WorldWideScience

Sample records for chemical control laser

  1. Phase Control of HF Chemical Lasers for Coherent Recombination

    Science.gov (United States)

    2007-11-02

    space vacuum and radiation effects on materials, lubrication and surface phenomena, photo- sensitive materials and sensors, high precision...3. PERFORMANCE INDEX .t£ J = 4 / (xTAx + uTBu)dt "’to 4. RICCATI EQUATION S = -SF - FTS - A + SGB -iGTs 5. OPTIMAL CONTROL GAINS C

  2. CONTROL OF LASER RADIATION PARAMETERS: Enhancement of the efficiency and control of emission parameters of an unstable-resonator chemical oxygen—iodine laser

    Science.gov (United States)

    Boreisho, A. S.; Lobachev, V. V.; Savin, A. V.; Strakhov, S. Yu; Trilis, A. V.

    2007-07-01

    The outlook is considered for the development of a high-power supersonic flowing chemical oxygen—iodine laser operating as an amplifier and controlled by radiation from a master oscillator by using an unstable resonator with a hole-coupled mirror. The influence of the seed radiation intensity, the coupling-hole diameter, the active-medium length, and the magnification factor on the parameters of laser radiation is analysed. It is shown that the use of such resonators is most advisable in medium-power oxygen—iodine lasers for which classical unstable resonators are inefficient because of their low magnification factors. The use of unstable resonators with a hole-coupled mirror and injection provides the control of radiation parameters and a considerable increase in the output power and brightness of laser radiation.

  3. Data acquisition and control system with a programmable logic controller (PLC) for a pulsed chemical oxygen-iodine laser

    Science.gov (United States)

    Yu, Haijun; Li, Guofu; Duo, Liping; Jin, Yuqi; Wang, Jian; Sang, Fengting; Kang, Yuanfu; Li, Liucheng; Wang, Yuanhu; Tang, Shukai; Yu, Hongliang

    2015-02-01

    A user-friendly data acquisition and control system (DACS) for a pulsed chemical oxygen -iodine laser (PCOIL) has been developed. It is implemented by an industrial control computer,a PLC, and a distributed input/output (I/O) module, as well as the valve and transmitter. The system is capable of handling 200 analogue/digital channels for performing various operations such as on-line acquisition, display, safety measures and control of various valves. These operations are controlled either by control switches configured on a PC while not running or by a pre-determined sequence or timings during the run. The system is capable of real-time acquisition and on-line estimation of important diagnostic parameters for optimization of a PCOIL. The DACS system has been programmed using software programmable logic controller (PLC). Using this DACS, more than 200 runs were given performed successfully.

  4. Low-intensity laser coupled with photosensitizer to reduce bacteria in root canals compared to chemical control; Laser em baixa intensidade associado a fotosensibilizador para reducao bacteriana intracanal comparado ao controle quimico

    Energy Technology Data Exchange (ETDEWEB)

    Garcez Segundo, Aguinaldo Silva

    2002-07-01

    The photodynamic therapy is a process in which a dye is associate with an appropriate wavelength of light and this dye goes to an excited state. The excited reacts with oxygen to form the highly reactive compound singlet oxygen, and this compound can kill bacteria and tumor cells. The purpose of this study was to evaluate the bactericidal reduction in root canal contaminated with E. Faecalis. Thirty teeth with their root canals prepared were contaminated with E. faecalis. The teeth have received the chemical substance sodium hypochlorite for 30 minutes; ten teeth have received the azulene dye paste for 5 minutes and have been irradiated with a diode laser, output power 10 mW and {lambda}= 685 nm for 3 minutes. Ten teeth have not received treatment (control group). The bacterial reduction was significantly higher for laser group when compared to chemical and control groups. These results indicate photodynamic therapy as an effective method to kill bacteria. (author)

  5. Arduino based laser control

    OpenAIRE

    Bernal Muñoz, Ferran

    2015-01-01

    ARDUINO is a vey usefull platform for prototypes. In this project ARDUINO will be used for controling a Semiconductor Tuneable Laser. [ANGLÈS] Diode laser for communications control based on an Arduino board. Temperature control implementation. Software and hardware protection for the laser implementation. [CASTELLÀ] Control de un láser de comunicaciones ópticas desde el ordenador utilizando una placa Arduino. Implementación de un control de temperatura y protección software y hardware ...

  6. Hydroxyl Radical Chemical Laser

    Science.gov (United States)

    1977-11-01

    Stone (I) 1 Atlantic Research Corporation, Alexandria, VA (Robert Naismith ) I Battelle Columbus laboratories, Columbus, OH (Fred Tietzel) 1...Corporation, Santa Monica, CA (Dr. Claude R. Culp) 1 Thiokol Chemical Corporation, Wasatch Division, Brigham City, UT ( James E. Hansen) 4 United

  7. Controlling Chaotic Lasers

    Science.gov (United States)

    Gills, Zelda; Roy, Rajarshi

    1995-01-01

    Irregular fluctuations in intensity have long plagued the operation of a wide variety of solid-state lasers. We are exploring the possibility of exploiting rather than avoiding a laser's chaotic output. As an important step in that direction, we have applied a novel control technique to stabilize a solid state laser. By making small periodic changes in only one input parameter of the laser, we are able to stabilize complex periodic waveforms and steady state behavior in the laser output. We demonstrate the application of this approach in a diode pumped Nd:/YAG laser system.

  8. Control of chemical chaos

    Institute of Scientific and Technical Information of China (English)

    李卫东; 钱积新

    2002-01-01

    Lyapunov exponents can act as the judgment rule whether the systems is chaotic or not.We propose an approach to control chaotic systems by varying the Lyapunov exponents of the system. At last we use this method to control a chemical system. Both the theoretical analysis and the simulation results prove that this method can quickly and effectively stabilize the chaotic systems to the desire points.

  9. Injection-controlled laser resonator

    Science.gov (United States)

    Chang, J.J.

    1995-07-18

    A new injection-controlled laser resonator incorporates self-filtering and self-imaging characteristics with an efficient injection scheme. A low-divergence laser signal is injected into the resonator, which enables the injection signal to be converted to the desired resonator modes before the main laser pulse starts. This injection technique and resonator design enable the laser cavity to improve the quality of the injection signal through self-filtering before the main laser pulse starts. The self-imaging property of the present resonator reduces the cavity induced diffraction effects and, in turn, improves the laser beam quality. 5 figs.

  10. Pressure Controlled Chemical Gardens.

    Science.gov (United States)

    Bentley, Megan R; Batista, Bruno C; Steinbock, Oliver

    2016-06-30

    The dissolution of metal salts in silicate solution can result in the growth of hollow precipitate tubes. These "chemical gardens" are a model of self-organization far from the equilibrium and create permanent macroscopic structures. The reproducibility of the growth process is greatly improved if the solid salt seed is replaced by a salt solution that is steadily injected by a pump; however, this modification of the original experiment eliminates the membrane-based osmotic pump at the base of conventional chemical gardens and does not allow for analyses in terms of the involved pressure. Here we describe a new experimental method that delivers the salt solution according to a controlled hydrostatic pressure. In one form of the experiment, this pressure slowly decreases as zinc sulfate solution flows into the silicate-containing reaction vessel, whereas a second version holds the respective solution heights constant. In addition to three known growth regimes (jetting, popping, budding), we observe single tubes that fill the vessel in a horizontally undulating but vertically layered fashion (crowding). The resulting, dried product has a cylindrical shape, very low density, and one continuous connection from top to bottom. We also present phase diagrams of these growth modes and show that the flow characteristics of our experiments follow a reaction-independent Hagen-Poiseuille equation.

  11. Variable emissivity laser thermal control system

    Science.gov (United States)

    Milner, Joseph R.

    1994-01-01

    A laser thermal control system for a metal vapor laser maintains the wall mperature of the laser at a desired level by changing the effective emissivity of the water cooling jacket. This capability increases the overall efficiency of the laser.

  12. Controlling chemical reactions of a single particle

    CERN Document Server

    Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael

    2012-01-01

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achi...

  13. Laser Velocimetry of Chemical Vapor Deposition Flows

    Science.gov (United States)

    1993-01-01

    Laser velocimetry (LV) is being used to measure the gas flows in chemical vapor deposition (CVD) reactors. These gas flow measurements can be used to improve industrial processes in semiconductor and optical layer deposition and to validate numerical models. Visible in the center of the picture is the graphite susceptor glowing orange-hot at 600 degrees C. It is inductively heated via the copper cool surrounding the glass reactor.

  14. Laser welding closed-loop power control

    DEFF Research Database (Denmark)

    Bagger, Claus; Olsen, Flemming Ove

    2003-01-01

    A closed-loop control system is developed to maintain an even seam width on the root side of a laser weld by continually controlling the output laser power of a 1500 W CO2 laser.......A closed-loop control system is developed to maintain an even seam width on the root side of a laser weld by continually controlling the output laser power of a 1500 W CO2 laser....

  15. Laser dye toxicity, hazards, and recommended controls

    Energy Technology Data Exchange (ETDEWEB)

    Mosovsky, J.A.

    1983-05-06

    Laser dyes are complex fluorescent organic compounds which, when in solution with organic solvents, form a lasing medium. The wavelength of a dye laser's output beam can vary with different dyes, concentrations, and solvents, giving it a tunable feature capable of emitting ultraviolet, visible, or infrared radiation. Toxicity information on the approximately 100 commercially available laser dyes is very scarce. Limited animal experimentation has been performed with only a few dyes. This paper summarizes what is known about laser dye toxicity, and offers recommendations for controlling dye hazards. The laser dyes investigated have been categorized according to their central chemical structures. These include the xanthenes (rhodamines and fluoresceins), polymethines (cyanines and carbocyanines), coumarins, and stilbenes. A few other miscellaneous dyes that do not fall into one of these categories have also been investigated. Prepared laser dye solutions usually contain very small quantities of dye--typical dye concentrations are 10/sup -2/ to 10/sup -5/ molar. For this reason, the solvent in which the dye is dissolved plays an important role when defining potential hazards. Practically all the solvents used are flammable and toxic by inhalation and skin absorption, and therefore must be controlled properly.

  16. Chemical Control of Plant Growth.

    Science.gov (United States)

    Agricultural Research Center (USDA), Beltsville, MD.

    Seven experiments are presented in this Science Study Aid to help students investigate the control of plant growth with chemicals. Plant growth regulators, weed control, and chemical pruning are the topics studied in the experiments which are based on investigations that have been and are being conducted at the U. S. Agricultural Research Center,…

  17. Remote Chemical Sensing Using Quantum Cascade Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Harper, Warren W.; Schultz, John F.

    2003-01-30

    Spectroscopic chemical sensing research at Pacific Northwest National Laboratory (PNNL) is focused on developing advanced sensors for detecting the production of nuclear, chemical, or biological weapons; use of chemical weapons; or the presence of explosives, firearms, narcotics, or other contraband of significance to homeland security in airports, cargo terminals, public buildings, or other sensitive locations. For most of these missions, the signature chemicals are expected to occur in very low concentrations, and in mixture with ambient air or airborne waste streams that contain large numbers of other species that may interfere with spectroscopic detection, or be mistaken for signatures of illicit activity. PNNL’s emphasis is therefore on developing remote and sampling sensors with extreme sensitivity, and resistance to interferents, or selectivity. PNNL’s research activities include: 1. Identification of signature chemicals and quantification of their spectral characteristics, 2. Identification and development of laser and other technologies that enable breakthroughs in sensitivity and selectivity, 3. Development of promising sensing techniques through experimentation and modeling the physical phenomenology and practical engineering limitations affecting their performance, and 4. Development and testing of data collection methods and analysis algorithms. Close coordination of all aspects of the research is important to ensure that all parts are focused on productive avenues of investigation. Close coordination of experimental development and numerical modeling is particularly important because the theoretical component provides understanding and predictive capability, while the experiments validate calculations and ensure that all phenomena and engineering limitations are considered.

  18. Optimal control for chemical engineers

    CERN Document Server

    Upreti, Simant Ranjan

    2013-01-01

    Optimal Control for Chemical Engineers gives a detailed treatment of optimal control theory that enables readers to formulate and solve optimal control problems. With a strong emphasis on problem solving, the book provides all the necessary mathematical analyses and derivations of important results, including multiplier theorems and Pontryagin's principle.The text begins by introducing various examples of optimal control, such as batch distillation and chemotherapy, and the basic concepts of optimal control, including functionals and differentials. It then analyzes the notion of optimality, de

  19. Photonic crystal laser sources for chemical detection

    OpenAIRE

    Lončar, Marko; Scherer, Axel; Qiu, Yueming

    2003-01-01

    We have realized photonic crystal lasers that permit the introduction of analyte within the peak of the optical field of the lasing mode. We have explored the design compromises for developing such sensitive low-threshold spectroscopy sources, and demonstrate the operation of photonic crystal lasers in different ambient organic solutions. We show that nanocavity lasers can be used to perform spectroscopic tests on femtoliter volumes of analyte, and propose to use these lasers for high-resolut...

  20. Polarisation control of DFB fibre lasers

    DEFF Research Database (Denmark)

    Varming, Poul; Philipsen, Jacob Lundgreen; Berendt, Martin Ole;

    1998-01-01

    The polarisation properties of a distributed feedback (DFB) fibre laser are investigated. It is shown experimentally that the birefringence of the UV induced phase-shift is the dominating effect controlling the polarisation properties of the laser...

  1. Chemical-free cleaning using excimer lasers

    Science.gov (United States)

    Lizotte, Todd E.; O'Keeffe, Terence R.

    1996-04-01

    A critical requirement in many industrial processes is the cleaning of oils and grease, oxides, solvent residues, particles, thin films and other contaminants from surfaces. There is a particularly acute need in the electronics industry for cleaning semiconductor wafers and computer chips and in the metals industry for removing oxides and other contaminants. Cleaning traditionally is done by various wet chemical processes, almost all consuming large amounts of water and producing large amounts of hazardous wastes. To further complicate this, some of these cleaning agents and vast water consumption are undergoing stringent restrictions. The Radiance ProcessSM is a novel, patented Excimer Laser approach to dry surface cleaning. The process has removed particles from 80 microns to submicron sizes, paints, inks, oxides, fingerprints, hazes, parts of molecules and metallic ions in fingerprints. The process does not ablate, melt or damage the underlying surface. Micro-roughening on some Silicon and Gallium Arsenide is on the order of 1A or less. This paper will discuss the various applications with this process and the latest results from a beta wafer cleaning prototype test bed system that is being built under an EPA grant and joint partnership between Radiance Services Company, Neuman Micro Technologies, Inc. and the Microelectronics Research Laboratory.

  2. Laser micromachining of chemically altered polymers

    Energy Technology Data Exchange (ETDEWEB)

    Lippert, T.

    1998-08-01

    During the last decade laser processing of polymers has become an important field of applied and fundamental research. One of the most promising proposals, to use laser ablation as dry etching technique in photolithography, has not yet become an industrial application. Many disadvantages of laser ablation, compared to conventional photolithography, are the result of the use of standard polymers. These polymers are designed for totally different applications, but are compared to the highly specialized photoresist. A new approach to laser polymer ablation will be described; the development of polymers, specially designed for high resolution laser ablation. These polymers have photolabile groups in the polymer backbone, which decompose upon laser irradiation or standard polymers are modified for ablation at a specific irradiation wavelength. The absorption maximum can be tailored for specific laser emissino lines, e.g. 351, 308 and 248 nm lines of excimer lasers. The authors show that with this approach many problems associated with the application of laser ablation for photolithography can be solved. The mechanism of ablation for these photopolymers is photochemical, whereas for most of the standard polymers this mechanism is photothermal. The photochemical decomposition mechanism results in high resolution ablation with no thermal damage at the edges of the etched structures. In addition there are no redeposited ablation products or surface modifications of the polymer after ablation.

  3. Chemical and Laser Sciences Division annual report 1989

    Energy Technology Data Exchange (ETDEWEB)

    Haines, N. (ed.)

    1990-06-01

    The Chemical and Laser Sciences Division Annual Report includes articles describing representative research and development activities within the Division, as well as major programs to which the Division makes significant contributions.

  4. High-energy molecular lasers self-controlled volume-discharge lasers and applications

    CERN Document Server

    Apollonov, V V

    2016-01-01

    This book displays the physics and design of high-power molecular lasers. The lasers described are self-controlled volume-discharge lasers. The book explains self-sustained discharge lasers, self-initiated discharge lasers and technical approaches to laser design. Important topics discussed are laser efficiency, laser beam quality and electric field homogeneity. The book contains many new innovative applications.

  5. Comparison of Laser Chemical Processing and LaserMicroJet for structuring and cutting silicon substrates

    Science.gov (United States)

    Hopman, Sybille; Fell, Andreas; Mayer, Kuno; Mesec, Matthias; Rodofili, Andreas; Kray, Daniel

    2009-06-01

    This paper deals with the development of a new cutting method for thin silicon solar wafers with liquid-jet-guided lasers (LaserMicroJet®, LMJ, and Laser Chemical Processing, LCP). Several laser systems with different wavelengths were tested to find the optimum laser system and processing parameters in terms of efficient material removal and deep laser cutting. Water and potassium hydroxide were used as carrier liquids to enhance laser ablation. The ablation efficiency was defined as a target parameter and experimentally determined by performing single laser grooves. It is demonstrated that the ablation process of LMJ is mainly affected by silicon melting and then removing by the liquid-jet momentum for single laser grooves. Best result for deep laser grooves is achieved if evaporation dominates the ablation process. Better surface quality referred to laser-induced crystalline damage is presented for a cut wafer with LMJ in comparison to a standard multiwire slurry saw. This shows a great potential of wafering with liquid-jet-guided lasers although no optimal liquid media was used.

  6. Laser studies of chemical reaction and collision processes

    Energy Technology Data Exchange (ETDEWEB)

    Flynn, G. [Columbia Univ., New York, NY (United States)

    1993-12-01

    This work has concentrated on several interrelated projects in the area of laser photochemistry and photophysics which impinge on a variety of questions in combustion chemistry and general chemical kinetics. Infrared diode laser probes of the quenching of molecules with {open_quotes}chemically significant{close_quotes} amounts of energy in which the energy transferred to the quencher has, for the first time, been separated into its vibrational, rotational, and translational components. Probes of quantum state distributions and velocity profiles for atomic fragments produced in photodissociation reactions have been explored for iodine chloride.

  7. Microprocessor-Controlled Laser Balancing System

    Science.gov (United States)

    Demuth, R. S.

    1985-01-01

    Material removed by laser action as part tested for balance. Directed by microprocessor, laser fires appropriate amount of pulses in correct locations to remove necessary amount of material. Operator and microprocessor software interact through video screen and keypad; no programing skills or unprompted system-control decisions required. System provides complete and accurate balancing in single load-and-spinup cycle.

  8. Bibliography of Short Wavelength Chemical Laser Research

    Science.gov (United States)

    1993-05-01

    Churassy, M.L. Gaillard, J.P. Pique and F. Hartmann HYPERFINE PREDISSOCIATION IN DIATOMIC BROMINE Laser Chem., 1, 185 (1983) 157. Koffend, J.B., C.E...FLUORESCENCE DECAY DYNAMICS OF MATRIX ISOLATED IBr J. Phys. Chem., 96, 4301 (1992) 172. Macler, M., J.P. Nicolai , and M.C. Heaven ELECTRONIC SPECTROSCOPY AND... Nicolai , J.P. and M.C. Heaven PHOTOSELECTION STUDY OF THE BROMINE MOLECULE A -4 X EMISSION SYSTEM IN AN ARGON MATRIX J. Chem. Phys., 83, 6538 (1985

  9. Applications of laser in the field of chemical solubility determination

    Institute of Scientific and Technical Information of China (English)

    Mingming Chen(陈明鸣); Peisheng Ma(马沛生); Xinxing Liu(柳新星)

    2003-01-01

    A novel experiment method for chemical solubility determination was brought forward, in which opticsand chemistry principles are united and the change of laser intensity indicates the process of chemicaldissolving. The more undissolved solid exists in the mixture of solute and solvent, the less transmittedlaser intensity is detected. Only when the transmitted laser intensity in stirring state and that in staticstate comes into equalization, the dissolving process stops. Under the help of laser intensity judgement,measurements turn to be more feasible and objective, especially at high pressure. The average relativeerrors for the solubility data determined in this paper are 2.3% for those in the minor value scope and 1.7%for those in the high value scope respectively. Comparison of the experimental solubility data with theliterature ones demonstrates that the laser-aid solubility determination apparatus is stable and reliable.

  10. New Electronic-Transition Laser Systems. Part 1. Electron Pumped Systems. Part 2. Chemically Pumped Systems

    Science.gov (United States)

    1976-12-01

    laser development . There has not yet been a demonstration of gain in a visible chemical laser systems, and it appears unlikely that practical lasers of this type will be developed in the near future. Substantial progress has been made

  11. How to control chemical hazards

    CERN Multimedia

    2012-01-01

    Improving protection against chemical hazards is one of the 2012 CERN safety objectives identified by the Director General. Identifying and drawing up a complete inventory of chemicals, and assessing the associated risks are important steps in this direction.   The HSE Unit has drawn up safety rules, guidelines and forms to help you to meet this objective. We would like to draw your attention to: • safety guidelines C-0-0-1 and C-1-0-2 (now also available in French), which deal with the identification of hazardous chemicals and the assessment of chemical risk; • safety guideline C-1-0-1, which deals with the storage of hazardous chemicals. All safety documents can be consulted at: cern.ch/regles-securite The HSE Unit will be happy to answer any questions you may have. Write to us at: safety-general@cern.ch The HSE Unit

  12. Microscale vortex laser with controlled topological charge

    Science.gov (United States)

    Wang, Xing-Yuan; Chen, Hua-Zhou; Li, Ying; Li, Bo; Ma, Ren-Min

    2016-12-01

    A microscale vortex laser is a new type of coherent light source with small footprint that can directly generate vector vortex beams. However, a microscale laser with controlled topological charge, which is crucial for virtually any of its application, is still unrevealed. Here we present a microscale vortex laser with controlled topological charge. The vortex laser eigenmode was synthesized in a metamaterial engineered non-Hermitian micro-ring cavity system at exceptional point. We also show that the vortex laser cavity can operate at exceptional point stably to lase under optical pumping. The microscale vortex laser with controlled topological charge can serve as a unique and general building block for next-generation photonic integrated circuits and coherent vortex beam sources. The method we used here can be employed to generate lasing eigenmode with other complex functionalities. Project supported by the “Youth 1000 Talent Plan” Fund, Ministry of Education of China (Grant No. 201421) and the National Natural Science Foundation of China (Grant Nos. 11574012 and 61521004).

  13. Chemical Changes Associated with Increased Acid Resistance of Er:YAG Laser Irradiated Enamel

    Directory of Open Access Journals (Sweden)

    Jennifer Manuela Díaz-Monroy

    2014-01-01

    Full Text Available Background. An increase in the acid resistance of dental enamel, as well as morphological and structural changes produced by Er:YAG laser irradiation, has been reported. Purpose. To evaluate the chemical changes associated with acid resistance of enamel treated with Er:YAG laser. Methods. Forty-eight enamel samples were divided into 4 groups (n=12. Group I (control; Groups II, III, and IV were irradiated with Er:YAG at 100 mJ (12.7 J/cm2, 200 mJ (25.5 J/cm2, and 300 mJ (38.2 J/cm2, respectively. Results. There were significant differences in composition of irradiated groups (with the exception of chlorine and in the amount of calcium released. Conclusions. Chemical changes associated with an increase in acid resistance of enamel treated with Er:YAG laser showed a clear postirradiation pattern characterized by a decrease in C at.% and an increase in O, P, and Ca at.% and no changes in Cl at.%. An increased Ca/P ratio after Er:YAG laser irradiation was associated with the use of higher laser energy densities. Chemical changes produced by acid dissolution showed a similar trend among experimental groups. Stable or increased Ca/P ratio after acid dissolution was observed in the irradiated groups, with reduction of Ca released into the acid solution.

  14. Laser-controllable coatings for corrosion protection.

    Science.gov (United States)

    Skorb, Ekaterina V; Skirtach, Andre G; Sviridov, Dmitry V; Shchukin, Dmitry G; Möhwald, Helmuth

    2009-07-28

    We introduce a novel and versatile approach to the corrosion protection by use of "smart" laser-controllable coating. The main advantage of the proposed technique is that one could terminate the corrosion process by very intensive healing after an appearance of corrosion centers using local laser irradiation. It is also shown that by applying a polyelectrolyte shell with noble metal particles over the mesoporous titania and silica via layer-by-layer assembly it is possible to fabricate micro- and nanoscaled reservoirs, which, being incorporated into the zirconia-organosilica matrix, are responsible for the ability of laser-driven release of the loaded materials (e.g., corrosion inhibitor). Furthermore, the resultant films are highly adhesive and could be easily deposited onto different metallic substrates. Laser-mediated remote release of incorporated corrosion inhibitor (benzotriazole) from engineered mesoporous containers with silver nanoparticles in the container shell is observed in real time on single and multicontainer levels.

  15. Controllability of intense-laser ion acceleration

    Institute of Scientific and Technical Information of China (English)

    Shigeo; Kawata; Toshihiro; Nagashima; Masahiro; Takano; Takeshi; Izumiyama; Daiki; Kamiyama; Daisuke; Barada; Qing; Kong; Yan; Jun; Gu; Ping; Xiao; Wang; Yan; Yun; Ma; Wei; Ming; Wang; Wu; Zhang; Jiang; Xie; Huiran; Zhang; Dongbo; Dai

    2014-01-01

    An ion beam has the unique feature of being able to deposit its main energy inside a human body to kill cancer cells or inside material. However, conventional ion accelerators tend to be huge in size and cost. In this paper, a future intenselaser ion accelerator is discussed to make the laser-based ion accelerator compact and controllable. The issues in the laser ion accelerator include the energy efficiency from the laser to the ions, the ion beam collimation, the ion energy spectrum control, the ion beam bunching, and the ion particle energy control. In the study, each component is designed to control the ion beam quality by particle simulations. The energy efficiency from the laser to ions is improved by using a solid target with a fine sub-wavelength structure or a near-critical-density gas plasma. The ion beam collimation is performed by holes behind the solid target or a multi-layered solid target. The control of the ion energy spectrum and the ion particle energy, and the ion beam bunching are successfully realized by a multi-stage laser–target interaction.

  16. Chemical control of flowering time

    DEFF Research Database (Denmark)

    Ionescu, Irina Alexandra; Møller, Birger Lindberg; Sánchez Pérez, Raquel

    2017-01-01

    the transition to flowering as well as flower opening. Increased emphasis on research within this area has the potential to counteract the negative effects of global warming on flowering time, especially in perennial crop plants. Perennial crops have a requirement for winter chill, but winters become...... increasingly warm in temperate regions. This has dramatic effects on crop yield. Different strategies are therefore being developed to engineer flowering time to match local growing conditions. The majority of these efforts are within plant breeding, which benefits from a substantial amount of knowledge...... on the genetic aspects of flowering time regulation in annuals, but less so in perennials. An alternative to plant breeding approaches is to engineer flowering time chemically via the external application of flower-inducing compounds. This review discusses a variety of exogenously applied compounds used in fruit...

  17. 20-Kw nitrogen diluent chemical oxygen-iodine laser

    Science.gov (United States)

    Yang, Tientsai T.; Bhowmik, Anup; Burde, David H.; Clark, Roy; Carroll, S.; Dickerson, Robert A.; Eblen, J.; Gylys, Vytas T.; Hsia, Y. C.; Humphreys, Richard H., Jr.; Moon, L. F.; Hurlock, Steve C.; Tomassian, A.

    2002-09-01

    A new Chemical Oxygen-Iodine Laser (COIL) has been developed and demonstrated at chlorine flow rates up to 1 gmol/s. The laser employs a cross flow jet oxygen generator operating with no diluent. The generator product flow enters the laser cavity at Mach 1 and is accelerated by mixing with 5 gmol/s, Mach 5 nitrogen diluent in an ejector nozzle array. The nitrogen also serves as the carrier for iodine. Vortex mixing is achieved through the use of mixing tabs at the nitrogen nozzle exit. Mixing approach design and analysis, including CFD analysis, led to the preferred nozzle configuration. The selected mixing enhancement design was tested in cold flow and the results are in good agreement with the CFD predictions. Good mixing was achieved within the desired cavity flow length of 20 cm and pressure recovery about 90 Torr was measured at the cavity exit. Finally, the design was incorporated into the laser and power extraction as high as 20 kw was measured at the best operating condition of 0.9 gmol/s. Stable resonator mode footprints showed desieable intensity profiles, which none of the sugar scoop profiles characteristic of the conventional COIL designs.

  18. Control of photodetachment spectra through laser dressing

    Science.gov (United States)

    Morrison, Nathan; Greene, Chris

    2013-05-01

    Photodetachment and photoionization spectra often display rich resonance structures. The properties of these spectra can be modified through dressing with intense laser fields, providing control over photon absorption and the emitted electron. We present a Floquet R-matrix method for calculating photodetachment cross sections in the presence of a dressing laser. The full wave functions in the Floquet formalism for bound and escaping electrons are found by solving the Schrödinger equation near the atomic core and applying analytic boundary conditions outside of the interaction region. These calculations are used to investigate the modification of existing resonances, such as modifying the shape, or q parameter, of Feshbach resonances. We also investigate the creation of new resonances in cases where high-lying bound states become autoionizing through the absorption of dressing laser photons. This work was supported by the DOE.

  19. Temperature control during laser vessel welding.

    Science.gov (United States)

    Springer, T A; Welch, A J

    1993-02-01

    A technique is described for the computer control of temperature during laser vessel welding. The technique is based on the use of thermal feedback from a calibrated IR sensor. The utilization of thermalfeedback makes it possible for welding to be performed at a quasiconstant temperature. An experimentalsystem based on this concept has been developed and evaluated in mock anastomoses with vasculartissue. A computer simulation of laser vessel welding with a one-dimensional heat conduction model hasbeen performed. Model parameters have been adjusted so that the relative effect of laser penetrationdepth and tissue dehydration as well as the role of thermal feedback in limiting the peak surfacetemperature can be studied. The results of the mock anastomoses are discussed in light of the computer model.

  20. The research of laser marking control technology

    Science.gov (United States)

    Zhang, Qiue; Zhang, Rong

    2009-08-01

    In the area of Laser marking, the general control method is insert control card to computer's mother board, it can not support hot swap, it is difficult to assemble or it. Moreover, the one marking system must to equip one computer. In the system marking, the computer can not to do the other things except to transmit marking digital information. Otherwise it can affect marking precision. Based on traditional control methods existed some problems, introduced marking graphic editing and digital processing by the computer finish, high-speed digital signal processor (DSP) control marking the whole process. The laser marking controller is mainly contain DSP2812, digital memorizer, DAC (digital analog converting) transform unit circuit, USB interface control circuit, man-machine interface circuit, and other logic control circuit. Download the marking information which is processed by computer to U disk, DSP read the information by USB interface on time, then processing it, adopt the DSP inter timer control the marking time sequence, output the scanner control signal by D/A parts. Apply the technology can realize marking offline, thereby reduce the product cost, increase the product efficiency. The system have good effect in actual unit markings, the marking speed is more quickly than PCI control card to 20 percent. It has application value in practicality.

  1. Study of silica coatings degradation under laser irradiation and in controlled environment; Etude de la degradation de couches minces de silice sous flux laser et en environnement controle

    Energy Technology Data Exchange (ETDEWEB)

    Becker, S

    2006-11-15

    Performances of optical components submitted to high laser intensities are usually determined by their laser-induced damage threshold. This value represents the highest density of energy (fluence) sustainable by the component before its damage. When submitted to laser fluences far below this threshold, optical performances may also decrease with time. The degradation processes depend on laser characteristics, optical materials, and environment around the component. Silica being the most used material in optics, the aim of this study was to describe and analyse the physical-chemical mechanisms responsible for laser-induced degradation of silica coatings in controlled environment. Experimental results show that degradation is due to the growth of a carbon deposit in the irradiated zone. From these results, a phenomenological model has been proposed and validated with numerical simulations. Then, several technological solutions have been tested in order to reduce the laser-induced contamination of silica coatings. (author)

  2. Space-Based Chemical Lasers in Strategic Defense

    Science.gov (United States)

    2007-11-02

    using <fJ*™’™ „, „,,„,,; rrÄr^ÄSXnceuea. MlRACL Chemical laser at White planned for 1995. ssssSS Sands New Mexico ^f Tit:*n s«ron»1 «>ta<J*’f...AsswnHY P«o Su<«y CS2 Secwios CaoaMitv LPE 10,412 OPE 12.323 S/C with Test Objects 12,382 Subtotal 35,117 Titan IVA Margin !32.7°.o

  3. Bifurcation and Chaos Control for Nonlinear Laser Systems

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In recent years, complexity science, including various bifurcations ,chaos and turbulence, has become a great challenge in various interdisciplinary fields. It promises to have a major impact on many aspects of nature science and engineering, even social and economic science. Candidates of complex system include coupled laser systems, accelerator-driven clean nuclear power system, neural networks, cellular automata, living organism, human brain, chemical reactions and economic systems. This new and challenging research and development area has in effect become a scientific inter-discipline itself, involving systems and control engineers, theoretical and experimental

  4. Rail profile control using laser triangulation scanners

    Science.gov (United States)

    Boronahin, Ð. ńlexandr M.; Larionov, Daniil Yu.; Podgornaya, Liudmila N.; Shalymov, Roman V.; Filatov, Yuri V.; Bokhman, Evgueny D.

    2016-11-01

    Rail track geometric parameters measurement requires knowledge of left and right rail head location in each section. First of all displacement in transverse plane of rail head point located at a distance of 14 mm below the running surface, must be controlled [1]. It is carried out by detecting of each rail profile using triangulation laser scanners. Optical image recognition is carried out successfully in the laboratory, approaches used for this purpose are widely known. However, laser scanners operation has several features on railways leading to necessity of traditional approaches adaptation for solving these particular problems. The most significant problem is images noisiness due to the solar flashes and the effect of "Moon path" on the smooth rail surface. Using of optical filters gives inadequate result, because scanner laser diodes radiation frequency varies with temperature changes that forbid the use of narrow-band filters. Consideration of these features requires additional constructive and algorithmic solutions, including involvement of information from other sensors of the system. The specific usage of optical scanners for rail profiles control is the subject of the paper.

  5. Safety in the Chemical Laboratory: Flood Control.

    Science.gov (United States)

    Pollard, Bruce D.

    1983-01-01

    Describes events leading to a flood in the Wehr Chemistry Laboratory at Marquette University, discussing steps taken to minimize damage upon discovery. Analyzes the problem of flooding in the chemical laboratory and outlines seven steps of flood control: prevention; minimization; early detection; stopping the flood; evaluation; clean-up; and…

  6. Chaos: Understanding and Controlling Laser Instability

    Science.gov (United States)

    Blass, William E.

    1997-01-01

    In order to characterize the behavior of tunable diode lasers (TDL), the first step in the project involved the redesign of the TDL system here at the University of Tennessee Molecular Systems Laboratory (UTMSL). Having made these changes it was next necessary to optimize the new optical system. This involved the fine adjustments to the optical components, particularly in the monochromator, to minimize the aberrations of coma and astigmatism and to assure that the energy from the beam is focused properly on the detector element. The next step involved the taking of preliminary data. We were then ready for the analysis of the preliminary data. This required the development of computer programs that use mathematical techniques to look for signatures of chaos. Commercial programs were also employed. We discovered some indication of high dimensional chaos, but were hampered by the low sample rate of 200 KSPS (kilosamples/sec) and even more by our sample size of 1024 (1K) data points. These limitations were expected and we added a high speed data acquisition board. We incorporated into the system a computer with a 40 MSPS (million samples/sec) data acquisition board. This board can also capture 64K of data points so that were then able to perform the more accurate tests for chaos. The results were dramatic and compelling, we had demonstrated that the lead salt diode laser had a chaotic frequency output. Having identified the chaotic character in our TDL data, we proceeded to stage two as outlined in our original proposal. This required the use of an Occasional Proportional Feedback (OPF) controller to facilitate the control and stabilization of the TDL system output. The controller was designed and fabricated at GSFC and debugged in our laboratories. After some trial and error efforts, we achieved chaos control of the frequency emissions of the laser. The two publications appended to this introduction detail the entire project and its results.

  7. Controlling Second Harmonic Efficiency of Laser Beam Interactions

    Science.gov (United States)

    Barnes, Norman P. (Inventor); Walsh, Brian M. (Inventor); Reichle, Donald J. (Inventor)

    2011-01-01

    A method is provided for controlling second harmonic efficiency of laser beam interactions. A laser system generates two laser beams (e.g., a laser beam with two polarizations) for incidence on a nonlinear crystal having a preferred direction of propagation. Prior to incidence on the crystal, the beams are optically processed based on the crystal's beam separation characteristics to thereby control a position in the crystal along the preferred direction of propagation at which the beams interact.

  8. Quantum cascade laser: Applications in chemical detection and environmental monitoring

    Directory of Open Access Journals (Sweden)

    Radovanović Jelena

    2009-01-01

    Full Text Available In this paper we consider the structural parameter optimization of the active region of a GaAs-based quantum cascade laser in order to maximize the optical gain of the laser at the characteristic wavelengths, which are best suited for detection of pollutant gasses, such as SO2, HNO3, CH4, and NH3, in the ambient air by means of direct absorption. The procedure relies on applying elaborate tools for global optimization, such as the genetic algorithm. One of the important goals is to extend the applicability of a single active region design to the detection of several compounds absorbing at close wave-lengths, and this is achieved by introducing a strong external magnetic field perpendicularly to the epitaxial layers. The field causes two-dimensional continuous energy subbands to split into the series of discrete Landau levels. Since the arrangement of Landau levels depends strongly on the magnitude of the magnetic field, this enables one to control the population inversion in the active region, and hence the optical gain. Furthermore, strong effects of band non-parabolicity result in subtle changes of the lasing wavelength at magnetic fields which maximize the gain, thus providing a path for fine-tuning of the output radiation properties and changing the target compound for detection. The numerical results are presented for quantum cascade laser structures designed to emit at specified wavelengths in the mid-infrared part of the spectrum.

  9. Laser and chemical surface modifications of titanium grade 2 for medical application

    Energy Technology Data Exchange (ETDEWEB)

    Kwaśniak, P. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Pura, J., E-mail: jaroslawpura@gmail.com [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Zwolińska, M.; Wieciński, P. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland); Skarżyński, H.; Olszewski, L. [Institute of Physiology and Pathology of Hearing, Warsaw (Poland); World Hearing Center, Kajetany (Poland); Marczak, J. [Military University of Technology, Institute of Optoelectronics, Warsaw (Poland); Garbacz, H.; Kurzydłowski, K.J. [Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw (Poland)

    2015-05-01

    Highlights: • DLIL technique and etching were used for functionalization of Ti grade 2 surface. • Modification was performed on semi-finished flat and curved Ti surfaces. • Modification results in periodic multimodal (micro and nano-size) Ti topography. - Abstract: The article presents combined, chemical and physical approach to titanium surface functionalization designed for biomedical applications. The topography modification has been obtained by employing the double laser beam interference technique and chemical etching. In the outcome, clean and smooth Ti surface as well as periodic striated topography with the roughness range from nano- to micrometers were created. The obtained structures were characterized in terms of shape, roughness, chemical composition, mechanical properties and microstructures. In order to achieve all information, numerous of research methods have been used: scanning electron microscopy, atomic force microscopy, optical profilometry and microhardness measurements. Demonstrated methodology can be used as an effective tool for manufacturing controlled surface structures improving the bone–implants interactions.

  10. Pilot study of laser induced breakdown spectroscopy for tissue differentiation by monitoring the plume created during laser surgery — An approach on a feedback Laser control mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Kanawade, Rajesh, E-mail: Rajesh.Kanawade@aot.uni-erlangen.de [Clinical Photonics Lab, Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 6, 91052 Erlangen (Germany); Institute of Photonics Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen (Germany); Mehari, Fanuel [Master Programme in Advanced Optical Technologies (MAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 6, 91052 Erlangen (Germany); Knipfer, Christian; Rohde, Maximilian [Department of Oral and Maxillofacial Surgery, University Hospital Erlangen, Friedrich-Alexander-Universität Erlangen-Nürnberg, Glueckstrasse 11, 91054 Erlangen (Germany); Tangermann-Gerk, Katja [Bayerisches Laserzentrum GmbH, Konrad-Zuse-Strasse 2-6, 91052 Erlangen (Germany); Schmidt, Michael [Clinical Photonics Lab, Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 6, 91052 Erlangen (Germany); Institute of Photonics Technologies, Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Str. 3, 91052 Erlangen (Germany); Bayerisches Laserzentrum GmbH, Konrad-Zuse-Strasse 2-6, 91052 Erlangen (Germany); and others

    2013-09-01

    This study focuses on tissue differentiation using ‘Laser Induced Breakdown Spectroscopy’ (LIBS) by monitoring the plasma plume created during laser surgery processes. This technique is aimed at controlling a laser surgery feedback system in real time. An Excimer laser (Ar-F 193 nm) was used for the ablation of tissue samples. Fat, muscle, nerve and skin tissue samples of bisected ex-vivo pig heads were prepared as test objects for the ablation procedure. A single fiber was used to collect emissions and deliver them to a spectrometer. The obtained LIBS spectra in the measured emissions were analyzed to determine each tissue type according to their chemical composition. The elements found in the samples and their emission spectra were in agreement with those described in literature. The collected LIBS spectra were analyzed to differentiate the tissues using statistical data analysis: Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Receiver Operating Characteristics (ROC). The obtained preliminary results suggest a successful differentiation of the target tissues with high sensitivity and specificity. The main goal of this study was to qualitatively identify tissue types during laser ablation, which will provide a real time feedback mechanism for clinical Laser surgery applications to significantly improve the accuracy and safety of laser surgery procedures. - Graphical abstract: Skin, fat, muscle and nerve tissue differentiation. - Highlights: • Methods to differentiate tissues for the application in a laser surgery feedback control system • Successful differentiation of the target tissues with high sensitivity and specificity for laser surgery application • Real time feedback mechanism for clinical Laser surgery applications • Laser surgery requirements • Biomedical applications of LIBS.

  11. Laser diagnostics of chemical vapour deposition of diamond films

    CERN Document Server

    Wills, J B

    2002-01-01

    Cavity ring down spectroscopy (CRDS) has been used to make diagnostic measurements of chemically activated CH sub 4 / H sub 2 gas mixtures during the chemical vapour deposition (CVD) of thin diamond films. Absolute absorbances, concentrations and temperatures are presented for CH sub 3 , NH and C sub 2 H sub 2 in a hot filament (HF) activated gas mixture and CH, C sub 2 and C sub 2 H sub 2 in a DC arc plasma jet activated mixture. Measurements of the radical species were made using a pulsed dye laser system to generate tuneable visible and UV wavelengths. These species have greatest concentration in the hottest, activated regions of the reactors. Spatial profiling of the number densities of CH sub 3 and NH radicals have been used as stringent tests of predictions of radical absorbance and number densities made by 3-D numerical simulations, with near quantitative agreement. O sub 2 has been shown to reside in the activated region of the Bristol DC arc jet at concentrations (approx 10 sup 1 sup 3 molecules / cm...

  12. Chemical-Free Cotton Defoliation by; Mechanical, Flame and Laser Girdling

    Directory of Open Access Journals (Sweden)

    Mathew G. Pelletier

    2017-01-01

    Full Text Available A novel new way to achieve chemical-free defoliation of cotton is discussed. The research found that by severing the phloem tissue on the main stalk, via a girdling operation, the operation stimulated the cotton plant to alter its growth into an early senescence pathway that resulted in the plant shedding its leaves and opening up all its bolls, leaving the plant in the perfect state for machine harvesting. Even with follow-up rains, zero regrowth occurred in the treated plants, unlike the untreated control plots where significant regrowth did occur. This report compares the results of greenhouse and field trials where the girdling operation was performed by hand, flame, mechanical and via a CO2 laser to achieve phloem tissue severance. Design parameters for a prototype laser girdling system are also provided. Results suggest that for deficit irrigated cotton, girdling can provide an alternative means to defoliate cotton.

  13. Chemical reactions at metallic and metal/semiconductor interfaces stimulated by pulsed laser annealing

    Science.gov (United States)

    Petit, E. J.; Caudano, R.

    1992-01-01

    Multilayer Al/Sb thin films have been evaporated on GaSb single crystals in ultra-high vacuum and pulsed-laser irradiated in-situ above the energy density threshold for surface melting. Superficial and interfacial chemical reactions have been characterized in-situ by Auger electron spectroscopy; and later, by X-ray photoelectron spectroscopy profiling, Rutherford backscattering spectrometry and scanning electron microscopy. The chemical reaction between the Al and Sb films is considered as a model reaction for laser-assisted synthesis of high-purity intermetallic compounds. The observation of a strong interfacial reaction between the melted film and the substrate is also a subject of great concern for optical data recording and laser alloying of ohmic contacts on semiconductors. We show that a suitable choice of the substrate and adding a low surface tension element into the metallic film can improve its stability during melting, and prevent inhomogeneous reaction and formation of holes, cracks and particles. Finally, other solutions are suggested to improve the control of these reactions.

