil), the discrepancy between the measured and simulated x-ray output is nevertheless significantly reduced when NOO-RAD is used in the simulations. In the multi-keV x-ray bands, the simulations display a strong sensitivity to the coupling between the electron thermal conductivity and the NLTE models, and for some particular combinations of these, provide a close match to the measured emission. The comparison between the measured and simulated H-like to He-like line-intensity ratios deduced from high-resolution spectra indicates higher experimental electron temperatures were achieved, compared to the simulated ones. Measurements of the plasma conditions have been achieved using the Thomson-scattering diagnostic. The electron temperatures are found to range from 3 to 5 keV at the end of the laser pulse and are greater than predicted by the simulations. The measured flow velocities are in reasonable agreement with the calculated ones. This last finding gives us confidence in our numerical predictions for the plasma parameters, which are over that time mainly determined by hydrodynamics, such as the mass densities and the ion temperatures.

Numerical simulation of exploding pusher targets

NASA Astrophysics Data System (ADS)

Atzeni, S.; Rosenberg, M. J.; Gatu Johnson, M.; Petrasso, R. D.

2017-10-01

Exploding pusher targets, i.e. gas-filled large aspect-ratio glass or plastic shells, driven by a strong laser-generated shock, are widely used as pulsed sources of neutrons and fast charged particles. Recent experiments on exploding pushers provided evidence for the transition from a purely fluid behavior to a kinetic one. Indeed, fluid models largely overpredict yield and temperature as the Knudsen number Kn (ratio of ion mean-free path to compressed gas radius) is comparable or larger than one. At Kn = 0.3 - 1, fluid codes reasonably estimate integral quantities as yield and neutron-averaged temperatures, but do not reproduce burn radii, burn profiles and DD/DHe3 yield ratio. This motivated a detailed simulation study of intermediate-Kn exploding pushers. We will show how simulation results depend on models for laser-interaction, electron conductivity (flux-limited local vs nonlocal), viscosity (physical vs artificial), and ion mixing. Work partially supported by Sapienza Project C26A15YTMA, Sapienza 2016 (n. 257584), and Eurofusion Project AWP17-ENR-IFE-CEA-01.

Full-wave and ray-based modeling of cross-beam energy transfer between laser beams with distributed phase plates and polarization smoothing

DOE PAGES

Follett, R. K.; Edgell, D. H.; Froula, D. H.; ...

2017-10-20

Radiation-hydrodynamic simulations of inertial confinement fusion (ICF) experiments rely on ray-based cross-beam energy transfer (CBET) models to calculate laser energy deposition. The ray-based models assume locally plane-wave laser beams and polarization averaged incoherence between laser speckles for beams with polarization smoothing. The impact of beam speckle and polarization smoothing on crossbeam energy transfer (CBET) are studied using the 3-D wave-based laser-plasma-interaction code LPSE. The results indicate that ray-based models under predict CBET when the assumption of spatially averaged longitudinal incoherence across the CBET interaction region is violated. A model for CBET between linearly-polarized speckled beams is presented that uses raymore » tracing to solve for the real speckle pattern of the unperturbed laser beams within the eikonal approximation and gives excellent agreement with the wavebased calculations. Lastly, OMEGA-scale 2-D LPSE calculations using ICF relevant plasma conditions suggest that the impact of beam speckle on laser absorption calculations in ICF implosions is small (< 1%).« less

Full-wave and ray-based modeling of cross-beam energy transfer between laser beams with distributed phase plates and polarization smoothing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Follett, R. K.; Edgell, D. H.; Froula, D. H.

Radiation-hydrodynamic simulations of inertial confinement fusion (ICF) experiments rely on ray-based cross-beam energy transfer (CBET) models to calculate laser energy deposition. The ray-based models assume locally plane-wave laser beams and polarization averaged incoherence between laser speckles for beams with polarization smoothing. The impact of beam speckle and polarization smoothing on crossbeam energy transfer (CBET) are studied using the 3-D wave-based laser-plasma-interaction code LPSE. The results indicate that ray-based models under predict CBET when the assumption of spatially averaged longitudinal incoherence across the CBET interaction region is violated. A model for CBET between linearly-polarized speckled beams is presented that uses raymore » tracing to solve for the real speckle pattern of the unperturbed laser beams within the eikonal approximation and gives excellent agreement with the wavebased calculations. Lastly, OMEGA-scale 2-D LPSE calculations using ICF relevant plasma conditions suggest that the impact of beam speckle on laser absorption calculations in ICF implosions is small (< 1%).« less

Optimization of laser-plasma injector via beam loading effects using ionization-induced injection

NASA Astrophysics Data System (ADS)

Lee, P.; Maynard, G.; Audet, T. L.; Cros, B.; Lehe, R.; Vay, J.-L.

2018-05-01

Simulations of ionization-induced injection in a laser driven plasma wakefield show that high-quality electron injectors in the 50-200 MeV range can be achieved in a gas cell with a tailored density profile. Using the PIC code Warp with parameters close to existing experimental conditions, we show that the concentration of N2 in a hydrogen plasma with a tailored density profile is an efficient parameter to tune electron beam properties through the control of the interplay between beam loading effects and varying accelerating field in the density profile. For a given laser plasma configuration, with moderate normalized laser amplitude, a0=1.6 and maximum electron plasma density, ne 0=4 ×1018 cm-3 , the optimum concentration results in a robust configuration to generate electrons at 150 MeV with a rms energy spread of 4% and a spectral charge density of 1.8 pC /MeV .

Numerical Simulations of Free Surface Magnetohydrodynamic Flows

NASA Astrophysics Data System (ADS)

Samulyak, Roman; Glimm, James; Oh, Wonho; Prykarpatskyy, Yarema

2003-11-01

We have developed a numerical algorithm and performed simulations of magnetohydrodynamic (MHD) free surface flows. The corresponding system of MHD equations is a system of strongly coupled hyperbolic and parabolic/elliptic equations in moving and geometrically complex domains. The hyperbolic system is solved using the front tracking technique for the free fluid interface. Parallel algorithms for solving elliptic and parabolic equations are based on a finite element discretization on moving grids dynamically conforming to fluid interfaces. The method has been implemented as an MHD extension of the FronTier code. The code has been applied for modeling the behavior of lithium and mercury jets in magnetic fields, laser ablation plumes, and the Richtmyer-Meshkov instability of a liquid mercury jet interacting with a high energy proton pulse in a strong magnetic field. Such an instability occurs in the target for the Muon Collider.

Advanced Concept Exploration for Fast Ignition Science Program, Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stephens, Richard Burnite; McLean, Harry M.; Theobald, Wolfgang

The Fast Ignition (FI) Concept for Inertial Confinement Fusion (ICF) has the potential to provide a significant advance in the technical attractiveness of Inertial Fusion Energy reactors. FI differs from conventional “central hot spot” (CHS) target ignition by decoupling compression from heating: using a laser (or heavy ion beam or Z pinch) drive pulse (10’s of nanoseconds) to create a dense fuel and a second, much shorter (~10 picoseconds) high intensity pulse to ignite a small volume within the dense fuel. The physics of fast ignition process was the focus of our Advanced Concept Exploration (ACE) program. Ignition depends criticallymore » on two major issues involving Relativistic High Energy Density (RHED) physics: The laser-induced creation of fast electrons and their propagation in high-density plasmas. Our program has developed new experimental platforms, diagnostic packages, computer modeling analyses, and taken advantage of the increasing energy available at laser facilities to advance understanding of the fundamental physics underlying these issues. Our program had three thrust areas: • Understand the production and characteristics of fast electrons resulting from FI relevant laser-plasma interactions and their dependence on laser prepulse and laser pulse length. • Investigate the subsequent fast electron transport in solid and through hot (FI-relevant) plasmas. • Conduct and understand integrated core-heating experiments by comparison to simulations. Over the whole period of this project (three years for this contract), we have greatly advanced our fundamental understanding of the underlying properties in all three areas: • Comprehensive studies on fast electron source characteristics have shown that they are controlled by the laser intensity distribution and the topology and plasma density gradient. Laser pre-pulse induced pre-plasma in front of a solid surface results in increased stand-off distances from the electron origin to the high density target as well as large and erratic spread of the electron beam with increasing short pulse duration. We have demonstrated, using newly available higher contrast lasers, an improved energy coupling, painting a promising picture for FI feasibility. • Our detailed experiments and analyses of fast electron transport dependence on target material have shown that it is feasible to collimate fast electron beam by self-generated resistive magnetic fields in engineered targets with a rather simple geometry. Stable and collimated electron beam with spot size as small as 50-μm after >100-μm propagation distance (an angular divergence angle of 20°!) in solid density plasma targets has been demonstrated with FI-relevant (10-ps, >1-kJ) laser pulses Such collimated beam would meet the required heating beam size for FI. • Our new experimental platforms developed for the OMEGA laser (i.e., i) high resolution 8 keV backlighter platform for cone-in-shell implosion and ii) the 8 keV imaging with Cu-doped shell targets for detailed transport characterization) have enabled us to experimentally confirm fuel assembly from cone-in-shell implosion with record-high areal density. We have also made the first direct measurement of fast electron transport and spatial energy deposition in integrated FI experiments enabling the first experiment-based benchmarking of integrated simulation codes. Executing this program required a large team. It was managed as a collaboration between General Atomics (GA), Lawrence Livermore National Laboratory (LLNL), and the Laboratory for Laser Energetics (LLE). GA fulfills its responsibilities jointly with the University of California, San Diego (UCSD), The Ohio State University (OSU) and the University of Nevada at Reno (UNR). The division of responsibility was as follows: (1) LLE had primary leadership for channeling studies and the integrated energy transfer, (2) LLNL led the development of measurement methods, analysis, and deployment of diagnostics, and (3) GA together with UCSD, OSU and UNR studied the detailed energy-transfer physics. The experimental program was carried out using the Titan laser at the Jupiter Laser Facility at LLNL, the OMEGA and OMEGA EP lasers at LLE and the Texas Petawatt laser at the University of Texas, Austin. Modeling has been pursued on large computing facilities at LLNL, OSU, and UCSD using codes developed (by us and others) within the HEDLP program, commercial codes, and by leveraging existing simulations codes developed by the National Nuclear Security Administration ICF program. One important aspect of this program was the involvement and training of young scientists including postdoctoral fellows and graduate students. This project generated an impressive forty articles in high quality journals including nine (two under review) in Physical Review Letters during the three years of this grant and five graduate students completed their doctoral dissertations.« less

A Post-Processing Receiver for the Lunar Laser Communications Demonstration Project

NASA Technical Reports Server (NTRS)

Srinivasan, Meera; Birnbaum, Kevin; Cheng, Michael; Quirk, Kevin

2013-01-01

The Lunar Laser Communications Demonstration Project undertaken by MIT Lincoln Laboratory and NASA's Goddard Space Flight Center will demonstrate high-rate laser communications from lunar orbit to the Earth. NASA's Jet Propulsion Laboratory is developing a backup ground station supporting a data rate of 39 Mbps that is based on a non-real-time software post-processing receiver architecture. This approach entails processing sample-rate-limited data without feedback in the presence high uncertainty in downlink clock characteristics under low signal flux conditions. In this paper we present a receiver concept that addresses these challenges with descriptions of the photodetector assembly, sample acquisition and recording platform, and signal processing approach. End-to-end coded simulation and laboratory data analysis results are presented that validate the receiver conceptual design.

Investigation of ionization-induced electron injection in a wakefield driven by laser inside a gas cell

DOE PAGES

Audet, T. L.; Hansson, M.; Lee, P.; ...

2016-02-16

Ionization-induced electron injection was investigated experimentally by focusing a driving laser pulse with a maximum normalized potential of 1.2 at different positions along the plasma density profile inside a gas cell, filled with a gas mixture composed of 99%H 2+1%N 2. Changing the laser focus position relative to the gas cell entrance controls the accelerated electron bunch properties, such as the spectrum width, maximum energy, and accelerated charge. Simulations performed using the 3D particle-in-cell code WARP with a realistic density profile give results that are in good agreement with the experimental ones. Lastly, we discuss the interest of this regimemore » for optimizing the bunch charge in a selected energy window.« less

Method to generate a pulse train of few-cycle coherent radiation

DOE PAGES

Garcia, Bryant; Hemsing, Erik; Raubenheimer, Tor; ...

2016-09-06

We develop a method to generate a long pulse train of few-cycle coherent radiation by modulating an electron beam with a high power laser. The large energy modulation disperses the beam in a radiating undulator and leads to the production of phase-locked few-cycle coherent radiation pulses. These pulses are produced at a high harmonic of the modulating laser, and are longitudinally separated by the modulating laser wavelength. Here, we discuss an analytical model for this scheme and investigate the temporal and spectral properties of this radiation. This model is compared with numerical simulation results using the unaveraged code Puffin. Wemore » examine various harmful effects and how they might be avoided, as well as a possible experimental realization of this scheme.« less

On the Initiation Mechanism in Exploding Bridgewire and Laser Detonators

NASA Astrophysics Data System (ADS)

Stewart, D. Scott; Thomas, Keith A.; Clarke, S.; Mallett, H.; Martin, E.; Martinez, M.; Munger, A.; Saenz, Juan

2006-07-01

Since its invention by Los Alamos during the Manhattan Project era the exploding bridgewire detonator (EBW) has seen tremendous use and study. Recent development of a laser-powered device with detonation properties similar to an EBW is reviving interest in the basic physics of the deflagration-to-detonation (DDT) process in both of these devices. Cutback experiments using both laser interferometry and streak camera observations are providing new insight into the initiation mechanism in EBWs. These measurements are being correlated to a DDT model of compaction to detonation and shock to detonation developed previously by Xu and Stewart. The DDT model is incorporated into a high-resolution, multi-material model code for simulating the complete process. Model formulation and the modeling issues required to describe the test data will be discussed.

Effects of the Atmosphere on the Propagation of 10.6-micro Laser Beams.

PubMed

Hayes, J N; Ulrich, P B; Aitken, A H

1972-02-01

This paper gives an overview of the use of a wave optics computer code to model the propagation of high power CO(2) laser beams in the atmosphere. The nonlinear effects of atmospheric heating and kinetic cooling phenomena are included in the analysis. Only steady-state, nonturbulent cases are studied. Thermal conduction and free convection are assumed negligible compared to other effects included in the calculation. Results showing the important effect of water vapor concentration on beam quality are given. Beam slewing is also studied. Comparison is made with geometrical optics results, and good agreement is found with laboratory experiments that simulate atmospheric propagation.

Refractive collimation beam shaper design and sensitivity analysis using a free-form profile construction method.

PubMed

Tsai, Chung-Yu

2017-07-01

A refractive laser beam shaper comprising two free-form profiles is presented. The profiles are designed using a free-form profile construction method such that each incident ray is directed in a certain user-specified direction or to a particular point on the target surface so as to achieve the required illumination distribution of the output beam. The validity of the proposed design method is demonstrated by means of ZEMAX simulations. The method is mathematically straightforward and easily implemented in computer code. It thus provides a convenient tool for the design and sensitivity analysis of laser beam shapers and similar optical components.

Design and realization of the optical and electron beam alignment system for the HUST-FEL oscillator

NASA Astrophysics Data System (ADS)

Fu, Q.; Tan, P.; Liu, K. F.; Qin, B.; Liu, X.

2018-06-01

A Free Electron Laser(FEL) oscillator with radiation wavelength at 30-100 μ m is under commissioning at Huazhong University of Science and Technology (HUST). This work presents the schematic design and realization procedures for the optical and beam alignment system in the HUST FEL facility. The optical cavity misalignment effects are analyzed with the code OPC + Genesis 1.3, and the tolerance of misalignment is proposed with the simulation result. Depending on undulator mechanical benchmarks, a laser indicating system has been built up as reference datum. The alignment of both optical axis and beam trajectory were achieved by this alignment system.

Possibilities of improving the performance of an autonomous cw chemical DF laser by replacing the slot nozzles by the ramp ones in the nozzle array

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bashkin, A S; Gurov, L V; Kurdyukov, M V

2011-08-31

The results of a comparative numerical study of the performance of an autonomous cw chemical DF laser are obtained by simulating the processes in the nozzles and laser cavity where several configurations of slot and ramp nozzle arrays are employed. Three-dimensional Navier-Stokes equations solved with the Ansys CFX software are used to describe the reacting multicomponent flow in the nozzles and laser cavity. To investigate lasing characteristics, a supplementary code is developed and is used to calculate the radiation intensity in the Fabry-Perot resonator, taking into account its nonuniform distribution along the aperture width and height. It is shown thatmore » the use of the nozzle array consisting of ramp nozzles, which, in contrast to the slot nozzles, provide enhanced mixing of the reactants makes it possible to improve the laser performance in the case of a high-pressure (more than 15 Torr) active medium. (control of radiation parameters)« less

Matching the laser generated p bunch into a crossbar-H drift tube linac

NASA Astrophysics Data System (ADS)

Almomani, A.; Droba, M.; Ratzinger, U.; Hofmann, I.

2012-05-01

Proton bunches with energies up to 30 MeV have been measured at the PHELIX laser. Because of the laser-plasma interactions at a power density of about 4×1019W/cm2, a total yield of 1.5×1013protons was produced. For the reference energy of 10 MeV, the yield within ±0.5MeV was exceeding 1010protons. The important topic for a further acceleration of the laser generated bunch is the matching into the acceptance of an rf accelerator stage. With respect to the high space charge forces and the transit energy range, only drift tube linacs seem adequate for this purpose. A crossbar H-type (CH) cavity was chosen as the linac structure. Optimum emittance values for the linac injection are compared with the available laser generated beam parameters. Options for beam matching into a CH structure by a pulsed magnetic solenoid and by using the simulation codes LASIN and LORASR are presented.

Vlasov Simulation of Ion Acceleration in the Field of an Intense Laser Incident on an Overdense Plasma

NASA Astrophysics Data System (ADS)

Shoucri, Magdi; Charbonneau-Lefort, Mathieu; Afeyan, Bedros

2008-11-01

We study the interaction of a high intensity laser with an overdense plasma. When the intensity of the laser is sufficiently high to make the electrons relativistic, unusual interactions between the EM wave and the surface of the plasma take place. We use an Eulerian Vlasov code for the numerical solution of the one-dimensional two-species relativistic Vlasov-Maxwell equations [1]. The results show that the incident laser steepens the density profile significantly. There is a large build-up of electron density at the plasma edge, and as a consequence a large charge separation that is induced under the action of the intense laser field. This results in an intense quasistatic longitudinal electric field generated at the surface of the plasma which accelerates ions in the forward direction. We will show the details of the formation of the longitudinal edge electric field and of electron and ion phase-space structures. [1] M. Charbonneau-Lefort, M. Shoucri, B. Afeyan , Proc. of the EPS Conference, Greece (2008).

Simulations of a Molecular Cloud experiment using CRASH

NASA Astrophysics Data System (ADS)

Trantham, Matthew; Keiter, Paul; Vandervort, Robert; Drake, R. Paul; Shvarts, Dov

2017-10-01

Recent laboratory experiments explore molecular cloud radiation hydrodynamics. The experiment irradiates a gold foil with a laser producing x-rays to drive the implosion or explosion of a foam ball. The CRASH code, an Eulerian code with block-adaptive mesh refinement, multigroup diffusive radiation transport, and electron heat conduction developed at the University of Michigan to design and analyze high-energy-density experiments, is used to perform a parameter search in order to identify optically thick, optically thin and transition regimes suitable for these experiments. Specific design issues addressed by the simulations are the x-ray drive temperature, foam density, distance from the x-ray source to the ball, as well as other complicating issues such as the positioning of the stalk holding the foam ball. We present the results of this study and show ways the simulations helped improve the quality of the experiment. This work is funded by the LLNL under subcontract B614207 and NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0002956.

Optical Phase Recovery and Locking in a PPM Laser Communication Link

NASA Technical Reports Server (NTRS)

Aveline, David C.; Yu, Nan; Farr, William H.

2012-01-01

Free-space optical communication holds great promise for future space missions requiring high data rates. For data communication in deep space, the current architecture employs pulse position modulation (PPM). In this scheme, the light is transmitted and detected as pulses within an array of time slots. While the PPM method is efficient for data transmission, the phase of the laser light is not utilized. The phase coherence of a PPM optical signal has been investigated with the goal of developing a new laser communication and ranging scheme that utilizes optical coherence within the established PPM architecture and photon-counting detection (PCD). Experimental measurements of a PPM modulated optical signal were conducted, and modeling code was developed to generate random PPM signals and simulate spectra via FFT (Fast Fourier Transform) analysis. The experimental results show very good agreement with the simulations and confirm that coherence is preserved despite modulation with high extinction ratios and very low duty cycles. A real-time technique has been developed to recover the phase information through the mixing of a PPM signal with a frequency-shifted local oscillator (LO). This mixed signal is amplified, filtered, and integrated to generate a voltage proportional to the phase of the modulated signal. By choosing an appropriate time constant for integration, one can maintain a phase lock despite long dark times between consecutive pulses with low duty cycle. A proof-of-principle demonstration was first achieved with an RF-based PPM signal and test setup. With the same principle method, an optical carrier within a PPM modulated laser beam could also be tracked and recovered. A reference laser was phase-locked to an independent pulsed laser signal with low-duty-cycle pseudo-random PPM codes. In this way, the drifting carrier frequency in the primary laser source is tracked via its phase change in the mixed beat note, while the corresponding voltage feedback maintains the phase lock between the two laser sources. The novelty and key significance of this work is that the carrier phase information can be harnessed within an optical communication link based on PPM-PCD architecture. This technology development could lead to quantum-limited efficient performance within the communication link itself, as well as enable high-resolution optical tracking capabilities for planetary science and spacecraft navigation.

Influence of incident angle on the decoding in laser polarization encoding guidance

NASA Astrophysics Data System (ADS)

Zhou, Muchun; Chen, Yanru; Zhao, Qi; Xin, Yu; Wen, Hongyuan

2009-07-01

Dynamic detection of polarization states is very important for laser polarization coding guidance systems. In this paper, a set of dynamic polarization decoding and detection system used in laser polarization coding guidance was designed. Detection process of the normal incident polarized light is analyzed with Jones Matrix; the system can effectively detect changes in polarization. Influence of non-normal incident light on performance of polarization decoding and detection system is studied; analysis showed that changes in incident angle will have a negative impact on measure results, the non-normal incident influence is mainly caused by second-order birefringence and polarization sensitivity effect generated in the phase delay and beam splitter prism. Combined with Fresnel formula, decoding errors of linearly polarized light, elliptically polarized light and circularly polarized light with different incident angles into the detector are calculated respectively, the results show that the decoding errors increase with increase of incident angle. Decoding errors have relations with geometry parameters, material refractive index of wave plate, polarization beam splitting prism. Decoding error can be reduced by using thin low-order wave-plate. Simulation of detection of polarized light with different incident angle confirmed the corresponding conclusions.

Emission of energetic protons from relativistic intensity laser interaction with a cone-wire target.

PubMed

Paradkar, B S; Yabuuchi, T; Sawada, H; Higginson, D P; Link, A; Wei, M S; Stephens, R B; Krasheninnikov, S I; Beg, F N

2012-11-01

Emission of energetic protons (maximum energy ∼18 MeV) from the interaction of relativistic intensity laser with a cone-wire target is experimentally measured and numerically simulated with hybrid particle-in-cell code, lsp [D. R. Welch et al., Phys. Plasmas 13, 063105 (2006)]. The protons originate from the wire attached to the cone after the OMEGA EP laser (670 J, 10 ps, 5 × 10^{18} W/cm^{2}) deposits its energy inside the cone. These protons are accelerated from the contaminant layer on the wire surface, and are measured in the radial direction, i.e., in a direction transverse to the wire length. Simulations show that the radial electric field, responsible for the proton acceleration, is excited by three factors, viz., (i) transverse momentum of the relativistic fast electrons beam entering into the wire, (ii) scattering of electrons inside the wire, and (iii) refluxing of escaped electrons by "fountain effect" at the end of the wire. The underlying physics of radial electric field and acceleration of protons is discussed.

Examination of Wildland Fire Spread at Small Scales Using Direct Numerical Simulations and High-Speed Laser Diagnostics

NASA Astrophysics Data System (ADS)

Wimer, N. T.; Mackoweicki, A. S.; Poludnenko, A. Y.; Hoffman, C.; Daily, J. W.; Rieker, G. B.; Hamlington, P.

2017-12-01

Results are presented from a joint computational and experimental research effort focused on understanding and characterizing wildland fire spread at small scales (roughly 1m-1mm) using direct numerical simulations (DNS) with chemical kinetics mechanisms that have been calibrated using data from high-speed laser diagnostics. The simulations are intended to directly resolve, with high physical accuracy, all small-scale fluid dynamic and chemical processes relevant to wildland fire spread. The high fidelity of the simulations is enabled by the calibration and validation of DNS sub-models using data from high-speed laser diagnostics. These diagnostics have the capability to measure temperature and chemical species concentrations, and are used here to characterize evaporation and pyrolysis processes in wildland fuels subjected to an external radiation source. The chemical kinetics code CHEMKIN-PRO is used to study and reduce complex reaction mechanisms for water removal, pyrolysis, and gas phase combustion during solid biomass burning. Simulations are then presented for a gaseous pool fire coupled with the resulting multi-step chemical reaction mechanisms, and the results are connected to the fundamental structure and spread of wildland fires. It is anticipated that the combined computational and experimental approach of this research effort will provide unprecedented access to information about chemical species, temperature, and turbulence during the entire pyrolysis, evaporation, ignition, and combustion process, thereby permitting more complete understanding of the physics that must be represented by coarse-scale numerical models of wildland fire spread.

Intense laser pulse propagation in ionizing gases

NASA Astrophysics Data System (ADS)

Bian, Zhigang

2003-10-01

There have been considerable technological advances in the development of high intensity, short pulse lasers. However, high intensity laser pulses are subject to various laser-plasma instabilities. In this thesis, a theory is developed to study the scattering instability that occurs when a laser pulse propagates through and ionizes a gas. The instability is due to the intensity dependence of the ionization rate, which leads to a transversely structured free electron density. The instability is convective in the frame of laser pulse, but can have a relatively short growth length scaling as Lg˜k0/k2p where k0 is the laser wave number, k2p=w2p/c 2 and op is the plasma frequency. The most unstable perturbations correspond to a scattering angle for which the transverse wave number is around the plasma wave number, k p. The scattered light is frequency upshifted. The comparison between simple analytic theory and numerical simulation shows good agreement. Instabilities can drastically change the shape of the laser pulse and reduce the propagation distance of the laser pulse. Therefore, we change the propagation conditions and reduce the laser-plasma interaction possibilities in applications which require an interaction length well in excess of the Rayleigh length of the laser beam. One of the methods is to use a capillary to propagate the laser pulse. We studied the propagation of short pulses in a glass capillary. The propagation is simulated using the code WAKE, which has been modified to treat the case in which the simulation boundary is the wall of a capillary. Parameters that were examined include transmission efficiency of the waveguides as a function of gas pressure, laser intensity, and waveguide length, which is up to 40 Rayleigh lengths. The transmission efficiency decreases with waveguide length due to energy loss through the side-walls of the capillary. The loss increases with gas pressure due to ionization of the gas and scattering of the radiation. The intensity on the inner wall of the capillary is monitored to assure realistic simulations, consistent with optical breakdown of the waveguide material. Generally speaking the intensity on the wall increases with gas pressure due to the scattering of the lowest order capillary mode. Finally, the high order harmonic generation (HHG) in a capillary is investigated. The phase matching condition is studied to increase the conversion efficiency for high order harmonics generation. The phase matching occurs as a balance of the dispersion of the neutral gas, plasma and the waveguide.

On the performance of joint iterative detection and decoding in coherent optical channels with laser frequency fluctuations

NASA Astrophysics Data System (ADS)

Castrillón, Mario A.; Morero, Damián A.; Agazzi, Oscar E.; Hueda, Mario R.

2015-08-01

The joint iterative detection and decoding (JIDD) technique has been proposed by Barbieri et al. (2007) with the objective of compensating the time-varying phase noise and constant frequency offset experienced in satellite communication systems. The application of JIDD to optical coherent receivers in the presence of laser frequency fluctuations has not been reported in prior literature. Laser frequency fluctuations are caused by mechanical vibrations, power supply noise, and other mechanisms. They significantly degrade the performance of the carrier phase estimator in high-speed intradyne coherent optical receivers. This work investigates the performance of the JIDD algorithm in multi-gigabit optical coherent receivers. We present simulation results of bit error rate (BER) for non-differential polarization division multiplexing (PDM)-16QAM modulation in a 200 Gb/s coherent optical system that includes an LDPC code with 20% overhead and net coding gain of 11.3 dB at BER = 10-15. Our study shows that JIDD with a pilot rate ⩽ 5 % compensates for both laser phase noise and laser frequency fluctuation. Furthermore, since JIDD is used with non-differential modulation formats, we find that gains in excess of 1 dB can be achieved over existing solutions based on an explicit carrier phase estimator with differential modulation. The impact of the fiber nonlinearities in dense wavelength division multiplexing (DWDM) systems is also investigated. Our results demonstrate that JIDD is an excellent candidate for application in next generation high-speed optical coherent receivers.

Raytracing and Direct-Drive Targets

NASA Astrophysics Data System (ADS)

Schmitt, Andrew J.; Bates, Jason; Fyfe, David; Eimerl, David

2013-10-01

Accurate simulation of the effects of laser imprinting and drive asymmetries in directly driven targets requires the ability to distinguish between raytrace noise and the intensity structure produced by the spatial and temporal incoherence of optical smoothing. We have developed and implemented a smoother raytrace algorithm for our mpi-parallel radiation hydrodynamics code, FAST3D. The underlying approach is to connect the rays into either sheets (in 2D) or volume-enclosing chunks (in 3D) so that the absorbed energy distribution continuously covers the propagation area illuminated by the laser. We will describe the status and show the different scalings encountered in 2D and 3D problems as the computational size, parallelization strategy, and number of rays is varied. Finally, we show results using the method in current NIKE experimental target simulations and in proposed symmetric and polar direct-drive target designs. Supported by US DoE/NNSA.

Dependence of core heating properties on heating pulse duration and intensity

NASA Astrophysics Data System (ADS)

Johzaki, Tomoyuki; Nagatomo, Hideo; Sunahara, Atsushi; Cai, Hongbo; Sakagami, Hitoshi; Mima, Kunioki

2009-11-01

In the cone-guiding fast ignition, an imploded core is heated by the energy transport of fast electrons generated by the ultra-intense short-pulse laser at the cone inner surface. The fast core heating (˜800eV) has been demonstrated at integrated experiments with GEKKO-XII+ PW laser systems. As the next step, experiments using more powerful heating laser, FIREX, have been started at ILE, Osaka university. In FIREX-I (phase-I of FIREX), our goal is the demonstration of efficient core heating (Ti ˜ 5keV) using a newly developed 10kJ LFEX laser. In the first integrated experiments, the LFEX laser is operated with low energy mode (˜0.5kJ/4ps) to validate the previous GEKKO+PW experiments. Between the two experiments, though the laser energy is similar (˜0.5kJ), the duration is different; ˜0.5ps in the PW laser and ˜ 4ps in the LFEX laser. In this paper, we evaluate the dependence of core heating properties on the heating pulse duration on the basis of integrated simulations with FI^3 (Fast Ignition Integrated Interconnecting) code system.

Pseudorandom Noise Code-Based Technique for Cloud and Aerosol Discrimination Applications

NASA Technical Reports Server (NTRS)

Campbell, Joel F.; Prasad, Narasimha S.; Flood, Michael A.; Harrison, Fenton Wallace

2011-01-01

NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the detection of CO2 and O2 from space based platforms suitable for ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multi-frequency, intensity modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a PN code based technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated, Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths. Keywords: ASCENDS, CO2 sensing, O2 sensing, PN codes, CW lidar

Quasi-matched propagation of an ultrashort and intense laser pulse in a plasma channel

NASA Astrophysics Data System (ADS)

Benedetti, Carlo; Schroeder, Carl; Esarey, Eric; Leemans, Wim

2011-10-01

The propagation of an ultrashort and relativistically-intense laser pulse in a preformed parabolic plasma channel is investigated. The nonlinear paraxial wave equation is solved both analytically and numerically. Numerical solutions are obtained using the 2D cylindrical, envelope, ponderomotive, hybrid PIC/fluid code INF&RNO, recently developed at LBNL. For an arbitrary laser pulse profile with a given power for each longitudinal slice (less then the critical power for self-focusing), we determine the laser intensity distribution ensuring matched propagation in the channel, neglecting non-paraxial effects (self-steepening, red-shifting, etc.). Similarly, in the case of a Gaussian pulse profile, we determine the optimal channel depth yielding a quasi-matched laser propagation, including the plasma density modification induced by the laser-pulse. The analytical results obtained for both cases in the weakly-relativistic intensity regime are presented and validated through comparison with numerical simulations. Work supported by the Office of Science, Office of High Energy Physics, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Energy transport in short-pulse-laser-heated targets measured using extreme ultraviolet laser backlighting.

PubMed

Wilson, L A; Tallents, G J; Pasley, J; Whittaker, D S; Rose, S J; Guilbaud, O; Cassou, K; Kazamias, S; Daboussi, S; Pittman, M; Delmas, O; Demailly, J; Neveu, O; Ros, D

2012-08-01

The accurate characterization of thermal electron transport and the determination of heating by suprathermal electrons in laser driven solid targets are both issues of great importance to the current experiments being performed at the National Ignition Facility, which aims to achieve thermonuclear fusion ignition using lasers. Ionization, induced by electronic heat conduction, can cause the opacity of a material to drop significantly once bound-free photoionization is no longer energetically possible. We show that this drop in opacity enables measurements of the transmission of extreme ultraviolet (EUV) laser pulses at 13.9 nm to act as a signature of the heating of thin (50 nm) iron layers with a 50-nm thick parylene-N (CH) overlay irradiated by 35-fs pulses at irradiance 3×10(16) Wcm(-2). Comparing EUV transmission measurements at different times after irradiation to fluid code simulations shows that the target is instantaneously heated by hot electrons (with approximately 10% of the laser energy), followed by thermal conduction with a flux limiter of ≈0.05.

Laser Cooling for Heavy-Ion Fusion (HIF)

NASA Astrophysics Data System (ADS)

Ho, D. D.-M.; Brandon, S.; Lee, Y.

1997-05-01

A critical requirement for HIF is the ability to focus space-charge dominated beams onto a millimeter-size spot. However, chromatic aberration can result in a substantial fraction of the beam ions falling outside the spot radius. Because of the space-charge force, correcting the chromatic aberration using sextupoles is impractical. Success in laser cooling of low-current ion beams in storage rings leads us to explore the application of laser cooling to HIF. Basic scheme: After the beams have been accelerated to the desired energy by the recirculating induction linac, we let the beams coast around at constant energy. For efficient interaction between the laser and the beam ions, we use Ba+ beams. We use two lasers to pump the transitions in the Ba+ for generating the laser force FL. There is also an auxiliary force Fa, which is in the opposition direction of FL, provided by the induction cores. The momentum spread along the beam can be compressed by FL and Fa. We will present preliminary PIC simulations using the PIC code CONDOR. Potential difficulties caused by velocity space instabilities will be discussed.

Three-Dimensional Hydrodynamic Simulations of the Effects of Laser Imprint in OMEGA Implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Campbell, E. M.; Goncharov, V. N.; Regan, S. P.; Shvydky, A.; Schmitt, A. J.

2017-10-01

Illumination of direct-drive implosion targets by the OMEGA laser introduces large-amplitude broadband modulations in the absorbed energy from the largest (target size 900- μm) to smallest (speckle size 2- μm) spatial scales. These modulations ``imprint'' perturbations into a target that are amplified because of the secular and Rayleigh-Taylor growths during acceleration and deceleration of the target. The degradation of performance of room-temperature and cryogenic OMEGA implosions caused by these perturbations were simulated in three dimensions using the code ASTER. The highest-resolution simulations resolve perturbation modes as high as l 200 . The high modes l 50to 100 dominate in the perturbation spectrum during the linear growth, while the late-time nonlinear evolution results in domination of modes with l 30to 50 . Smoothing by spectral dispersion reduces the linear-phase mode amplitudes by a factor of 4 and results in substantial improvements in implosion performance that is in good agreement with measurements. The effects of imprint on implosion performance are compared with the effects of other implosion asymmetries, such as those induced because of laser beam imbalance, mistiming and mispointing, and target offset. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Cryogenic tritium-hydrogen-deuterium and deuterium-tritium layer implosions with high density carbon ablators in near-vacuum hohlraums

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meezan, N. B., E-mail: meezan1@llnl.gov; Hopkins, L. F. Berzak; Pape, S. Le

2015-06-15

High Density Carbon (or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a deuterium-tritium (DT) layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a tritium-hydrogen-deuterium (THD) layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape.more » Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 × 10{sup 15} neutrons, 40% of the 1D simulated yield.« less

Three-dimensional ordering of cold ion beams in a storage ring: A molecular-dynamics simulation study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuri, Yosuke, E-mail: yuri.yosuke@jaea.go.jp

Three-dimensional (3D) ordering of a charged-particle beams circulating in a storage ring is systematically studied with a molecular-dynamics simulation code. An ion beam can exhibit a 3D ordered configuration at ultralow temperature as a result of powerful 3D laser cooling. Various unique characteristics of the ordered beams, different from those of crystalline beams, are revealed in detail, such as the single-particle motion in the transverse and longitudinal directions, and the dependence of the tune depression and the Coulomb coupling constant on the operating points.

End-to-end plasma bubble PIC simulations on GPUs

NASA Astrophysics Data System (ADS)

Germaschewski, Kai; Fox, William; Matteucci, Jackson; Bhattacharjee, Amitava

2017-10-01

Accelerator technologies play a crucial role in eventually achieving exascale computing capabilities. The current and upcoming leadership machines at ORNL (Titan and Summit) employ Nvidia GPUs, which provide vast computational power but also need specifically adapted computational kernels to fully exploit them. In this work, we will show end-to-end particle-in-cell simulations of the formation, evolution and coalescence of laser-generated plasma bubbles. This work showcases the GPU capabilities of the PSC particle-in-cell code, which has been adapted for this problem to support particle injection, a heating operator and a collision operator on GPUs.

Proceedings of Symposium on Physics of Target Implosion and Pulsed Power Techniques Held in Yokohama, Japan on 30 September-1 October 1987

DTIC Science & Technology

1988-02-01

Japan. -- ,, mnm mmmm m m mil II m mlmmmm PREFACE A It is reported that by using the Nd glass laser, experiments of beam-target interaction are carried...Beam 8. 14.00-14.30 T. Ishimoto and T. Kato (Waseda Univ.) Electron Current Effect on Stability of Plasma Channel 9. 14.30-15.00 S. Kawata, M ...Matsumoto and Y. Masubuchi (Tech. Univ. Nagaoka) Numerical Simulation in LIB ICF 10. 15.00-15.30 J. M . Perlado (Univ. Politec. Madrid) Simulation Code for ICF

Observation of a Hydrodynamically Driven, Radiative Precursor Shock

NASA Astrophysics Data System (ADS)

Keiter, P. A.; Drake, R. P.; Perry, T. S.; Robey, H.; Remington, B. A.; Iglesias, C. A.; Turner, N.; Stone, J.; Knauer, J.