  14. Advanced Laser Chemical Processing For Microelectronics and Integrated Optics

    Science.gov (United States)

    1992-08-15

    Barbara, CA (June 25-27, 1990). 15. R.M. Osgood, Jr., " Laser - Fabrication for Integrated Electronics and Optics," OITDA Conference, Tokyo, Japan, (July 5...Society Meeting, Boston, MA, November 26 - December 3, 1990. 20. R.M. Osgood, Jr., "Advances in Laser Fabrication for Solid-State Electronics and...Thin, Excimer Laser-Deposited Cd Interlayers," J. Elec. Mat. 12, 1239 (July, 1990). 14. R.M. Osgood, Jr., " Laser - Fabrication for Solid State

  15. Chemical optimization algorithm for fuzzy controller design

    CERN Document Server

    Astudillo, Leslie; Castillo, Oscar

    2014-01-01

    In this book, a novel optimization method inspired by a paradigm from nature is introduced. The chemical reactions are used as a paradigm to propose an optimization method that simulates these natural processes. The proposed algorithm is described in detail and then a set of typical complex benchmark functions is used to evaluate the performance of the algorithm. Simulation results show that the proposed optimization algorithm can outperform other methods in a set of benchmark functions. This chemical reaction optimization paradigm is also applied to solve the tracking problem for the dynamic model of a unicycle mobile robot by integrating a kinematic and a torque controller based on fuzzy logic theory. Computer simulations are presented confirming that this optimization paradigm is able to outperform other optimization techniques applied to this particular robot application

  16. Pilot study of laser induced breakdown spectroscopy for tissue differentiation by monitoring the plume created during laser surgery — An approach on a feedback Laser control mechanism

    Science.gov (United States)

    Kanawade, Rajesh; Mehari, Fanuel; Knipfer, Christian; Rohde, Maximilian; Tangermann-Gerk, Katja; Schmidt, Michael; Stelzle, Florian

    2013-09-01

    This study focuses on tissue differentiation using 'Laser Induced Breakdown Spectroscopy' (LIBS) by monitoring the plasma plume created during laser surgery processes. This technique is aimed at controlling a laser surgery feedback system in real time. An Excimer laser (Ar-F 193 nm) was used for the ablation of tissue samples. Fat, muscle, nerve and skin tissue samples of bisected ex-vivo pig heads were prepared as test objects for the ablation procedure. A single fiber was used to collect emissions and deliver them to a spectrometer. The obtained LIBS spectra in the measured emissions were analyzed to determine each tissue type according to their chemical composition. The elements found in the samples and their emission spectra were in agreement with those described in literature. The collected LIBS spectra were analyzed to differentiate the tissues using statistical data analysis: Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA) and Receiver Operating Characteristics (ROC). The obtained preliminary results suggest a successful differentiation of the target tissues with high sensitivity and specificity. The main goal of this study was to qualitatively identify tissue types during laser ablation, which will provide a real time feedback mechanism for clinical Laser surgery applications to significantly improve the accuracy and safety of laser surgery procedures.

  17. Laser controlled atom source for optical clocks

    Science.gov (United States)

    Kock, Ole; He, Wei; Świerad, Dariusz; Smith, Lyndsie; Hughes, Joshua; Bongs, Kai; Singh, Yeshpal

    2016-11-01

    Precision timekeeping has been a driving force in innovation, from defining agricultural seasons to atomic clocks enabling satellite navigation, broadband communication and high-speed trading. We are on the verge of a revolution in atomic timekeeping, where optical clocks promise an over thousand-fold improvement in stability and accuracy. However, complex setups and sensitivity to thermal radiation pose limitations to progress. Here we report on an atom source for a strontium optical lattice clock which circumvents these limitations. We demonstrate fast (sub 100 ms), cold and controlled emission of strontium atomic vapours from bulk strontium oxide irradiated by a simple low power diode laser. Our results demonstrate that millions of strontium atoms from the vapour can be captured in a magneto-optical trap (MOT). Our method enables over an order of magnitude reduction in scale of the apparatus. Future applications range from satellite clocks testing general relativity to portable clocks for inertial navigation systems and relativistic geodesy.

  18. LHC Survey Laser Tracker Controls Renovation

    CERN Document Server

    Charrondière, C

    2011-01-01

    The LHC survey laser tracker control system is based on an industrial software package (Axyz) from Leica Geosystems™ that has an interface to Visual Basic™, which we used to automate the geometric measurements for the LHC magnets. With the new version of the Leica software, this Visual Basic™ interface is no longerb available and we had to redesign the interface software to adapt to a PC-DMIS server that replaced the Axyz software. As this package is no longer supported, we have taken the decision to recode the automation application in LabVIEW. This presentation describes the existing equipment, interface and application showing the reasons for our decisions to move to PC-DMIS and LabVIEW. A comparison between the new and legacy system is made

  19. Development of the power control system for semiconductor lasers

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kwang Suk; Kim, Cheol Jung

    1997-12-01

    For the first year plan of this program, we developed the power control system for semiconductor lasers. We applied the high-current switching mode techniques to fabricating a power control system. Then, we investigated the direct side pumping techniques with GaA1As diode laser bars to laser crystal without pumping optics. We obtained 0.5W average output power from this DPSSL. (author). 54 refs., 3 tabs., 18 figs.

  20. Spectral control of diode lasers using external waveguide circuits

    NARCIS (Netherlands)

    Oldenbeuving, R.M.

    2013-01-01

    We investigated spectral control of diode lasers using external waveguide circuits. The purpose of this work is to investigate such external control for providing a new class of diode lasers with technologically interesting properties, such as a narrow spectral bandwidth and spectrally tunable outpu

  1. Parallel femtosecond laser processing with vector-wave control

    Directory of Open Access Journals (Sweden)

    Hayasaki Yoshio

    2013-11-01

    Full Text Available Parallel femtosecond laser processing with a computer-generated hologram displayed on a spatial light modulator, has the advantages of high throughput and high energy-use efficiency. for further increase of the processing efficiency, we demonstrated parallel femtosecond laser processing with vector-wave control that is based on polarization control using a pair of spatial light modulators.

  2. Broadband laser polarization control with aligned carbon nanotubes

    CERN Document Server

    Yang, He; Lia, Diao; Chen, Ya; Mattila, Marco; Tian, Ying; Yong, Zhenzhong; Yang, Changxi; Tittonen, Ilkka; Ren, Zhaoyu; Bai, Jingtao; Li, Qingwen; Kauppinen, Esko I; Lipsanen, Harri; Sun, Zhipei

    2015-01-01

    We introduce a simple approach to fabricate aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic property is confirmed with optical and scanning electron microscopy, and with polarized Raman and absorption spectroscopy. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 um) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as ...

  3. Tunable diode laser control by a stepping Michelson interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Valentin, A.; Nicolas, C.; Henry, L.; Mantz, A.W.

    1987-01-01

    A tunable diode laser beam is sent through a Michelson interferometer and is locked to a fringe of the diode laser interferometer pattern by controlling the diode laser polarization current. The path difference change of the Michelson interferometer is controlled step by step by a stabilized He--Ne red laser. When the interferometer path differences increases or decreases, the polarization current of the diode is forced to change in order to preserve the interference order of the diode beam. At every step the diode frequency is accurately fixed and its phase noise significantly reduced.

  4. [Effects of helium-neon laser on physico-chemical properties of the bile].

    Science.gov (United States)

    Mansurov, Kh Kh; Dzhuraev, Kh Sh; Barakaev, S B; Kharina, T P; Pulatov, L I

    1990-08-01

    The influence of helium-neon laser radiation on bile physico-chemical characteristics in healthy subjects and in patients with the physico-chemical stage of gallstone disease was studied in vitro. This type of laser was found to induce positive therapeutic effects, such as: correction of hydrogen ion concentrations, surface tension and viscosity decrease and prolonged bile nucleation in patients with gallstone disease.

  5. Chemical Biology Strategies for Biofilm Control.

    Science.gov (United States)

    Yang, Liang; Givskov, Michael

    2015-08-01

    Microbes live as densely populated multicellular surface-attached biofilm communities embedded in self-generated, extracellular polymeric substances (EPSs). EPSs serve as a scaffold for cross-linking biofilm cells and support development of biofilm architecture and functions. Biofilms can have a clear negative impact on humans, where biofilms are a common denominator in many chronic diseases in which they prime development of destructive inflammatory conditions and the failure of our immune system to efficiently cope with them. Our current assortment of antimicrobial agents cannot efficiently eradicate biofilms. For industrial applications, the removal of biofilms within production machinery in the paper and hygienic food packaging industry, cooling water circuits, and drinking water manufacturing systems can be critical for the safety and efficacy of those processes. Biofilm formation is a dynamic process that involves microbial cell migration, cell-to-cell signaling and interactions, EPS synthesis, and cell-EPS interactions. Recent progress of fundamental biofilm research has shed light on novel chemical biology strategies for biofilm control. In this article, chemical biology strategies targeting the bacterial intercellular and intracellular signaling pathways will be discussed.

  6. Molecular wave-packet dynamics on laser-controlled transition states

    CERN Document Server

    Fischer, Andreas; Cörlin, Philipp; Sperl, Alexander; Schönwald, Michael; Mizuno, Tomoya; Sansone, Giuseppe; Senftleben, Arne; Ullrich, Joachim; Feuerstein, Bernold; Pfeifer, Thomas; Moshammer, Robert

    2016-01-01

    Understanding and controlling the electronic as well as ro-vibrational motion and, thus, the entire chemical dynamics in molecules is the ultimate goal of ultrafast laser and imaging science. In photochemistry, laser-induced dissociation has become a valuable tool for modification and control of reaction pathways and kinetics. Here, we present a pump-probe study of the dissociation dynamics of H$_2^+$ using ultrashort extreme-ultraviolet (XUV) and near-infrared (IR) laser pulses. The reaction kinematics can be controlled by varying the pump-probe delay. We demonstrate that the nuclear motion through the transition state can be reduced to isolated pairs of initial vibrational states. The dynamics is well reproduced by intuitive semi-classical trajectories on a time-dependent potential curve. From this most fundamental scenario we gain insight in the underlying mechanisms which can be applied as design principles for molecular quantum control, particularly for ultrafast reactions involving protons.

  7. Modelling and control of laser surface treatment

    NARCIS (Netherlands)

    Römer, Gerardus Richardus Benardus Engelina

    1999-01-01

    The results of laser surface treatment may vary significantly during laser surface processing. These variations arise from the sensitivity of the process to disturbances, such as varying absorptivity and the small dimensions of the work piece. To increase the reproducibility of the process, a real-t

  8. Laser Beam Duct Pressure Controller System.

    Science.gov (United States)

    the axial flow of a conditioning gas within the laser beam duct, by matching the time rate of change of the pressure of the flowing conditioning gas...to the time rate of change of the pressure in the cavity of an operably associated laser beam turret.

  9. The Effect of Laser Treatment as a Weed Control Method

    DEFF Research Database (Denmark)

    Bak, Thomas; Mathiassen, Solvejg K.; Christensen, Svend

    2006-01-01

    A laser beam directed towards weeds can be an efficient weed control method as an alternative to herbicides. Lasers may deliver high-density energy to selected plant material, raising the temperature of the water in the plant cells and thereby stop or delay the growth. A commercial use of lasers...... for weed control, however, require a systematic investigation of the relationship between energy density and the biological effect on different weed species, growth stages, etc. This paper investigates the effect of laser treatment directed towards the apical meristems of selected weed species...... at the cotyledon stage. Experiments were carried out under controlled conditions, using pot-grown weeds. Two lasers and two spot sizes were tested and different energy doses were applied by varying the exposure time. The biological efficacy was examined on three different weed species: Stellaria media (common...

  10. LASER-INDUCED DECOMPOSITION OF METAL CARBONYLS FOR CHEMICAL VAPOR DEPOSITION OF MICROSTRUCTURES

    OpenAIRE

    1989-01-01

    Tungsten and nickel carbonyls were used to produce metal microstructures by laser-induced chemical vapor deposition (CVD) on various substrates. The deposition rate of microstructures produced by thermodecomposition of W(CO)6 on Si substrates heated with a cw Ar+ laser beam was relatively low (10 to 30 nm/s) even at high temperatures (above 900°C). Ni microstructures were deposited on quartz substrates irradiated with a CO2 laser beam. Relatively high laser powers were needed to heat the Ni s...

  11. Penetration control in laser welding of sheet metal

    NARCIS (Netherlands)

    Postma, S.; Aarts, R.G.K.M.; Meijer, Johan; Jonker, J.B.

    2002-01-01

    For economical reasons it is desirable to apply the highest possible speed during laser welding. Increasing the welding speed at a certain laser power might result in insufficient penetration of the weld. This work describes the design of a feedback controller, which is able to maintain full penetra

  12. Microstructure and chemical bond evolution of diamond-like carbon films machined by femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing; Wang, Chunhui [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Yongsheng, E-mail: yongshengliu@nwpu.edu.cn [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Cheng, Laifei [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Weinan [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China); Zhang, Qing [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Yang, Xiaojun [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China)

    2015-06-15

    Highlights: • The machining depth was essentially proportional to the laser power. • The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. And the number of nanoparticles increased with the processing power as well. • It revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. • It showed that a great decrease of sp{sup 3}/sp{sup 2} after laser treatment. - Abstract: Femtosecond laser is of great interest for machining high melting point and hardness materials such as diamond-like carbon, SiC ceramic, et al. In present work, the microstructural and chemical bond evolution of diamond-like carbon films were investigated using electron microscopy and spectroscopy techniques after machined by diverse femtosecond laser power in air. The results showed the machining depth was essentially proportional to the laser power. The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. Considering the D and G Raman band parameters on the laser irradiation, it revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. X-ray photoelectron spectroscopy analysis showed a great decrease of sp{sup 3}/sp{sup 2} after laser treatment.

  13. Digital control of diode laser for atmospheric spectroscopy

    Science.gov (United States)

    Menzies, R. T.; Rutledge, C. W. (Inventor)

    1985-01-01

    A system is described for remote absorption spectroscopy of trace species using a diode laser tunable over a useful spectral region of 50 to 200 cm(-1) by control of diode laser temperature over range from 15 K to 100 K, and tunable over a smaller region of typically 0.1 to 10 cm(-1) by control of the diode laser current over a range from 0 to 2 amps. Diode laser temperature and current set points are transmitted to the instrument in digital form and stored in memory for retrieval under control of a microprocessor during measurements. The laser diode current is determined by a digital to analog converter through a field effect transistor for a high degree of ambient temperature stability, while the laser diode temperature is determined by set points entered into a digital to analog converter under control of the microprocessor. Temperature of the laser diode is sensed by a sensor diode to provide negative feedback to the temperature control circuit that responds to the temperature control digital to analog converter.

  14. Picosecond lasers with the dynamical operation control

    Science.gov (United States)

    Mikheev, N. G.; Morozov, V. B.; Olenin, A. N.; Yakovlev, D. V.

    2016-04-01

    Numerical model for simulation of generation process in advanced pulse-periodic high-peak-power picosecond diode-pumped Nd:YAG and Nd:YLF lasers has been developed. The model adequately describes picosecond pulse formation governed by active and passive mode-locking, negative feedback and adjustable loss level in the oscillator cavity. Optical jitter of output pulses attributed to laser generation development from spontaneous noise level was evaluated using statistical analysis of calculation results. In the presented laser scheme, minimal jitter value on the level ~40 ps was estimated.

  15. Controlling Laser Plasma Instabilities Using Temporal Bandwidth

    Science.gov (United States)

    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.

  16. High stable power control of a laser diode

    Institute of Scientific and Technical Information of China (English)

    YANG Jiu-ru; LI Cheng; YE Hong-an; L(U) Guo-hui; JIA Shi-lou

    2006-01-01

    In this paper,the low and the high frequency noises of a laser diode have been analyzed. Based on the analysis a novel scheme that adapts analog and digital hybrid techniques is proposed to stabilize the output power of a laser diode. With the hybrid controller,the low and the high frequency noises of a laser diode are conspicuously reduced.By accurate calculation,the short-term stability of the output power of laser diode reaches ±0.55‰, and the long-term stability is ±0.7‰.

  17. Pulse shape control in a dual cavity laser: numerical modeling

    Science.gov (United States)

    Yashkir, Yuri

    2006-04-01

    We present a numerical model of the laser system for generating a special shape of the pulse: a steep peak at the beginning followed by a long pulse tail. Laser pulses of this nature are required for various applications (laser material processing, optical breakdown spectroscopy, etc.). The laser system consists of two "overlapped" cavities with different round-trip times. The laser crystal, the Q-switching element, the back mirror, and the output coupler are shared. A shorter pulse is generated in a short cavity. A small fraction of this pulse is injected into the long cavity as a seed. It triggers generation of the longer pulse. The output emission from this hybrid laser produces a required pulse shape. Parameters of the laser pulse (ratios of durations and energies of short- and long- pulse components) can be controlled through cavity length and the output coupler reflection. Modelling of the laser system is based on a set of coupled rate equations for dynamic variables of the system: the inverse population in an active laser media and photon densities in coupled cavities. Numerical experiments were provided with typical parameters of a Nd:YAG laser to study the system behaviour for different combinations of parameters.

  18. CO2 laser scribe of chemically strengthened glass with high surface compressive stress

    Science.gov (United States)

    Li, Xinghua; Vaddi, Butchi R.

    2011-03-01

    Chemically strengthened glass is finding increasing use in handheld, IT and TV cover glass applications. Chemically strengthened glass, particularly with high (>600MPa) compressive stress (CS) and deeper depth of layer (DOL), enable to retain higher strength after damage than non-strengthened glass when its surface is abraded. Corning Gorilla® Glass has particularly proven to be advantageous over competition in this attribute. However, due to high compressive stress (CS) and Central Tension (CT) cutting ion-exchanged glass is extremely difficult and often unmanageable where ever the applications require dicing the chemically strengthened mother glass into smaller parts. We at Corning have developed a CO2 laser scribe and break method (LSB) to separate a single chemically strengthened glass sheet into plurality of devices. Furthermore, CO2 laser scribe and break method enables debris-free separation of glass with high edge strength due to its mirror-like edge finish. We have investigated laser scribe and break of chemically strengthened glass with surface compressive stress greater than 600 MPa. In this paper we present the results of CO2 scribe and break method and underlying laser scribing mechanisms. We demonstrated cross-scribe repetitively on GEN 2 size chemically strengthened glass substrates. Specimens for edge strength measurements of different thickness and CS/DOL glass were prepared using the laser scribe and break technique. The specimens were tested using the standard 4-point bend method and the results are presented.

  19. Preparation of γ-Al2O3 films by laser chemical vapor deposition

    Science.gov (United States)

    Gao, Ming; Ito, Akihiko; Goto, Takashi

    2015-06-01

    γ- and α-Al2O3 films were prepared by chemical vapor deposition using CO2, Nd:YAG, and InGaAs lasers to investigate the effects of varying the laser wavelength and deposition conditions on the phase composition and microstructure. The CO2 laser was found to mostly produce α-Al2O3 films, whereas the Nd:YAG and InGaAs lasers produced γ-Al2O3 films when used at a high total pressure. γ-Al2O3 films had a cauliflower-like structure, while the α-Al2O3 films had a dense and columnar structure. Of the three lasers, it was the Nd:YAG laser that interacted most with intermediate gas species. This promoted γ-Al2O3 nucleation in the gas phase at high total pressure, which explains the cauliflower-like structure of nanoparticles observed.

  20. The effects of motive gas physical properties on the performance of ejector for chemical lasers

    Science.gov (United States)

    Jin, Jungkun; Kim, Sehoon; Kwon, Hyuckmo; Kwon, Sejin

    2005-03-01

    Axi-symmetric annular type ejector has been developed as a pressure recovery system for HF/DF chemical laser. Ejector was tested using air as operating gases and low-pressure entrained flow was obtained. In this paper, we changed motive gas since operating gases for chemical laser system are products of chemical reaction. By selection of motive gas, physical properties of operating gas changes, therefore the performance of ejector is different for each motive gas, i.e., specific heat at constant pressure (CP) and average molecular weight (MW) on the effectiveness of ejection. The research was carried out by both numerical analysis using commercial CFD code, FLUENT and experiments.

  1. Control of the differential interference contrast in reinjected bimode laser

    CERN Document Server

    Lacot, Eric; Hugon, Olivier; de Chatellus, Hugues Guillet

    2016-01-01

    We have demonstrated, both theoretically and experimentally, that it is possible to control (i.e., to enhance or cancel) the contrast of the interference pattern appearing in the intensity images obtained with a laser optical feedback imaging (LOFI) setup using a bimode laser. The laser is composed of two coupled orthogonally polarized states that interact (i.e., interfere) through the cross saturation laser dynamics. We created the contrast control by choosing the frequency shift (i.e., the beating frequency) between the feedback electric fields and the intracavity electric fields. We have shown that the interference contrast of the output power modulation of the laser total intensity is independent from the frequency shift and is always maximal. On the other hand, the interference contrast of each polarization state is frequency dependent. We obtained the maximal contrast when the frequency shift was equal to one of the resonance frequencies of the bimode dynamics, and was very low (and almost cancels) for ...

  2. A Polarization Controlled Switchable Multiwavelength Erbium-Doped Fibre Laser

    Institute of Scientific and Technical Information of China (English)

    冯新焕; 刘艳格; 孙磊; 袁树忠; 开桂云; 董孝义

    2004-01-01

    A polarization controlled switchable multiwavelength erbium-dopedfibre laser with overlapping cavities is proposed. The wavelengths are specified by two Bragg gratings in polarization-maintaining PANDA fibre. The proposed laser can be designed to be operated in stable four-wavelength or wavelength switching modes only by simple adjustment of two polarization controllers. For wavelength switching, four single-wavelength, six dualwavelength, and four three-wavelength operations have been obtained. The minimum wavelength spacing is only about 0.4 nm.

  3. Semiconductor Laser Lidar Wind Velocity Sensor for Turbine Control

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Hu, Qi; Pedersen, Christian

    2014-01-01

    A dual line-of-sight CW lidar that measures both wind speed and direction is presented . The wind lidar employs a semiconductor laser, which allows for inexpensive remote sensors geared towards enhanced control of wind turbines .......A dual line-of-sight CW lidar that measures both wind speed and direction is presented . The wind lidar employs a semiconductor laser, which allows for inexpensive remote sensors geared towards enhanced control of wind turbines ....

  4. Chemical detection and laser wavelength stabilization employing spectroscopic absorption via laser compliance voltage sensing

    Energy Technology Data Exchange (ETDEWEB)

    Taubman, Matthew S.; Phillips, Mark C.

    2016-01-12

    Systems and methods are disclosed that provide a direct indication of the presence and concentration of an analyte within the external cavity of a laser device that employ the compliance voltage across the laser device. The systems can provide stabilization of the laser wavelength. The systems and methods can obviate the need for an external optical detector, an external gas cell, or other sensing region and reduce the complexity and size of the sensing configuration.

  5. Chemical Structure by Laser-Produced X-Rays.

    Science.gov (United States)

    1982-04-02

    replicating sub-micrometer line- width patterns. (2) Besides replicating test patterns, the tech- nique has been used to fabricare surface acoustic wave...infrared prepulse of 30ns width, which has been chipped off the main laser pulse is focused with a cylindrical lens onto a rectangular region comprising

  6. A high repetition rate passively Q-switched microchip laser for controllable transverse laser modes

    Science.gov (United States)

    Dong, Jun; Bai, Sheng-Chuang; Liu, Sheng-Hui; Ueda, Ken-Ichi; Kaminskii, Alexander A.

    2016-05-01

    A Cr4+:YAG passively Q-switched Nd:YVO4 microchip laser for versatile controllable transverse laser modes has been demonstrated by adjusting the position of the Nd:YVO4 crystal along the tilted pump beam direction. The pump beam diameter-dependent asymmetric saturated inversion population inside the Nd:YVO4 crystal governs the oscillation of various Laguerre-Gaussian, Ince-Gaussian and Hermite-Gaussian modes. Controllable transverse laser modes with repetition rates over 25 kHz and up to 183 kHz, depending on the position of the Nd:YVO4 crystal, have been achieved. The controllable transverse laser beams with a nanosecond pulse width and peak power over hundreds of watts have been obtained for potential applications in optical trapping and quantum computation.

  7. Laser Soldering of Rat Skin Using a Controlled Feedback System

    Directory of Open Access Journals (Sweden)

    Mohammad Sadegh Nourbakhsh

    2009-03-01

    Full Text Available Introduction: Laser tissue soldering using albumin and indocyanine green dye (ICG is an effective technique utilized in various surgical procedures. The purpose of this study was to perform laser soldering of rat skin under a feedback control system and compare the results with those obtained using standard sutures. Material and Methods: Skin incisions were made over eight rats’ dorsa, which were subsequently closed using different wound closure interventions in two groups: (a using a temperature controlled infrared detector or (b by suture. Tensile strengths were measured at 2, 5, 7 and 10 days post-incision. Histological examination was performed at the time of sacrifice. Results: Tensile strength results showed that during the initial days following the incisions, the tensile strengths of the sutured samples were greater than the laser samples. However, 10 days after the incisions, the tensile strengths of the laser soldered incisions were higher than the sutured cuts. Histopathological examination showed a preferred wound healing response in the soldered skin compared with the control samples. The healing indices of the laser soldered repairs (426 were significantly better than the control samples (340.5. Conclusion: Tissue feedback control of temperature and optical changes in laser soldering of skin leads to a higher tensile strength and better histological results and hence this method may be considered as an alternative to standard suturing.

  8. Vacuum Ultraviolet Laser Probe of Chemical Dynamics of Aerospace Relevance

    Science.gov (United States)

    2012-09-12

    valuable for modeling aerospace environments using the Direct Simulation Monte Carlo and Particles in Cell methods. Environments of interest to the...School of Chemical Biology and Biotechnology”, Shenzhen , China, Nov. 21, 2010. 29. C. Y. Ng, “The Role of Basic (Chemical) Research in Modern

  9. Gain generator optimization for hydrogen fluoride overtone and fundamental chemical lasers

    Science.gov (United States)

    Duncan, William A.; Patterson, Stanley P.; Graves, Bruce R.; Sollee, Jeffrey L.; Yonehara, Gordon N.; Dering, John P.

    1993-06-01

    The hydrogen fluoride (HF) chemical laser is the baseline concept for SDIO space based laser (SBL) weapons systems. Ground based tests at power levels appropriate for this application have been demonstrated. Because the brightness of a laser beam projected to the far field is inversely proportional to the square of the wavelength, shorter wavelengths are desirable to enhance brightness on target. Development of the HF overtone chemical laser ((lambda) equals 1.3 - 1.4 micrometers ) as a growth technology for SBL applications has proceeded rapidly during the past several years. This paper reviews the parametric characterization and optimization of the Hypersonic, Low-Temperature (HYLTE) nozzle concept for HF overtone and HF fundamental performance. The experiments utilize advanced multilayer dielectric coatings on uncooled silicon substrates. The experimental results reported include laser power, small signal gain, mode footprint, and spectral content. The design of a multiple nozzle HYLTE module as a building block to an advanced high power HF chemical laser device is presented. Design philosophy emphasizes traceability from an intermediate size linear module to a full scale cylindrical gain generator for SBL applications. The key issues addressed are power scalability, fabricability, regenerative cooling capability, and thermal/structural performance.

  10. Method and apparatus for laser-controlled proton beam radiology

    Science.gov (United States)

    Johnstone, Carol J.

    1998-01-01

    A proton beam radiology system provides cancer treatment and proton radiography. The system includes an accelerator for producing an H.sup.- beam and a laser source for generating a laser beam. A photodetachment module is located proximate the periphery of the accelerator. The photodetachment module combines the H.sup.- beam and laser beam to produce a neutral beam therefrom within a subsection of the H.sup.- beam. The photodetachment module emits the neutral beam along a trajectory defined by the laser beam. The photodetachment module includes a stripping foil which forms a proton beam from the neutral beam. The proton beam is delivered to a conveyance segment which transports the proton beam to a patient treatment station. The photodetachment module further includes a laser scanner which moves the laser beam along a path transverse to the cross-section of the H.sup.- beam in order to form the neutral beam in subsections of the H.sup.- beam. As the scanning laser moves across the H.sup.- beam, it similarly varies the trajectory of the proton beam emitted from the photodetachment module and in turn varies the target location of the proton beam upon the patient. Intensity modulation of the proton beam can also be achieved by controlling the output of the laser.

  11. Physico-Chemical Dynamics of Nanoparticle Formation during Laser Decontamination

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, M.D.

    2005-06-01

    Laser-ablation based decontamination is a new and effective approach for simultaneous removal and characterization of contaminants from surfaces (e.g., building interior and exterior walls, ground floors, etc.). The scientific objectives of this research are to: (1) characterize particulate matter generated during the laser-ablation based decontamination, (2) develop a technique for simultaneous cleaning and spectroscopic verification, and (3) develop an empirical model for predicting particle generation for the size range from 10 nm to tens of micrometers. This research project provides fundamental data obtained through a systematic study on the particle generation mechanism, and also provides a working model for prediction of particle generation such that an effective operational strategy can be devised to facilitate worker protection.

  12. Microprocessor-controlled laser tracker for atmospheric sensing

    Science.gov (United States)

    Johnson, R. A.; Webster, C. R.; Menzies, R. T.

    1985-01-01

    An optical tracking system comprising a visible HeNe laser, an imaging detector, and a microprocessor-controlled mirror, has been designed to track a moving retroreflector located up to 500 m away from an atmospheric instrument and simultaneously direct spectrally tunable infrared laser radiation to the retroreflector for double-ended, long-path absorption measurements of atmospheric species. The tracker has been tested during the recent flight of a balloon-borne tunable diode laser absorption spectrometer which monitors the concentrations of stratospheric species within a volume defined by a 0.14-m-diameter retroreflector lowered 500 m below the instrument gondola.

  13. Semiconductor Laser Wind Lidar for Turbine Control

    DEFF Research Database (Denmark)

    Hu, Qi

    instead of the conventional fiber-lasers. Besides its advantage of lower cost, the relative intensity noise, which peaks around 1 MHz for fiber lasers, is inherently avoided by using a semiconductor light source. The impact of the line width increment on the SNR in the application of wind measurement has...... and demonstrated in this work. The challenge, aside from cost and compactness, is to ensure a long lifetime without regular maintenance, since the wind turbines are designed to last for 20 years. Finally, field test results of various measurement campaigns, designed to evaluate our lidar design, are presented here...... historical overview within the topic of wind lidar systems. Both the potential and the challenges of an industrialized wind lidar has been addressed here. Furthermore, the basic concept behind the heterodyne detection and a brief overview of the lidar signal processing is explained; and a simple...

  14. Electron-beam-controlled laser with a grid-controlled electron gun

    Energy Technology Data Exchange (ETDEWEB)

    Avanesyan, V.S.; Dutov, A.I.; Lakhno, Y.V.; Malkhov, L.N.

    1977-08-01

    An experimental investigation was made of an electron-beam-controlled carbon dioxide laser with an electron gun in which the beam current was modulated by a control grid. The design features of the electron gun and laser are described and their performance is reported. Observations of instabilities of the electron beam in the gun are reported and methods for eliminating them are suggested.

  15. Tunable degree of localization in random lasers with controlled interaction

    CERN Document Server

    Leonetti, Marco; Lopez, Cefe

    2012-01-01

    We show that the degree of localization for the modes of a random laser (RL) is affected by the inter mode interaction that is controlled by shaping the spot of the pump laser. By experimentally investigating the spatial properties of the lasing emission we infer that strongly localized modes are activated in the low interacting regime while in the strongly interacting one extended modes are found lasing. Thus we demonstrate that the degree o localization may be finely tuned at the micrometer level.

  16. Controllable Femtosecond Laser-Induced Dewetting for Plasmonic Applications

    CERN Document Server

    Makarov, Sergey V; Mukhin, Ivan S; Shishkin, Ivan I; Zuev, Dmitriy A; Mozharov, Alexey M; Krasnok, Alexander E; Belov, Pavel A

    2015-01-01

    Dewetting of thin metal films is one of the most widespread method for functional plasmonic nanostructures fabrication. However, simple thermal-induced dewetting does not allow to control degree of nanostructures order without additional lithographic process steps. Here we propose a novel method for lithography-free and large-scale fabrication of plasmonic nanostructures via controllable femtosecond laser-induced dewetting. The method is based on femtosecond laser surface pattering of a thin film followed by a nanoscale hydrodynamical instability, which is found to be very controllable under specific irradiation conditions. We achieve control over degree of nanostructures order by changing laser irradiation parametrs and film thickness. This allowed us to exploit the method for the broad range of applications: resonant light absorbtion and scattering, sensing, and potential improving of thin-film solar cells.

  17. Electronically controlled heat sink for high-power laser diodes

    Science.gov (United States)

    Vetrovec, John

    2009-05-01

    We report on a novel electronically controlled active heat sink for high-power laser diodes offering unparalleled capacity in high-heat flux handling and temperature control. The heat sink receives diode waste heat at high flux and transfers it at reduced flux to environment, coolant fluid, heat pipe, or structure. Thermal conductance of the heat sink is electronically adjustable, allowing for precise control of diode temperature and the diode light wavelength. When pumping solid-state or alkaline vapor lasers, diode wavelength can be precisely temperature-tuned to the gain medium absorption features. This paper presents the heat sink physics, engineering design, and performance modeling.

  18. Taming random lasers through active spatial control of the pump.

    Science.gov (United States)

    Bachelard, N; Andreasen, J; Gigan, S; Sebbah, P

    2012-07-20

    Active control of the spatial pump profile is proposed to exercise control over random laser emission. We demonstrate numerically the selection of any desired lasing mode from the emission spectrum. An iterative optimization method is employed, first in the regime of strong scattering where modes are spatially localized and can be easily selected using local pumping. Remarkably, this method works efficiently even in the weakly scattering regime, where strong spatial overlap of the modes precludes spatial selectivity. A complex optimized pump profile is found, which selects the desired lasing mode at the expense of others, thus demonstrating the potential of pump shaping for robust and controllable single mode operation of a random laser.

  19. Taming random lasers through active spatial control of the pump

    CERN Document Server

    Bachelard, Nicolas; Gigan, Sylvain; Sebbah, Patrick

    2012-01-01

    Active control of the pump spatial profile is proposed to exercise control over random laser emission. We demonstrate numerically the selection of any desired lasing mode from the emission spectrum. An iterative optimization method is employed, first in the regime of strong scattering where modes are spatially localized and can be easily selected using local pumping. Remarkably, this method works efficiently even in the weakly scattering regime, where strong spatial overlap of the modes precludes spatial selectivity. A complex optimized pump profile is found, which selects the desired lasing mode at the expense of others, thus demonstrating the potential of pump shaping for robust and controllable singlemode operation of a random laser.

  20. Antimony sulfide thin films prepared by laser assisted chemical bath deposition

    Science.gov (United States)

    Shaji, S.; Garcia, L. V.; Loredo, S. L.; Krishnan, B.; Aguilar Martinez, J. A.; Das Roy, T. K.; Avellaneda, D. A.

    2017-01-01

    Antimony sulfide (Sb2S3) thin films were prepared by laser assisted chemical bath deposition (LACBD) technique. These thin films were deposited on glass substrates from a chemical bath containing antimony chloride, acetone and sodium thiosulfate under various conditions of normal chemical bath deposition (CBD) as well as in-situ irradiation of the chemical bath using a continuous laser of 532 nm wavelength. Structure, composition, morphology, optical and electrical properties of the Sb2S3 thin films produced by normal CBD and LACBD were analyzed by X-Ray diffraction (XRD), Raman Spectroscopy, Atomic force microscopy (AFM), X-Ray photoelectron spectroscopy (XPS), UV-vis spectroscopy and Photoconductivity. The results showed that LACBD is an effective synthesis technique to obtain Sb2S3 thin films for optoelectronic applications.

  1. Advantages of Laser Polarimetry Applied to Tequila Industrial Process Control

    Science.gov (United States)

    Fajer, V.; Rodriguez, C.; Flores, R.; Naranjo, S.; Cossio, G.; Lopez, J.

    2002-03-01

    The development of a polarimetric method for crude and cooked agave juice quality control not only by direct polarimetric measurement also by means of laser polarimeter LASERPOL 101M used as a liquid chromatographic detector is presented. The viability and advantage of this method for raw material quality control and during Tequila industrial process is shown.

  2. Benchmarking Advanced Control Algorithms for a Laser Scanner System

    DEFF Research Database (Denmark)

    Stoustrup, Jakob; Ordys, A.W.; Smillie, I.

    1996-01-01

    The paper describes tests performed on the laser scanner system toassess feasibility of modern control techniques in achieving a requiredperformance in the trajectory following problem. The two methods tested areQTR H-infinity and Predictive Control. The results are ilustated ona simulation example....

  3. Advanced nozzle characterization for hydrogen fluoride overtone chemical lasers

    Science.gov (United States)

    Duncan, William A.; Patterson, Stanley P.; Graves, Bruce R.; Sollee, Jeffrey L.; Yonehara, Gordon N.; Dering, John P.

    1992-07-01

    The parametric characterization and optimization of the hypersonic, low-temperature (HYLTE) nozzle concept for the hydrogen fluoride (HF) overtone and HF fundamental performance are reviewed. The HF fundamental space-based laser for weapons systems is considered to be more mature, nearer term potential application than the overtone. Emphasis is placed on the Task 3 advanced gain generator technology configurations (AGGTC) aimed at a thorough characterization in the fundamental regime. The experiments were based on advanced multilayer dielectric coatings on uncooled silicon substrates. It is concluded that the Task 3 AGGTC hardware functioned quite well in optimizing the performance of the HYLTE nozzle concept.

  4. Fabrication of silicon nanowire arrays by near-field laser ablation and metal-assisted chemical etching

    Science.gov (United States)

    Brodoceanu, D.; Alhmoud, H. Z.; Elnathan, R.; Delalat, B.; Voelcker, N. H.; Kraus, T.

    2016-02-01

    We present an elegant route for the fabrication of ordered arrays of vertically-aligned silicon nanowires with tunable geometry at controlled locations on a silicon wafer. A monolayer of transparent microspheres convectively assembled onto a gold-coated silicon wafer acts as a microlens array. Irradiation with a single nanosecond laser pulse removes the gold beneath each focusing microsphere, leaving behind a hexagonal pattern of holes in the gold layer. Owing to the near-field effects, the diameter of the holes can be at least five times smaller than the laser wavelength. The patterned gold layer is used as catalyst in a metal-assisted chemical etching to produce an array of vertically-aligned silicon nanowires. This approach combines the advantages of direct laser writing with the benefits of parallel laser processing, yielding nanowire arrays with controlled geometry at predefined locations on the silicon surface. The fabricated VA-SiNW arrays can effectively transfect human cells with a plasmid encoding for green fluorescent protein.

  5. Toward the Realization of a Compact Chemical Sensor Platform using Quantum Cascade Lasers

    Science.gov (United States)

    2015-09-01

    ARL-RP-0550 ● SEP 2015 US Army Research Laboratory Toward the Realization of a Compact Chemical Sensor Platform using Quantum...ARL-RP-0550 ● SEP 2015 US Army Research Laboratory Toward the Realization of a Compact Chemical Sensor Platform using Quantum Cascade...Lasers by Ellen L Holthoff, Logan S Marcus, and Paul M Pellegrino Sensors and Electron Devices Directorate, ARL A reprint from Proc

  6. Hierarchical Process Control of Chemical Vapor Infiltration.

    Science.gov (United States)

    1995-05-31

    in these variables with reference to Figure 8. Conventional PID controllers are beneficially employed at this level in order to retain industry...to achieve minimum controlled-variable variations. PID controllers are beneficially employed at this level to retain industry standard functions useful

  7. Chemical dosing for sulfide control in Australia: An industry survey.

    Science.gov (United States)

    Ganigue, Ramon; Gutierrez, Oriol; Rootsey, Ray; Yuan, Zhiguo

    2011-12-01

    Controlling sulfide (H(2)S) production and emission in sewer systems is critical due to the corrosion and malodour problems that sulfide causes. Chemical dosing is one of the most commonly used measures to mitigate these problems. Many chemicals have been reported to be effective for sulfide control, but the extent of success varies between chemicals and is also dependent on how they are applied. This industry survey aims to summarise the current practice in Australia with the view to assist the water industry to further improve their practices and to identify new research questions. Results showed that dosing is mainly undertaken in pressure mains. Magnesium hydroxide, sodium hydroxide and nitrate are the most commonly used chemicals for sewers with low flows. In comparison, iron salts are preferentially used for sulfide control in large systems. The use of oxygen injection has declined dramatically in the past few years. Chemical dosing is mainly conducted at wet wells and pumping stations, except for oxygen, which is injected into the pipe. The dosing rates are normally linked to the control mechanisms of the chemicals and the dosing locations, with constant or profiled dosing rates usually applied. Finally, key opportunities for improvement are the use of mathematical models for the selection of chemicals and dosing locations, on-line dynamic control of the dosing rates and the development of more cost-effective chemicals for sulfide control.

  8. Laser-induced fluorescence: quantitative analysis of atherosclerotic plaque chemical content in human aorta

    Science.gov (United States)

    Dai, Erbin; Wishart, David; Khoury, Samir; Kay, Cyril M.; Jugdutt, Bodh I.; Tulip, John; Lucas, Alexandra

    1996-05-01

    We have been studying laser-induced fluorescence as a technique for identification of selected changes in the chemical composition of atherosclerotic plaque. Formulae for quantification of chemical changes have been developed based upon analysis of fluorescence emission spectra using multiple regression analysis and the principal of least squares. The intima of human aortic necropsy specimens was injected with chemical compounds present in atherosclerotic plaque. Spectra recorded after injection of selected chemical components found in plaque (collagen I, III, IV, elastin and cholesterol) at varying concentrations (0.01 - 1.0 mg) were compared with saline injection. A single fiber system was used for both fluorescence excitation (XeCl excimer laser, 308 nm, 1.5 - 2.0 mJ/ pulse, 5 Hz) and fluorescence emission detection. Average spectra for each chemical have been developed and the wavelengths of peak emission intensity identified. Curve fitting analysis as well as multiple regression analysis were used to develop formulae for assessment of chemical content. Distinctive identifying average curves were established for each chemical. Excellent correlations were identified for collagen I, III, and IV, elastin, and cholesterol (R2 equals 0.92 6- 0.997). Conclusions: (1) Fluorescence spectra of human aortas were significantly altered by collagen I, collagen III, elastin and cholesterol. (2) Fluorescence spectroscopic analysis may allow quantitative assessment of atherosclerotic plaque chemical content in situ.

  9. Scalable shape-controlled fabrication of curved microstructures using a femtosecond laser wet-etching process

    Energy Technology Data Exchange (ETDEWEB)

    Bian, Hao; Yang, Qing; Chen, Feng, E-mail: chenfeng@mail.xjtu.edu.cn; Liu, Hewei; Du, Guangqing; Deng, Zefang; Si, Jinhai; Yun, Feng; Hou, Xun

    2013-07-01

    Materials with curvilinear surface microstructures are highly desirable for micro-optical and biomedical devices. However, realization of such devices efficiently remains technically challenging. This paper demonstrates a facile and flexible method to fabricate curvilinear microstructures with controllable shapes and dimensions. The method composes of femtosecond laser exposures and chemical etching process with the hydrofluoric acid solutions. By fixed-point and step-in laser irradiations followed by the chemical treatments, concave microstructures with different profiles such as spherical, conical, bell-like and parabola were fabricated on silica glasses. The convex structures were replicated on polymers by the casting replication process. In this work, we used this technique to fabricate high-quality microlens arrays and high-aspect-ratio microwells which can be used in 3D cell culture. This approach offers several advantages such as high-efficient, scalable shape-controllable and easy manipulations. - Highlights: • We demonstrate a flexible method to fabricate curvilinear microstructures. • This method composes of femtosecond laser exposures and chemical etching process. • Concave microstructures with different profiles were fabricated on silica glasses. • High-quality microlens arrays and high-aspect-ratio microwells were fabricated.

  10. Controlling strongly correlated dust clusters with lasers

    CERN Document Server

    Thomsen, Hauke; Bonitz, Michael; Schablinski, Jan; Block, Dietmar; Schella, André; Melzer, André

    2014-01-01

    The most attractive feature of dusty plasmas is the possibility to create strong correlations at room temperatures. At the same time, these plasmas allow for a precise diagnostics with single-particle resolution. From such measurements, the structural properties of finite two-dimensional (2D) clusters and three-dimensional (3D) spherical crystals in nearly harmonic traps-Yukawa balls-have been explored in great detail. Their structural properties-the shell compositions and the order within the shells-have been investigated and good agreement to theoretical predictions was found. Open questions on the agenda are the excitation behavior, the structural changes, and phase transitions that occur at elevated temperature. In order to increase the dust temperature in the experiment various techniques have been used. Among them, laser heating appears to have unique capabilities because it affects only the dust particles, leaving the lighter plasma components unchanged. Here we report on recent experimental results wh...

  11. ADVANCED CONTROL OF A COMPLEX CHEMICAL PROCESS

    Directory of Open Access Journals (Sweden)

    Roxana Both

    Full Text Available Abstract Three phase catalytic hydrogenation reactors are important reactors with complex behavior due to the interaction among gas, solid and liquid phases with the kinetic, mass and heat transfer mechanisms. A nonlinear distributed parameter model was developed based on mass and energy conservation principles. It consists of balance equations for the gas and liquid phases, so that a system of partial differential equations is generated. Because detailed nonlinear mathematical models are not suitable for use in controller design, a simple linear mathematical model of the process, which describes its most important properties, was determined. Both developed mathematical models were validated using plant data. The control strategies proposed in this paper are a multivariable Smith Predictor PID controller and multivariable Smith Predictor structure in which the primary controllers are derived based on Internal Model Control. Set-point tracking and disturbance rejection tests are presented for both methods based on scenarios implemented in Matlab/SIMULINK.

  12. Direct writing of carbon nanotube patterns by laser-induced chemical vapor deposition on a transparent substrate

    Energy Technology Data Exchange (ETDEWEB)

    Park, J.B. [Department of Mechatronics, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Jeong, M.S. [Advanced Photonics Research Institute, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of); Jeong, S.H., E-mail: shjeong@gist.ac.kr [Department of Mechatronics, Gwangju Institute of Science and Technology, 1 Oryong-dong, Buk-gu, Gwangju 500-712 (Korea, Republic of)

    2009-02-01

    Dot array and line patterns of multi-walled carbon nanotubes (MWCNTs) were successfully grown by laser-induced chemical vapor deposition (LCVD) on a transparent substrate at room temperature. In the proposed technique, a Nd:YVO{sub 4} laser with a wavelength of 532 nm irradiates the backside of multiple catalyst layers (Ni/Al/Cr) through a transparent substrate to induce a local temperature rise, thereby allowing the direct writing of dense dot and line patterns of MWCNTs below 10 {mu}m in size to be produced with uniform density on the controlled positions. In this LCVD method, a multiple-catalyst-layer with a Cr thermal layer is the central component for enabling the growth of dense MWCNTs with good spatial resolution.

  13. Automatic control system design of laser interferometer

    Science.gov (United States)

    Lu, Qingjie; Li, Chunjie; Sun, Hao; Ren, Shaohua; Han, Sen

    2015-10-01

    There are a lot of shortcomings with traditional optical adjustment in interferometry, such as low accuracy, time-consuming, labor-intensive, uncontrollability, and bad repetitiveness, so we treat the problem by using wireless remote control system. Comparing to the traditional method, the effect of vibration and air turbulence will be avoided. In addition the system has some peculiarities of low cost, high reliability and easy operation etc. Furthermore, the switching between two charge coupled devices (CCDs) can be easily achieved with this wireless remote control system, which is used to collect different images. The wireless transmission is achieved by using Radio Frequency (RF) module and programming the controller, pulse width modulation (PWM) of direct current (DC) motor, real-time switching of relay and high-accuracy displacement control of FAULHABER motor are available. The results of verification test show that the control system has good stability with less than 5% packet loss rate, high control accuracy and millisecond response speed.

  14. Laboratory Transferability of Optimally Shaped Laser Pulses for Quantum Control

    CERN Document Server

    Tibbetts, Katharine Moore; Rabitz, Herschel

    2013-01-01

    Optimal control experiments can readily identify effective shaped laser pulses, or "photonic reagents", that achieve a wide variety of objectives. For many practical applications, an important criterion is that a particular photonic reagent prescription still produce a good, if not optimal, target objective yield when transferred to a different system or laboratory, {even if the same shaped pulse profile cannot be reproduced exactly. As a specific example, we assess the potential for transferring optimal photonic reagents for the objective of optimizing a ratio of photoproduct ions from a family of halomethanes through three related experiments.} First, applying the same set of photonic reagents with systematically varying second- and third-order chirp on both laser systems generated similar shapes of the associated control landscape (i.e., relation between the objective yield and the variables describing the photonic reagents). Second, optimal photonic reagents obtained from the first laser system were found...

  15. Controlling a microdisk laser by local refractive index perturbation

    Energy Technology Data Exchange (ETDEWEB)

    Liew, Seng Fatt; Redding, Brandon; Cao, Hui, E-mail: hui.cao@yale.edu [Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States); Ge, Li [Department of Engineering Science and Physics, College of Staten Island, CUNY, Staten Island, New York 10314 (United States); The Graduate Center, CUNY, New York, New York 10016 (United States); Solomon, Glenn S. [Joint Quantum Institute, NIST and University of Maryland, Gaithersburg, Maryland 20899 (United States)

    2016-02-01

    We demonstrate a simple yet effective approach of controlling lasing in a semiconductor microdisk by photo-thermal effect. A continuous wave green laser beam, focused onto the microdisk perimeter, can enhance or suppress lasing in different cavity modes, depending on the position of the focused beam. Its main effect is a local modification of the refractive index of the disk, which results in an increase in the power slope of some lasing modes and a decrease of others. The boundary roughness breaks the rotational symmetry of a circular disk, allowing the lasing process to be tuned by varying the green beam position. Using the same approach, we can also fine tune the relative intensity of a quasi-degenerate pair of lasing modes. Such post-fabrication control, enabled by an additional laser beam, is flexible and reversible, thus enhancing the functionality of semiconductor microdisk lasers.

  16. Active disturbance rejection controller for chemical reactor

    Energy Technology Data Exchange (ETDEWEB)

    Both, Roxana; Dulf, Eva H.; Muresan, Cristina I., E-mail: roxana.both@aut.utcluj.ro [Technical University of Cluj-Napoca, 400114 Cluj-Napoca (Romania)

    2015-03-10

    In the petrochemical industry, the synthesis of 2 ethyl-hexanol-oxo-alcohols (plasticizers alcohol) is of high importance, being achieved through hydrogenation of 2 ethyl-hexenal inside catalytic trickle bed three-phase reactors. For this type of processes the use of advanced control strategies is suitable due to their nonlinear behavior and extreme sensitivity to load changes and other disturbances. Due to the complexity of the mathematical model an approach was to use a simple linear model of the process in combination with an advanced control algorithm which takes into account the model uncertainties, the disturbances and command signal limitations like robust control. However the resulting controller is complex, involving cost effective hardware. This paper proposes a simple integer-order control scheme using a linear model of the process, based on active disturbance rejection method. By treating the model dynamics as a common disturbance and actively rejecting it, active disturbance rejection control (ADRC) can achieve the desired response. Simulation results are provided to demonstrate the effectiveness of the proposed method.

  17. All-optical noninvasive delayed feedback control of semiconductor lasers

    CERN Document Server

    Schikora, Sylvia

    2013-01-01

    The stabilization of unstable states hidden in the dynamics of a system, in particular the control of chaos, has received much attention in the last years. Sylvia Schikora for the first time applies a well-known control method called delayed feedback control entirely in the all-optical domain. A multisection semiconductor laser receives optical feedback from an external Fabry-Perot interferometer. The control signal is a phase-tunable superposition of the laser signal and provokes the laser to operate in an otherwise unstable periodic state with a period equal to the time delay. The control is noninvasive, because the reflected signal tends to zero when the target state is reached.   The work has been awarded the Carl-Ramsauer-Prize 2012.   Contents ·         All-Optical Control Setup ·         Stable States with Resonant Fabry-Perot Feedback ·         Control of an Unstable Stationary State and of Unstable Selfpulsations ·         Controlling Chaos ·         Con...

  18. DSP-based multi-purpose control system for laser processing

    Institute of Scientific and Technical Information of China (English)

    U Tong-Hyok; ZHANG Guo-shun; XU Bao-zhong; GANG Bei; LI Cheng; WANG Meng

    2006-01-01

    A DSP-based control system for laser processing that enables the motion of laser beam in two dimensions,and the control of its power with PC or without PC is discussed. The operation and implementation of the control system along with the rapid processing of image data are presented. The purpose of the control system is to operate the laser equipments in such a manner that various programmable laser control signals are available for vector and bitmap processing of characters and pictures. This control system makes the laser processing more intelligent and flexible and can be used for welding, marking and engraving by lasers.

  19. Partial feedback unstable resonator on small scale supersonic large aperture chemical laser

    Science.gov (United States)

    Wang, Hongyan; Wang, Rui; Li, Lei

    2015-05-01

    There is always a challenge on large aperture medium power laser's resonator design, stable resonator would supports significant higher order transverse modes, folded and telescope stable resonator are too complex and not preferred by engineers, unstable resonator need rather large round trip gain to compensate its high geometric out-coupling, which is difficult for this kind of laser since its gain length is limited due to the power level and large aperture. Partial feedback unstable resonator had been proposed to tackle this difficulty since the early days of laser development, however, the debates of its effect never stopped even with those distinguished optical resonator scientists such as Siegman, Anan'ev, and Weber. Recently integrated partial feedback unstable resonator design had been successfully demonstrated on a medium size chemical oxygen iodine laser. In this paper, we carry this resonator configuration on a small scale discharge driven supersonic nozzle array Hydrogen Fluoride chemical laser, a typical large aperture short gain length device. With magnification equals 4/3, we successfully get ten Watts level ring beam output.

  20. Laser Microdissection and Atmospheric Pressure Chemical Ionization Mass Spectrometry Coupled for Multimodal Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lorenz, Matthias [ORNL; Ovchinnikova, Olga S [ORNL; Kertesz, Vilmos [ORNL; Van Berkel, Gary J [ORNL

    2013-01-01

    This paper describes the coupling of ambient laser ablation surface sampling, accomplished using a laser capture microdissection system, with atmospheric pressure chemical ionization mass spectrometry for high spatial resolution multimodal imaging. A commercial laser capture microdissection system was placed in close proximity to a modified ion source of a mass spectrometer designed to allow for sampling of laser ablated material via a transfer tube directly into the ionization region. Rhodamine 6G dye of red sharpie ink in a laser etched pattern as well as cholesterol and phosphatidylcholine in a cerebellum mouse brain thin tissue section were identified and imaged from full scan mass spectra. A minimal spot diameter of 8 m was achieved using the 10X microscope cutting objective with a lateral oversampling pixel resolution of about 3.7 m. Distinguishing between features approximately 13 m apart in a cerebellum mouse brain thin tissue section was demonstrated in a multimodal fashion including co-registered optical and mass spectral chemical images.

  1. Fibre Laser Cutting and Chemical Etching of AZ31 for Manufacturing Biodegradable Stents

    Directory of Open Access Journals (Sweden)

    Ali Gökhan Demir

    2013-01-01

    Full Text Available The use of magnesium-alloy stents shows promise as a less intrusive solution for the treatment of cardiovascular pathologies as a result of the high biocompatibility of the material and its intrinsic dissolution in body fluids. However, in addition to requiring innovative solutions in material choice and design, these stents also require a greater understanding of the manufacturing process to achieve the desired quality with improved productivity. The present study demonstrates the manufacturing steps for the realisation of biodegradable stents in AZ31 magnesium alloy. These steps include laser microcutting with a Q-switched fibre laser for the generation of the stent mesh and subsequent chemical etching for the cleaning of kerf and surface finish. Specifically, for the laser microcutting step, inert and reactive gas cutting conditions were compared. The effect of chemical etching on the reduction in material thickness, as well as on spatter removal, was also evaluated. Prototype stents were produced, and the material composition and surface quality were characterised. The potentialities of combining nanosecond laser microcutting and chemical etching are shown and discussed.

  2. Laser rangefinders for autonomous intelligent cruise control systems

    Science.gov (United States)

    Journet, Bernard A.; Bazin, Gaelle

    1998-01-01

    THe purpose of this paper is to show to what kind of application laser range-finders can be used inside Autonomous Intelligent Cruise Control systems. Even if laser systems present good performances the safety and technical considerations are very restrictive. As the system is used in the outside, the emitted average output power must respect the rather low level of 1A class. Obstacle detection or collision avoidance require a 200 meters range. Moreover bad weather conditions, like rain or fog, ar disastrous. We have conducted measurements on laser rangefinder using different targets and at different distances. We can infer that except for cooperative targets low power laser rangefinder are not powerful enough for long distance measurement. Radars, like 77 GHz systems, are better adapted to such cases. But in case of short distances measurement, range around 10 meters, with a minimum distance around twenty centimeters, laser rangefinders are really useful with good resolution and rather low cost. Applications can have the following of white lines on the road, the target being easily cooperative, detection of vehicles in the vicinity, that means car convoy traffic control or parking assistance, the target surface being indifferent at short distances.

  3. Chemical and microstructural transformations in lithium iron phosphate battery electrodes following pulsed laser exposure

    Energy Technology Data Exchange (ETDEWEB)

    Lutey, Adrian H.A., E-mail: adrian.lutey2@unibo.it [DIN, Università di Bologna, viale Risorgimento, 2, Bologna (Italy); Fiorini, Maurizio [DICAM, Università di Bologna, via Terracini, 28, Bologna (Italy); Fortunato, Alessandro; Ascari, Alessandro [DIN, Università di Bologna, viale Risorgimento, 2, Bologna (Italy)

    2014-12-15

    Highlights: • Lithium iron phosphate battery electrodes are exposed to pulsed laser radiation. • Raman spectroscopy is performed on regions approaching the incisions and cuts. • Chemical and microstructural changes in the active electrode layers are limited to the visible HAZ. • Some oxidation and degradation of the olive LiFePO{sub 4} cathode active material takes place in the HAZ. • The anode polycrystalline graphite structure becomes less ordered (higher D/G ratio) in the HAZ. - Abstract: Multi-layer lithium iron phosphate (LFP) battery electrodes are exposed to nanosecond pulsed laser radiation of wavelength 1064 nm. Test parameters are chosen to achieve characteristic interaction types ranging from partial incision of the active coating layers only to complete penetration of the electrodes with high visual cut quality. Raman spectroscopy is performed on unexposed regions and at points approaching each incision, highlighting changes in chemical composition and microstructure in the heat affected zone (HAZ). Thermogravimetric analysis is performed on the unexposed electrode active materials to distinguish the development of compositional changes under conditions of slow heating below the melting and sublimation temperatures. A brief theoretical description of the physical phenomena taking place during laser exposure is provided in terms of direct ablation during each laser pulse and vaporization or thermal degradation due to conductive heat transfer on a much longer time-scale, with characteristics of the HAZ reported in terms of these changes. For all laser exposures carried out in the study, chemical and microstructural changes are limited to the visible HAZ. Some degree of oxidation and LFP olivine phase degradation is observed in the cathode, while the polycrystalline graphite structure becomes less ordered in the anode. Where complete penetration is achieved, melting of the cathode active layer and combustion of the anode active layer take place

  4. NONLINEAR MODEL PREDICTIVE CONTROL OF CHEMICAL PROCESSES

    Directory of Open Access Journals (Sweden)

    R. G. SILVA

    1999-03-01

    Full Text Available A new algorithm for model predictive control is presented. The algorithm utilizes a simultaneous solution and optimization strategy to solve the model's differential equations. The equations are discretized by equidistant collocation, and along with the algebraic model equations are included as constraints in a nonlinear programming (NLP problem. This algorithm is compared with the algorithm that uses orthogonal collocation on finite elements. The equidistant collocation algorithm results in simpler equations, providing a decrease in computation time for the control moves. Simulation results are presented and show a satisfactory performance of this algorithm.

  5. Stoichiometry controlled oxide thin film growth by pulsed laser deposition

    NARCIS (Netherlands)

    Groenen, Rik; Smit, Jasper; Orsel, Kasper; Vailionis, Arturas; Bastiaens, Bert; Huijben, Mark; Boller, Klaus; Rijnders, Guus; Koster, Gertjan

    2015-01-01

    The oxidation of species in the plasma plume during pulsed laser deposition controls both the stoichiometry as well as the growth kinetics of the deposited SrTiO3 thin films, instead of the commonly assumed mass distribution in the plasma plume and the kinetic energy of the arriving species. It was

  6. Controlling hyperchaos in erbium-doped fibre laser

    Institute of Scientific and Technical Information of China (English)

    张胜海; 沈柯

    2003-01-01

    The dual-ring erbium-doped fibre laser shows a hyperchaotic behaviour under some conditions. The hyperchaotic behaviour can be well controlled to enter into periodicity by modulating the pumping in one of the two rings. The period is different for different modulation index at the same modulation frequency, or for different modulation frequency at the same modulation index.

  7. Direct laser additive fabrication system with image feedback control

    Energy Technology Data Exchange (ETDEWEB)

    Griffith, Michelle L. (Albuquerque, NM); Hofmeister, William H. (Nashville, TN); Knorovsky, Gerald A. (Albuquerque, NM); MacCallum, Danny O. (Edgewood, NM); Schlienger, M. Eric (Albuquerque, NM); Smugeresky, John E. (Pleasanton, CA)

    2002-01-01

    A closed-loop, feedback-controlled direct laser fabrication system is disclosed. The feedback refers to the actual growth conditions obtained by real-time analysis of thermal radiation images. The resulting system can fabricate components with severalfold improvement in dimensional tolerances and surface finish.

  8. Two-pulse laser control of nuclear and electronic motion

    DEFF Research Database (Denmark)

    Grønager, Michael; Henriksen, Niels Engholm

    1997-01-01

    We discuss an explicitly time-dependent two-pulse laser scheme for controlling where nuclei and electrons are going in unimolecular reactions. We focus on electronic motion and show, with HD+ as an example, that one can find non-stationary states where the electron (with some probability) oscilla...

  9. Two-pulse laser control of bond-selective fragmentation

    DEFF Research Database (Denmark)

    Amstrup, Bjarne; Henriksen, Niels Engholm

    1996-01-01

    We elaborate on a two-pulse (pump-pump) laser control scheme for selective bond-breaking in molecules [Amstrup and Henriksen, J. Chem. Phys. 97, 8285 (1992)]. We show, in particular, that with this scheme one can overcome the obstacle of intramolecular vibrational relaxation. As an example, we co...

  10. Ultrashort pulse laser microsurgery system with plasma luminescence feedback control

    Energy Technology Data Exchange (ETDEWEB)

    Kim, B.M.; Feit, M.D.; Rubenchik, A.M.; Gold, D.M.; Darrow, C.B.; Da Silva, L.B.

    1997-11-10

    Plasma luminescence spectroscopy was used for precise ablation of bone tissue during ultrashort pulse laser (USPL) micro-spinal surgery. Strong contrast of the luminescence spectra between bone marrow and spinal cord provided the real time feedback control so that only bone tissue can be selectively ablated while preserving the spinal cord.

  11. Roadmap to Secure Control Systems in the Chemical Sector

    Science.gov (United States)

    2009-09-01

    provide minimal protection against forgery of data or control messages. These issues are of particular concern in industries that rely on...Ammonia Refrigeration; • National Association of Chemical Distributors; • National Paint & Coatings Association; • National Petrochemical and

  12. Physics of a ballistic missile defense - The chemical laser boost-phase defense

    Science.gov (United States)

    Grabbe, Crockett L.

    1988-01-01

    The basic physics involved in proposals to use a chemical laser based on satellites for a boost-phase defense are investigated. After a brief consideration of simple physical conditions for the defense, a calculation of an equation for the number of satellites needed for the defense is made along with some typical values of this for possible future conditions for the defense. Basic energy and power requirements for the defense are determined. A sumary is made of probable minimum conditions that must be achieved for laser power, targeting accuracy, number of satellites, and total sources for power needed.

  13. Feedback control of Layerwise Laser Melting using optical sensors

    Science.gov (United States)

    Craeghs, Tom; Bechmann, Florian; Berumen, Sebastian; Kruth, Jean-Pierre

    Layerwise Laser Melting (LLM) is a layerwise production technique enabling the production of complex metallic parts. Thin powder layers are molten according to a predefined scan pattern by means of a laser source. Nowadays constant process parameters are used throughout the build, leading for some geometries to an overly thick feature size or overheating at downfacing surfaces. In this paper a monitoring and control system is presented which enables monitoring the melt pool continously at high speed throughout the building process. The signals from the sensors can be incorporated in a real-time control loop, in this way enabling feedback control of the process parameters. In this paper the experimental set-up will be first shown. Next the dynamic relation between the melt pool and the process parameters is identified. Finally the proof of concept for feedback control is demonstrated with experimental results.

  14. An acquisition control for the laser interferometer space antenna

    Energy Technology Data Exchange (ETDEWEB)

    Maghami, P G [NASA Goddard Space Flight Center, Guidance, Navigation and Control Division, Greenbelt, MD 20771 (United States); Hyde, T T [NASA Goddard Space Flight Center, Guidance, Navigation and Control Division, Greenbelt, MD 20771 (United States); Kim, J [Swales Aerospace, Inc., Greenbelt, MD 20771 (United States)

    2005-05-21

    The Laser Interferometer Space Antenna mission is a planned gravitational wave detector consisting of three spacecraft in heliocentric orbit. Laser interferometry is used to measure distance fluctuations between test masses aboard each spacecraft to the picometre level over a 5 million km separation. The disturbance reduction system comprises the pointing and positioning control of the spacecraft, electrostatic suspension control of the test masses and point-ahead and acquisition control. This paper presents an approach for the acquisition control of the LISA formation. The approach establishes one link at a time. For each link, it defocuses the incoming beams to make its light detectable by the receiving spacecraft. Simulations are performed to demonstrate the feasibility of the proposed approach.

  15. Laser- and UV-assisted modification of polystyrene surfaces for control of protein adsorption and cell adhesion

    Science.gov (United States)

    Pfleging, Wilhelm; Torge, Maika; Bruns, Michael; Trouillet, Vanessa; Welle, Alexander; Wilson, Sandra

    2009-03-01

    An appropriate choice of laser and process parameters enables new approaches for the fabrication of polymeric lab-on-chip devices with integrated functionalities. We will present our current research results in laser-assisted modification of polystyrene (PS) with respect to the fabrication of polymer devices for cell culture applications. For this purpose laser micro-patterning of PS and subsequent surface functionalization was investigated as function of laser and process parameters. A high power ArF-excimer laser radiation source with a pulse length of 19 ns as well as a high repetition ArF-excimer laser source with a pulse length of 5 ns were used in order to study the influence of laser pulse length on laser-induced surface oxidation. The change in surface chemistry was characterized by X-ray photoelectron spectroscopy and contact angle measurements. The difference between laser-assisted modification versus UV-lamp assisted modification was investigated. A photolytic activation of specific areas of the polymer surface and subsequent oxidization in oxygen or ambient air leads to a chemically modified polymer surface bearing carboxylic acid groups well-suited for controlled competitive protein adsorption or protein immobilization. Finally, distinct areas for cell growth and adhesion are obtained.

  16. Preparation and analysis of chemically gradient functional bioceramic coating formed by pulsed laser deposition.

    Science.gov (United States)

    Rajesh, P; Muraleedharan, C V; Sureshbabu, S; Komath, Manoj; Varma, Harikrishna

    2012-02-01

    Bioactive ceramic coatings based on calcium phosphates yield better functionality in the human body for a variety of metallic implant devices including orthopaedic and dental prostheses. In the present study chemically and hence functionally gradient bioceramic coating was obtained by pulsed laser deposition method. Calcium phosphate bioactive ceramic coatings based on hydroxyapatite (HA) and tricalcium phosphate (TCP) were deposited over titanium substrate to produce gradation in physico-chemical characteristics and in vitro dissolution behaviour. Sintered targets of HA and α-TCP were deposited in a multi target laser deposition system. The obtained deposits were characterized by X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. Inductively coupled plasma spectroscopy was used to estimate the in vitro dissolution behaviour of coatings. The variation in mechanical property of the gradient layer was evaluated through scratch test and micro-indentation hardness. The bioactivity was examined in vitro with respect to the ability of HA layer to form on the surface as a result of contact with simulated body fluid. It could be inferred that chemically gradient functional bioceramic coating can be produced by laser deposition of multiple sintered targets with variable chemical composition.

  17. Chemical control of Vorticella bioactuator using microfluidics.

    Science.gov (United States)

    Nagai, Moeto; Ryu, Sangjin; Thorsen, Todd; Matsudaira, Paul; Fujita, Hiroyuki

    2010-06-21

    In this report, we demonstrate a microfluidic platform to control the stalk contraction and extension of Vorticella convallaria by changing concentration of Ca2+ with pneumatically-actuated elastomeric microvalves. Habitation, extraction and control of V. convallaria were carried out in a PDMS-based microfluidic device. By treating the cells with the permeant saponin, external actuation of cell-anchoring stalk between an extended and contracted state was achieved by cyclic exposure of the cells to a Ca2+ buffer (10(-6) M) and a rinse buffer containing EGTA as a chelation agent. When solutions were switched, the stalk contracted and extended responding to the ambient Ca2+ concentration change. The length of the stalk changed between 20 and 60 microm, resulting in a working distance of about 40 microm.

  18. Laser Controlling Wavepacket Trains of a Paul Trapped Ion

    Institute of Scientific and Technical Information of China (English)

    CAI Li-Hua; HAI Wen-Hua; WU Yun-Wen

    2006-01-01

    We have studied the quantum and classical motions of a single Paul trapped ion interacting with a timeperiodic laser field. By using the test-function method, we construct n exact solutions of quantum dynamics that describe the generalized squeezed coherent states with the expectation orbits being the corresponding classical ones. The spacetime evolutions of the exact probability densities show some wavepacket trains. It is demonstrated analytically that by adjusting the laser intensity and frequency, we can control the center motions of the wavepacket trains. We also discuss the other physical properties such as the expectation value of energy, the widths and heights of the wavepackets, and the resonance loss of stability.

  19. Laser control of double proton transfer in porphycenes. Towards an ultrafast switch for photonic molecular wires

    CERN Document Server

    Abdel-Latif, Mahmoud K

    2010-01-01

    Electronic excitation energy transfer along a molecular wire depends on the relative orientation of the electronic transition dipole moments of neighboring chromophores. In porphycenes this orientation is changed upon double proton transfer in the electronic ground state. We explore the possibility to trigger such a double proton transfer reaction by means of an infrared pump-dump laser control scheme. To this end a quantum chemical characterization of an asymmetrically substituted porphycene is performed using density functional theory. Ground state geometries, the topology of the potential energy surface for double proton transfer, and S0->S1 transition energies are compared with the parent compound porphycene and a symmetric derivative. Employing a simple two-dimensional model for the double proton transfer, which incorporates sequential and concerted motions, quantum dynamics simulations of the laser driven dynamics are performed which demonstrate tautomerization control. Based on the orientation of the t...

  20. Coupling chemical networks to hydrogels controls oscillatory behavior

    CERN Document Server

    Reeves, Daniel; Pérez-Mercader, Juan

    2015-01-01

    In this letter, we demonstrate that oscillations and excitable behavior can be imparted to a chemical network by coupling the network to an active hydrogel. We discuss two mechanisms by which the mechanical response of the gel to the embedded chemical reactant provides feedback into the chemistry. These feedback mechanisms can be applied to control existing chemical oscillations as well as create new oscillations under some conditions. We analyze two model systems to demonstrate these two effects, respectively: a theoretical system that exhibits no excitability in the absence of a gel, and the Oregonator model of the Belousov-Zhabotinsky reaction in which the metal catalyst is intercalated into the polymer network. This work can aid in designing new materials that harness these feedbacks to create, control, and stabilize oscillatory and excitable chemical behavior in both oscillatory and non-oscillatory chemical networks.

  1. A New Optimal Control System Design for Chemical Processes

    Institute of Scientific and Technical Information of China (English)

    丛二丁; 胡明慧; 涂善东; 邵惠鹤

    2013-01-01

    Based on frequency response and convex optimization, a novel optimal control system was developed for chemical processes. The feedforward control is designed to improve the tracking performance of closed loop chemical systems. The parametric model is not required because the system directly utilizes the frequency response of the loop transfer function, which can be measured accurately. In particular, the extremal values of magnitude and phase can be solved according to constrained quadratic programming optimizer and convex optimization. Simula-tion examples show the effectiveness of the method. The design method is simple and easily adopted in chemical industry.

  2. Two-Pulse Atomic Coherent Control (2PACC) Spectroscopy of Eley-Rideal Reactions. An Application of an Atom Laser

    CERN Document Server

    Jorgensen, S F; Jorgensen, Solvejg; Kosloff, Ronnie

    2003-01-01

    A spectroscopic application of the atom laser is suggested. The spectroscopy termed 2PACC employs the coherent properties of matter-waves from a two pulse atom laser. These waves are employed to control a gas-surface chemical recombination reaction. The method is demonstrated for an Eley-Rideal reaction of a hydrogen or alkali atom-laser pulse where the surface target is an adsorbed hydrogen atom. The reaction yields either a hydrogen or alkali hydride molecule. The desorbed gas phase molecular yield and its internal state is shown to be controlled by the time and phase delay between two atom-laser pulses. The calculation is based on solving the time-dependent Schrodinger equation in a diabatic framework. The probability of desorption which is the predicted 2PACC signal has been calculated as a function of the pulse parameters.

  3. All-optical noninvasive chaos control of a semiconductor laser.

    Science.gov (United States)

    Schikora, S; Wünsche, H-J; Henneberger, F

    2008-08-01

    We demonstrate experimentally control of a chaotic system on time scales much shorter than in any previous study. Combining a multisection laser with an external Fabry-Perot etalon, the chaotic output transforms into a regular intensity self-pulsation with a frequency in the 10-GHz range. The control is noninvasive as the feedback from the etalon is minimum when the target state is reached. The optical phase is identified as a crucial control parameter. Numerical simulations agree well with the experimental data and uncover global control properties.

  4. III-Nitride nanowire lasers: fabrication and control of optical properties (Conference Presentation)

    Science.gov (United States)

    Wang, George T.

    2016-09-01

    III-nitride nanowires have attracted increasing interest as potential ultracompact and low-power nanoscale lasers in the UV-visible wavelengths. In order to maximize the potential of nanowire lasers, a greater understanding and control over their properties, including mode control, polarization control, wavelength tuning, and beam shaping, is necessary. Here, we discuss the fabrication of III-nitride based single nanowire and nanowire photonic crystal lasers using a top-down approach, and present multiple methods for controlling their optical properties. The nanowires were fabricated by a two-step process composed of a lithographic dry etch followed by a selective, wet chemical etch of the nanowire sidewalls. This technique allows for high quality nanowires with straight and smooth nonpolar m-plane sidewalls and with controllable height, pitch and diameter. Precisely engineered axial nanowire heterostructures can be formed from planar heterostructures, while radial nanowire heterostructures can be formed via regrowth on the etched nanowires. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. Department of Energy, Office of Basic Energy Sciences user facility. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  5. Plasma shape control by pulsed solenoid on laser ion source

    Energy Technology Data Exchange (ETDEWEB)

    Sekine, M. [Tokyo Institute of Technology, Meguro-ku, Tokyo 2-12-1 (Japan); RIKEN, Wako, Saitama 351-0198 (Japan); Ikeda, S. [Tokyo Institute of Technology, Yokohama, Kanagawa 226-8502 (Japan); RIKEN, Wako, Saitama 351-0198 (Japan); Romanelli, M. [Cornell University, Ithaca, NY 14850 (United States); Kumaki, M. [RIKEN, Wako, Saitama 351-0198 (Japan); Waseda University, Shinjuku, Tokyo 169-0072 (Japan); Fuwa, Y. [RIKEN, Wako, Saitama 351-0198 (Japan); Kyoto University, Uji, Kyoto 611-0011 (Japan); Kanesue, T. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Hayashizaki, N. [Tokyo Institute of Technology, Meguro-ku, Tokyo 2-12-1 (Japan); Lambiase, R. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Okamura, M. [RIKEN, Wako, Saitama 351-0198 (Japan); Brookhaven National Laboratory, Upton, NY 11973 (United States)

    2015-09-21

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  6. Plasma shape control by pulsed solenoid on laser ion source

    Science.gov (United States)

    Sekine, M.; Ikeda, S.; Romanelli, M.; Kumaki, M.; Fuwa, Y.; Kanesue, T.; Hayashizaki, N.; Lambiase, R.; Okamura, M.

    2015-09-01

    A Laser ion source (LIS) provides high current heavy ion beams with a very simple mechanical structure. Plasma is produced by a pulsed laser ablation of a solid state target and ions are extracted by an electric field. However, it was difficult to manipulate the beam parameters of a LIS, since the plasma condition could only be adjusted by the laser irradiation condition. To enhance flexibility of LIS operation, we employed a pulsed solenoid in the plasma drift section and investigated the effect of the solenoid field on singly charged iron beams. The experimentally obtained current profile was satisfactorily controlled by the pulsed magnetic field. This approach may also be useful to reduce beam emittance of a LIS.

  7. Feedback Control Of Dynamical Instabilities In Classical Lasers And Fels

    CERN Document Server

    Bielawski, S; Szwaj, C

    2005-01-01

    Dynamical instabilities lead to unwanted full-scale power oscillations in many classical lasers and FEL oscillators. For a long time, applications requiring stable operation were typically performed by working outside the problematic parameter regions. A breakthrough occurred in the nineties [1], when emphasis was made on the practical importance of unstable states (stationary or periodic) that coexist with unwanted oscillatory states. Indeed, although not observable in usual experiments, unstable states can be stabilized, using a feedback control involving arbitrarily small perturbations of a parameter. This observation stimulated a set of works leading to successful suppression of dynamical instabilities (initially chaos) in lasers, sometimes with surprisingly simple feedback devices [2]. We will review a set of key results, including in particular the recent works on the stabilization of mode-locked lasers, and of the super-ACO, ELETTRA and UVSOR FELs [3].

  8. Dynamic analysis and continuous control of semiconductor lasers

    CERN Document Server

    Behnia, Sohrab; Afrang, Saeid

    2011-01-01

    Stability control in laser is still an emerging field of research. In this paper the dynamics of External cavity semiconductor lasers (ECSLs) is widely studied applying the methods of chaos physics. The stability is analyzed through plotting the Lyapunov exponent spectra, bifurcation diagrams and time series. The oscillation of the electric field E has been reported to be either periodic (P1,P2,..) or chaotic. The results of the study show that the rich nonlinear dynamics of the electric field |E|^2 includes saddle node bifurcations, quasi-periodicity and regular pulse packages. The issue of finding the conditions for creating stable domains has been studied. By considering the dynamical pumping current system coupled with laser, a method for the creation of the stable domain has been introduced.

  9. Control of a resonant tunneling structure by intense laser fields

    Science.gov (United States)

    Aktas, S.; Kes, H.; Boz, F. K.; Okan, S. E.

    2016-10-01

    The intense laser field effects on a resonant tunneling structure were studied using computational methods. The considered structure was a GaAs/InxGa1-xAs/Al0.3Ga0.7As/InyGa1-yAs/AlAs/GaAs well-barrier system. In the presence of intense laser fields, the transmission coefficient and the dwell time of the structure were calculated depending on the depth and the width of InGaAs wells. It was shown that an intense laser field provides full control on the performance of the device as the geometrical restrictions on the resonant tunneling conditions overcome. Also, the choice of the resonant energy value becomes possible depending on the field strength.

  10. A pressure recovery system for chemical oxygen-iodine laser based on an active diffuser

    Science.gov (United States)

    Malkov, V. M.; Kiselev, I. A.; Orlov, A. E.; Shatalov, I. V.

    2011-09-01

    An open-type pressure recovery system (PRS) for chemical oxygen-iodine laser was designed and fabricated. As a first stage, an active diffuser was used in which the ejecting gas supply was organized through nozzles disposed around the channel periphery. The second stage was a supersonic ejector. Numerical simulation data for the viscous turbulent flow with heat release through the diffuser gas-dynamic channel, and also data obtained by testing the active diffuser in operation on a model facility equipped with a vacuum chamber, are reported. The obtained data were used to develop a full-scale setup with exhaust of laser gas into the atmosphere; this has allowed us to optimize the performance characteristics of the setup and substantially improve its mass-dimensional characteristics. Special attention was paid to parameter matching and synchronization of laser start with the operation of PRS components.

  11. A laser feedback control design for passive ring laser gyros in a very high finesse cavity

    Science.gov (United States)

    Lorenz, M. A.

    1985-12-01

    The Frank J. Seiler Research Laboratory is currently developing a Passive Resonant Ring Laser Gyroscope (PRRLG) enclosing 58 sq m for proposed use in testing high precision rate sensors and for possibly validating the Theory of General Relativity. The sensitivities required for such experiments are in the 10 to the minus 7th power to 10 to the minus 10th power Earth Rate Unit (ERU) range. This high sensitivity necessitates the use of a large, high finesse cavity. In dealing with high finesse cavities new considerations arise. For example, the cavity linewidth is narrower than linewidths of commercially available stabilized He-Ne lasers. The stability of the laser then becomes the limiting factor in the performance of the PRRLG because of the increased signal-to-noise ratio that arises in this situation. In addition, high finesse cavities exhibit photon lifetimes on the order of 10 to the minus 3rd power to 10 to the minus 6th power seconds, which limits the bandwidth of practical controllers. In this research, a PRRLG was constructed in which a He-Ne laser was frequency locked to 25,000 finesse, 169 sq. cm. resonant cavity, as opposed to the more traditional technique of locking the resonant condition of the cavity to the laser frequency.

  12. Dancing droplets: Chemical space, substrates, and control

    Science.gov (United States)

    Cira, Nate; Benusiglio, Adrien; Prakash, Manu

    2015-11-01

    Previously we showed that droplets of propylene glycol and water display remarkable properties when placed on clean glass due to an interplay between surface tension and evaporation. (Cira, Benusiglio, Prakash: Nature, 2015). We showed that these mechanisms apply to a range of two-component mixtures of miscible liquids where one component has both higher surface tension and higher vapor pressure on a variety of high energy surfaces. We now show how this rule can be cheated using a simple trick. We go on to demonstrate applications for cleaning, and show how this system works on substrates prepared only with sunlight. We finish by demonstrating active control of droplets, allowing access to a host of new possibilities.

  13. Influence of exothermic chemical reactions on laser-induced shock waves.

    Science.gov (United States)

    Gottfried, Jennifer L

    2014-10-21

    Differences in the excitation of non-energetic and energetic residues with a 900 mJ, 6 ns laser pulse (1064 nm) have been investigated. Emission from the laser-induced plasma of energetic materials (e.g. triaminotrinitrobenzene [TATB], cyclotrimethylene trinitramine [RDX], and hexanitrohexaazaisowurtzitane [CL-20]) is significantly reduced compared to non-energetic materials (e.g. sugar, melamine, and l-glutamine). Expansion of the resulting laser-induced shock wave into the air above the sample surface was imaged on a microsecond timescale with a high-speed camera recording multiple frames from each laser shot; the excitation of energetic materials produces larger heat-affected zones in the surrounding atmosphere (facilitating deflagration of particles ejected from the sample surface), results in the formation of additional shock fronts, and generates faster external shock front velocities (>750 m s(-1)) compared to non-energetic materials (550-600 m s(-1)). Non-explosive materials that undergo exothermic chemical reactions in air at high temperatures such as ammonium nitrate and magnesium sulfate produce shock velocities which exceed those of the inert materials but are less than those generated by the exothermic reactions of explosive materials (650-700 m s(-1)). The most powerful explosives produced the highest shock velocities. A comparison to several existing shock models demonstrated that no single model describes the shock propagation for both non-energetic and energetic materials. The influence of the exothermic chemical reactions initiated by the pulsed laser on the velocity of the laser-induced shock waves has thus been demonstrated for the first time.

  14. Controllable Dispersion in an Optical Laser Gyroscope

    Science.gov (United States)

    Wolfe, Owen; Du, Shuangli; Rochester, Simon; Budker, Dmitry; Novikova, Irina; Mikhailov, Eugeniy

    2016-05-01

    Optical gyroscopes use Sagnac interferometry to make precise measurements of angular velocity. Increased gyroscope sensitivity will allow for more accurate control of aerospace systems and allow for more precise measurements of the Earth's rotation. Severalfold improvements to optical gyroscope sensitivity were predicted for fast light regimes (ng gyroscope response via tuning the experimental parameters. Gyroscope sensitivity was shown to be dependent on several parameters including pump power, pump detunning, and vapor density. This work was supported by the NSF and Naval Air Warfare Center STTR program N68335-11-C-0428.

  15. CdS thin films prepared by laser assisted chemical bath deposition

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, L.V.; Mendivil, M.I.; Garcia Guillen, G.; Aguilar Martinez, J.A. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Krishnan, B. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); CIIDIT – Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Avellaneda, D.; Castillo, G.A.; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); Shaji, S., E-mail: sshajis@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, Av. Pedro de Alba s/n, Ciudad Universitaria, San Nicolas de los Garza, Nuevo Leon 66450 (Mexico); CIIDIT – Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

    2015-05-01

    Highlights: • CdS thin films by conventional CBD and laser assisted CBD. • Characterized these films using XRD, XPS, AFM, optical and electrical measurements. • Accelerated growth was observed in the laser assisted CBD process. • Improved dark conductivity and good photocurrent response for the LACBD CdS. - Abstract: In this work, we report the preparation and characterization of CdS thin films by laser assisted chemical bath deposition (LACBD). CdS thin films were prepared from a chemical bath containing cadmium chloride, triethanolamine, ammonium hydroxide and thiourea under various deposition conditions. The thin films were deposited by in situ irradiation of the bath using a continuous laser of wavelength 532 nm, varying the power density. The thin films obtained during deposition of 10, 20 and 30 min were analyzed. The changes in morphology, structure, composition, optical and electrical properties of the CdS thin films due to in situ irradiation of the bath were analyzed by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–vis spectroscopy. The thin films obtained by LACBD were nanocrystalline, photoconductive and presented interesting morphologies. The results showed that LACBD is an effective synthesis technique to obtain nanocrystalline CdS thin films having good optoelectronic properties.

  16. Nanosecond laser textured superhydrophobic metallic surfaces and their chemical sensing applications

    Science.gov (United States)

    Ta, Duong V.; Dunn, Andrew; Wasley, Thomas J.; Kay, Robert W.; Stringer, Jonathan; Smith, Patrick J.; Connaughton, Colm; Shephard, Jonathan D.

    2015-12-01

    This work demonstrates superhydrophobic behavior on nanosecond laser patterned copper and brass surfaces. Compared with ultrafast laser systems previously used for such texturing, infrared nanosecond fiber lasers offer a lower cost and more robust system combined with potentially much higher processing rates. The wettability of the textured surfaces develops from hydrophilicity to superhydrophobicity over time when exposed to ambient conditions. The change in the wetting property is attributed to the partial deoxidation of oxides on the surface induced during laser texturing. Textures exhibiting steady state contact angles of up to ∼152° with contact angle hysteresis of around 3-4° have been achieved. Interestingly, the superhydrobobic surfaces have the self-cleaning ability and have potential for chemical sensing applications. The principle of these novel chemical sensors is based on the change in contact angle with the concentration of methanol in a solution. To demonstrate the principle of operation of such a sensor, it is found that the contact angle of methanol solution on the superhydrophobic surfaces exponentially decays with increasing concentration. A significant reduction, of 128°, in contact angle on superhydrophobic brass is observed, which is one order of magnitude greater than that for the untreated surface (12°), when percent composition of methanol reaches to 28%.

  17. Chemical Control of Pennesetum Purpureum Laboratory Trials

    Directory of Open Access Journals (Sweden)

    B.N Tripathi

    1977-10-01

    Full Text Available Dichloral urea, diethyl chloracetamide, nitrourea, chloralhydrate, sodium trichloroacetate, sodium borate, ammonium thiocynate, sodium arsenite, arsenic oxide-sulphuric acid mixture, sodium chlorate, maleic hydrazide and the salts containing inorganic ions Cu/sup 2+/, Co/sup 2+/, MoO/sub 4//sup 2-/ and Zn/sup 2+/ were tested in experimental plots for their phytotoxic activity on a hybrid variety of Pennesetum purpureum. Sodium borate (2500 Kg/hectare, Sodium arsenite (250 Kg/hectare and sodium chlorate (1000 Kg/hectare through soil and ammonium thiocyanate (100 Kg/hectare through direct spray function as growth retardants. Arsenic oxide-sulphuric acid (100 : 300 Kg/hectare spray kills the existing leaves. Sodium chlorate (250 Kg/hectare spray exerts phytocidal action on young plants (3 weeks. Maleic hydrazide (50 Kg/hectare exerts permanent growth suppressant action on older plants (height >=1 m and kills the existing leaves of younger plants (height=<0.5 m. Copper sulphate (100 Kg/hectare induces partial drying of existing leaves and cobalt sulphate in the same dose induces yellowing of leaves extending the period of growth beyond the season of maximum growth of the control. Ammonium molybdate and Zinc acetate in the same dose do not exert any perceptible effect.

  18. Self-organizing microstructures orientation control in femtosecond laser patterning on silicon surface.

    Science.gov (United States)

    Liu, Pengjun; Jiang, Lan; Hu, Jie; Zhang, Shuai; Lu, Yongfeng

    2014-07-14

    Self-organizing rippled microstructures are induced on silicon surface by linearly polarized femtosecond laser pulses. At a near threshold fluence, it is observed that ripple orientation is co-determined by the laser polarization direction and laser scanning parameters (scanning direction and scanning speed) in surface patterning process. Under fixed laser polarization, the ripple orientation can be controlled to rotate by about 40° through changing laser scanning parameters. In addition, it is also observed that the ripple morphology is sensitive to the laser scanning direction, and it is an optimal choice to obtain ordered ripple structures when the angle between laser scanning and laser polarization is less than 45°.

  19. Environmental and chemical controls on palagonitization

    Science.gov (United States)

    Pauly, Bruce D.; Schiffman, Peter; Zierenberg, Robert A.; Clague, David A.