2001-10-01

Many astrophysical systems, such as supernova remnants and jets, produce radiative-precursor shock waves. In a radiative-precursor shock, radiation from the shock ionizes and heats the medium ahead of it. The simulation of such systems requires that one treat both the emission and the absorption of the radiation. An important goal of this effort is to produce an experiment that can be modeled by astrophysical codes without implementing laser absorption physics into an astrophysical code. We report here the first measurements of a radiative-precursor shock in such an experiment. The experimental design is based on a past experiment[1,2] that used the Nova laser facility to simulate young supernova remnants. The target consists of a 60 νm CH plastic plug followed by a 150 νm vacuum gap and 2 mm of SiO2 aerogel foam. For the experiment, the density of the components and the laser-irradiation conditions are chosen so that the driven shock will produce an observable radiative precursor. We observed the radiative-precursor by using absorption spectroscopy. By backlighting the silicate aerogel foam with a thulium backlighter, we were able to observe both the 1s-2p and 1s-3p lines. These observations will allow us to determine the temperature profile in the precursor. 1. R.P. Drake, et al, Phys. Rev. Lett. 81, 2068 (1998). 2. R.P. Drake, et al., Phys. Plasmas, 7, 2142 (2000) Work supported by the U.S. Department of Energy both directly and through the Lawrence Livermore National Laboratory

Relationship between symmetry and laser pulse shape in low-fill hohlraums at the National Ignition Facility

NASA Astrophysics Data System (ADS)

MacLaren, Steve; Zylstra, A. B.; Yi, A.; Kline, J. L.; Kyrala, G. A.; Kot, L. B.; Loomis, E. N.; Perry, T. S.; Shah, R. C.; Masse, L. P.; Ralph, J. E.; Khan, S. F.

2017-10-01

Typically in indirect-drive inertial confinement fusion (ICF) hohlraums cryogenic helium gas fill is used to impede the motion of the hohlraum wall plasma as it is driven by the laser pulse. A fill of 1 mg/cc He has been used to significantly suppress wall motion in ICF hohlraums at the National Ignition Facility (NIF); however, this level of fill also causes laser-plasma instabilities (LPI) which result in hot electrons, time-dependent symmetry swings and reduction in drive due to increased backscatter. There are currently no adequate models for these phenomena in codes used to simulate integrated ICF experiments. A better compromise is a fill in the range of 0.3 0.6 mg/cc, which has been shown to provide some reduction in wall motion without incurring significant LPI effects. The wall motion in these low-fill hohlraums and the resulting effect on symmetry due to absorption of the inner cone beams by the outer cone plasma can be simulated with some degree of accuracy with the hydrodynamics and inverse Bremsstrahlung models in ICF codes. We describe a series of beryllium capsule implosions in 0.3 mg/cc He fill hohlraums that illustrate the effect of pulse shape on implosion symmetry in the ``low-fill'' regime. In particular, we find the shape of the beginning or ``foot'' of the pulse has significant leverage over the final symmetry of the stagnated implosion. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strozzi, David J.; Perkins, L. J.; Marinak, M. M.

The effects of an imposed, axial magnetic fieldmore » $$B_{z0}$$ on hydrodynamics and energetic electrons in inertial confinement fusion indirect-drive hohlraums are studied. We present simulations from the radiation-hydrodynamics code HYDRA of a low-adiabat ignition design for the National Ignition Facility, with and without $$B_{z0}=70~\\text{T}$$. The field’s main hydrodynamic effect is to significantly reduce electron thermal conduction perpendicular to the field. This results in hotter and less dense plasma on the equator between the capsule and hohlraum wall. The inner laser beams experience less inverse bremsstrahlung absorption before reaching the wall. The X-ray drive is thus stronger from the equator with the imposed field. We study superthermal, or ‘hot’, electron dynamics with the particle-in-cell code ZUMA, using plasma conditions from HYDRA. During the early-time laser picket, hot electrons based on two-plasmon decay in the laser entrance hole (Regan et al., Phys. Plasmas, vol. 17(2), 2010, 020703) are guided to the capsule by a 70 T field. Twelve times more energy deposits in the deuterium–tritium fuel. For plasma conditions early in peak laser power, we present mono-energetic test-case studies with ZUMA as well as sources based on inner-beam stimulated Raman scattering. Furthermore, the effect of the field on deuterium–tritium deposition depends strongly on the source location, namely whether hot electrons are generated on field lines that connect to the capsule.« less

Heating in short-pulse laser-driven cone-capped wire targets

NASA Astrophysics Data System (ADS)

Mason, R. J.; Wei, M.; King, J.; Beg, F.; Stephens, R. B.

2007-11-01

The 2-D implicit hybrid simulation code e-PLAS has been used to study heating in cone-capped copper wire targets. The code e-PLAS tracks collisional particle-in-cell (PIC) electrons traversing background plasma of collisional Eulerian cold electron and ion fluids. It computes E- and B-fields by the Implicit Moment Method [1,2]. In recent experiments [3] at the Vulcan laser facility, sub- picosecond laser pulses at 1.06 μm, and 4.0 x 10^20 W/cm^2 intensity were focused into thin-walled (˜10 μm) cones attached to copper wires. The wire diameter was varied from 10-40 μm with a typical length of 1 mm. We characterize heating of the wires as a function of their diameters and length, and relate modifications of this heating to changes in the assumed laser-generated hot electron spectrum and directivity. As in recent nail experiments [4], the cones can serve as reservoirs for hot electrons, diverting them from passage down the wires. [1] R. J. Mason, and C. Cranfill, IEEE Trans. Plasma Sci. PS-14, 45 (1986). [2] R. J. Mason, J. Comp. Phys. 71, 429 (1987). [3] J. King et al., to be submitted to Phys. Rev. Lett.. [4] R. J. Mason, M. Wei, F. Beg, R. Stephens, and C. Snell, in Proc. of ICOPS07, Albuquerque, NM, June 17-22, 2007, Talk 7D4.

Evaluation of Thin Plate Hydrodynamic Stability through a Combined Numerical Modeling and Experimental Effort

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tentner, A.; Bojanowski, C.; Feldman, E.

An experimental and computational effort was undertaken in order to evaluate the capability of the fluid-structure interaction (FSI) simulation tools to describe the deflection of a Missouri University Research Reactor (MURR) fuel element plate redesigned for conversion to lowenriched uranium (LEU) fuel due to hydrodynamic forces. Experiments involving both flat plates and curved plates were conducted in a water flow test loop located at the University of Missouri (MU), at conditions and geometries that can be related to the MURR LEU fuel element. A wider channel gap on one side of the test plate, and a narrower on the othermore » represent the differences that could be encountered in a MURR element due to allowed fabrication variability. The difference in the channel gaps leads to a pressure differential across the plate, leading to plate deflection. The induced plate deflection the pressure difference induces in the plate was measured at specified locations using a laser measurement technique. High fidelity 3-D simulations of the experiments were performed at MU using the computational fluid dynamics code STAR-CCM+ coupled with the structural mechanics code ABAQUS. Independent simulations of the experiments were performed at Argonne National Laboratory (ANL) using the STAR-CCM+ code and its built-in structural mechanics solver. The simulation results obtained at MU and ANL were compared with the corresponding measured plate deflections.« less

Radial current high power dummy load for characterizing the high power laser triggered transformer-type accelerator.

PubMed

Yin, Yi; Zhong, Hui-Huang; Liu, Jin-Liang; Ren, He-Ming; Yang, Jian-Hua; Zhang, Xiao-Ping; Hong, Zhi-qiang

2010-09-01

A radial-current aqueous resistive solution load was applied to characterize a laser triggered transformer-type accelerator. The current direction in the dummy load is radial and is different from the traditional load in the axial. Therefore, this type of dummy load has smaller inductance and fast response characteristic. The load was designed to accommodate both the resistance requirement of accelerator and to allow optical access for the laser. Theoretical and numerical calculations of the load's inductance and capacitance are given. The equivalent circuit of the dummy load is calculated in theory and analyzed with a PSPICE code. The simulation results agree well with the theoretical analysis. At last, experiments of the dummy load applied to the high power spiral pulse forming line were performed; a quasisquare pulse voltage is obtained at the dummy load.

Amplifying modeling for broad bandwidth pulse in Nd:glass based on hybrid-broaden mechanism

NASA Astrophysics Data System (ADS)

Su, J.; Liu, L.; Luo, B.; Wang, W.; Jing, F.; Wei, X.; Zhang, X.

2008-05-01

In this paper, the cross relaxation time is proposed to combine the homogeneous and inhomogeneous broaden mechanism for broad bandwidth pulse amplification model. The corresponding velocity equation, which can describe the response of inverse population on upper and low energy level of gain media to different frequency of pulse, is also put forward. The gain saturation and energy relaxation effect are also included in the velocity equation. Code named CPAP has been developed to simulate the amplifying process of broad bandwidth pulse in multi-pass laser system. The amplifying capability of multi-pass laser system is evaluated and gain narrowing and temporal shape distortion are also investigated when bandwidth of pulse and cross relaxation time of gain media are different. Results can benefit the design of high-energy PW laser system in LFRC, CAEP.

Radial current high power dummy load for characterizing the high power laser triggered transformer-type accelerator

NASA Astrophysics Data System (ADS)

Yin, Yi; Zhong, Hui-Huang; Liu, Jin-Liang; Ren, He-Ming; Yang, Jian-Hua; Zhang, Xiao-Ping; Hong, Zhi-qiang

2010-09-01

A radial-current aqueous resistive solution load was applied to characterize a laser triggered transformer-type accelerator. The current direction in the dummy load is radial and is different from the traditional load in the axial. Therefore, this type of dummy load has smaller inductance and fast response characteristic. The load was designed to accommodate both the resistance requirement of accelerator and to allow optical access for the laser. Theoretical and numerical calculations of the load's inductance and capacitance are given. The equivalent circuit of the dummy load is calculated in theory and analyzed with a PSPICE code. The simulation results agree well with the theoretical analysis. At last, experiments of the dummy load applied to the high power spiral pulse forming line were performed; a quasisquare pulse voltage is obtained at the dummy load.

LANL compact laser pumping simulation. Final task report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, B.S.; White, J.

1987-09-28

Rockwell has been tasked with the objective of both qualitatively and quantitatively defining the performance of LANL Compact Laser coupling systems. The performance criteria of the system will be based upon the magnitude and uniformity of the energy distribution in the laser pumping rod. Once this is understood, it will then be possible to improve the device performance via changes in the system`s component parameters. For this study, the authors have chosen to use the Los Alamos Radiometry Code (LARC), which was previously developed by Rockwell. LARC, as an analysis tool, is well suited for this problem because the codemore » contains the needed photometric calculation capability and easily handles the three-dimensionality of the problem. Also, LARC`s internal graphics can provide very informative visual displays of the optical system.« less

Application of Plasma Waveguides to High Energy Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milchberg, Howard M

2013-03-30

The eventual success of laser-plasma based acceleration schemes for high-energy particle physics will require the focusing and stable guiding of short intense laser pulses in reproducible plasma channels. For this goal to be realized, many scientific issues need to be addressed. These issues include an understanding of the basic physics of, and an exploration of various schemes for, plasma channel formation. In addition, the coupling of intense laser pulses to these channels and the stable propagation of pulses in the channels require study. Finally, new theoretical and computational tools need to be developed to aid in the design and analysismore » of experiments and future accelerators. Here we propose a 3-year renewal of our combined theoretical and experimental program on the applications of plasma waveguides to high-energy accelerators. During the past grant period we have made a number of significant advances in the science of laser-plasma based acceleration. We pioneered the development of clustered gases as a new highly efficient medium for plasma channel formation. Our contributions here include theoretical and experimental studies of the physics of cluster ionization, heating, explosion, and channel formation. We have demonstrated for the first time the generation of and guiding in a corrugated plasma waveguide. The fine structure demonstrated in these guides is only possible with cluster jet heating by lasers. The corrugated guide is a slow wave structure operable at arbitrarily high laser intensities, allowing direct laser acceleration, a process we have explored in detail with simulations. The development of these guides opens the possibility of direct laser acceleration, a true miniature analogue of the SLAC RF-based accelerator. Our theoretical studies during this period have also contributed to the further development of the simulation codes, Wake and QuickPIC, which can be used for both laser driven and beam driven plasma based acceleration schemes. We will continue our development of advanced simulation tools by modifying the QuickPIC algorithm to allow for the simulation of plasma particle pick-up by the wake fields. We have also performed extensive simulations of plasma slow wave structures for efficient THz generation by guided laser beams or accelerated electron beams. We will pursue experimental studies of direct laser acceleration, and THz generation by two methods, ponderomotive-induced THz polarization, and THz radiation by laser accelerated electron beams. We also plan to study both conventional and corrugated plasma channels using our new 30 TW in our new lab facilities. We will investigate production of very long hydrogen plasma waveguides (5 cm). We will study guiding at increasing power levels through the onset of laser-induced cavitation (bubble regime) to assess the role played by the preformed channel. Experiments in direct acceleration will be performed, using laser plasma wakefields as the electron injector. Finally, we will use 2-colour ionization of gases as a high frequency THz source (<60 THz) in order for femtosecond measurements of low plasma densities in waveguides and beams.« less

Study of laser preheating dependence on laser wavelength and intensity for MagLIF

NASA Astrophysics Data System (ADS)

Wei, M. S.; Harvey-Thompson, A. J.; Glinsky, M.; Nagayama, T.; Weis, M.; Geissel, M.; Peterson, K.; Fooks, J.; Krauland, C.; Giraldez, E.; Davies, J.; Campbell, E. M.; Bahr, R.; Edgell, D.; Stoeckl, C.; Glebov, V.; Emig, J.; Heeter, R.; Strozzi, D.

2017-10-01

The magnetized liner inertial fusion (MagLIF) scheme requires preheating underdense fuel to 100's eV temperature by a TW-scale long pulse laser via collisional absorption. To better understand how laser preheat scales with laser wavelength and intensity as well as to provide data for code validation, we have conducted a well-characterized experiment on OMEGA to directly compare laser propagation, energy deposition and laser plasma instabilities (LPI) using 2 ω (527 nm) and 3 ω (351 nm) lasers with intensity in the range of (1-5)x1014 Wcm-2. The laser beam (1 - 1.5 ns square pulse) enters the gas-filled plastic liner though a 2-µm thick polyimide window to heat an underdense Ar-doped deuterium gas with electron density of 5.5% of critical density. Laser propagation and plasma temperature are diagnosed by time-resolved 2D x-ray images and Ar emission spectroscopy, respectively. LPI is monitored by backscattering and hard x-ray diagnostics. The 2 ω beam propagation shows a noticeable larger lateral spread than the 3 ω beam, indicating laser spray due to filamentation. LPI is observed to increase with laser intensity and the 2 ω beam produces more hot electrons compared with the 3 ω beam under similar conditions. Results will be compared with radiation hydrodynamic simulations. Work supported by the U.S. DOE ARPA-E and NNSA.

A tesselation-based model for intensity estimation and laser plasma interactions calculations in three dimensions

NASA Astrophysics Data System (ADS)

Colaïtis, A.; Chapman, T.; Strozzi, D.; Divol, L.; Michel, P.

2018-03-01

A three-dimensional laser propagation model for computation of laser-plasma interactions is presented. It is focused on indirect drive geometries in inertial confinement fusion and formulated for use at large temporal and spatial scales. A modified tesselation-based estimator and a relaxation scheme are used to estimate the intensity distribution in plasma from geometrical optics rays. Comparisons with reference solutions show that this approach is well-suited to reproduce realistic 3D intensity field distributions of beams smoothed by phase plates. It is shown that the method requires a reduced number of rays compared to traditional rigid-scale intensity estimation. Using this field estimator, we have implemented laser refraction, inverse-bremsstrahlung absorption, and steady-state crossed-beam energy transfer with a linear kinetic model in the numerical code Vampire. Probe beam amplification and laser spot shapes are compared with experimental results and pf3d paraxial simulations. These results are promising for the efficient and accurate computation of laser intensity distributions in holhraums, which is of importance for determining the capsule implosion shape and risks of laser-plasma instabilities such as hot electron generation and backscatter in multi-beam configurations.

Study of transport of laser-driven relativistic electrons in solid materials

NASA Astrophysics Data System (ADS)

Leblanc, Philippe

With the ultra intense lasers available today, it is possible to generate very hot electron beams in solid density materials. These intense laser-matter interactions result in many applications which include the generation of ultrashort secondary sources of particles and radiation such as ions, neutrons, positrons, x-rays, or even laser-driven hadron therapy. For these applications to become reality, a comprehensive understanding of laser-driven energy transport including hot electron generation through the various mechanisms of ionization, and their subsequent transport in solid density media is required. This study will focus on the characterization of electron transport effects in solid density targets using the state-of- the-art particle-in-cell code PICLS. A number of simulation results will be presented on the topics of ionization propagation in insulator glass targets, non-equilibrium ionization modeling featuring electron impact ionization, and electron beam guiding by the self-generated resistive magnetic field. An empirically derived scaling relation for the resistive magnetic in terms of the laser parameters and material properties is presented and used to derive a guiding condition. This condition may prove useful for the design of future laser-matter interaction experiments.

Handheld laser scanner automatic registration based on random coding

NASA Astrophysics Data System (ADS)

He, Lei; Yu, Chun-ping; Wang, Li

2011-06-01

Current research on Laser Scanner often focuses mainly on the static measurement. Little use has been made of dynamic measurement, that are appropriate for more problems and situations. In particular, traditional Laser Scanner must Keep stable to scan and measure coordinate transformation parameters between different station. In order to make the scanning measurement intelligently and rapidly, in this paper ,we developed a new registration algorithm for handleheld laser scanner based on the positon of target, which realize the dynamic measurement of handheld laser scanner without any more complex work. the double camera on laser scanner can take photograph of the artificial target points to get the three-dimensional coordinates, this points is designed by random coding. And then, a set of matched points is found from control points to realize the orientation of scanner by the least-square common points transformation. After that the double camera can directly measure the laser point cloud in the surface of object and get the point cloud data in an unified coordinate system. There are three major contributions in the paper. Firstly, a laser scanner based on binocular vision is designed with double camera and one laser head. By those, the real-time orientation of laser scanner is realized and the efficiency is improved. Secondly, the coding marker is introduced to solve the data matching, a random coding method is proposed. Compared with other coding methods,the marker with this method is simple to match and can avoid the shading for the object. Finally, a recognition method of coding maker is proposed, with the use of the distance recognition, it is more efficient. The method present here can be used widely in any measurement from small to huge obiect, such as vehicle, airplane which strengthen its intelligence and efficiency. The results of experiments and theory analzing demonstrate that proposed method could realize the dynamic measurement of handheld laser scanner. Theory analysis and experiment shows the method is reasonable and efficient.

Comparison of measured with calculated dose distribution from a 120-MeV electron beam from a laser-plasma accelerator.

PubMed

Lundh, O; Rechatin, C; Faure, J; Ben-Ismaïl, A; Lim, J; De Wagter, C; De Neve, W; Malka, V

2012-06-01

To evaluate the dose distribution of a 120-MeV laser-plasma accelerated electron beam which may be of potential interest for high-energy electron radiation therapy. In the interaction between an intense laser pulse and a helium gas jet, a well collimated electron beam with very high energy is produced. A secondary laser beam is used to optically control and to tune the electron beam energy and charge. The potential use of this beam for radiation treatment is evaluated experimentally by measurements of dose deposition in a polystyrene phantom. The results are compared to Monte Carlo simulations using the geant4 code. It has been shown that the laser-plasma accelerated electron beam can deliver a peak dose of more than 1 Gy at the entrance of the phantom in a single laser shot by direct irradiation, without the use of intermediate magnetic transport or focusing. The dose distribution is peaked on axis, with narrow lateral penumbra. Monte Carlo simulations of electron beam propagation and dose deposition indicate that the propagation of the intense electron beam (with large self-fields) can be described by standard models that exclude collective effects in the response of the material. The measurements show that the high-energy electron beams produced by an optically injected laser-plasma accelerator can deliver high enough dose at penetration depths of interest for electron beam radiotherapy of deep-seated tumors. Many engineering issues must be resolved before laser-accelerated electrons can be used for cancer therapy, but they also represent exciting challenges for future research. © 2012 American Association of Physicists in Medicine.

Towards Real Time Diagnostics of Hybrid Welding Laser/GMAW

DOE Office of Scientific and Technical Information (OSTI.GOV)

Timothy Mcjunkin; Dennis C. Kunerth; Corrie Nichol

2013-07-01

Methods are currently being developed towards a more robust system real time feedback in the high throughput process combining laser welding with gas metal arc welding. A combination of ultrasonic, eddy current, electronic monitoring, and visual techniques are being applied to the welding process. Initial simulation and bench top evaluation of proposed real time techniques on weld samples are presented along with the concepts to apply the techniques concurrently to the weld process. Consideration for the eventual code acceptance of the methods and system are also being researched as a component of this project. The goal is to detect defectsmore » or precursors to defects and correct when possible during the weld process.« less

Towards real time diagnostics of Hybrid Welding Laser/GMAW

DOE Office of Scientific and Technical Information (OSTI.GOV)

McJunkin, T. R.; Kunerth, D. C.; Nichol, C. I.

2014-02-18

Methods are currently being developed towards a more robust system real time feedback in the high throughput process combining laser welding with gas metal arc welding. A combination of ultrasonic, eddy current, electronic monitoring, and visual techniques are being applied to the welding process. Initial simulation and bench top evaluation of proposed real time techniques on weld samples are presented along with the concepts to apply the techniques concurrently to the weld process. Consideration for the eventual code acceptance of the methods and system are also being researched as a component of this project. The goal is to detect defectsmore » or precursors to defects and correct when possible during the weld process.« less

Towards real time diagnostics of Hybrid Welding Laser/GMAW

NASA Astrophysics Data System (ADS)

McJunkin, T. R.; Kunerth, D. C.; Nichol, C. I.; Todorov, E.; Levesque, S.

2014-02-01

Methods are currently being developed towards a more robust system real time feedback in the high throughput process combining laser welding with gas metal arc welding. A combination of ultrasonic, eddy current, electronic monitoring, and visual techniques are being applied to the welding process. Initial simulation and bench top evaluation of proposed real time techniques on weld samples are presented along with the concepts to apply the techniques concurrently to the weld process. Consideration for the eventual code acceptance of the methods and system are also being researched as a component of this project. The goal is to detect defects or precursors to defects and correct when possible during the weld process.

Estimation of Airborne Radioactivity Induced by 8-GeV-Class Electron LINAC Accelerator.

PubMed

Asano, Yoshihiro

2017-10-01

Airborne radioactivity induced by high-energy electrons from 6 to 10 GeV is estimated by using analytical methods and the Monte Carlo codes PHITS and FLUKA. Measurements using a gas monitor with a NaI(Tl) scintillator are carried out in air from a dump room at SACLA, an x-ray free-electron laser facility with 7.8-GeV electrons and are compared to the simulations.

A soft X-ray source based on a low divergence, high repetition rate ultraviolet laser

NASA Astrophysics Data System (ADS)

Crawford, E. A.; Hoffman, A. L.; Milroy, R. D.; Quimby, D. C.; Albrecht, G. F.

The CORK code is utilized to evaluate the applicability of low divergence ultraviolet lasers for efficient production of soft X-rays. The use of the axial hydrodynamic code wih one ozone radial expansion to estimate radial motion and laser energy is examined. The calculation of ionization levels of the plasma and radiation rates by employing the atomic physics and radiation model included in the CORK code is described. Computations using the hydrodynamic code to determine the effect of laser intensity, spot size, and wavelength on plasma electron temperature are provided. The X-ray conversion efficiencies of the lasers are analyzed. It is observed that for a 1 GW laser power the X-ray conversion efficiency is a function of spot size, only weakly dependent on pulse length for time scales exceeding 100 psec, and better conversion efficiencies are obtained at shorter wavelengths. It is concluded that these small lasers focused to 30 micron spot sizes and 10 to the 14th W/sq cm intensities are useful sources of 1-2 keV radiation.

Simulations of Converging Shock Collisions for Shock Ignition

NASA Astrophysics Data System (ADS)

Sauppe, Joshua; Dodd, Evan; Loomis, Eric

2016-10-01

Shock ignition (SI) has been proposed as an alternative to achieving high gain in inertial confinement fusion (ICF) targets. A central hot spot below the ignition threshold is created by an initial compression pulse, and a second laser pulse drives a strong converging shock into the fuel. The collision between the rebounding shock from the compression pulse and the converging shock results in amplification of the converging shock and increases the hot spot pressure above the ignition threshold. We investigate shock collision in SI drive schemes for cylindrical targets with a polystyrene foam interior using radiation-hydrodynamics simulations with the RAGE code. The configuration is similar to previous targets fielded on the Omega laser. The CH interior results in a lower convergence ratio and the cylindrical geometry facilitates visualization of the shock transit using an axial X-ray backlighter, both of which are important for comparison to potential experimental measurements. One-dimensional simulations are used to determine shock timing, and the effects of low mode asymmetries in 2D computations are also quantified. LA-UR-16-24773.

Simultaneous Laser Ranging and Communication from an Earth-Based Satellite Laser Ranging Station to the Lunar Reconnaissance Orbiter in Lunar Orbit

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Skillman, David R.; Hoffman, Evan D.; Mao, Dandan; McGarry, Jan F.; Neumann, Gregory A.; McIntire, Leva; Zellar, Ronald S.; Davidson, Frederic M.; Fong, Wai H.;

Method of laser beam coding for control systems

NASA Astrophysics Data System (ADS)

Pałys, Tomasz; Arciuch, Artur; Walczak, Andrzej; Murawski, Krzysztof

2017-08-01

The article presents the method of encoding a laser beam for control systems. The experiments were performed using a red laser emitting source with a wavelength of λ = 650 nm and a power of P ≍ 3 mW. The aim of the study was to develop methods of modulation and demodulation of the laser beam. Results of research, in which we determined the effect of selected camera parameters, such as image resolution, number of frames per second on the result of demodulation of optical signal, is also shown in the paper. The experiments showed that the adopted coding method provides sufficient information encoded in a single laser beam (36 codes with the effectiveness of decoding at 99.9%).

Three-dimensional modeling of direct-drive cryogenic implosions on OMEGA

DOE PAGES

Igumenshchev, I. V.; Goncharov, V. N.; Marshall, F. J.; ...

2016-05-04

The effects of large-scale (with Legendre modes ≲10) laser-imposed nonuniformities in direct-drive cryogenic implosions on the OMEGA laser system are investigated using three-dimension hydrodynamic simulations performed using a newly developed code ASTER. Sources of these nonuniformities include an illumination pattern produced by 60 OMEGA laser beams, capsule offsets (~10 to 20 μm), and imperfect pointing, energy balance, and timing of the beams (with typical σ rms ~10 μm, 10%, and 5 ps, respectively). Two implosion designs using 26-kJ triple-picket laser pulses were studied: a nominal design, in which a 880-μm-diameter capsule is illuminated by the same-diameter beams, and a “R75”more » design using a capsule of 900 μm in diameter and beams of 75% of this diameter. Simulations found that nonuniformities because of capsule offsets and beam imbalance have the largest effect on implosion performance. These nonuniformities lead to significant distortions of implosion cores resulting in an incomplete stagnation. The shape of distorted cores is well represented by neutron images, but loosely in x-rays. Simulated neutron spectra from perturbed implosions show large directional variations and up to ~ 2 keV variation of the hot spot temperature inferred from these spectra. The R75 design is more hydrodynamically efficient because of mitigation of crossed-beam energy transfer, but also suffers more from the nonuniformities. Furthermore, simulations predict a performance advantage of this design over the nominal design when the target offset and beam imbalance σ rms are reduced to less than 5 μm and 5%, respectively.« less

Three-dimensional modeling of direct-drive cryogenic implosions on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Igumenshchev, I. V.; Goncharov, V. N.; Marshall, F. J.

The effects of large-scale (with Legendre modes ≲10) laser-imposed nonuniformities in direct-drive cryogenic implosions on the OMEGA laser system are investigated using three-dimension hydrodynamic simulations performed using a newly developed code ASTER. Sources of these nonuniformities include an illumination pattern produced by 60 OMEGA laser beams, capsule offsets (~10 to 20 μm), and imperfect pointing, energy balance, and timing of the beams (with typical σ rms ~10 μm, 10%, and 5 ps, respectively). Two implosion designs using 26-kJ triple-picket laser pulses were studied: a nominal design, in which a 880-μm-diameter capsule is illuminated by the same-diameter beams, and a “R75”more » design using a capsule of 900 μm in diameter and beams of 75% of this diameter. Simulations found that nonuniformities because of capsule offsets and beam imbalance have the largest effect on implosion performance. These nonuniformities lead to significant distortions of implosion cores resulting in an incomplete stagnation. The shape of distorted cores is well represented by neutron images, but loosely in x-rays. Simulated neutron spectra from perturbed implosions show large directional variations and up to ~ 2 keV variation of the hot spot temperature inferred from these spectra. The R75 design is more hydrodynamically efficient because of mitigation of crossed-beam energy transfer, but also suffers more from the nonuniformities. Furthermore, simulations predict a performance advantage of this design over the nominal design when the target offset and beam imbalance σ rms are reduced to less than 5 μm and 5%, respectively.« less

Laser treatment of female stress urinary incontinence: optical, thermal, and tissue damage simulations

NASA Astrophysics Data System (ADS)

Hardy, Luke A.; Chang, Chun-Hung; Myers, Erinn M.; Kennelly, Michael J.; Fried, Nathaniel M.

2016-02-01

Treatment of female stress urinary incontinence (SUI) by laser thermal remodeling of subsurface tissues is studied. Light transport, heat transfer, and thermal damage simulations were performed for transvaginal and transurethral methods. Monte Carlo (MC) provided absorbed photon distributions in tissue layers (vaginal wall, endopelvic fascia, urethral wall). Optical properties (n,μa,μs,g) were assigned to each tissue at λ=1064 nm. A 5-mm-diameter laser beam and power of 5 W for 15 s was used, based on previous experiments. MC output was converted into absorbed energy, serving as input for ANSYS finite element heat transfer simulations of tissue temperatures over time. Convective heat transfer was simulated with contact cooling probe set at 0 °C. Thermal properties (κ,c,ρ) were assigned to each tissue layer. MATLAB code was used for Arrhenius integral thermal damage calculations. A temperature matrix was constructed from ANSYS output, and finite sum was incorporated to approximate Arrhenius integral calculations. Tissue damage properties (Ea,A) were used to compute Arrhenius sums. For the transvaginal approach, 37% of energy was absorbed in endopelvic fascia layer with 0.8% deposited beyond it. Peak temperature was 71°C, treatment zone was 0.8-mm-diameter, and almost all of 2.7-mm-thick vaginal wall was preserved. For transurethral approach, 18% energy was absorbed in endopelvic fascia with 0.3% deposited beyond it. Peak temperature was 80°C, treatment zone was 2.0-mm-diameter, and only 0.6 mm of 2.4-mm-thick urethral wall was preserved. A transvaginal approach is more feasible than transurethral approach for laser treatment of SUI.

Orestes Kinetics Model for the Electra KrF Laser

NASA Astrophysics Data System (ADS)

Giuliani, J. L.; Kepple, P.; Lehmberg, R. H.; Myers, M. C.; Sethian, J. D.; Petrov, G.; Wolford, M.; Hegeler, F.

2003-10-01

Orestes is a first principles simulation code for the electron deposition, plasma chemistry, laser transport, and amplified spontaneous emission (ASE) in an e-beam pumped KrF laser. Orestes has been benchmarked against results from Nike at NRL and the Keio laser facility. The modeling tasks are to support ongoing oscillator experiments on the Electra laser ( 500 J), to predict performance of Electra as an amplifier, and to develop scaling relations for larger systems such as envisioned for an inertial fusion energy power plant. In Orestes the energy deposition of the primary beam electrons is assumed to be spatially uniform, but the excitation and ionization of the Ar/Kr/F2 target gas by the secondary electrons is determined from the energy distribution function as calculated by a Boltzmann code. The subsequent plasma kinetics of 23 species subject to over 100 reactions is followed with 1-D spatial resolution along the lasing axis. In addition, the vibrational relaxation among excited electronic states of the KrF molecule are included in the kinetics since lasing at 248 nm can occur from several vibrational lines of the B state. Transport of the lasing photons is solved by the method of characteristics. The time dependent ASE is calculated in 3-D using a ``local look-back'' scheme with discrete ordinates and includes specular reflection off the side walls and rear mirror. Gain narrowing is treated by multi-frequency transport of the ASE. Calculations for the gain, saturation intensity, extraction efficiency, and laser output from the Orestes model will be presented and compared with available data from Electra operated as an oscillator. Potential implications for the difference in optimal F2 concentration will be discussed along with the effects of window transmissivity at 248 nm.

Hybridizing Gravitationl Waveforms of Inspiralling Binary Neutron Star Systems

NASA Astrophysics Data System (ADS)

Cullen, Torrey; LIGO Collaboration

2016-03-01

Gravitational waves are ripples in space and time and were predicted to be produced by astrophysical systems such as binary neutron stars by Albert Einstein. These are key targets for Laser Interferometer and Gravitational Wave Observatory (LIGO), which uses template waveforms to find weak signals. The simplified template models are known to break down at high frequency, so I wrote code that constructs hybrid waveforms from numerical simulations to accurately cover a large range of frequencies. These hybrid waveforms use Post Newtonian template models at low frequencies and numerical data from simulations at high frequencies. They are constructed by reading in existing Post Newtonian models with the same masses as simulated stars, reading in the numerical data from simulations, and finding the ideal frequency and alignment to ``stitch'' these waveforms together.

Lorentz boosted frame simulation technique in Particle-in-cell methods

NASA Astrophysics Data System (ADS)

Yu, Peicheng

In this dissertation, we systematically explore the use of a simulation method for modeling laser wakefield acceleration (LWFA) using the particle-in-cell (PIC) method, called the Lorentz boosted frame technique. In the lab frame the plasma length is typically four orders of magnitude larger than the laser pulse length. Using this technique, simulations are performed in a Lorentz boosted frame in which the plasma length, which is Lorentz contracted, and the laser length, which is Lorentz expanded, are now comparable. This technique has the potential to reduce the computational needs of a LWFA simulation by more than four orders of magnitude, and is useful if there is no or negligible reflection of the laser in the lab frame. To realize the potential of Lorentz boosted frame simulations for LWFA, the first obstacle to overcome is a robust and violent numerical instability, called the Numerical Cerenkov Instability (NCI), that leads to unphysical energy exchange between relativistically drifting particles and their radiation. This leads to unphysical noise that dwarfs the real physical processes. In this dissertation, we first present a theoretical analysis of this instability, and show that the NCI comes from the unphysical coupling of the electromagnetic (EM) modes and Langmuir modes (both main and aliasing) of the relativistically drifting plasma. We then discuss the methods to eliminate them. However, the use of FFTs can lead to parallel scalability issues when there are many more cells along the drifting direction than in the transverse direction(s). We then describe an algorithm that has the potential to address this issue by using a higher order finite difference operator for the derivative in the plasma drifting direction, while using the standard second order operators in the transverse direction(s). The NCI for this algorithm is analyzed, and it is shown that the NCI can be eliminated using the same strategies that were used for the hybrid FFT/Finite Difference solver. This scheme also requires a current correction and filtering which require FFTs. However, we show that in this case the FFTs can be done locally on each parallel partition. We also describe how the use of the hybrid FFT/Finite Difference or the hybrid higher order finite difference/second order finite difference methods permit combining the Lorentz boosted frame simulation technique with another "speed up" technique, called the quasi-3D algorithm, to gain unprecedented speed up for the LWFA simulations. In the quasi-3D algorithm the fields and currents are defined on an r--z PIC grid and expanded in azimuthal harmonics. The expansion is truncated with only a few modes so it has similar computational needs of a 2D r--z PIC code. We show that NCI has similar properties in r--z as in z-x slab geometry and show that the same strategies for eliminating the NCI in Cartesian geometry can be effective for the quasi-3D algorithm leading to the possibility of unprecedented speed up. We also describe a new code called UPIC-EMMA that is based on fully spectral (FFT) solver. The new code includes implementation of a moving antenna that can launch lasers in the boosted frame. We also describe how the new hybrid algorithms were implemented into OSIRIS. Examples of LWFA using the boosted frame using both UPIC-EMMA and OSIRIS are given, including the comparisons against the lab frame results. We also describe how to efficiently obtain the boosted frame simulations data that are needed to generate the transformed lab frame data, as well as how to use a moving window in the boosted frame. The NCI is also a major issue for modeling relativistic shocks with PIC algorithm. In relativistic shock simulations two counter-propagating plasmas drifting at relativistic speeds are colliding against each other. We show that the strategies for eliminating the NCI developed in this dissertation are enabling such simulations being run for much longer simulation times, which should open a path for major advances in relativistic shock research. (Abstract shortened by ProQuest.).

3D broadband Bubbles Dynamics for the imprinted ablative Rayleigh-Taylor Instability

NASA Astrophysics Data System (ADS)

Casner, Alexis; Khan, S.; Mailliet, C.; Martinez, D.; Izumi, N.; Le Bel, E.; Remington, B. A.; Masse, L.; Smalyuk, V. A.

2017-10-01

We report on highly nonlinear ablative Rayleigh-Taylor growth measurements of 3D laser imprinted modulations. These experiments are part of the Discovery Science Program on NIF. Planar plastic samples were irradiated by 450 kJ of 3w laser light and the growth of 3D laser imprinted modulations is quantified through face-on radiography. The initial seed of the imprinted RTI is imposed by one beam focused in advance (-300 ps) without any optical smoothing (no CPP, no SSD). For the first time four generations of bubbles were created as larger bubbles overtake and merge with smaller bubbles because of the unprecedented long laser drive (30 ns). The experimental data, analyzed both in real and Fourier space, are compared with classical bubble-merger models, as well as recent theory and simulations predicting 3D bubbles reacceleration due to vorticity accumulation caused by mass ablation. These experiments are of crucial importance for benchmarking 2D and 3D radiation hydrodynamics code for Inertial Confinement Fusion.