    2011-12-01

    Palagonitized sideromelane from submarine volcaniclastic, seafloor volcanic, marine phreatomagmatic, lacustine phreatomagmatic, and subglacial volcanic settings was investigated using in situ microanalysis to test if palagonite composition and texture are related to depositional environment. Palagonitization extent varies linearly and inversely with original sample porosity, suggesting that porosity is a controlling factor of palagonitization. Water absorbance of reflected infrared light varies linearly with water content derived from electron microprobe totals. Palagonite water content has a linear, inverse relationship to palagonitization extent. REEs are immobile during palagonitization, so they can be used to construct isocon diagrams for estimating major-element concentration changes. Major-element and overall mass changes during palagonitization vary widely (particularly for FeO and TiO2) and indicate that palagonitization cannot be an isovolumetric process. These parameters depend strongly on original sideromelane composition, thus requiring composition to be taken into account when performing global oceanic cation flux calculations. Subalkaline sideromelane dissolves much more rapidly than alkaline sideromelane during palagonitization. Two styles of palagonitization, burial-diagenesis (relatively long-duration, low water/rock; passive fluid circulation) and hydrothermal (relatively short-duration, high water/rock; hydrothermal fluid circulation), are recognized. Observed palagonite REE concentration gradients indicate that sideromelane dissolution must continue in the zone behind the advancing palagonitization front. MgO was found to be highly mobile during palagonitization. Observed palagonite MgO gradients are not developed during sideromelane dissolution, but instead record initiation of syn- and/or post-palagonitization conversion of the gel-palagonite layer to a phyllosillicate layer, consistent with evolution of sideromelane alteration layers toward

  20. Laser-based standoff detection of surface-bound explosive chemicals

    Science.gov (United States)

    Huestis, David L.; Smith, Gregory P.; Oser, Harald

    2010-04-01

    Avoiding or minimizing potential damage from improvised explosive devices (IEDs) such as suicide, roadside, or vehicle bombs requires that the explosive device be detected and neutralized outside its effective blast radius. Only a few seconds may be available to both identify the device as hazardous and implement a response. As discussed in a study by the National Research Council, current technology is still far from capable of meeting these objectives. Conventional nitrocarbon explosive chemicals have very low vapor pressures, and any vapors are easily dispersed in air. Many pointdetection approaches rely on collecting trace solid residues from dust particles or surfaces. Practical approaches for standoff detection are yet to be developed. For the past 5 years, SRI International has been working toward development of a novel scheme for standoff detection of explosive chemicals that uses infrared (IR) laser evaporation of surfacebound explosive followed by ultraviolet (UV) laser photofragmentation of the explosive chemical vapor, and then UV laser-induced fluorescence (LIF) of nitric oxide. This method offers the potential of long standoff range (up to 100 m or more), high sensitivity (vaporized solid), simplicity (no spectrometer or library of reference spectra), and selectivity (only nitrocompounds).

  1. Control system for high power laser drilling workover and completion unit

    Energy Technology Data Exchange (ETDEWEB)

    Zediker, Mark S; Makki, Siamak; Faircloth, Brian O; DeWitt, Ronald A; Allen, Erik C; Underwood, Lance D

    2015-05-12

    A control and monitoring system controls and monitors a high power laser system for performing high power laser operations. The control and monitoring system is configured to perform high power laser operation on, and in, remote and difficult to access locations.

  2. Photothermal laser fabrication of micro- and nanostructured chemical templates for directed protein immobilization.

    Science.gov (United States)

    Schröter, Anja; Franzka, Steffen; Hartmann, Nils

    2014-12-16

    Photothermal patterning of poly(ethylene glycol) terminated organic monolayers on surface-oxidized silicon substrates is carried out using a microfocused beam of a CW laser operated at a wavelength of 532 nm. Trichlorosilane and trimethoxysilane precursors are used for coating. Monolayers from trimethoxysilane precursors show negligible unspecific protein adsorption in the background, i.e., provide platforms of superior protein repellency. Laser patterning results in decomposition of the monolayers and yields chemical templates for directed immobilization of proteins at predefined positions. Characterization is carried out via complementary analytical methods including fluorescence microscopy, atomic force microscopy, and scanning electron microscopy. Appropriate labeling techniques (fluorescent markers and gold clusters) and substrates (native and thermally oxidized silicon substrates) are chosen in order to facilitate identification of protein adsorption and ensure high sensitivity and selectivity. Variation of the laser parameters at a 1/e(2) spot diameter of 2.8 μm allows for fabrication of protein binding domains with diameters on the micrometer and nanometer length scale. Minimum domain sizes are about 300 nm. In addition to unspecific protein adsorption on as-patterned monolayers, biotin-streptavidin coupling chemistry is exploited for specific protein binding. This approach represents a novel facile laser-based means for fabrication of protein micro- and nanopatterns. The routine is readily applicable to femtosecond laser processing of glass substrates for the fabrication of transparent templates.

  3. Molecular Alignment and Orientation From Laser-Induced Mechanisms to Optimal Control

    CERN Document Server

    Atabek, O

    2002-01-01

    Genetic algorithms, as implemented in optimal control strategies, are currently successfully exploited in a wide range of problems in molecular physics. In this context, laser control of molecular alignment and orientation remains a very promising issue with challenging applications extending from chemical reactivity to nanoscale design. We emphasize the complementarity between basic quantum mechanisms monitoring alignment/orientation processes and optimal control scenarios. More explicitly, if on one hand we can help the optimal control scheme to take advantage of such mechanisms by appropriately building the targets and delineating the parameter sampling space, on the other hand we expect to learn, from optimal control results, some robust and physically sound dynamical mechanisms. We present basic mechanisms for alignment and orientation, such as pendular states accommodated by the molecule-plus-field effective potential and the "kick" mechanism obtained by a sudden excitation. Very interestingly, an optim...

  4. Chemical decomposition of urinary stones during holmium-laser lithotripsy: II. Evidence for photothermal breakdown

    Science.gov (United States)

    Glickman, Randolph D.; Teichman, Joel M. H.; Vassar, George J.; Weintraub, Susan T.; Chan, Kin Foong; Pfefer, T. Joshua; Welch, Ashley J.

    1999-06-01

    Because of the greater than or equal to 250 microsecond pulsewidth emitted by the Ho:YAG laser used in clinical lithotripsy, it is unlikely that stress confinement occurs within the irradiated stones. Experimental data supports a thermal mechanism for Ho:YAG laser stone ablation. Stone fragmentation occurs soon after the onset of the laser pulse, is uncorrelated to cavitation bubble formation or collapse, and is associated with low pressures (cf. part I). The mass- loss of desiccated calcium oxalate monohydrate (COM) stones exposed to 150 J from the Ho:YAG laser in air was 40 plus or minus 12 mg (mean plus or minus 1 s.d.); for hydrated stones in air was 25 plus or minus 9 mg; and for hydrated stones in water was 17 plus or minus 3 mg, p less than .001. These differences indicate that direct absorption of the laser radiation by the stone is required for the most efficient ablation. Lowering the initial temperature of COM or cystine stones also reduced the stone mass-loss following 20 J of delivered laser energy: 2.2 plus or minus 1.1 mg vs 5.2 plus or minus 1.6 mg for COM stones (-80 vs 23 degrees Celsius), and 0.8 plus or minus 0.4 mg vs 2.2 plus or minus 1.1 mg for cystine stones (-80 vs 23 degrees Celsius), p less than or equal to .05. Finally, chemical analysis of the laser-induced stone fragments revealed the presence of thermal breakdown products: CaCO3 from COM; free sulfur and cysteine from cystine; Ca2O7P2 from calcium hydorgen phosphate dihydrate, and cyanide from uric acid.

  5. Visually Guiding and Controlling the Search While Mining Chemical Structures

    OpenAIRE

    Max Pereira; Vitor Santos Costa; Rui Camacho; Fonseca, Nuno A.

    2009-01-01

    In this paper we present the work in progress on LogCHEM, an ILP based tool for discriminative interactive mining of chemical fragments. In particular, we describe the integration with a molecule visualisation software that allows the chemist to graphically control the search for interesting patterns in chemical fragments. Furthermore, we show how structured information, such as rings, functional groups like carboxyl, amine, methyl, ester, etc are integrated and exploited in LogCHEM.

  6. Pump-Controlled Modal Interactions in Microdisk Lasers

    CERN Document Server

    Liew, Seng Fatt; Redding, Brandon; Solomon, Glenn S; Cao, Hui

    2014-01-01

    We demonstrate an effective control of nonlinear interactions of lasing modes in a semiconductor microdisk cavity by shaping the pump profile. A target mode is selected at the expense of its competing modes either by increasing their lasing thresholds or suppressing their power slopes above the lasing threshold. Despite of strong spatial overlap of the lasing modes at the disk boundary, adaptive pumping enables an efficient selection of any lasing mode to be the dominant one, leading to a switch of lasing frequency. The theoretical analysis illustrates both linear and nonlinear effects of selective pumping, and quantify their contributions to lasing mode selection. This work shows that adaptive pumping not only provides a powerful tool of controlling the nonlinear process in multimode lasers, but also enables the tuning of lasing characteristic after the lasers have been fabricated.

  7. Controlling synchronization in large laser networks using number theory

    CERN Document Server

    Nixon, Micha; Ronen, Eitan; Friesem, Asher A; Davidson, Nir; Kanter, Ido

    2011-01-01

    Synchronization in networks with delayed coupling are ubiquitous in nature and play a key role in almost all fields of science including physics, biology, ecology, climatology and sociology. In general, the published works on network synchronization are based on data analysis and simulations, with little experimental verification. Here we develop and experimentally demonstrate various multi-cluster phase synchronization scenarios within coupled laser networks. Synchronization is controlled by the network connectivity in accordance to number theory, whereby the number of synchronized clusters equals the greatest common divisor of network loops. This dependence enables remote switching mechanisms to control the optical phase coherence among distant lasers by local network connectivity adjustments. Our results serve as a benchmark for a broad range of coupled oscillators in science and technology, and offer feasible routes to achieve multi-user secure protocols in communication networks and parallel distribution...

  8. Nanometer thickness laser ablation for spatial control of cell attachment

    Science.gov (United States)

    Thissen, H.; Hayes, J. P.; Kingshott, P.; Johnson, G.; Harvey, E. C.; Griesser, H. J.

    2002-10-01

    We demonstrate here a new method to control the location of cells on surfaces in two dimensions, which can be applied to a number of biomedical applications including diagnostic tests and tissue engineered medical devices. Two-dimensional control over cell attachment is achieved by generation of a spatially controlled surface chemistry that allows control over protein adsorption, a process which mediates cell attachment. Here, we describe the deposition of thin allylamine plasma polymer coatings on silicon wafer and perfluorinated poly(ethylene-co-propylene) substrates, followed by grafting of a protein resistant layer of poly(ethylene oxide). Spatially controlled patterning of the surface chemistry was achieved in a fast, one-step procedure by nanometer thickness controlled laser ablation using a 248 nm excimer laser. X-ray photoelectron spectroscopy and atomic force microscopy were used to confirm the production of surface chemistry patterns with a resolution of approximately 1 µm, which is significantly below the dimensions of a single mammalian cell. Subsequent adsorption of the extracellular matrix proteins collagen I and fibronectin followed by cell culture experiments using bovine corneal epithelial cells confirmed that cell attachment is controlled by the surface chemistry pattern. The method is an effective tool for use in a number of in vitro and in vivo applications.

  9. Optomechatronics Design and Control for Confocal Laser Scanning Microscopy

    OpenAIRE

    Yoo, H W

    2015-01-01

    Confocal laser scanning microscopy (CLSM) is considered as one of the major advancements in microscopy in the last century and is widely accepted as a 3D fluorescence imaging tool for biological studies. For the emerging biological questions CLSM requires fast imaging to detect rapid biological processes and aberration-corrected imaging to localize the targeted biomolecule precisely through optical disturbances by specimen. In this thesis, optomechatronics design and control are discussed for...

  10. Active subnanometer spectral control of a random laser

    CERN Document Server

    Leonetti, Marco; 10.1063/1.4792759

    2013-01-01

    We demonstrate an experimental technique that allows to achieve a robust control on the emission spectrum of a micro random laser and to select individual modes with sub-nanometer resolution. The presented approach relies on an optimization protocol of the spatial profile of the pump beam. Here we demonstrate not only the possibility to increase the emission at a wavelength, but also that we can isolate an individual peak suppressing unwanted contributions form other modes.

  11. Rapid laser-free ion cooling by controlled collision

    CERN Document Server

    Lau, Hoi-Kwan

    2012-01-01

    I propose a method to transfer the axial motional excitation of a hot ion to a coolant ion with possibly different mass by precisely controlling the ion separation and the local trapping potentials during ion collision. The whole cooling process can be conducted diabatically, involving only a few oscillation periods of the harmonic trap. With sufficient coolant ions pre-prepared, this method can rapidly re-cool ion qubits in quantum information processing without applying lengthy laser cooling.

  12. Development of a new laser heating system for thin film growth by chemical vapor deposition.

    Science.gov (United States)

    Fujimoto, Eiji; Sumiya, Masatomo; Ohnishi, Tsuyoshi; Lippmaa, Mikk; Takeguchi, Masaki; Koinuma, Hideomi; Matsumoto, Yuji

    2012-09-01

    We have developed a new laser heating system for thin film growth by chemical vapor deposition (CVD). A collimated beam from a high-power continuous-wave 808 nm semiconductor laser was directly introduced into a CVD growth chamber without an optical fiber. The light path of the heating laser inside the chamber was isolated mechanically from the growth area by bellows to protect the optics from film coating. Three types of heat absorbers, (10 × 10 × 2 mm(3)) consisting of SiC, Ni/NiO(x), or pyrolytic graphite covered with pyrolytic BN (PG/PBN), located at the backside of the substrate, were tested for heating performance. It was confirmed that the substrate temperature could reach higher than 1500 °C in vacuum when a PG/PBN absorber was used. A wide-range temperature response between 400 °C and 1000 °C was achieved at high heating and cooling rates. Although the thermal energy loss increased in a H(2) gas ambient due to the higher thermal conductivity, temperatures up to 1000 °C were achieved even in 200 Torr H(2). We have demonstrated the capabilities of this laser heating system by growing ZnO films by metalorganic chemical vapor deposition. The growth mode of ZnO films was changed from columnar to lateral growth by repeated temperature modulation in this laser heating system, and consequently atomically smooth epitaxial ZnO films were successfully grown on an a-plane sapphire substrate.

  13. An embedded laser marking controller based on ARM and FPGA processors.

    Science.gov (United States)

    Dongyun, Wang; Xinpiao, Ye

    2014-01-01

    Laser marking is an important branch of the laser information processing technology. The existing laser marking machine based on PC and WINDOWS operating system, are large and inconvenient to move. Still, it cannot work outdoors or in other harsh environments. In order to compensate for the above mentioned disadvantages, this paper proposed an embedded laser marking controller based on ARM and FPGA processors. Based on the principle of laser galvanometer scanning marking, the hardware and software were designed for the application. Experiments showed that this new embedded laser marking controller controls the galvanometers synchronously and could achieve precise marking.

  14. An Embedded Laser Marking Controller Based on ARM and FPGA Processors

    Directory of Open Access Journals (Sweden)

    Wang Dongyun

    2014-01-01

    Full Text Available Laser marking is an important branch of the laser information processing technology. The existing laser marking machine based on PC and WINDOWS operating system, are large and inconvenient to move. Still, it cannot work outdoors or in other harsh environments. In order to compensate for the above mentioned disadvantages, this paper proposed an embedded laser marking controller based on ARM and FPGA processors. Based on the principle of laser galvanometer scanning marking, the hardware and software were designed for the application. Experiments showed that this new embedded laser marking controller controls the galvanometers synchronously and could achieve precise marking.

  15. Photo-vibrational spectroscopy of solid and liquid chemicals using laser Doppler vibrometer.

    Science.gov (United States)

    Hu, Qi; Lim, Jacob Song Kiat; Liu, Huan; Fu, Yu

    2016-08-22

    Photoacoustic/photothermal spectroscopy is an established technique for trace detection of chemicals and explosives. However, prior sample preparation is required and the analysis is conducted in a sealed space with a high-sensitivity microphone or a piezo sensor coupled with a lock-in amplifier, limiting the technique to applications in a laboratory environment. Due to the aforementioned requirements, traditionally this technique may not be suitable for defense and security applications where the detection of explosives or hazardous chemicals is required in an open environment at a safe standoff distance. In this study, chemicals in various forms (membrane, powder and liquid) were excited by an intensity-modulated quantum cascade laser (QCL), while a laser Doppler vibrometer (LDV) based on the Mach-Zehnder interferometer was applied to detect the vibration signal resulting from the photocoustic/photothermal effect. The photo-vibrational spectrum obtained by scanning the QCL's wavelength in MIR range, coincides well with the corresponding spectrum obtained using typical FTIR equipment. The experiment demonstrated that the LDV is a capable sensor for applications in photoacoustic/photothermal spectroscopy, with potential to enable the detection of chemicals in open environment at safe standoff distance.

  16. Process Control Systems in the Chemical Industry: Safety vs. Security

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey Hahn; Thomas Anderson

    2005-04-01

    Traditionally, the primary focus of the chemical industry has been safety and productivity. However, recent threats to our nation’s critical infrastructure have prompted a tightening of security measures across many different industry sectors. Reducing vulnerabilities of control systems against physical and cyber attack is necessary to ensure the safety, security and effective functioning of these systems. The U.S. Department of Homeland Security has developed a strategy to secure these vulnerabilities. Crucial to this strategy is the Control Systems Security and Test Center (CSSTC) established to test and analyze control systems equipment. In addition, the CSSTC promotes a proactive, collaborative approach to increase industry's awareness of standards, products and processes that can enhance the security of control systems. This paper outlines measures that can be taken to enhance the cybersecurity of process control systems in the chemical sector.

  17. Laser control of molecular excitations in stochastic dissipative media.

    Science.gov (United States)

    Tremblay, Jean Christophe

    2011-05-07

    In the present work, ideas for controlling photochemical reactions in dissipative environments using shaped laser pulses are presented. New time-local control algorithms for the stochastic Schrödinger equation are introduced and compared to their reduced density matrix analog. The numerical schemes rely on time-dependent targets for guiding the reaction along a preferred path. The methods are tested on the vibrational control of adsorbates at metallic surfaces and on the ultrafast electron dynamics in a strong dissipative medium. The selective excitation of the specific states is achieved with improved yield when using the new algorithms. Both methods exhibit similar convergence behavior and results compare well with those obtained using local optimal control for the reduced density matrix. The favorable scaling of the methods allows to tackle larger systems and to control photochemical reactions in dissipative media of molecules with many more degrees of freedom.

  18. Laser vision based adaptive fill control system for TIG welding

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The variation of joint groove size during tungsten inert gas (TIG) welding will result in the non-uniform fill of deposited metal. To solve this problem, an adaptive fill control system was developed based on laser vision sensing. The system hardware consists of a modular development kit (MDK) as the real-time image capturing system, a computer as the controller, a D/A conversion card as the interface of controlled variable output, and a DC TIG welding system as the controlled device. The system software is developed and the developed feature extraction algorithm and control strategy are of good accuracy and robustness. Experimental results show that the system can implement adaptive fill of melting metal with high stability, reliability and accuracy. The groove is filled well and the quality of the weld formation satisfies the relevant industry criteria.

  19. Comparison of H-infinity control and generalized predictive control for a laser scanner system

    DEFF Research Database (Denmark)

    Ordys, A.W.; Stoustrup, Jakob; Smillie, I.

    2000-01-01

    This paper describes tests performed on a laser scanner system to assess the feasibility of H-infinity control and generalized predictive control design techniques in achieving a required performance in a trajectory folowing problem. The two methods are compared with respect to achieved scan times...

  20. Method for controlling a laser additive process using intrinsic illumination

    Science.gov (United States)

    Tait, Robert; Cai, Guoshuang; Azer, Magdi; Chen, Xiaobin; Liu, Yong; Harding, Kevin

    2015-05-01

    One form of additive manufacturing is to use a laser to generate a melt pool from powdered metal that is sprayed from a nozzle. The laser net-shape machining system builds the part a layer at a time by following a predetermined path. However, because the path may need to take many turns, maintaining a constant melt pool may not be easy. A straight section may require one speed and power while a sharp bend would over melt the metal at the same settings. This paper describes a process monitoring method that uses the intrinsic IR radiation from the melt pool along with a process model configured to establish target values for the parameters associated with the manufacture or repair. This model is based upon known properties of the metal being used as well as the properties of the laser beam. An adaptive control technique is then employed to control process parameters of the machining system based upon the real-time weld pool measurement. Since the system uses the heat radiant from the melt pool, other previously deposited metal does not confuse the system as only the melted material is seen by the camera.

  1. Tunable Diode Laser Sensor for Monitoring and Control of Harsh Combustion Environments

    Energy Technology Data Exchange (ETDEWEB)

    VonDrasek, William; Melsio-Pubill, Anna

    2006-05-30

    This work represents the collaborative effort between American Air Liquide and Physical Sciences, Inc. for developing a sensor based on near-IR tunable diode lasers (TDL). The multi-species capability of the sensor for simultaneous monitoring of CO, O2, and H2O concentration as well as gas temperature is ideal for in-situ monitoring on industrial furnaces. The chemical species targeted are fundamental for controlling the combustion space for improved energy efficiency, reduced pollutants, and improved product quality, when coupling the measurement to a combustion control system. Several add-on modules developed provide flexibility in the system configuration for handling different process monitoring applications. For example, the on-Demand Power Control system for the 1.5 ?m laser is used for high particle density exhaust streams where laser transmission is problematic. For long-distance signal collection a fiber optic communication system is used to reduce noise pick-up. Finally, hardened modules to withstand high ambient temperatures, immune to EMF interference, protection from flying debris, and interfaced with pathlength control laser beam shielding probes were developed specifically for EAF process monitoring. Demonstration of these different system configurations was conducted on Charter Steel's reheat furnace, Imco Recycling, Inc. (now Aleris International, Inc.) aluminum reverberatory furnace, and Gerdau Ameristeel's EAF. Measurements on the reheat furnace demonstrated zone monitoring with the measurement performed close to the steel billet. Results from the aluminum furnace showed the benefit of measuring in-situ near the bath. In this case, low-level furnace optimization was performed and demonstrated 5% fuel savings. Monitoring tests on the EAF off-gas demonstrated the level of industrialization of the sensor to survive the harsh EAF environment. Long-term testing on the EAF has been on-going for over 6 months with essentially zero maintenance

  2. Controlled Chemical Doping of Semiconductor Nanocrystals Using Redox Buffers

    Energy Technology Data Exchange (ETDEWEB)

    Engel, Jesse H. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Surendranath, Yogesh [Univ. of California, Berkeley, CA (United States); Alivisatos, Paul [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2013-07-20

    Semiconductor nanocrystal solids are attractive materials for active layers in next-generation optoelectronic devices; however, their efficient implementation has been impeded by the lack of precise control over dopant concentrations. Herein we demonstrate a chemical strategy for the controlled doping of nanocrystal solids under equilibrium conditions. Exposing lead selenide nanocrystal thin films to solutions containing varying proportions of decamethylferrocene and decamethylferrocenium incrementally and reversibly increased the carrier concentration in the solid by 2 orders of magnitude from their native values. This application of redox buffers for controlled doping provides a new method for the precise control of the majority carrier concentration in porous semiconductor thin films.

  3. Feedback-controlled laser fabrication of micromirror substrates.

    Science.gov (United States)

    Petrak, Benjamin; Konthasinghe, Kumarasiri; Perez, Sonia; Muller, Andreas

    2011-12-01

    Short (40-200 μs) single focused CO(2) laser pulses of energy ≳100 μJ were used to fabricate high quality concave micromirror templates on silica and fluoride glass. The ablated features have diameters of ≈20-100 μm and average root-mean-square (RMS) surface microroughness near their center of less than 0.2 nm. Temporally monitoring the fabrication process revealed that it proceeds on a time scale shorter than the laser pulse duration. We implement a fast feedback control loop (≈20 kHz bandwidth) based on the light emitted by the sample that ensures an RMS size dispersion of less than 5% in arrays on chips or in individually fabricated features on an optical fiber tip, a significant improvement over previous approaches using longer pulses and open loop operation.

  4. Adhesion of fibroblasts on micro- and nanostructured surfaces prepared by chemical vapor deposition and pulsed laser treatment

    Energy Technology Data Exchange (ETDEWEB)

    Veith, M; Aktas, O C; Ullah Wazir, H; Grobelsek, I [INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbruecken (Germany); Metzger, W; Sossong, D; Pohlemann, T; Oberringer, M [Department of Trauma-, Hand- and Reconstructive Surgery, Saarland University, Kirrberger Strasse, Building 57, 66421 Homburg (Germany); Puetz, N; Wennemuth, G, E-mail: Michael.Veith@inm-gmbh.d [Department of Anatomy and Cell Biology, Saarland University, Kirrberger Strasse, Building 61, 66421 Homburg (Germany)

    2010-09-15

    The development of micro- and nanostructured surfaces which improve the cell-substrate interaction is of great interest in today's implant applications. In this regard, Al/Al{sub 2}O{sub 3} bi-phasic nanowires were synthesized by chemical vapor deposition of the molecular precursor ({sup t}BuOAlH{sub 2}){sub 2}. Heat treatment of such bi-phasic nanowires with short laser pulses leads to micro- and nanostructured Al{sub 2}O{sub 3} surfaces. Such surfaces were characterized by scanning electron microscopy (SEM), electron dispersive spectroscopy and x-ray photoelectron spectroscopy. Following the detailed material characterization, the prepared surfaces were tested for their cell compatibility using normal human dermal fibroblasts. While the cells cultivated on Al/Al{sub 2}O{sub 3} bi-phasic nanowires showed an unusual morphology, cells cultivated on nanowires treated with one and two laser pulses exhibited morphologies similar to those observed on the control substrate. The highest cell density was observed on surfaces treated with one laser pulse. The interaction of the cells with the nano- and microstructures was investigated by SEM analysis in detail. Laser treatment of Al/Al{sub 2}O{sub 3} bi-phasic nanowires is a fast and easy method to fabricate nano- and microstructured Al{sub 2}O{sub 3}-surfaces for studying cell-surface interactions. It is our goal to develop a biocompatible Al{sub 2}O{sub 3}-surface which could be used as a coating material for medical implants exhibiting a cell selective response because of its specific physical landscape and especially because it promotes the adhesion of osteoblasts while minimizing the adhesion of fibroblasts.

  5. Chemical and ecological control methods for Epitrix spp.

    OpenAIRE

    A. G. S. Cuthbertson

    2015-01-01

    Very little information exists in regards to the control options available for potato flea beetles, Epitrix spp. This short review covers both chemical and ecological options currently available for control of Epitrix spp. Synthetic pyrethroids are the weapon of choice for the beetles. However, the impetus in integrated pest management is to do timely (early-season) applications with something harsh which will give long-term protection at a time when there are not a lot of beneficials in the ...

  6. Control electronics for a multi-laser/multi-detector scanning system

    Science.gov (United States)

    Kennedy, W.

    1980-01-01

    The Mars Rover Laser Scanning system uses a precision laser pointing mechanism, a photodetector array, and the concept of triangulation to perform three dimensional scene analysis. The system is used for real time terrain sensing and vision. The Multi-Laser/Multi-Detector laser scanning system is controlled by a digital device called the ML/MD controller. A next generation laser scanning system, based on the Level 2 controller, is microprocessor based. The new controller capabilities far exceed those of the ML/MD device. The first draft circuit details and general software structure are presented.

  7. Sign control of magnetoresistance through chemically engineered interfaces.

    Science.gov (United States)

    Ciudad, David; Gobbi, Marco; Kinane, Christy J; Eich, Marius; Moodera, Jagadeesh S; Hueso, Luis E

    2014-12-01

    Chemically engineered interfaces are shown to produce inversions of the magnetoresistance in spintronic devices including lithium fluoride interlayers. This behavior is explained by the formation of anti-ferromagnetic difluoride layers. By changing the order of deposition of the different materials, the sign of the magnetoresistance can be deterministically controlled both in organic spin valves and in inorganic magnetic tunnel junctions.

  8. Methylene Diphosphonate Chemical and Biological control of MDP complex

    CERN Document Server

    Aungurarat, A

    2000-01-01

    Technetium-9 sup 9 sup m MDP easy prepared from MDP kits which different sources such as OAP (In house), SIGMA. The resulting Tc 9 sup 9 sup m -MDP preparations were controlled in chemical and biological tests to compare the different results in these cases: radiochemical purity, the quantity of starting material and biodistribution result.

  9. Model Based Monitoring and Control of Chemical and Biochemical Processes

    DEFF Research Database (Denmark)

    Huusom, Jakob Kjøbsted

    This presentation will give an overview of the work performed at the department of Chemical and Biochemical Engineering related to process control. A research vision is formulated and related to a number of active projects at the department. In more detail a project describing model estimation...

  10. MIMO Self-Tuning Control of Chemical Process Operation

    DEFF Research Database (Denmark)

    Hallager, L.; Jørgensen, S. B.; Goldschmidt, L.

    1984-01-01

    The problem of selecting a feasible model structure for a MIMO self-tuning controller (MIMOSC) is addressed. The dependency of the necessary structure complexity in relation to the specific process operating point is investigated. Experimental results from a fixed-bed chemical reactor are used...

  11. Thermal Performance of ATLAS Laser Thermal Control System Demonstration Unit

    Science.gov (United States)

    Ku, Jentung; Robinson, Franklin; Patel, Deepak; Ottenstein, Laura

    2013-01-01

    The second Ice, Cloud, and Land Elevation Satellite mission currently planned by National Aeronautics and Space Administration will measure global ice topography and canopy height using the Advanced Topographic Laser Altimeter System {ATLAS). The ATLAS comprises two lasers; but only one will be used at a time. Each laser will generate between 125 watts and 250 watts of heat, and each laser has its own optimal operating temperature that must be maintained within plus or minus 1 degree Centigrade accuracy by the Laser Thermal Control System (LTCS) consisting of a constant conductance heat pipe (CCHP), a loop heat pipe (LHP) and a radiator. The heat generated by the laser is acquired by the CCHP and transferred to the LHP, which delivers the heat to the radiator for ultimate rejection. The radiator can be exposed to temperatures between minus 71 degrees Centigrade and minus 93 degrees Centigrade. The two lasers can have different operating temperatures varying between plus 15 degrees Centigrade and plus 30 degrees Centigrade, and their operating temperatures are not known while the LTCS is being designed and built. Major challenges of the LTCS include: 1) A single thermal control system must maintain the ATLAS at 15 degrees Centigrade with 250 watts heat load and minus 71 degrees Centigrade radiator sink temperature, and maintain the ATLAS at plus 30 degrees Centigrade with 125 watts heat load and minus 93 degrees Centigrade radiator sink temperature. Furthermore, the LTCS must be qualification tested to maintain the ATLAS between plus 10 degrees Centigrade and plus 35 degrees Centigrade. 2) The LTCS must be shut down to ensure that the ATLAS can be maintained above its lowest desirable temperature of minus 2 degrees Centigrade during the survival mode. No software control algorithm for LTCS can be activated during survival and only thermostats can be used. 3) The radiator must be kept above minus 65 degrees Centigrade to prevent ammonia from freezing using no more

  12. Control and optimization of a staged laser-wakefield accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Golovin, G.; Banerjee, S.; Chen, S.; Powers, N.; Liu, C.; Yan, W.; Zhang, J.; Zhang, P.; Zhao, B.; Umstadter, D., E-mail: donald.umstadter@unl.edu

    2016-09-11

    We report results of an experimental study of laser-wakefield acceleration of electrons, using a staged device based on a double-jet gas target that enables independent injection and acceleration stages. This novel scheme is shown to produce stable, quasi-monoenergetic, and tunable electron beams. We show that optimal accelerator performance is achieved by systematic variation of five critical parameters. For the injection stage, we show that the amount of trapped charge is controlled by the gas density, composition, and laser power. For the acceleration stage, the gas density and the length of the jet are found to determine the final electron energy. This independent control over both the injection and acceleration processes enabled independent control over the charge and energy of the accelerated electron beam while preserving the quasi-monoenergetic character of the beam. We show that the charge and energy can be varied in the ranges of 2–45 pC, and 50–450 MeV, respectively. This robust and versatile electron accelerator will find application in the generation of high-brightness and controllable x-rays, and as the injector stage for more conventional devices.

  13. Control and optimization of a staged laser-wakefield accelerator

    Science.gov (United States)

    Golovin, G.; Banerjee, S.; Chen, S.; Powers, N.; Liu, C.; Yan, W.; Zhang, J.; Zhang, P.; Zhao, B.; Umstadter, D.

    2016-09-01

    We report results of an experimental study of laser-wakefield acceleration of electrons, using a staged device based on a double-jet gas target that enables independent injection and acceleration stages. This novel scheme is shown to produce stable, quasi-monoenergetic, and tunable electron beams. We show that optimal accelerator performance is achieved by systematic variation of five critical parameters. For the injection stage, we show that the amount of trapped charge is controlled by the gas density, composition, and laser power. For the acceleration stage, the gas density and the length of the jet are found to determine the final electron energy. This independent control over both the injection and acceleration processes enabled independent control over the charge and energy of the accelerated electron beam while preserving the quasi-monoenergetic character of the beam. We show that the charge and energy can be varied in the ranges of 2-45 pC, and 50-450 MeV, respectively. This robust and versatile electron accelerator will find application in the generation of high-brightness and controllable x-rays, and as the injector stage for more conventional devices.

  14. Defect control in room temperature deposited cadmium sulfide thin films by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Como, N. [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, TX, 75080 (United States); Martinez-Landeros, V. [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, TX, 75080 (United States); Centro de Investigación en Materiales Avanzados, Monterrey, Nuevo Leon, 66600, México (Mexico); Mejia, I. [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, TX, 75080 (United States); Aguirre-Tostado, F.S. [Centro de Investigación en Materiales Avanzados, Monterrey, Nuevo Leon, 66600, México (Mexico); Nascimento, C.D.; Azevedo, G. de M; Krug, C. [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, 91509-900 (Brazil); Quevedo-Lopez, M.A., E-mail: mquevedo@utdallas.edu [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, TX, 75080 (United States)

    2014-01-01

    The control of defects in cadmium sulfide thin films and its impact on the resulting CdS optical and electrical characteristics are studied. Sulfur vacancies and cadmium interstitial concentrations in the CdS films are controlled using the ambient pressure during pulsed laser deposition. CdS film resistivities ranging from 10{sup −1} to 10{sup 4} Ω-cm are achieved. Hall Effect measurements show that the carrier concentration ranges from 10{sup 19} to 10{sup 13} cm{sup −3} and is responsible for the observed resistivity variation. Hall mobility varies from 2 to 12 cm{sup 2}/V-s for the same pressure regime. Although the energy bandgap remains unaffected (∼ 2.42 eV), the optical transmittance is reduced due to the increase of defects in the CdS films. Rutherford back scattering spectroscopy shows the dependence of the CdS films stoichiometry with deposition pressure. The presence of CdS defects is attributed to more energetic species reaching the substrate, inducing surface damage in the CdS films during pulsed laser deposition. - Highlights: • CdS thin films deposited by pulsed laser deposition at room temperature. • The optical, electrical and structural properties were evaluated. • Carrier concentration ranged from 10{sup 19} to 10{sup 13} cm{sup −3}. • The chemical composition was studied by Rutherford back scattering. • The density of sulfur vacancies and cadmium interstitial was varied.

  15. Adaptive control of lasers and their interactions with matter using femtosecond pulse shaping

    Science.gov (United States)

    Efimov, Anatoly

    Coherent control of chemical reactions, atomic and molecular systems, lattice dynamics, and electronic motion rely on femtosecond laser sources capable of producing programmable arbitrarily shaped waveforms. To enter the time scale of natural dynamic processes in many systems, femtosecond pulse shaping techniques must be extended to the ultrashort pulse domain (teach our laser to control its own phase by using spectral blueshifting in a rapidly created plasma as a feedback to the algorithm. Control of lattice vibrations has long been sought as a means of studying phonon-related processes in solids. In addition, generation and control of large-amplitude optical phonon modes may open a path to femtosecond time- resolved studies of structural phase transitions and production of ultrashort shaped X-ray pulses. We perform pump-probe phase-resolved measurements and control of optical A1g mode in sapphire through shaped-pulse impulsive stimulated Raman scattering (ISRS). We chose this material as a candidate for possible nonlinear oscillations regime for its wide band gap and superior optical properties allowing for high-energy excitation. To enter a nonlinear regime, however, complex asymmetric multiple-pulse excitation is required. Therefore, we make a detailed proposal of the experimental adaptive feedback implementation for optimization of phonon amplitude based on the coherent probe scattering and a novel phase mask calculation algorithm for the real-time asymmetric pulse train generation.

  16. Chemical potential and reaction electronic flux in symmetry controlled reactions.

    Science.gov (United States)

    Vogt-Geisse, Stefan; Toro-Labbé, Alejandro

    2016-07-15

    In symmetry controlled reactions, orbital degeneracies among orbitals of different symmetries can occur along a reaction coordinate. In such case Koopmans' theorem and the finite difference approximation provide a chemical potential profile with nondifferentiable points. This results in an ill-defined reaction electronic flux (REF) profile, since it is defined as the derivative of the chemical potential with respect to the reaction coordinate. To overcome this deficiency, we propose a new way for the calculation of the chemical potential based on a many orbital approach, suitable for reactions in which symmetry is preserved. This new approach gives rise to a new descriptor: symmetry adapted chemical potential (SA-CP), which is the chemical potential corresponding to a given irreducible representation of a symmetry group. A corresponding symmetry adapted reaction electronic flux (SA-REF) is also obtained. Using this approach smooth chemical potential profiles and well defined REFs are achieved. An application of SA-CP and SA-REF is presented by studying the Cs enol-keto tautomerization of thioformic acid. Two SA-REFs are obtained, JA'(ξ) and JA'' (ξ). It is found that the tautomerization proceeds via an in-plane delocalized 3-center 4-electron O-H-S hypervalent bond which is predicted to exist only in the transition state (TS) region. © 2016 Wiley Periodicals, Inc.

  17. Microstructural characterization and chemical compatibility of pulsed laser deposited yttria coatings on high density graphite

    Energy Technology Data Exchange (ETDEWEB)

    Sure, Jagadeesh [Corrosion Science and Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam — 603 102 (India); Mishra, Maneesha [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102 (India); Tarini, M. [SRM University, Kattankulathur-603 203 (India); Shankar, A. Ravi; Krishna, Nanda Gopala [Corrosion Science and Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam — 603 102 (India); Kuppusami, P. [Physical Metallurgy Group, Indira Gandhi Centre for Atomic Research, Kalpakkam-603 102 (India); Mallika, C. [Corrosion Science and Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam — 603 102 (India); Mudali, U. Kamachi, E-mail: kamachi@igcar.gov.in [Corrosion Science and Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam — 603 102 (India)

    2013-10-01

    Yttria coatings were deposited on high density (HD) graphite substrate by pulsed laser deposition method and subsequently annealing in vacuum at 1373 K was carried out to evaluate the thermal stability of the coatings. Yttria deposited on HD graphite samples were exposed to molten LiCl–KCl salt at 873 K for 3 h to evaluate the corrosion behavior of the coating for the purpose of pyrochemical reprocessing applications. The microstructure and the corrosion behavior of the yttria coating deposited on HD graphite in molten LiCl–KCl salt were evaluated by several characterization techniques. X-ray diffraction and Laser Raman patterns confirmed the presence of cubic phase of yttria in the coating. The surface morphology of yttria coating on HD graphite examined by scanning electron microscope and atomic force microscopy revealed the agglomeration of oxide particles and formation of clusters. After annealing at 1373 K, no appreciable grain growth of yttria particles could be observed. X-ray photoelectron spectroscopy analysis was carried out for elemental analysis before and after chemical compatibility test of the coated samples in molten LiCl–KCl salt to identify the corrosive elements present on the yttria coatings. The chemical compatibility and thermal stability of the yttria coating on HD graphite in molten LiCl–KCl salt medium have been established. - Highlights: • Y{sub 2}O{sub 3} coating was deposited on graphite by pulsed laser deposition method. • Chemical compatibility of Y{sub 2}O{sub 3} coating in LiCl–KCl salt at 873 K was studied. • Gibbs free energy change was positive for Y{sub 2}O{sub 3} reaction with Cl{sub 2}, U and UCl{sub 3}. • Y{sub 2}O{sub 3} coating exhibited better corrosion performance in molten LiCl–KCl salt.

  18. Controlled Chemical Patterns with ThermoChemical NanoLithography (TCNL)

    Science.gov (United States)

    Carroll, Keith; Giordano, Anthony; Wang, Debin; Kodali, Vamsi; King, W. P.; Marder, S. R.; Riedo, E.; Curtis, J. E.

    2012-02-01

    Many research areas, both fundamental and applied, rely upon the ability to organize non-trivial assemblies of molecules on surfaces. In this work, we introduce a significant extension of ThermoChemical NanoLithography (TCNL), a high throughput chemical patterning technique that uses temperature-driven chemical reactions localized near the tip of a thermal cantilever. By combining a chemical kinetics based model with experiments, we have developed a protocol for varying the concentration of surface bound molecules. The result is an unprecedented ability to fabricate extremely complex patterns comprised of varying chemical concentrations, as demonstrated by sinusoidal patterns of amine groups with varying pitches (˜5-15 μm) and the replication of Leonardo da Vinci's Mona Lisa with dimensions of ˜30 x 40 μm^2. Programmed control of the chemical reaction rate should have widespread applications for a technique which has already been shown to nanopattern various substrates including graphene nanowires, piezoelectric crystals, and optoelectronic materials.

  19. Determining treatment frequency for controlling weeds on traffic islands using chemical and non-chemical weed control

    DEFF Research Database (Denmark)

    Rask, Anne Merete; Larsen, S.U.; Andreasen, Christian;

    2013-01-01

    Many public authorities rely on the use of non-chemical weed control methods, due to stringent restrictions on herbicide use in urban areas. However, these methods usually require more repeated treatments than chemical weed management, resulting in increased costs of weed management. In order...... to investigate the efficacy of four non-chemical weed control methods and glyphosate treatment, experiments were carried out on traffic islands in the growing seasons 2005 and 2006. Three trial sites were each divided into six treatment areas, which were either treated with glyphosate, flame, steam, hot air....../flame, hot water or left untreated. The treatments were carried out at regular, predetermined intervals throughout the growing season in 2004, whereas in 2005 and 2006 how many treatments that were required to keep weed cover below a predetermined acceptance level of 2% were investigated. Percentage weed...

  20. Pollution control in oil, gas and chemical plants

    CERN Document Server

    Bahadori, Alireza

    2014-01-01

    This unique book covers the fundamental requirements for air, soil, noise and water pollution control in oil and gas refineries, chemical plants, oil terminals, petrochemical plants, and related facilities. Coverage includes design and operational considerations relevant to critical systems such as monitoring of water pollution control, equipment, and engineering techniques as well as engineering/technological methods related to soil, noise and air pollution control. This book also: ·         Covers a diverse list of pollution control strategies important to practitioners, ranging from waste water gathering systems and oil/suspended solids removal to chemical flocculation units, biological treatment, and sludge handling and treatment ·         Provides numerous step-by-step tutorials that orient both entry level and veteran engineers to the essentials of pollution control methods in petroleum and chemical industries ·         Includes a comprehensive glossary providing readers with...

  1. Economic model predictive control theory, formulations and chemical process applications

    CERN Document Server

    Ellis, Matthew; Christofides, Panagiotis D

    2017-01-01

    This book presents general methods for the design of economic model predictive control (EMPC) systems for broad classes of nonlinear systems that address key theoretical and practical considerations including recursive feasibility, closed-loop stability, closed-loop performance, and computational efficiency. Specifically, the book proposes: Lyapunov-based EMPC methods for nonlinear systems; two-tier EMPC architectures that are highly computationally efficient; and EMPC schemes handling explicitly uncertainty, time-varying cost functions, time-delays and multiple-time-scale dynamics. The proposed methods employ a variety of tools ranging from nonlinear systems analysis, through Lyapunov-based control techniques to nonlinear dynamic optimization. The applicability and performance of the proposed methods are demonstrated through a number of chemical process examples. The book presents state-of-the-art methods for the design of economic model predictive control systems for chemical processes. In addition to being...

  2. Stainless steel surface wettability control via laser ablation in external electric field

    Science.gov (United States)

    Serkov, A. A.; Shafeev, G. A.; Barmina, E. V.; Loufardaki, A.; Stratakis, E.

    2016-12-01

    Laser ablation of stainless steel in external electric field (up to 10 kV/cm) is experimentally studied. The dependencies of both morphology and chemical properties of surface structures on laser parameters and electric field strength are investigated. Surface wettability properties of the laser-treated samples are considered by means of contact angle measurement. It is shown that under certain conditions laser irradiation in external electric field can render the surface superhydrophobic. Influence of electric field on the laser surface treatment is discussed on basis of its impact on melt solidification and oxidation processes.

  3. Diesel combustion: an integrated view combining laser diagnostics, chemical kinetics, and empirical validation

    Energy Technology Data Exchange (ETDEWEB)

    Akinyami, O C; Dec, J E; Durrett, R P; Flynn, P F; Hunter, G L; Loye, A O; Westbrook, C

    1999-02-01

    This paper proposes a structure for the diesel combustion process based on a combination of previously published and new results. Processes are analyzed with proven chemical kinetic models and validated with data from production-like direct injection diesel engines. The analysis provides new insight into the ignition and particulate formation processes, which combined with laser diagnostics, delineates the two-stage nature of combustion in diesel engines. Data are presented to quantify events occurring during the ignition and initial combustion processes that form soot precursors. A framework is also proposed for understanding the heat release and emission formation processes.

  4. Real-time power measurement and control for high power diode laser

    Science.gov (United States)

    Qin, Wen-bin; Liu, You-qiang; Cao, Yin-hua; Wang, Zhi-yong

    2011-06-01

    As the continual improvement of technology and beam quality, diode laser, with poor beam quality, no longer just apply to pump solid-state laser. As a kind of implement of laser materials processing, high-power diode laser has been used in manufacture, as a brand new means of laser processing. Due to the influence of inevitable unstable factors, for example, the temperature of water-cooler, the current of power supply, etc, the output power of diode laser will be unstable. And laser output power, as an important parameter, frequently affects the performance of the laser beam and the experimental results of processing, especially in the laser materials processing. Therefore, researching the real-time power measurement and control of high power diode laser has great significance, and for diode laser, it would improve performance of itself. To achieve the purpose of real-time detection, traditional measuring method, placing a power sensor behind the total-reflection mirror of laser resonant cavity, is mainly applied in the system of gas laser and solid-state laser. However, Owing to the high integration level of diode laser, traditional measuring method can't be adopted. A technique for real-time measure output power of high power diode laser is developed to improve quality of the laser in this paper. A lens placed at an angle of 45° in the system was used to sample output light of laser, and a piece of ground glass was used to uniform the beam power density, then the photoelectric detector received an optic signal and converted it into electric signal. This feeble signal was processed by amplification circuit with a filter. Finally, this detected electric signal was applied to accomplish the closed-loop control of power. The performance of power measurement and control system was tested with the 300W diode laser, and the measuring inaccuracy achieved was less than +/-1%.

  5. Laser-Pulse-Shape Control of Seeded QED Cascades

    CERN Document Server

    Tamburini, Matteo; Keitel, Christoph H

    2015-01-01

    The emergence of electron-positron cascades via ultrastrong electromagnetic fields constitutes a prominent manifestation of the complex interplay between strong-field QED processes and multiparticle dynamics. Here the onset and development of electron-positron cascades are investigated in the head-on collision of two realistic tightly focused ultraintense optical laser pulses in a tenuous gas. As a consequence of the large ponderomotive forces expelling all electrons of the gas from the focal volume, we demonstrate that the onset of QED cascades may be prevented even at intensities around $10^{26}\\;\\text{W/cm$^2$}$ by focusing the laser energy almost down to the diffraction limit. Alternatively, a well controlled development of a QED cascade may be facilitated at laser intensities below $10^{24}\\;\\text{W/cm$^2$}$ per beam by enlarged focal areas and a rapid rise of the pulse or at total powers near $20\\;\\text{PW}$ by employing suitable high-$Z$ gases.

  6. Spectrocolorimetric Control of Ancient Documents Postablation with Excimer Lasers

    Science.gov (United States)

    Soares, Olivério D. D.; Miranda, Rosa M.; Costa, José L. C.

    1999-10-01

    The application of excimer lasers in ablation, cleaning, and restoration for the recovery of paper and parchment manuscripts is a recently implemented technique. A report of the use of excimer lasers in a cleaning process by which mud was removed from Islamic papers and parchments is presented. It was found that, because of the close proximity of the binding energies of paper to paper and of paper to mud, it was difficult to maintain control of the ablation process. However, the substrate was not affected. Spectrocolorimetry was used as a technique to detect the effects of ablation on cleaned areas of the manuscripts in terms of change in color appearance and severity of aging postablation. The analysis was performed by comparison of treated and untreated areas. Mathematical modeling was developed to define a representative original color and a color-distribution parameter. Improvements in the measuring method were made to yield the required precision for evaluating differences in color produced by laser ablation and to follow the color evolution after ablation. Results show that the effects of restoration, aging, and the environmental conditions can be individually identified under certain conditions. The method has applications in other domains.

  7. Composition analysis of oxide films formed on titanium surface under pulsed laser action by method of chemical thermodynamics

    Science.gov (United States)

    Ageev, E. I.; Andreeva, Ya M.; Karlagina, Yu Yu; Kolobov, Yu R.; Manokhin, S. S.; Odintsova, G. V.; Slobodov, A. A.; Veiko, V. P.

    2017-04-01

    A pulsed fiber laser with a wavelength of 1.06 µm was used to treat a commercial pure titanium surface in the air at intensities below the ablation threshold to provide oxide formation. Laser oxidation results are predicted by the chemical thermodynamic method and confirmed by experimental techniques (x-ray diffraction, energy dispersive x-ray spectroscopy). For the first time, the chemical thermodynamic method was used for determining the qualitative and quantitative phase-chemical composition of the compounds formed by a pulsed laser heating of commercial titanium in the air, and its applicability is proven. The simulation shows that multilayered composite film appears on a surface, the lower layers of which consist of Ti2O3 and TiO oxides with the addition of titanium nitride; and the thin upper layer consists of transparent titanium dioxide. Also, the chemical composition of films remains unchanged within a temperature range of 881–2000 K.

  8. Chemical and ecological control methods for Epitrix spp.

    Directory of Open Access Journals (Sweden)

    A. G. S. Cuthbertson

    2015-01-01

    Full Text Available Very little information exists in regards to the control options available for potato flea beetles, Epitrix spp. This short review covers both chemical and ecological options currently available for control of Epitrix spp. Synthetic pyrethroids are the weapon of choice for the beetles. However, the impetus in integrated pest management is to do timely (early-season applications with something harsh which will give long-term protection at a time when there are not a lot of beneficials in the field. Finding the balance for control of Epitrix spp. is proving difficult.

  9. High energy conversion efficiency in laser-proton acceleration by controlling laser-energy deposition onto thin foil targets

    Energy Technology Data Exchange (ETDEWEB)

    Brenner, C. M. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX (United Kingdom); Robinson, A. P. L.; Markey, K.; Scott, R. H. H.; Lancaster, K. L.; Musgrave, I. O.; Spindloe, C.; Winstone, T.; Wyatt, D.; Neely, D. [Central Laser Facility, STFC, Rutherford Appleton Laboratory, Didcot, Oxon OX11 0QX (United Kingdom); Gray, R. J.; McKenna, P. [Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG (United Kingdom); Rosinski, M.; Badziak, J.; Wolowski, J. [Institute of Plasma Physics and Laser Microfusion, 00-908 Warsaw (Poland); Deppert, O. [Institut für Kernphysik, Technische Universität Darmstadt, 64289 Darmstadt (Germany); Batani, D. [Dipartimento di Fisica G. Occhialini, Universita di Milano Bicocca, 20126 Milan (Italy); Davies, J. R. [Laboratory for Laser Energetics, Fusion Science Center for Extreme States of Matter, University of Rochester, Rochester, New York 14623 (United States); Hassan, S. M.; Tatarakis, M. [Department of Electronics Engineering, Centre for Plasma Physics and Lasers, 73133 Chania, 74100 Rethymno, Crete (Greece); and others

    2014-02-24

    An all-optical approach to laser-proton acceleration enhancement is investigated using the simplest of target designs to demonstrate application-relevant levels of energy conversion efficiency between laser and protons. Controlled deposition of laser energy, in the form of a double-pulse temporal envelope, is investigated in combination with thin foil targets in which recirculation of laser-accelerated electrons can lead to optimal conditions for coupling laser drive energy into the proton beam. This approach is shown to deliver a substantial enhancement in the coupling of laser energy to 5–30 MeV protons, compared to single pulse irradiation, reaching a record high 15% conversion efficiency with a temporal separation of 1 ps between the two pulses and a 5 μm-thick Au foil. A 1D simulation code is used to support and explain the origin of the observation of an optimum pulse separation of ∼1 ps.

  10. Externally Controlled Injection of Electrons by a Laser Pulse in a Laser Wakefield Electron Accelerator

    CERN Document Server

    Chen Szu Yuan; Chen Wei Ting; Chien, Ting-Yei; Lee, Chau-Hwang; Lin, Jiunn-Yuan; Wang, Jyhpyng

    2005-01-01

    Spatially and temporally localized injection of electrons is a key element for development of plasma-wave electron accelerator. Here we report the demonstration of two different schemes for electron injection in a self-modulated laser wakefield accelerator (SM-LWFA) by using a laser pulse. In the first scheme, by implementing a copropagating laser prepulse with proper timing, we are able to control the growth of Raman forward scattering and the production of accelerated electrons. We found that the stimulated Raman backward scattering of the prepulse plays the essential role of injecting hot electrons into the fast plasma wave driven by the pump pulse. In the second scheme, by using a transient density ramp we achieve self-injection of electrons in a SM-LWFA with spatial localization. The transient density ramp is produced by a prepulse propagating transversely to drill a density depression channel via ionization and expansion. The same mechanism of injection with comparable efficiency is also demonstrated wi...

  11. The evolution of a large laser control system - From Shiva to Nova

    Energy Technology Data Exchange (ETDEWEB)

    Suski, G.J.; Holloway, F.W.

    1979-09-01

    The Nova laser system is a 200 terawatt laser facility under construction at Lawrence Livermore Laboratory. Its current operational predecessor, the 30 terawatt Shiva laser, is controlled and diagnosed via a network of 50 computers. Although the highly distributed Shiva control system has proven effective and reliable, the need for more integrated process control on Nova is leading to a more centralized architecture. An overview of these control systems is presented and their differences are discussed.

  12. Chemical and mechanical weed control in soybean (Glycine max

    Directory of Open Access Journals (Sweden)

    Weber, Jonas Felix

    2016-02-01

    Full Text Available In this study we investigated the possibility of chemical and mechanical weed control strategies in soybean. Soybean field experiments were carried out in 2013 and 2014 in Southern Germany. Five treatments including common herbicide mixtures and four mechanical weed control treatments, implementing a harrow and a hoe, were tested at different locations. In the herbicide experiments two treatments were applied by PRE emergence herbicides (metribuzin, clomazone, dimethenamid and metribuzin, flufenacet, clomazone and another two treatments were sprayed with a combination of PRE + POST emergence herbicides (metribuzin, flufenacet, thifensulfuron and pendimethalin, thifensulfuron, bentazone, cycloxydim. Furthermore, a POST herbicide treatment was implemented (thifensulfuron, bentazone, thifensulfuron and fluazifop-P-butyl. In the mechanical weed control experiments, treatments were: three times hoeing, PRE emergence harrowing plus three times hoeing, hoeing and harrowing in rotation or three times harrowing. In both experiments an untreated control was included. A 90% weed control efficacy and 23% yield increase was observed in the POST herbicide treatment. PRE + POST treatments resulted in 92% to 99% weed control efficiency and 15% yield increase compared to the untreated control. In the mechanical weed control experiments the combination of PRE emergence harrowing and POST emergence hoeing resulted in 82% weed control efficiency and 34% higher yield compared to the untreated control. Less weed control efficiency (72% was observed in the harrow treatment, leading to 20% higher yield compared to the control. The suitability of both strategies for implementation in “Integrated Weed Management” has been investigated.

  13. The density matrix picture of laser coherent control current

    Institute of Scientific and Technical Information of China (English)

    SHOU Qian; ZHANG Haichao; LIU Luning; LIN Weizhu

    2004-01-01

    The physical substance of the coherent control current and the optical rectification have been analyzed based on density matrix perturbation theory. The analytical results demonstrate that they arise from the real and virtual manifestations of the same nonlinear process associated with diagonal and non-diagonal density matrix.And in terms of polarization, they respectively arise from the intraband and interband polarizations. Both the evolution of the coherent control current exited by ultrafast laser pulse and its dependence on frequency have been studied in time and frequency domains. In order to get an explicit knowledge of intraband polarization and the origination of the coherent control current, we have investigated the initial photo-carriers momentum distribution. The ultrafast decay of the polar momentum population in order of tens of femtosends is given to illustrate its instantaneous optical response.

  14. AGV Trajectory Control Based on Laser Sensor Navigation

    Directory of Open Access Journals (Sweden)

    Thanh Luan Bui

    2013-01-01

    Full Text Available Autonomous Guided Vehicle Systems (AGVs are used to transport goods and products in manufacturing fields where navigation can be done in a structured environment. In order to track the given trajectory, a tracking control based on Lyapunov stability theory is introduced. The use of the nonlinear Lyapunov technique provides robustness for load disturbance and sensor noise. To apply Lyapunov's theorem, the kinematic model of AGV is given. To recognize its position in indoor environment, in this paper, a laser sensor device NAV200 is used to detect the AGV position in real-time. For simulation and experiment, software and hardware are described. The AGV consists of 4 wheels with two passive wheels and two driving wheels. A controller is developed based on industrial computer. The effectiveness of the proposed controller is proved by simulation and experimental results

  15. Temperature Controlled Laser Joining of Aluminum to Galvanized Steel

    Science.gov (United States)

    Weller, Daniel; Simon, Jörg; Stritt, Peter; Weber, Rudolf; Graf, Thomas; Bezençon, Cyrille; Bassi, Corrado

    Reliable joining of 6000 series aluminum alloy to galvanized steel is a challenge for current manufacturing technologies. To control and limit the formation of brittle intermetallic phases, mixing of both metals in liquid state has to be avoided. It has been shown that laser weld-brazing is a possible process. Thereby the aluminum and zinc layer of the galvanized steel are molten and the steel remains solid during the process. In addition, to avoid zinc degassing, the aluminum melt bath temperature has to be below zinc boiling temperature of 907°C. To meet these requirements a temperature controlled laser process was developed, allowing to join the two materials without flux and filler material. The thickness of the intermetallic layer shows a dependency on the set temperature used to control the process. At optimum set temperature the thickness of intermetallic phases can be limited to about 5 μm. Tensile strengths of the joints of up to 75% of the aluminum base material were achieved.

  16. Runaway electron beam control for longitudinally pumped metal vapor lasers

    Science.gov (United States)

    Kolbychev, G. V.; Kolbycheva, P. D.

    1995-08-01

    Physics and techniques for producing of the pulsed runaway electron beams are considered. The main obstacle for increasing electron energies in the beams is revealed to be a self- breakdown of the e-gun's gas-filled diode. Two methods to suppress the self-breakdown and enhance the volumetric discharge producing the e-beam are offered and examined. Each of them provides 1.5 fold increase of the ceiling potential on the gun. The methods also give the ways to control several guns simultaneously. Resulting in the possibility of realizing the powerful longitudinal pumping of metal-vapor lasers on self-terminated transitions of atoms or ions.

  17. Laser system for identification, tracking, and control of flying insects.

    Science.gov (United States)

    Mullen, Emma R; Rutschman, Phillip; Pegram, Nathan; Patt, Joseph M; Adamczyk, John J; Johanson, 3ric

    2016-05-30

    Flying insects are common vectors for transmission of pathogens and inflict significant harm to humans and agricultural production in many parts of the world. We present proof of principle for an optical system capable of highly specific vector control. This system utilizes a combination of optical sources, detectors, and sophisticated software to search, detect, and identify flying insects in real-time, with the capability of eradication using a lethal laser pulse. We present data on two insect species to show species distinction; Diaphorina citri, a vector of the causal agent of citrus greening disease, and Anopheles stephensi, a malaria vector.

  18. Controlled calibration method for laser induced breakdown spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Li Wang; Chijian Zhang; Yuan Feng

    2008-01-01

    Laser induced breakdown spectroscopy (LIBS) is a potential technique for rapid analysis of samples present in solids, gases and liquids. In the last two decades it was an object of extensive studies. Controlled calibration method used to analysis the LIBS spectra is investigated. Compared with the inner calibration and calibration-free (CF) methods, this new method overcomes "matrix effect", and demonstrates a better ability to cope with the spectra. It is used to analyze natural soil, and errors of the concentration are decreased about 5%. The result shows that the new method is feasible and accurate.

  19. Quantum coherent control of ultra short laser pulses

    Institute of Scientific and Technical Information of China (English)

    ZHOU JianYing; ZENG JianHua; LI JunTao

    2008-01-01

    The effective photonic control is one of the key issues in photo-physics. Significant advancement in photonic crystals, quantum optics, ultrafast optics as well as micro-nano-optics gives rise to new op-portunities to manipulate the emission and propagation in optical fields, leading to a number of new and interesting discoveries, e.g., ultrashort light pulse storage and efficient energy conversion. This paper reviews the latest research progress in storage, release and energy conversion for ultrashort laser pulses in periodical arrays of absorbing medium. Techniques to fabricate such devices are also presented.

  20. Fabrication of microchannels in single-crystal GaN by wet-chemical-assisted femtosecond-laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Nakashima, Seisuke, E-mail: seisuke@riken.jp [RIKEN-Advanced Science Institute, Wako, Saitama 351-0198 (Japan); Sugioka, Koji; Midorikawa, Katsumi [RIKEN-Advanced Science Institute, Wako, Saitama 351-0198 (Japan)

    2009-09-30

    We investigated micro- and nano-fabrication of wide band-gap semiconductor gallium nitride (GaN) using a femtosecond (fs) laser. Nanoscale craters were successfully formed by wet-chemical-assisted fs-laser ablation, in which the laser beam is focused onto a single-crystal GaN substrate in a hydrochloric acid (HCl) solution. This allows efficient removal of ablation debris produced by chemical reactions during ablation, resulting in high-quality ablation. However, a two-step processing method involving irradiation by a fs-laser beam in air followed by wet etching, distorts the shape of the crater because of residual debris. The threshold fluence for wet-chemical-assisted fs-laser ablation is lower than that for fs-laser ablation in air, which is advantageous for improving fabrication resolution since it reduces thermal effects. We have fabricated craters as small as 510 nm by using a high numerical aperture (NA) objective lens with an NA of 0.73. Furthermore, we have formed three-dimensional hollow microchannels in GaN by fs-laser direct-writing in HCl solution.

  1. Fabrication of microchannels in single-crystal GaN by wet-chemical-assisted femtosecond-laser ablation

    Science.gov (United States)

    Nakashima, Seisuke; Sugioka, Koji; Midorikawa, Katsumi

    2009-09-01

    We investigated micro- and nano-fabrication of wide band-gap semiconductor gallium nitride (GaN) using a femtosecond (fs) laser. Nanoscale craters were successfully formed by wet-chemical-assisted fs-laser ablation, in which the laser beam is focused onto a single-crystal GaN substrate in a hydrochloric acid (HCl) solution. This allows efficient removal of ablation debris produced by chemical reactions during ablation, resulting in high-quality ablation. However, a two-step processing method involving irradiation by a fs-laser beam in air followed by wet etching, distorts the shape of the crater because of residual debris. The threshold fluence for wet-chemical-assisted fs-laser ablation is lower than that for fs-laser ablation in air, which is advantageous for improving fabrication resolution since it reduces thermal effects. We have fabricated craters as small as 510 nm by using a high numerical aperture (NA) objective lens with an NA of 0.73. Furthermore, we have formed three-dimensional hollow microchannels in GaN by fs-laser direct-writing in HCl solution.

  2. Laser Induced Breakdown Spectroscopy applications to meteorites: Chemical analysis and composition profiles

    Science.gov (United States)

    Dell'Aglio, M.; De Giacomo, A.; Gaudiuso, R.; Pascale, O. De; Senesi, G. S.; Longo, S.

    2010-12-01

    A fast procedure for chemical analysis of different meteorites is presented, based on LIBS (Laser Induced Breakdown Spectroscopy). The technique is applied to several test cases (Dhofar 019, Dhofar 461, Sahara 98222, Toluca, Sikhote Alin and Campo del Cielo) and can be useful for rapid meteorite identification providing geologists with specific chemical information for meteorite classification. Concentration profiles of Fe, Ni and Co are simultaneously detected across the Widmanstätten structure of the iron meteorite Toluca with a view to determining cooling rates. The LIBS analysis of meteorites is also used as a laboratory test for analogous studies on the respective parent bodies (Mars, asteroids) in space exploration missions where one clear advantage of the proposed technique is that no direct contact with the sample is required.

  3. Chemical measurements with optical fibers for process control.

    Science.gov (United States)

    Boisde, G; Blanc, F; Perez, J J

    1988-02-01

    Several aspects of remote in situ spectrophotometric measurement by means of optical fibers are considered in the context of chemical process control. The technique makes it possible to measure a species in a particular oxidation state, such as plutonium(VI), sequentially, under the stringent conditions of automated analysis. For the control of several species in solution, measurements at discrete wavelengths on the sides of the absorption peaks serve to increase the dynamic range. Examples are given concerning the isotopic separation of uranium in the Chemex process. The chemical control of complex solutions containing numerous mutually interfering species requires a more elaborate spectral scan and real-time processing to determine the chemical kinetics. Photodiode array spectrophotometers are therefore ideal for analysing the uranium and plutonium solutions of the Purex process. Remote on-line control by ultraviolet monitoring exhibits limitations chiefly due to Rayleigh scattering in the optical fibers. The measurement of pH in acidic (0.8-3.2) and basic media (10-13) has also been attempted. Prior calibration, signal processing and optical spectra modeling are also discussed.

  4. Controlling chemical dosing for sulfide mitigation in sewer networks using a hybrid automata control strategy.

    Science.gov (United States)

    Liu, Yiqi; Ganigué, Ramon; Sharma, Keshab; Yuan, Zhiguo

    2013-01-01

    Chemicals such as magnesium hydroxide (Mg(OH)2) and iron salts are widely used to control sulfide-induced corrosion in sewer networks composed of interconnected sewer pipe lines and pumping stations. Chemical dosing control is usually non-automatic and based on experience, thus often resulting in sewage reaching the discharge point receiving inadequate or even no chemical dosing. Moreover, intermittent operation of pumping stations makes traditional control theory inadequate. A hybrid automata-based (HA-based) control method is proposed in this paper to coordinate sewage pumping station operations by considering their states, thereby ensuring suitable chemical concentrations in the network discharge. The performance of the proposed control method was validated through a simulation study of a real sewer network using real sewage flow data. The physical, chemical and biological processes were simulated using the well-established SeweX model. The results suggested that the HA-based control strategy significantly improved chemical dosing control performance and sulfide mitigation in sewer networks, compared to the current common practice.

  5. Laser-based mass spectrometry for in situ chemical composition analysis of planetary surfaces

    Science.gov (United States)

    Frey, Samira; Neuland, Maike B.; Grimaudo, Valentine; Moreno-García, Pavel; Riedo, Andreas; Tulej, Marek; Broekmann, Peter; Wurz, Peter

    2016-04-01

    Mass spectrometry is an important analytical technique in space research. The chemical composition of planetary surface material is a key scientific question on every space mission to a planet, moon or asteroid. Chemical composition measurements of rocky material on the surface are of great importance to understand the origin and evolution of the planetary body.[1] A miniature laser ablation/ionisation reflectron- type time-of-flight mass spectrometer (instrument name LMS) was designed and built at the University of Bern for planetary research.[2] Despite its small size and light weight, the LMS instrument still maintains the same capabilities as large laboratory systems, which makes it suitable for its application on planetary space missions.[3-5] The high dynamic range of about eight orders of magnitude, high lateral (μm-level) and vertical (sub-nm level) resolution and high detection sensitivity for almost all elements (10 ppb, atomic fraction) make LMS a versatile instrument for various applications. LMS is a suitable instrument for in situ measurements of elemental and isotope composition with high precision and accuracy. Measurements of Pb- isotope abundances can be used for dating of planetary material. Measurements of bio-relevant elements allow searching for past or present life on a planetary surface. The high spatial resolution, both in lateral and vertical direction, is of considerable interest, e.g. for analysis of inhomogeneous, extraterrestrial samples as well as weathering processes of planetary material. References [1] P. Wurz, D. Abplanalp, M. Tulej, M. Iakovleva, V.A. Fernandes, A. Chumikov, and G. Managadze, "Mass Spectrometric Analysis in Planetary Science: Investigation of the Surface and the Atmosphere", Sol. Sys. Res., 2012, 46, 408. [2] U. Rohner, J.A. Whitby, P. Wurz, "A miniature laser ablation time of flight mass spectrometer for in situ planetary exploration" Meas. Sci. Tch., 2003, 14, 2159. [3] M. Tulej, A. Riedo, M.B. Neuland, S

  6. Microfabricated Instrumentation for Chemical Sensing in Industrial Process Control

    Energy Technology Data Exchange (ETDEWEB)

    Ramsey, J. M.

    2000-06-01

    The monitoring of chemical constituents in manufacturing processes is of economic importance to most industries. The monitoring and control of chemical constituents may be of importance for product quality control or, in the case of process effluents, of environmental concern. The most common approach now employed for chemical process control is to collect samples which are returned to a conventional chemical analysis laboratory. This project attempts to demonstrate the use of microfabricated structures, referred to as 'lab-on-a-chip' devices, that accomplish chemical measurement tasks that emulate those performed in the conventional laboratory. The devices envisioned could be used as hand portable chemical analysis instruments where samples are analyzed in the field or as emplaced sensors for continuous 'real-time' monitoring. This project focuses on the development of filtration elements and solid phase extraction elements that can be monolithically integrated onto electrophoresis and chromatographic structures pioneered in the laboratory. Successful demonstration of these additional functional elements on integrated microfabricated devices allows lab-on-a-chip technologies to address real world samples that would be encountered in process control environments. The resultant technology has a broad application to industrial environmental monitoring problems. such as monitoring municipal water supplies, waste water effluent from industrial facilities, or monitoring of run-off from agricultural activities. The technology will also be adaptable to manufacturing process control scenarios. Microfabricated devices integrating sample filtration, solid phase extraction, and chromatographic separation with solvent programming were demonstrated. Filtering of the sample was accomplished at the same inlet with an array of seven channels each 1 {micro}m deep and 18 {micro}m wide. Sample concentration and separation were performed on channels 5 {micro}m deep

  7. Comparison of laser-ablation and hot-wall chemical vapour deposition techniques for nanowire fabrication

    Science.gov (United States)

    Stern, E.; Cheng, G.; Guthrie, S.; Turner-Evans, D.; Broomfield, E.; Lei, B.; Li, C.; Zhang, D.; Zhou, C.; Reed, M. A.

    2006-06-01

    A comparison of the transport properties of populations of single-crystal, In2O3 nanowires (NWs) grown by unassisted hot-wall chemical vapour deposition (CVD) versus NWs grown by laser-ablation-assisted chemical vapour deposition (LA-CVD) is presented. For nominally identical growth conditions across the two systems, NWs fabricated at 850 °C with laser-ablation had significantly higher average mobilities at the 99.9% confidence level, 53.3 ± 5.8 cm2 V-1 s-1 versus 10.2 ± 1.9 cm2 V-1 s-1. It is also observed that increasing growth temperature decreases mobility for LA-CVD NWs. Transmission electron microscopy studies of CVD-fabricated samples indicate the presence of an amorphous In2O3 region surrounding the single-crystal core. Further, low-temperature measurements verify the presence of ionized impurity scattering in low-mobility CVD-grown NWs.

  8. Semi-gas kinetics model for performance modeling of flowing chemical oxygen-iodine lasers (COIL)

    Institute of Scientific and Technical Information of China (English)

    GAO Zhi; HU Limin; SHEN Yiqing

    2004-01-01

    A semi-gas kinetics (SGK) model for performance analyses of flowing chemical oxygen-iodine laser (COIL) is presented. In this model, the oxygen-iodine reaction gas flow is treated as a continuous medium, and the effect of thermal motions of particles of different laser energy levels on the performances of the COIL is included and the velocity distribution function equations are solved by using the double-parameter perturbational method. For a premixed flow, effects of different chemical reaction systems, different gain saturation models and temperature, pressure, yield of excited oxygen, iodine concentration and frequency-shift on the performances of the COIL are computed, and the calculated output power agrees well with the experimental data. The results indicate that the power extraction of the SGK model considering 21 reactions is close to those when only the reversible pumping reaction is considered, while different gain saturation models and adjustable parameters greatly affect the output power, the optimal threshold gain range, and the length of power extraction.

  9. Communication: Control of chemical reactions using electric field gradients.

    Science.gov (United States)

    Deshmukh, Shivaraj D; Tsori, Yoav

    2016-05-21

    We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts.

  10. Communication: Control of chemical reactions using electric field gradients

    Science.gov (United States)

    Deshmukh, Shivaraj D.; Tsori, Yoav

    2016-05-01

    We examine theoretically a new idea for spatial and temporal control of chemical reactions. When chemical reactions take place in a mixture of solvents, an external electric field can alter the local mixture composition, thereby accelerating or decelerating the rate of reaction. The spatial distribution of electric field strength can be non-trivial and depends on the arrangement of the electrodes producing it. In the absence of electric field, the mixture is homogeneous and the reaction takes place uniformly in the reactor volume. When an electric field is applied, the solvents separate and the reactants are concentrated in the same phase or separate to different phases, depending on their relative miscibility in the solvents, and this can have a large effect on the kinetics of the reaction. This method could provide an alternative way to control runaway reactions and to increase the reaction rate without using catalysts.

  11. Laser-micromachined and laminated microfluidic components for miniaturized thermal, chemical, and biological systems

    Science.gov (United States)

    Martin, Peter M.; Matson, Dean W.; Bennett, Wendy D.; Stewart, Donald C.; Lin, Yuehe

    1999-03-01

    Microchannel microfluidic components are being developed for heat transfer, chemical reactor, chemical analysis, and biological analytical applications. Specific applications include chemical sensing, DNA replication, blood analysis, capillary electrophoresis, fuel cell reactors, high temperature chemical reactors, heat pumps, combustors, and fuel processors. Two general types of component architectures have been developed and the fabrication processes defined. All involve a lamination scheme using plastic, ceramic, or metal laminates, as opposed to planar components. The first type is a stacked architecture that utilizes functionality built in each layer, with fluid flow interconnects between layers. Each layer of the laminate has specific microchannel geometry, and performs a specific function. Polymeric materials are used primarily. Fabrication processes used are laser micromachining, wet and dry etching, and coating deposition. the laminates can also be micromolded plastics. The second architecture employs laminates to form internal microchannels and interconnects. Materials include ceramic tapes and high temperature metals. Catalysts can be placed in the microchannels. Fabrication processes used are diffusion bonding, ceramic bonding and firing, photochemical etching, and electrochemical micromachining. Bonding, thus sealing, the laminates is an important issue. Process conditions have been develop to reduce distortion of the laminates and to hermetically seal the components.

  12. Part height control of laser metal additive manufacturing process

    Science.gov (United States)

    Pan, Yu-Herng

    Laser Metal Deposition (LMD) has been used to not only make but also repair damaged parts in a layer-by-layer fashion. Parts made in this manner may produce less waste than those made through conventional machining processes. However, a common issue of LMD involves controlling the deposition's layer thickness. Accuracy is important, and as it increases, both the time required to produce the part and the material wasted during the material removal process (e.g., milling, lathe) decrease. The deposition rate is affected by multiple parameters, such as the powder feed rate, laser input power, axis feed rate, material type, and part design, the values of each of which may change during the LMD process. Using a mathematical model to build a generic equation that predicts the deposition's layer thickness is difficult due to these complex parameters. In this thesis, we propose a simple method that utilizes a single device. This device uses a pyrometer to monitor the current build height, thereby allowing the layer thickness to be controlled during the LMD process. This method also helps the LMD system to build parts even with complex parameters and to increase material efficiency.

  13. Controlled electron injection using nanoparticles in laser wakefield acceleration

    Science.gov (United States)

    Cho, Myung Hoon; Pathak, Vishwa Bandhu; Kim, Hyung Taek; Nakajima, Kazuhisa; Nam, Chang Hee; CenterRelativistic Laser Science Team

    2016-10-01

    Laser wakefield acceleration is one of compact electron acceleration schemes due to its high accelerating gradient. Despite of the great progress of several GeV electron beams with high power lasers, the electron injection to the wakefield is still a critical issue for a very low density plasma 1017 electrons/cc. In this talk a novel method to control the injection using nanoparticles is proposed. We investigate the electron injection by analyzing the interaction of electrons with the two potentials - one created by a nanoparticle and the other by the wakefield. The nanoparticle creates a localized electric potential and this nanoparticle potential just slips the present wake potential. To confirm the Hamiltonian description of the interaction, a test particle calculation is performed by controlling the bubble and the nanoparticle potentials. A multi-dimensional particle-in-cell simulations are also presented as a proof-of-principle. Comparing theoretical estimates and PIC simulation, we suggest nanoparticle parameters of size and electron density depending on the background plasma density. Our scheme can be applicable for low plasma density to break though the limitation of self-injection toward extremely high energy electron energy.

  14. ANALYSIS OF CHEMICAL AND PHASE TRANSITIONS OF MULTICOMPONENT ALLOYS UNDER PULSED LASER EXPOSURE IN THE AIR BY METHODS OF CHEMICAL THERMODYNAMICS

    Directory of Open Access Journals (Sweden)

    V. P. Veiko

    2013-03-01

    Full Text Available The article deals with computational thermodynamic method for determination of phase chemical composition of metal alloys surface formed under laser action in the atmosphere, depending on its volume components, conditions of laser exposure and atmosphere composition. By giving an example of laser heating of complex alloy (alloyed steel in the air it is demonstrated that from a set of various possible reactions of interaction between iron, nickel or chrome with air components (oxygen, nitrogen, carbon, their compounds, atmospheric moisture, etc., only strictly defined reactions are realized. Primarily, these are metal oxidation processes with the formation of an oxide film, whose phase and chemical composition is determined by temperature and heating time. Calculation data are confirmed by the experimental data provided by energy-dispersive X-ray spectroscopy.

  15. Chemical-Assisted Femtosecond Laser Writing of Lab-in-Fiber Sensors

    Science.gov (United States)

    Haque, Moez

    fringe contrast and peak resolution beyond that available with FPIs and offer a significant theoretical improvement in refractometer sensitivity. The advanced laser processes optimized here may provide a new base for photonics, microfluidics, and optofluidics fabrication in a LIF platform with multiplexed functionality and rapid prototyping capabilities of fully integrable 3D optofluidic systems. The proposed LIF devices define new micro-systems for temperature, strain, pressure, refractive index, and bend strain sensing that may find application in the acoustic, aerospace, automotive, biological, chemical, civil, or medical fields.

  16. Bioactive Ti metal analogous to human cancellous bone: Fabrication by selective laser melting and chemical treatments.

    Science.gov (United States)

    Pattanayak, Deepak K; Fukuda, A; Matsushita, T; Takemoto, M; Fujibayashi, S; Sasaki, K; Nishida, N; Nakamura, T; Kokubo, T

    2011-03-01

    Selective laser melting (SLM) is a useful technique for preparing three-dimensional porous bodies with complicated internal structures directly from titanium (Ti) powders without any intermediate processing steps, with the products being expected to be useful as a bone substitute. In this study the necessary SLM processing conditions to obtain a dense product, such as the laser power, scanning speed, and hatching pattern, were investigated using a Ti powder of less than 45 μm particle size. The results show that a fully dense plate thinner than 1.8 mm was obtained when the laser power to scanning speed ratio was greater than 0.5 and the hatch spacing was less than the laser diameter, with a 30 μm thick powder layer. Porous Ti metals with structures analogous to human cancellous bone were fabricated and the compressive strength measured. The compressive strength was in the range 35-120 MPa when the porosity was in the range 75-55%. Porous Ti metals fabricated by SLM were heat-treated at 1300 °C for 1h in an argon gas atmosphere to smooth the surface. Such prepared specimens were subjected to NaOH, HCl, and heat treatment to provide bioactivity. Field emission scanning electron micrographs showed that fine networks of titanium oxide were formed over the whole surface of the porous body. These treated porous bodies formed bone-like apatite on their surfaces in a simulated body fluid within 3 days. In vivo studies showed that new bone penetrated into the pores and directly bonded to the walls within 12 weeks after implantation into the femur of Japanese white rabbits. The percentage bone affinity indices of the chemical- and heat-treated porous bodies were significantly higher than that of untreated implants.

  17. Integrated Process Design, Control and Analysis of Intensified Chemical Processes

    DEFF Research Database (Denmark)

    Mansouri, Seyed Soheil

    chemical processes; for example, intensified processes such as reactive distillation. Most importantly, it identifies and eliminates potentially promising design alternatives that may have controllability problems later. To date, a number of methodologies have been proposed and applied on various problems......Process design and process control have been considered as independent problems for many years. In this context, a sequential approach is used where the process is designed first, followed by the control design. However, this sequential approach has its limitations related to dynamic constraint...... violations, for example, infeasible operating points, process overdesign or under-performance. Therefore, by using this approach, a robust performance is not always guaranteed. Furthermore, process design decisions can influence process control and operation. To overcome these limitations, an alternative...

  18. Integrated control system of transverse flow CO II laser and its application

    Science.gov (United States)

    Liu, Juan; Tang, Xiahui; Zhang, Yang; Peng, Hao; Wang, Youqing

    2008-03-01

    Aiming to the special high power CO II laser surface treatment, the paper developed the integrated control system based on S7-200 PLC of transverse flow CO II laser. The selection of key technology and components, detection and control of signals, integrated control of complete circuit, technology of human machine interface and process control of system have been researched. Double closed loop power control system was realized, so that the stability of the laser power was in +/-2%. Also, the giving power can be controlled by the laser controller or by the processing machine, thus, the users can control the laser more efficiently when processing. A series of experiments have been performed on 5kW transverse flow CO II laser, the output laser power was stable at discharge current of 9A for 8 hours, and the maximal power was 5.42 kW. The new type of transverse flow CO II Laser with Integrated Control System has been applied for special laser cladding with power-modulating on the metallic surface of the oil industry production.

  19. An infrared free-electron laser for the Chemical Dynamics Research Laboratory. Design report

    Energy Technology Data Exchange (ETDEWEB)

    Vaughan, D. [comp.

    1992-04-01

    This document describes a free-electron laser (FEL) proposed as part of the Chemical Dynamics Research Laboratory (CDRL), a user facility that also incorporates several advanced lasers of conventional design and two beamlines for the ALS. The FEL itself addresses the needs of the chemical sciences community for a high-brightness, tunable source covering a broad region of the infrared spectrum -- from 3 to 50 {mu}m. All of these sources, together with a variety of sophisticated experimental stations, will be housed in a new building to be located adjacent to the ALS. The radiation sources can be synchronized to permit powerful two-color, pump-probe experiments that will further our fundamental understanding of chemical dynamics at the molecular level, especially those aspects relevant to practical issues in combustion chemistry. The technical approach adopted in this design makes use of superconducting radiofrequency (SCRF) accelerating structures. The primary motivation for adopting this approach was to meet the user requirement for wavelength stability equal to one part in 10{sup 4}. Previous studies concluded that a wavelength stability of only one part in 10{sup 3} could be achieved with currently available room-temperature technology. In addition, the superconducting design operates in a continuous-wave (cw) mode and hence offers considerably higher average optical output power. It also allows for various pulse-gating configurations that will permit simultaneous multiuser operations. A summary of the comparative performance attainable with room-temperature and superconducting designs is given. The FEL described in this report provides a continuous train of 30-ps micropulses, with 100{mu}J of optical energy per micropulse, at a repetition rate of 6.1 MHz. The device can also deliver pulses at a cw repetition rate of 12.2 MHz, with a peak power of 50 {mu}J per micropulse. 70 ref.

  20. An infrared free-electron laser for the Chemical Dynamics Research Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Vaughan, D. (comp.)

    1992-04-01

    This document describes a free-electron laser (FEL) proposed as part of the Chemical Dynamics Research Laboratory (CDRL), a user facility that also incorporates several advanced lasers of conventional design and two beamlines for the ALS. The FEL itself addresses the needs of the chemical sciences community for a high-brightness, tunable source covering a broad region of the infrared spectrum -- from 3 to 50 {mu}m. All of these sources, together with a variety of sophisticated experimental stations, will be housed in a new building to be located adjacent to the ALS. The radiation sources can be synchronized to permit powerful two-color, pump-probe experiments that will further our fundamental understanding of chemical dynamics at the molecular level, especially those aspects relevant to practical issues in combustion chemistry. The technical approach adopted in this design makes use of superconducting radiofrequency (SCRF) accelerating structures. The primary motivation for adopting this approach was to meet the user requirement for wavelength stability equal to one part in 10{sup 4}. Previous studies concluded that a wavelength stability of only one part in 10{sup 3} could be achieved with currently available room-temperature technology. In addition, the superconducting design operates in a continuous-wave (cw) mode and hence offers considerably higher average optical output power. It also allows for various pulse-gating configurations that will permit simultaneous multiuser operations. A summary of the comparative performance attainable with room-temperature and superconducting designs is given. The FEL described in this report provides a continuous train of 30-ps micropulses, with 100{mu}J of optical energy per micropulse, at a repetition rate of 6.1 MHz. The device can also deliver pulses at a cw repetition rate of 12.2 MHz, with a peak power of 50 {mu}J per micropulse. 70 ref.

  1. Acute oral toxicities of wildland fire control chemicals to birds

    Science.gov (United States)

    Vyas, N.B.; Spann, J.W.; Hill, E.F.

    2009-01-01

    Wildland fire control chemicals are released into the environment by aerial and ground applications to manage rangeland, grassland, and forest fires. Acute oral 24 h median lethal dosages (LD50) for three fire retardants (Fire-Trol GTS-R?, Phos-Chek D-75F?, and Fire-Trol LCG-R?) and two Class A fire suppressant foams (Silv-Ex? and Phos-Chek WD881?) were estimated for northern bobwhites, Colinus virginianus, American kestrels, Falco sparverius, and red-winged blackbirds, Agelaius phoeniceus. The LD50s of all chemicals for the bobwhites and red-winged blackbirds and for kestrels dosed with Phos-Chek WD881? and Silv-Ex? were above the predetermined 2000 mg chemical/kg body mass regulatory limit criteria for acute oral toxicity. The LD50s were not quantifiable for kestrels dosed with Fire-Trol GTS-R?, Phos-Chek D-75F?, and Fire-Trol LCG-R? because of the number of birds which regurgitated the dosage. These chemicals appear to be of comparatively low order of acute oral toxicity to the avian species tested.

  2. Fabrication of honeycomb texture on poly-Si by laser interference and chemical etching

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Bogeum; Lee, Myeongkyu, E-mail: myeong@yonsei.ac.kr

    2013-11-01

    In this paper, we present a laser-interference method to fabricate honeycomb textures on poly-Si wafer for reflection reduction. When exposed to three interfering pulsed laser beams at 532 nm, the Si surface was periodically melted in accordance with the interference pattern. As a result, concave holes were generated on the surface because the melted material overflowed and condensed at the periphery. Subsequent acid etching revealed uniform and clean honeycomb textures. The texture depth could be controlled by varying the irradiation condition and a minimum reflectance of 10% was obtained. Transmission electron microscopy analysis showed that no irradiation-induced damage remained after etching. This approach can be a cost-effective alternative to lithographic processes for fabricating high-efficiency poly-Si solar cells.

  3. AMAZON RAINFOREST COSMETICS: CHEMICAL APPROACH FOR QUALITY CONTROL

    Directory of Open Access Journals (Sweden)

    Mariko Funasaki

    2016-02-01

    Full Text Available The market for natural cosmetics featuring ingredients derived from Amazon natural resources is growing worldwide. However, there is neither enough scientific basis nor quality control of these ingredients. This paper is an account of the chemical constituents and their biological activities of fourteen Amazonian species used in cosmetic industry, including açaí (Euterpe oleracea, andiroba (Carapa guianensis, bacuri (Platonia insignis, Brazil nut (Bertholletia excelsa, buriti (Mauritia vinifera or M. flexuosa, cumaru (Dipteryx odorata, cupuaçu (Theobroma grandiflorum, guarana (Paullinia cupana, mulateiro (Calycophyllum spruceanum, murumuru (Astrocaryum murumuru, patawa (Oenocarpus bataua or Jessenia bataua, pracaxi (Pentaclethra macroloba, rosewood (Aniba rosaeodora, and ucuuba (Virola sebifera. Based on the reviewed articles, we selected chemical markers for the quality control purpose and evaluated analytical methods. Even though chromatographic and spectroscopic methods are major analytical techniques in the studies of these species, molecular approaches will also be important as used in food and medicine traceability. Only a little phytochemical study is available about most of the Amazonian species and some species such as açaí and andiroba have many reports on chemical constituents, but studies on biological activities of isolated compounds and sampling with geographical variation are limited.

  4. Selective control of HOD photodissociation using CW lasers

    Indian Academy of Sciences (India)

    Manabendra Sarma; S Adhikari; Manoj K Mishra

    2007-09-01

    Selective control of HOD photodissociation (H-O + D ← HOD → H + O-D) has been theoretically investigated using CW lasers with appropriate carrier frequency and |0, 0〉, |0, 1〉 and |0, 2〉 with zero quantum of excitation in the O-H bond and zero, one and two quanta of excitation in the O-D bond as the initial states. Results indicate that the O-H bond in HOD can be selectively dissociated with a maximum flux of 87% in the H + O-D channel from the ground vibrational state |0, 0〉. For the O-D bond dissociation, it requires two quanta of excitation (|0, 2〉) in the O-D mode to obtain 83% flux in the H-O + D channel. Use of a two colour laser set-up in conjunction with the field optimized initial state (FOIST) scheme to obtain an optimal linear combination of |0, 0〉 and |0, 1〉 vibrational states as the initial state provides an additional 7% improvement to flux in the H-O + D channel as compared to that from the pure |0, 1〉 state.