Detailed energy distributions in laser-produced plasmas of solid gold and foam gold planar targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Yunsong; Department of Engineering Physics, Tsinghua University, Beijing 100084; Zhang, Lu

Foam gold was proposed to increase the laser to x-ray conversion efficiency due to its important applications. To understand the mechanism of x-ray enhancement, the detailed energy distributions and plasma profiles for laser-irradiated solid gold and foam gold targets were studied comparatively by hydrodynamic simulations using the code Multi-1D. It is confirmed that the radiation heat wave is subsonic for the normal solid gold target, while supersonic for the foam gold target. The shock wave, which is behind the supersonic radiation heat wave for the foam gold target, generates a plasma temperature gradient with high temperature near the shock wavemore » front to produce an additional net outward radiation for enhancement of the x-ray emission. Much larger inward plasma velocity is also driven by the shock wave as an initial plasma velocity for the laser deposition and electron thermal conduct zone, which decreases the expanding plasma kinetic energy loss and helps to increase the x-ray radiation.« less

Comparison of two- and three-dimensional flow computations with laser anemometer measurements in a transonic compressor rotor

NASA Technical Reports Server (NTRS)

Chima, R. V.; Strazisar, A. J.

1982-01-01

Two and three dimensional inviscid solutions for the flow in a transonic axial compressor rotor at design speed are compared with probe and laser anemometers measurements at near-stall and maximum-flow operating points. Experimental details of the laser anemometer system and computational details of the two dimensional axisymmetric code and three dimensional Euler code are described. Comparisons are made between relative Mach number and flow angle contours, shock location, and shock strength. A procedure for using an efficient axisymmetric code to generate downstream pressure input for computationally expensive Euler codes is discussed. A film supplement shows the calculations of the two operating points with the time-marching Euler code.

Laser-driven dielectric electron accelerator for radiobiology researches

NASA Astrophysics Data System (ADS)

Koyama, Kazuyoshi; Matsumura, Yosuke; Uesaka, Mitsuru; Yoshida, Mitsuhiro; Natsui, Takuya; Aimierding, Aimidula

2013-05-01

In order to estimate the health risk associated with a low dose radiation, the fundamental process of the radiation effects in a living cell must be understood. It is desired that an electron bunch or photon pulse precisely knock a cell nucleus and DNA. The required electron energy and electronic charge of the bunch are several tens keV to 1 MeV and 0.1 fC to 1 fC, respectively. The smaller beam size than micron is better for the precise observation. Since the laser-driven dielectric electron accelerator seems to suite for the compact micro-beam source, a phase-modulation-masked-type laser-driven dielectric accelerator was studied. Although the preliminary analysis made a conclusion that a grating period and an electron speed must satisfy the matching condition of LG/λ = v/c, a deformation of a wavefront in a pillar of the grating relaxed the matching condition and enabled the slow electron to be accelerated. The simulation results by using the free FDTD code, Meep, showed that the low energy electron of 20 keV felt the acceleration field strength of 20 MV/m and gradually felt higher field as the speed was increased. Finally the ultra relativistic electron felt the field strength of 600 MV/m. The Meep code also showed that a length of the accelerator to get energy of 1 MeV was 3.8 mm, the required laser power and energy were 11 GW and 350 mJ, respectively. Restrictions on the laser was eased by adopting sequential laser pulses. If the accelerator is illuminated by sequential N pulses, the pulse power, pulse width and the pulse energy are reduced to 1/N, 1/N and 1/N2, respectively. The required laser power per pulse is estimated to be 2.2 GW when ten pairs of sequential laser pulse is irradiated.

Modeling of laser induced air plasma and shock wave dynamics using 2D-hydrodynamic simulations

NASA Astrophysics Data System (ADS)

Paturi, Prem Kiran; S, Sai Shiva; Chelikani, Leela; Ikkurthi, Venkata Ramana; C. D., Sijoy; Chaturvedi, Shashank; Acrhem, University Of Hyderabad Team; Computational Analysis Division, Bhabha Atomic Research Centre, Visakhapatnam Team

2017-06-01

The laser induced air plasma dynamics and the SW evolution modeled using the two dimensional hydrodynamic code by considering two different EOS: ideal gas EOS with charge state effects taken into consideration and Chemical Equilibrium applications (CEA) EOS considering the chemical kinetics of different species will be presented. The inverse bremsstrahlung absorption process due to electron-ion and electron-neutrals is considered for the laser-air interaction process for both the models. The numerical results obtained with the two models were compared with that of the experimental observations over the time scales of 200 - 4000 ns at an input laser intensity of 2.3 ×1010 W/cm2. The comparison shows that the plasma and shock dynamics differ significantly for two EOS considered. With the ideas gas EOS the asymmetric expansion and the subsequent plasma dynamics have been well reproduced as observed in the experiments, whereas with the CEA model these processes were not reproduced due to the laser energy absorption occurring mostly at the focal volume. ACRHEM team thank DRDO, India for funding.

Modulating laser intensity profile ellipticity for microstructural control during metal additive manufacturing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roehling, Tien T.; Wu, Sheldon S. Q.; Khairallah, Saad A.

Additively manufactured (AM) metals are often highly textured, containing large columnar grains that initiate epitaxially under steep temperature gradients and rapid solidification conditions. These unique microstructures partially account for the massive property disparity existing between AM and conventionally processed alloys. Although equiaxed grains are desirable for isotropic mechanical behavior, the columnar-to-equiaxed transition remains difficult to predict for conventional solidification processes, and much more so for AM. In this study, the effects of laser intensity profile ellipticity on melt track macrostructures and microstructures were studied in 316L stainless steel. Experimental results were supported by temperature gradients and melt velocities simulated usingmore » the ALE3D multi-physics code. As a general trend, columnar grains preferentially formed with increasing laser power and scan speed for all beam profiles. However, when conduction mode laser heating occurs, scan parameters that result in coarse columnar microstructures using Gaussian profiles produce equiaxed or mixed equiaxed-columnar microstructures using elliptical profiles. Furthermore, by modulating spatial laser intensity profiles on the fly, site-specific microstructures and properties can be directly engineered into additively manufactured parts.« less

Modulating laser intensity profile ellipticity for microstructural control during metal additive manufacturing

DOE PAGES

Roehling, Tien T.; Wu, Sheldon S. Q.; Khairallah, Saad A.; ...

2017-02-12

Additively manufactured (AM) metals are often highly textured, containing large columnar grains that initiate epitaxially under steep temperature gradients and rapid solidification conditions. These unique microstructures partially account for the massive property disparity existing between AM and conventionally processed alloys. Although equiaxed grains are desirable for isotropic mechanical behavior, the columnar-to-equiaxed transition remains difficult to predict for conventional solidification processes, and much more so for AM. In this study, the effects of laser intensity profile ellipticity on melt track macrostructures and microstructures were studied in 316L stainless steel. Experimental results were supported by temperature gradients and melt velocities simulated usingmore » the ALE3D multi-physics code. As a general trend, columnar grains preferentially formed with increasing laser power and scan speed for all beam profiles. However, when conduction mode laser heating occurs, scan parameters that result in coarse columnar microstructures using Gaussian profiles produce equiaxed or mixed equiaxed-columnar microstructures using elliptical profiles. Furthermore, by modulating spatial laser intensity profiles on the fly, site-specific microstructures and properties can be directly engineered into additively manufactured parts.« less

Thermo-elasto-plastic simulations of femtosecond laser-induced structural modifications: Application to cavity formation in fused silica

NASA Astrophysics Data System (ADS)

Beuton, Romain; Chimier, Benoît; Breil, Jérôme; Hébert, David; Maire, Pierre-Henri; Duchateau, Guillaume

2017-11-01

The absorbed laser energy of a femtosecond laser pulse in a transparent material induces a warm dense matter region relaxation of which may lead to structural modifications in the surrounding cold matter. The modeling of the thermo-elasto-plastic material response is addressed to predict such modifications. It has been developed in a 2D plane geometry and implemented in a hydrodynamic Lagrangian code. The particular case of a tightly focused laser beam in the bulk of fused silica is considered as a first application of the proposed general model. It is shown that the warm dense matter relaxation, influenced by the elasto-plastic behavior of the surrounding cold matter, generates both strong shock and rarefaction waves. Permanent deformations appear in the surrounding solid matter if the induced stress becomes larger than the yield strength. This interaction results in the formation of a sub-micrometric cavity surrounded by an overdense area. This approach also allows one to predict regions where cracks may form. The present modeling can be used to design nanostructures induced by short laser pulses.

Partially coherent X-ray wavefront propagation simulations including grazing-incidence focusing optics.

PubMed

Canestrari, Niccolo; Chubar, Oleg; Reininger, Ruben

2014-09-01

X-ray beamlines in modern synchrotron radiation sources make extensive use of grazing-incidence reflective optics, in particular Kirkpatrick-Baez elliptical mirror systems. These systems can focus the incoming X-rays down to nanometer-scale spot sizes while maintaining relatively large acceptance apertures and high flux in the focused radiation spots. In low-emittance storage rings and in free-electron lasers such systems are used with partially or even nearly fully coherent X-ray beams and often target diffraction-limited resolution. Therefore, their accurate simulation and modeling has to be performed within the framework of wave optics. Here the implementation and benchmarking of a wave-optics method for the simulation of grazing-incidence mirrors based on the local stationary-phase approximation or, in other words, the local propagation of the radiation electric field along geometrical rays, is described. The proposed method is CPU-efficient and fully compatible with the numerical methods of Fourier optics. It has been implemented in the Synchrotron Radiation Workshop (SRW) computer code and extensively tested against the geometrical ray-tracing code SHADOW. The test simulations have been performed for cases without and with diffraction at mirror apertures, including cases where the grazing-incidence mirrors can be hardly approximated by ideal lenses. Good agreement between the SRW and SHADOW simulation results is observed in the cases without diffraction. The differences between the simulation results obtained by the two codes in diffraction-dominated cases for illumination with fully or partially coherent radiation are analyzed and interpreted. The application of the new method for the simulation of wavefront propagation through a high-resolution X-ray microspectroscopy beamline at the National Synchrotron Light Source II (Brookhaven National Laboratory, USA) is demonstrated.

pF3D Simulations of Large Outer-Beam Brillouin Scattering from NIF Rugby Hohlraums

NASA Astrophysics Data System (ADS)

Langer, Steven; Strozzi, David; Chapman, Thomas; Amendt, Peter

2015-11-01

We assess the cause of large outer-beam stimulated Brillouin scattering (SBS) in a NIF shot with a rugby-shaped hohlraum, which has less wall surface loss and thus higher x-ray drive than a cylindrical hohlraum of the same radius. This shot differed from a prior rugby shot with low SBS in three ways: outer beam pointing, split-pointing of the four beams within each outer-beam quadruplet, and a small amount of neon added to the hohlraum helium fill gas. We use pF3D, a massively-parallel, paraxial-envelope laser plasma interaction code, with plasma profiles from the radiation-hydrodynamics code Lasnex. We determine which change between the two shots increased the SBS by adding them one at a time to the simulations. We compare the simulations to experimental data for total SBS power, its spatial distribution at the lens, and the SBS spectrum. For each shot, we use profiles from Lasnex simulations with and without a model for mix at the hohlraum wall-gas interface. Work performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344. Release number LLNL-ABS-674893.

DRACO development for 3D simulations

NASA Astrophysics Data System (ADS)

Fatenejad, Milad; Moses, Gregory

2006-10-01

The DRACO (r-z) lagrangian radiation-hydrodynamics laser fusion simulation code is being extended to model 3D hydrodynamics in (x-y-z) coordinates with hexahedral cells on a structured grid. The equation of motion is solved with a lagrangian update with optional rezoning. The fluid equations are solved using an explicit scheme based on (Schulz, 1964) while the SALE-3D algorithm (Amsden, 1981) is used as a template for computing cell volumes and other quantities. A second order rezoner has been added which uses linear interpolation of the underlying continuous functions to preserve accuracy (Van Leer, 1976). Artificial restoring force terms and smoothing algorithms are used to avoid grid distortion in high aspect ratio cells. These include alternate node couplers along with a rotational restoring force based on the Tensor Code (Maenchen, 1964). Electron and ion thermal conduction is modeled using an extension of Kershaw's method (Kershaw, 1981) to 3D geometry. Test problem simulations will be presented to demonstrate the applicability of this new version of DRACO to the study of fluid instabilities in three dimensions.

Towards robust algorithms for current deposition and dynamic load-balancing in a GPU particle in cell code

NASA Astrophysics Data System (ADS)

Rossi, Francesco; Londrillo, Pasquale; Sgattoni, Andrea; Sinigardi, Stefano; Turchetti, Giorgio

2012-12-01

We present `jasmine', an implementation of a fully relativistic, 3D, electromagnetic Particle-In-Cell (PIC) code, capable of running simulations in various laser plasma acceleration regimes on Graphics-Processing-Units (GPUs) HPC clusters. Standard energy/charge preserving FDTD-based algorithms have been implemented using double precision and quadratic (or arbitrary sized) shape functions for the particle weighting. When porting a PIC scheme to the GPU architecture (or, in general, a shared memory environment), the particle-to-grid operations (e.g. the evaluation of the current density) require special care to avoid memory inconsistencies and conflicts. Here we present a robust implementation of this operation that is efficient for any number of particles per cell and particle shape function order. Our algorithm exploits the exposed GPU memory hierarchy and avoids the use of atomic operations, which can hurt performance especially when many particles lay on the same cell. We show the code multi-GPU scalability results and present a dynamic load-balancing algorithm. The code is written using a python-based C++ meta-programming technique which translates in a high level of modularity and allows for easy performance tuning and simple extension of the core algorithms to various simulation schemes.

LLE Review Quarterly Report (January-March 1999). Volume 78

DOE Office of Scientific and Technical Information (OSTI.GOV)

Regan, Sean P.

1999-03-01

This volume of the LLE Review, covering the period January-March 1999, features two articles concerning issues relevant to 2-D SSD laser-beam smoothing on OMEGA. In the first article J. D. Zuegel and J. A. Marozas present the design of an efficient, bulk phase modulator operating at approximately 10.5 GHz, which can produce substantial phase-modulated bandwidth with modest microwave drive power. This modulator is the cornerstone of the 1-THz UV bandwidth operation planned for OMEGA this year. In the second article J. A. Marozas and J. H. Kelly describe a recently developed code -- Waasese -- that simulates the collective behaviormore » of the optical components in the SSD driver line. The measurable signatures predicted by the code greatly enhance the diagnostic capability of the SSD driver line. Other articles in this volume are titled: Hollow-Shell Implosion Studies on the 60-Beam, UC OMEGA Laser System; Simultaneous Measurements of Fuel Areal Density, Shell Areal Density, and Fuel Temperature in D 3He-Filled Imploding Capsules; The Design of Optical Pulse Shapes with an Aperture-Coupled-Stripline Pulse-Shaping System; Measurement Technique for Characterization of Rapidly Time- and Frequency-Varying Electronic Devices; and, Damage to Fused-Silica, Spatial-Filter Lenses on the OMEGA Laser System.« less

Does laser-driven heat front propagation depend on material microstructure?

NASA Astrophysics Data System (ADS)

Colvin, J. D.; Matsukuma, H.; Fournier, K. B.; Yoga, A.; Kemp, G. E.; Tanaka, N.; Zhang, Z.; Kota, K.; Tosaki, S.; Ikenouchi, T.; Nishimura, H.

2016-10-01

We showed earlier that the laser-driven heat front propagation velocity in low-density Ti-silica aerogel and TiO2 foam targets was slower than that simulated with a 2D radiation-hydrodynamics code incorporating an atomic kinetics model in non-LTE and assuming initially homogeneous material. Some theoretical models suggest that the heat front is slowed over what it would be in a homogeneous medium by the microstructure of the foam. In order to test this hypothesis we designed and conducted a comparison experiment on the GEKKO laser to measure heat front propagation velocity in two targets, one an Ar/CO2 gas mixture and the other a TiO2 foam, that had identical initial densities and average ionization states. We found that the heat front traveled about ten times faster in the gas than in the foam. We present the details of the experiment design and a comparison of the data with the simulations. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract No. DE-AC52-07NA27344, and the joint research project of ILE Osaka U. (contract Nos. 2014A1-04 and 2015A1-02).

LIAD-fs scheme for studies of ultrafast laser interactions with gas phase biomolecules.

PubMed

Calvert, C R; Belshaw, L; Duffy, M J; Kelly, O; King, R B; Smyth, A G; Kelly, T J; Costello, J T; Timson, D J; Bryan, W A; Kierspel, T; Rice, P; Turcu, I C E; Cacho, C M; Springate, E; Williams, I D; Greenwood, J B

2012-05-14

Laser induced acoustic desorption (LIAD) has been used for the first time to study the parent ion production and fragmentation mechanisms of a biological molecule in an intense femtosecond (fs) laser field. The photoacoustic shock wave generated in the analyte substrate (thin Ta foil) has been simulated using the hydrodynamic HYADES code, and the full LIAD process has been experimentally characterised as a function of the desorption UV-laser pulse parameters. Observed neutral plumes of densities >10(9) cm(-3) which are free from solvent or matrix contamination demonstrate the suitability and potential of the source for studying ultrafast dynamics in the gas phase using fs laser pulses. Results obtained with phenylalanine show that through manipulation of fundamental femtosecond laser parameters (such as pulse length, intensity and wavelength), energy deposition within the molecule can be controlled to allow enhancement of parent ion production or generation of characteristic fragmentation patterns. In particular by reducing the pulse length to a timescale equivalent to the fastest vibrational periods in the molecule, we demonstrate how fragmentation of the molecule can be minimised whilst maintaining a high ionisation efficiency. This journal is © the Owner Societies 2012

Optical Analysis of Grazing Incidence Ring Resonators for Free-Electron Lasers

NASA Astrophysics Data System (ADS)

Gabardi, David Richard

1990-08-01

The design of resonators for free-electron lasers (FELs) which are to operate in the soft x-ray/vacuum ultraviolet (XUV) region of the spectrum is complicated by the fact that, in this wavelength regime, normal incidence mirrors, which would otherwise be used for the construction of the resonators, generally have insufficient reflectivities for this purpose. However, the use of grazing incidence mirrors in XUV resonators offers the possibility of (1) providing sufficient reflectivity, (2) a lessening of the mirrors' thermal loads due to the projection of the laser beam onto an oblique surface, and (3) the preservation of the FEL's tunability. In this work, the behavior of resonators employing grazing incidence mirrors in ring type configurations is explored. In particular, two designs, each utilizing four off-axis conic mirrors and a number of flats, are examined. In order to specify the location, orientation, and surface parameters for the mirrors in these resonators, a design algorithm has been developed based upon the properties of Gaussian beam propagation. Two computer simulation methods are used to perform a vacuum stability analysis of the two resonator designs. The first method uses paraxial ray trace techniques with the resonators' thin lens analogues while the second uses the diffraction-based computer simulation code GLAD (General Laser Analysis and Design). The effects of mirror tilts and deviations in the mirror surface parameters are investigated for a number of resonators designed to propagate laser beams of various Rayleigh ranges. It will be shown that resonator stability decreases as the laser wavelength for which the resonator was designed is made smaller. In addition, resonator stability will also be seen to decrease as the amount of magnification the laser beam receives as it travels around the resonator is increased.

Maximum current density and beam brightness achievable by laser-driven electron sources

NASA Astrophysics Data System (ADS)

Filippetto, D.; Musumeci, P.; Zolotorev, M.; Stupakov, G.

2014-02-01

This paper discusses the extension to different electron beam aspect ratio of the Child-Langmuir law for the maximum achievable current density in electron guns. Using a simple model, we derive quantitative formulas in good agreement with simulation codes. The new scaling laws for the peak current density of temporally long and transversely narrow initial beam distributions can be used to estimate the maximum beam brightness and suggest new paths for injector optimization.

Photovoltaic conversion of laser power to electrical power

NASA Technical Reports Server (NTRS)

Walker, G. H.; Heinbockel, J. H.

1986-01-01

Photovoltaic laser to electric converters are attractive for use with a space-based laser power station. This paper presents the results of modeling studies for a silicon vertical junction converter used with a Nd laser. A computer code was developed for the model and this code was used to conduct a parametric study for a Si vertical junction converter consisting of one p-n junction irradiated with a Nd laser. These calculations predict an efficiency over 50 percent for an optimized converter.

Assessment of the prevailing physics codes: LEOPARD, LASER, and EPRI-CELL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lan, J.S.

1981-01-01

In order to analyze core performance and fuel management, it is necessary to verify reactor physics codes in great detail. This kind of work not only serves the purpose of understanding and controlling the characteristics of each code, but also ensures the reliability as codes continually change due to constant modifications and machine transfers. This paper will present the results of a comprehensive verification of three code packages - LEOPARD, LASER, and EPRI-CELL.

Modelling debris and shrapnel generation in inertial confinement fusion experiments

DOE PAGES

Eder, D. C.; Fisher, A. C.; Koniges, A. E.; ...

2013-10-24

Modelling and mitigation of damage are crucial for safe and economical operation of high-power laser facilities. Experiments at the National Ignition Facility use a variety of targets with a range of laser energies spanning more than two orders of magnitude (~14 kJ to ~1.9 MJ). Low-energy inertial confinement fusion experiments are used to study early-time x-ray load symmetry on the capsule, shock timing, and other physics issues. For these experiments, a significant portion of the target is not completely vaporized and late-time (hundreds of ns) simulations are required to study the generation of debris and shrapnel from these targets. Damagemore » to optics and diagnostics from shrapnel is a major concern for low-energy experiments. Here, we provide the first full-target simulations of entire cryogenic targets, including the Al thermal mechanical package and Si cooling rings. We use a 3D multi-physics multi-material hydrodynamics code, ALE-AMR, for these late-time simulations. The mass, velocity, and spatial distribution of shrapnel are calculated for three experiments with laser energies ranging from 14 to 250 kJ. We calculate damage risk to optics and diagnostics for these three experiments. For the lowest energy re-emit experiment, we provide a detailed analysis of the effects of shrapnel impacts on optics and diagnostics and compare with observations of damage sites.« less

Computer modeling of pulsed CO2 lasers for lidar applications

NASA Technical Reports Server (NTRS)

Spiers, Gary D.

1993-01-01

The object of this effort is to develop code to enable the accurate prediction of the performance of pulsed transversely excited (TE) CO2 lasers prior to their construction. This is of particular benefit to the NASA Laser Atmospheric Wind Sounder (LAWS) project. A benefit of the completed code is that although developed specifically for the pulsed CO2 laser much of the code can be modified to model other laser systems of interest to the lidar community. A Boltzmann equation solver has been developed which enables the electron excitation rates for the vibrational levels of CO2 and N2, together with the electron ionization and attachment coefficients to be determined for any CO2 laser gas mixture consisting of a combination of CO2, N2, CO, He and CO. The validity of the model has been verified by comparison with published material. The results from the Boltzmann equation solver have been used as input to the laser kinetics code which is currently under development. A numerical code to model the laser induced medium perturbation (LIMP) arising from the relaxation of the lower laser level has been developed and used to determine the effect of LIMP on the frequency spectrum of the LAWS laser output pulse. The enclosed figures show representative results for a laser operating at 0.5 atm. with a discharge cross-section of 4.5 cm to produce a 20 J pulse with aFWHM of 3.1 microns. The first four plots show the temporal evolution of the laser pulse power, energy evolution, LIMP frequency chirp and electric field magnitude. The electric field magnitude is taken by beating the calculated complex electric field and beating it with a local oscillator signal. The remaining two figures show the power spectrum and energy distribution in the pulse as a function of the varying pulse frequency. The LIMP theory has been compared with experimental data from the NOAA Windvan Lidar and has been found to be in good agreement.

Post-acceleration of laser driven protons with a compact high field linac

NASA Astrophysics Data System (ADS)

Sinigardi, Stefano; Londrillo, Pasquale; Rossi, Francesco; Turchetti, Giorgio; Bolton, Paul R.

2013-05-01

We present a start-to-end 3D numerical simulation of a hybrid scheme for the acceleration of protons. The scheme is based on a first stage laser acceleration, followed by a transport line with a solenoid or a multiplet of quadrupoles, and then a post-acceleration section in a compact linac. Our simulations show that from a laser accelerated proton bunch with energy selection at ~ 30MeV, it is possible to obtain a high quality monochromatic beam of 60MeV with intensity at the threshold of interest for medical use. In the present day experiments using solid targets, the TNSA mechanism describes accelerated bunches with an exponential energy spectrum up to a cut-off value typically below ~ 60MeV and wide angular distribution. At the cut-off energy, the number of protons to be collimated and post-accelerated in a hybrid scheme are still too low. We investigate laser-plasma acceleration to improve the quality and number of the injected protons at ~ 30MeV in order to assure efficient post-acceleration in the hybrid scheme. The results are obtained with 3D PIC simulations using a code where optical acceleration with over-dense targets, transport and post-acceleration in a linac can all be investigated in an integrated framework. The high intensity experiments at Nara are taken as a reference benchmarks for our virtual laboratory. If experimentally confirmed, a hybrid scheme could be the core of a medium sized infrastructure for medical research, capable of producing protons for therapy and x-rays for diagnosis, which complements the development of all optical systems.

Simulation of deleterious processes in a static-cell diode pumped alkali laser

NASA Astrophysics Data System (ADS)

Oliker, Benjamin Q.; Haiducek, John D.; Hostutler, David A.; Pitz, Greg A.; Rudolph, Wolfgang; Madden, Timothy J.

2014-02-01

The complex interactions in a diode pumped alkali laser (DPAL) gain cell provide opportunities for multiple deleterious processes to occur. Effects that may be attributable to deleterious processes have been observed experimentally in a cesium static-cell DPAL at the United States Air Force Academy [B.V. Zhdanov, J. Sell, R.J. Knize, "Multiple laser diode array pumped Cs laser with 48 W output power," Electronics Letters, 44, 9 (2008)]. The power output in the experiment was seen to go through a "roll-over"; the maximum power output was obtained with about 70 W of pump power, then power output decreased as the pump power was increased beyond this point. Research to determine the deleterious processes that caused this result has been done at the Air Force Research Laboratory utilizing physically detailed simulation. The simulations utilized coupled computational fluid dynamics (CFD) and optics solvers, which were three-dimensional and time-dependent. The CFD code used a cell-centered, conservative, finite-volume discretization of the integral form of the Navier-Stokes equations. It included thermal energy transport and mass conservation, which accounted for chemical reactions and state kinetics. Optical models included pumping, lasing, and fluorescence. The deleterious effects investigated were: alkali number density decrease in high temperature regions, convective flow, pressure broadening and shifting of the absorption lineshape including hyperfine structure, radiative decay, quenching, energy pooling, off-resonant absorption, Penning ionization, photoionization, radiative recombination, three-body recombination due to free electron and buffer gas collisions, ambipolar diffusion, thermal aberration, dissociative recombination, multi-photon ionization, alkali-hydrocarbon reactions, and electron impact ionization.

Imposed magnetic field and hot electron propagation in inertial fusion hohlraums

DOE PAGES

Strozzi, David J.; Perkins, L. J.; Marinak, M. M.; ...

2015-12-02

The effects of an imposed, axial magnetic fieldmore » $$B_{z0}$$ on hydrodynamics and energetic electrons in inertial confinement fusion indirect-drive hohlraums are studied. We present simulations from the radiation-hydrodynamics code HYDRA of a low-adiabat ignition design for the National Ignition Facility, with and without $$B_{z0}=70~\\text{T}$$. The field’s main hydrodynamic effect is to significantly reduce electron thermal conduction perpendicular to the field. This results in hotter and less dense plasma on the equator between the capsule and hohlraum wall. The inner laser beams experience less inverse bremsstrahlung absorption before reaching the wall. The X-ray drive is thus stronger from the equator with the imposed field. We study superthermal, or ‘hot’, electron dynamics with the particle-in-cell code ZUMA, using plasma conditions from HYDRA. During the early-time laser picket, hot electrons based on two-plasmon decay in the laser entrance hole (Regan et al., Phys. Plasmas, vol. 17(2), 2010, 020703) are guided to the capsule by a 70 T field. Twelve times more energy deposits in the deuterium–tritium fuel. For plasma conditions early in peak laser power, we present mono-energetic test-case studies with ZUMA as well as sources based on inner-beam stimulated Raman scattering. Furthermore, the effect of the field on deuterium–tritium deposition depends strongly on the source location, namely whether hot electrons are generated on field lines that connect to the capsule.« less

Energy transport in plasmas produced by a high brightness krypton fluoride laser focused to a line

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Hadithi, Y.; Tallents, G.J.; Zhang, J.

A high brightness krypton fluoride Raman laser (wavelength 0.268 [mu]m) generating 0.3 TW, 12 ps pulses with 20 [mu]rad beam divergence and a prepulse of less than 10[sup [minus]10] has been focused to produce a 10 [mu]m wide line focus (irradiances [similar to]0.8--4[times]10[sup 15] W cm[sup [minus]2]) on plastic targets with a diagnostic sodium fluoride (NaF) layer buried within the target. Axial and lateral transport of energy has been measured by analysis of x-ray images of the line focus and from x-ray spectra emitted by the layer of NaF with varying overlay thicknesses. It is shown that the ratio ofmore » the distance between the critical density surface and the ablation surface to the laser focal width controls lateral transport in a similar manner as for previous spot focus experiments. The measured axial energy transport is compared to MEDUSA [J. P. Christiansen, D. E. T. F. Ashby, and K. V. Roberts, Comput. Phys. Commun. [bold 7], 271 (1974)] one-dimensional hydrodynamic code simulations with an average atom post-processor for predicting spectral line intensities. An energy absorption of [similar to]10% in the code gives agreement with the experimental axial penetration. Various measured line ratios of hydrogen- and helium-like Na and F are investigated as temperature diagnostics in the NaF layer using the RATION [R. W. Lee, B. L. Whitten, and R. E. Strout, J. Quant. Spectrosc. Radiat. Transfer [bold 32], 91 (1984)] code.« less

Chromatic energy filter and characterization of laser-accelerated proton beams for particle therapy

NASA Astrophysics Data System (ADS)

Hofmann, Ingo; Meyer-ter-Vehn, Jürgen; Yan, Xueqing; Al-Omari, Husam

2012-07-01

The application of laser accelerated protons or ions for particle therapy has to cope with relatively large energy and angular spreads as well as possibly significant random fluctuations. We suggest a method for combined focusing and energy selection, which is an effective alternative to the commonly considered dispersive energy selection by magnetic dipoles. Our method is based on the chromatic effect of a magnetic solenoid (or any other energy dependent focusing device) in combination with an aperture to select a certain energy width defined by the aperture radius. It is applied to an initial 6D phase space distribution of protons following the simulation output from a Radiation Pressure Acceleration model. Analytical formula for the selection aperture and chromatic emittance are confirmed by simulation results using the TRACEWIN code. The energy selection is supported by properly placed scattering targets to remove the imprint of the chromatic effect on the beam and to enable well-controlled and shot-to-shot reproducible energy and transverse density profiles.

Monte Carlo simulation study of positron generation in ultra-intense laser-solid interactions

NASA Astrophysics Data System (ADS)

Yan, Yonghong; Wu, Yuchi; Zhao, Zongqing; Teng, Jian; Yu, Jinqing; Liu, Dongxiao; Dong, Kegong; Wei, Lai; Fan, Wei; Cao, Leifeng; Yao, Zeen; Gu, Yuqiu

2012-02-01

The Monte Carlo transport code Geant4 has been used to study positron production in the transport of laser-produced hot electrons in solid targets. The dependence of the positron yield on target parameters and the hot-electron temperature has been investigated in thick targets (mm-scale), where only the Bethe-Heitler process is considered. The results show that Au is the best target material, and an optimal target thickness exists for generating abundant positrons at a given hot-electron temperature. The positron angular distributions and energy spectra for different hot electron temperatures were studied without considering the sheath field on the back of the target. The effect of the target rear sheath field for positron acceleration was studied by numerical simulation while including an electrostatic field in the Monte Carlo model. It shows that the positron energy can be enhanced and quasi-monoenergetic positrons are observed owing to the effect of the sheath field.

Advances in petascale kinetic plasma simulation with VPIC and Roadrunner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bowers, Kevin J; Albright, Brian J; Yin, Lin

2009-01-01

VPIC, a first-principles 3d electromagnetic charge-conserving relativistic kinetic particle-in-cell (PIC) code, was recently adapted to run on Los Alamos's Roadrunner, the first supercomputer to break a petaflop (10{sup 15} floating point operations per second) in the TOP500 supercomputer performance rankings. They give a brief overview of the modeling capabilities and optimization techniques used in VPIC and the computational characteristics of petascale supercomputers like Roadrunner. They then discuss three applications enabled by VPIC's unprecedented performance on Roadrunner: modeling laser plasma interaction in upcoming inertial confinement fusion experiments at the National Ignition Facility (NIF), modeling short pulse laser GeV ion acceleration andmore » modeling reconnection in magnetic confinement fusion experiments.« less

Active imaging systems to see through adverse conditions: Light-scattering based models and experimental validation

NASA Astrophysics Data System (ADS)

Riviere, Nicolas; Ceolato, Romain; Hespel, Laurent

2014-10-01

Onera, the French aerospace lab, develops and models active imaging systems to understand the relevant physical phenomena affecting these systems performance. As a consequence, efforts have been done on the propagation of a pulse through the atmosphere and on target geometries and surface properties. These imaging systems must operate at night in all ambient illumination and weather conditions in order to perform strategic surveillance for various worldwide operations. We have implemented codes for 2D and 3D laser imaging systems. As we aim to image a scene in the presence of rain, snow, fog or haze, we introduce such light-scattering effects in our numerical models and compare simulated images with measurements provided by commercial laser scanners.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakaki, H.; Fukuda, Y.; Nishiuchi, M.

A single-shot-imaging thin scintillator film was developed for an online Thomson parabola (TP) spectrometer and the first analysis of laser accelerated ions, using the online TP spectrometer, was demonstrated at the JAEA-Kansai Advanced Relativistic Engineering Laser System (J-KAREN). An energy spectrum of {approx}4.0 MeV protons is obtained using only this imaging film without the need of a microchannel plate that is typically utilized in online ion analyses. A general-purpose Monte Carlo particle and heavy ion-transport code system, which consists of various quantum dynamics models, was used for the prediction of the luminescent properties of the scintillator. The simulation can reasonablymore » predict not only the ion trajectories detected by the spectrometer, but also luminescence properties.« less

Evaluation of a satellite laser ranging technique using pseudonoise code modulated laser diodes

NASA Technical Reports Server (NTRS)

Ball, Carolyn Kay

1987-01-01

Several types of Satellite Laser Ranging systems exist, operating with pulsed, high-energy lasers. The distance between a ground point and an orbiting satellite can be determined to within a few centimeters. A new technique substitutes pseudonoise code modulated laser diodes, which are much more compact, reliable and less costly, for the lasers now used. Since laser diode technology is only now achieving sufficiently powerful lasers, the capabilities of the new technique are investigated. Also examined are the effects of using an avalanche photodiode detector instead of a photomultiplier tube. The influence of noise terms (including background radiation, detector dark and thermal noise and speckle) that limit the system range and performance is evaluated.

Electromagnetic Gauge Study of Laser-Induced Shock Waves in Aluminium Alloys

NASA Astrophysics Data System (ADS)

Peyre, P.; Fabbro, R.

1995-12-01

The laser-shock behaviour of three industrial aluminum alloys has been analyzed with an Electromagnetic Gauge Method (EMV) for measuring the velocity of the back free surface of thin foils submitted to plane laser irradiation. Surface pressure, shock decay in depth and Hugoniot Elastic Limits (HEL) of the materials were investigated with increasing thicknesses of foils to be shocked. First, surface peak pressures values as a function of laser power density gave a good agreement with conventional piezoelectric quartz measurements. Therefore, comparison of experimental results with computer simulations, using a 1D hydrodynamic Lagrangian finite difference code, were also in good accordance. Lastly, HEL values were compared with static and dynamic compressive tests in order to estimate the effects of a very large range of strain rates (10^{-3} s^{-1} to 10^6 s^{-1}) on the mechanical properties of the alloys. Cet article fait la synthèse d'une étude récente sur la caractérisation du comportement sous choc-laser de trois alliages d'aluminium largement utilisés dans l'industrie à travers la méthode dite de la jauge électromagnétique. Cette méthode permet de mesurer les vitesses matérielles induites en face arrière de plaques d'épaisseurs variables par un impact laser. La mise en vitesse de plaques nous a permis, premièrement, de vérifier la validité des pressions d'impact superficielles obtenues en les comparant avec des résultats antérieurs obtenus par des mesures sur capteurs quartz. Sur des plaques d'épaisseurs croissantes, nous avons caractérisé l'atténuation des ondes de choc en profondeur dans les alliages étudiés et mesuré les limites d'élasticité sous choc (pressions d'Hugoniot) des alliages. Les résultats ont été comparés avec succès à des simulations numériques grâce à un code de calcul monodimensionnel Lagrangien. Enfin, les valeurs des pressions d'Hugoniot mesurées ont permis de tracer l'évolution des contraintes d'écoulement plastique en fonction de la vitesse de déformation pour des valeurs comprises entre 10^{-3} s^{-1} et 10^6 s^{-1}.

Theoretical quantification of shock-timing sensitivities for direct-drive inertial confinement fusion implosions on OMEGA

DOE PAGES

Cao, D.; Boehly, T. R.; Gregor, M. C.; ...

2018-05-16

Using temporally shaped laser pulses, multiple shocks can be launched in direct-drive inertial confinement fusion implosion experiments to set the shell on a desired isentrope or adiabat. The velocity of the first shock and the times at which subsequent shocks catch up to it are measured through the VISAR diagnostic on OMEGA. Simulations reproduce these velocity and shock-merger time measurements when using laser pulses designed for setting mid-adiabat (α ~ 3) implosions, but agreement degrades for lower-adiabat (α ~ 1) designs. Several possibilities for this difference are studied: errors in placing the target at the center of irradiation (target offset),more » variations in energy between the different incident beams (power imbalance), and errors in modeling the laser energy coupled into the capsule. Simulation results indicate that shock timing is most sensitive to details of the density and temperature profiles in the coronal plasma, which influences the laser energy coupled into the target, and only marginally sensitive to target offset and beam power imbalance. A new technique under development to infer coronal profiles using x-ray self-emission imaging can be applied to the pulse shapes used in shock-timing experiments. In conclusion, this will help identify improved physics models to implement in codes and consequently enhance shock-timing predictive capability for low-adiabat pulses.« less

Convective Heating of the LIFE Engine Target During Injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holdener, D S; Tillack, M S; Wang, X R

2011-10-24

Target survival in the hostile, high temperature xenon environment of the proposed Laser Inertial Fusion Energy (LIFE) engine is critical. This work focuses on the flow properties and convective heat load imposed upon the surface of the indirect drive target while traveling through the xenon gas. While this rarefied flow is traditionally characterized as being within the continuum regime, it is approaching transition where conventional CFD codes reach their bounds of operation. Thus ANSYS, specifically the Navier-Stokes module CFX, will be used in parallel with direct simulation Monte Carlo code DS2V and analytically and empirically derived expressions for heat transfermore » to the hohlraum for validation. Comparison of the viscous and thermal boundary layers of ANSYS and DS2V were shown to be nearly identical, with the surface heat flux varying less than 8% on average. From the results herein, external baffles have been shown to reduce this heat transfer to the sensitive laser entrance hole (LEH) windows and optimize target survival independent of other reactor parameters.« less

Pseudorandom Noise Code-Based Technique for Thin Cloud Discrimination with CO2 and O2 Absorption Measurements

NASA Technical Reports Server (NTRS)

Campbell, Joel F.; Prasad, Narasimha S.; Flood, Michael A.

2011-01-01

NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the detection of CO2 and O2 from space based platforms suitable for ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multi-frequency, intensity modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a pseudo noise (PN) code based technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated, Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths.

Generation of warm dense matter using an argon based capillary discharge laser

NASA Astrophysics Data System (ADS)

Rossall, A. K.; Tallents, G. J.

2015-06-01

Argon based capillary discharge lasers operating in the extreme ultra violet (EUV) at 46.9 nm with output up to 0.5 mJ energy per pulse and repetition rates up to 10 Hz are capable of focused irradiances of 109-1012 W cm-2 and can be used to generate plasma in the warm dense matter regime by irradiating solid material. To model the interaction between such an EUV laser and solid material, the 2D radiative-hydrodynamic code POLLUX has been modified to include absorption via direct photo-ionisation, a super-configuration model to describe the ionization-dependent electronic configurations and a calculation of plasma refractive indices for ray tracing of the incident EUV laser radiation. A simulation study is presented, demonstrating how capillary discharge lasers of 1200 ps pulse duration can be used to generate warm dense matter at close to solid densities with temperatures of a few eV and energy densities up to 1 × 105 J cm-3. Plasmas produced by EUV laser irradiation are shown to be useful for examining the properties of warm dense matter as, for example, plasma emission is not masked by hotter, less dense plasma emission that occurs with visible/infra-red laser target irradiation.

A Novel Technique to Detect Code for SAC-OCDMA System

NASA Astrophysics Data System (ADS)

Bharti, Manisha; Kumar, Manoj; Sharma, Ajay K.

2018-04-01

The main task of optical code division multiple access (OCDMA) system is the detection of code used by a user in presence of multiple access interference (MAI). In this paper, new method of detection known as XOR subtraction detection for spectral amplitude coding OCDMA (SAC-OCDMA) based on double weight codes has been proposed and presented. As MAI is the main source of performance deterioration in OCDMA system, therefore, SAC technique is used in this paper to eliminate the effect of MAI up to a large extent. A comparative analysis is then made between the proposed scheme and other conventional detection schemes used like complimentary subtraction detection, AND subtraction detection and NAND subtraction detection. The system performance is characterized by Q-factor, BER and received optical power (ROP) with respect to input laser power and fiber length. The theoretical and simulation investigations reveal that the proposed detection technique provides better quality factor, security and received power in comparison to other conventional techniques. The wide opening of eye in case of proposed technique also proves its robustness.

The EGS4 Code System: Solution of Gamma-ray and Electron Transport Problems

DOE R&D Accomplishments Database

Nelson, W. R.; Namito, Yoshihito

1990-03-01

In this paper we present an overview of the EGS4 Code System -- a general purpose package for the Monte Carlo simulation of the transport of electrons and photons. During the last 10-15 years EGS has been widely used to design accelerators and detectors for high-energy physics. More recently the code has been found to be of tremendous use in medical radiation physics and dosimetry. The problem-solving capabilities of EGS4 will be demonstrated by means of a variety of practical examples. To facilitate this review, we will take advantage of a new add-on package, called SHOWGRAF, to display particle trajectories in complicated geometries. These are shown as 2-D laser pictures in the written paper and as photographic slides of a 3-D high-resolution color monitor during the oral presentation. 11 refs., 15 figs.

Main functions, recent updates, and applications of Synchrotron Radiation Workshop code

NASA Astrophysics Data System (ADS)

Chubar, Oleg; Rakitin, Maksim; Chen-Wiegart, Yu-Chen Karen; Chu, Yong S.; Fluerasu, Andrei; Hidas, Dean; Wiegart, Lutz

2017-08-01

The paper presents an overview of the main functions and new application examples of the "Synchrotron Radiation Workshop" (SRW) code. SRW supports high-accuracy calculations of different types of synchrotron radiation, and simulations of propagation of fully-coherent radiation wavefronts, partially-coherent radiation from a finite-emittance electron beam of a storage ring source, and time-/frequency-dependent radiation pulses of a free-electron laser, through X-ray optical elements of a beamline. An extended library of physical-optics "propagators" for different types of reflective, refractive and diffractive X-ray optics with its typical imperfections, implemented in SRW, enable simulation of practically any X-ray beamline in a modern light source facility. The high accuracy of calculation methods used in SRW allows for multiple applications of this code, not only in the area of development of instruments and beamlines for new light source facilities, but also in areas such as electron beam diagnostics, commissioning and performance benchmarking of insertion devices and individual X-ray optical elements of beamlines. Applications of SRW in these areas, facilitating development and advanced commissioning of beamlines at the National Synchrotron Light Source II (NSLS-II), are described.

Validation of High-Speed Turbulent Boundary Layer and Shock-Boundary Layer Interaction Computations with the OVERFLOW Code

NASA Technical Reports Server (NTRS)

Oliver, A. B.; Lillard, R. P.; Blaisdell, G. A.; Lyrintizis, A. S.

2006-01-01

The capability of the OVERFLOW code to accurately compute high-speed turbulent boundary layers and turbulent shock-boundary layer interactions is being evaluated. Configurations being investigated include a Mach 2.87 flat plate to compare experimental velocity profiles and boundary layer growth, a Mach 6 flat plate to compare experimental surface heat transfer,a direct numerical simulation (DNS) at Mach 2.25 for turbulent quantities, and several Mach 3 compression ramps to compare computations of shock-boundary layer interactions to experimental laser doppler velocimetry (LDV) data and hot-wire data. The present paper describes outlines the study and presents preliminary results for two of the flat plate cases and two small-angle compression corner test cases.

A Test of Superradiance in an FEL Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyce, R

We describe the design of an FEL Amplifier Test Experiment (FATE)1 to demonstrate the superradiant short bunch regime of a Free Electron Laser in the 1-3 {micro}m wavelength range starting from noise. The relevance to the LCLS X-ray FEL [1] proposal is discussed and numerical simulations are shown. It is numerically demonstrated for the first time with the 2-D code GINGER, that clean-up of noise in the superradiant regime occurs even at low power levels.

Tapered undulator for SASE FELs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fawley, William M.; Huang, Zhirong; Kim, Kwang-Je

We discuss the use of tapered undulators to enhance the performance of free-electron lasers (FELs) based upon self-amplified spontaneous emission (SASE), where the radiation tends to have a relatively broad bandwidth, limited temporal phase coherence, and large amplitude fluctuations. Using the polychromatic FEL simulation code GINGER, we numerically demonstrate the effectiveness of a tapered undulator for parameters corresponding to the existing Argonne low-energy undulator test line (LEUTL) FEL. We also study possible tapering options for proposed x-ray FELs such as the Linac Coherent Light Source (LCLS).

Spontaneous and amplified radiation at the initial stage of a SASE FEL.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Z.; Kim, K.-J.

At the initial stage of a self-amplified spontaneous emission (SASE) free-electron laser (FEL), spontaneous undulator radiation in certain experimental configurations can dominate the amplified signal over an extended undulator distance. In this paper they study both the spontaneous and the amplified radiation in the framework of the paraxial wave equation and determine the transition from the dominance of spontaneous emission to exponential amplification. They compare theoretical expectations with SASE simulation codes GINGER and GENESIS.

Assessment and Mitigation of Radiation, EMP, Debris & Shrapnel Impacts at Megajoule-Class Laser Facilities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eder, D C; Anderson, R W; Bailey, D S

2009-10-05

The generation of neutron/gamma radiation, electromagnetic pulses (EMP), debris and shrapnel at mega-Joule class laser facilities (NIF and LMJ) impacts experiments conducted at these facilities. The complex 3D numerical codes used to assess these impacts range from an established code that required minor modifications (MCNP - calculates neutron and gamma radiation levels in complex geometries), through a code that required significant modifications to treat new phenomena (EMSolve - calculates EMP from electrons escaping from laser targets), to a new code, ALE-AMR, that is being developed through a joint collaboration between LLNL, CEA, and UC (UCSD, UCLA, and LBL) for debrismore » and shrapnel modelling.« less

Laser pulse coded signal frequency measuring device based on DSP and CPLD

NASA Astrophysics Data System (ADS)

Zhang, Hai-bo; Cao, Li-hua; Geng, Ai-hui; Li, Yan; Guo, Ru-hai; Wang, Ting-feng

2011-06-01

Laser pulse code is an anti-jamming measures used in semi-active laser guided weapons. On account of the laser-guided signals adopting pulse coding mode and the weak signal processing, it need complex calculations in the frequency measurement process according to the laser pulse code signal time correlation to meet the request in optoelectronic countermeasures in semi-active laser guided weapons. To ensure accurately completing frequency measurement in a short time, it needed to carry out self-related process with the pulse arrival time series composed of pulse arrival time, calculate the signal repetition period, and then identify the letter type to achieve signal decoding from determining the time value, number and rank number in a signal cycle by Using CPLD and DSP for signal processing chip, designing a laser-guided signal frequency measurement in the pulse frequency measurement device, improving the signal processing capability through the appropriate software algorithms. In this article, we introduced the principle of frequency measurement of the device, described the hardware components of the device, the system works and software, analyzed the impact of some system factors on the accuracy of the measurement. The experimental results indicated that this system improve the accuracy of the measurement under the premise of volume, real-time, anti-interference, low power of the laser pulse frequency measuring device. The practicality of the design, reliability has been demonstrated from the experimental point of view.

Hybrid-PIC modeling of laser-plasma interactions and hot electron generation in gold hohlraum walls

NASA Astrophysics Data System (ADS)

Thoma, C.; Welch, D. R.; Clark, R. E.; Rose, D. V.; Golovkin, I. E.

2017-06-01

The walls of the hohlraum used in experiments at the national ignition facility are heated by laser beams with intensities ˜ 10 15 W/cm2, a wavelength of ˜ 1 / 3 μm, and pulse lengths on the order of a ns, with collisional absorption believed to be the primary heating mechanism. X-rays generated by the hot ablated plasma at the gold walls are then used to implode a target in the hohlraum interior. In addition to the collisional absorption of laser energy at the walls, non-linear laser-plasma interactions (LPI), such as stimulated Raman scattering and two plasmon decay, are believed to generate a population of supra-thermal electrons which, if present in the hohlraum, can have a deleterious effect on target implosion. We describe results of hohlraum modeling using a hybrid particle-in-cell code. To enable this work, new particle-based algorithms for a multiple-ion magneto-hydrodynamic (MHD) treatment, and a particle-based ray-tracing model were developed. The use of such hybrid methods relaxes the requirement to resolve the laser wavelength, and allows for relatively large-scale hohlraum simulations with a reasonable number of cells. But the non-linear effects which are believed to be the cause of hot electron generation can only be captured by fully kinetic simulations with good resolution of the laser wavelength. For this reason, we employ a two-tiered approach to hohlraum modeling. Large-scale simulations of the collisional absorption process can be conducted using the fast quasi-neutral MHD algorithm with fluid particle species. From these simulations, we can observe the time evolution of the hohlraum walls and characterize the density and temperature profiles. From these results, we can transition to smaller-scale highly resolved simulations using traditional kinetic particle-in-cell methods, from which we can fully model all of the non-linear laser-plasma interactions, as well as assess the details of the electron distribution function. We find that vacuum hohlraums should be stable to both two plasmon decay and stimulated Raman scattering instabilities for intensities ≤ 10 15 W/cm2. In gas-filled hohlraums, shocks may be induced in the blowoff gold plasma, which leads to more complex density and temperatures profiles. The resulting effect on LPI stability depends strongly on the details of the profile, and it is possible for the gas-filled hohlraum to become unstable to two plasmon decay at 1015 W/cm2 if the quarter-critical surface reaches temperatures exceeding 1 keV.

Laser beam-profile impression and target thickness impact on laser-accelerated protons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schollmeier, M.; Harres, K.; Nuernberg, F.

Experimental results on the influence of the laser focal spot shape onto the beam profile of laser-accelerated protons from gold foils are reported. The targets' microgrooved rear side, together with a stack of radiochromic films, allowed us to deduce the energy-dependent proton source-shape and size, respectively. The experiments show, that shape and size of the proton source depend only weakly on target thickness as well as shape of the laser focus, although they strongly influence the proton's intensity distribution. It was shown that the laser creates an electron beam that closely follows the laser beam topology, which is maintained duringmore » the propagation through the target. Protons are then accelerated from the rear side with an electron created electric field of a similar shape. Simulations with the Sheath-Accelerated Beam Ray-tracing for IoN Analysis code SABRINA, which calculates the proton distribution in the detector for a given laser-beam profile, show that the electron distribution during the transport through a thick target (50 {mu}m Au) is only modified due to multiple small angle scattering. Thin targets (10 {mu}m) show large source sizes of over 100 {mu}m diameter for 5 MeV protons, which cannot be explained by multiple scattering only and are most likely the result of refluxing electrons.« less

Three-dimensional hydrodynamic simulations of OMEGA implosions

NASA Astrophysics Data System (ADS)

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.; Campbell, E. M.; Epstein, R.; Forrest, C. J.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Marshall, F. J.; McCrory, R. L.; Regan, S. P.; Sangster, T. C.; Stoeckl, C.; Schmitt, A. J.; Obenschain, S.

2017-05-01

The effects of large-scale (with Legendre modes ≲ 10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets ( ˜10 to 20 μm), beam-power imbalance ( σrms˜10 %), and variations ( ˜5 %) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosion targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ˜1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh-Taylor growth.

Three-dimensional hydrodynamic simulations of OMEGA implosions

DOE PAGES

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.; ...

2017-03-30

Here, the effects of large-scale (with Legendre modes ≲10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets (~10 to 20 μm), beam-power imbalance (σ rms ~ 10%), and variations (~5%) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosionmore » targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ~1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh–Taylor growth.« less

Three-dimensional hydrodynamic simulations of OMEGA implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Igumenshchev, I. V.; Michel, D. T.; Shah, R. C.

Here, the effects of large-scale (with Legendre modes ≲10) asymmetries in OMEGA direct-drive implosions caused by laser illumination nonuniformities (beam-power imbalance and beam mispointing and mistiming), target offset, and variation in target-layer thickness were investigated using the low-noise, three-dimensional Eulerian hydrodynamic code ASTER. Simulations indicate that these asymmetries can significantly degrade the implosion performance. The most important sources of the asymmetries are the target offsets (~10 to 20 μm), beam-power imbalance (σ rms ~ 10%), and variations (~5%) in target-layer thickness. Large-scale asymmetries distort implosion cores, resulting in a reduced hot-spot confinement and an increased residual kinetic energy of implosionmore » targets. The ion temperature inferred from the width of simulated neutron spectra is influenced by bulk fuel motion in the distorted hot spot and can result in up to an ~1 -keV increase in apparent temperature. Similar temperature variations along different lines of sight are observed. Demonstrating hydrodynamic equivalence to ignition designs on OMEGA requires a reduction in large-scale target and laser-imposed nonuniformities, minimizing target offset, and employing highly efficient mid-adiabat (α = 4) implosion designs, which mitigate cross-beam energy transfer and suppress short-wavelength Rayleigh–Taylor growth.« less

Acceleration of planar foils by the indirect-direct drive scheme

NASA Astrophysics Data System (ADS)

Honrubia, J. J.; Martínez-Val, J. M.; Bocher, J. L.; Faucheux, G.

1996-05-01

We have investigated the hydrodynamic response of plastic and aluminum foils accelerated by a pulse formed by an x-ray prepulse followed by the main laser pulse. This illumination scheme, so-called indirect-direct drive scheme, has been proposed as an alternative to the direct and indirect drive. The advantages of such a scheme are that it can contribute to solve the problem of uniformity of the direct drive and, at the same time, it can be much more efficient and use simpler targets than the indirect-drive. Experiments about this hybrid drive scheme have been performed at Limeil with the PHEBUS facility and the standard experimental set-up and diagnostics. The agreement between experiments and simulations is good for quantities such as the energy of the laser converted into x-rays and the burnthrough time of the converter foil. To simulate the full hydrodynamic evolution of the converter and target foils separated a distance of 1 mm, 2-D effects should be taken into account. The basic goals have been to check the simulation codes developed by the Institute of Nuclear Fusion and to determine the hydrodynamic response of the target foil to the hybrid pulse. These goals have been fulfilled.

Laser-driven x-ray and neutron source development for industrial applications of plasma accelerators

NASA Astrophysics Data System (ADS)

Brenner, C. M.; Mirfayzi, S. R.; Rusby, D. R.; Armstrong, C.; Alejo, A.; Wilson, L. A.; Clarke, R.; Ahmed, H.; Butler, N. M. H.; Haddock, D.; Higginson, A.; McClymont, A.; Murphy, C.; Notley, M.; Oliver, P.; Allott, R.; Hernandez-Gomez, C.; Kar, S.; McKenna, P.; Neely, D.

2016-01-01

Pulsed beams of energetic x-rays and neutrons from intense laser interactions with solid foils are promising for applications where bright, small emission area sources, capable of multi-modal delivery are ideal. Possible end users of laser-driven multi-modal sources are those requiring advanced non-destructive inspection techniques in industry sectors of high value commerce such as aerospace, nuclear and advanced manufacturing. We report on experimental work that demonstrates multi-modal operation of high power laser-solid interactions for neutron and x-ray beam generation. Measurements and Monte Carlo radiation transport simulations show that neutron yield is increased by a factor ~2 when a 1 mm copper foil is placed behind a 2 mm lithium foil, compared to using a 2 cm block of lithium only. We explore x-ray generation with a 10 picosecond drive pulse in order to tailor the spectral content for radiography with medium density alloy metals. The impact of using  >1 ps pulse duration on laser-accelerated electron beam generation and transport is discussed alongside the optimisation of subsequent bremsstrahlung emission in thin, high atomic number target foils. X-ray spectra are deconvolved from spectrometer measurements and simulation data generated using the GEANT4 Monte Carlo code. We also demonstrate the unique capability of laser-driven x-rays in being able to deliver single pulse high spatial resolution projection imaging of thick metallic objects. Active detector radiographic imaging of industrially relevant sample objects with a 10 ps drive pulse is presented for the first time, demonstrating that features of 200 μm size are resolved when projected at high magnification.

Modified Laser and Thermos cell calculations on microcomputers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shapiro, A.; Huria, H.C.

1987-01-01

In the course of designing and operating nuclear reactors, many fuel pin cell calculations are required to obtain homogenized cell cross sections as a function of burnup. In the interest of convenience and cost, it would be very desirable to be able to make such calculations on microcomputers. In addition, such a microcomputer code would be very helpful for educational course work in reactor computations. To establish the feasibility of making detailed cell calculations on a microcomputer, a mainframe cell code was compiled and run on a microcomputer. The computer code Laser, originally written in Fortran IV for the IBM-7090more » class of mainframe computers, is a cylindrical, one-dimensional, multigroup lattice cell program that includes burnup. It is based on the MUFT code for epithermal and fast group calculations, and Thermos for the thermal calculations. There are 50 fast and epithermal groups and 35 thermal groups. Resonances are calculated assuming a homogeneous system and then corrected for self-shielding, Dancoff, and Doppler by self-shielding factors. The Laser code was converted to run on a microcomputer. In addition, the Thermos portion of Laser was extracted and compiled separately to have available a stand alone thermal code.« less

Safety with surgical lasers.

PubMed

McKenzie, A L

1984-01-01

As the sales of surgical lasers continue to grow, the problem of laser safety in hospitals becomes increasingly more urgent. This article considers both the principles and the practice of laser safety, and indicates how safety codes should be organized within a hospital. Eye safety is of paramount importance, and the effects of different wavelengths of laser radiation on the eye are described, both for intrabeam and extended-source exposure. An account is given of the concept of Maximum Permissible Exposure (MPE) and how it depends upon wavelength and exposure duration. The standard laser classification is developed in relation to MPE. The use of laser protective eyewear is discussed for the surgeon, other theatre staff and the patient. Finally, the role of the Laser Protection Supervisor and of the Laser Protection Adviser are explained in the context of establishing a local laser safety code.

Development and characterization of plasma targets for controlled injection of electrons into laser-driven wakefields

NASA Astrophysics Data System (ADS)

Kleinwaechter, Tobias; Goldberg, Lars; Palmer, Charlotte; Schaper, Lucas; Schwinkendorf, Jan-Patrick; Osterhoff, Jens

2012-10-01

Laser-driven wakefield acceleration within capillary discharge waveguides has been used to generate high-quality electron bunches with GeV-scale energies. However, owing to fluctuations in laser and plasma conditions in combination with a difficult to control self-injection mechanism in the non-linear wakefield regime these bunches are often not reproducible and can feature large energy spreads. Specialized plasma targets with tailored density profiles offer the possibility to overcome these issues by controlling the injection and acceleration processes. This requires precise manipulation of the longitudinal density profile. Therefore our target concept is based on a capillary structure with multiple gas in- and outlets. Potential target designs are simulated using the fluid code OpenFOAM and those meeting the specified criteria are fabricated using femtosecond-laser machining of structures into sapphire plates. Density profiles are measured over a range of inlet pressures utilizing gas-density profilometry via Raman scattering and pressure calibration with longitudinal interferometry. In combination these allow absolute density mapping. Here we report the preliminary results.

SuperGaussian distribution functions in inhomogenous plasmas

NASA Astrophysics Data System (ADS)

Matte, Jean-Pierre

2008-11-01

In plasmas heated by a narrow laser beam, the shape of the distribution function is influenced by both the absorption, which tends to give a superGaussian (DLM) distribution function [1], and the effects of heat flow, which tends to make the distribution more Maxwellian, when the hot region is considerably wider than the laser beam [2]. Thus, it is only at early times that the deformation is as strong as predicted by our uniform intensity formula [1]. A large number of electron kinetic simulations of a finite width laser beam heating a uniform density plasma were performed with the electron kinetic code FPI [1] to study the competition between these two mechanisms. In some cases, the deformation is approximately given by this formula if we average the laser intensity over the entire plasma. This may explain why distributions were more Maxwellian than expected in some experiments [3]. [0pt] [1] J.-P. Matte et al., Plasma Phys. Contr. Fusion 30, 1665 (1988) [2] S. Brunner and E. Valeo, Phys. Plasmas 9, 923 (2002) [3] S.H. Glenzer et al., Phys. Rev. Lett. 82, 97 (1999).

On the Initiation Mechanism in Exploding Bridgewire and Laser Detonators

NASA Astrophysics Data System (ADS)

Stewart, D. Scott; Thomas, K.; Saenz, J.

2005-07-01

Since its invention by Los Alamos during the Manhattan Project era the exploding bridgewire detonator (EBW) has seen tremendous use and study. Recent development of a laser-powered device with detonation properties similar to an EBW is reviving interest in the basic physics of the Deflagration-to-Detonation (DDT) process in both of these devices,[1]. Cutback experiments using both laser interferometry and streak camera observations are providing new insight into the initiation mechanism in EBWs. These measurements are being correlated to a DDT model of compaction to detonation and shock to detonation developed previously by Xu and Stewart, [2]. The DDT model is incorporated into a high-resolution, multi-material model code for simulating the complete process. Model formulation and predictions against the test data will be discussed. REFS. [1] A. Munger, J. Kennedy, A. Akinci, and K. Thomas, "Dev. of a Laser Detonator" 30th Int. Pyrotechnics Seminar, Fort Collins, CO, (2004). [2] Xu, S. and Stewart, D. S. Deflagration to detonation transition in porous energetic materials: A model study. J. Eng. Math., 31, 143-172 (1997)

Laser-Material Interaction of Powerful Ultrashort Laser Pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komashko, A

2003-01-06

Laser-material interaction of powerful (up to a terawatt) ultrashort (several picoseconds or shorter) laser pulses and laser-induced effects were investigated theoretically in this dissertation. Since the ultrashort laser pulse (USLP) duration time is much smaller than the characteristic time of the hydrodynamic expansion and thermal diffusion, the interaction occurs at a solid-like material density with most of the light energy absorbed in a thin surface layer. Powerful USLP creates hot, high-pressure plasma, which is quickly ejected without significant energy diffusion into the bulk of the material, Thus collateral damage is reduced. These and other features make USLPs attractive for amore » variety of applications. The purpose of this dissertation was development of the physical models and numerical tools for improvement of our understanding of the process and as an aid in optimization of the USLP applications. The study is concentrated on two types of materials - simple metals (materials like aluminum or copper) and wide-bandgap dielectrics (fused silica, water). First, key physical phenomena of the ultrashort light interaction with metals and the models needed to describe it are presented. Then, employing one-dimensional plasma hydrodynamics code enhanced with models for laser energy deposition and material properties at low and moderate temperatures, light absorption was self-consistently simulated as a function of laser wavelength, pulse energy and length, angle of incidence and polarization. Next, material response on time scales much longer than the pulse duration was studied using the hydrocode and analytical models. These studies include examination of evolution of the pressure pulses, effects of the shock waves, material ablation and removal and three-dimensional dynamics of the ablation plume. Investigation of the interaction with wide-bandgap dielectrics was stimulated by the experimental studies of the USLP surface ablation of water (water is a model of biological tissue) and laser-induced pressure waves. Simulations on the basis of the nonlinear ionization equation were used to examine effects of the laser created surface plasma on light absorption, reflection and transmission. Laser pulse energy conversion efficiency into pressure waves was studied experimentally and theoretically.« less

Continuum Vlasov Simulation in Four Phase-space Dimensions

NASA Astrophysics Data System (ADS)

Cohen, B. I.; Banks, J. W.; Berger, R. L.; Hittinger, J. A.; Brunner, S.

2010-11-01

In the VALHALLA project, we are developing scalable algorithms for the continuum solution of the Vlasov-Maxwell equations in two spatial and two velocity dimensions. We use fourth-order temporal and spatial discretizations of the conservative form of the equations and a finite-volume representation to enable adaptive mesh refinement and nonlinear oscillation control [1]. The code has been implemented with and without adaptive mesh refinement, and with electromagnetic and electrostatic field solvers. A goal is to study the efficacy of continuum Vlasov simulations in four phase-space dimensions for laser-plasma interactions. We have verified the code in examples such as the two-stream instability, the weak beam-plasma instability, Landau damping, electron plasma waves with electron trapping and nonlinear frequency shifts [2]^ extended from 1D to 2D propagation, and light wave propagation.^ We will report progress on code development, computational methods, and physics applications. This work was performed under the auspices of the U.S. DOE by LLNL under contract no. DE-AC52-07NA27344. This work was funded by the Lab. Dir. Res. and Dev. Prog. at LLNL under project tracking code 08-ERD-031. [1] J.W. Banks and J.A.F. Hittinger, to appear in IEEE Trans. Plas. Sci. (Sept., 2010). [2] G.J. Morales and T.M. O'Neil, Phys. Rev. Lett. 28,417 (1972); R. L. Dewar, Phys. Fluids 15,712 (1972).

Pulse shaping and energy storage capabilities of angularly multiplexed KrF laser fusion drivers

NASA Astrophysics Data System (ADS)

Lehmberg, R. H.; Giuliani, J. L.; Schmitt, A. J.

2009-07-01

This paper describes a rep-rated multibeam KrF laser driver design for the 500kJ Inertial Fusion test Facility (FTF) recently proposed by NRL, then models its optical pulse shaping capabilities using the ORESTES laser kinetics code. It describes a stable and reliable iteration technique for calculating the required precompensated input pulse shape that will achieve the desired output shape, even when the amplifiers are heavily saturated. It also describes how this precompensation technique could be experimentally implemented in real time on a reprated laser system. The simulations show that this multibeam system can achieve a high fidelity pulse shaping capability, even for a high gain shock ignition pulse whose final spike requires output intensities much higher than the ˜4MW/cm2 saturation levels associated with quasi-cw operation; i.e., they show that KrF can act as a storage medium even for pulsewidths of ˜1ns. For the chosen pulse, which gives a predicted fusion energy gain of ˜120, the simulations predict the FTF can deliver a total on-target energy of 428kJ, a peak spike power of 385TW, and amplified spontaneous emission prepulse contrast ratios IASE/I<3×10-7 in intensity and FASE/F<1.5×10-5 in fluence. Finally, the paper proposes a front-end pulse shaping technique that combines an optical Kerr gate with cw 248nm light and a 1μm control beam shaped by advanced fiber optic technology, such as the one used in the National Ignition Facility (NIF) laser.

The effects of microstructure on propagation of laser-driven radiative heat waves in under-dense high-Z plasma

NASA Astrophysics Data System (ADS)

Colvin, J. D.; Matsukuma, H.; Brown, K. C.; Davis, J. F.; Kemp, G. E.; Koga, K.; Tanaka, N.; Yogo, A.; Zhang, Z.; Nishimura, H.; Fournier, K. B.

2018-03-01

This work was motivated by previous findings that the measured laser-driven heat front propagation velocity in under-dense TiO2/SiO2 foams is slower than the simulated one [Pérez et al., Phys. Plasmas 21, 023102 (2014)]. In attempting to test the hypothesis that these differences result from effects of the foam microstructure, we designed and conducted an experiment on the GEKKO laser using an x-ray streak camera to compare the heat front propagation velocity in "equivalent" gas and foam targets, that is, targets that have the same initial density, atomic weight, and average ionization state. We first discuss the design and the results of this comparison experiment. To supplement the x-ray streak camera data, we designed and conducted an experiment on the Trident laser using a new high-resolution, time-integrated, spatially resolved crystal spectrometer to image the Ti K-shell spectrum along the laser-propagation axis in an under-dense TiO2/SiO2 foam cylinder. We discuss the details of the design of this experiment, and present the measured Ti K-shell spectra compared to the spectra simulated with a detailed superconfiguration non-LTE atomic model for Ti incorporated into a 2D radiation hydrodynamic code. We show that there is indeed a microstructure effect on heat front propagation in under-dense foams, and that the measured heat front velocities in the TiO2/SiO2 foams are consistent with the analytical model of Gus'kov et al. [Phys. Plasmas 18, 103114 (2011)].

The integration of laser communication and ranging

NASA Astrophysics Data System (ADS)

Xu, Mengmeng; Sun, Jianfeng; Zhou, Yu; Zhang, Bo; Zhang, Guo; Li, Guangyuan; He, Hongyu; Lao, Chenzhe

2017-08-01

The method to realize the integration of laser communication and ranging is proposed in this paper. In the transmitter of two places, the ranging codes with uniqueness, good autocorrelation and cross-correlation properties are embed in the communication data and the encoded with the communication data to realize serial communication. And then the encoded data are modulated and send to each other, which can realize high speed two one-way laser communication. At the receiver, we can get the received ranging code after the demodulation, decoding and clock recovery. The received ranging codes and the local ranging codes do the autocorrelation to get a roughly range, while the phase difference between the local clock and the recovery clock to achieve the precision of the distance.

Consistency analysis on laser signal in laser guided weapon simulation

NASA Astrophysics Data System (ADS)

Yin, Ruiguang; Zhang, Wenpan; Guo, Hao; Gan, Lin

2015-10-01

The hardware-in-the-loop simulation is widely used in laser semi-active guidance weapon experiments, the authenticity of the laser guidance signal is the key problem of reliability. In order to evaluate the consistency of the laser guidance signal, this paper analyzes the angle of sight, laser energy density, laser spot size, atmospheric back scattering, sun radiation and SNR by comparing the different working state between actual condition and hardware-in-the-loop simulation. Based on measured data, mathematical simulation and optical simulation result, laser guidance signal effects on laser seeker are determined. By using Monte Carlo method, the laser guided weapon trajectory and impact point distribution are obtained, the influence of the systematic error are analyzed. In conclusion it is pointed out that the difference between simulation system and actual system has little influence in normal guidance, has great effect on laser jamming. The research is helpful to design and evaluation of laser guided weapon simulation.

Injection of externally produced kinetic electrons into a self-guided laser wakefield accelerator

NASA Astrophysics Data System (ADS)

Pollock, Bradley; Ralph, Joseph; Albert, Felicie; Shaw, Jessica; Clayton, Christopher; Marsh, Ken; Joshi, Chan; Mori, Warren; Kesler, Leigh; Mills, Sarah; Severson, Brian; Rigby, Alexandra; Glenzer, Siegfried

2012-10-01

A two-stage laser wakefield accelerator is being developed at the Lawrence Livermore National Laboratory using the Callisto laser system. The first stage is a high density (˜10^19 cm-3), 5 mm He gas jet plasma which is driven by 30 TW of 800 nm laser light focused to an a0˜ 2. The <100 MeV electrons produced in this stage are deflected by a 0.5 T dipole magnet onto the axis of the second stage, which is a low density (˜10^18 cm-3), 15 mm He gas cell driven by 200 TW of 800 nm light also focused to an a0˜ 2; no additional electrons are trapped in this stage. Electrons injected into the second stage can then be further accelerated to higher energy without increasing the energy spread. Measurements of the transmitted laser profile and spectrum from the second stage indicate that the laser pulse is self-guided throughout the gas cell and that a strong wake is driven. These results compare well with particle-in-cell (PIC) simulations performed with the code OSIRIS. This work was performed under the auspices of the United States Department of Energy by the Lawrence Livermore National Laboratory under contract No. DE-AC52-07NA-27344.

The use of lasers for achieving extreme conditions of matter, and fusion

NASA Astrophysics Data System (ADS)

Roberts, P. D.

2012-05-01

Since the early'70s AWE has focussed on indirect drive as a means of accessing high energy density regimes. We give a brief historical perspective of this work and the rationale for the construction of the ORION laser. This laser is currently in commissioning and is scheduled to commence experiments in 2012. The ORION laser is configured to provide long pulses (~ 1ns) with a high degree of pulse shape flexibility, together with synchronised short pulse (~1ps) irradiation. The paper describes how this combination should enable pressures in excess of 1 Gb and temperatures of greater than 500 eV to be achieved. The ability to access and diagnose such conditions has applications in many fields; examples are given in planetary science, astrophysics and inertial fusion energy. For these applications we first describe the approach to measuring equation of state and opacity properties in the high energy density regime. Such properties are then incorporated into integrated computer simulation codes and validated against laser experiments, some of which have been conducted recently at the OMEGA laser at the University of Rochester. The paper concludes with a discussion of inertial fusion energy and the new high energy density regimes that this would access, if successful.

Modeling dynamic plasmas driven by ultraintense nano-focused x-ray laser pulses in solid iron targets

NASA Astrophysics Data System (ADS)

Royle, Ryan; Sentoku, Yasuhiko; Mancini, Roberto

2017-10-01

The hard x-ray free electron laser has proven to be a valuable tool for high energy density (HED) physics as it is able to produce well-characterized samples of HED matter at exactly solid density and homogeneous temperatures. However, if the x-ray pulses are focused to sub-micron spot sizes, where peak intensities can exceed 1020 W/cm2, the plasmas driven by sources of non-thermal photoelectrons and Auger electrons can be highly dynamic and so cannot be modeled by atomic kinetics or fluid codes. We apply the 2D/3D particle-in-cell code, PICLS-which has been extended with numerous physics models to enable the simulation of XFEL-driven plasmas-to the modeling of such dynamic plasmas driven by nano-focused XFEL pulses in solid iron targets. In the case of the smallest focal spot investigated of just 100 nm in diameter, keV plasmas induce strong radial E-fields that accelerate keV ions radially as well as sheath fields that accelerate surface ions to hundreds of keV. The heated spot, which is initially larger than the laser spot due to the kinetic nature of the fast Auger electrons, expands as ion and electron waves propagate radially, leaving a low density region along the laser axis. This research was supported by the US DOE-OFES under Grant No. DE-SC0008827, the DOE-NNSA under Grant No. DE-NA0002075, and the JSPS KAKENHI under Grant No. JP15K21767.

Diagnosis of warm dense conditions in foil targets heated by intense femtosecond laser pulses using Kα imaging spectroscopy

DOE PAGES

Bae, L. J.; Zastrau, U.; Chung, H. -K.; ...

2018-03-01

Warm dense conditions in titanium foils irradiated with intense femtosecond laser pulses are diagnosed using an x-ray imaging spectroscopy technique. The line shapes of radially resolved titanium Kα spectra are measured with a toroidally bent GaAs crystal and an x-ray charge-coupled device. Measured spectra are compared with the K-shell emissions modeled using an atomic kinetics – spectroscopy simulation code. Kα line shapes are strongly affected by warm (5-40 eV) bulk electron temperatures and imply multiple temperature distributions in the targets. Finally, the spatial distribution of temperature is dependent on the target thickness, and a thin target shows an advantage tomore » generate uniform warm dense conditions in a large area.« less

Diagnosis of warm dense conditions in foil targets heated by intense femtosecond laser pulses using Kα imaging spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bae, L. J.; Zastrau, U.; Chung, H. -K.

Warm dense conditions in titanium foils irradiated with intense femtosecond laser pulses are diagnosed using an x-ray imaging spectroscopy technique. The line shapes of radially resolved titanium Kα spectra are measured with a toroidally bent GaAs crystal and an x-ray charge-coupled device. Measured spectra are compared with the K-shell emissions modeled using an atomic kinetics – spectroscopy simulation code. Kα line shapes are strongly affected by warm (5-40 eV) bulk electron temperatures and imply multiple temperature distributions in the targets. Finally, the spatial distribution of temperature is dependent on the target thickness, and a thin target shows an advantage tomore » generate uniform warm dense conditions in a large area.« less

Development of Spectral and Atomic Models for Diagnosing Energetic Particle Characteristics in Fast Ignition Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacFarlane, Joseph J.; Golovkin, I. E.; Woodruff, P. R.