  5. Laser printing of nanoparticle toner enables digital control of micropatterned carbon nanotube growth.

    Science.gov (United States)

    Polsen, Erik S; Stevens, Adam G; Hart, A John

    2013-05-01

    Commercialization of materials utilizing patterned carbon nanotube (CNT) forests, such as hierarchical composite structures, dry adhesives, and contact probe arrays, will require catalyst patterning techniques that do not rely on cleanroom photolithography. We demonstrate the large scale patterning of CNT growth catalyst via adaptation of a laser-based electrostatic printing process that uses magnetic ink character recognition (MICR) toner. The MICR toner contains iron oxide nanoparticles that serve as the catalyst for CNT growth, which are printed onto a flexible polymer (polyimide) and then transferred to a rigid substrate (silicon or alumina) under heat and mechanical pressure. Then, the substrate is processed for CNT growth under an atmospheric pressure chemical vapor deposition (CVD) recipe. This process enables digital control of patterned CNT growth via the laser intensity, which controls the CNT density; and via the grayscale level, which controls the pixelation of the image into arrays of micropillars. Moreover, virtually any pattern can be designed using standard software (e.g., MS Word, AutoCAD, etc.) and printed on demand. Using a standard office printer, we realize isolated CNT microstructures as small as 140 μm and isolated catalyst ″pixels″ as small as 70 μm (one grayscale dot) and determine that individual toner microparticles result in features of approximately 5-10 μm . We demonstrate that grayscale CNT patterns can function as dry adhesives and that large-area catalyst patterns can be printed directly onto metal foils or transferred to ceramic plates. Laser printing therefore shows promise to enable high-speed micropatterning of nanoparticle-containing thin films under ambient conditions, possibly for a wide variety of nanostructures by engineering of toners containing nanoparticles of desired composition, size, and shape.

  6. Laser spectroscopy

    CERN Document Server

    Demtröder, Wolfgang

    2008-01-01

    Keeping abreast of the latest techniques and applications, this new edition of the standard reference and graduate text on laser spectroscopy has been completely revised and expanded. While the general concept is unchanged, the new edition features a broad array of new material, e.g., frequency doubling in external cavities, reliable cw-parametric oscillators, tunable narrow-band UV sources, more sensitive detection techniques, tunable femtosecond and sub-femtosecond lasers (X-ray region and the attosecond range), control of atomic and molecular excitations, frequency combs able to synchronize independent femtosecond lasers, coherent matter waves, and still more applications in chemical analysis, medical diagnostics, and engineering.

  7. Blinding Techniques in Randomized Controlled Trials of Laser Therapy: An Overview and Possible Solution

    Directory of Open Access Journals (Sweden)

    Ian Relf

    2008-01-01

    Full Text Available Low-level laser therapy has evidence accumulating about its effectiveness in a variety of medical conditions. We reviewed 51 double blind randomized controlled trials (RCTs of laser treatment. Analysis revealed 58% of trials showed benefit of laser over placebo. However, less than 5% of the trials had addressed beam disguise or allocation concealment in the laser machines used. Many of the trials used blinding methods that rely on staff cooperation and are therefore open to interference or bias. This indicates significant deficiencies in laser trial methodology. We report the development and preliminary testing of a novel laser machine that can blind both patient and operator to treatment allocation without staff participation. The new laser machine combines sealed preset and non-bypassable randomization codes, decoy lights and sound, and a conical perspex tip to overcome laser diode glow detection.

  8. Laser cooling and control of excitations in superfluid helium

    CERN Document Server

    Harris, G I; Sheridan, E; Sachkou, Y; Baker, C; Bowen, W P

    2015-01-01

    Superfluidity is an emergent quantum phenomenon which arises due to strong interactions between elementary excitations in liquid helium. These excitations have been probed with great success using techniques such as neutron and light scattering. However measurements to-date have been limited, quite generally, to average properties of bulk superfluid or the driven response far out of thermal equilibrium. Here, we use cavity optomechanics to probe the thermodynamics of superfluid excitations in real-time. Furthermore, strong light-matter interactions allow both laser cooling and amplification of the thermal motion. This provides a new tool to understand and control the microscopic behaviour of superfluids, including phonon-phonon interactions, quantised vortices and two-dimensional quantum phenomena such as the Berezinskii-Kosterlitz-Thouless transition. The third sound modes studied here also offer a pathway towards quantum optomechanics with thin superfluid films, including femtogram effective masses, high me...

  9. A Laser Feedback Control Design for Passive Ring Laser Gyros in a Very High Finesse Cavity.

    Science.gov (United States)

    1985-12-01

    14 II. Theory ....................... 16 Optical Cavities ................ 16 Laser Fundamentals ...............24 The Gaussian Beam. ...............28...c 1-(ABC 1h(.8 = (2.18) F = 1 2.19) - (RARCRD) t = = (2.20) C c[i- (RARRc%)] Laser Fundamentals A laser consists of three basic components: a gain

  10. Surface Contaminant Control Technologies to Improve Laser Damage Resistance of Optics

    Directory of Open Access Journals (Sweden)

    Xiaofeng Cheng

    2014-01-01

    Full Text Available The large high-power solid lasers, such as the National Ignition Facility (NIF of America and the Shenguang-III (SG-III laser facility of China, can output over 2.1 MJ laser pulse for the inertial confinement fusion (ICF experiments. Because of the enhancement of operating flux and the expansion of laser driver scale, the problem of contamination seriously influences their construction period and operation life. During irradiation by intense laser beams, the contaminants on the metallic surface of beam tubes can be transmitted to the optical surfaces and lead to damage of optical components. For the high-power solid-state laser facilities, contamination control focuses on the slab amplifiers, spatial filters, and final-optical assemblies. In this paper, an effective solution to control contaminations including the whole process of the laser driver is put forward to provide the safe operation of laser facilities, and the detailed technical methods of contamination control such as washing, cleanliness metrology, and cleanliness protecting are also introduced to reduce the probability of laser-induced damage of optics. The experimental results show that the cleanliness level of SG-III laser facility is much better to ensure that the laser facility can safely operate at high energy flux.

  11. Ultrasonic photoacoustic spectroscopy of trace hazardous chemicals using quantum cascade laser

    Science.gov (United States)

    Kumar, Deepak; Ghai, Devinder Pal; Soni, R. K.

    2016-12-01

    We report an ultrasonic sensor based on open-cell photoacoustic spectroscopy method for the detection of explosive agents in traces. Experimentally, we recorded photoacoustic spectra of traces of hazardous explosives and molecules. Tunable mid-infrared quantum cascade lasers in the wavelength range 7.0-8.8 μm lying in the molecular fingerprint region are used as optical source. Samples of Pentaerylthirol Tetranitrate (PETN), Tetranitro-triazacyclohexane (RDX), Dinitrotoluene, p-Nitrobenzoic acid and other chemicals like Ibuprofen having quantity 1.0 mg were detected using a custom made photoacoustic cells in both open and closed configurations. The explosive traces were swiped using paper from contaminated surface and detected. Finite element mesh based simulation of photoacoustic cell is carried out for optimization of geometry at ultrasonic frequency (40 kHz). A point sensor based on above approach will be very effective for forensic applications and suspicious material screening.

  12. Controlling Chaos in a Semiconductor Laser via Weak Optical Positive Feedback and Modulating Amplitude

    Institute of Scientific and Technical Information of China (English)

    YAN Sen-Lin

    2007-01-01

    Numerical analysis of weak optical positive feedback (OPF) controlling chaos is studied in a semiconductor laser.The physical model of controlling chaos produced via modulating the current of semiconductor laser is presented under the condition of OPF.We find the physical mechanism that the nonlinear gain coefficient and linewidth enhancement factor of the laser are affected by OPF so that the dynamical behaviour of the system can be efficiently controlled.Chaos is controlled into a single-periodic state,a dual-periodic state,a fri-periodic state,a quadr-periodic state,a pentaperiodic state,and the laser emitting powers are increased by OPF in simulations.Lastly,another chaos-control method with modulating the amplitude of the feedback light is presented and numerically simulated to control chaotic laser into multi-periodic states.

  13. Chemical, morphological and chromatic behavior of mural paintings under Er:YAG laser irradiation

    Science.gov (United States)

    Striova, J.; Camaiti, M.; Castellucci, E. M.; Sansonetti, A.

    2011-08-01

    Several pigments (malachite CuCO3ṡCu(OH)2, azurite 2CuCO3ṡCu(OH)2, yellow ochre (goethite α-FeOOH, gypsum CaSO4ṡ2H2O), St. John's white CaCO3 formed from slaked lime) and respective mural paintings specimens were subjected to the free-running Er:YAG laser radiation in order to study their damage thresholds, in a broad range of laser fluences, both in dry and wet conditions. The specimens' damage thresholds were evaluated by spectroscopic methods, colorimetric measurements and microscopic observation. The pigments containing -OH groups were found to be more sensitive than St. John's white; hence the most sensitive paint layers in dry conditions are those containing malachite, azurite (both 1.3 J/cm2) and yellow ochre (2.5 J/cm2) as compared to the ones containing St. John's white (15.2 J/cm2). The presence of wetting agents (w.a.) attenuated the pigments chemical alteration. The damage thresholds of all the paint layers, in presence of w.a., were found to be around 2.5 J/cm2. The alteration was caused by thermo-mechanical damage and by binding medium ablation of a fresco and a secco prepared specimens, respectively.

  14. Colour and chemical changes of the lime wood surface due to CO2 laser thermal modification

    Science.gov (United States)

    Kubovský, Ivan; Kačík, František

    2014-12-01

    We studied colour and main wood components changes of lime wood caused by CO2 laser beam irradiation. The dry surface of lime wood (Tilia vulgaris L.) was irradiated with the CO2 laser beam (wavelength of 10.6 μm) at different exposures (expressed as the irradiation dose). Colour changes were monitored by the spectrophotometer, chemical changes were observed by the ATR-FTIR spectroscopy and carbohydrates were analysed by the HPLC method. With the growth of the irradiation dose (from 8.1 to 28.7 J cm-2) lightness (ΔL*) decrease and increase of the total colour difference (ΔE*) were observed. Higher values of the input energy lead to accelerating the mutual reaction of the functional groups resulting in the subsequent condensation of lignin. The total decrease in saccharides at the highest irradiation dose reaches 27.39% of the initial amount of saccharides in the reference sample. We have observed degradation and loss of hemicelluloses.

  15. Quantum control and entanglement in a chemical compass

    CERN Document Server

    Cai, Jianming; Briegel, Hans J

    2009-01-01

    The radical pair mechanism is one of the two main hypotheses to explain the navigability of animals in weak magnetic fields, enabling e.g. birds to see the Earth's magnetic field. We show how quantum control can be used to either enhance or reduce the performance of such a chemical compass, providing a route to further test this hypothesis experimentally. We investigate the dynamics of quantum entanglement in this model, and demonstrate intriguing connections between radical-pair entanglement and the magnetic field sensitivity of the compass. The nature of the nuclear-spin environment plays an essential role for the observed effects.

  16. Can Chemical Mouthwash Agents Achieve Plaque/Gingivitis Control?

    Science.gov (United States)

    Van der Weijden, Fridus A; Van der Sluijs, Eveline; Ciancio, Sebastian G; Slot, Dagmar E

    2015-10-01

    Also note that structured abstracts are not allowed per journal style: What is the effect of a mouthwash containing various active chemical ingredients on plaque control and managing gingivitis in adults based on evidence gathered from existing systematic reviews? The summarized evidence suggests that mouthwashes containing chlorhexidine(CHX) and essential oils (EO) had a large effect supported by a strong body of evidence. Also there was strong evidence for a moderate effect of cetylpyridinium chloride(CPC). Evidence suggests that a CHX mouthwash is the first choice, the most reliable alternative is EO. No difference between CHX and EO with respect to gingivitis was observed.

  17. Using Chemicals to Optimize Conformance Control in Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Seright, Randall S.; Liang, Jenn-Tai; Schrader, Richard; Hagstrom II, John; Wang, Ying; Kumar, Ananad; Wavrik, Kathryn

    2001-10-29

    This report describes work performed during the third and final year of the project, Using Chemicals to Optimize Conformance Control in Fractured Reservoirs. This research project had three objectives. The first objective was to develop a capability to predict and optimize the ability of gels to reduce permeability to water more than that to oil or gas. The second objective was to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems. The third objective was to develop procedures to optimize blocking agent placement in naturally fractured reservoirs.

  18. Upgrading NASA/DOSE laser ranging system control computers

    Science.gov (United States)

    Ricklefs, Randall L.; Cheek, Jack; Seery, Paul J.; Emenheiser, Kenneth S.; Hanrahan, William P., III; Mcgarry, Jan F.

    1993-01-01

    Laser ranging systems now managed by the NASA Dynamics of the Solid Earth (DOSE) and operated by the Bendix Field Engineering Corporation, the University of Hawaii, and the University of Texas have produced a wealth on interdisciplinary scientific data over the last three decades. Despite upgrades to the most of the ranging station subsystems, the control computers remain a mix of 1970's vintage minicomputers. These encompass a wide range of vendors, operating systems, and languages, making hardware and software support increasingly difficult. Current technology allows replacement of controller computers at a relatively low cost while maintaining excellent processing power and a friendly operating environment. The new controller systems are now being designed using IBM-PC-compatible 80486-based microcomputers, a real-time Unix operating system (LynxOS), and X-windows/Motif IB, and serial interfaces have been chosen. This design supports minimizing short and long term costs by relying on proven standards for both hardware and software components. Currently, the project is in the design and prototyping stage with the first systems targeted for production in mid-1993.

  19. Laser-error-correction control unit for machine tools

    Energy Technology Data Exchange (ETDEWEB)

    Burleson, R.R.

    1978-05-23

    An ultraprecision machining capability is needed for the laser fusion program. For this work, a precision air-bearing spindle has been mounted horizontally on a modified vertical column of a Moore Number 3 measuring machine base located in a development laboratory at the Oak Ridge Y-12 Plant. An open-loop control system previously installed on this machine was inadequate to meet the upcoming requirements since accuracy is limited to 0.5 ..mu..m by the errors in the machine's gears and leadscrew. A new controller was needed that could monitor the actual position of the machine and perform real-time error correction on the programmed tool path. It was necessary that this project: (1) attain an optimum tradeoff between hardware and software; (2) use a modular design for easy maintenance; (3) use a standard NC tape service; (4) drive the x and y axes with a positioning resolution of 5.08 nm and a feedback resolution of 10 nm; (5) drive the x and y axis motors at a velocity of 0.05 cm/sec in the contouring mode and 0.18 cm/sec in the positioning mode; (6) eliminate the possibility of tape-reader errors; and (7) allow editing of the part description data. The work that was done to develop and install the new machine controller is described.

  20. Control of light backscattering in blood during intravenous laser irradiation

    Science.gov (United States)

    Melnik, Ivan S.; Popov, V. D.; Rusina, Tatyana V.; Dets, Sergiy M.

    1997-02-01

    One of the most important problems in modern laser medicine is the determination of system response on laser treatment. Reaction of living system is significant during many kinds of laser procedures like surgery, therapy and biostimulation. Our study was aimed to optimize laser exposure using feed-back fiber system for intravenous laser irradiation of blood (ILIB). This system consisted of helium-neon laser (633 nm, 5 mW) with coupled fiber unit, photodetector and PC interface. Photodetector signals produced due to light backscattering were storaged and processed during all blood irradiation procedure. Significant time-dependent variations were observed within 9-15 min after beginning of treatment procedure and were correlated with number of trials, stage and character of disease. The designed feed-back system allows us to register a human blood response on laser irradiation to achieve better cure effect.

  1. Accuracy of navigated control concepts using an Er: Yag-laser for cavity preparation.

    Science.gov (United States)

    Wolff, Regine; Weitz, Jochen; Poitzsch, Luise; Hohlweg-Majert, Bettina; Deppe, Herbert; Lueth, Tim C

    2011-01-01

    This paper describes a method for measuring the shape accuracy of a cylindrical hole which is created by means of an automatically power-controlled laser system using navigated control. In dental surgery, drills or mills are used for bone treatment. For most patients the use of these instruments is very inconvenient. Furthermore, the bone treatment with rotating instruments can lead to thermal necrosis. Using a laser system could be a good alternative for the patient. The utilization of a laser system could also facilitate bone treatment without any severe thermal damage. An optical navigation system can be used for a safer handling of a laser system. The position and the orientation of the laser handpiece relative to the patient can be calculated. Thereby, the laser can be automatically switched off, if the end of the laser beam does not hit the preoperative planned area. In order to measure the accuracy of such a laser system, we created several cavities in a phantom with a manually guided, automatically power-controlled laser. Afterwards, the deviation between the planned shape and the shape created by manually guided automatically power-controlled laser treatment has been measured. The application of this system showed, that the required accuracy of <1 mm for dental implantology applications, could not be reached.

  2. Tattoo pigments are cleaved by laser light-the chemical analysis in vitro provide evidence for hazardous compounds.

    Science.gov (United States)

    Vasold, Rudolf; Naarmann, Natascha; Ulrich, Heidi; Fischer, Daniela; König, Burkhard; Landthaler, Michael; Bäumler, Wolfgang

    2004-01-01

    In the western world, more than 80 million people decorate their skin with tattoos. Tattoo colorants are injected into the skin, like medical drugs. Most tattoo colorants are industrial pigments, and chemical industries have never produced them for human use but only to stain consumer goods. Up to 10% of tattooed people request removal of their tattoos because of an improved self-image or social stigmatization. In contrast to tattooing, physicians usually perform the tattoo removal. For that purpose laser light at very high intensities irradiates the skin to destroy the tattoo pigments. Based on a recent analysis of tattoo pigments, two widely used azo compounds were irradiated in suspension with laser and subsequently analyzed by using quantitative high-performance liquid chromatography and mass spectrometry. The high laser intensities cleaved the azo compounds, leading to an increase of decomposition products such as 2-methyl-5-nitroaniline, 2-5-dichloraniline and 4-nitro-toluene, which are toxic or even carcinogenic compounds. Moreover, the results of the chemical analysis show that the tattoo colorants already contain such compounds before laser irradiation. Because of a high number of patients undergoing laser treatment of tattoos and based on the results of our findings in vitro, it is an important goal to perform a risk assessment in humans regarding laser-induced decomposition products.

  3. Effects of high-repetition-rate femtosecond laser micromachining on the physical and chemical properties of polylactide (PLA).

    Science.gov (United States)

    Jia, Wei; Luo, Yiming; Yu, Jian; Liu, Bowen; Hu, Minglie; Chai, Lu; Wang, Chingyue

    2015-10-19

    The effects of femtosecond laser ablation, with 115 fs pulses at 1040 nm wavelength and 57 MHz repetition-rate, on the physical and chemical properties of polylactide (PLA) were studied in air and in water. The surface of the PLA sample ablated by high-repetition-rate femtosecond laser was analysed using field emission scanning electron microscopy, infrared spectroscopy, raman spectroscopy, as well as X-ray photoelectron spectroscopy. Compared with the experiments in the air at ambient temperature, melting resolidification was negligible for the experiments conducted under water. Neither in air nor under water did oxidation and crystallization process take place in the laser ablated surface. In addition, the intensity of some oxygen related peaks increased for water experiments, probably due to the hydrolysis. Meantime, the chemical shift to higher energies appeared in C1s XPS spectrum of laser processing in water. Interestingly, a large amount of defects were observed after laser processing in air, while no significant change was shown under water experiments. This indicates that thermal and mechanical effects by high-repetition-rate femtosecond laser ablation in water are quite limited, which could be even ignored.

  4. A non-chemical system for online weed control.

    Science.gov (United States)

    Rueda-Ayala, Victor; Peteinatos, Gerassimos; Gerhards, Roland; Andújar, Dionisio

    2015-03-30

    Non-chemical weed control methods need to be directed towards a site-specific weeding approach, in order to be able to compete the conventional herbicide equivalents. A system for online weed control was developed. It automatically adjusts the tine angle of a harrow and creates different levels of intensity: from gentle to aggressive. Two experimental plots in a maize field were harrowed with two consecutive passes. The plots presented from low to high weed infestation levels. Discriminant capabilities of an ultrasonic sensor were used to determine the crop and weed variability of the field. A controlling unit used ultrasonic readings to adjust the tine angle, producing an appropriate harrowing intensity. Thus, areas with high crop and weed densities were more aggressively harrowed, while areas with lower densities were cultivated with a gentler treatment; areas with very low densities or without weeds were not treated. Although the weed development was relatively advanced and the soil surface was hard, the weed control achieved by the system reached an average of 51% (20%-91%), without causing significant crop damage as a result of harrowing. This system is proposed as a relatively low cost, online, and real-time automatic harrow that improves the weed control efficacy, reduces energy consumption, and avoids the usage of herbicide.

  5. Use of external cavity quantum cascade laser compliance voltage in real-time trace gas sensing of multiple chemicals

    Energy Technology Data Exchange (ETDEWEB)

    Phillips, Mark C.; Taubman, Matthew S.; Kriesel, Jason M.

    2015-02-08

    We describe a prototype trace gas sensor designed for real-time detection of multiple chemicals. The sensor uses an external cavity quantum cascade laser (ECQCL) swept over its tuning range of 940-1075 cm-1 (9.30-10.7 µm) at a 10 Hz repetition rate.

  6. Controlling the Orientation and Alignment of Reagent Molecules by a Polarized Laser

    Institute of Scientific and Technical Information of China (English)

    丛书林; 韩克利; 楼南泉

    2003-01-01

    The expressions used for controlling the alignment and orientation of reagent molecules are derived. The problem to the control of the orientation and alignment of reagent molecules by the polarization direction and propagation direction of laser is discussed.

  7. Fragmentation Control of a Polyatomic Molecule by fully determined Laser-Fields

    Directory of Open Access Journals (Sweden)

    Varga K.

    2013-03-01

    Full Text Available Strong-field control of acetylene fragmentation by fully determined few-cycle laser pulses is demonstrated. The control mechanism is shown to be based on electron recollision and inelastic ionization from inner-valence molecular orbitals.

  8. Development of real-time monitoring and control in COIL laser cutting for joint R and D between Korea and U.S

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Chin Man; Kim, Cheol Jung; Kim, Min Suk; Baik, Sung Hoon; Kwon, Sung Ok; Park, Sun Kyu

    2000-12-01

    The laser monitoring and control technique investigated to experiment for cutting kerf width and result of laser cutting for D and D of nuclear facility. The demands for this laser monitoring and control technique were applied to process control in laser cutting and to fabricate monitoring and control system, focusing lens assembly. This system can had a advantage to monitor and control the laser cutting on real time. KAERI investigated the COIL laser and monitored 2 kW laser power.

  9. Control of optical and electrical properties of ZnO nanocrystals by nanosecond-laser annealing

    Science.gov (United States)

    Shimogaki, T.; Ofuji, T.; Tetsuyama, N.; Kawahara, H.; Higashihata, M.; Ikenoue, H.; Nakamura, D.; Okada, T.

    2014-03-01

    Effects of laser annealing on electrical and optical properties of Zinc oxide (ZnO) nanocrystals, which are expected as building blocks for optoelectronic devices, have been investigated in this study. In the case of fabricating p-n junction in single one-dimensional ZnO nanocrystal, phosphorus-ions implanted p-type ZnO nanocrystals were recrystallized and recovered in the optical properties by nanosecond-laser annealing using a KrF excimer laser. Antimony-doped p-type ZnO nanocrystals were synthesized by irradiating laminated structure which antimony thin film were deposited on ZnO nanocrystals with the laser beam. Additionally, it is possible to control the growth rate of ZnO nanowires by using laser annealing. Irradiating with pulsed laser a part of ZnO buffer layer deposited on the a-cut sapphire substrate, then ZnO nanowires were grown on the ZnO buffer layer by the nanoparticle assisted pulsed laser deposition method. As a result, the clear boundary of the laser annealed and non-laser annealed area was appeared. It was observed that ZnO nanowires were grown densely at non-laser annealed area, on the other hand, sparse ones were grown at the laser-annealed region. In this report, the possibility of laser annealing techniques to establish the stable and reliable fabrication process of ZnO nanowires-based LD and LED are discussed on the basis of experimental results.

  10. Lasers in tattoo and pigmentation control: role of the PicoSure® laser system

    Directory of Open Access Journals (Sweden)

    Torbeck R

    2016-05-01

    Full Text Available Richard Torbeck,1 Richard Bankowski,2 Sarah Henize,3 Nazanin Saedi,11Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 2Cynosure, Inc, Westford, MA, 3Huron Consulting Group, Chicago, IL, USABackground and objectives: The use of picosecond lasers to remove tattoos has greatly improved due to the long-standing outcomes of nanosecond lasers, both clinically and histologically. The first aesthetic picosecond laser available for this use was the PicoSure® laser system (755/532 nm. Now that a vast amount of research on its use has been conducted, we performed a comprehensive review of the literature to validate the continued application of the PicoSure® laser system for tattoo removal.Study design and methods: A PubMed search was conducted using the term "picosecond" combined with "laser", "dermatology", and "laser tattoo removal".Results: A total of 13 articles were identified, and ten of these met the inclusion criteria for this review. The majority of studies showed that picosecond lasers are an effective and safe treatment mode for the removal of tattoo pigments. Several studies also indicated potential novel applications of picosecond lasers in the removal of various tattoo pigments (eg, black, red, and yellow. Adverse effects were generally mild, such as transient hypopigmentation or blister formation, and were rarely more serious, such as scarring and/or textural change.Conclusion: Advancements in laser technologies and their application in cutaneous medicine have revolutionized the field of laser surgery. Computational modeling provides evidence that the optimal pulse durations for tattoo ink removal are in the picosecond domain. It is recommended that the PicoSure® laser system continue to be used for safe and effective tattoo removal, including for red and yellow pigments.Keywords: tattoo, removal, laser, picosecond 

  11. Controlling laser beam irradiation area using an optical duplicate system to improve satellite-ground laser communications

    Science.gov (United States)

    Nakayama, Tomoko; Takayama, Yoshihisa; Fujikawa, Chiemi; Kodate, Kashiko

    2016-08-01

    To improve the quality of ground to satellite laser communications, we propose an optical duplicate system of the optical ground station. Our proposed approach can be used to control the beam irradiation area for a satellite position without changing the total power of the output beam and the mechanical drive unit; this is performed by controlling the input pattern of a liquid crystal filter inserted in the input plane of the optical duplicate system. Most of the power of the diffracted laser beam emitted from the ground is focused on the optical axis. By distributing the power to side lobes, it is possible to extend the coverage area for a satellite position. This system allows the laser beam irradiation area to be controlled by a sufficient degree by adjusting the threshold of the satellite reception level. We verify the efficacy of the system using wave optics numerical calculations.

  12. Time-Delayed Feedback Control in a Single-Mode Laser System

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The effects of time-delayed feedback control in a single-mode laser system is investigated. Using the small time delay approximation, the analytic expression of the stationary probability distribution function of the laser field is obtaincd. The mean, normalized variance and skewness of the steady-state laser intensity are calculated. It is found that the time-delayed feedback control can suppress the intensity fluctuation of the laser system. The numerical simulations are in good agreement with the approximate analytic results.

  13. Laser controlled melting of pre-treated zirconia surface

    Energy Technology Data Exchange (ETDEWEB)

    Yilbas, B.S., E-mail: bsyilbas@kfupm.edu.sa [ME Department, KFUPM, Dhahran 31261, (Saudi Arabia); Akhtar, S.S. [ME Department, KFUPM, Dhahran 31261, (Saudi Arabia); Karatas, C. [Engineering College, Hacettepe University, (Turkey)

    2011-05-15

    Laser treatment of pre-prepared zirconia surface is carried out. The pre-prepared surface, prior to laser treatment, consists of 50 {mu}m carbon film and 7% titanium carbide particles, which are imbedded in the carbon film. The microstructural and morphological changes in the laser treated surface layer are examined using optical and scanning electron microscopes, energy dispersive spectroscopy, and X-ray diffraction. The fracture toughness of the laser treated surface is measured and the residual stress formed at the surface vicinity is determined from the X-ray diffraction technique. It is found that the microhardness of the laser treated surface increased slightly due to the dense layer formed at the surface vicinity. However, the laser treatment process reduces the fracture toughness of the surface due to improved surface hardness and the residual stress formed in the surface vicinity.

  14. Provenance control on chemical indices of weathering (Taiwan river sands)

    Science.gov (United States)

    Garzanti, Eduardo; Resentini, Alberto

    2016-05-01

    Geochemical parameters obtained from the analysis of sediments and sedimentary rocks are widely used to infer weathering and paleo-weathering conditions in source areas. Chemical indices of weathering, however, may not reflect weathering only, or even principally. The concentration of chemical elements in terrigenous sediments is constrained by the original mineralogy of source rocks, and is thus provenance-dependent. Moreover, the mineralogy and consequently the geochemistry of sediments may undergo substantial modifications by diverse physical processes during transport and deposition, including recycling and hydraulic sorting by size, density or shape, and/or by chemical dissolution and precipitation during diagenesis. Around the island of Taiwan, temperature and rainfall are consistently high and relatively homogeneous, and no significant correlation is observed between geochemical and climatic parameters. Physical erosion, fostered by landslides induced by frequent earthquakes and typhoons, prevails because of high relief and extreme rates of tectonic uplift. In such a dynamic orogenic setting, all chemical indices of weathering are controlled principally by the geology of source terranes. Sedimentaclastic and metasedimentaclastic sands carried by western Taiwan rivers draining the pro-wedge display the strongest depletion in Na, Ca, Mg and Sr relative to average upper continental crust, and no depletion or even enrichment in K, Rb and Ba. Low WIP indices reflect erosion of phyllosilicate-dominated rocks in the Slate Belt and extensive recycling of clastic rocks exposed in the Western Foothills. Instead, metamorphiclastic sands carried by eastern Taiwan rivers draining the retro-wedge show no depletion or even enrichment in Mg and Ca, and low CIA and PIA, reflecting contributions from the Tailuko Belt and Coastal Range. Volcaniclastic sands have the same CIA values of their andesitic source rocks (47 ± 1 versus 47 ± 7), indicating that weathering is

  15. A Polymer Film Dye Laser with Spatially Modulated Emission Controlled by Transversely Distributed Pumping

    Directory of Open Access Journals (Sweden)

    Zurab V. Wardosanidze

    2016-01-01

    Full Text Available Spatial modulation of laser emission controlled by the structure of excitation light field was demonstrated. A dye doped polymer film as an active medium was sandwiched between two laser mirrors forming a laser cell. The pumping was performed by an interference pattern formed with two mutually coherent beams of the second harmonic of a Q-switched Nd:YAG laser (532 nm and located in the plane of the laser cell. The laser emission was observed normally on the plane of the cell. The cross section of the obtained laser emission was modulated in intensity with an interval between maximums depending on the period of the pumping interference pattern. Thus, the emitted light field qualitatively looks like diffraction from an elementary dynamic hologram, that is, a holographic diffraction grating.

  16. Carbon nanotubes grown by catalytic CO 2 laser-induced chemical vapor deposition on core-shell Fe/C composite nanoparticles

    Science.gov (United States)

    Morjan, I.; Soare, I.; Alexandrescu, R.; Gavrila-Florescu, L.; Morjan, R.-E.; Prodan, G.; Fleaca, C.; Sandu, I.; Voicu, I.; Dumitrache, F.; Popovici, E.

    2008-01-01

    The synthesis of carbon nanotubes (CNTs) by catalytic laser-induced chemical vapor deposition (C-LCVD) was investigated. C-LCVD uses both ex situ synthesized catalyst nanoparticles and the controlled decomposition of gas-phase hydrocarbon mixtures. As catalysts, Fe/C composites of the core-shell type were used. A continuous-wave CO 2 laser was employed to irradiate the ethylene/acetylene hydrocarbon precursors and to simultaneously heat a silicon substrate on which the carbon nanotubes were grown. The effects on carbon nanotube growth of both the iron-based nanocomposite particles and of the ethylene concentration were studied. The analysis suggests the feasibility of the C-LCVD process, in which the core-shell Fe/C catalysts comply with the prerequisite conditions of the CNT growth namely dispersion and supersaturation.

  17. Determination of metformin in mouse, rat, dog and human plasma samples by laser diode thermal desorption/atmospheric pressure chemical ionization tandem mass spectrometry.

    Science.gov (United States)

    Swales, John G; Gallagher, Richard; Peter, Raimund M

    2010-11-02

    A simple, rapid and robust high-throughput assay for the quantitative analysis of metformin in plasma from different species using laser diode thermal desorption interfaced with atmospheric chemical pressure ionization tandem mass spectrometry (LDTD-APCI-MSMS) was developed for use in a pharmaceutical discovery environment. In order to minimize sample preparation a generic protein precipitation method was used to extract metformin from the plasma. Laser diode thermal desorption is a relatively new sample introduction method, the optimization of the instrumental parameters are presented. The method was successfully applied to spiked mouse, rat, dog and human plasma samples and was subsequently used to determine the oral pharmacokinetics of metformin after dosing to male rats in order to support drug discovery projects. The deviations for intra-assay accuracy and precision across the four species were less than 30% at all calibration and quality control levels.

  18. Surface micro- and nano-texturing of stainless steel by femtosecond laser for the control of cell migration

    Science.gov (United States)

    Martínez-Calderon, M.; Manso-Silván, M.; Rodríguez, A.; Gómez-Aranzadi, M.; García-Ruiz, J. P.; Olaizola, S. M.; Martín-Palma, R. J.

    2016-11-01

    The precise control over the interaction between cells and the surface of materials plays a crucial role in optimizing the integration of implanted biomaterials. In this regard, material surface with controlled topographic features at the micro- and nano-scales has been proved to affect the overall cell behavior and therefore the final osseointegration of implants. Within this context, femtosecond (fs) laser micro/nano machining technology was used in this work to modify the surface structure of stainless steel aiming at controlling cell adhesion and migration. The experimental results show that cells tend to attach and preferentially align to the laser-induced nanopatterns oriented in a specific direction. Accordingly, the laser-based fabrication method here described constitutes a simple, clean, and scalable technique which allows a precise control of the surface nano-patterning process and, subsequently, enables the control of cell adhesion, migration, and polarization. Moreover, since our surface-patterning approach does not involve any chemical treatments and is performed in a single step process, it could in principle be applied to most metallic materials.

  19. Lasers in tattoo and pigmentation control: role of the PicoSure® laser system

    OpenAIRE

    2016-01-01

    Richard Torbeck,1 Richard Bankowski,2 Sarah Henize,3 Nazanin Saedi,11Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA, 2Cynosure, Inc, Westford, MA, 3Huron Consulting Group, Chicago, IL, USABackground and objectives: The use of picosecond lasers to remove tattoos has greatly improved due to the long-standing outcomes of nanosecond lasers, both clinically and histologically. The first aesthetic picosecond laser availa...

  20. Hierarchical tree-structured control network for the Antares laser facility

    Energy Technology Data Exchange (ETDEWEB)

    McGirt, F.

    1979-01-01

    The design and implementation of a distributed, computer-based control system for the Antares 100-kJ gas laser fusion facility is presented. Control system requirements and their operational interrelationships that consider both integrated system control and individual subsystem control are described. Several configurations of minicomputers are established to provide direct control of sets of microcomputers and to provide points of operator-laser interaction. Over 100 microcomputers are located very close to the laser device control points or sources of data and perform the real-time functions of the control system, such as data and control signal multiplexing, stepping motor control, and vacuum and gas system control. These microcomputers are designed to be supported as an integral part of the control network and to be software compatible with the larger minicomputers.

  1. Development of multiple laser frequency control system for Ca{sup +} isotope ion cooling

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Kyunghun, E-mail: jung@lyman.q.t.u-tokyo.ac.jp [The University of Tokyo, Nuclear Professional School (Japan); Yamamoto, Yuta, E-mail: yamamoto@lyman.q.t.u-tokyo.ac.jp [The University of Tokyo, Department of Nuclear Engineering and Management (Japan); Hasegawa, Shuichi, E-mail: hasegawa@tokai.t.u-tokyo.ac.jp [The University of Tokyo, Nuclear Professional School (Japan)

    2015-11-15

    We here developed and evaluated a laser frequency control system which synchronizes the laser frequency to the resonance of target Ca {sup +} isotope ion whose having more than 8 GHz of isotope shift based on the Fringe Offset Lock method for simple operation of ICPMS-ILECS (Inductively Coupled Plasma Mass Spectrometry - Ion trap Laser Cooling Spectroscopy) The system fulfilled the minimum requirements of four slave lasers stability for Doppler cooling of Ca {sup +} ions. A performance of the system was evaluated by cooling {sup 40}Ca {sup +} ions with the stabilized slave lasers. All the stable even Ca {sup +} isotope ions were trapped and their fluorescence was observed by switching laser frequencies using the system. An odd calcium isotope {sup 43}Ca {sup +}cooling was also succeeded by the control system.

  2. Physico-chemical and Bio-chemical Controls on Soil C Saturation Behavior

    Energy Technology Data Exchange (ETDEWEB)

    Six, Johan [Univ. of California, Davis, CA (United States); Plante, Alain F. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    2011-05-31

    In this project, we tested through a multitude of lab and field experiments the concept of soil C stabilization and determined metrics for the level of C saturation across soils and soil organic matter fractions. The basic premise of the soil C saturation concept is that there is a maximum amount of C that can be stabilized within a soil, even when C input is further increased. In a first analysis, our results showed that linear regression models do not adequately predict maximal organic C stabilization by fine soil particles. Soil physical and chemical properties associated with soil clay mineralogy, such as specific surface area and organic C loading, should be incorporated into models for predicting maximal organic C stabilization. In a second analysis, we found significantly greater maximal C stabilization in the microaggregate-protected versus the non-microaggregate protected mineral fractions, which provides independent validation that microaggregation plays an important role in increasing the protection and stabilization of soil C leading to greater total soil C accumulation in these pools. In a third study, our results question the role of biochemical preference in mineral C stabilization and of the chemical recalcitrance of specific plant-derived compounds in non-protected soil C accumulation. Because C biochemical composition of slowly turning over mineral protected C pools does not change with C saturation, input C composition is unlikely to affect long-term C stabilization. Rather, C saturation and stabilization in soil is controlled only by the quantity of C input to the soil and the physical and chemical protection mechanisms at play in long-term C stabilization. In conclusion, we have further corroborated the concept of soil C saturation and elucidated several mechanisms underlying this soil C saturation.

  3. Towards benchmarking of multivariable controllers in chemical/biochemical industries: Plantwide control for ethylene glycol production

    DEFF Research Database (Denmark)

    Huusom, Jakob Kjøbsted; Bialas, Dawid Jan; Jørgensen, John Bagterp

    2011-01-01

    In this paper we discuss a simple yet realistic benchmark plant for evaluation and comparison of advanced multivariable control for chemical and biochemical processes. The benchmark plant is based on recycle-separator-recycle systems for ethylene glycol production and implemented in Matlab...

  4. Lasers in tattoo and pigmentation control: role of the PicoSure® laser system

    Science.gov (United States)

    Torbeck, Richard; Bankowski, Richard; Henize, Sarah; Saedi, Nazanin

    2016-01-01

    Background and objectives The use of picosecond lasers to remove tattoos has greatly improved due to the long-standing outcomes of nanosecond lasers, both clinically and histologically. The first aesthetic picosecond laser available for this use was the PicoSure® laser system (755/532 nm). Now that a vast amount of research on its use has been conducted, we performed a comprehensive review of the literature to validate the continued application of the PicoSure® laser system for tattoo removal. Study design and methods A PubMed search was conducted using the term “picosecond” combined with “laser”, “dermatology”, and “laser tattoo removal”. Results A total of 13 articles were identified, and ten of these met the inclusion criteria for this review. The majority of studies showed that picosecond lasers are an effective and safe treatment mode for the removal of tattoo pigments. Several studies also indicated potential novel applications of picosecond lasers in the removal of various tattoo pigments (eg, black, red, and yellow). Adverse effects were generally mild, such as transient hypopigmentation or blister formation, and were rarely more serious, such as scarring and/or textural change. Conclusion Advancements in laser technologies and their application in cutaneous medicine have revolutionized the field of laser surgery. Computational modeling provides evidence that the optimal pulse durations for tattoo ink removal are in the picosecond domain. It is recommended that the PicoSure® laser system continue to be used for safe and effective tattoo removal, including for red and yellow pigments. PMID:27194919

  5. Controlled oxidation of iron nanoparticles in chemical vapour synthesis

    Science.gov (United States)

    Ruusunen, Jarno; Ihalainen, Mika; Koponen, Tarmo; Torvela, Tiina; Tenho, Mikko; Salonen, Jarno; Sippula, Olli; Joutsensaari, Jorma; Jokiniemi, Jorma; Lähde, Anna

    2014-02-01

    In the present study, iron oxide nanoparticles (primary particle size of 80-90 nm) with controlled oxidation state were prepared via an atmospheric pressure chemical vapour synthesis (APCVS) method. Iron pentacarbonyl [Fe(CO)5], a precursor material, was thermally decomposed to iron in the APCVS reactor. Subsequently, the iron was oxidized with controlled amount of oxygen in the reactor to produce nearly pure magnetite or haematite particles depending on the oxygen concentration. Size, morphology and crystal structure of the synthesized nanoparticles were studied with scanning mobility particle sizer (SMPS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In addition, thermodynamic equilibrium calculations and computational fluid dynamics model were used to predict the oxidation state of the iron oxides and the reaction conditions during mixing. Aggregates of crystalline particles were formed, determined as magnetite at the oxygen volumetric fraction of 0.1 % and haematite at volumetric fraction of 0.5 %, according to the XRD. The geometric mean electrical mobility diameter of the aggregates increased from 110 to 155 nm when the volumetric fraction of oxygen increased from 0.1 to 0.5 %, determined using the SMPS. The aggregates were highly sintered based on TEM analyses. As a conclusion, APCVS method can be used to produce nearly pure crystalline magnetite or haematite nanoparticles with controlled oxidation in a continuous one-stage gas-phase process.

  6. Control of environmental impact with modern chemical technology

    Science.gov (United States)

    Hocking, Martin B.

    1986-03-01

    Here are assembled representative excerpts from a new text in applied chemistry. They illustrate the well-referenced treatment of industrial processes that are here considered with their related emission control problems and solutions. A brief account of general aspects of the industry is followed by surveys of the significance and technical aspects of air and water pollution chemistry. Consideration is given to emission avoidance or containment, waste treatment, and waste disposal options as they relate to both of these environmental areas. Details of salt recovery and the products of brine electrolysis plus environmental aspects of these operations are treated as examples of some of the processes discussed. Also covered are fertilizer constituent preparation, formulation, and use with consideration of the large-scale effects of each of these activities. Detailed reference is made to the chemical technology and emission control aspects of the pulp and paper industry and refinery operations. Throughout, integral process changes and waste recycling practices are directly related to emission control aspects of each process in a way to be useful to the student and professional alike. These excerpts are extracted from one of the first, single volume accounts to take this unified approach to the subject.

  7. Flow-Induced Control of Pattern Formation in Chemical Systems

    Science.gov (United States)

    Berenstein, Igal; Beta, Carsten

    Since Alan Turing's seminal paper in 1952, the study of spatio-temporal patterns that arise in systems of reacting and diffusing components has grown into an immense and vibrant realm of scientific research. This field includes not only chemical systems but spans many areas of science as diverse as cell and developmental biology, ecology, geosciences, or semiconductor physics. For several decades research in this field has concentrated on the vast variety of patterns that can emerge in reaction-diffusion systems and on the underlying instabilities. In the 1990s, stimulated by the pioneering work of Ott, Grebogi and Yorke, control of pattern formation arose as a new topical focus and gradually developed into an entire new field of research. On the one hand, research interests concentrated on control and suppression of undesired dynamical states, in particular on control of chaos. On the other hand, the design and engineering of particular space-time patterns became a major focus in this field that motivates ongoing scientific effort until today...

  8. Femtosecond laser pulses for chemical-free embryonic and mesenchymal stem cell differentiation

    Science.gov (United States)

    Mthunzi, Patience; Dholakia, Kishan; Gunn-Moore, Frank

    2011-10-01

    Owing to their self renewal and pluripotency properties, stem cells can efficiently advance current therapies in tissue regeneration and/or engineering. Under appropriate culture conditions in vitro, pluripotent stem cells can be primed to differentiate into any cell type some examples including neural, cardiac and blood cells. However, there still remains a pressing necessity to answer the biological questions concerning how stem cell renewal and how differentiation programs are operated and regulated at the genetic level. In stem cell research, an urgent requirement on experimental procedures allowing non-invasive, marker-free observation of growth, proliferation and stability of living stem cells under physiological conditions exists. Femtosecond (fs) laser pulses have been reported to non-invasively deliver exogenous materials, including foreign genetic species into both multipotent and pluripotent stem cells successfully. Through this multi-photon facilitated technique, directly administering fs laser pulses onto the cell plasma membrane induces transient submicrometer holes, thereby promoting cytosolic uptake of the surrounding extracellular matter. To display a chemical-free cell transfection procedure that utilises micro-litre scale volumes of reagents, we report for the first time on 70 % transfection efficiency in ES-E14TG2a cells using the enhanced green fluorescing protein (EGFP) DNA plasmid. We also show how varying the average power output during optical transfection influences cell viability, proliferation and cytotoxicity in embryonic stem cells. The impact of utilizing objective lenses of different numerical aperture (NA) on the optical transfection efficiency in ES-E14TG2a cells is presented. Finally, we report on embryonic and mesenchymal stem cell differentiation. The produced specialized cell types could thereafter be characterized and used for cell based therapies.

  9. Actively controlled tuning of an external cavity diode laser by polarization spectroscopy.

    Science.gov (United States)

    Führer, Thorsten; Stang, Denise; Walther, Thomas

    2009-03-30

    We report on an universal method to achieve and sustain a large mode-hop free tuning range of an external cavity diode laser. By locking one of the resonators using a closed loop control based on polarization spectroscopy while tuning the laser we achieved mode-hop free tuning of up to 130 GHz with a non AR-coated, off-the-shelf laser diode.

  10. Controlling quantum coherence of atom laser by light with strong strength

    Institute of Scientific and Technical Information of China (English)

    JING; Hui(景辉); GE; Molin(葛墨林); GE; Molin(葛墨林)

    2002-01-01

    A new method for controlling the quantum coherence of atom laser by applying input light with strong strength is presented within the framework of quantum dynamical theory. Unlike the case of rotating wave approximation(RWA), we show that the non-classical properties, such as sub-Poisson distribution and quadrature squeezed effect, can appear in the output atom laser beam with time. By choosing suitable initial RF phase, a steady and brighter output of squeezed coherent atom laser is also available.

  11. Towards Friction Control using laser-induced periodic Surface Structures

    NARCIS (Netherlands)

    Eichstädt, J.; Römer, G.R.B.E.; Huis in 't Veld, A.J.

    2011-01-01

    This paper aims at contributing to the study of laser-induced periodic surface structures (LIPSS) and the description of their tribological properties in order to facilitate the knowledge for contact mechanical applications. To obtain laser parameters for LIPSS formation, we propose to execute two D

  12. Using Chemicals to Optimize Conformance Control in Fractured Reservoirs

    Energy Technology Data Exchange (ETDEWEB)

    Seright, Randall S.; Liang, Jenn-Tai; Schrader, Richard; Hagstrom II, John; Liu, Jin; Wavrik, Kathryn

    1999-09-27

    This report describes work performed during the first year of the project, ''Using Chemicals to Optimize Conformance Control in Fractured Reservoirs.'' This research project has three objectives. The first objective is to develop a capability to predict and optimize the ability of gels to reduce permeability to water more than that to oil or gas. The second objective is to develop procedures for optimizing blocking agent placement in wells where hydraulic fractures cause channeling problems. The third objective is to develop procedures to optimize blocking agent placement in naturally fractured reservoirs. This research project consists of three tasks, each of which addresses one of the above objectives. Our work is directed at both injection wells and production wells and at vertical, horizontal, and highly deviated wells.

  13. [Application of chemical ecology in controlling marine fouling organisms].

    Science.gov (United States)

    Fang, Fang; Yan, Tao; Liu, Qing

    2005-10-01

    Many marine organisms can produce secondary metabolites beneficial to the protection of marine environments against fouling, and thus, applying chemo-ecological methods to extract the natural antifoulants from marine organisms to resolve the problems relevant to marine fouling is a new thinking in resent years. Its aim is to search for high efficient and non-toxic antifoulants to replace the existing chemically synthetic ones which are unfortunately found to have widespread toxic effects on marine environment. Although we know few about the antifouling mechanisms of secondary metabolites, many natural products have been proved to have antifouling activity. Therefore, basic and applied researches on the ecological roles of these natural compounds, their action mechanisms, coating compatibility, controlled release, and field test are required in the future.

  14. Note: Efficient diode laser line narrowing using dual, feed-forward + feed-back laser frequency control

    Science.gov (United States)

    Lintz, M.; Phung, D. H.; Coulon, J.-P.; Faure, B.; Lévèque, T.

    2017-02-01

    We have achieved distributed feedback laser diode line narrowing by simultaneously acting on the diode current via a feed-back loop and on an external electrooptic phase modulator in feed-forward actuator. This configuration turns out to be very efficient in reaching large bandwidth in the phase correction: up to 15 MHz with commercial laser control units. About 98% of the laser power undergoes narrowing. The full width at half maximum of the narrowed optical spectrum is of less than 4 kHz. This configuration appears to be very convenient as the delay in the feed-forward control electronics is easily compensated for by a 20 m optical fiber roll.

  15. Laser cooling and control of excitations in superfluid helium

    Science.gov (United States)

    Harris, G. I.; McAuslan, D. L.; Sheridan, E.; Sachkou, Y.; Baker, C.; Bowen, W. P.

    2016-08-01

    Superfluidity is a quantum state of matter that exists macroscopically in helium at low temperatures. The elementary excitations in superfluid helium have been probed with great success using techniques such as neutron and light scattering. However, measurements of phonon excitations have so far been limited to average thermodynamic properties or the driven response far out of thermal equilibrium. Here, we use cavity optomechanics to probe the thermodynamics of phonon excitations in real time. Furthermore, strong light-matter interactions allow both laser cooling and amplification. This represents a new tool to observe and control superfluid excitations that may provide insight into phonon-phonon interactions, quantized vortices and two-dimensional phenomena such as the Berezinskii-Kosterlitz-Thouless transition. The third sound modes studied here also offer a pathway towards quantum optomechanics with thin superfluid films, including the prospect of femtogram masses, high mechanical quality factors, strong phonon-phonon and phonon-vortex interactions, and self-assembly into complex geometries with sub-nanometre feature size.

  16. Influence of the Local Chemical Composition on the Mechanical Properties of Laser Beam Welded Al-Li Alloys

    Science.gov (United States)

    Enz, Josephin; Riekehr, Stefan; Ventzke, Volker; Kashaev, Nikolai

    The increasing interest of the aircraft industry in reduction of structural weight of aircrafts has resulted in the development of lightweight and high-strength Al-Li alloys as well as in the introduction of laser beam welding to the manufacturing process. The objective of this study is the investigation of the influence of variations in the chemical composition on local mechanical properties, like micro-hardness and micro-tensile strength, of CO 2 laser beam welded skin-stringer joints made from AA2196 and AA2198. Additionally the influence of the welding process on weld chemistry is studied in view of the improvement of the weld quality.

  17. Modeling of Flowing Plasmas and Pulse Power Schemes for O2(1Delta) Production for Chemical Lasers

    Science.gov (United States)

    2008-01-19

    Redistribution subject to AlP license or copyright, see http:l/jap.aip.org/jap/copyright.jsp 113306-11 Babaeva, Arakoni, and Kushner J. Appi . Phys. 99...Babaeva, and M. J. Kushner, J. Appl. ’W. E. McDermott, N R. Pchelkin, D. J. Benard. and R. R. Bousek, AppI . Phys. 98. 073304 (2t005). Phys. Lett. 32. 469...8217A. Elior, B. D. Barm,tsheniko, E. Lebiush, and S. Rosenwaks. AppI . Phys. Gas Flost and Chemical Las,ers and lligh Power Laser Conference tyro- B

  18. Controlling Laser-Driven Hohlraums-Clues from Experiments with Earlier Lasers

    Science.gov (United States)

    Kruer, William; Thomas, Cliff

    2015-11-01

    Better characterized and controlled hohlraums are very important for both implosion and science experiments on NIF. A brief review of some hohlraum and related experiments with earlier lasers is given to search for lessons learned and clues for better understanding NIF hohlraums. For example, surprises associated with heat transport inhibition and improved models for radiation generation have been a recurring theme in indirect drive experiments. In Shiva experiments, the hohlraum filling with plasma with density near quarter-critical was only calculated after inhibited heat transport and improved radiation models were adopted in the design code. Early NIF experiments also led to a change in the heat transport and radiation models. In this case, the heat transport model was changed from one with modest inhibition (which had been used to model Nova experiments) to near classical transport. Most recently, a design model invoking very inhibited transport (at various times and locations) has been proposed by C. Thomas for NIF hohlraums. Other recurring themes will also be discussed. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  19. Closed loop control of laser welding using an optical spectroscopic sensor for Nd:YAG and CO2 lasers

    NARCIS (Netherlands)

    Konuk, A.R.; Aarts, R.G.K.M.; Huis in 't Veld, A.J.; Sibillano, T.; Rizzi, D.; Ancona, A.

    2011-01-01

    Recent developments in laser joining show the applicability of spectral analysis of the plasma plume emission to monitor and control the quality of weld. The analysis of the complete spectra makes it possible to measure specific emission lines which reveal information about the welding process. The

  20. Laser speckle technique to study the effect of chemical pre-treatment on the quality of minimally processed apples

    Science.gov (United States)

    Minz, Preeti D.; Nirala, A. K.

    2016-04-01

    In the present study, the laser speckle technique has been used for the quality evaluation of chemically treated cut apples. Chemical pre-treatment includes 1% (w/v) solution of citric acid (CA), sodium chloride (SC), and a combination of CA and sodium chloride (CS). The variation in weight loss, respiration rate, total soluble solids (TSS), titratable acidity (TA), and absorbance of chemically treated cut apples stored at 5 °C was monitored for 11 d. The speckle grain size was calculated by an autocovariance method from the speckled images of freshly cut chemically treated apples. The effect of chemicals on TSS and the TA content variation of the cut apples were well correlated to the linear speckle grain size. Circular degree of polarization confirms the presence of a small scatterer and hence Rayleigh diffusion region. For all the treated cut apples, a decrease in the concentration of small particles nearly after the mid-period of storage results in the fast decay of circular degree of polarization. For non-invasive and fast analysis of the chemical constituent of fruits during minimal processing, the laser speckle can be practically used in the food industry.

  1. Start features of supersonic chemical laser (SCL) channel operating with pressure recovery system (PRS)

    Science.gov (United States)

    Boreysho, A. S.; Malkov, V. M.

    2007-05-01

    The particularity of start process of rectangular laser channel in comparison with star of wind tunnel - the state of understart - is discovered. The higher pressure level is realized in laser cavity as result of this phenomena and it brings to laser power decrease.

  2. A Self-Calibrating Remote Control Chemical Monitoring System

    Energy Technology Data Exchange (ETDEWEB)

    Jessica Croft

    2007-06-01

    The Susie Mine, part of the Upper Tenmile Mining Area, is located in Rimini, MT about 15 miles southwest of Helena, MT. The Upper Tenmile Creek Mining Area is an EPA Superfund site with 70 abandoned hard rock mines and several residential yards prioritized for clean up. Water from the Susie mine flows into Tenmile Creek from which the city of Helena draws part of its water supply. MSE Technology Applications in Butte, Montana was contracted by the EPA to build a treatment system for the Susie mine effluent and demonstrate a system capable of treating mine waste water in remote locations. The Idaho National Lab was contracted to design, build and demonstrate a low maintenance self-calibrating monitoring system that would monitor multiple sample points, allow remote two-way communications with the control software and allow access to the collected data through a web site. The Automated Chemical Analysis Monitoring (ACAM) system was installed in December 2006. This thesis documents the overall design of the hardware, control software and website, the data collected while MSE-TA’s system was operational, the data collected after MSE-TA’s system was shut down and suggested improvements to the existing system.

  3. Control of chemical reaction pathways by femtosecond ponderomotive forces: Time-resolved multiphoton ionization spectroscopic study of OCIO photodissociation

    Science.gov (United States)

    Blackwell, M.; Ludowise, P.; Chen, Y.

    1997-07-01

    Femtosecond time-resolved multiphoton ionization spectroscopy is applied to the study of the photodissociation of OClO. The observed ratio of O2+/ClO+ signal increases 12-fold with a 3-fold increase of the pump laser intensity. They are attributed to the change in the branching ratio between the two independent reaction channels leading to Cl+O2 and ClO+O, respectively. We believe this is the first experimental demonstration of laser controlled chemical reactions by femtosecond ponderomotive forces. At low pump power, the photodissociation dynamics at 386 nm is shown to be a two-step process, with the OClO slowly approaching (time constant 4.6 ps) a transition state that falls apart rapidly (time constant 250 fs).

  4. Laser controlled charge-transfer reaction at low temperatures

    CERN Document Server

    Petrov, Alexander; Kotochigova, Svetlana

    2016-01-01

    We study the low-temperature charge transfer reaction between a neutral atom and an ion under the influence of near-resonant laser light. By setting up a multi-channel model with field-dressed states we demonstrate that the reaction rate coefficient can be enhanced by several orders of magnitude with laser intensities of $10^6$ W/cm$^2$ or larger. In addition, depending on laser frequency one can induce a significant enhancement or suppression of the charge-exchange rate coefficient. For our intensities multi-photon processes are not important.

  5. Programmable Control of the Pulse Repetition Rate in the Multiwave Strontium Vapor Laser System

    Directory of Open Access Journals (Sweden)

    Soldatov Anatoly

    2016-01-01

    Full Text Available The aim of the present work was the development of laser systems for ablation of biological tissues with a programmable control over the lasing pulse repetition rate in a wide range. A two-stage laser system consisting of a master oscillator and a power amplifier based on strontium vapor laser has been developed. The operation of the laser system in a single-pulse mode operation, multipulse mode operation, and with a pulse repetition rate up to 20 kHz has been technically implemented. The possibility of a bone tissue ablation with no visible thermal damage is shown.

  6. Size control of vapor bubbles on a silver film by a tuned CW laser

    Directory of Open Access Journals (Sweden)

    Y. J. Zheng

    2012-06-01

    Full Text Available A vapor bubble is created by a weakly focused continuous-wave (CW laser beam on the surface of a silver film. The temporal dynamics of the bubble is experimentally investigated with a tuned incident laser. The expansion and contraction rates of the vapor bubble are determined by the laser power. The diameter of the vapor bubble can be well controlled through tuning the laser power. A theory model is given to explain the underlying physics in the process. The method reported will have some interesting applications in micro-fluidics and bio-techniques.

  7. 31 CFR 598.309 - Narcotic drug; controlled substance; listed chemical.

    Science.gov (United States)

    2010-07-01

    ...; listed chemical. 598.309 Section 598.309 Money and Finance: Treasury Regulations Relating to Money and... SANCTIONS REGULATIONS General Definitions § 598.309 Narcotic drug; controlled substance; listed chemical. The terms narcotic drug, controlled substance, and listed chemical have the meanings given those...

  8. Aluminum-coated hollow glass fibers for ArF-excimer laser light fabricated by metallorganic chemical-vapor deposition.

    Science.gov (United States)

    Matsuura, Y; Miyagi, M

    1999-04-20

    A hollow fiber composed of a glass capillary tube and a metal thin film upon the inside of the tube is proposed for the delivery of ArF-excimer laser light. From theoretical analysis, aluminum is chosen as the metal layer. A thin aluminum film is deposited by metallorganic chemical-vapor deposition, with dimethylethylamine alane employed as the source material. Measured loss spectra in vacuum-ultraviolet and ultraviolet regions and losses for ArF-excimer laser light show the low-loss property of the aluminum-coated fiber at the 193-nm wavelength of ArF-excimer laser light. The straight loss of the 1-m long, 1-mm-bore fiber is 1.0 dB.

  9. Particle Generation by Laser Ablation in Support of Chemical Analysis of High Level Mixed Waste from Plutonium Production Operations

    Energy Technology Data Exchange (ETDEWEB)

    J. Thomas Dickinson; Michael L. Alexander

    2001-11-30

    Investigate particles produced by laser irradiation and their analysis by Laser Ablation Inductively Coupled Plasma Mass Spectroscopy (LA/ICP-MS), with a view towards optimizing particle production for analysis of high level waste materials and waste glass. LA/ICP-MS has considerable potential to increase the safety and speed of analysis required for the remediation of high level wastes from cold war plutonium production operations. In some sample types, notably the sodium nitrate-based wastes at Hanford and elsewhere, chemical analysis using typical laser conditions depends strongly on the details of sample history composition in a complex fashion, rendering the results of analysis uncertain. Conversely, waste glass materials appear to be better behaved and require different strategies to optimize analysis.

  10. Towards Friction Control using laser-induced periodic Surface Structures

    OpenAIRE

    Eichstädt, J.; Römer, G.R.B.E.; Huis in 't Veld, A.J.

    2011-01-01

    This paper aims at contributing to the study of laser-induced periodic surface structures (LIPSS) and the description of their tribological properties in order to facilitate the knowledge for contact mechanical applications. To obtain laser parameters for LIPSS formation, we propose to execute two D2-Experiments. For the transfer of results from static experiments to areas of LIPSS we propose the discrete accumulation of fluences. Areas covered by homogeneously distributed LIPSS were machined...

  11. Development of 3D control of a tiny dew droplet by scattered laser light

    Science.gov (United States)

    Matsumoto, Shigeaki

    2009-06-01

    In order to study dropwise condensation on a metal plate, the method for controlling a tiny dew droplet deposited on a copper plate has been developed by using scattered laser light. The method employed the proportional control combined with shifting movement by an integrator to control the intensity of the scattered laser light constantly. Also, the control simulation of the method has been developed to confirm the usefulness of the method and the simulated three-dimensional shape of controlled dew droplet was obtained with the control action. A tiny thin dew droplet, of which the diameter was of handreds micrometers and the mass was about 10-7 g, was controlled in the atmosphere at room temperature for 60 minutes at the preset level of the intensity of scattered laser light and the three-dimensional shape of the controlled dew droplet was shown from the interference fringes.

  12. A non-contact temperature measurement system for controlling photothermal medical laser treatments

    Science.gov (United States)

    Kaya, Ã.-zgür; Gülsoy, Murat

    2016-03-01

    Photothermal medical laser treatments are extremely dependent on the generated tissue temperature. It is necessary to reach a certain temperature threshold to achieve successful results, whereas preventing to exceed an upper temperature value is required to avoid thermal damage. One method to overcome this problem is to use previously conducted dosimetry studies as a reference. Nevertheless, these results are acquired in controlled environments using uniform subjects. In the clinical environment, the optical and thermal characteristics (tissue color, composition and hydration level) vary dramatically among different patients. Therefore, the most reliable solution is to use a closed-loop feedback system that monitors the target tissue temperature to control laser exposure. In this study, we present a compact, non-contact temperature measurement system for the control of photothermal medical laser applications that is cost-efficient and simple to use. The temperature measurement is achieved using a focused, commercially available MOEMS infrared thermocouple sensor embedded in an off-axis arrangement on the laser beam delivery hand probe. The spot size of the temperature sensor is ca. 2.5 mm, reasonably smaller than the laser spot sizes used in photothermal medical laser applications. The temperature readout and laser control is realized using a microcontroller for fast operation. The utilization of the developed system may enable the adaptation of several medical laser treatments that are currently conducted only in controlled laboratory environments into the clinic. Laser tissue welding and cartilage reshaping are two of the techniques that are limited to laboratory research at the moment. This system will also ensure the safety and success of laser treatments aiming hyperthermia, coagulation and ablation, as well as LLLT and PDT.

  13. High-pressure gravity-independent singlet oxygen generator, laser nozzle, and iodine injection system for the chemical oxygen-iodine laser

    Science.gov (United States)

    Emanuel, George

    2004-09-01

    A novel approach is outlined for a singlet oxygen generator (SOG), a laser minimum length nozzle (MLN), and an iodine injector system for a chemical oxygen-iodine laser (COIL). A unified approach, referred to as a SOG/MLN/I2 system, is partly based on past experimental work. For instance, the SOG concept stems from sparger technology and a KSY fesibility experiment. A MLN with a curved sonic line is used for the laser nozzle, and slender struts are used for the injection, in the downstream direction, of iodine/helium vapor. The heated struts are located downstream of the nozzle's throat. The engineering logic behind the approach is discussed; it has a diversity of potential system benefits relative to current technology. These include a compact, scalable laser that can operate in space. The SOG operates at a significantly higher pressure with a high O2(1Δ) yield. In addition, basic hydrogen peroxide reconditioning is not required, a water vapor removal system is not required, and diluent may be unnecessary, although useful for pressure recovery. The impact on a COIL system in terms of power, efficiency, and pressure recovery is briefly assessed.

  14. ABT-controllable laser hyperthermia of biological objects

    Science.gov (United States)

    Krotov, Eugene V.; Yakovlev, Ivan V.; Zhadobov, Maxim; Reyman, Alexander M.

    2002-05-01

    The results of experimentally investigated laser heating of optically absorbing inhomogeneities inside the biological objects accompanied with monitoring of internal temperature by acoustical brightness thermometry (ABT) have been presented. One of the urgent problems of modern medicine is to provide organism safety during photodynamic therapy of various neoplasms including malignant ones. In the case when neoplasm differs from normal tissue mainly in optical absorption it seems to be effective to use laser heating for this purpose. In our experiments we used the NIR emission of CW and pulse-periodic Nd:YAG lasers (1064 nm) as well as CW semiconductor laser (800 nm) for heating of tissue- simulating phantom. Optically transparent gelatine with absorbing inhomogeneity inside was used as a phantom. Internal temperature was measured non-invasively by means of multi-channel ABT after long heating of an object by laser radiation. Temperature was also measured independently by contact electronic thermometer. The results of experiments demonstrated high efficiency of ABT application for internal temperature monitoring during PDT and other hyperthermia procedures. Besides that laser radiation can be used for backlighting followed by ABT investigation of internal structure of temperature distribution inside biological tissues. This work was supported by Russian Foundation for Basic Research (Projects # 00-02-16600; 01-02-06417; 01-02- 17645) and 6th competition-expertise of young scientists of Russian Academy of Sciences (Project #399).

  15. Determination and controlling of grain structure of metals after laser incidence: Theoretical approach

    Science.gov (United States)

    Dezfoli, Amir Reza Ansari; Hwang, Weng-Sing; Huang, Wei-Chin; Tsai, Tsung-Wen

    2017-01-01

    There are serious questions about the grain structure of metals after laser melting and the ways that it can be controlled. In this regard, the current paper explains the grain structure of metals after laser melting using a new model based on combination of 3D finite element (FE) and cellular automaton (CA) models validated by experimental observation. Competitive grain growth, relation between heat flows and grain orientation and the effect of laser scanning speed on final micro structure are discussed with details. Grains structure after laser melting is founded to be columnar with a tilt angle toward the direction of the laser movement. Furthermore, this investigation shows that the grain orientation is a function of conduction heat flux at molten pool boundary. Moreover, using the secondary laser heat source (SLHS) as a new approach to control the grain structure during the laser melting is presented. The results proved that the grain structure can be controlled and improved significantly using SLHS. Using SLHS, the grain orientation and uniformity can be change easily. In fact, this method can help us to produce materials with different local mechanical properties during laser processing according to their application requirements.

  16. High sensitivity stand-off detection and quantification of chemical mixtures using an active coherent laser spectrometer (ACLaS)

    Science.gov (United States)

    MacLeod, Neil A.; Weidmann, Damien

    2016-05-01

    High sensitivity detection, identification and quantification of chemicals in a stand-off configuration is a highly sought after capability across the security and defense sector. Specific applications include assessing the presence of explosive related materials, poisonous or toxic chemical agents, and narcotics. Real world field deployment of an operational stand-off system is challenging due to stringent requirements: high detection sensitivity, stand-off ranges from centimeters to hundreds of meters, eye-safe invisible light, near real-time response and a wide chemical versatility encompassing both vapor and condensed phase chemicals. Additionally, field deployment requires a compact, rugged, power efficient, and cost-effective design. To address these demanding requirements, we have developed the concept of Active Coherent Laser Spectrometer (ACLaS), which can be also described as a middle infrared hyperspectral coherent lidar. Combined with robust spectral unmixing algorithms, inherited from retrievals of information from high-resolution spectral data generated by satellitebased spectrometers, ACLaS has been demonstrated to fulfil the above-mentioned needs. ACLaS prototypes have been so far developed using quantum cascade lasers (QCL) and interband cascade lasers (ICL) to exploit the fast frequency tuning capability of these solid state sources. Using distributed feedback (DFB) QCL, demonstration and performance analysis were carried out on narrow-band absorbing chemicals (N2O, H2O, H2O2, CH4, C2H2 and C2H6) at stand-off distances up to 50 m using realistic non cooperative targets such as wood, painted metal, and bricks. Using more widely tunable external cavity QCL, ACLaS has also been demonstrated on broadband absorbing chemicals (dichloroethane, HFC134a, ethylene glycol dinitrate and 4-nitroacetanilide solid) and on complex samples mixing narrow-band and broadband absorbers together in a realistic atmospheric background.

  17. Heat and Mass Transfer during Chemical Vapor Deposition on the Particle Surface Subjected to Nanosecond Laser Heating

    CERN Document Server

    Peng, Quan; He, Yaling; Mao, Yijin

    2016-01-01

    A thermal model of chemical vapor deposition of titanium nitride (TiN) on the spherical particle surface under irradiation by a nanosecond laser pulse is presented in this paper. Heat and mass transfer on a single spherical metal powder particle surface subjected to temporal Gaussian heat flux is investigated analytically. The chemical reaction on the particle surface and the mass transfer in the gas phase are also considered. The surface temperature, thermal penetration depth, and deposited film thickness under different laser fluence, pulse width, initial particle temperature, and particle radius are investigated. The effect of total pressure in the reaction chamber on deposition rate is studied as well. The particle-level model presented in this paper is an important step toward development of multiscale model of LCVI.

  18. SOFTWARE TOOL FOR LASER CUTTING PROCESS CONTROL – SOLVING REAL INDUSTRIAL CASE STUDIES

    Directory of Open Access Journals (Sweden)

    Miloš Madić

    2016-08-01

    Full Text Available Laser cutting is one of the leading non-conventional machining technologies with a wide spectrum of application in modern industry. It order to exploit a number of advantages that this technology offers for contour cutting of materials, it is necessary to carefully select laser cutting conditions for each given workpiece material, thickness and desired cut qualities. In other words, there is a need for process control of laser cutting. After a comprehensive analysis of the main laser cutting parameters and process performance characteristics, the application of the developed software tool “BRUTOMIZER” for off-line control of CO2 laser cutting process of three different workpiece materials (mild steel, stainless steel and aluminum is illustrated. Advantages and abilities of the developed software tool are also illustrated.

  19. A study on fractional erbium glass laser therapy versus chemical peeling for the treatment of melasma in female patients

    Directory of Open Access Journals (Sweden)

    Neerja Puri

    2013-01-01

    Full Text Available Introduction: Melasma is a commonly acquired hypermelanosis and a common dermatologic skin disease that occurs on sun-exposed areas of face. Aims: To assess the efficacy and safety of non-ablative 1,550 nm Erbium glass fractional laser therapy and compare results with those obtained with chemical peeling. Materials and Methods: We selected 30 patients of melasma aged between 20 years and 50 years for the study. The patients were divided into two groups of 15 patients each. Group I patients were subjected to four sessions of 1,550 nm Erbium glass non-ablative fractional laser at 3 weeks interval. In group II patients, four sessions of chemical peeling with 70% glycolic acid was performed. Results: After 12 weeks of treatment, percentage reduction in Melasma Area and Severity Index (MASI score was seen in 62.9% in the laser group and 58.7% in the peels group. Conclusion: It was observed that 1,550 nm fractional laser is as effective as 70% glycolic acid peel in reducing MASI score in patients with melasma.

  20. A Study on Fractional Erbium Glass Laser Therapy Versus Chemical Peeling for the Treatment of Melasma in Female Patients

    Science.gov (United States)

    Puri, Neerja

    2013-01-01

    Introduction: Melasma is a commonly acquired hypermelanosis and a common dermatologic skin disease that occurs on sun-exposed areas of face. Aims: To assess the efficacy and safety of non-ablative 1,550 nm Erbium glass fractional laser therapy and compare results with those obtained with chemical peeling. Materials and Methods: We selected 30 patients of melasma aged between 20 years and 50 years for the study. The patients were divided into two groups of 15 patients each. Group I patients were subjected to four sessions of 1,550 nm Erbium glass non-ablative fractional laser at 3 weeks interval. In group II patients, four sessions of chemical peeling with 70% glycolic acid was performed. Results: After 12 weeks of treatment, percentage reduction in Melasma Area and Severity Index (MASI) score was seen in 62.9% in the laser group and 58.7% in the peels group. Conclusion: It was observed that 1,550 nm fractional laser is as effective as 70% glycolic acid peel in reducing MASI score in patients with melasma. PMID:24163531

  1. Precision Locking and Control of CW Lasers in Support of ASCENDS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Vescent Photonics proposes to design and build significantly improved laser frequency locking and control systems that will be suitable for ASCENDS and other NASA...

  2. A Power-Controllable Semiconductor Fiber Ring Laser and its Applications

    Institute of Scientific and Technical Information of China (English)

    Z.G.; Lu; C.P.; Grover

    2003-01-01

    A stable and power controllable laser with larger than 17-dB output power range is presented. Based on this device, a novel optical amplifier with the power transit immune behaviors has been demonstrated.

  3. Addressing Control of Hazardous Energy (COHE) Requirements in a Laser Safety Program

    Energy Technology Data Exchange (ETDEWEB)

    Woods, Michael; /SLAC

    2012-02-15

    OSHA regulation 29CFR1910.147 specifies control of hazardous energy requirements for 'the servicing and maintenance of machines and equipment in which the unexpected energization or start up of the machines or equipment, or release of stored energy could cause injury to employees.' Class 3B and Class 4 laser beams must be considered hazardous energy sources because of the potential for serious eye injury; careful consideration is therefore needed to safely de-energize these lasers. This paper discusses and evaluates control of hazardous energy principles in this OSHA regulation, in ANSI Z136.1 ''Safe Use of Lasers,'' and in ANSI Z244.1 ''Control of Hazardous Energy, Lockout/Tagout and Alternative Methods.'' Recommendations are made for updating and improving CoHE (control of hazardous energy) requirements in these standards for their applicability to safe laser operations.

  4. Coupled molecular dynamics-Monte Carlo model to study the role of chemical processes during laser ablation of polymeric materials.

    Science.gov (United States)

    Prasad, Manish; Conforti, Patrick F; Garrison, Barbara J

    2007-08-28

    The coarse grained chemical reaction model is enhanced to build a molecular dynamics (MD) simulation framework with an embedded Monte Carlo (MC) based reaction scheme. The MC scheme utilizes predetermined reaction chemistry, energetics, and rate kinetics of materials to incorporate chemical reactions occurring in a substrate into the MD simulation. The kinetics information is utilized to set the probabilities for the types of reactions to perform based on radical survival times and reaction rates. Implementing a reaction involves changing the reactants species types which alters their interaction potentials and thus produces the required energy change. We discuss the application of this method to study the initiation of ultraviolet laser ablation in poly(methyl methacrylate). The use of this scheme enables the modeling of all possible photoexcitation pathways in the polymer. It also permits a direct study of the role of thermal, mechanical, and chemical processes that can set off ablation. We demonstrate that the role of laser induced heating, thermomechanical stresses, pressure wave formation and relaxation, and thermochemical decomposition of the polymer substrate can be investigated directly by suitably choosing the potential energy and chemical reaction energy landscape. The results highlight the usefulness of such a modeling approach by showing that various processes in polymer ablation are intricately linked leading to the transformation of the substrate and its ejection. The method, in principle, can be utilized to study systems where chemical reactions are expected to play a dominant role or interact strongly with other physical processes.

  5. Chemical Oxidation of La2CuO4 Epitaxial Thin Films Grown by Pulsed Laser Deposition

    Institute of Scientific and Technical Information of China (English)

    WANG Chun-Chang; YAN Yun-Jie; ZHU Jing

    2007-01-01

    Chemical oxidation is used to induce superconductivity in La2CuO4 expitaxial thin films fabricated by pulsed laser deposition technique. Details about the influence of oxidation time on structural, surface morphology, Raman spectra, and electrical properties have been investigated. The results convince that successful uptake of oxygen occurs in the oxidized films, and the content of the inserted oxygen increases with increasing oxidation interval. The possible mechanism for the excess oxygen insertion into the film is also discussed.

  6. New Possibilities for Magnetic Control of Chemical and Biochemical Reactions.

    Science.gov (United States)

    Buchachenko, Anatoly; Lawler, Ronald G

    2017-02-20

    Chemistry is controlled by Coulomb energy; magnetic energy is lower by many orders of magnitude and may be confidently ignored in the energy balance of chemical reactions. The situation becomes less clear, however, when reaction rates are considered. In this case, magnetic perturbations of nearly degenerate energy surface crossings may produce observable, and sometimes even dramatic, effects on reactions rates, product yields, and spectroscopic transitions. A case in point that has been studied for nearly five decades is electron spin-selective chemistry via the intermediacy of radical pairs. Magnetic fields, external (permanent or oscillating) and the internal magnetic fields of magnetic nuclei, have been shown to overcome electron spin selection rules for pairs of reactive paramagnetic intermediates, catalyzing or inhibiting chemical reaction pathways. The accelerating effects of magnetic stimulation may therefore be considered to be magnetic catalysis. This type of catalysis is most commonly observed for reactions of a relatively long-lived radical pair containing two weakly interacting electron spins formed by dissociation of molecules or by electron transfer. The pair may exist in singlet (total electron spin is zero) or triplet (total spin is unity) spin states. In virtually all cases, only the singlet state yields stable reaction products. Magnetic interactions with nuclear spins or applied fields may therefore affect the reactivity of radical pairs by changing the angular momentum of the pairs. Magnetic catalysis, first detected via its effect on spin state populations in nuclear and electron spin resonance, has been shown to function in a great variety of well-characterized reactions of organic free radicals. Considerably less well studied are examples suggesting that the basic mechanism may also explain magnetic effects that stimulate ATP synthesis, eliminating ATP deficiency in cardiac diseases, control cell proliferation, killing cancer cells, and

  7. Chemical-assisted femtosecond laser writing of lab-in-fibers.

    Science.gov (United States)

    Haque, Moez; Lee, Kenneth K C; Ho, Stephen; Fernandes, Luís A; Herman, Peter R

    2014-10-07

    The lab-on-chip (LOC) platform has presented a powerful opportunity to improve functionalization, parallelization, and miniaturization on planar or multilevel geometries that has not been possible with fiber optic technology. A migration of such LOC devices into the optical fiber platform would therefore open the revolutionary prospect of creating novel lab-in-fiber (LIF) systems on the basis of an efficient optical transport highway for multifunctional sensing. For the LIF, the core optical waveguide inherently offers a facile means to interconnect numerous types of sensing elements along the optical fiber, presenting a radical opportunity for optimizing the packaging and densification of diverse components in convenient geometries beyond that available with conventional LOCs. In this paper, three-dimensional patterning inside the optical fiber by femtosecond laser writing, together with selective chemical etching, is presented as a powerful tool to form refractive index structures such as optical waveguides and gratings as well as to open buried microfluidic channels and optical resonators inside the flexible and robust glass fiber. In this approach, optically smooth surfaces (~12 nm rms) are introduced for the first time inside the fiber cladding that precisely conform to planar nanograting structures when formed by aberration-free focusing with an oil-immersion lens across the cylindrical fiber wall. This process has enabled optofluidic components to be precisely embedded within the fiber to be probed by either the single-mode fiber core waveguide or the laser-formed optical circuits. We establish cladding waveguides, X-couplers, fiber Bragg gratings, microholes, mirrors, optofluidic resonators, and microfluidic reservoirs that define the building blocks for facile interconnection of inline core-waveguide devices with cladding optofluidics. With these components, more advanced, integrated, and multiplexed fiber microsystems are presented demonstrating

  8. Chemical control of spin propagation between heterometallic rings.

    Science.gov (United States)

    Faust, Thomas B; Bellini, Valerio; Candini, Andrea; Carretta, Stefano; Lorusso, Giulia; Allan, David R; Carthy, Laura; Collison, David; Docherty, Rebecca J; Kenyon, Jasbinder; Machin, John; McInnes, Eric J L; Muryn, Christopher A; Nowell, Harriott; Pritchard, Robin G; Teat, Simon J; Timco, Grigore A; Tuna, Floriana; Whitehead, George F S; Wernsdorfer, Wolfgang; Affronte, Marco; Winpenny, Richard E P

    2011-12-09

    We present a synthetic, structural, theoretical, and spectroscopic study of a family of heterometallic ring dimers which have the formula [{Cr(7)NiF(3)(Etglu)(O(2)CtBu)(15)}(2)(NLN)], in which Etglu is the pentadeprotonated form of the sugar N-ethyl-D-glucamine, and NLN is an aromatic bridging diimine ligand. By varying NLN we are able to adjust the strength of the interaction between rings with the aim of understanding how to tune our system to achieve weak magnetic communication between the spins, a prerequisite for quantum entanglement. Micro-SQUID and EPR data reveal that the magnetic coupling between rings is partly related to the through-bond distance between the spin centers, but also depends on spin-polarization mechanisms and torsion angles between aromatic rings. Density functional theory (DFT) calculations allow us to make predictions of how such chemically variable parameters could be used to tune very precisely the interaction in such systems. For possible applications in quantum information processing and molecular spintronics, such precise control is essential.

  9. Physical controls on directed virus assembly at nanoscale chemical templates

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, C L; Chung, S; Chatterji, A; Lin, T; Johnson, J E; Hok, S; Perkins, J; De Yoreo, J

    2006-05-10

    Viruses are attractive building blocks for nanoscale heterostructures, but little is understood about the physical principles governing their directed assembly. In-situ force microscopy was used to investigate organization of Cowpea Mosaic Virus engineered to bind specifically and reversibly at nanoscale chemical templates with sub-30nm features. Morphological evolution and assembly kinetics were measured as virus flux and inter-viral potential were varied. The resulting morphologies were similar to those of atomic-scale epitaxial systems, but the underlying thermodynamics was analogous to that of colloidal systems in confined geometries. The 1D templates biased the location of initial cluster formation, introduced asymmetric sticking probabilities, and drove 1D and 2D condensation at subcritical volume fractions. The growth kinetics followed a t{sup 1/2} law controlled by the slow diffusion of viruses. The lateral expansion of virus clusters that initially form on the 1D templates following introduction of polyethylene glycol (PEG) into the solution suggests a significant role for weak interaction.

  10. Comparison of some effects of modification of a polylactide surface layer by chemical, plasma, and laser methods

    Energy Technology Data Exchange (ETDEWEB)

    Moraczewski, Krzysztof, E-mail: kmm@ukw.edu.pl [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Rytlewski, Piotr [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland); Malinowski, Rafał [Institute for Engineering of Polymer Materials and Dyes, ul. M. Skłodowskiej–Curie 55, 87-100 Toruń (Poland); Żenkiewicz, Marian [Department of Materials Engineering, Kazimierz Wielki University, Department of Materials Engineering, ul. Chodkiewicza 30, 85-064 Bydgoszcz (Poland)

    2015-08-15

    Highlights: • We modified polylactide surface layer with chemical, plasma or laser methods. • We tested selected properties and surface structure of modified samples. • We stated that the plasma treatment appears to be the most beneficial. - Abstract: The article presents the results of studies and comparison of selected properties of the modified PLA surface layer. The modification was carried out with three methods. In the chemical method, a 0.25 M solution of sodium hydroxide in water and ethanol was utilized. In the plasma method, a 50 W generator was used, which produced plasma in the air atmosphere under reduced pressure. In the laser method, a pulsed ArF excimer laser with fluency of 60 mJ/cm{sup 2} was applied. Polylactide samples were examined by using the following techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), goniometry and X-ray photoelectron spectroscopy (XPS). Images of surfaces of the modified samples were recorded, contact angles were measured, and surface free energy was calculated. Qualitative and quantitative analyses of chemical composition of the PLA surface layer were performed as well. Based on the survey it was found that the best modification results are obtained using the plasma method.

  11. Laser-activated nano-biomaterials for tissue repair and controlled drug release

    Energy Technology Data Exchange (ETDEWEB)

    Matteini, P; Ratto, F; Rossi, F; Pini, R [Institute of Applied Physics ' Nello Carrara' , National Research Council, via Madonna del Piano 10 50019 Sesto Fiorentino (Italy)

    2014-07-31

    We present recent achievements of minimally invasive welding of biological tissue and controlled drug release based on laser-activated nano-biomaterials. In particular, we consider new advancements in the biomedical application of near-IR absorbing gold nano-chromophores as an original solution for the photothermal repair of surgical incisions and as nanotriggers of controlled drug release from hybrid biopolymer scaffolds. (laser biophotonics)

  12. Distributed computer control system in the Nova Laser Fusion Test Facility

    Energy Technology Data Exchange (ETDEWEB)

    1985-09-01

    The EE Technical Review has two purposes - to inform readers of various activities within the Electronics Engineering Department and to promote the exchange of ideas. The articles, by design, are brief summaries of EE work. The articles included in this report are as follows: Overview - Nova Control System; Centralized Computer-Based Controls for the Nova Laser Facility; Nova Pulse-Power Control System; Nova Laser Alignment Control System; Nova Beam Diagnostic System; Nova Target-Diagnostics Control System; and Nova Shot Scheduler. The 7 papers are individually abstracted.

  13. Laser-induced breakdown spectroscopy for on-line control of selective removal of cobalt binder from tungsten carbide hardmetal by pulsed UV laser surface ablation

    Science.gov (United States)

    Li, Tiejun; Lou, Qihong; Wei, Yunrong; Huang, Feng; Dong, Jingxing; Liu, Jingru

    2001-09-01

    Laser-induced breakdown spectroscopy (LIBS) was successfully used in on-line control of selective removal of cobalt from tungsten carbide hardmetal by pulsed UV laser surface ablation. The dependence of LIBS on number of laser shots was investigated at different laser fluences. The optimal laser fluence of 2.5 J/cm 2 suited for selective removal of cobalt from surface layer of hardmetal was confirmed. The result sample was also subject to different post-examinations to evaluate the feasibility of the application of LIBS in this laser ablation process. It was demonstrated that, monitoring of the emission intensity of cobalt lines could be used as a control parameter for selective removal of cobalt from surface layer of hardmetal by pulsed UV laser. The on-line implementation of the spectroscopic technique LIBS to the surface-ablation process provided important information about the optimal-ablation parameters.

  14. High power lasers & systems

    OpenAIRE

    Chatwin, Chris; Young, Rupert; Birch, Philip

    2015-01-01

    Some laser history;\\ud Airborne Laser Testbed & Chemical Oxygen Iodine Laser (COIL);\\ud Laser modes and beam propagation;\\ud Fibre lasers and applications;\\ud US Navy Laser system – NRL 33kW fibre laser;\\ud Lockheed Martin 30kW fibre laser;\\ud Conclusions

  15. Laser assisted modification and chemical metallization of electron-beam deposited ceria thin films

    Energy Technology Data Exchange (ETDEWEB)

    Krumov, E., E-mail: emodk@clf.bas.bg [Central Laboratory of Photoprocesses ' Acad. Jordan Malinowski' , Bulgarian Academy of Sciences, Acad. Georgy Bonchev Str., bl. 109, 1113 Sofia (Bulgaria); Starbov, N.; Starbova, K. [Central Laboratory of Photoprocesses ' Acad. Jordan Malinowski' , Bulgarian Academy of Sciences, Acad. Georgy Bonchev Str., bl. 109, 1113 Sofia (Bulgaria); Perea, A.; Solis, J. [Instituto de Optica ' Daza de Valdes' , CSIC, 28006 Madrid (Spain)

    2009-11-15

    Excimer laser processing is applied for tailoring the surface morphology and phase composition of CeO{sub 2} ceramic thin films. E-beam evaporation technique is used to deposit samples on stainless steel and silicate glass substrates. The films are then irradiated with ArF* excimer laser pulses under different exposure conditions. Scanning electron microscopy, optical spectrophotometry, X-ray diffractometry and EDS microanalysis are used to characterize the non-irradiated and laser-processed films. Upon UV laser exposure there is large increase of the surface roughness that is accompanied by photo-darkening and ceria reduction. It is shown that the laser induced changes in the CeO{sub 2} films facilitate the deposition of metal nano-aggregates in a commercial copper electroless plating bath. The significance of laser modification as a novel approach for the production of CeO{sub 2} based thin film catalysts is discussed.

  16. Quantum interferences and their classical limit in laser driven coherent control scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Franco, Ignacio, E-mail: ifranco@chem.northwestern.edu [Chemical Physics Theory Group, Department of Chemistry, Center for Quantum Information and Quantum Control, University of Toronto, Toronto, ON, M5S 3H6 (Canada); Spanner, Michael; Brumer, Paul [Chemical Physics Theory Group, Department of Chemistry, Center for Quantum Information and Quantum Control, University of Toronto, Toronto, ON, M5S 3H6 (Canada)

    2010-05-12

    Graphical abstract: The analogy between Young's double-slit experiment with matter and laser driven coherent control schemes is investigated, and shown to be limited. To do so, a general decomposition of observables in the Heisenberg picture into direct terms and interference contributions is introduced, and formal quantum-classical correspondence arguments in the Heisenberg picture are employed to define classical analogs of quantum interference terms. While the classical interference contributions in the double-slit experiment are shown to be zero, they can be nonzero in laser driven coherent control schemes and lead to laser control in the classical limit. This classical limit is interpreted in terms of nonlinear response theory arguments. - Abstract: The analogy between Young's double-slit experiment with matter and laser driven coherent control schemes is investigated, and shown to be limited. To do so, a general decomposition of observables in the Heisenberg picture into direct terms and interference contributions is introduced, and formal quantum-classical correspondence arguments in the Heisenberg picture are employed to define classical analogs of quantum interference terms. While the classical interference contributions in the double-slit experiment are shown to be zero, they can be nonzero in laser driven coherent control schemes and lead to laser control in the classical limit. This classical limit is interpreted in terms of nonlinear response theory arguments.

  17. A novel intelligent adaptive control of laser-based ground thermal test

    Institute of Scientific and Technical Information of China (English)

    Gan Zhengtao; Yu Gang; Li Shaoxia; He Xiuli; Chen Ru; Zheng Caiyun; Ning Weijian

    2016-01-01

    Laser heating technology is a type of potential and attractive space heat flux simulation technology, which is characterized by high heating rate, controlled spatial intensity distribution and rapid response. However, the controlled plant is nonlinear, time-varying and uncertainty when implementing the laser-based heat flux simulation. In this paper, a novel intelligent adaptive controller based on proportion–integration–differentiation (PID) type fuzzy logic is proposed to improve the performance of laser-based ground thermal test. The temperature range of thermal cycles is more than 200 K in many instances. In order to improve the adaptability of controller, output scaling factors are real time adjusted while the thermal test is underway. The initial values of scaling factors are optimized using a stochastic hybrid particle swarm optimization (H-PSO) algorithm. A validating system has been established in the laboratory. The performance of the pro-posed controller is evaluated through extensive experiments under different operating conditions (reference and load disturbance). The results show that the proposed adaptive controller performs remarkably better compared to the conventional PID (PID) controller and the conventional PID type fuzzy (F-PID) controller considering performance indicators of overshoot, settling time and steady state error for laser-based ground thermal test. It is a reliable tool for effective temperature control of laser-based ground thermal test.