2009-08-07

This Final Report summarizes work performed under DOE STTR Phase II Grant No. DE-FG02-05ER86258 during the project period from August 2006 to August 2009. The project, “Development of Spectral and Atomic Models for Diagnosing Energetic Particle Characteristics in Fast Ignition Experiments,” was led by Prism Computational Sciences (Madison, WI), and involved collaboration with subcontractors University of Nevada-Reno and Voss Scientific (Albuquerque, NM). In this project, we have: Developed and implemented a multi-dimensional, multi-frequency radiation transport model in the LSP hybrid fluid-PIC (particle-in-cell) code [1,2]. Updated the LSP code to support the use of accurate equation-of-state (EOS) tables generated by Prism’smore » PROPACEOS [3] code to compute more accurate temperatures in high energy density physics (HEDP) plasmas. Updated LSP to support the use of Prism’s multi-frequency opacity tables. Generated equation of state and opacity data for LSP simulations for several materials being used in plasma jet experimental studies. Developed and implemented parallel processing techniques for the radiation physics algorithms in LSP. Benchmarked the new radiation transport and radiation physics algorithms in LSP and compared simulation results with analytic solutions and results from numerical radiation-hydrodynamics calculations. Performed simulations using Prism radiation physics codes to address issues related to radiative cooling and ionization dynamics in plasma jet experiments. Performed simulations to study the effects of radiation transport and radiation losses due to electrode contaminants in plasma jet experiments. Updated the LSP code to generate output using NetCDF to provide a better, more flexible interface to SPECT3D [4] in order to post-process LSP output. Updated the SPECT3D code to better support the post-processing of large-scale 2-D and 3-D datasets generated by simulation codes such as LSP. Updated atomic physics modeling to provide for more comprehensive and accurate atomic databases that feed into the radiation physics modeling (spectral simulations and opacity tables). Developed polarization spectroscopy modeling techniques suitable for diagnosing energetic particle characteristics in HEDP experiments. A description of these items is provided in this report. The above efforts lay the groundwork for utilizing the LSP and SPECT3D codes in providing simulation support for DOE-sponsored HEDP experiments, such as plasma jet and fast ignition physics experiments. We believe that taken together, the LSP and SPECT3D codes have unique capabilities for advancing our understanding of the physics of these HEDP plasmas. Based on conversations early in this project with our DOE program manager, Dr. Francis Thio, our efforts emphasized developing radiation physics and atomic modeling capabilities that can be utilized in the LSP PIC code, and performing radiation physics studies for plasma jets. A relatively minor component focused on the development of methods to diagnose energetic particle characteristics in short-pulse laser experiments related to fast ignition physics. The period of performance for the grant was extended by one year to August 2009 with a one-year no-cost extension, at the request of subcontractor University of Nevada-Reno.« less

Theoretical analysis and simulation of the influence of self-bunching effects and longitudinal space charge effects on the propagation of keV electron bunch produced by a novel S-band Micro-Pulse electron Gun

NASA Astrophysics Data System (ADS)

Zhao, Jifei; Lu, Xiangyang; Zhou, Kui; Yang, Ziqin; Yang, Deyu; Luo, Xing; Tan, Weiwei; Yang, Yujia

2016-06-01

As an important electron source, Micro-Pulse electron Gun (MPG) which is qualified for producing high average current, short pulse, low emittance electron bunches steadily holds promise to use as an electron source of Coherent Smith-Purcell Radiation (CSPR), Free Electron Laser (FEL). The stable output of S-band MPG has been achieved in many labs. To establish reliable foundation for the future application of it, the propagation of picosecond electron bunch produced by MPG should be studied in detail. In this article, the MPG which was working on the rising stage of total effective Secondary Electron Yield (SEY) curve was introduced. The self-bunching mechanism was discussed in depth both in the multipacting amplifying state and the steady working state. The bunch length broadening induced by the longitudinal space-charge (SC) effects was investigated by different theoretical models in different regions. The 2D PIC codes MAGIC and beam dynamic codes TraceWin simulations were also performed in the propagation. The result shows an excellent agreement between the simulation and the theoretical analysis for bunch length evolution.

Extreme ultraviolet emission and confinement of tin plasmas in the presence of a magnetic field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roy, Amitava, E-mail: roy@fzu.cz, E-mail: aroy@barc.gov.in; HiLASE Project, Department of Diode-pumped Lasers, Institute of Physics of the ASCR, Na Slovance 2, 18221 Prague; Murtaza Hassan, Syed

2014-05-15

We investigated the role of a guiding magnetic field on extreme ultraviolet (EUV) and ion emission from a laser produced Sn plasma for various laser pulse duration and intensity. For producing plasmas, planar slabs of pure Sn were irradiated with 1064 nm, Nd:YAG laser pulses with varying pulse duration (5–15 ns) and intensity. A magnetic trap was fabricated with the use of two neodymium permanent magnets which provided a magnetic field strength ∼0.5 T along the plume expansion direction. Our results indicate that the EUV conversion efficiency do not depend significantly on applied axial magnetic field. Faraday Cup ion analysis of Sn plasmamore » show that the ion flux reduces by a factor of ∼5 with the application of an axial magnetic field. It was found that the plasma plume expand in the lateral direction with peak velocity measured to be ∼1.2 cm/μs and reduced to ∼0.75 cm/μs with the application of an axial magnetic field. The plume expansion features recorded using fast photography in the presence and absence of 0.5 T axial magnetic field are simulated using particle-in-cell code. Our simulation results qualitatively predict the plasma behavior.« less

Blast-Wave Generation and Propagation in Rapidly Heated Laser-Irradiated Targets

NASA Astrophysics Data System (ADS)

Ivancic, S. T.; Stillman, C. R.; Nilson, P. M.; Solodov, A. A.; Froula, D. H.

2017-10-01

Time-resolved extreme ultraviolet (XUV) spectroscopy was used to study the creation and propagation of a >100-Mbar blast wave in a target irradiated by an intense (>1018WWcm2 cm2) laser pulse. Blast waves provide a platform to generate immense pressures in the laboratory. A temporal double flash of XUV radiation was observed when viewing the rear side of the target, which is attributed to the emergence of a blast wave following rapid heating by a fast-electron beam generated from the laser pulse. The time-history of XUV emission in the photon energy range of 50 to 200 eV was recorded with an x-ray streak camera with 7-ps temporal resolution. The heating and expansion of the target was simulated with an electron transport code coupled to 1-D radiation-hydrodynamics simulations. The temporal delay between the two flashes measured in a systematic study of target thickness and composition was found to evolve in good agreement with a Sedov-Taylor blast-wave solution. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and Department of Energy Office of Science Award Number DE-SC-0012317.

Surface hardening using cw CO2 laser: laser heat treatment, modelation, and experimental work

NASA Astrophysics Data System (ADS)

Muniz, German; Alum, Jorge

1996-02-01

In the present work are given the results of the application of laser metal surface hardening techniques using a cw carbon dioxide laser as an energy source on steel 65 G. The laser heat treatment results are presented theoretically and experimentally. Continuous wave carbon dioxide laser of 0.6, 0.3, and 0.4 kW were used. A physical model for the descriptions of the thermophysical laser metal interactions process is given and a numerical algorithm is used to solve this problem by means of the LHT code. The results are compared with the corresponding experimental ones and a very good agreement is observed. The LHT code is able to do predictions of transformation hardening by laser heating. These results will be completed with other ones concerning laser alloying and cladding presented in a second paper.

Three-dimensional simulation of beam propagation and heat transfer in static gas Cs DPALs using wave optics and fluid dynamics models

NASA Astrophysics Data System (ADS)

Waichman, Karol; Barmashenko, Boris D.; Rosenwaks, Salman

2017-10-01

Analysis of beam propagation, kinetic and fluid dynamic processes in Cs diode pumped alkali lasers (DPALs), using wave optics model and gasdynamic code, is reported. The analysis is based on a three-dimensional, time-dependent computational fluid dynamics (3D CFD) model. The Navier-Stokes equations for momentum, heat and mass transfer are solved by a commercial Ansys FLUENT solver based on the finite volume discretization technique. The CFD code which solves the gas conservation equations includes effects of natural convection and temperature diffusion of the species in the DPAL mixture. The DPAL kinetic processes in the Cs/He/C2H6 gas mixture dealt with in this paper involve the three lowest energy levels of Cs, (1) 62S1/2, (2) 62P1/2 and (3) 62P3/2. The kinetic processes include absorption due to the 1->3 D2 transition followed by relaxation the 3 to 2 fine structure levels and stimulated emission due to the 2->1 D1 transition. Collisional quenching of levels 2 and 3 and spontaneous emission from these levels are also considered. The gas flow conservation equations are coupled to fast-Fourier-transform algorithm for transverse mode propagation to obtain a solution of the scalar paraxial propagation equation for the laser beam. The wave propagation equation is solved by the split-step beam propagation method where the gain and refractive index in the DPAL medium affect the wave amplitude and phase. Using the CFD and beam propagation models, the gas flow pattern and spatial distributions of the pump and laser intensities in the resonator were calculated for end-pumped Cs DPAL. The laser power, DPAL medium temperature and the laser beam quality were calculated as a function of pump power. The results of the theoretical model for laser power were compared to experimental results of Cs DPAL.

Modeling of a VMJ PV array under Gaussian high intensity laser power beam condition

NASA Astrophysics Data System (ADS)

Eom, Jeongsook; Kim, Gunzung; Park, Yongwan

2018-02-01

The high intensity laser power beaming (HILPB) system is one of the most promising systems in the long-rang wireless power transfer field. The vertical multi-junction photovoltaic (VMJ PV) array converts the HILPB into electricity to power the load or charges a battery. The output power of a VMJ PV array depends mainly on irradiance values of each VMJ PV cells. For simulating an entire VMJ PV array, the irradiance profile of the Gaussian HILPB and the irradiance level of the VMJ PV cell are mathematically modeled first. The VMJ PV array is modeled as a network with dimension m*n, where m represents the number of VMJ PV cells in a column, and n represents the number of VMJ PV cells in a row. In order to validate the results obtained in modeling and simulation, a laboratory setup was developed using 55 VMJ PV array. By using the output power model of VMJ PV array, we can establish an optimal power transmission path by the receiver based on the received signal strength. When the laser beam from multiple transmitters aimed at a VMJ PV array at the same time, the received power is the sum of all energy at a VMJ PV array. The transmitter sends its power characteristics as optically coded laser pulses and powers as HILPB. Using the attenuated power model and output power model of VMJ PV array, the receiver can estimate the maximum receivable powers from the transmitters and select optimal transmitters.

Modeling the effect of laser heating on the strength and failure of 7075-T6 aluminum

DOE PAGES

Florando, J. N.; Margraf, J. D.; Reus, J. F.; ...

2015-06-06

The effect of rapid laser heating on the response of 7075-T6 aluminum has been characterized using 3-D digital image correlation and a series of thermocouples. The experimental results indicate that as the samples are held under a constant load, the heating from the laser profile causes non-uniform temperature and strain fields, and the strain-rate increases dramatically as the sample nears failure. Simulations have been conducted using the LLNL multi-physics code ALE3D, and compared to the experiments. The strength and failure of the material was modeled using the Johnson–Cook strength and damage models. Here, in order to capture the response, amore » dual-condition criterion was utilized which calibrated one set of parameters to low temperature quasi-static strain rate data, while the other parameter set is calibrated to high temperature high strain rate data. The thermal effects were captured using temperature dependent thermal constants and invoking thermal transport with conduction, convection, and thermal radiation.« less

Research on the optoacoustic communication system for speech transmission by variable laser-pulse repetition rates

NASA Astrophysics Data System (ADS)

Jiang, Hongyan; Qiu, Hongbing; He, Ning; Liao, Xin

2018-06-01

For the optoacoustic communication from in-air platforms to submerged apparatus, a method based on speech recognition and variable laser-pulse repetition rates is proposed, which realizes character encoding and transmission for speech. Firstly, the theories and spectrum characteristics of the laser-generated underwater sound are analyzed; and moreover character conversion and encoding for speech as well as the pattern of codes for laser modulation is studied; lastly experiments to verify the system design are carried out. Results show that the optoacoustic system, where laser modulation is controlled by speech-to-character baseband codes, is beneficial to improve flexibility in receiving location for underwater targets as well as real-time performance in information transmission. In the overwater transmitter, a pulse laser is controlled to radiate by speech signals with several repetition rates randomly selected in the range of one to fifty Hz, and then in the underwater receiver laser pulse repetition rate and data can be acquired by the preamble and information codes of the corresponding laser-generated sound. When the energy of the laser pulse is appropriate, real-time transmission for speaker-independent speech can be realized in that way, which solves the problem of underwater bandwidth resource and provides a technical approach for the air-sea communication.

SPECT3D - A multi-dimensional collisional-radiative code for generating diagnostic signatures based on hydrodynamics and PIC simulation output

NASA Astrophysics Data System (ADS)

MacFarlane, J. J.; Golovkin, I. E.; Wang, P.; Woodruff, P. R.; Pereyra, N. A.

2007-05-01

SPECT3D is a multi-dimensional collisional-radiative code used to post-process the output from radiation-hydrodynamics (RH) and particle-in-cell (PIC) codes to generate diagnostic signatures (e.g. images, spectra) that can be compared directly with experimental measurements. This ability to post-process simulation code output plays a pivotal role in assessing the reliability of RH and PIC simulation codes and their physics models. SPECT3D has the capability to operate on plasmas in 1D, 2D, and 3D geometries. It computes a variety of diagnostic signatures that can be compared with experimental measurements, including: time-resolved and time-integrated spectra, space-resolved spectra and streaked spectra; filtered and monochromatic images; and X-ray diode signals. Simulated images and spectra can include the effects of backlighters, as well as the effects of instrumental broadening and time-gating. SPECT3D also includes a drilldown capability that shows where frequency-dependent radiation is emitted and absorbed as it propagates through the plasma towards the detector, thereby providing insights on where the radiation seen by a detector originates within the plasma. SPECT3D has the capability to model a variety of complex atomic and radiative processes that affect the radiation seen by imaging and spectral detectors in high energy density physics (HEDP) experiments. LTE (local thermodynamic equilibrium) or non-LTE atomic level populations can be computed for plasmas. Photoabsorption rates can be computed using either escape probability models or, for selected 1D and 2D geometries, multi-angle radiative transfer models. The effects of non-thermal (i.e. non-Maxwellian) electron distributions can also be included. To study the influence of energetic particles on spectra and images recorded in intense short-pulse laser experiments, the effects of both relativistic electrons and energetic proton beams can be simulated. SPECT3D is a user-friendly software package that runs on Windows, Linux, and Mac platforms. A parallel version of SPECT3D is supported for Linux clusters for large-scale calculations. We will discuss the major features of SPECT3D, and present example results from simulations and comparisons with experimental data.

Experiments and simulations of Richtmyer-Meshkov Instability with measured,volumetric initial conditions

NASA Astrophysics Data System (ADS)

Sewell, Everest; Ferguson, Kevin; Jacobs, Jeffrey; Greenough, Jeff; Krivets, Vitaliy

2016-11-01

We describe experiments of single-shock Richtmyer-Meskhov Instability (RMI) performed on the shock tube apparatus at the University of Arizona in which the initial conditions are volumetrically imaged prior to shock wave arrival. Initial perturbations play a major role in the evolution of RMI, and previous experimental efforts only capture a single plane of the initial condition. The method presented uses a rastered laser sheet to capture additional images throughout the depth of the initial condition immediately before the shock arrival time. These images are then used to reconstruct a volumetric approximation of the experimental perturbation. Analysis of the initial perturbations is performed, and then used as initial conditions in simulations using the hydrodynamics code ARES, developed at Lawrence Livermore National Laboratory (LLNL). Experiments are presented and comparisons are made with simulation results.

Rise time of proton cut-off energy in 2D and 3D PIC simulations

NASA Astrophysics Data System (ADS)

Babaei, J.; Gizzi, L. A.; Londrillo, P.; Mirzanejad, S.; Rovelli, T.; Sinigardi, S.; Turchetti, G.

2017-04-01

The Target Normal Sheath Acceleration regime for proton acceleration by laser pulses is experimentally consolidated and fairly well understood. However, uncertainties remain in the analysis of particle-in-cell simulation results. The energy spectrum is exponential with a cut-off, but the maximum energy depends on the simulation time, following different laws in two and three dimensional (2D, 3D) PIC simulations so that the determination of an asymptotic value has some arbitrariness. We propose two empirical laws for the rise time of the cut-off energy in 2D and 3D PIC simulations, suggested by a model in which the proton acceleration is due to a surface charge distribution on the target rear side. The kinetic energy of the protons that we obtain follows two distinct laws, which appear to be nicely satisfied by PIC simulations, for a model target given by a uniform foil plus a contaminant layer that is hydrogen-rich. The laws depend on two parameters: the scaling time, at which the energy starts to rise, and the asymptotic cut-off energy. The values of the cut-off energy, obtained by fitting 2D and 3D simulations for the same target and laser pulse configuration, are comparable. This suggests that parametric scans can be performed with 2D simulations since 3D ones are computationally very expensive, delegating their role only to a correspondence check. In this paper, the simulations are carried out with the PIC code ALaDyn by changing the target thickness L and the incidence angle α, with a fixed a0 = 3. A monotonic dependence, on L for normal incidence and on α for fixed L, is found, as in the experimental results for high temporal contrast pulses.

UV Lidar Receiver Analysis for Tropospheric Sensing of Ozone

NASA Technical Reports Server (NTRS)

Pliutau, Denis; DeYoung, Russell J.

2013-01-01

A simulation of a ground based Ultra-Violet Differential Absorption Lidar (UV-DIAL) receiver system was performed under realistic daytime conditions to understand how range and lidar performance can be improved for a given UV pulse laser energy. Calculations were also performed for an aerosol channel transmitting at 3 W. The lidar receiver simulation studies were optimized for the purpose of tropospheric ozone measurements. The transmitted lidar UV measurements were from 285 to 295 nm and the aerosol channel was 527-nm. The calculations are based on atmospheric transmission given by the HITRAN database and the Modern Era Retrospective Analysis for Research and Applications (MERRA) meteorological data. The aerosol attenuation is estimated using both the BACKSCAT 4.0 code as well as data collected during the CALIPSO mission. The lidar performance is estimated for both diffuseirradiance free cases corresponding to nighttime operation as well as the daytime diffuse scattered radiation component based on previously reported experimental data. This analysis presets calculations of the UV-DIAL receiver ozone and aerosol measurement range as a function of sky irradiance, filter bandwidth and laser transmitted UV and 527-nm energy

Performance modeling of the effects of aperture phase error, turbulence, and thermal blooming on tiled subaperture systems

NASA Astrophysics Data System (ADS)

Leakeas, Charles L.; Capehart, Shay R.; Bartell, Richard J.; Cusumano, Salvatore J.; Whiteley, Matthew R.

2011-06-01

Laser weapon systems comprised of tiled subapertures are rapidly emerging in importance in the directed energy community. Performance models of these laser weapon systems have been developed from numerical simulations of a high fidelity wave-optics code called WaveTrain which is developed by MZA Associates. System characteristics such as mutual coherence, differential jitter, and beam quality rms wavefront error are defined for a focused beam on the target. Engagement scenarios are defined for various platform and target altitudes, speeds, headings, and slant ranges along with the natural wind speed and heading. Inputs to the performance model include platform and target height and velocities, Fried coherence length, Rytov number, isoplanatic angle, thermal blooming distortion number, Greenwood and Tyler frequencies, and atmospheric transmission. The performance model fit is based on power-in-the-bucket (PIB) values against the PIB from the simulation results for the vacuum diffraction-limited spot size as the bucket. The goal is to develop robust performance models for aperture phase error, turbulence, and thermal blooming effects in tiled subaperture systems.

Start-Up of FEL Oscillator from Shot Noise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, V.; Krishnagopal, S.; Fawley, W.M.

In free-electron laser (FEL) oscillators, as inself-amplified spontaneous emission (SASE) FELs, the buildup of cavitypower starts from shot noise resulting from the discreteness ofelectronic charge. It is important to do the start-up analysis for thebuild-up of cavity power in order to fix the macropulse width from theelectron accelerator such that the system reaches saturation. In thispaper, we use the time-dependent simulation code GINGER [1]toperformthis analysis. We present results of this analysis for theparameters of the Compact Ultrafast TErahertz FEL (CUTE-FEL) [2]beingbuilt atRRCAT.

Three- and Two- Dimensional Simulations of Re-shock Experiments at High Energy Densities at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Wang, Ping; Raman, Kumar; MacLaren, Stephan; Huntington, Channing; Nagel, Sabrina

2016-10-01

We present simulations of recent high-energy-density (HED) re-shock experiments on the National Ignition Facility (NIF). The experiments study the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instability growth that occurs after successive shocks transit a sinusoidally-perturbed interface between materials of different densities. The shock tube is driven at one or both ends using indirect-drive laser cavities or hohlraums. X-ray area-backlit imaging is used to visualize the growth at different times. Our simulations are done with the three-dimensional, radiation hydrodynamics code ARES, developed at LLNL. We show the instabilitygrowth rate, inferred from the experimental radiographs, agrees well with our 2D and 3D simulations. We also discuss some 3D geometrical effects, suggested by our simulations, which could deteriorate the images at late times, unless properly accounted for in the experiment design. Work supported by U.S. Department of Energy under Contract DE- AC52-06NA27279. LLNL-ABS-680789.

The effect of shot noise on the start up of the fundamental and harmonics in free-electron lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freund, H. P.; Miner, W. H. Jr.; Giannessi, L.

2008-12-15

The problem of radiation start up in free-electron lasers (FELs) is important in the simulation of virtually all FEL configurations including oscillators and amplifiers in both seeded master oscillator power amplifier (MOPA) and self-amplified spontaneous emission (SASE) modes. Both oscillators and SASE FELs start up from spontaneous emission due to shot noise on the electron beam, which arises from the random fluctuations in the phase distribution of the electrons. The injected power in a MOPA is usually large enough to overwhelm the shot noise. However, this noise must be treated correctly in order to model the initial start up ofmore » the harmonics. In this paper, we discuss and compare two different shot noise models that are implemented in both one-dimensional wiggler-averaged (PERSEO) and non-wiggler-averaged (MEDUSA1D) simulation codes, and a three-dimensional non-wiggler-averaged (MEDUSA) formulation. These models are compared for examples describing both SASE and MOPA configurations in one dimension, in steady-state, and time-dependent simulations. Remarkable agreement is found between PERSEO and MEDUSA1D for the evolution of the fundamental and harmonics. In addition, three-dimensional correction factors have been included in the MEDUSA1D and PERSEO, which show reasonable agreement with MEDUSA for a sample MOPA in steady-state and time-dependent simulations.« less

Computer modeling of pulsed CO2 lasers for lidar applications

NASA Technical Reports Server (NTRS)

Spiers, Gary D.; Smithers, Martin E.; Murty, Rom

1991-01-01

The experimental results will enable a comparison of the numerical code output with experimental data. This will ensure verification of the validity of the code. The measurements were made on a modified commercial CO2 laser. Results are listed as following. (1) The pulse shape and energy dependence on gas pressure were measured. (2) The intrapulse frequency chirp due to plasma and laser induced medium perturbation effects were determined. A simple numerical model showed quantitative agreement with these measurements. The pulse to pulse frequency stability was also determined. (3) The dependence was measured of the laser transverse mode stability on cavity length. A simple analysis of this dependence in terms of changes to the equivalent fresnel number and the cavity magnification was performed. (4) An analysis was made of the discharge pulse shape which enabled the low efficiency of the laser to be explained in terms of poor coupling of the electrical energy into the vibrational levels. And (5) the existing laser resonator code was changed to allow it to run on the Cray XMP under the new operating system.

Study of Linear and Nonlinear Waves in Plasma Crystals Using the Box_Tree Code

NASA Astrophysics Data System (ADS)

Qiao, K.; Hyde, T.; Barge, L.

Dusty plasma systems play an important role in both astrophysical and planetary environments (protostellar clouds, planetary ring systems and magnetospheres, cometary environments) and laboratory settings (plasma processing or nanofabrication). Recent research has focussed on defining (both theoretically and experimentally) the different types of wave mode propagations, which are possible within plasma crystals. This is an important topic since several of the fundamental quantities for characterizing such crystals can be obtained directly from an analysis of the wave propagation/dispersion. This paper will discuss a num rical model fore 2D-monolayer plasma crystals, which was established using a modified box tree code. Different wave modes were examined by adding a time dependent potential to the code designed to simulate a laser radiation perturbation as has been applied in many experiments. Both linear waves (for example, longitudinal and transverse dust lattice waves) and nonlinear waves (solitary waves) are examined. The output data will also be compared with the results of corresponding experiments and discussed.

NRA8-21 Cycle 2 RBCC Turbopump Risk Reduction

NASA Technical Reports Server (NTRS)

Ferguson, Thomas V.; Williams, Morgan; Marcu, Bogdan

2004-01-01

This project was composed of three sub-tasks. The objective of the first task was to use the CFD code INS3D to generate both on- and off-design predictions for the consortium optimized impeller flowfield. The results of the flow simulations are given in the first section. The objective of the second task was to construct a turbomachinery testing database comprised of measurements made on several different impellers, an inducer and a diffuser. The data was in the form of static pressure measurements as well as laser velocimeter measurements of velocities and flow angles within the stated components. Several databases with this information were created for these components. The third subtask objective was two-fold: first, to validate the Enigma CFD code for pump diffuser analysis, and secondly, to perform steady and unsteady analyses on some wide flow range diffuser concepts using Enigma. The code was validated using the consortium optimized impeller database and then applied to two different concepts for wide flow diffusers.

Characterization of the ELIMED Permanent Magnets Quadrupole system prototype with laser-driven proton beams

NASA Astrophysics Data System (ADS)

Schillaci, F.; Pommarel, L.; Romano, F.; Cuttone, G.; Costa, M.; Giove, D.; Maggiore, M.; Russo, A. D.; Scuderi, V.; Malka, V.; Vauzour, B.; Flacco, A.; Cirrone, G. A. P.

2016-07-01

Laser-based accelerators are gaining interest in recent years as an alternative to conventional machines [1]. In the actual ion acceleration scheme, energy and angular spread of the laser-driven beams are the main limiting factors for beam applications and different solutions for dedicated beam-transport lines have been proposed [2,3]. In this context a system of Permanent Magnet Quadrupoles (PMQs) has been realized [2] by INFN-LNS (Laboratori Nazionali del Sud of the Instituto Nazionale di Fisica Nucleare) researchers, in collaboration with SIGMAPHI company in France, to be used as a collection and pre-selection system for laser driven proton beams. This system is meant to be a prototype to a more performing one [3] to be installed at ELI-Beamlines for the collection of ions. The final system is designed for protons and carbons up to 60 MeV/u. In order to validate the design and the performances of this large bore, compact, high gradient magnetic system prototype an experimental campaign have been carried out, in collaboration with the group of the SAPHIR experimental facility at LOA (Laboratoire d'Optique Appliquée) in Paris using a 200 TW Ti:Sapphire laser system. During this campaign a deep study of the quadrupole system optics has been performed, comparing the results with the simulation codes used to determine the setup of the PMQ system and to track protons with realistic TNSA-like divergence and spectrum. Experimental and simulation results are good agreement, demonstrating the possibility to have a good control on the magnet optics. The procedure used during the experimental campaign and the most relevant results are reported here.

Energy and Technology Review

NASA Astrophysics Data System (ADS)

Poggio, Andrew J.

1988-10-01

This issue of Energy and Technology Review contains: Neutron Penumbral Imaging of Laser-Fusion Targets--using our new penumbral-imaging diagnostic, we have obtained the first images that can be used to measure directly the deuterium-tritium burn region in laser-driven fusion targets; Computed Tomography for Nondestructive Evaluation--various computed tomography systems and computational techniques are used in nondestructive evaluation; Three-Dimensional Image Analysis for Studying Nuclear Chromatin Structure--we have developed an optic-electronic system for acquiring cross-sectional views of cell nuclei, and computer codes to analyze these images and reconstruct the three-dimensional structures they represent; Imaging in the Nuclear Test Program--advanced techniques produce images of unprecedented detail and resolution from Nevada Test Site data; and Computational X-Ray Holography--visible-light experiments and numerically simulated holograms test our ideas about an X-ray microscope for biological research.

A new airborne laser rangefinder dynamic target simulator for non-stationary environment

NASA Astrophysics Data System (ADS)

Ma, Pengge; Pang, Dongdong; Yi, Yang

2017-11-01

For the non-stationary environment simulation in laser range finder product testing, a new dynamic target simulation system is studied. First of all, the three-pulsed laser ranging principle, laser target signal composition and mathematical representation are introduced. Then, the actual nonstationary working environment of laser range finder is analyzed, and points out that the real sunshine background light clutter and target shielding effect in laser echo become the main influencing factors. After that, the dynamic laser target signal simulation method is given. Eventlly, the implementation of automatic test system based on arbitrary waveform generator is described. Practical application shows that the new echo signal automatic test system can simulate the real laser ranging environment of laser range finder, and is suitable for performance test of products.

Plasma interpenetration study on the Omega laser facility

NASA Astrophysics Data System (ADS)

Le Pape, Sebastien; Divol, Laurent; Ross, Steven; Wilks, Scott; Amendt, Peter; Berzak Hopkins, Laura; Huser, Gael; Moody, John; MacKinnon, Andy; Meezan, Nathan

2016-10-01

The Near Vacuum Campaign on the National Ignition Facility has sparked an interest on the nature of the gold/carbon interface at high velocity, high electron temperature, low-electron density. Indeed radiation-hydrodynamic simulations have been unable to accurately reproduce the experimental shape of the hot spot resulting from implosion driven in Near Vacuum Holhraum. The experimental data are suggesting that the inner beams are freely propagating to the waist of the hohlraum when simulations predict that a density ridge at the gold/carbon interface blocks the inner beams. The discrepancy between experimental data and simulation might be explained by the fluid description of the plasma interface in a rad-hydro code which is probably not valid in when two plasma at high velocity, high temperature are meeting. To test our assumption, we went to the Omega laser facility to study gold/carbon interface in the relevant regime. Time resolved images of the self-emission as well as Thomson scattering data will be presented. For the first time, a transition from a multifluid to a single fluid is observed as plasmas are interacting. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

Model-based engineering for laser weapons systems

NASA Astrophysics Data System (ADS)

Panthaki, Malcolm; Coy, Steve

2011-10-01

The Comet Performance Engineering Workspace is an environment that enables integrated, multidisciplinary modeling and design/simulation process automation. One of the many multi-disciplinary applications of the Comet Workspace is for the integrated Structural, Thermal, Optical Performance (STOP) analysis of complex, multi-disciplinary space systems containing Electro-Optical (EO) sensors such as those which are designed and developed by and for NASA and the Department of Defense. The CometTM software is currently able to integrate performance simulation data and processes from a wide range of 3-D CAD and analysis software programs including CODE VTM from Optical Research Associates and SigFitTM from Sigmadyne Inc. which are used to simulate the optics performance of EO sensor systems in space-borne applications. Over the past year, Comet Solutions has been working with MZA Associates of Albuquerque, NM, under a contract with the Air Force Research Laboratories. This funded effort is a "risk reduction effort", to help determine whether the combination of Comet and WaveTrainTM, a wave optics systems engineering analysis environment developed and maintained by MZA Associates and used by the Air Force Research Laboratory, will result in an effective Model-Based Engineering (MBE) environment for the analysis and design of laser weapons systems. This paper will review the results of this effort and future steps.

Nanosecond laser pulses for mimicking thermal effects on nanostructured tungsten-based materials

NASA Astrophysics Data System (ADS)

Besozzi, E.; Maffini, A.; Dellasega, D.; Russo, V.; Facibeni, A.; Pazzaglia, A.; Beghi, M. G.; Passoni, M.

2018-03-01

In this work, we exploit nanosecond laser irradiation as a compact solution for investigating the thermomechanical behavior of tungsten materials under extreme thermal loads at the laboratory scale. Heat flux factor thresholds for various thermal effects, such as melting, cracking and recrystallization, are determined under both single and multishot experiments. The use of nanosecond lasers for mimicking thermal effects induced on W by fusion-relevant thermal loads is thus validated by direct comparison of the thresholds obtained in this work and the ones reported in the literature for electron beams and millisecond laser irradiation. Numerical simulations of temperature and thermal stress performed on a 2D thermomechanical code are used to predict the heat flux factor thresholds of the different thermal effects. We also investigate the thermal effect thresholds of various nanostructured W coatings. These coatings are produced by pulsed laser deposition, mimicking W coatings in tokamaks and W redeposited layers. All the coatings show lower damage thresholds with respect to bulk W. In general, thresholds decrease as the porosity degree of the materials increases. We thus propose a model to predict these thresholds for coatings with various morphologies, simply based on their porosity degree, which can be directly estimated by measuring the variation of the coating mass density with respect to that of the bulk.

Conceptual design of fast-ignition laser fusion reactor FALCON-D

NASA Astrophysics Data System (ADS)

Goto, T.; Someya, Y.; Ogawa, Y.; Hiwatari, R.; Asaoka, Y.; Okano, K.; Sunahara, A.; Johzaki, T.

2009-07-01

A new conceptual design of the laser fusion power plant FALCON-D (Fast-ignition Advanced Laser fusion reactor CONcept with a Dry wall chamber) has been proposed. The fast-ignition method can achieve sufficient fusion gain for a commercial operation (~100) with about 10 times smaller fusion yield than the conventional central ignition method. FALCON-D makes full use of this property and aims at designing with a compact dry wall chamber (5-6 m radius). 1D/2D simulations by hydrodynamic codes showed a possibility of achieving sufficient gain with a laser energy of 400 kJ, i.e. a 40 MJ target yield. The design feasibility of the compact dry wall chamber and the solid breeder blanket system was shown through thermomechanical analysis of the dry wall and neutronics analysis of the blanket system. Moderate electric output (~400 MWe) can be achieved with a high repetition (30 Hz) laser. This dry wall reactor concept not only reduces several difficulties associated with a liquid wall system but also enables a simple cask maintenance method for the replacement of the blanket system, which can shorten the maintenance period. The basic idea of the maintenance method for the final optics system has also been proposed. Some critical R&D issues required for this design are also discussed.

All-optical spin switching: A new frontier in femtomagnetism — A short review and a simple theory

NASA Astrophysics Data System (ADS)

Zhang, G. P.; Latta, T.; Babyak, Z.; Bai, Y. H.; George, Thomas F.

2016-08-01

Using an ultrafast laser pulse to manipulate the spin degree of freedom has broad technological appeal. It allows one to control the spin dynamics on a femtosecond time scale. The discipline, commonly called femtomagnetism, started with the pioneering experiment by Beaurepaire and coworkers in 1996, who showed subpicosecond demagnetization occurs in magnetic Ni thin films. This finding has motivated extensive research worldwide. All-optical helicity-dependent spin switching (AO-HDS) represents a new frontier in femtomagnetism, where a single ultrafast laser pulse can permanently switch spin without any assistance from a magnetic field. This review summarizes some of the crucial aspects of this new discipline: key experimental findings, leading mechanisms, controversial issues, and possible future directions. The emphasis is on our latest investigation. We first develop the all-optical spin switching (AOS) rule that determines how the switchability depends on the light helicity. This rule allows one to understand microscopically how the spin is reversed and why the circularly polarized light appears more powerful than the linearly polarized light. Then we invoke our latest spin-orbit coupled harmonic oscillator model to simulate single spin reversal. We consider both continuous wave (cw) excitation and pulsed laser excitation. The results are in a good agreement with the experimental result (a MatLab code is available upon request from the author). We then extend the code to include the exchange interaction among different spin sites. We show where the “inverse-Faraday field” comes from and how the laser affects the spin reversal nonlinearly. Our hope is that this review will motivate new experimental and theoretical investigations and discussions.

Particle dynamics and pair production in tightly focused standing wave

NASA Astrophysics Data System (ADS)

Jirka, M.; Klimo, O.; Vranić, M.; Weber, S.; Korn, G.

2017-05-01

With the advent of 10 PW laser facilities, new regimes of laser-matter interaction are opening since effects of quantum electrodynamics, such as electron-positron pair production and cascade development, start to be important. The dynamics of light charged particles, such as electrons and positrons, is affected by the radiation reaction force. This effect can strongly influence the interaction of intense laser pulses with matter since it lowers the energy of emitting particles and transforms their energy to the gamma radiation. Consequently, electron-positron pairs can be generated via Breit-Wheeler process. To study this new regime of interaction, numerical simulations are required. With their help it is possible to predict and study quantum effects which may occur in future experiments at modern laser facilities. In this work we present results of electron interaction with an intense standing wave formed by two colliding laser pulses. Due to the necessity to achieve ultra intense laser field, the laser beam has to be focused to a μm-diameter spot. Since the paraxial approximation is not valid for tight focusing, the appropriate model describing the tightly focused laser beam has to be employed. In tightly focused laser beam the longitudinal component of the electromagnetic field becomes significant and together with the ponderomotive force they affect the dynamics of interacting electrons and also newly generated Breit-Wheeler electron-positron pairs. Using the Particle-In-Cell code we study electron dynamics, gamma radiation and pair production in such a configuration for linear polarization and different types of targets.

Synthesis of polycaprolactone-titanium oxide multilayer films by nanosecond laser pulses and electrospinning technique for better implant fabrication

NASA Astrophysics Data System (ADS)

Naghshine, Babak B.; Cosman, James A.; Kiani, Amirkianoosh

2016-08-01

In this study, a combination of electrospinning and laser texturing is introduced as a novel method for increasing the biocompatibility of metal implants. Besides having a rough laser treated surface, the implant benefits from the high porosity and better wettability of an electrospun fibrous structure, which is a more favorable environment for cell proliferation. Titanium samples were patterned using a nanosecond laser beam and were placed as collectors in an electrospinning machine. They were then soaked in simulated body fluid for four weeks. Energy Dispersive X-ray and X-Ray Diffraction results indicate significantly more hydroxyapatite formation on laser treated samples with nanoscale fibers deposited on their surface. This shows that having a laser treated surface underneath the fibrous layer can improve short-term biocompatibility even before degradation of fibers. The thermal conductivity of the electrospun layer, measured using a Hot Disk Transient Plane Source instrument and computer code, was shown to be considerably lower than that of titanium and very close to bone. The presence of this layer can therefore be beneficial in making the implant more compatible to a biological medium. In case of dental implants, it was shown that this layer can act as a thermal barrier while a hot beverage is consumed and it can decrease the temperature rise by about 60%, which avoids any possible damage to newly formed cells during the healing period.

Advancing adaptive optics technology: Laboratory turbulence simulation and optimization of laser guide stars

NASA Astrophysics Data System (ADS)

Rampy, Rachel A.

Since Galileo's first telescope some 400 years ago, astronomers have been building ever-larger instruments. Yet only within the last two decades has it become possible to realize the potential angular resolutions of large ground-based telescopes, by using adaptive optics (AO) technology to counter the blurring effects of Earth's atmosphere. And only within the past decade have the development of laser guide stars (LGS) extended AO capabilities to observe science targets nearly anywhere in the sky. Improving turbulence simulation strategies and LGS are the two main topics of my research. In the first part of this thesis, I report on the development of a technique for manufacturing phase plates for simulating atmospheric turbulence in the laboratory. The process involves strategic application of clear acrylic paint onto a transparent substrate. Results of interferometric characterization of the plates are described and compared to Kolmogorov statistics. The range of r0 (Fried's parameter) achieved thus far is 0.2--1.2 mm at 650 nm measurement wavelength, with a Kolmogorov power law. These plates proved valuable at the Laboratory for Adaptive Optics at University of California, Santa Cruz, where they have been used in the Multi-Conjugate Adaptive Optics testbed, during integration and testing of the Gemini Planet Imager, and as part of the calibration system of the on-sky AO testbed named ViLLaGEs (Visible Light Laser Guidestar Experiments). I present a comparison of measurements taken by ViLLaGEs of the power spectrum of a plate and the real sky turbulence. The plate is demonstrated to follow Kolmogorov theory well, while the sky power spectrum does so in a third of the data. This method of fabricating phase plates has been established as an effective and low-cost means of creating simulated turbulence. Due to the demand for such devices, they are now being distributed to other members of the AO community. The second topic of this thesis pertains to understanding and optimizing the laser beacons used to bring AO correction to parts of the sky that lack a naturally bright light source for measuring atmospheric distortion. Long pulse length laser guide stars (LGS) that use fluorescence from the D 2 transition in mesospheric sodium are valuable both due to their high altitude, and because they permit Rayleigh blanking and fratricide avoidance in multiple LGS systems. Bloch equation simulations of sodium-light interactions in Mathematica show that certain spectral formats and pulse lengths (on the order of 30 μs), with high duty cycles (20-50%), should be able to achieve photon returns within 10% of what is seen from continuous wave (CW) excitation. Utilizing this recently developed code (called LGSBloch), I investigated the time dependent characteristics of sodium fluorescence. I then identified the optimal format for the new LGS that will be part of the upgrade to the AO system on the Shane 3 meter telescope at the Lick Observatory. I discuss these results, along with their general applicability to other LGS systems, and provide a brief description of the potential benefits of uplink correction. Predictions from the LGSBloch simulation package are compared to data from currently operating LGS systems. For a CW LGS, the return flux measurements and theory show reasonable agreement, but for short pulse lasers, such as those at the Lick and Keck Observatories, the code seems to be overestimating the data by a factor of 2--3. Several tactics to explicate this discrepancy are explored, such as verifying parameters involved in the measurements and including greater detail in the modeling. Although these efforts were unsuccessful at removing the discrepancy, they illuminated other facets of the problem that deserve further consideration. Use of the sophisticated LGSBloch model has allowed detailed study of the evolution of the energy level populations and other physical effects (e.g. Larmor precession, atomic recoil, and collisions). This has determined formats that will have maximal coupling efficiency of the laser light to the sodium atoms in order to achieve the highest possible return signal per Watt of output power. These quantitative findings allow the astronomical AO community to make rational, physics-based choices of which high-power (and unavoidably high-cost) lasers to procure for implementation in future LGS systems.

Directed high-power THz radiation from transverse laser wakefield excited in an electron density filament

NASA Astrophysics Data System (ADS)

Kalmykov, Serge; Englesbe, Alexander; Elle, Jennifer; Domonkos, Matthew; Schmitt-Sody, Andreas

2017-10-01

A tightly focused femtosecond, weakly relativistic laser pulse partially ionizes the ambient gas, creating a string (a ``filament'') of electron density, locally reducing the nonlinear index and compensating for the self-focusing effect caused by bound electrons. While maintaining the filament over many Rayleigh lengths, the pulse drives inside it a three-dimensional (3D) wave of charge separation - the plasma wake. If the pulse waist size is much smaller than the Langmuir wavelength, electron current in the wake is mostly transverse. Electrons, driven by the wake across the sharp radial boundary of the filament, lose coherence within 2-3 periods of wakefield oscillations, and the wake decays. The laser pulse is thus accompanied by a short-lived, almost aperiodic electron current coupled to the sharp index gradient. The comprehensive 3D hydrodynamic model shows that this structure emits a broad-band THz radiation, with the highest power emitted in the near-forward direction. The THz radiation pattern contains information on wake currents surrounding the laser pulse, thus serving as an all-optical diagnostic tool. The results are tested in cylindrical and full 3D PIC simulations using codes WAKE and EPOCH.

Modeling Laser-Plasma Interactions at Direct-Drive Ignition-Relevant Plasma Conditions at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Solodov, A. A.; Rosenberg, M. J.; Myatt, J. F.; Epstein, R.; Seka, W.; Hohenberger, M.; Short, R. W.; Shaw, J. G.; Regan, S. P.; Froula, D. H.; Radha, P. B.; Bates, J. W.; Schmitt, A. J.; Michel, P.; Moody, J. D.; Ralph, J. E.; Turnbull, D. P.; Barrios, M. A.

2016-10-01

Laser-plasma interaction instabilities, such as two-plasmon decay (TPD) and stimulated Raman scattering (SRS), can be detrimental for direct-drive inertial confinement fusion because of target preheat by generated high-energy electrons. The radiation-hydrodynamics code DRACO has been used to design planar-target experiments that generate plasma and interaction conditions relevant to direct-drive-ignition designs (IL 1015 W / cm 2 , Te > 3 KeV density gradient scale lengths of Ln 600 μm) . The hot-electron temperature of 40to50keV and the fraction of laser energy converted to hot electrons of 0.5to were inferred based on comparing the simulated and experimentally observed x-ray emission when the laser intensity at the quarter-critical surface increased from 6 to 15 ×1014 W / cm 2 . The measured SRS energy was sufficient to explain the observed total energy in hot electrons. Implications for ignition-scale direct-drive experiments and hot-electron preheat mitigation using mid- Z ablators will be discussed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

A FORTRAN code for the calculation of probe volume geometry changes in a laser anemometry system caused by window refraction

NASA Technical Reports Server (NTRS)

Owen, Albert K.

1987-01-01

A computer code was written which utilizes ray tracing techniques to predict the changes in position and geometry of a laser Doppler velocimeter probe volume resulting from refraction effects. The code predicts the position change, changes in beam crossing angle, and the amount of uncrossing that occur when the beams traverse a region with a changed index of refraction, such as a glass window. The code calculates the changes for flat plate, cylinder, general axisymmetric and general surface windows and is currently operational on a VAX 8600 computer system.

Design and performance investigation of LDPC-coded upstream transmission systems in IM/DD OFDM-PONs

NASA Astrophysics Data System (ADS)

Gong, Xiaoxue; Guo, Lei; Wu, Jingjing; Ning, Zhaolong

2016-12-01

In Intensity-Modulation Direct-Detection (IM/DD) Orthogonal Frequency Division Multiplexing Passive Optical Networks (OFDM-PONs), aside from Subcarrier-to-Subcarrier Intermixing Interferences (SSII) induced by square-law detection, the same laser frequency for data sending from Optical Network Units (ONUs) results in ONU-to-ONU Beating Interferences (OOBI) at the receiver. To mitigate those interferences, we design a Low-Density Parity Check (LDPC)-coded and spectrum-efficient upstream transmission system. A theoretical channel model is also derived, in order to analyze the detrimental factors influencing system performances. Simulation results demonstrate that the receiver sensitivity is improved 3.4 dB and 2.5 dB under QPSK and 8QAM, respectively, after 100 km Standard Single-Mode Fiber (SSMF) transmission. Furthermore, the spectrum efficiency can be improved by about 50%.

Improved non-LTE simulation algorithm

NASA Astrophysics Data System (ADS)

Busquet, Michel; Klapisch, Marcel; Colombant, Denis; Fyfe, David; Gardner, John

2008-11-01

The RAdiation Dependent Ionization Model (RADIOM)- a.k.a Busquet's model-[1] has proven its success in simulating non --LTE effects in laser fusion plasmas [2]. This improved algorithm can take into account Auger effect by a new parameter fitted to SCROLL [3] results. It is independent of the photon binning thanks to a projection on a standard grid. It guarantees smoother convergence to LTE. This algorithm has been implemented in a new way in the hydro-code FASTnD. Hydro simulations on the recent subMJ targets[4], with and without non-LTE corrections will be shown. [1] M. Busquet, Phys. Fluids B 5, 4191(1993). [2] D.G. Colombant et al, Phys. Plas. 7,2046 (2000). [3] A. Bar-Shalom, J. Oreg M. Klapisch, J. Quant. Spectr. Rad. Transf. 65 ,43 (2000). [4] S. P. Obenschain, D. G. Colombant, A. J. Schmitt et al., Phys. Plasmas 13, 056320 (2006).

Numerical modeling of laser-driven experiments aiming to demonstrate magnetic field amplification via turbulent dynamo

NASA Astrophysics Data System (ADS)

Tzeferacos, P.; Rigby, A.; Bott, A.; Bell, A. R.; Bingham, R.; Casner, A.; Cattaneo, F.; Churazov, E. M.; Emig, J.; Flocke, N.; Fiuza, F.; Forest, C. B.; Foster, J.; Graziani, C.; Katz, J.; Koenig, M.; Li, C.-K.; Meinecke, J.; Petrasso, R.; Park, H.-S.; Remington, B. A.; Ross, J. S.; Ryu, D.; Ryutov, D.; Weide, K.; White, T. G.; Reville, B.; Miniati, F.; Schekochihin, A. A.; Froula, D. H.; Gregori, G.; Lamb, D. Q.

2017-04-01

The universe is permeated by magnetic fields, with strengths ranging from a femtogauss in the voids between the filaments of galaxy clusters to several teragauss in black holes and neutron stars. The standard model behind cosmological magnetic fields is the nonlinear amplification of seed fields via turbulent dynamo to the values observed. We have conceived experiments that aim to demonstrate and study the turbulent dynamo mechanism in the laboratory. Here, we describe the design of these experiments through simulation campaigns using FLASH, a highly capable radiation magnetohydrodynamics code that we have developed, and large-scale three-dimensional simulations on the Mira supercomputer at the Argonne National Laboratory. The simulation results indicate that the experimental platform may be capable of reaching a turbulent plasma state and determining the dynamo amplification. We validate and compare our numerical results with a small subset of experimental data using synthetic diagnostics.

Experiments and simulations of single shock Richtmeyer-Meshkov Instability with measured, volumetric initial conditions

NASA Astrophysics Data System (ADS)

Sewell, Everest; Ferguson, Kevin; Greenough, Jeffrey; Jacobs, Jeffrey

2014-11-01

We describe new experiments of single shock Richtmeyer-Meshkov Instability (RMI) performed on the shock tube apparatus at the University of Arizona in which the initial conditions are volumetrically imaged prior to shock wave arrival. Initial perturbation plays a major role in the evolution of RMI, and previous experimental efforts only capture a narrow slice of the initial condition. The method presented uses a rastered laser sheet to capture additional images in the depth of the initial condition shortly before the experimental start time. These images are then used to reconstruct a volumetric approximation of the experimental perturbation, which is simulated using the hydrodynamics code ARES, developed at Lawrence Livermore National Laboratory (LLNL). Comparison is made between the time evolution of the interface width and the mixedness ratio measured from the experiments against the predictions from the numerical simulations.

Theoretical analysis and simulation of the influence of self-bunching effects and longitudinal space charge effects on the propagation of keV electron bunch produced by a novel S-band Micro-Pulse electron Gun

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Jifei; Lu, Xiangyang, E-mail: xylu@pku.edu.cn; Yang, Ziqin

As an important electron source, Micro-Pulse electron Gun (MPG) which is qualified for producing high average current, short pulse, low emittance electron bunches steadily holds promise to use as an electron source of Coherent Smith-Purcell Radiation (CSPR), Free Electron Laser (FEL). The stable output of S-band MPG has been achieved in many labs. To establish reliable foundation for the future application of it, the propagation of picosecond electron bunch produced by MPG should be studied in detail. In this article, the MPG which was working on the rising stage of total effective Secondary Electron Yield (SEY) curve was introduced. Themore » self-bunching mechanism was discussed in depth both in the multipacting amplifying state and the steady working state. The bunch length broadening induced by the longitudinal space-charge (SC) effects was investigated by different theoretical models in different regions. The 2D PIC codes MAGIC and beam dynamic codes TraceWin simulations were also performed in the propagation. The result shows an excellent agreement between the simulation and the theoretical analysis for bunch length evolution.« less

Simulation of laser beam reflection at the sea surface modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2013-06-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for the pre-calculation of images for cameras operating in different spectral wavebands (visible, short wave infrared) for a bistatic configuration of laser source and receiver for different atmospheric conditions. In the visible waveband the calculated detected total power of reflected laser light from a 660nm laser source is compared with data collected in a field trial. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser beam reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the view of a camera the sea surface radiance must be calculated for the specific waveband. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). Validation of simulation results is prerequisite before applying the computer simulation to maritime laser applications. For validation purposes data (images and meteorological data) were selected from field measurements, using a 660nm cw-laser diode to produce laser beam reflection at the water surface and recording images by a TV camera. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam.

Temperature field simulation on Ti6Al4V and Inconel718 heated by continuous infrared laser

NASA Astrophysics Data System (ADS)

Wang, Yanshen; Zhang, Zheng; Feng, Weiwei; Wang, Bo; Gai, Yuxian

2014-08-01

Laser assisted machining technology can heat and soften metals, which can be used for improving the machinability of superalloys such as Ti6Al4V and Inconel718. Researches on temperature field simulation of Ti6Al4V and Inconel718 are conducted in this paper. A thermal differential equation is established based on Fourier's law and energy conservation law. Then, a model using ABAQUS for simulating heat transfer process is brought out, which is then experimentally validated. Using the simulation model, detailed investigations on temperature field simulation are carried out in Ti6Al4V and Inconel718. According to simulation, surface temperature of the two superalloys eventually reaches their peak values, and the peak temperature of Ti6Al4V is much higher than that of Inconel718. To further investigate temperature heated by laser, laser parameters such as power, scanning velocity, laser spot radius and inclination angle are set to be variables separately for simulation. Simulation results show that laser power and laser spot radius are predominant factors in heating process compared with the influence of scanning velocity and inclination angle. Simulations in this paper provide valuable references for parameter optimization in the following laser heating experiments, which plays an important role in laser assisted machining.

FY96-98 Summary Report Mercury: Next Generation Laser for High Energy Density Physics SI-014

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayramian, A.; Beach, R.; Bibeau, C.

The scope of the Mercury Laser project encompasses the research, development, and engineering required to build a new generation of diode-pumped solid-state lasers for Inertial Confinement Fusion (ICF). The Mercury Laser will be the first integrated demonstration of laser diodes, crystals, and gas cooling within a scalable laser architecture. This report is intended to summarize the progress accomplished during the first three years of the project. Due to the technological challenges associated with production of 900 nm diode-bars, heatsinks, and high optical-quality Yb:S-FAP crystals, the initial focus of the project was primarily centered on the R&D in these three areas.more » During the third year of the project, the R&D continued in parallel with the development of computer codes, partial activation of the laser, component testing, and code validation where appropriate.« less

Theoretical quantification of shock-timing sensitivities for direct-drive inertial confinement fusion implosions on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, D.; Boehly, T. R.; Gregor, M. C.

Using temporally shaped laser pulses, multiple shocks can be launched in direct-drive inertial confinement fusion implosion experiments to set the shell on a desired isentrope or adiabat. The velocity of the first shock and the times at which subsequent shocks catch up to it are measured through the VISAR diagnostic [T. R. Boehly et al., Phys. Plasmas 18, 092706 (2011)] on OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Simulations reproduce these velocity and shock-merger time measurements when using laser pulses designed for setting mid-adiabat (alpha ~ 3) implosions, but agreement degrades for lower-adiabat (alpha ~ 1)more » designs. Several possibilities for this difference are studied: (1) errors in placing the target at the center of irradiation (target offset), (2) variations in energy between the different incident beams (power imbalance), and (3) errors in modeling the laser energy coupled into the capsule. Simulation results indicate that shock timing is most sensitive to details of the density and temperature profiles in the coronal plasma, which influences the laser energy coupled into the target, and only marginally sensitive to target offset and beam power imbalance. A new technique under development to infer coronal profiles using x-ray self-emission imaging [A. K. Davis et al., Bull. Am. Phys. Soc. 61, BAPS.2016.DPP.NO8.7 (2016)] can be applied to the pulse shapes used in shock-timing experiments. This will help identify improved physics models to implement in codes and consequently enhance shock-timing predictive capability for low-adiabat pulses.« less

Design the RS(255,239) encoder and interleaving in the space laser communication system

NASA Astrophysics Data System (ADS)

Lang, Yue; Tong, Shou-feng

2013-08-01

Space laser communication is researched by more and more countries. Space laser communication deserves to be researched. We can acquire higher transmission speed and better transmission quality between satellite and satellite, satellite and earth by setting up laser link. But in the space laser communication system，the reliability is under influences of many factors of atmosphere，detector noise, optical platform jitter and other factors. The intensity of the signal which is attenuated because of the long transmission distance is demanded to have higher intensity to acquire low BER. The channel code technology can enhance the anti-interference ability of the system. The theory of channel coding technology is that some redundancies is added to information codes. So it can make use of the checkout polynomial to correct errors at the sink port. It help the system to get low BER rate and coding gain. Reed-Solomon (RS) code is one of the channel code, and it is one kind of multi-ary BCH code, and it can correct both burst errors and random errors, and it is widely used in the error-control schemes. The new method of the RS encoder and interleaving based on the FPGA is proposed, aiming at satisfying the needs of the widely-used error control technology in the space laser communication field. An improved method for Finite Galois Field multiplier of encoding is proposed, and it is suitable for FPGA implementation. Comparison of the XOR gates cost between the optimization and original, the number of XOR gates is lessen more than 40% .Then give a new structure of interleaving by using the FPGA. By controlling the in-data stream and out-data stream of encoder, the asynchronous process of the whole frame is accomplished, while by using multi-level pipeline, the real-time transfer of the data is achieved. By controlling the read-address and write-address of the block RAM, the interleaving operation of the arbitrary depth is synchronously implemented. Compared with the normal method, it could reduce the complexity of the channel encoder and the hardware requirement effectively.

Numerical Investigation of Radiative Heat Transfer in Laser Induced Air Plasmas

NASA Technical Reports Server (NTRS)

Liu, J.; Chen, Y. S.; Wang, T. S.; Turner, James E. (Technical Monitor)

2001-01-01

Radiative heat transfer is one of the most important phenomena in the laser induced plasmas. This study is intended to develop accurate and efficient methods for predicting laser radiation absorption and plasma radiative heat transfer, and investigate the plasma radiation effects in laser propelled vehicles. To model laser radiation absorption, a ray tracing method along with the Beer's law is adopted. To solve the radiative transfer equation in the air plasmas, the discrete transfer method (DTM) is selected and explained. The air plasma radiative properties are predicted by the LORAN code. To validate the present nonequilibrium radiation model, several benchmark problems are examined and the present results are found to match the available solutions. To investigate the effects of plasma radiation in laser propelled vehicles, the present radiation code is coupled into a plasma aerodynamics code and a selected problem is considered. Comparisons of results at different cases show that plasma radiation plays a role of cooling plasma and it lowers the plasma temperature by about 10%. This change in temperature also results in a reduction of the coupling coefficient by about 10-20%. The present study indicates that plasma radiation modeling is very important for accurate modeling of aerodynamics in a laser propelled vehicle.

The simulation study on optical target laser active detection performance

NASA Astrophysics Data System (ADS)

Li, Ying-chun; Hou, Zhao-fei; Fan, Youchen

2014-12-01

According to the working principle of laser active detection system, the paper establishes the optical target laser active detection simulation system, carry out the simulation study on the detection process and detection performance of the system. For instance, the performance model such as the laser emitting, the laser propagation in the atmosphere, the reflection of optical target, the receiver detection system, the signal processing and recognition. We focus on the analysis and modeling the relationship between the laser emitting angle and defocus amount and "cat eye" effect echo laser in the reflection of optical target. Further, in the paper some performance index such as operating range, SNR and the probability of the system have been simulated. The parameters including laser emitting parameters, the reflection of the optical target and the laser propagation in the atmosphere which make a great influence on the performance of the optical target laser active detection system. Finally, using the object-oriented software design methods, the laser active detection system with the opening type, complete function and operating platform, realizes the process simulation that the detection system detect and recognize the optical target, complete the performance simulation of each subsystem, and generate the data report and the graph. It can make the laser active detection system performance models more intuitive because of the visible simulation process. The simulation data obtained from the system provide a reference to adjust the structure of the system parameters. And it provides theoretical and technical support for the top level design of the optical target laser active detection system and performance index optimization.

Computational study of hot electron generation and energy transport in intense laser produced hot dense matter

NASA Astrophysics Data System (ADS)

Mishra, Rohini

Present ultra high power lasers are capable of producing high energy density (HED) plasmas, in controlled way, with a density greater than solid density and at a high temperature of keV (1 keV ˜ 11,000,000° K). Matter in such extreme states is particularly interesting for (HED) physics such as laboratory studies of planetary and stellar astrophysics, laser fusion research, pulsed neutron source etc. To date however, the physics in HED plasma, especially, the energy transport, which is crucial to realize applications, has not been understood well. Intense laser produced plasmas are complex systems involving two widely distinct temperature distributions and are difficult to model by a single approach. Both kinetic and collisional process are equally important to understand an entire process of laser-solid interaction. By implementing atomic physics models, such as collision, ionization, and radiation damping, self consistently, in state-of-the-art particle-in-cell code (PICLS) has enabled to explore the physics involved in the HED plasmas. Laser absorption, hot electron transport, and isochoric heating physics in laser produced hot dense plasmas are studied with a help of PICLS simulations. In particular, a novel mode of electron acceleration, namely DC-ponderomotive acceleration, is identified in the super intense laser regime which plays an important role in the coupling of laser energy to a dense plasma. Geometric effects on hot electron transport and target heating processes are examined in the reduced mass target experiments. Further, pertinent to fast ignition, laser accelerated fast electron divergence and transport in the experiments using warm dense matter (low temperature plasma) is characterized and explained.

Coding for stable transmission of W-band radio-over-fiber system using direct-beating of two independent lasers.

PubMed

Yang, L G; Sung, J Y; Chow, C W; Yeh, C H; Cheng, K T; Shi, J W; Pan, C L

2014-10-20

We demonstrate experimentally Manchester (MC) coding based W-band (75 - 110 GHz) radio-over-fiber (ROF) system to reduce the low-frequency-components (LFCs) signal distortion generated by two independent low-cost lasers using spectral shaping. Hence, a low-cost and higher performance W-band ROF system is achieved. In this system, direct-beating of two independent low-cost CW lasers without frequency tracking circuit (FTC) is used to generate the millimeter-wave. Approaches, such as delayed self-heterodyne interferometer and heterodyne beating are performed to characterize the optical-beating-interference sub-terahertz signal (OBIS). Furthermore, W-band ROF systems using MC coding and NRZ-OOK are compared and discussed.

The Use of a Pseudo Noise Code for DIAL Lidar

NASA Technical Reports Server (NTRS)

Burris, John F.

2010-01-01

Retrievals of CO2 profiles within the planetary boundary layer (PBL) are required to understand CO2 transport over regional scales and for validating the future space borne CO2 remote sensing instrument, such as the CO2 Laser Sounder, for the ASCENDS mission, We report the use of a return-to-zero (RZ) pseudo noise (PN) code modulation technique for making range resolved measurements of CO2 within the PBL using commercial, off-the-shelf, components. Conventional, range resolved, measurements require laser pulse widths that are s#rorter than the desired spatial resolution and have pulse spacing such that returns from only a single pulse are observed by the receiver at one time (for the PBL pulse separations must be greater than approximately 2000m). This imposes a serious limitation when using available fiber lasers because of the resulting low duty cycle (less than 0.001) and consequent low average laser output power. RZ PN code modulation enables a fiber laser to operate at much higher duty cycles (approaching 0.1) thereby more effectively utilizing the amplifier's output. This results in an increase in received counts by approximately two orders of magnitude. The approach involves employing two, back to back, CW fiber amplifiers seeded at the appropriate on and offline CO2 wavelengths (approximately 1572 nm) using distributed feedback diode lasers modulated by a PN code at rates significantly above 1 megahertz. An assessment of the technique, discussions of measurement precision and error sources as well as preliminary data will be presented.

Modeling rapidly spinning, merging black holes with numerical relativity for the era of first gravitational-wave observations

NASA Astrophysics Data System (ADS)

Lovelace, Geoffrey; Simulating eXtreme Collaboration; LIGO Scientific Collaboration

2016-03-01

The Advanced Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO) began searching for gravitational waves in September 2015, with three times the sensitivity of the initial LIGO experiment. Merging black holes are among the most promising sources of gravitational waves for Advanced LIGO, but near the time of merger, the emitted waves can only be computed using numerical relativity. In this talk, I will present new numerical-relativity simulations of merging black holes, made using the Spectral Einstein Code [black-holes.org/SpEC.html], including cases with black-hole spins that are nearly as fast as possible. I will discuss how such simulations will be able to rapidly follow up gravitational-wave observations, improving our understanding of the waves' sources.

Measurements of Mode Converted Ion Cyclotron Wave with Phase Contrast Imaging in Alcator C-Mod and Comparisons with Synthetic PCI Simulations in TORIC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsujii, N.; Porkolab, M.; Edlund, E. M.

2009-11-26

Mode converted ion cyclotron wave (ICW) has been observed with phase contrast imaging (PCI) in D-{sup 3}He plasmas in Alcator C-Mod. The measurements were carried out with the optical heterodyne technique using acousto-optic modulators which modulate the CO2 laser beam intensity near the ion cyclotron frequency. With recently improved calibration of the PCI system using a calibrated sound wave source, the measurements have been compared with the full-wave code TORIC, as interpreted by a synthetic diagnostic. Because of the line-integrated nature of the PCI signal, the predictions are sensitive to the exact wave field pattern. The simulations are found tomore » be in qualitative agreement with the measurements.« less

NRL Review, 2004

DTIC Science & Technology

2004-05-01

intense laser - matter interaction studies, including particle acceleration. A new 10 Hz ultrashort - pulse (40 fs), Ti:Sapphire...of high- intensity ultrashort laser pulses . He is the chief developer of the HELCAP laser propagation code. Prior to joining NRL, he was employed by...two short- pulse high- intensity lasers , the Table-Top Terawatt (T3) laser and the new Ti:Sapphire Femtosecond Laser (TFL) to study intense

Statistical properties of single-mode fiber coupling of satellite-to-ground laser links partially corrected by adaptive optics.

PubMed

Canuet, Lucien; Védrenne, Nicolas; Conan, Jean-Marc; Petit, Cyril; Artaud, Geraldine; Rissons, Angelique; Lacan, Jerome

2018-01-01

In the framework of satellite-to-ground laser downlinks, an analytical model describing the variations of the instantaneous coupled flux into a single-mode fiber after correction of the incoming wavefront by partial adaptive optics (AO) is presented. Expressions for the probability density function and the cumulative distribution function as well as for the average fading duration and fading duration distribution of the corrected coupled flux are given. These results are of prime interest for the computation of metrics related to coded transmissions over correlated channels, and they are confronted by end-to-end wave-optics simulations in the case of a geosynchronous satellite (GEO)-to-ground and a low earth orbit satellite (LEO)-to-ground scenario. Eventually, the impact of different AO performances on the aforementioned fading duration distribution is analytically investigated for both scenarios.

Study of the hydrodynamics of the formation of flows caused by the interaction of a shock wave with two-dimensional density perturbations on the Iskra-5 laser facility

NASA Astrophysics Data System (ADS)

Babanov, A. V.; Barinov, M. A.; Barinov, S. P.; Garanin, R. V.; Zhidkov, N. V.; Kalmykov, N. A.; Kovalenko, V. P.; Kokorin, S. N.; Pinegin, A. V.; Solomatina, E. Yu.; Solomatin, I. I.; Suslov, N. A.

2017-03-01

The hydrodynamics of the flow formation due to the interaction of a shock wave with two-dimensional density perturbations is experimentally investigated on the Iskra-5 laser facility. Shadow images of a jet arising as a result of the impact of a shock wave (formed by a soft X-ray pulse from a target-illuminator) on a flat aluminium target with a blind cylindrical cavity are recorded in experiments with point-like X-ray backlighting having a photon energy of ~4.5 keV. The sizes and mass of the jet ejected from the aluminium cavity by this shock wave are estimated. The experimental data are compared with the results of numerical simulation of the jet formation and dynamics according to the two-dimensional MID-ND2D code.

On the saturation of stimulated Raman scattering in laser amplification

NASA Astrophysics Data System (ADS)

Dodd, E. S.; Ren, J.; Kwan, T. J. T.; Schmitt, M. J.

2012-10-01

The use of stimulated Raman scattering (SRS) in plasmas has been proposed as an alternative to the CPA technique for laser pulse amplification and compression [1]. Initial experiments demonstrated the amplification and compression of laser pulses in plasma to an unfocused intensity of ˜10^16 W/cm^2 [2], however the amplification was saturated at this level and was accompanied by deleterious spatial and temporal incoherence. The reasons for this incoherence have not been well understood. A physical picture has been developed with results from PIC simulations using the LSP code where spontaneous SRS in the pump modifies the plasma conditions, and which in turn significantly weakens the coupling strength for seed amplification. This led to the development of a novel experimental method to significantly increase the amplified power in the short-pulses via SRS.[4pt] [1] G. Shvets, N. J. Fisch, A. Pukhov, and J. Meyer-ter-Vehn, Phys. Rev. Lett. 81 4879 (1998).[0pt] [2] J. Ren, W.-F. Cheng, S.-L Li, and S. Suckewer, Nat. Phys. 3 732 (2007). LA-UR-12-22734

Effects of CSR Generated from Upstream Bends in a Laser Plasma Storage Ring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell, C.; Qiang, J.; Venturini, M.

The recent proposal [1] of a Laser Plasma Storage Ring (LPSR) envisions the use of a laser-plasma (LP) acceleration module to inject an electron beam into a compact 500 MeV storage ring. Electron bunches generated by LP methods are naturally very short (tens of femtoseconds), presenting peak currents on the order of 10 kA or higher. Of obvious concern is the impact of collective effects and in particular Coherent Synchrotron Radiation (CSR) on the beam dynamics in the storage ring. Available simulation codes (e.g. Elegant [2]) usually include transient CSR effects but neglect the contribution of radiation emitted from trailingmore » magnets. In a compact storage ring, with dipole magnets close to each other, cross talking between different magnets could in principle be important.In this note we investigate this effect for the proposed LPSR and show that, in fact, this effect is relatively small. However our analysis also indicates that CSR effects in general would be quite strong and deserve a a careful study.« less

High-current, relativistic electron-beam transport in metals and the role of magnetic collimation.

PubMed

Storm, M; Solodov, A A; Myatt, J F; Meyerhofer, D D; Stoeckl, C; Mileham, C; Betti, R; Nilson, P M; Sangster, T C; Theobald, W; Guo, Chunlei

2009-06-12

High-resolution coherent transition radiation (CTR) imaging diagnoses electrons accelerated in laser-solid interactions with intensities of approximately 10;{19} W/cm;{2}. The CTR images indicate electron-beam filamentation and annular propagation. The beam temperature and half-angle divergence are inferred to be approximately 1.4 MeV and approximately 16 degrees , respectively. Three-dimensional hybrid-particle-in-cell code simulations reproduce the details of the CTR images assuming an initial half-angle divergence of approximately 56 degrees . Self-generated resistive magnetic fields are responsible for the difference between the initial and measured divergence.

Abstracts for student symposium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldman, B.

Lawrence Livermore National Laboratory Science and Engineering Research Semester (SERS) students are participants in a national program sponsored by the DOE Office of Energy Research. Presented topics from Fall 1993 include: Laser glass, wiring codes, lead in food and food containers, chromium removal from ground water, fiber optic sensors for ph measurement, CFC replacement, predator/prey simulation, detection of micronuclei in germ cells, DNA conformation, stimulated brillouin scattering, DNA sequencing, evaluation of education programs, neural network analysis of nuclear glass, lithium ion batteries, Indonesian snails, optical switching systems, and photoreceiver design. Individual papers are indexed separately on the Energy Data Base.

UCLA Final Technical Report for the "Community Petascale Project for Accelerator Science and Simulation”.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mori, Warren

The UCLA Plasma Simulation Group is a major partner of the “Community Petascale Project for Accelerator Science and Simulation”. This is the final technical report. We include an overall summary, a list of publications, progress for the most recent year, and individual progress reports for each year. We have made tremendous progress during the three years. SciDAC funds have contributed to the development of a large number of skeleton codes that illustrate how to write PIC codes with a hierarchy of parallelism. These codes cover 2D and 3D as well as electrostatic solvers (which are used in beam dynamics codesmore » and quasi-static codes) and electromagnetic solvers (which are used in plasma based accelerator codes). We also used these ideas to develop a GPU enabled version of OSIRIS. SciDAC funds were also contributed to the development of strategies to eliminate the Numerical Cerenkov Instability (NCI) which is an issue when carrying laser wakefield accelerator (LWFA) simulations in a boosted frame and when quantifying the emittance and energy spread of self-injected electron beams. This work included the development of a new code called UPIC-EMMA which is an FFT based electromagnetic PIC code and to new hybrid algorithms in OSIRIS. A new hybrid (PIC in r-z and gridless in φ) algorithm was implemented into OSIRIS. In this algorithm the fields and current are expanded into azimuthal harmonics and the complex amplitude for each harmonic is calculated separately. The contributions from each harmonic are summed and then used to push the particles. This algorithm permits modeling plasma based acceleration with some 3D effects but with the computational load of an 2D r-z PIC code. We developed a rigorously charge conserving current deposit for this algorithm. Very recently, we made progress in combining the speed up from the quasi-3D algorithm with that from the Lorentz boosted frame. SciDAC funds also contributed to the improvement and speed up of the quasi-static PIC code QuickPIC. We have also used our suite of PIC codes to make scientific discovery. Highlights include supporting FACET experiments which achieved the milestones of showing high beam loading and energy transfer efficiency from a drive electron beam to a witness electron beam and the discovery of a self-loading regime a for high gradient acceleration of a positron beam. Both of these experimental milestones were published in Nature together with supporting QuickPIC simulation results. Simulation results from QuickPIC were used on the cover of Nature in one case. We are also making progress on using highly resolved QuickPIC simulations to show that ion motion may not lead to catastrophic emittance growth for tightly focused electron bunches loaded into nonlinear wakefields. This could mean that fully self-consistent beam loading scenarios are possible. This work remains in progress. OSIRIS simulations were used to discover how 200 MeV electron rings are formed in LWFA experiments, on how to generate electrons that have a series of bunches on nanometer scale, and how to transport electron beams from (into) plasma sections into (from) conventional beam optic sections.« less

Polar-Drive--Implosion Physics on OMEGA and the NIF

NASA Astrophysics Data System (ADS)

Radha, P. B.

2012-10-01

Polar drive (PD) permits the execution of direct-drive--ignition experiments on facilities that are configured for x-ray drive such as the National Ignition Facility (NIF) and Laser M'egajoule. Experiments on the OMEGA laser are used to develop and validate models of PD implosions. Results from OMEGA PD shock-timing and warm implosions are presented. Experiments are simulated with the 2-D hydrodynamic code DRACO including full 3-D ray trace to model oblique beams. Excellent agreement is obtained in shock velocity and catch-up in PD geometry in warm, plastic shells. Predicted areal densities are measured in PD implosion experiments. Good agreement between simulation and experiments is obtained in the overall shape of the compressing shell when observed through x-ray backlighting. Simulated images of the hot core, including the effect of magnetic fields, are compared with experiments. Comparisons of simulated and observed scattered light and bang time in PD geometry are presented. Several techniques to increase implosion velocity are presented including beam profile variations and different ablator materials. Results from shimmed-target PD experiments will also be presented. Designs for future PD OMEGA experiments at ignition-relevant intensities will be presented. The implication of these results for NIF-scale plasmas is discussed. Experiments for the NIF in its current configuration, with indirect-drive phase plates, are proposed to study implosion energetics and shell asymmetries. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.

Modulated Sine Waves for Differential Absorption Measurements Using a CW Laser System

NASA Technical Reports Server (NTRS)

Campbell, Joel F. (Inventor); Lin, Bing (Inventor); Nehrir, Amin R. (Inventor)

2015-01-01

A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

Comparison of laser anemometer measurements and theory in an annular turbine cascade with experimental accuracy determined by parameter estimation

NASA Technical Reports Server (NTRS)

Goldman, L. J.; Seasholtz, R. G.

1982-01-01

Experimental measurements of the velocity components in the blade to blade (axial tangential) plane were obtained with an axial flow turbine stator passage and were compared with calculations from three turbomachinery computer programs. The theoretical results were calculated from a quasi three dimensional inviscid code, a three dimensional inviscid code, and a three dimensional viscous code. Parameter estimation techniques and a particle dynamics calculation were used to assess the accuracy of the laser measurements, which allow a rational basis for comparison of the experimenal and theoretical results. The general agreement of the experimental data with the results from the two inviscid computer codes indicates the usefulness of these calculation procedures for turbomachinery blading. The comparison with the viscous code, while generally reasonable, was not as good as for the inviscid codes.

Pattern recognition of electronic bit-sequences using a semiconductor mode-locked laser and spatial light modulators

NASA Astrophysics Data System (ADS)

Bhooplapur, Sharad; Akbulut, Mehmetkan; Quinlan, Franklyn; Delfyett, Peter J.

2010-04-01

A novel scheme for recognition of electronic bit-sequences is demonstrated. Two electronic bit-sequences that are to be compared are each mapped to a unique code from a set of Walsh-Hadamard codes. The codes are then encoded in parallel on the spectral phase of the frequency comb lines from a frequency-stabilized mode-locked semiconductor laser. Phase encoding is achieved by using two independent spatial light modulators based on liquid crystal arrays. Encoded pulses are compared using interferometric pulse detection and differential balanced photodetection. Orthogonal codes eight bits long are compared, and matched codes are successfully distinguished from mismatched codes with very low error rates, of around 10-18. This technique has potential for high-speed, high accuracy recognition of bit-sequences, with applications in keyword searches and internet protocol packet routing.

Simulations and measurements of hot-electron generation driven by the multibeam two-plasmon-decay instability

DOE PAGES

Follett, R. K.; Myatt, J. F.; Shaw, J. G.; ...

2017-10-30

We report that multiple-beam experiments relevant to direct-drive inertial confinement fusion show the importance of nonlinear saturation mechanisms in the common-wave two-plasmon-decay (TPD) instability. Planar target experiments on the OMEGA laser used hard-x-ray measurements to study the influence of the linear common-wave growth rate on TPD driven hot-electron production in two drive beam configurations and over a range of overlapped laser intensities from 3.6 to 15.2 x 10 14 W/cm 2. The beam configuration with the larger linear common-wave growth rate had a lower intensity threshold for the onset of hot-electron production, but the linear growth rate did not havemore » a significant impact on hot-electron production at high intensities. The experiments were modeled in 3-D using a hybrid code (LPSE) that combines a wave solver with a particle tracker to self-consistently calculate the electron velocity distribution and evolve electron Landau damping. Finally, good quantitative agreement was obtained between the simulated and measured hotel-electron distributions using a novel technique to account for macroscopic spatial and temporal variations that are present in the experiments.« less

Simulations and measurements of hot-electron generation driven by the multibeam two-plasmon-decay instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Follett, R. K.; Myatt, J. F.; Shaw, J. G.

We report that multiple-beam experiments relevant to direct-drive inertial confinement fusion show the importance of nonlinear saturation mechanisms in the common-wave two-plasmon-decay (TPD) instability. Planar target experiments on the OMEGA laser used hard-x-ray measurements to study the influence of the linear common-wave growth rate on TPD driven hot-electron production in two drive beam configurations and over a range of overlapped laser intensities from 3.6 to 15.2 x 10 14 W/cm 2. The beam configuration with the larger linear common-wave growth rate had a lower intensity threshold for the onset of hot-electron production, but the linear growth rate did not havemore » a significant impact on hot-electron production at high intensities. The experiments were modeled in 3-D using a hybrid code (LPSE) that combines a wave solver with a particle tracker to self-consistently calculate the electron velocity distribution and evolve electron Landau damping. Finally, good quantitative agreement was obtained between the simulated and measured hotel-electron distributions using a novel technique to account for macroscopic spatial and temporal variations that are present in the experiments.« less

Simulation studies of a XUV/soft X-ray harmonic-cascade FEL for the proposed LBNL recirculating linac*

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fawley, W.M.; Barletta, W.A.; Corlett, J.N.

Presently there is significant interest at LBNL in designing and building a facility for ultrafast (i.e. femtosecond time scale) x-ray science based upon a superconducting, recirculating RF linac (see Corlett et al. for more details). In addition to producing synchrotron radiation pulses in the 1-15 keV energy range, we are also considering adding one or more free-electron laser (FEL) beamlines using a harmonic cascade approach to produce coherent XUV soft X-ray emission beginning with a strong input seed at {approx}200 nm wavelength obtained from a ''conventional'' laser. Each cascade is composed of a radiator together with a modulator section, separatedmore » by a magnetic chicane. The chicane temporally delays the electron beam pulse in order that a ''virgin'' pulse region (with undegraded energy spread) be brought into synchronism with the radiation pulse, which together then undergo FEL action in the modulator. We present various results obtained with the GINGER simulation code examining final output sensitivity to initial electron beam parameters. We also discuss the effects of spontaneous emission and shot noise upon this particular cascade approach which can limit the final output coherence.« less

Time Shifted PN Codes for CW Lidar, Radar, and Sonar

NASA Technical Reports Server (NTRS)

Campbell, Joel F. (Inventor); Prasad, Narasimha S. (Inventor); Harrison, Fenton W. (Inventor); Flood, Michael A. (Inventor)

2013-01-01

A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere.

Simulation of stimulated Brillouin scattering and stimulated Raman scattering in shock ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hao, L.; Li, J.; Liu, W. D.

2016-04-15

We study stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) in shock ignition by comparing fluid and particle-in-cell (PIC) simulations. Under typical parameters for the OMEGA experiments [Theobald et al., Phys. Plasmas 19, 102706 (2012)], a series of 1D fluid simulations with laser intensities ranging between 2 × 10{sup 15} and 2 × 10{sup 16 }W/cm{sup 2} finds that SBS is the dominant instability, which increases significantly with the incident intensity. Strong pump depletion caused by SBS and SRS limits the transmitted intensity at the 0.17n{sub c} to be less than 3.5 × 10{sup 15 }W/cm{sup 2}. The PIC simulations show similar physics but with higher saturationmore » levels for SBS and SRS convective modes and stronger pump depletion due to higher seed levels for the electromagnetic fields in PIC codes. Plasma flow profiles are found to be important in proper modeling of SBS and limiting its reflectivity in both the fluid and PIC simulations.« less

Research of laser echo signal simulator

NASA Astrophysics Data System (ADS)

Xu, Rui; Shi, Rui; Wang, Xin; Li, Zhou

2015-11-01

Laser echo signal simulator is one of the most significant components of hardware-in-the-loop (HWIL) simulation systems for LADAR. System model and time series model of laser echo signal simulator are established. Some influential factors which could induce fixed error and random error on the simulated return signals are analyzed, and then these system insertion errors are analyzed quantitatively. Using this theoretical model, the simulation system is investigated experimentally. The results corrected by subtracting fixed error indicate that the range error of the simulated laser return signal is less than 0.25m, and the distance range that the system can simulate is from 50m to 20km.

Heat transport modeling of the dot spectroscopy platform on NIF

DOE PAGES

Farmer, W. A.; Jones, O. S.; Barrios, M. A.; ...

2018-02-13

Electron heat transport within an inertial-fusion hohlraum plasma is difficult to model due to the complex interaction of kinetic plasma effects, magnetic fields, laser-plasma interactions, and microturbulence. In this paper, simulations using the radiation-hydrodynamic code, HYDRA, are compared to hohlraum plasma experiments which contain a Manganese–Cobalt tracer dot (Barrios et al 2016 Phys. Plasmas 23 056307). The dot is placed either on the capsule or on a film midway between the capsule and the laser-entrance hole. From spectroscopic measurements, electron temperature and position of the dot are inferred. Simulations are performed with ad hoc flux limiters of f = 0.15more » and f = 0.03 (with electron heat flux, q, limited to fnT 3/2/m 1/2), and two more physical means of flux limitation: the magnetohydrodynamics and nonlocal packages. The nonlocal model agrees best with the temperature of the dot-on-film and dot-on-capsule. The hohlraum produced x-ray flux is over-predicted by roughly ~11% for the f = 0.03 model and the remaining models by ~16%. The simulated trajectories of the dot-on-capsule are slightly ahead of the experimental trajectory for all but the f = 0.03 model. The simulated dot-on-film position disagrees with the experimental measurement for all transport models. In the MHD simulation of the dot-on-film, the dot is strongly perturbative, though the simulation predicts a peak dot-on-film temperature 2–3 keV higher than the measurement. Finally, this suggests a deficiency in the MHD modeling possibly due to the neglect of the Righi–Leduc term or interpenetrating flows of multiple ion species which would reduce the strength of the self-generated fields.« less

Heat transport modeling of the dot spectroscopy platform on NIF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, W. A.; Jones, O. S.; Barrios, M. A.

Electron heat transport within an inertial-fusion hohlraum plasma is difficult to model due to the complex interaction of kinetic plasma effects, magnetic fields, laser-plasma interactions, and microturbulence. In this paper, simulations using the radiation-hydrodynamic code, HYDRA, are compared to hohlraum plasma experiments which contain a Manganese–Cobalt tracer dot (Barrios et al 2016 Phys. Plasmas 23 056307). The dot is placed either on the capsule or on a film midway between the capsule and the laser-entrance hole. From spectroscopic measurements, electron temperature and position of the dot are inferred. Simulations are performed with ad hoc flux limiters of f = 0.15more » and f = 0.03 (with electron heat flux, q, limited to fnT 3/2/m 1/2), and two more physical means of flux limitation: the magnetohydrodynamics and nonlocal packages. The nonlocal model agrees best with the temperature of the dot-on-film and dot-on-capsule. The hohlraum produced x-ray flux is over-predicted by roughly ~11% for the f = 0.03 model and the remaining models by ~16%. The simulated trajectories of the dot-on-capsule are slightly ahead of the experimental trajectory for all but the f = 0.03 model. The simulated dot-on-film position disagrees with the experimental measurement for all transport models. In the MHD simulation of the dot-on-film, the dot is strongly perturbative, though the simulation predicts a peak dot-on-film temperature 2–3 keV higher than the measurement. Finally, this suggests a deficiency in the MHD modeling possibly due to the neglect of the Righi–Leduc term or interpenetrating flows of multiple ion species which would reduce the strength of the self-generated fields.« less

Heat transport modeling of the dot spectroscopy platform on NIF

NASA Astrophysics Data System (ADS)

Farmer, W. A.; Jones, O. S.; Barrios, M. A.; Strozzi, D. J.; Koning, J. M.; Kerbel, G. D.; Hinkel, D. E.; Moody, J. D.; Suter, L. J.; Liedahl, D. A.; Lemos, N.; Eder, D. C.; Kauffman, R. L.; Landen, O. L.; Moore, A. S.; Schneider, M. B.

2018-04-01

Electron heat transport within an inertial-fusion hohlraum plasma is difficult to model due to the complex interaction of kinetic plasma effects, magnetic fields, laser-plasma interactions, and microturbulence. Here, simulations using the radiation-hydrodynamic code, HYDRA, are compared to hohlraum plasma experiments which contain a Manganese-Cobalt tracer dot (Barrios et al 2016 Phys. Plasmas 23 056307). The dot is placed either on the capsule or on a film midway between the capsule and the laser-entrance hole. From spectroscopic measurements, electron temperature and position of the dot are inferred. Simulations are performed with ad hoc flux limiters of f = 0.15 and f = 0.03 (with electron heat flux, q, limited to fnT 3/2/m 1/2), and two more physical means of flux limitation: the magnetohydrodynamics and nonlocal packages. The nonlocal model agrees best with the temperature of the dot-on-film and dot-on-capsule. The hohlraum produced x-ray flux is over-predicted by roughly ˜11% for the f = 0.03 model and the remaining models by ˜16%. The simulated trajectories of the dot-on-capsule are slightly ahead of the experimental trajectory for all but the f = 0.03 model. The simulated dot-on-film position disagrees with the experimental measurement for all transport models. In the MHD simulation of the dot-on-film, the dot is strongly perturbative, though the simulation predicts a peak dot-on-film temperature 2-3 keV higher than the measurement. This suggests a deficiency in the MHD modeling possibly due to the neglect of the Righi-Leduc term or interpenetrating flows of multiple ion species which would reduce the strength of the self-generated fields.

Mapping the Milky Way Galaxy with LISA

NASA Technical Reports Server (NTRS)

McKinnon, Jose A.; Littenberg, Tyson

2012-01-01

Gravitational wave detectors in the mHz band (such as the Laser Interferometer Space Antenna, or LISA) will observe thousands of compact binaries in the galaxy which can be used to better understand the structure of the Milky Way. To test the effectiveness of LISA to measure the distribution of the galaxy, we simulated the Close White Dwarf Binary (CWDB) gravitational wave sky using different models for the Milky Way. To do so, we have developed a galaxy density distribution modeling code based on the Markov Chain Monte Carlo method. The code uses different distributions to construct realizations of the galaxy. We then use the Fisher Information Matrix to estimate the variance and covariance of the recovered parameters for each detected CWDB. This is the first step toward characterizing the capabilities of space-based gravitational wave detectors to constrain models for galactic structure, such as the size and orientation of the bar in the center of the Milky Way

Using a short-pulse diffraction-limited laser beam to probe filamentation of a random phase plate smoothed beam.

PubMed

Kline, J L; Montgomery, D S; Flippo, K A; Johnson, R P; Rose, H A; Shimada, T; Williams, E A

2008-10-01

A short pulse (few picoseconds) laser probe provides high temporal resolution measurements to elucidate details of fast dynamic phenomena not observable with typical longer laser pulse probes and gated diagnostics. Such a short pulse laser probe (SPLP) has been used to measure filamentation of a random phase plate (RPP) smoothed laser beam in a gas-jet plasma. The plasma index of refraction due to driven density and temperature fluctuations by the RPP beam perturbs the phase front of a SPLP propagating at a 90 degree angle with respect to the RPP interaction beam. The density and temperature fluctuations are quasistatic on the time scale of the SPLP (approximately 2 ps). The transmitted near-field intensity distribution from the SPLP provides a measure of the phase front perturbation. At low plasma densities, the transmitted intensity pattern is asymmetric with striations across the entire probe beam in the direction of the RPP smoothed beam. As the plasma density increases, the striations break up into smaller sizes along the direction of the RPP beam propagation. The breakup of the intensity pattern is consistent with self-focusing of the RPP smoothed interaction beam. Simulations of the experiment using the wave propagation code, PF3D, are in qualitative agreement demonstrating that the asymmetric striations can be attributed to the RPP driven density fluctuations. Quantification of the beam breakup measured by the transmitted SPLP could lead to a new method for measuring self-focusing of lasers in underdense plasmas.

Characterization of the fast electrons distribution produced in a high intensity laser target interaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Westover, B.; Lawrence Livermore National Laboratory, Livermore, California 94550; Chen, C. D.

2014-03-15

Experiments on the Titan laser (∼150 J, 0.7 ps, 2 × 10{sup 20} W cm{sup −2}) at the Lawrence Livermore National Laboratory were carried out in order to study the properties of fast electrons produced by high-intensity, short pulse laser interacting with matter under conditions relevant to Fast Ignition. Bremsstrahlung x-rays produced by these fast electrons were measured by a set of compact filter-stack based x-ray detectors placed at three angles with respect to the target. The measured bremsstrahlung signal allows a characterization of the fast electron beam spectrum, conversion efficiency of laser energy into fast electron kinetic energy and angular distribution. A Monte Carlo codemore » Integrated Tiger Series was used to model the bremsstrahlung signal and infer a laser to fast electron conversion efficiency of 30%, an electron slope temperature of about 2.2 MeV, and a mean divergence angle of 39°. Simulations were also performed with the hybrid transport code ZUMA which includes fields in the target. In this case, a conversion efficiency of laser energy to fast electron energy of 34% and a slope temperature between 1.5 MeV and 4 MeV depending on the angle between the target normal direction and the measuring spectrometer are found. The observed temperature of the bremsstrahlung spectrum, and therefore the inferred electron spectrum are found to be angle dependent.« less

Inertial fusion program and national laser users facility program

NASA Astrophysics Data System (ADS)

1995-01-01

This is the 1994 annual report for the University of Rochester, Laboratory for Laser Energetics. The report is presented as a series of research type reports. The titles emphasize the breadth of work carried out. They are: stability analysis of unsteady ablation fronts; characterization of laser-produced plasma density profiles using grid image refractometry; transport and sound waves in plasmas with light and heavy ions; three-halves-harmonic radiation from long-scale-length plasmas revisited; OMEGA upgrade status report; target imaging and backlighting diagnosis; effect of electron collisions on ion-acoustic waves and heat flow; particle-in-cell code simulations of the interaction of gaussian ultrashort laser pulses with targets of varying initial scale lengths; characterization of thick cryogenic fuel layers: compensation for the lens effect using convergent beam interferometry; compact, multijoule-output, Nd:Glass, large-aperture ring amplifier; atomic force microscopy observation of water-induced morphological changes in Y2O3 monolayer coatings; observation of longitudinal acceleration of electrons born in a high-intensity laser focus; spatial intensity nonuniformities of an OMEGA beam due to nonlinear beam propagation; calculated X-ray backlighting images of mixed imploded targets; evaluation of cosmic rays for use in the monitoring of the MEDUSA scintillator-photomultiplier diagnostic array; highly efficient second-harmonic generation of ultra-intense Nd:Glass laser pulses multiple cutoff wave numbers of the ablative Rayleigh-Taylor instability; ultrafast, all-silicon light modulator; angular dependence of the stimulated Brillouin scattering in homogeneous plasma; and femtosecond excited-state dynamics of a conjugated ladder polymer.

Synthesis of polycaprolactone-titanium oxide multilayer films by nanosecond laser pulses and electrospinning technique for better implant fabrication

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naghshine, Babak B.; Cosman, James A.; Kiani, Amirkianoosh, E-mail: a.kiani@unb.ca

In this study, a combination of electrospinning and laser texturing is introduced as a novel method for increasing the biocompatibility of metal implants. Besides having a rough laser treated surface, the implant benefits from the high porosity and better wettability of an electrospun fibrous structure, which is a more favorable environment for cell proliferation. Titanium samples were patterned using a nanosecond laser beam and were placed as collectors in an electrospinning machine. They were then soaked in simulated body fluid for four weeks. Energy Dispersive X-ray and X-Ray Diffraction results indicate significantly more hydroxyapatite formation on laser treated samples withmore » nanoscale fibers deposited on their surface. This shows that having a laser treated surface underneath the fibrous layer can improve short-term biocompatibility even before degradation of fibers. The thermal conductivity of the electrospun layer, measured using a Hot Disk Transient Plane Source instrument and computer code, was shown to be considerably lower than that of titanium and very close to bone. The presence of this layer can therefore be beneficial in making the implant more compatible to a biological medium. In case of dental implants, it was shown that this layer can act as a thermal barrier while a hot beverage is consumed and it can decrease the temperature rise by about 60%, which avoids any possible damage to newly formed cells during the healing period.« less

Digital barcodes of suspension array using laser induced breakdown spectroscopy

PubMed Central

He, Qinghua; Liu, Yixi; He, Yonghong; Zhu, Liang; Zhang, Yilong; Shen, Zhiyuan

2016-01-01

We show a coding method of suspension array based on the laser induced breakdown spectroscopy (LIBS), which promotes the barcodes from analog to digital. As the foundation of digital optical barcodes, nanocrystals encoded microspheres are prepared with self-assembly encapsulation method. We confirm that digital multiplexing of LIBS-based coding method becomes feasible since the microsphere can be coded with direct read-out data of wavelengths, and the method can avoid fluorescence signal crosstalk between barcodes and analyte tags, which lead to overall advantages in accuracy and stability to current fluorescent multicolor coding method. This demonstration increases the capability of multiplexed detection and accurate filtrating, expanding more extensive applications of suspension array in life science. PMID:27808270

Comparative analysis of ventricular assist devices (POLVAD and POLVAD_EXT) based on multiscale FEM model.

PubMed

Milenin, Andrzej; Kopernik, Magdalena

2011-01-01

The prosthesis - pulsatory ventricular assist device (VAD) - is made of polyurethane (PU) and biocompatible TiN deposited by pulsed laser deposition (PLD) method. The paper discusses the numerical modelling and computer-aided design of such an artificial organ. Two types of VADs: POLVAD and POLVAD_EXT are investigated. The main tasks and assumptions of the computer program developed are presented. The multiscale model of VAD based on finite element method (FEM) is introduced and the analysis of the stress-strain state in macroscale for the blood chamber in both versions of VAD is shown, as well as the verification of the results calculated by applying ABAQUS, a commercial FEM code. The FEM code developed is based on a new approach to the simulation of multilayer materials obtained by using PLD method. The model in microscale includes two components, i.e., model of initial stresses (residual stress) caused by the deposition process and simulation of active loadings observed in the blood chamber of POLVAD and POLVAD_EXT. The computed distributions of stresses and strains in macro- and microscales are helpful in defining precisely the regions of blood chamber, which can be defined as the failure-source areas.

Optimization of the LCLS X-Ray FEL Output Performance in the Presence of Strong Undulator Wakefields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reiche, S.; /UCLA; Bane, K.L.F.

The Linac Coherent Light Source (LCLS) Free-Electron Laser will operate in the wavelength range of 1.5 to 15 Angstroms. Energy loss due to wakefields within the long undulator can degrade the FEL process by detuning the resonant FEL frequency. The wakefields arise from the vacuum chamber wall resistivity, its surface roughness, and abrupt changes in its aperture. For LCLS parameters, the resistive component is the most critical and depends upon the chamber material (e.g. Cu) and its radius. To study the expected performance in the presence of these wakefields, we make a series of start-to-end simulations with tracking codes PARMELAmore » and ELEGANT and time-dependent FEL simulation codes Genesis 1.3 and Ginger. We discuss the impact of the wakefield on output energy, spectral bandwidth, and temporal envelope of the output FEL pulse, as well as the benefits of a partial compensation obtained with a slight z dependent taper in the undulator field. We compare these results to those obtained by decreasing the bunch charge or increasing the vacuum chamber radius. We also compare our results to those predicted in concurrent analytical work.« less

Design of high-speed optical transmission module with an integrated Ti:Er:LiNbO3 waveguide laser/ LiNbO3 electro-optic modulator

NASA Astrophysics Data System (ADS)

Bai, Yang; Chen, Shufen; Fu, Li; Fang, Wei; Lu, Junjun

2005-01-01

A high bit rate more than 10Gbit/s optical pulse generation device is the key to achieving high-speed and broadband optical fiber communication network system .Now, we propose a novel high-speed optical transmission module(TM) consisting of a Ti:Er:LiNbO3 waveguide laser and a Mach-Zehnder-type encoding modulator on the same Er-doped substrate. According to the standard of ITU-T, we design the 10Gbit/ s transmission module at 1.53μm on the Z cut Y propagation LiNbO3 slice. A dynamic model and the corresponding numerical code are used to analyze the waveguide laser while the electrooptic effect to design the modulator. Meanwhile, the working principle, key technology, typical characteristic parameters of the module are given. The transmission module has a high extinction ratio and a low driving voltage, which supplies the efficient, miniaturized light source for wavelength division multiplexing(WDM) system. In additional, the relation of the laser gain with the cavity parameter, as well as the relation of the bandwidth of the electrooptic modulator with some key factors are discussed .The designed module structure is simulated by BPM software and HFSS software.

Feasibility and its characteristics of CO2 laser micromachining-based PMMA anti-scattering grid estimated by MCNP code simulation.

PubMed

Bae, Jun Woo; Kim, Hee Reyoung

2018-01-01

Anti-scattering grid has been used to improve the image quality. However, applying a commonly used linear or parallel grid would cause image distortion, and focusing grid also requires a precise fabrication technology, which is expensive. To investigate and analyze whether using CO2 laser micromachining-based PMMA anti-scattering grid can improve the performance of the grid at a lower cost. Thus, improvement of grid performance would result in improvement of image quality. The cross-sectional shape of CO2 laser machined PMMA is similar to alphabet 'V'. The performance was characterized by contrast improvement factor (CIF) and Bucky. Four types of grid were tested, which include thin parallel, thick parallel, 'V'-type and 'inverse V'-type of grid. For a Bucky factor of 2.1, the CIF of the grid with both the "V" and inverse "V" had a value of 1.53, while the thick and thick parallel types had values of 1.43 and 1.65, respectively. The 'V' shape grid manufacture by CO2 laser micromachining showed higher CIF than parallel one, which had same shielding material channel width. It was thought that the 'V' shape grid would be replacement to the conventional parallel grid if it is hard to fabricate the high-aspect-ratio grid.

Laser pulse propagation in inhomogeneous magnetoplasma channels and wakefield acceleration

NASA Astrophysics Data System (ADS)

Sharma, B. S.; Jain, Archana; Jaiman, N. K.; Gupta, D. N.; Jang, D. G.; Suk, H.; Kulagin, V. V.

2014-02-01

Wakefield excitation in a preformed inhomogeneous parabolic plasma channel by an intense relativistic (≃1019 W/cm2) circularly polarized Gaussian laser pulse is investigated analytically and numerically in the presence of an external longitudinal magnetic field. A three dimensional envelope equation for the evolution of the laser pulse is derived, which includes the effect of the nonparaxial and applied external magnetic field. A relation for the channel radius with the laser spot size is derived and examines numerically to see the external magnetic field effect. It is observed that the channel radius depends on the applied external magnetic field. An analytical expression for the wakefield is derived and validated with the help of a two dimensional particle in cell (2D PIC) simulation code. It is shown that the electromagnetic nature of the wakes in an inhomogeneous plasma channel makes their excitation nonlocal, which results in change of fields with time and external magnetic field due to phase mixing of the plasma oscillations with spatially varying frequencies. The magnetic field effect on perturbation of the plasma density and decreasing length is also analyzed numerically. In addition, it has been shown that the electron energy gain in the inhomogeneous parabolic magnetoplasma channel can be increased significantly compared with the homogeneous plasma channel.

The lightcraft project

NASA Technical Reports Server (NTRS)

Messitt, Don G.; Myrabo, Leik N.

1991-01-01

Rensselaer Polytechnic Institute has been developing a transatmospheric 'Lightcraft' technology which uses beamed laser energy to propel advanced shuttle craft to orbit. In the past several years, Rensselaer students have analyzed the unique combined-cycle Lightcraft engine, designed a small unmanned Lightcraft Technology Demonstrator, and conceptualized larger manned Lightcraft - to name just a few of the interrelated design projects. The 1990-91 class carried out preliminary and detailed design efforts for a one-person 'Mercury' Lightcraft, using computer-aided design and finite-element structural modeling techniques. In addition, they began construction of a 2.6 m-diameter, full-scale engineering prototype mockup. The mockup will be equipped with three robotic legs that 'kneel' for passenger entry and exit. More importantly, the articulated tripod gear is crucial for accurately pointing at, and tracking the laser relay mirrors, a maneuver that must be performed just prior to liftoff. Also accomplished were further design improvements on a 6-inch-diameter Lightcraft model (for testing in RPI's hypersonic tunnel), and new laser propulsion experiments. The resultant experimental data will be used to calibrate Computational Fluid Dynamic (CFD) codes and analytical laser propulsion models that can simulate vehicle/engine flight conditions along a transatmospheric boost trajectory. These efforts will enable the prediction of distributed aerodynamic and thruster loads over the entire full-scale spacecraft.

Simulation of laser interaction with ablative plasma and hydrodynamic behavior of laser supported plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tong Huifeng; Yuan Hong; Tang Zhiping

When an intense laser beam irradiates on a solid target, ambient air ionizes and becomes plasma, while part of the target rises in temperature, melts, vaporizes, ionizes, and yet becomes plasma. A general Godunov finite difference scheme WENO (Weighted Essentially Non-Oscillatory Scheme) with fifth-order accuracy is used to simulate 2-dimensional axis symmetrical laser-supported plasma flow field in the process of laser ablation. The model of the calculation of ionization degree of plasma and the interaction between laser beam and plasma are considered in the simulation. The numerical simulations obtain the profiles of temperature, density, and velocity at different times whichmore » show the evolvement of the ablative plasma. The simulated results show that the laser energy is strongly absorbed by plasma on target surface and that the velocity of laser supported detonation (LSD) wave is half of the ideal LSD value derived from Chapman-Jouguet detonation theory.« less

77 FR 13367 - General Electric-Hitachi Global Laser Enrichment, LLC, Proposed Laser-Based Uranium Enrichment...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-06

... NUCLEAR REGULATORY COMMISSION [NRC-2009-0157] General Electric-Hitachi Global Laser Enrichment... Impact Statement (EIS) for the proposed General Electric- Hitachi Global Laser Enrichment, LLC (GLE... issue a license to GLE, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) parts 30, 40...

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, K. S.

1985-01-01

This semiannual progress report covers the period from April 1, 1985 to Sept. 30, 1985 under NASA grant NAS1-441 entitled direct solar pumped iodine laser amplifier. During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator was carried out before the amplifier studies. The amplifier studies are postponed to the extended period following completion of the parametric studies. In addition, the kinetic modeling of a solar pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) the radiation characteristics of solar simulator and the parametric characteristics of photodissociation iodine laser continuously pumped by a Vortek solar simulator; (2) kinetic modeling of a solar pumped iodine laser amplifier; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

An analysis of options available for developing a common laser ray tracing package for Ares and Kull code frameworks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weeratunga, S K

Ares and Kull are mature code frameworks that support ALE hydrodynamics for a variety of HEDP applications at LLNL, using two widely different meshing approaches. While Ares is based on a 2-D/3-D block-structured mesh data base, Kull is designed to support unstructured, arbitrary polygonal/polyhedral meshes. In addition, both frameworks are capable of running applications on large, distributed-memory parallel machines. Currently, both these frameworks separately support assorted collections of physics packages related to HEDP, including one for the energy deposition by laser/ion-beam ray tracing. This study analyzes the options available for developing a common laser/ion-beam ray tracing package that can bemore » easily shared between these two code frameworks and concludes with a set of recommendations for its development.« less

Comparing numerical and analytic approximate gravitational waveforms

NASA Astrophysics Data System (ADS)

Afshari, Nousha; Lovelace, Geoffrey; SXS Collaboration

2016-03-01

A direct observation of gravitational waves will test Einstein's theory of general relativity under the most extreme conditions. The Laser Interferometer Gravitational-Wave Observatory, or LIGO, began searching for gravitational waves in September 2015 with three times the sensitivity of initial LIGO. To help Advanced LIGO detect as many gravitational waves as possible, a major research effort is underway to accurately predict the expected waves. In this poster, I will explore how the gravitational waveform produced by a long binary-black-hole inspiral, merger, and ringdown is affected by how fast the larger black hole spins. In particular, I will present results from simulations of merging black holes, completed using the Spectral Einstein Code (black-holes.org/SpEC.html), including some new, long simulations designed to mimic black hole-neutron star mergers. I will present comparisons of the numerical waveforms with analytic approximations.

A conservative MHD scheme on unstructured Lagrangian grids for Z-pinch hydrodynamic simulations

NASA Astrophysics Data System (ADS)

Wu, Fuyuan; Ramis, Rafael; Li, Zhenghong

2018-03-01

A new algorithm to model resistive magnetohydrodynamics (MHD) in Z-pinches has been developed. Two-dimensional axisymmetric geometry with azimuthal magnetic field Bθ is considered. Discretization is carried out using unstructured meshes made up of arbitrarily connected polygons. The algorithm is fully conservative for mass, momentum, and energy. Matter energy and magnetic energy are managed separately. The diffusion of magnetic field is solved using a derivative of the Symmetric-Semi-Implicit scheme, Livne et al. (1985) [23], where unconditional stability is obtained without needing to solve large sparse systems of equations. This MHD package has been integrated into the radiation-hydrodynamics code MULTI-2D, Ramis et al. (2009) [20], that includes hydrodynamics, laser energy deposition, heat conduction, and radiation transport. This setup allows to simulate Z-pinch configurations relevant for Inertial Confinement Fusion.

CO2 laser modeling

NASA Technical Reports Server (NTRS)

Johnson, Barry

1992-01-01

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.

Extraordinary Tools for Extraordinary Science: The Impact ofSciDAC on Accelerator Science&Technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryne, Robert D.

2006-08-10

Particle accelerators are among the most complex and versatile instruments of scientific exploration. They have enabled remarkable scientific discoveries and important technological advances that span all programs within the DOE Office of Science (DOE/SC). The importance of accelerators to the DOE/SC mission is evident from an examination of the DOE document, ''Facilities for the Future of Science: A Twenty-Year Outlook''. Of the 28 facilities listed, 13 involve accelerators. Thanks to SciDAC, a powerful suite of parallel simulation tools has been developed that represent a paradigm shift in computational accelerator science. Simulations that used to take weeks or more now takemore » hours, and simulations that were once thought impossible are now performed routinely. These codes have been applied to many important projects of DOE/SC including existing facilities (the Tevatron complex, the Relativistic Heavy Ion Collider), facilities under construction (the Large Hadron Collider, the Spallation Neutron Source, the Linac Coherent Light Source), and to future facilities (the International Linear Collider, the Rare Isotope Accelerator). The new codes have also been used to explore innovative approaches to charged particle acceleration. These approaches, based on the extremely intense fields that can be present in lasers and plasmas, may one day provide a path to the outermost reaches of the energy frontier. Furthermore, they could lead to compact, high-gradient accelerators that would have huge consequences for US science and technology, industry, and medicine. In this talk I will describe the new accelerator modeling capabilities developed under SciDAC, the essential role of multi-disciplinary collaboration with applied mathematicians, computer scientists, and other IT experts in developing these capabilities, and provide examples of how the codes have been used to support DOE/SC accelerator projects.« less

Extraordinary tools for extraordinary science: the impact of SciDAC on accelerator science and technology

NASA Astrophysics Data System (ADS)

Ryne, Robert D.

2006-09-01

Particle accelerators are among the most complex and versatile instruments of scientific exploration. They have enabled remarkable scientific discoveries and important technological advances that span all programs within the DOE Office of Science (DOE/SC). The importance of accelerators to the DOE/SC mission is evident from an examination of the DOE document, ''Facilities for the Future of Science: A Twenty-Year Outlook.'' Of the 28 facilities listed, 13 involve accelerators. Thanks to SciDAC, a powerful suite of parallel simulation tools has been developed that represent a paradigm shift in computational accelerator science. Simulations that used to take weeks or more now take hours, and simulations that were once thought impossible are now performed routinely. These codes have been applied to many important projects of DOE/SC including existing facilities (the Tevatron complex, the Relativistic Heavy Ion Collider), facilities under construction (the Large Hadron Collider, the Spallation Neutron Source, the Linac Coherent Light Source), and to future facilities (the International Linear Collider, the Rare Isotope Accelerator). The new codes have also been used to explore innovative approaches to charged particle acceleration. These approaches, based on the extremely intense fields that can be present in lasers and plasmas, may one day provide a path to the outermost reaches of the energy frontier. Furthermore, they could lead to compact, high-gradient accelerators that would have huge consequences for US science and technology, industry, and medicine. In this talk I will describe the new accelerator modeling capabilities developed under SciDAC, the essential role of multi-disciplinary collaboration with applied mathematicians, computer scientists, and other IT experts in developing these capabilities, and provide examples of how the codes have been used to support DOE/SC accelerator projects.

Human cadaver retina model for retinal heating during corneal surgery with a femtosecond laser

NASA Astrophysics Data System (ADS)

Sun, Hui; Fan, Zhongwei; Yun, Jin; Zhao, Tianzhuo; Yan, Ying; Kurtz, Ron M.; Juhasz, Tibor

2014-02-01

Femtosecond lasers are widely used in everyday clinical procedures to perform minimally invasive corneal refractive surgery. The intralase femtosecond laser (AMO Corp. Santa Ana, CA) is a common example of such a laser. In the present study a numerical simulation was developed to quantify the temperature rise in the retina during femtosecond intracorneal surgery. Also, ex-vivo retinal heating due to laser irradiation was measured with an infrared thermal camera (Fluke Corp. Everett, WA) as a validation of the simulation. A computer simulation was developed using Comsol Multiphysics to calculate the temperature rise in the cadaver retina during femtosecond laser corneal surgery. The simulation showed a temperature rise of less than 0.3 degrees for realistic pulse energies for the various repetition rates. Human cadaver retinas were irradiated with a 150 kHz Intralase femtosecond laser and the temperature rise was measured withan infrared thermal camera. Thermal camera measurements are in agreement with the simulation. During routine femtosecond laser corneal surgery with normal clinical parameters, the temperature rise is well beneath the threshold for retina damage. The simulation predictions are in agreement with thermal measurements providing a level of experimental validation.

Laser altimetry simulator. Version 3.0: User's guide

NASA Technical Reports Server (NTRS)

Abshire, James B.; Mcgarry, Jan F.; Pacini, Linda K.; Blair, J. Bryan; Elman, Gregory C.

1994-01-01

A numerical simulator of a pulsed, direct detection laser altimeter has been developed to investigate the performance of space-based laser altimeters operating over surfaces with various height profiles. The simulator calculates the laser's optical intensity waveform as it propagates to and is reflected from the terrain surface and is collected by the receiver telescope. It also calculates the signal and noise waveforms output from the receiver's optical detector and waveform digitizer. Both avalanche photodiode and photomultiplier detectors may be selected. Parameters of the detected signal, including energy, the 50 percent rise-time point, the mean timing point, and the centroid, can be collected into histograms and statistics calculated after a number of laser firings. The laser altimeter can be selected to be fixed over the terrain at any altitude. Alternatively, it can move between laser shots to simulate the terrain profile measured with the laser altimeter.

Range Resolved CO2 Atmospheric Backscattering Measurements Using Fiber Lasers and RZPN Code Modulation

NASA Technical Reports Server (NTRS)

Burris, John

2011-01-01

We report the use of a return-to- zero (RZPN) pseudo noise modulation technique for making range resolved measurements of CO2 within the planetary boundary layer (PBL) using commercial, off-the-shelf, components. Conventional, range resolved, DIAL measurements require laser pulse widths that are significantly shorter than the desired spatial resolution and necessitate using pulses whose temporal spacing is such that scattered returns from only a single pulse are observed by the receiver at any one time (for the PBL pulse separations must be greater than approximately 20 microseconds). This imposes significant operational limitations when using currently available fiber lasers because of the resulting low duty cycle (less than approximately 0.0005) and consequent low average laser output power. The RZPN modulation technique enables a fiber laser to operate at much higher duty cycles (approaching 0.04) thereby more effectively utilizing the amplifier's output. This increases the counts received by approximately two orders of magnitude. Our approach involves employing two distributed feedback lasers (DFB), each modulated by a different RPZN code, whose outputs are then amplified by a CW fiber amplifier. One laser is tuned to a CO2 absorption line; the other operates offline thereby permitting the simultaneous acquisition of both on and offline signals using independent RZPN codes. This minimizes the impact of atmospheric turbulence on the measurement. The on and offline signals are retrieved by deconvolving the return signal using the appropriate kernels.

Observation of 1-D time dependent non-propagating laser plasma structures using fluid and PIC codes

NASA Astrophysics Data System (ADS)

Verma, Deepa; Bera, Ratan Kumar; Kumar, Atul; Patel, Bhavesh; Das, Amita

2017-12-01

The manuscript reports the observation of time dependent localized and non-propagating structures in the coupled laser plasma system through 1-D fluid and Particle-In-Cell (PIC) simulations. It is reported that such structures form spontaneously as a result of collision amongst certain exact solitonic solutions. They are seen to survive as coherent entities for a long time up to several hundreds of plasma periods. Furthermore, it is shown that such time dependence can also be artificially recreated by significantly disturbing the delicate balance between the radiation and the density fields required for the exact non-propagating solution obtained by Esirkepov et al., JETP 68(1), 36-41 (1998). The ensuing time evolution is an interesting interplay between kinetic and field energies of the system. The electrostatic plasma oscillations are coupled with oscillations in the electromagnetic field. The inhomogeneity of the background and the relativistic nature, however, invariably produces large amplitude density perturbations leading to its wave breaking. In the fluid simulations, the signature of wave breaking can be discerned by a drop in the total energy which evidently gets lost to the grid. The PIC simulations are observed to closely follow the fluid simulations till the point of wave breaking. However, the total energy in the case of PIC simulations is seen to remain conserved throughout the simulations. At the wave breaking, the particles are observed to acquire thermal kinetic energy in the case of PIC. Interestingly, even after wave breaking, compact coherent structures with trapped radiation inside high-density peaks continue to exist both in PIC and fluid simulations. Although the time evolution does not exactly match in the two simulations as it does prior to the process of wave breaking, the time-dependent features exhibited by the remnant structures are characteristically similar.

Refined Simulation of Satellite Laser Altimeter Full Echo Waveform

NASA Astrophysics Data System (ADS)

Men, H.; Xing, Y.; Li, G.; Gao, X.; Zhao, Y.; Gao, X.

2018-04-01

The return waveform of satellite laser altimeter plays vital role in the satellite parameters designation, data processing and application. In this paper, a method of refined full waveform simulation is proposed based on the reflectivity of the ground target, the true emission waveform and the Laser Profile Array (LPA). The ICESat/GLAS data is used as the validation data. Finally, we evaluated the simulation accuracy with the correlation coefficient. It was found that the accuracy of echo simulation could be significantly improved by considering the reflectivity of the ground target and the emission waveform. However, the laser intensity distribution recorded by the LPA has little effect on the echo simulation accuracy when compared with the distribution of the simulated laser energy. At last, we proposed a refinement idea by analyzing the experimental results, in the hope of providing references for the waveform data simulation and processing of GF-7 satellite in the future.

Flight Tasks and Metrics to Evaluate Laser Eye Protection in Flight Simulators

DTIC Science & Technology

2017-07-07

AFRL-RH-FS-TR-2017-0026 Flight Tasks and Metrics to Evaluate Laser Eye Protection in Flight Simulators Thomas K. Kuyk Peter A. Smith Solangia...34Flight Tasks and Metrics to Evaluate Laser Eye Protection in Flight Simulators" (AFRL-RH-FS-TR- 2017 - 0026 SHORTER.PATRI CK.D.1023156390 Digitally...SUBTITLE Flight Tasks and Metrics to Evaluate Laser Eye Protection in Flight Simulators 5a. CONTRACT NUMBER FA8650-14-D-6519 5b. GRANT NUMBER 5c

Proceedings of the 14th International Conference on the Numerical Simulation of Plasmas

NASA Astrophysics Data System (ADS)

Partial Contents are as follows: Numerical Simulations of the Vlasov-Maxwell Equations by Coupled Particle-Finite Element Methods on Unstructured Meshes; Electromagnetic PIC Simulations Using Finite Elements on Unstructured Grids; Modelling Travelling Wave Output Structures with the Particle-in-Cell Code CONDOR; SST--A Single-Slice Particle Simulation Code; Graphical Display and Animation of Data Produced by Electromagnetic, Particle-in-Cell Codes; A Post-Processor for the PEST Code; Gray Scale Rendering of Beam Profile Data; A 2D Electromagnetic PIC Code for Distributed Memory Parallel Computers; 3-D Electromagnetic PIC Simulation on the NRL Connection Machine; Plasma PIC Simulations on MIMD Computers; Vlasov-Maxwell Algorithm for Electromagnetic Plasma Simulation on Distributed Architectures; MHD Boundary Layer Calculation Using the Vortex Method; and Eulerian Codes for Plasma Simulations.

Characterization of plasma wake excitation and particle trapping in the nonlinear bubble regime

NASA Astrophysics Data System (ADS)

Benedetti, Carlo; Schroeder, Carl; Esarey, Eric; Leemans, Wim

2010-11-01

We investigate the excitation of nonlinear wake (bubble) formation by an ultra-short (kpL ˜2), intense (e Alaser/mc^2 > 2) laser pulse interacting with an underdense plasma. A detailed analysis of particle orbits in the wakefield is performed by using reduced analytical models and numerical simulations performed with the 2D cylindrical, envelope, ponderomotive, hybrid PIC/fluid code INF&RNO, recently developed at LBNL. In particular we study the requirements for injection and/or trapping of background plasma electrons in the nonlinear wake. Characterization of the phase-space properties of the injected particle bunch will also be discussed.

A Quantitative Analysis of the Relationship between Medicare Payment and Service Volume for Glaucoma Procedures from 2005 through 2009.

PubMed

Gong, Dan; Jun, Lin; Tsai, James C

2015-05-01

To calculate the association between Medicare payment and service volume for 6 commonly performed glaucoma procedures. Retrospective, longitudinal database study. A 100% dataset of all glaucoma procedures performed on Medicare Part B beneficiaries within the United States from 2005 to 2009. Fixed-effects regression model using Medicare Part B carrier data for all 50 states and the District of Columbia, controlling for time-invariant carrier-specific characteristics, national trends in glaucoma service volume, Medicare beneficiary population, number of ophthalmologists, and income per capita. Payment-volume elasticities, defined as the percent change in service volume per 1% change in Medicare payment, for laser trabeculoplasty (Current Procedural Terminology [CPT] code 65855), trabeculectomy without previous surgery (CPT code 66170), trabeculectomy with previous surgery (CPT code 66172), aqueous shunt to reservoir (CPT code 66180), laser iridotomy (CPT code 66761), and scleral reinforcement with graft (CPT code 67255). The payment-volume elasticity was nonsignificant for 4 of 6 procedures studied: laser trabeculoplasty (elasticity, -0.27; 95% confidence interval [CI], -1.31 to 0.77; P = 0.61), trabeculectomy without previous surgery (elasticity, -0.42; 95% CI, -0.85 to 0.01; P = 0.053), trabeculectomy with previous surgery (elasticity, -0.28; 95% CI, -0.83 to 0.28; P = 0.32), and aqueous shunt to reservoir (elasticity, -0.47; 95% CI, -3.32 to 2.37; P = 0.74). Two procedures yielded significant associations between Medicare payment and service volume. For laser iridotomy, the payment-volume elasticity was -1.06 (95% CI, -1.39 to -0.72; P < 0.001): for every 1% decrease in CPT code 66761 payment, laser iridotomy service volume increased by 1.06%. For scleral reinforcement with graft, the payment-volume elasticity was -2.92 (95% CI, -5.72 to -0.12; P = 0.041): for every 1% decrease in CPT code 67255 payment, scleral reinforcement with graft service volume increased by 2.92%. This study calculated the association between Medicare payment and service volume for 6 commonly performed glaucoma procedures and found varying magnitudes of payment-volume elasticities, suggesting that the volume response to changes in Medicare payments, if present, is not uniform across all Medicare procedures. Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Constraining heat-transport models by comparison to experimental data in a NIF hohlraum

NASA Astrophysics Data System (ADS)

Farmer, W. A.; Jones, O. S.; Barrios Garcia, M. A.; Koning, J. M.; Kerbel, G. D.; Strozzi, D. J.; Hinkel, D. E.; Moody, J. D.; Suter, L. J.; Liedahl, D. A.; Moore, A. S.; Landen, O. L.

2017-10-01

The accurate simulation of hohlraum plasma conditions is important for predicting the partition of energy and the symmetry of the x-ray field within a hohlraum. Electron heat transport within the hohlraum plasma is difficult to model due to the complex interaction of kinetic plasma effects, magnetic fields, laser-plasma interactions, and microturbulence. Here, we report simulation results using the radiation-hydrodynamic code, HYDRA, utilizing various physics packages (e.g., nonlocal Schurtz model, MHD, flux limiters) and compare to data from hohlraum plasma experiments which contain a Mn-Co tracer dot. In these experiments, the dot is placed in various positions in the hohlraum in order to assess the spatial variation of plasma conditions. Simulated data is compared to a variety of experimental diagnostics. Conclusions are given concerning how the experimental data does and does not constrain the physics models examined. This work was supported by the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Tunneling ionization and Wigner transform diagnostics in OSIRIS

NASA Astrophysics Data System (ADS)

Martins, S.; Fonseca, R. A.; Silva, L. O.; Deng, S.; Katsouleas, T.; Tsung, F.; Mori, W. B.

2004-11-01

We describe the ionization module implemented in the PIC code OSIRIS [1]. Benchmarks with previously published tunnel ionization results were made. Our ionization module works in 1D, 2D and 3D simulations with barrier suppression ionization or the ADK ionization model, and allows for moving ions. Several illustrative 3D numerical simulations were performed, namely of the propagation of a SLAC beam in a Li gas cell, for the parameters of [2]. We compare the performance of OSIRIS with/without the ionization module, concluding that much less simulation time is usually required when using the ionization module. A novel diagnostic over the electric field is implemented, the Wigner transform, that provides information on the local spectral content of the field. This diagnostic is applied to the analysis of the chirp induced in an ionizing laser pulse. [1] R. A. Fonseca et al., LNCS 2331, 342-351, (Springer, Heidelberg, 2002). [2] S. Deng et al., Phys. Rev. E 68, 047401 (2003).

Numerical modeling of laser-driven experiments aiming to demonstrate magnetic field amplification via turbulent dynamo

DOE PAGES

Tzeferacos, Petros; Rigby, A.; Bott, A.; ...

2017-03-22

The universe is permeated by magnetic fields, with strengths ranging from a femtogauss in the voids between the filaments of galaxy clusters to several teragauss in black holes and neutron stars. The standard model behind cosmological magnetic fields is the nonlinear amplification of seed fields via turbulent dynamo to the values observed. We have conceived experiments that aim to demonstrate and study the turbulent dynamo mechanism in the laboratory. Here, we describe the design of these experiments through simulation campaigns using FLASH, a highly capable radiation magnetohydrodynamics code that we have developed, and large-scale three-dimensional simulations on the Mira supercomputermore » at the Argonne National Laboratory. The simulation results indicate that the experimental platform may be capable of reaching a turbulent plasma state and determining the dynamo amplification. As a result, we validate and compare our numerical results with a small subset of experimental data using synthetic diagnostics.« less

Validation and verification of the laser range safety tool (LRST)

NASA Astrophysics Data System (ADS)

Kennedy, Paul K.; Keppler, Kenneth S.; Thomas, Robert J.; Polhamus, Garrett D.; Smith, Peter A.; Trevino, Javier O.; Seaman, Daniel V.; Gallaway, Robert A.; Crockett, Gregg A.

2003-06-01

The U.S. Dept. of Defense (DOD) is currently developing and testing a number of High Energy Laser (HEL) weapons systems. DOD range safety officers now face the challenge of designing safe methods of testing HEL's on DOD ranges. In particular, safety officers need to ensure that diffuse and specular reflections from HEL system targets, as well as direct beam paths, are contained within DOD boundaries. If both the laser source and the target are moving, as they are for the Airborne Laser (ABL), a complex series of calculations is required and manual calculations are impractical. Over the past 5 years, the Optical Radiation Branch of the Air Force Research Laboratory (AFRL/HEDO), the ABL System Program Office, Logicon-RDA, and Northrup-Grumman, have worked together to develop a computer model called teh Laser Range Safety Tool (LRST), specifically designed for HEL reflection hazard analyses. The code, which is still under development, is currently tailored to support the ABL program. AFRL/HEDO has led an LRST Validation and Verification (V&V) effort since 1998, in order to determine if code predictions are accurate. This paper summarizes LRST V&V efforts to date including: i) comparison of code results with laboratory measurements of reflected laser energy and with reflection measurements made during actual HEL field tests, and ii) validation of LRST's hazard zone computations.

Augmented burst-error correction for UNICON laser memory. [digital memory

NASA Technical Reports Server (NTRS)

Lim, R. S.

1974-01-01

A single-burst-error correction system is described for data stored in the UNICON laser memory. In the proposed system, a long fire code with code length n greater than 16,768 bits was used as an outer code to augment an existing inner shorter fire code for burst error corrections. The inner fire code is a (80,64) code shortened from the (630,614) code, and it is used to correct a single-burst-error on a per-word basis with burst length b less than or equal to 6. The outer code, with b less than or equal to 12, would be used to correct a single-burst-error on a per-page basis, where a page consists of 512 32-bit words. In the proposed system, the encoding and error detection processes are implemented by hardware. A minicomputer, currently used as a UNICON memory management processor, is used on a time-demanding basis for error correction. Based upon existing error statistics, this combination of an inner code and an outer code would enable the UNICON system to obtain a very low error rate in spite of flaws affecting the recorded data.

Time-dependent wave front propagation simulation of a hard x-ray split-and-delay unit: Towards a measurement of the temporal coherence properties of x-ray free electron lasers

DOE PAGES

Roling, S.; Zacharias, H.; Samoylova, L.; ...

2014-11-18

For the European x-ray free electron laser (XFEL) a split-and-delay unit based on geometrical wavefront beam splitting and multilayer mirrors is built which covers the range of photon energies from 5 keV up to 20 keV. Maximum delays between Δτ = ±2.5 ps at hν=20 keV and up to Δτ = ±23 ps at hν = 5 keV will be possible. Time-dependent wave-optics simulations have been performed by means of Synchrotron Radiation Workshop software for XFEL pulses at hν = 5 keV. The XFEL radiation was simulated using results of time-dependent simulations applying the self-amplified spontaneous emission code FAST. Mainmore » features of the optical layout, including diffraction on the beam splitter edge and optics imperfections measured with a nanometer optic component measuring machine slope measuring profiler, were taken into account. The impact of these effects on the characterization of the temporal properties of XFEL pulses is analyzed. An approach based on fast Fourier transformation allows for the evaluation of the temporal coherence despite large wavefront distortions caused by the optics imperfections. In this manner, the fringes resulting from time-dependent two-beam interference can be filtered and evaluated yielding a coherence time of τ c = 0.187 fs (HWHM) for real, nonperfect mirrors, while for ideal mirrors a coherence time of τ c = 0.191 fs (HWHM) is expected.« less

Computer simulation of a multiple-aperture coherent laser radar

NASA Astrophysics Data System (ADS)

Gamble, Kevin J.; Weeks, Arthur R.

1996-06-01

This paper presents the construction of a 2D multiple aperture coherent laser radar simulation that is capable of including the effects of the time evolution of speckle on the laser radar output. Every portion of a laser radar system is modeled in software, including quarter and half wave plates, beamsplitters (polarizing and non-polarizing), the detector, the laser source, and all necessary lenses. Free space propagation is implemented using the Rayleigh- Sommerfeld integral for both orthogonal polarizations. Atmospheric turbulence is also included in the simulation and is modeled using time correlated Kolmogorov phase screens. The simulation itself can be configured to simulate both monostatic and bistatic systems. The simulation allows the user to specify component level parameters such as extinction ratios for polarizing beam splitters, detector sizes and shapes. orientation of the slow axis for quarter/half wave plates and other components used in the system. This is useful from a standpoint of being a tool in the design of a multiple aperture laser radar system.

Simulation of laser beam reflection at the sea surface

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2011-05-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for both the calculation of images of SWIR (short wave infrared) imaging sensor and for determination of total detected power of reflected laser light for a bistatic configuration of laser source and receiver at different atmospheric conditions. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. The propagation model for water waves is applied for sea surface animation. To predict the view of a camera in the spectral band SWIR the sea surface radiance must be calculated. This is done by considering the emitted sea surface radiance and the reflected sky radiance, calculated by MODTRAN. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled in the SWIR band considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). This BRDF model considers the statistical slope statistics of waves and accounts for slope-shadowing of waves that especially occurs at flat incident angles of the laser beam and near horizontal detection angles of reflected irradiance at rough seas. Simulation results are presented showing the variation of the detected laser power dependent on the geometric configuration of laser, sensor and wind characteristics.

Laser Linewidth Requirements for Optical Bpsk and Qpsk Heterodyne Lightwave Systems.

NASA Astrophysics Data System (ADS)

Boukli-Hacene, Mokhtar

In this dissertation, optical Binary Phase-Shift Keying (BPSK) and Quadrature Phase-Shift Keying (QPSK) heterodyne communication receivers are investigated. The main objective of this research work is to analyze the performance of these receivers in the presence of laser phase noise and shot noise. The heterodyne optical BPSK is based on the square law carrier recovery (SLCR) scheme for phase detection. The BPSK heterodyne receiver is analyzed assuming a second order linear phase-locked loop (PLL) subsystem and a small phase error. The noise properties are analyzed and the problem of minimizing the effect of noise is addressed. The performance of the receiver is evaluated in terms of the bit error rate (BER), which leads to the analysis of the BER versus the laser linewidth and the number of photons/bit to achieve good performance. Since we cannot track the pure carrier component in the presence of noise, a non-linear model is used to solve the problem of recovery of the carrier. The non -linear system is analyzed in the presence of a low signal -to-noise ratio (SNR). The non-Gaussian noise model represented by its probability density function (PDF) is used to analyze the performance of the receiver, especially the phase error. In addition the effect of the PLL is analyzed by studying the cycle slippage (cs). Finally, the research effort is expanded from BPSK to QPSK systems. The heterodyne optical QPSK based on the fourth power multiplier scheme (FPMS) in conjunction with linear and non-linear PLL model is investigated. Optimum loop and higher power penalty in the presence of phase noise and shot noise are analyzed. It is shown that the QPSK system yields a high speed and high sensitivity coherent means for transmission of information accompanied by a small degradation in the laser linewidth. Comparative analysis of BPSK and QPSK systems leads us to conclude that in terms of laser linewidth, bit rate, phase error and power penalty, the QPSK system is more sensitive than the BPSK system and suffers less from higher power penalty. The BPSK and QPSK heterodyne receivers used in the uncoded scheme demand a realistic laser linewidth. Since the laser linewidth is the critical measure of the performance of a receiver, a convolutional code applied to QPSK of the system is used to improve the sensitivity of the system. The effect of coding is particularly important as means of relaxing the laser linewidth requirement. The validity and usefulness of the analysis presented in the dissertation is supported by computer simulations.

Thermally induced distortion of a high-average-power laser system by an optical transport system

NASA Astrophysics Data System (ADS)

Chow, Robert; Ault, Linda E.; Taylor, John R.; Jedlovec, Don

1999-11-01

The atomic vapor laser isotope separation process uses high- average power lasers that have the commercial potential to enrich uranium for the electric power utilities. The transport of the laser beam through the laser system to the separation chambers requires high performance optical components, most of which have either fused silica or Zerodur as the substrate material. One of the requirements of the optical components is to preserve the wavefront quality of the laser beam that propagate over long distances. Full aperture tests with the high power process lasers and finite element analysis (FEA) have been performed on the transport optics. The wavefront distortions of the various sections of the transport path were measured with diagnostic Hartmann sensor packages. The FEA results were derived from an in-house thermal-structural- optical code which is linked to the commercially available CodeV program. In comparing the measured and predicted results, the bulk absorptance of fused silica was estimated to about 50 ppm/cm in the visible wavelength regime. Wavefront distortions will be reported on optics made from fused silica and Zerodur substrate materials.

Laser Scanner For Automatic Storage

NASA Astrophysics Data System (ADS)

Carvalho, Fernando D.; Correia, Bento A.; Rebordao, Jose M.; Rodrigues, F. Carvalho

1989-01-01

The automated magazines are beeing used at industry more and more. One of the problems related with the automation of a Store House is the identification of the products envolved. Already used for stock management, the Bar Codes allows an easy way to identify one product. Applied to automated magazines, the bar codes allows a great variety of items in a small code. In order to be used by the national producers of automated magazines, a devoted laser scanner has been develloped. The Prototype uses an He-Ne laser whose beam scans a field angle of 75 degrees at 16 Hz. The scene reflectivity is transduced by a photodiode into an electrical signal, which is then binarized. This digital signal is the input of the decodifying program. The machine is able to see barcodes and to decode the information. A parallel interface allows the comunication with the central unit, which is responsible for the management of automated magazine.

In-orbit verification of small optical transponder (SOTA): evaluation of satellite-to-ground laser communication links

NASA Astrophysics Data System (ADS)

Takenaka, Hideki; Koyama, Yoshisada; Akioka, Maki; Kolev, Dimitar; Iwakiri, Naohiko; Kunimori, Hiroo; Carrasco-Casado, Alberto; Munemasa, Yasushi; Okamoto, Eiji; Toyoshima, Morio

2016-03-01

Research and development of space optical communications is conducted in the National Institute of Information and Communications Technology (NICT). The NICT developed the Small Optical TrAnsponder (SOTA), which was embarked on a 50kg-class satellite and launched into a low earth orbit (LEO). The space-to-ground laser communication experiments have been conducted with the SOTA. Atmospheric turbulence causes signal fadings and becomes an issue to be solved in satellite-to-ground laser communication links. Therefore, as error-correcting functions, a Reed-Solomon (RS) code and a Low-Density Generator Matrix (LDGM) code are implemented in the communication system onboard the SOTA. In this paper, we present the in-orbit verification results of SOTA including the characteristic of the functions, the communication performance with the LDGM code via satellite-to-ground atmospheric paths, and the link budget analysis and the comparison between theoretical and experimental results.

Performance calculation and simulation system of high energy laser weapon

NASA Astrophysics Data System (ADS)

Wang, Pei; Liu, Min; Su, Yu; Zhang, Ke

2014-12-01

High energy laser weapons are ready for some of today's most challenging military applications. Based on the analysis of the main tactical/technical index and combating process of high energy laser weapon, a performance calculation and simulation system of high energy laser weapon was established. Firstly, the index decomposition and workflow of high energy laser weapon was proposed. The entire system was composed of six parts, including classical target, platform of laser weapon, detect sensor, tracking and pointing control, laser atmosphere propagation and damage assessment module. Then, the index calculation modules were designed. Finally, anti-missile interception simulation was performed. The system can provide reference and basis for the analysis and evaluation of high energy laser weapon efficiency.

Characterizing Hohlraum Plasma Conditions at the National Ignition Facility (NIF) Using X-ray Spectroscopy

NASA Astrophysics Data System (ADS)

Barrios, Maria Alejandra

2015-11-01

Improved hohlraums will have a significant impact on increasing the likelihood of indirect drive ignition at the NIF. In indirect-drive Inertial Confinement Fusion (ICF), a high-Z hohlraum converts laser power into a tailored x-ray flux that drives the implosion of a spherical capsule filled with D-T fuel. The x-radiation drive to capsule coupling sets the velocity, adiabat, and symmetry of the implosion. Previous experiments in gas-filled hohlraums determined that the laser-hohlraum energy coupling is 20-25% less than modeled, therefore identifying energy loss mechanisms that reduce the efficacy of the hohlraum drive is central to improving implosion performance. Characterizing the plasma conditions, particularly the plasma electron temperature (Te) , is critical to understanding mechanism that affect the energy coupling such as the laser plasma interactions (LPI), hohlraum x-ray conversion efficiency, and dynamic drive symmetry. The first Te measurements inside a NIF hohlraum, presented here, were achieved using K-shell X-ray spectroscopy of an Mn-Co tracer dot. The dot is deposited on a thin-walled CH capsule, centered on the hohlraum symmetry axis below the laser entrance hole (LEH) of a bottom-truncated hohlraum. The hohlraum x-ray drive ablates the dot and causes it to flow upward, towards the LEH, entering the hot laser deposition region. An absolutely calibrated streaked spectrometer with a line of sight into the LEH records the temporal history of the Mn and Co X-ray emission. The measured (interstage) Lyα/ Heα line ratios for Co and Mn and the Mn-Heα/Co-Heα isoelectronic line ratio are used to infer the local plasma Te from the atomic physics code SCRAM. Time resovled x-ray images perpendicular to the hohlraum axis record the dot expansion and trajectory into the LEH region. The temporal evolution of the measured Te and dot trajectory are compared with simulations from radiation-hydrodynamic codes. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

The stimulated Brillouin scattering during the interaction of picosecond laser pulses with moderate- scale-length plasmas

NASA Astrophysics Data System (ADS)

Gaeris, Andres Claudio

The Stimulated Brillouin Scattering (SBS) instability is studied in moderately short scale-length plasmas. The backscattered and specularly reflected light resulting from the interaction of a pair of high power picosecond duration laser pulses with solid Silicon, Gold and Parylene-N (CH) strip targets was spectrally resolved. The first, weaker laser pulse forms a short scale-length plasma while the second delayed one interacts with the isothermally expanded, underdense region of the plasma. The pulses are generated by the Table Top Terawatt (TTT) laser operating at 1054 nm (infrared) with intensities up to 5.10 16 W/cm2. Single laser pulses only show Lambertian scattering on the target critical surface. Pairs of pulses with high intensity in the second pulse show an additional backscattered, highly blueshifted feature, associated with SBS. Increasing this second pulse intensity even more leads to the appearance of a third feature, even more blueshifted than the second, resulting from the Brillouin sidescattering of the laser pulse reflected on the critical surface. The SBS threshold intensities and enhanced reflectivities for P-polarized light are determined for different plasma density scale-lengths. These measurements agree with the convective thresholds predicted by the SBS theory of Liu, Rosenbluth, and White using plasma profiles simulated by the LILAC code. The spectral position of the Brillouin back- and sidescattered features are determined. The SBS and Doppler shifts are much too small to explain the observed blueshifts. The refractive index shift is of the right magnitude, although more detailed verification is required in the future.

Laser-initiated channels for ion transport: breakdown and channel evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olsen, J.N.; Baker, L.

1981-05-01

The electrical breakdown and discharge evolution in CO/sub 2/ laser-heated molecular gases has been studied. With the laser tuned to a vibrational mode of NH/sub 3/, C/sub 2/H/sub 4/, CH/sub 2/CHCN, or CH/sub 3/OH the breakdown potential decreases as much as 10-fold for laser pulse energies up to 35 J/cm/sup 2/. The subsequent 50--142-cm discharges are straight, stable, and reproducible. Analogous tests in D/sub 2/ and air yield only a small alteration of breakdown potential and do not cause a straight discharge. The expansion of the initial laser-heated gas has been modeled by the CHARTB hydrocode with the addition ofmore » the NH/sub 3/ equation of state in tabular and analytic form to that code. The breakdown characteristics and initial expansion stage confirm the earlier calculation of laser heating to 1900--2100 /sup 0/K. Experimental observations of the discharge evolution in NH/sub 3/ have measured (1) the radial expansion velocity by streak-camera photography of the H/sub ..beta../ emission zone, (2) the plasma temperature by the Niv/Niii line-ratio method, and (3) the electron-density profile by holographic interferometry. The central zone of the channel is heated to 5.5 eV and expands with a radial velocity of 1.0--1.2 mm/..mu..s for the case of a 27-kA discharge in 20 Torr of NH/sub 3/. Preliminary hydrocode simulations of the discharge show qualitative agreement with observations.« less

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, K. S.

1986-01-01

During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator were carried out before amplifier studies. The amplifier studies are postponed to the extended period after completing the parametric studies. In addition, the kinetic modeling of a solar-pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) a 10 W CW iodine laser pumped by a Vortek solar simulator; (2) kinetic modeling to predict the time to lasing threshold, lasing time, and energy output of solar-pumped iodine laser; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

Interaction of intense laser pulses with gas for two-color THz generation and remote magnetometry

NASA Astrophysics Data System (ADS)

Johnson, Luke A.

The interaction of intense laser pulses with atmospheric gases is studied in two contexts: (i) the generation of broadband terahertz radiation via two-color photoionization currents in nitrogen, and (ii) the generation of an electromagnetic wakefield by the induced magnetization currents of oxygen. (i) A laser pulse propagation simulation code was developed to investigate the radiation patterns from two-color THz generation in nitrogen. Understanding the mechanism for conical, two-color THz furthers the development of broadband THz sources. Two-color photoionization produces a cycle-averaged current driving broadband, conically emitted THz radiation. The THz emission angle is found to be determined by an optical Cherenkov effect, occurring when the front velocity of the ionization induced current source is greater than the THz phase velocity. (ii) A laser pulse propagating in the atmosphere is capable of exciting a magnetic dipole transition in molecular oxygen. The resulting transient current creates a co-propagating electromagnetic field behind the laser pulse, i.e. the wakefield, which has a rotated polarization that depends on the background magnetic field. This effect is analyzed to determine it's suitability for remote atmospheric magnetometry for the detection of underwater and underground objects. In the proposed approach, Kerr self-focusing is used to bring a polarized, high-intensity, laser pulse to focus at a remote detection site where the laser pulse induces a ringing in the oxygen magnetization. The detection signature for underwater and underground objects is the change in the wakefield polarization between different measurement locations. The magnetic dipole transition line that is considered is the b-X transition band of oxygen near 762 nm.

Extended x-ray absorption fine structure measurements of quasi-isentropically compressed vanadium targets on the OMEGA laser

NASA Astrophysics Data System (ADS)

Yaakobi, B.; Boehly, T. R.; Sangster, T. C.; Meyerhofer, D. D.; Remington, B. A.; Allen, P. G.; Pollaine, S. M.; Lorenzana, H. E.; Lorenz, K. T.; Hawreliak, J. A.

2008-06-01

The use of in situ extended x-ray absorption fine structure (EXAFS) for characterizing nanosecond laser-shocked vanadium, titanium, and iron has recently been demonstrated. These measurements are extended to laser-driven, quasi-isentropic compression experiments (ICE). The radiation source (backlighter) for EXAFS in all of these experiments is obtained by imploding a spherical target on the OMEGA laser [T. R. Boehly et al., Rev. Sci. Instrum. 66, 508 (1995)]. Isentropic compression (where the entropy is kept constant) enables to reach high compressions at relatively low temperatures. The absorption spectra are used to determine the temperature and compression in a vanadium sample quasi-isentropically compressed to pressures of up to ˜0.75Mbar. The ability to measure the temperature and compression directly is unique to EXAFS. The drive pressure is calibrated by substituting aluminum for the vanadium and interferometrically measuring the velocity of the back target surface by the velocity interferometer system for any reflector (VISAR). The experimental results obtained by EXAFS and VISAR agree with each other and with the simulations of a hydrodynamic code. The role of a shield to protect the sample from impact heating is studied. It is shown that the shield produces an initial weak shock that is followed by a quasi-isentropic compression at a relatively low temperature. The role of radiation heating from the imploding target as well as from the laser-absorption region is studied. The results show that in laser-driven ICE, as compared with laser-driven shocks, comparable compressions can be achieved at lower temperatures. The EXAFS results show important details not seen in the VISAR results.

LLE review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bradley, D.K.

1989-01-01

This volume of the LLE Review, covering the period October--December 1989, contains an article discussing saturation effects and power-balance considerations in the design of high-power lasers and an article describing numerical modeling of the effects of power imbalances on target behavior. The advanced technology section reports on the development of a liquid crystal laser-beam apodizer and an experiment to study the high-intensity ionization of noble gases. Finally, the activities of the National Laser Users Facility and the GDL and OMEGA laser facilities are summarized. The highlights of this issue are: The problem of achieving power balance in high-efficiency, multibeam lasersmore » has been studied in terms of gain-saturation effects and the nonlinear nature of harmonic frequency conversion. It is shown that power imbalance can be minimized by balancing the gains and losses in equivalent amplification stages in each beamline. The effects of target implosion behavior of various power-imbalance sources in the OMEGA laser system have been studied using the two-dimensional hydrodynamics code ORCHID. The simulations show good agreement with an experiment in which a deliberate power imbalance was applied to the target drive. Laser-beam apodizers with large clear apertures have been fabricated using cholesteric liquid crystals. A soft-edge profile has been achieved by filling a cell with two separate liquid crystals with different selective-reflection bands, and allowing them to partially mix at the interface. A study of the ionization of noble gases in the tunneling regime using high- intensity, 1-ps pulses from the tabletop terawatt laser (T{sup 3}) has been carried out. The measured ion production is well predicted by a Coulomb barrier suppression ionization theory.« less

Simulation of a polarized laser beam reflected at the sea surface: modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric

2015-05-01

A 3-D simulation of the polarization-dependent reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation considers polarized or unpolarized laser sources and calculates the polarization states upon reflection at the sea surface. It is suitable for the radiance calculation of the scene in different spectral wavebands (e.g. near-infrared, SWIR, etc.) not including the camera degradations. The simulation also considers a bistatic configuration of laser source and receiver as well as different atmospheric conditions. In the SWIR, the detected total power of reflected laser light is compared with data collected in a field trial. Our computer simulation combines the 3-D simulation of a maritime scene (open sea/clear sky) with the simulation of polarized or unpolarized laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the input of a camera equipped with a linear polarizer, the polarized sea surface radiance must be calculated for the specific waveband. The s- and p-polarization states are calculated for the emitted sea surface radiance and the specularly reflected sky radiance to determine the total polarized sea surface radiance of each component. The states of polarization and the radiance of laser light specularly reflected at the wind-roughened sea surface are calculated by considering the s- and p- components of the electric field of laser light with respect to the specular plane of incidence. This is done by using the formalism of their coherence matrices according to E. Wolf [1]. Additionally, an analytical statistical sea surface BRDF (bidirectional reflectance distribution function) is considered for the reflection of laser light radiances. Validation of the simulation results is required to ensure model credibility and applicability to maritime laser applications. For validation purposes, field measurement data (images and meteorological data) was analyzed. An infrared laser, with or without a mounted polarizer, produced laser beam reflection at the water surface and images were recorded by a camera equipped with a polarizer with horizontal or vertical alignment. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam and different alignment for the laser polarizers (vertical/horizontal/without) and the camera (vertical/horizontal).

Effects of electron recirculation on a hard x-ray source observed during the interaction of a high intensity laser pulse with thin Au targets

NASA Astrophysics Data System (ADS)

Compant La Fontaine, A.; Courtois, C.; Lefebvre, E.; Bourgade, J. L.; Landoas, O.; Thorp, K.; Stoeckl, C.

2013-12-01

The interaction of a high intensity laser pulse on the preplasma of a high-Z solid target produced by the pulse's pedestal generates high-energy electrons. These electrons subsequently penetrate inside the solid target and produce bremsstrahlung photons, generating an x-ray source which can be used for photonuclear studies or to radiograph high area density objects. The source characteristics are compared for targets with thin (20 μm) and thick (100 μm) Au foils on the Omega EP laser at Laboratory for Laser Energetics. Simulations using the particle-in-cell code CALDER show that for a 20 μm thickness Au target, electrons perform multiple round-trips in the target under the effect of the laser ponderomotive potential and the target electrostatic potential. These relativistic electrons have random transverse displacements, with respect to the target normal, attributed to electrostatic fluctuation fields. As a result, the x-ray spot size is increased by a factor 2 for thin target compared to thick targets, in agreement with experimental results. In addition, the computed doses agree with the measured ones provided that electron recirculation in the thin target is taken into account. A dose increase by a factor 1.7 is then computed by allowing for recirculation. In the 100 μm target case, on the other hand, this effect is found to be negligible.

Finite Element Analysis of Interaction of Laser Beam with Material in Laser Metal Powder Bed Fusion Process.

PubMed

Fu, Guang; Zhang, David Z; He, Allen N; Mao, Zhongfa; Zhang, Kaifei

2018-05-10

A deep understanding of the laser-material interaction mechanism, characterized by laser absorption, is very important in simulating the laser metal powder bed fusion (PBF) process. This is because the laser absorption of material affects the temperature distribution, which influences the thermal stress development and the final quality of parts. In this paper, a three-dimensional finite element analysis model of heat transfer taking into account the effect of material state and phase changes on laser absorption is presented to gain insight into the absorption mechanism, and the evolution of instantaneous absorptance in the laser metal PBF process. The results showed that the instantaneous absorptance was significantly affected by the time of laser radiation, as well as process parameters, such as hatch space, scanning velocity, and laser power, which were consistent with the experiment-based findings. The applicability of this model to temperature simulation was demonstrated by a comparative study, wherein the peak temperature in fusion process was simulated in two scenarios, with and without considering the effect of material state and phase changes on laser absorption, and the simulated results in the two scenarios were then compared with experimental data respectively.

Laser Signature Prediction Using The VALUE Computer Program

NASA Astrophysics Data System (ADS)

Akerman, Alexander; Hoffman, George A.; Patton, Ronald

1989-09-01

A variety of enhancements are being made to the 1976-vintage LASERX computer code. These include: - Surface characterization with BDRF tabular data - Specular reflection from transparent surfaces - Generation of glint direction maps - Generation of relative range imagery - Interface to the LOWTRAN atmospheric transmission code - Interface to the LEOPS laser sensor code - User friendly menu prompting for easy setup Versions of VALUE have been written for both VAX/VMS and PC/DOS computer environments. Outputs have also been revised to be user friendly and include tables, plots, and images for (1) intensity, (2) cross section,(3) reflectance, (4) relative range, (5) region type, and (6) silhouette.

System Modeling of kJ-class Petawatt Lasers at LLNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shverdin, M Y; Rushford, M; Henesian, M A

2010-04-14

Advanced Radiographic Capability (ARC) project at the National Ignition Facility (NIF) is designed to produce energetic, ultrafast x-rays in the range of 70-100 keV for backlighting NIF targets. The chirped pulse amplification (CPA) laser system will deliver kilo-Joule pulses at an adjustable pulse duration from 1 ps to 50 ps. System complexity requires sophisticated simulation and modeling tools for design, performance prediction, and comprehension of experimental results. We provide a brief overview of ARC, present our main modeling tools, and describe important performance predictions. The laser system (Fig. 1) consists of an all-fiber front end, including chirped-fiber Bragg grating (CFBG)more » stretchers. The beam after the final fiber amplifier is split into two apertures and spatially shaped. The split beam first seeds a regenerative amplifier and is then amplified in a multi-pass Nd:glass amplifier. Next, the preamplified chirped pulse is split in time into four identical replicas and injected into one NIF Quad. At the output of the NIF beamline, each of the eight amplified pulses is compressed in an individual, folded, four-grating compressor. Compressor grating pairs have slightly different groove densities to enable compact folding geometry and eliminate adjacent beam cross-talk. Pulse duration is adjustable with a small, rack-mounted compressor in the front-end. We use non-sequential ray-tracing software, FRED for design and layout of the optical system. Currently, our FRED model includes all of the optical components from the output of the fiber front end to the target center (Fig. 2). CAD designed opto-mechanical components are imported into our FRED model to provide a complete system description. In addition to incoherent ray tracing and scattering analysis, FRED uses Gaussian beam decomposition to model coherent beam propagation. Neglecting nonlinear effects, we can obtain a nearly complete frequency domain description of the ARC beam at different stages in the system. We employ 3D Fourier based propagation codes: MIRO, Virtual Beamline (VBL), and PROP for time-domain pulse analysis. These codes simulate nonlinear effects, calculate near and far field beam profiles, and account for amplifier gain. Verification of correct system set-up is a major difficulty to using these codes. VBL and PROP predictions have been extensively benchmarked to NIF experiments, and the verified descriptions of specific NIF beamlines are used for ARC. MIRO has the added capability of treating bandwidth specific effects of CPA. A sample MIRO model of the NIF beamline is shown in Fig. 3. MIRO models are benchmarked to VBL and PROP in the narrow bandwidth mode. Developing a variety of simulation tools allows us to cross-check predictions of different models and gain confidence in their fidelity. Preliminary experiments, currently in progress, are allowing us to validate and refine our models, and help guide future experimental campaigns.« less

An assessment of multibody simulation tools for articulated spacecraft

NASA Technical Reports Server (NTRS)

Man, Guy K.; Sirlin, Samuel W.

1989-01-01

A survey of multibody simulation codes was conducted in the spring of 1988, to obtain an assessment of the state of the art in multibody simulation codes from the users of the codes. This survey covers the most often used articulated multibody simulation codes in the spacecraft and robotics community. There was no attempt to perform a complete survey of all available multibody codes in all disciplines. Furthermore, this is not an exhaustive evaluation of even robotics and spacecraft multibody simulation codes, as the survey was designed to capture feedback on issues most important to the users of simulation codes. We must keep in mind that the information received was limited and the technical background of the respondents varied greatly. Therefore, only the most often cited observations from the questionnaire are reported here. In this survey, it was found that no one code had both many users (reports) and no limitations. The first section is a report on multibody code applications. Following applications is a discussion of execution time, which is the most troublesome issue for flexible multibody codes. The representation of component flexible bodies, which affects both simulation setup time as well as execution time, is presented next. Following component data preparation, two sections address the accessibility or usability of a code, evaluated by considering its user interface design and examining the overall simulation integrated environment. A summary of user efforts at code verification is reported, before a tabular summary of the questionnaire responses. Finally, some conclusions are drawn.

Laser Altimeter for Flight Simulator

NASA Technical Reports Server (NTRS)

Webster, L. D.

1986-01-01

Height of flight-simulator probe above model of terrain measured by automatic laser triangulation system. Airplane simulated by probe that moves over model of terrain. Altitude of airplane scaled from height of probe above model. Height measured by triangulation of laser beam aimed at intersection of model surface with plumb line of probe.