  18. A novel intelligent adaptive control of laser-based ground thermal test

    Directory of Open Access Journals (Sweden)

    Gan Zhengtao

    2016-08-01

    Full Text Available Laser heating technology is a type of potential and attractive space heat flux simulation technology, which is characterized by high heating rate, controlled spatial intensity distribution and rapid response. However, the controlled plant is nonlinear, time-varying and uncertainty when implementing the laser-based heat flux simulation. In this paper, a novel intelligent adaptive controller based on proportion–integration–differentiation (PID type fuzzy logic is proposed to improve the performance of laser-based ground thermal test. The temperature range of thermal cycles is more than 200 K in many instances. In order to improve the adaptability of controller, output scaling factors are real time adjusted while the thermal test is underway. The initial values of scaling factors are optimized using a stochastic hybrid particle swarm optimization (H-PSO algorithm. A validating system has been established in the laboratory. The performance of the proposed controller is evaluated through extensive experiments under different operating conditions (reference and load disturbance. The results show that the proposed adaptive controller performs remarkably better compared to the conventional PID (PID controller and the conventional PID type fuzzy (F-PID controller considering performance indicators of overshoot, settling time and steady state error for laser-based ground thermal test. It is a reliable tool for effective temperature control of laser-based ground thermal test.

  19. Quantum coherent control of the vibrational dynamics of a polyatomic molecule using adaptive feedback control of a femtosecond laser

    Indian Academy of Sciences (India)

    L R Botha; L E De Clercq; A M Smit; N Botha; E Ronander; H J Strydom

    2014-02-01

    We simulate adaptive feedback control to coherently shape a femtosecond infrared laser pulse by means of a 4f-spatial light modulator in order to selectively excite the rovibrational modes of a polyatomic molecule. We preferentially populate an arbitrarily chosen upper rovibrational level by only employing these tailored temporally shaped pulses. A second laser would then allow for mode selective chemistry to interact selectively with the excited population. Alternatively the excited molecules enhanced reactivity could be exploited for selective chemistry.

  20. Chemical contaminants in swimming pools: Occurrence, implications and control.

    Science.gov (United States)

    Teo, Tiffany L L; Coleman, Heather M; Khan, Stuart J

    2015-03-01

    A range of trace chemical contaminants have been reported to occur in swimming pools. Current disinfection practices and monitoring of swimming pool water quality are aimed at preventing the spread of microbial infections and diseases. However, disinfection by-products (DBPs) are formed when the disinfectants used react with organic and inorganic matter in the pool. Additional chemicals may be present in swimming pools originating from anthropogenic sources (bodily excretions, lotions, cosmetics, etc.) or from the source water used where trace chemicals may already be present. DBPs have been the most widely investigated trace chemical contaminants, including trihalomethanes (THMs), haloacetic acids (HAAs), halobenzoquinones (HBQs), haloacetonitriles (HANs), halonitromethanes (HNMs), N-nitrosamines, nitrite, nitrates and chloramines. The presence and concentrations of these chemical contaminants are dependent upon several factors including the types of pools, types of disinfectants used, disinfectant dosages, bather loads, temperature and pH of swimming pool waters. Chemical constituents of personal care products (PCPs) such as parabens and ultraviolet (UV) filters from sunscreens have also been reported. By-products from reactions of these chemicals with disinfectants and UV irradiation have been reported and some may be more toxic than their parent compounds. There is evidence to suggest that exposure to some of these chemicals may lead to health risks. This paper provides a detailed review of various chemical contaminants reported in swimming pools. The concentrations of chemicals present in swimming pools may also provide an alternative indicator to swimming pool water quality, providing insights to contamination sources. Alternative treatment methods such as activated carbon filtration and advanced oxidation processes may be beneficial in improving swimming pool water quality.

  1. Fabrication of broadband antireflective black metal surfaces with ultra-light-trapping structures by picosecond laser texturing and chemical fluorination

    Science.gov (United States)

    Zheng, Buxiang; Wang, Wenjun; Jiang, Gedong; Mei, Xuesong

    2016-06-01

    A hybrid method consisting of ultrafast laser-assisted texturing and chemical fluorination treatment was applied for efficiently enhancing the surface broadband antireflection to fabricate black titanium alloy surface with ultra-light-trapping micro-nanostructure. Based on the theoretical analysis of surface antireflective principle of micro-nanostructures and fluoride film, the ultra-light-trapping micro-nanostructures have been processed using a picosecond pulsed ultrafast laser on titanium alloy surfaces. Then fluorination treatment has been performed by using fluoroalkyl silane solution. According to X-ray diffraction phase analysis of the surface compositions and measurement of the surface reflectance using spectrophotometer, the broadband antireflective properties of titanium alloy surface with micro-nano structural characteristics were investigated before and after fluorination treatment. The results show that the surface morphology of micro-nanostructures processed by picosecond laser has significant effects on the antireflection of light waves to reduce the surface reflectance, which can be further reduced using chemical fluorination treatment. The high antireflection of over 98 % in a broad spectral range from ultraviolet to infrared on the surface of metal material has been achieved for the surface structures, and the broadband antireflective black metal surfaces with an extremely low reflectance of ultra-light-trapping structures have been obtained in the wavelength range from ultraviolet-visible to near-infrared, middle-wave infrared. The average reflectance of microgroove groups structured surface reaches as low as 2.43 % over a broad wavelength range from 200 to 2600 nm. It indicates that the hybrid method comprising of picosecond laser texturing and chemical fluorination can effectively induce the broadband antireflective black metal surface. This method has a potential application for fabricating antireflective surface used to improve the

  2. Laser system for identification, tracking, and control of flying insects

    Science.gov (United States)

    Flying insects are common vectors for transmission of pathogens and inflict significant harm on humans in large parts of the developing world. Besides the direct impact to humans, these pathogens also cause harm to crops and result in agricultural losses. Here, we present a laser-based system that c...

  3. Optomechatronics Design and Control for Confocal Laser Scanning Microscopy

    NARCIS (Netherlands)

    Yoo, H.W.

    2015-01-01

    Confocal laser scanning microscopy (CLSM) is considered as one of the major advancements in microscopy in the last century and is widely accepted as a 3D fluorescence imaging tool for biological studies. For the emerging biological questions CLSM requires fast imaging to detect rapid biological proc

  4. Designing, modeling and controlling a novel autonomous laser weeding system

    DEFF Research Database (Denmark)

    Shahrak Nadimi, Esmaeil; Andersson, Kim Johan; Jørgensen, Rasmus Nyholm

    2009-01-01

      Abstract: in this paper, the process of designing and developing a novel laser weeding test setup is explained. The main purpose of designing this system was to simulate the dynamic field conditions of a mobile vehicle capable of targeting weeds. This system consists of a rig containing three...

  5. Significance of the Resonance Condition for Controlling the Seam Position in Laser-assisted TIG Welding

    Science.gov (United States)

    Emde, B.; Huse, M.; Hermsdorf, J.; Kaierle, S.; Wesling, V.; Overmeyer, L.; Kozakov, R.; Uhrlandt, D.

    As an energy-preserving variant of laser hybrid welding, laser-assisted arc welding uses laser powers of less than 1 kW. Recent studies have shown that the electrical conductivity of a TIG welding arc changes within the arc in case of a resonant interaction between laser radiation and argon atoms. This paper presents investigations on how to control the position of the arc root on the workpiece by means of the resonant interaction. Furthermore, the influence on the welding result is demonstrated. The welding tests were carried out on a cooled copper plate and steel samples with resonant and non-resonant laser radiation. Moreover, an analysis of the weld seam is presented.

  6. A real-time laser feedback control method for the three-wave laser source used in the polarimeter-interferometer diagnostic on Joint-TEXT tokamak.

    Science.gov (United States)

    Xiong, C Y; Chen, J; Li, Q; Liu, Y; Gao, L

    2014-12-01

    A three-wave laser polarimeter-interferometer, equipped with three independent far-infrared laser sources, has been developed on Joint-TEXT (J-TEXT) tokamak. The diagnostic system is capable of high-resolution temporal and phase measurement of the Faraday angle and line-integrated density. However, for long-term operation (>10 min), the free-running lasers can lead to large drifts of the intermediate frequencies (∼100-∼500 kHz/10 min) and decay of laser power (∼10%-∼20%/10 min), which act to degrade diagnostic performance. In addition, these effects lead to increased maintenance cost and limit measurement applicability to long pulse/steady state experiments. To solve this problem, a real-time feedback control method of the laser source is proposed. By accurately controlling the length of each laser cavity, both the intermediate frequencies and laser power can be simultaneously controlled: the intermediate frequencies are controlled according to the pre-set values, while the laser powers are maintained at an optimal level. Based on this approach, a real-time feedback control system has been developed and applied on J-TEXT polarimeter-interferometer. Long-term (theoretically no time limit) feedback of intermediate frequencies (maximum change less than ±12 kHz) and laser powers (maximum relative power change less than ±7%) has been successfully achieved.

  7. Small laser spot versus standard laser spot photodynamic therapy for idiopathic choroidal neovascularization: a randomized controlled study

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-xin; TAO Yong

    2012-01-01

    Backcround Idiopathic choroidal neovascularization (ICNV) affects young patients and thus may have a significant impact on vision and life quality over a patient's lifespan.This study was designed to compare the visual outcome and retinal pigment epithelium (RPE) damage after photodynamic therapy (PDT) with small laser spot and PDT with standard laser spot for idiopathic choroidal neovascularization (ICNV).Methods This was a randomized controlled study.Fifty-two patients with ICNV were enrolled and randomly divided into a study group (small laser spot PDT,n=27) and a control group (standard laser spot PDT,n=25).Best corrected visual acuity (BCVA),optic coherence tomography (OCT) and fluorescein angiography (FA) findings were the main measurements.The patients were followed up 1 week,1,3,6,9 months and 1 year after PDT.Results BCVA improvement was statistically significantly higher in the study group than the control group at 6-month ((25.53±15.01) letters vs.(14.71±11.66) letters,P=0.025) and 9-month follow-ups ((27.53±17.78) letters vs.(15.59±12.21) letters,P=0.039).At 3-and 6-month follow-ups,the quadrants of RPE damage between the two groups varied significantly (P <0.001 and P=0.023,respectively).In each follow-up,the number of cases with decreased or unchanged leakage of choroidal neovascularization by FA and reduced subretinal fluid by OCT did not vary significantly between the two groups.Ten cases (37.0%) in the study group and eight cases (32.0%) in the control group suffered from recurrent CNV (P=0.703).Conclusions Better visual improvements,less RPE damage,a similar recurrent rate of CNV and change of subretinal fluid were observed in the small laser spot PDT group than in the standard laser spot PDT group for ICNV.

  8. Demonstration of a rapidly-swept external cavity quantum cascade laser for rapid and sensitive quantification of chemical mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Brumfield, Brian E.; Taubman, Matthew S.; Phillips, Mark C.

    2016-02-13

    A rapidly-swept external cavity quantum cascade laser (ECQCL) system for fast open-path quantification of multiple chemicals and mixtures is presented. The ECQCL system is swept over its entire tuning range (>100 cm-1) at frequencies up to 200 Hz. At 200 Hz the wavelength tuning rate and spectral resolution are 2x104 cm-1/sec and < 0.2 cm-1, respectively. The capability of the current system to quantify changes in chemical concentrations on millesecond timescales is demonstrated at atmospheric pressure using an open-path multi-pass cell. The detection limits for chemicals ranged from ppb to ppm levels depending on the absorption cross-section.

  9. Experimental control of the beam properties of laser-accelerated protons and carbon ions

    Energy Technology Data Exchange (ETDEWEB)

    Amin, Munib

    2008-12-15

    The laser generation of energetic high quality beams of protons and heavier ions has opened up the door to a plethora of applications. These beams are usually generated by the interaction of a short pulse high power laser with a thin metal foil target. They could already be applied to probe transient phenomena in plasmas and to produce warm dense matter by isochoric heating. Other applications such as the production of radioisotopes and tumour radiotherapy need further research to be put into practice. To meet the requirements of each application, the properties of the laser-accelerated particle beams have to be controlled precisely. In this thesis, experimental means to control the beam properties of laser-accelerated protons and carbon ions are investigated. The production and control of proton and carbon ion beams is studied using advanced ion source designs: Experiments concerning mass-limited (i.e. small and isolated) targets are conducted. These targets have the potential to increase both the number and the energy of laser-accelerated protons. Therefore, the influence of the size of a plane foil target on proton beam properties is measured. Furthermore, carbon ion sources are investigated. Carbon ions are of particular interest in the production of warm dense matter and in cancer radiotherapy. The possibility to focus carbon ion beams is investigated and a simple method for the production of quasi-monoenergetic carbon ion beams is presented. This thesis also provides an insight into the physical processes connected to the production and the control of laser-accelerated ions. For this purpose, laser-accelerated protons are employed to probe plasma phenomena on laser-irradiated targets. Electric fields evolving on the surface of laser-irradiated metal foils and hollow metal foil cylinders are investigated. Since these fields can be used to displace, collimate or focus proton beams, understanding their temporal and spatial evolution is crucial for the design of

  10. Interfacing ?Soft? and ?Hard? Matter with Exquisite Chemical Control

    Energy Technology Data Exchange (ETDEWEB)

    Woo, Y; Camarero, J A

    2006-01-13

    The present paper reviews the recent development of new chemical and biological technologies for the site-specific immobilization of proteins onto inorganic materials and their potential applications to the fields of micro and nanotechnology.

  11. Wavefront control of high power laser beams for the National Ignition Facility (NIF)

    Energy Technology Data Exchange (ETDEWEB)

    Bliss, E; Feldman, M; Grey, A; Koch, J; Lund, L; Sacks, R; Smith, D; Stolz, C; Van Atta, L; Winters, S; Woods, B; Zacharias, R

    1999-09-22

    The use of lasers as the driver for inertial confinement fusion and weapons physics experiments is based on their ability to produce high-energy short pulses in a beam with low divergence. Indeed, the focus ability of high quality laser beams far exceeds alternate technologies and is a major factor in the rationale for building high power lasers for such applications. The National Ignition Facility (NIF) is a large, 192-beam, high-power laser facility under construction at the Lawrence Livermore National Laboratory for fusion and weapons physics experiments. Its uncorrected minimum focal spot size is limited by laser system aberrations. The NIF includes a Wavefront Control System to correct these aberrations to yield a focal spot small enough for its applications. Sources of aberrations to be corrected include prompt pump-induced distortions in the laser amplifiers, previous-shot thermal distortions, beam off-axis effects, and gravity, mounting, and coating-induced optic distortions. Aberrations from gas density variations and optic manufacturing figure errors are also partially corrected. This paper provides an overview of the NIF Wavefront Control System and describes the target spot size performance improvement it affords. It describes provisions made to accommodate the NIF's high fluence (laser beam and flashlamp), large wavefront correction range, wavefront temporal bandwidth, temperature and humidity variations, cleanliness requirements, and exception handling requirements (e.g. wavefront out-of-limits conditions).

  12. Shaped Plasma Lenses for Optical Beam Control at High Laser Intensities

    Science.gov (United States)

    Hubbard, R. F.; Palastro, J. P.; Johnson, L. A.; Hafizi, B.; Gordon, D. F.; Penano, J. R.; Helle, M. H.; Kaganovich, D.

    2016-10-01

    A plasma channel is a cylindrical plasma column with an on-axis density minimum. A short plasma channel can focus a laser pulse in much the same manner as a conventional lens or off-axis parabola. If the plasma has an off-axis density maximum (``inverse channel''), it behaves like a negative lens and acts to defocus the pulse. In either case, a shaped plasma lens (SPL) may be placed in the beamline at locations where the laser intensity or fluence is orders of magnitude above the damage threshold for conventional solid optics. When placed after an off-axis parabola, SPLs may provide additional flexibility and spot size control and may also be useful in suppressing laser prepulse. For high power, ultrashort laser pulses, the broad laser bandwidth and extreme intensities produce chromatic and phase aberrations and amplitude distortions that degrade the lens focusing or defocusing performance. Although there have been a few experiments that demonstrate laser pulse focusing by a shaped plasma lens, generation and control of the plasma present significant challenges. Potential applications of SPLs to laser-plasma accelerators will be discussed. Supported by the Naval Research Laboratory Base Program.

  13. Novel hybrid method: pulse CO2 laser-TIG hybrid welding by coordinated control

    Institute of Scientific and Technical Information of China (English)

    Chen Yanbin; Lei Zhenglong; Li Liqun; Wu Lin; Xie Cheng

    2006-01-01

    In continuous wave CO2 laser-TIG hybrid welding process, the laser energy is not fully utilized because of the absorption and defocusing by plasma in the arc space. Therefore, the optimal welding result can only be achieved in a limited energy range. In order to improve the welding performance further, a novel hybrid welding method-pulse CO2 laser-TIG arc hybrid welding by coordinated control is proposed and investigated. The experimental results indicate that, compared with continuous wave CO2 laser-TIG hybrid welding, the absorption and defocusing of laser energy by plasma are decreased further, and at the same time, the availability ratio of laser and arc energy can be increased when a coordinated frequency is controlled. As a result, the weld appearance is also improved as well as the weld depth is deepened. Furthermore, the effect of frequency and phase of pulse laser and TIG arc on the arc images and welding characteristics is also studied. However, the novel hybrid method has great potentials in the application of industrials from views of techniques and economy.

  14. Linearly polarized pumped passively Q-switched Nd:YVO4 microchip laser for Ince-Gaussian laser modes with controllable orientations

    Science.gov (United States)

    He, Hong-Sen; Zhang, Ming-Ming; Dong, Jun; Ueda, Ken-Ichi

    2016-12-01

    A tilted, linearly polarized laser diode end-pumped Cr4+:YAG passively Q-switched a-cut Nd:YVO4 microchip laser for generating numerous Ince-Gaussian (IG) laser modes with controllable orientations has been demonstrated by selecting the crystalline orientation of an a-cut Nd:YVO4 crystal. The same IG laser mode with different orientations has been achieved with the same absorbed pump power in a passively Q-switched Nd:YVO4 microchip laser under linearly polarized pumping when the incident pump power and the crystalline orientation of an a-cut Nd:YVO4 crystal are both properly selected. The significant improvement of pulsed laser performance of controllable IG modes has been achieved by selecting the crystalline orientation of an a-cut Nd:YVO4 crystal. The maximum pulse energy is obtained along the a-axis of an a-cut Nd:YVO4 crystal and the highest peak power is achieved along the c-axis of an a-cut Nd:YVO4 crystal, respectively, which has potential applications on quantum computation and optical manipulation. The generation of controllable IG laser modes in microchip lasers under linearly polarized pumping provides a convenient and universal way to control IG laser mode numbers with anisotropic crystal as a gain medium.

  15. Optical properties of carbon nanostructures produced by laser irradiation on chemically modified multi-walled carbon nanotubes

    Science.gov (United States)

    Santiago, Enrique Vigueras; López, Susana Hernández; Camacho López, Marco A.; Contreras, Delfino Reyes; Farías-Mancilla, Rurik; Flores-Gallardo, Sergio G.; Hernández-Escobar, Claudia A.; Zaragoza-Contreras, E. Armando

    2016-10-01

    This research focused on the nanosecond (Nd: YAG-1064 nm) laser pulse effect on the optical and morphological properties of chemically modified multi-walled carbon nanotubes (MWCNT). Two suspensions of MWCNT in tetrahydrofuran (THF) were prepared, one was submitted to laser pulses for 10 min while the other (blank) was only mechanically homogenized during the same time. Following the laser irradiation, the suspension acquired a yellow-amber color, in contrast to the black translucent appearance of the blank. UV-vis spectroscopy confirmed this observation, showing the blank a higher absorption. Additionally, photoluminescence measurements exhibited a broad blue-green emission band both in the blank and irradiated suspension when excited at 369 nm, showing the blank a lower intensity. However, a modification in the excitation wavelength produced a violet to green tuning in the irradiated suspension, which did not occur in the blank. Lastly, the electron microscopy analysis of the treated nanotubes showed the abundant formation of amorphous carbon, nanocages, and nanotube unzipping, exhibiting the intense surface modification produced by the laser pulse. Nanotube surface modification and the coexistence with the new carbon nanostructures were considered as the conductive conditions for optical properties modification.

  16. Laser controlled deposition of metal microstructures via nondiffracting Bessel beam illumination

    Science.gov (United States)

    Drampyan, Rafael; Leonov, Nikita; Vartanyan, Tigran

    2016-04-01

    The technique of the laser controlled deposition of sodium and rubidium deposits on the sapphire substrate is presented. The metals were deposited on the clean sapphire substrate from the vapor phase contained in the evacuated and sealed cell. We use an axicon to produce a non-diffracting Bessel beam out of the beam got from the cw diode laser with 200 mW power at the wavelength of 532 nm. After 30 minutes of the laser-controlled deposition the substrates were examined in the optical microscope. The obtained metal deposits form the sharp-cut circles with the pitch of 10 μm, coincident with the tens of dark rings of the Bessel beam. Reduction of the laser power leads to the build up of the continuous metal film over the whole substrate.

  17. Double threshold behavior in a resonance-controlled ZnO random laser

    Science.gov (United States)

    Niyuki, Ryo; Fujiwara, Hideki; Nakamura, Toshihiro; Ishikawa, Yoshie; Koshizaki, Naoto; Tsuji, Takeshi; Sasaki, Keiji

    2017-03-01

    We observed unusual lasing characteristics, such as double thresholds and blue-shift of lasing peak, in a resonance-controlled ZnO random laser. From the analysis of lasing threshold carrier density, we found that the lasing at 1st and 2nd thresholds possibly arises from different mechanisms; the lasing at 1st threshold involves exciton recombination, whereas the lasing at 2nd threshold is caused by electron-hole plasma recombination, which is the typical origin of conventional random lasers. These phenomena are very similar to the transition from polariton lasing to photon lasing observed in a well-defined cavity laser.

  18. Control of photoassociation reaction F+H→HF with ultrashort laser pulse

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The laser-induced vibrational state-selectivity of product HF in photoassociation reaction H+F→HF is theoretically investigated by using the time-dependent quantum wave packet method. The population transfer process from the continuum state down to the bound vibrational states can be controlled by the driving laser. The effects of laser pulse parameters and the initial momentum of the two collision atoms on the vibrational population of the product HF are discussed in detail. Photodissociation accompanied with the photoassociation process is also described.

  19. Feedback Control of Laser Welding Based on Frequency Analysis of Light Emissions and Adaptive Beam Shaping

    Science.gov (United States)

    Mrňa, L.; Šarbort, M.; Řeřucha, Š.; Jedlička, P.

    This paper presents a novel method for optimization and feedback control of laser welding process. It is based on frequency analysis of the light emitted during the process and adaptive shaping of the laser beam achieved by an active optical element. Experimentally observed correlations between the focal properties of the laser beam, the weld depth and the frequency characteristics of the light emissions, which form the basis of the method, are discussed in detail. The functionality and the high efficiency of the method are demonstrated for a variety of welding parameters settings usually used in industrial practice.

  20. Temporal measures and controls in ultrafast laser domain; Mesures et controles temporels dans le domaine des lasers ultrabrefs

    Energy Technology Data Exchange (ETDEWEB)

    Oksenhendler, Th

    2004-12-15

    This work presents the development of a streak camera 'jitter free' sweep unit synchronized on a femtosecond laser. This application of high voltage photoconductive switches ('High voltage Auston switch') yields subpicosecond resolution for accumulated images on streak camera on a few hundreds micro joule femtosecond laser. Two others applications of these photoconductive switches are studied: - ultrafast optical commutation by a Pockels cell directly driven by a photoconductive switch (rising edge < 100 ps and jitter < 2 ps), - laser pulse energy self-stabilization experimentally proving that driving a Pockels cell by a photoconductive switch can increase the stability of the laser pulse energy from 7 % to 0.7 % rms. Additionally, the application of the acoustic-optical programmable dispersive filter (Dazzler) to the self referenced spectral phase measurement is presented. As these measurements require a linear filter combined with a non linear filter, it is possible to replace the complete linear part (generally a complex optical set-up) by the Dazzler leading to new kind of linear filters and new measurements. Thus base band autocorrelation and time-domain SPIDER (SPIDER by Fourier transform spectroscopy) have been demonstrated experimentally for the first time. (author)

  1. Electron dynamics in RF sources with a laser controlled emission

    CERN Document Server

    Khodak, I V; Metrochenko, V V

    2001-01-01

    Photoemission radiofrequency (RF) electron sources are sources of electron beams with extremely high brightness. Beam bunching processes in such devices are well studied in case when laser pulse duration is much lower of rf oscillation period.At the same time photoemission RF guns have some merits when operating in 'long-pulse' mode. In this case the laser pulse duration is much higher of rf oscillation period but much lower of rise time of oscillations in a gun cavity. Beam parameters at the gun output are compared for photoemission and thermoemission cathode applications. The paper presents results of a beam dynamics simulation in such guns with different resonance structures. Questions connected with defining of the current pulse peak value that can be obtained in such guns are discussed.

  2. Improved Beam Jitter Control Methods for High Energy Laser Systems

    Science.gov (United States)

    2009-12-01

    REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour...7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. 239-18 ii THIS PAGE INTENTIONALLY LEFT BLANK iii Approved for public...Gyro FSM Fast Steering Mirror FX-LMS Filtered-X Least Mean Squares FX-RLS Filtered-X Recursive Least Square HEL High Energy Laser JCT

  3. Control of Hazards to Health From Laser Radiation

    Science.gov (United States)

    2006-01-01

    ocular media and at the retina. (See chapter 7 for a discussion on laser eye protective devices.) Figure 3–3. Absorption of electromagnetic...and does not include other nonbeam hazards. HCLSs manufactured or marketed in the United States for the U.S. Army must comply with all provisions of...USAMRD–WRAIR Ocular via the staff duty officer (DSN b. Information to be reported wil (1) Patient name, grade, and socia (2) Unit name

  4. Laser-induced jetting and controlled droplet formation

    Science.gov (United States)

    Pascu, Mihail Lucian; Andrei, Ionut Relu; Delville, Jean-Pierre

    2016-12-01

    The article reports, in the general context of developing techniques to generate microjets, nanojets and even individual nanodroplets, a new method to obtain such formations by interaction of a single laser pulse at 532 nm with an individual/single mother droplet in pendant position in open air. The beam energy per pulse is varied between 0.25 and 1 mJ, the focus diameter is 90 μm, and the droplet's volumes are either 3 μl or 3.5 μl. Droplet's shape evolution and jet emission at impact with laser pulse was visualised with a high speed camera working at 10 kfps. Reproducible jets and/or separated microdroplets and nanodroplets are obtained which shows potential for applications in particular in jet printing. It is demonstrated that it becomes possible to play with the geometrical symmetry of both laser excitation and liquid in order to manage the number and the orientation of an induced microjet and consequently to actuate the orientation and the production of nanodroplets by light.

  5. Control strategies for laser separation of carbon isotopes

    Indian Academy of Sciences (India)

    V Parthasarathy; A K Nayak; S K Sarkar

    2002-12-01

    Laser isotope separation (LIS) by infrared laser chemistry of polyatomic molecules has come a long way since its discovery. The last decade has seen considerable efforts in scaling up of the process for light elements like carbon, oxygen and silicon. These efforts aim at ways to improve both the enrichment factor and the throughput. The achievement is quite significant especially for carbon isotope separation wherein macroscopic operating scales have been realized. We report our studies on the IR laser chemistry of two promising systems, viz. neat CF2HCl and CF3Br/Cl2. We have investigated conditions for optimizing the dissociation yield and selectivity using natural samples containing 1.1 % C-13. We also highlight our current efforts for scaling up the process. These include the design aspects of a photochemical reactor with multipass refocusing Herriott optics for efficient photon utilization, development of a cryogenic distillation set up and a preparative gas chromatograph for large scale separation/collection of the isotopically enriched photoproduct in the post-irradiation stage.

  6. Controllable assembly of silver nanoparticles induced by femtosecond laser direct writing

    OpenAIRE

    Wang, Huan; Liu, Sen; Zhang, Yong-Lai; Wang, Jian-Nan; Wang, Lei; Xia,Hong; Chen, Qi-Dai; Ding, Hong; Sun, Hong-Bo

    2015-01-01

    We report controllable assembly of silver nanoparticles (Ag NPs) for patterning of silver microstructures. The assembly is induced by femtosecond laser direct writing (FsLDW). A tightly focused femtosecond laser beam is capable of trapping and driving Ag NPs to form desired micropatterns with a high resolution of ∼190 nm. Taking advantage of the ‘direct writing’ feature, three microelectrodes have been integrated with a microfluidic chip; two silver-based microdevices including a microheater ...

  7. Design of optimal laser pulses to control molecular rovibrational excitation in a heteronuclear diatomic molecule

    Indian Academy of Sciences (India)

    Sitansh Sharma; Gabriel G Balint-Kurti; Harjinder Singh

    2012-01-01

    Optimal control theory in combination with time-dependent quantum dynamics is employed to design laser pulses which can perform selective vibrational and rotational excitations in a heteronuclear diatomic system. We have applied the conjugate gradient method for the constrained optimization of a suitably designed functional incorporating the desired objectives and constraints. Laser pulses designed for several excitation processes of the molecule were able to achieve predefined dynamical goals with almost 100% yield.

  8. Design of a CO2 laser power control system for a Spacelab microgravity experiment

    Science.gov (United States)

    Wenzler, Carl J.; Eichenberg, Dennis J.

    1990-01-01

    The surface tension driven convection experiment (STDCE) is a Space Transportation System flight experiment manifested to fly aboard the USML-1 Spacelab mission. A CO2 laser is used to heat a spot on the surface of silicone oil contained inside a test chamber. Several CO2 laser control systems were evaluated and the selected system will be interfaced with the balance of the experimental hardware to constitute a working engineering model. Descriptions and a discussion of these various design approaches are presented.

  9. Controlling the Direct Laser Acceleration Inside a Plasma Bubble Using Lasers' Polarization and Wavelength

    Science.gov (United States)

    Zhang, Xi; Khudik, Vladimir; Zgadzaj, Rafal; Bernstein, Aaron; Downer, Mike; Shvets, Gennady

    2016-10-01

    The combination of the direct laser acceleration and laser wakefield acceleration (DLA and LWFA) mechanisms has been recently proposed for increasing the total electron energy gain. Here we will report on the effects of the polarization and wavelength of the DLA pulse on the properties of the accelerated beam. Specifically, we address the moderate-power regime, where the laser powers of the leading LWFA and the trailing DLA pulses are not very much larger than the critical power. Three cases will be discussed: (a) the DLA pulse has the same wavelength and polarization as the LWFA pulse, (b) the wavelengths are the same but the polarizations are orthogonal, and (c) the wavelength of the DLA pulse is twice shorter than that of the LWFA pulse. LWFA via particle-in-cell (PIC) simulations. It is found that both (b) and (c) scenarios result in higher tolerance to pulse-delay jitter. The most promising scenario is (c) because it enables higher final electron bunch energy and charge. This work is supported by the US DOE Grant DE-SC0007889 and the AFOSR Grant FA9550-14-1-0045.

  10. Experimental study and chemical application of GaAs semiconductor laser treating trigeminal neuralgia

    Science.gov (United States)

    Qiu, Ke-Qum; Cao, Shu-Chen; Wang, Hu-Zhong; Wang, Ke-Ning; Xiao, Ton-Ha; Shen, Ke-Wei

    1993-03-01

    GaAs semiconductor laser was used to treat trigeminal neuralgia with an effective rate of 91.1%, and no side effects were found in 67 cases. Changes in and the recovery of the trigeminal nerve cell were studied with light and electromicroscope. Discussed in this article are the time length and quantity of laser treatment with low power. Experimental study and clinical application of the GaAs semiconductor laser have been carried out in our department since 1987. One-hundred-fifteen patients with various diseases in the maxillofacial region (including 67 cases of trigeminal neuralgia) have been treated with satisfactory effects and without any side-effects. The wavelength of the laser is 904 mu, the largest pulse length is 200 mu, and the average power is 2000 HZ.

  11. Effect of Process Parameter in Laser Cutting of PMMA Sheet and ANFIS Modelling for Online Control

    Directory of Open Access Journals (Sweden)

    Hossain Anamul

    2016-01-01

    Full Text Available Laser beam machining (LBM is a promising and high accuracy machining technology in advanced manufacturing process. In LBM, crucial machining qualities of the end product include heat affected zone, surface roughness, kerf width, thermal stress, taper angle etc. It is essential for industrial applications especially in laser cutting of thermoplastics to acquire output product with minimum kerf width. The kerf width is dependent on laser input parameters such as laser power, cutting speed, standoff distance, assist gas pressure etc. However it is difficult to get a functional relationship due to the high uncertainty among these parameters. Hence, total 81 sets of full factorial experiment were conducted, representing four input parameters with three different levels. The experiments were performed by a continuous wave (CW CO2 laser with the mode structure of TEM01 named Zech laser machine that can provide maximum laser power up to 500 W. The polymethylmethacrylate (PMMA sheet with thickness of 3.0 mm was used for this experiment. Laser power, cutting speed, standoff distance and assist gas pressure were used as input parameters for the output named kerf width. Standoff distance, laser power, cutting speed and assist gas pressure have the dominant effect on kerf width, respectively, although assist gas has some significant effect to remove the harmful gas. ANFIS model has been developed for online control purposes. This research is considered important and helpful for manufacturing engineers in adjusting and decision making of the process parameters in laser manufacturing industry of PMMA thermoplastics with desired minimum kerf width as well as intricate shape design purposes.

  12. Compatible biological and chemical control systems for Rhizoctonia solani in potato

    NARCIS (Netherlands)

    Boogert, van den P.H.J.F.; Luttikholt, A.J.G.

    2004-01-01

    A series of chemical and biological control agents were tested for compatibility with the Rhizoctonia-specific biocontrol fungus Verticillium biguttatum aimed at designing novel control strategies for black scurf (Rhizoctonia solani) and other tuber diseases in potato. The efficacy of chemicals, alo

  13. Chemical and physical processes for integrated temperature control in microfluidic devices

    NARCIS (Netherlands)

    Guijt, Rosanne M.; Dodge, Arash; Van Dedem, Gijs W. K.; De Rooij, Nico F.; Verpoorte, Elisabeth

    2003-01-01

    Microfluidic devices are a promising new tool for studying and optimizing (bio)chemical reactions and analyses. Many (bio)chemical reactions require accurate temperature control, such as for example thermocycling for PCR. Here, a new integrated temperature control system for microfluidic devices is

  14. STM CONTROL OF CHEMICAL REACTIONS: Single-Molecule Synthesis

    Science.gov (United States)

    Hla, Saw-Wai; Rieder, Karl-Heinz

    2003-10-01

    The fascinating advances in single atom/molecule manipulation with a scanning tunneling microscope (STM) tip allow scientists to fabricate atomic-scale structures or to probe chemical and physical properties of matters at an atomic level. Owing to these advances, it has become possible for the basic chemical reaction steps, such as dissociation, diffusion, adsorption, readsorption, and bond-formation processes, to be performed by using the STM tip. Complete sequences of chemical reactions are able to induce at a single-molecule level. New molecules can be constructed from the basic molecular building blocks on a one-molecule-at-a-time basis by using a variety of STM manipulation schemes in a systematic step-by-step manner. These achievements open up entirely new opportunities in nanochemistry and nanochemical technology. In this review, various STM manipulation techniques useful in the single-molecule reaction process are reviewed, and their impact on the future of nanoscience and technology are discussed.

  15. Quantum-State Controlled Chemical Reactions of Ultracold KRb Molecules

    CERN Document Server

    Ospelkaus, S; Wang, D; de Miranda, M H G; Neyenhuis, B; Quéméner, G; Julienne, P S; Bohn, J L; Jin, D S; Ye, J

    2009-01-01

    How does a chemical reaction proceed at ultralow temperatures? Can simple quantum mechanical rules such as quantum statistics, single scattering partial waves, and quantum threshold laws provide a clear understanding for the molecular reactivity under a vanishing collision energy? Starting with an optically trapped near quantum degenerate gas of polar $^{40}$K$^{87}$Rb molecules prepared in their absolute ground state, we report experimental evidence for exothermic atom-exchange chemical reactions. When these fermionic molecules are prepared in a single quantum state at a temperature of a few hundreds of nanoKelvins, we observe p-wave-dominated quantum threshold collisions arising from tunneling through an angular momentum barrier followed by a near-unity probability short-range chemical reaction. When these molecules are prepared in two different internal states or when molecules and atoms are brought together, the reaction rates are enhanced by a factor of 10 to 100 due to s-wave scattering, which does not ...

  16. FPGA-BASED CONTROL OF THERMOELECTRIC COOLERS FOR LASER DIODE TEMPERATURE REGULATION

    Directory of Open Access Journals (Sweden)

    AHTESHAM ALI

    2012-04-01

    Full Text Available The proportional-integral-derivative (PID controller is the most used controller in the industry. Field programmable gate arrays (FPGAs allow efficient implementation of PID controllers. This paper presents the temperature regulation of a 48W laser diode through thermoelectric coolers (TECs. The temperature regulation system is designed and tested. The results demonstrate the feasibility and applicability of PID control through FPGA.

  17. Control of Dermatomycoses by Physical, Chemical and Biological Agents.

    Science.gov (United States)

    1978-10-31

    were purchased from Sigma Chemical Co. (St. Louis , Mo.). Lycopene was Isolated from tomato according to the method described by Weedor (22...Bacteriol . To E~e pub1Ished in December 1978. 4. Emyanitoff, R. G. and 1. ~1ashimoto . The effect of temperature ,Incubation atmosphere and medium

  18. Development of a dual joystick-controlled laser trapping and cutting system for optical micromanipulation of chromosomes inside living cells.

    Science.gov (United States)

    Harsono, Marcellinus S; Zhu, Qingyuan; Shi, Linda Z; Duquette, Michelle; Berns, Michael W

    2013-02-01

    A multi-joystick robotic laser microscope system used to control two optical traps (tweezers) and one laser scissors has been developed for subcellular organelle manipulation. The use of joysticks has provided a "user-friendly" method for both trapping and cutting of organelles such as chromosomes in live cells. This innovative design has enabled the clean severing of chromosome arms using the laser scissors as well as the ability to easily hold and pull the severed arm using the laser tweezers.

  19. Optical mode control of surface-plasmon quantum cascade lasers

    Science.gov (United States)

    Moreau, V.; Bahriz, M.; Palomo, J.; Wilson, L. R.; Krysa, A. B.; Sirtori, C.; Austin, D. A.; Cockburn, J. W.; Roberts, J. S.; Colombelli, R.

    2007-04-01

    Surface-plasmon waveguides based on metallic strips can provide a two dimensional optical confinement. This concept has been successfully applied to quantum cascade lasers, processed as ridge waveguides, to demonstrate that the lateral extension of the optical mode can be influenced solely by the width of the device top contact. For devices operating at a wavelength of λ ≈7.5 μm, the room-temperature threshold current density was reduced from 6.3 kA/cm2 to 4.4 kA/cm2 with respect to larger devices with full top metallization.

  20. Methods and system for controlled laser-driven explosive bonding

    Energy Technology Data Exchange (ETDEWEB)

    Rubenchik, Alexander M.; Farmer, Joseph C.; Hackel, Lloyd; Rankin, Jon

    2015-11-19

    A technique for bonding two dissimilar materials includes positioning a second material over a first material at an oblique angle and applying a tamping layer over the second martial. A laser beam is directed at the second material that generates a plasma at the location of impact on the second material. The plasma generates pressure that accelerates a portion of the second material to a very high velocity and towards the first material. The second material impacts the first material causing bonding of the two materials.

  1. Effects of the Spectral Line Broadened Model on the Performance of a Flowing Chemical Oxygen-Iodine Laser

    Institute of Scientific and Technical Information of China (English)

    高智; 胡利民

    2002-01-01

    A new gain saturation model of chemical oxygen-iodine lasers (COILs) is deduced from the conservation equations of the population number of upper and lower lasing levels. The present model is compared with both the Voigt profile function model and its low-pressure limit model. The differences between the Voigt profile function model or its low-pressure limit model and the model presented here are pointed out, such as the length of power extraction, the optimal range of the threshold gain. These differences are useful for the optimization of COIL adjustable parameters.

  2. Accumulation boundaries: codimension-two accumulation of accumulations in phase diagrams of semiconductor lasers, electric circuits, atmospheric and chemical oscillators.

    Science.gov (United States)

    Bonatto, Cristian; Gallas, Jason Alfredo Carlson

    2008-02-28

    We report high-resolution phase diagrams for several familiar dynamical systems described by sets of ordinary differential equations: semiconductor lasers; electric circuits; Lorenz-84 low-order atmospheric circulation model; and Rössler and chemical oscillators. All these systems contain chaotic phases with highly complicated and interesting accumulation boundaries, curves where networks of stable islands of regular oscillations with ever-increasing periodicities accumulate systematically. The experimental exploration of such codimension-two boundaries characterized by the presence of infinite accumulation of accumulations is feasible with existing technology for some of these systems.

  3. High-power supersonic chemical lasers: gas-dynamic problems of operation of mobile systems with PRS

    Science.gov (United States)

    Boreysho, A. S.; Malkov, V. M.; Savin, A. V.

    2008-10-01

    Supersonic chemical lasers, such as HF /DF and COIL, have always been in the focus of special interest as the most powerful sources of continuous wave generation. Presently, autonomous mobile laser complexes (both air- and landbased) are being developed on the basis of SCL [1-3]. It is commonly accepted that SCL appeared, conditionally speaking, at the crossroads of a number of sciences: of physics - quantum electronics and physical kinetics; chemistry - combustion theory and chemical kinetics; classic optics - theory of resonators, aero-optics, and gas dynamics (there is a supersonic flow in the SCL channel). Due to this fact, all tasks and problems which could be resolved in the course of SCL development have complex character and could be considered as the next stage of complexity in comparison with the well known similar tasks which had been considered earlier. This is why they should be resolved anew with consideration of the specific aspects of the SCL processes. This is true for the gas-dynamic problems: new parameter areas, non-traditional channel geometry, consideration of new phenomena, etc.Supersonic chemical lasers, such as HF /DF and COIL, have always been in the focus of special interest as the most powerful sources of continuous wave generation. Presently, autonomous mobile laser complexes (both air- and landbased) are being developed on the basis of SCL [1-3]. It is commonly accepted that SCL appeared, conditionally speaking, at the crossroads of a number of sciences: of physics - quantum electronics and physical kinetics; chemistry - combustion theory and chemical kinetics; classic optics - theory of resonators, aero-optics, and gas dynamics (there is a supersonic flow in the SCL channel). Due to this fact, all tasks and problems which could be resolved in the course of SCL development have complex character and could be considered as the next stage of complexity in comparison with the well known similar tasks which had been considered earlier

  4. Lasers.

    Science.gov (United States)

    Passeron, T

    2012-12-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  5. [Lasers].

    Science.gov (United States)

    Passeron, T

    2012-11-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  6. Control of Quantum Fluid Dynamics and Adaptive Phase Compensation for Laser Propagation in Turbulence

    Science.gov (United States)

    Gustafsson, Jonathan; Sritharan, Sivaguru S.

    2015-11-01

    Equations of High Energy Laser propagation in a turbulent medium and the equations of quantum fluid dynamics are connected through a mathematical transformation. In this way the problem of adaptive phase compensation can be phrased as an initial velocity control problem for quantum fluid dynamics. The quantum hydrodynamics equation can be derived by applying the Madelung transformation to the time-dependent linear or nonlinear Schrödinger equation. The resulting equations are similar to incompressible Euler equations with an additional term denoted the quantum pressure term. The quantum hydrodynamics equation can thus be a good way to understand adaptive optics and laser propagation through the atmosphere. A Riemann solver within the Clawpack framework has been developed. An initial value optimization problem will be solved using adjoint methods. The initial phase can be controlled when the beam leaves the laser appartus. The control method can also be coupled to a Navier-Stokes solver in order to study thermal blooming where the laser heats the air and changes the index of refraction. The change in refractive index will in turn affect the propagation of the Laser beam. Using optimal control techniques, it is possible to adjust the beam in order to compensate for the heating.

  7. The chemical digestion of Ti6Al7Nb scaffolds produced by Selective Laser Melting reduces significantly ability of Pseudomonas aeruginosa to form biofilm.

    Science.gov (United States)

    Junka, Adam F; Szymczyk, Patrycja; Secewicz, Anna; Pawlak, Andrzej; Smutnicka, Danuta; Ziółkowski, Grzegorz; Bartoszewicz, Marzenna; Chlebus, Edward

    2016-01-01

    In our previous work we reported the impact of hydrofluoric and nitric acid used for chemical polishing of Ti-6Al-7Nb scaffolds on decrease of the number of Staphylococcus aureus biofilm forming cells. Herein, we tested impact of the aforementioned substances on biofilm of Gram-negative microorganism, Pseudomonas aeruginosa, dangerous pathogen responsible for plethora of implant-related infections. The Ti-6Al-7Nb scaffolds were manufactured using Selective Laser Melting method. Scaffolds were subjected to chemical polishing using a mixture of nitric acid and fluoride or left intact (control group). Pseudomonal biofilm was allowed to form on scaffolds for 24 hours and was removed by mechanical vortex shaking. The number of pseudomonal cells was estimated by means of quantitative culture and Scanning Electron Microscopy. The presence of nitric acid and fluoride on scaffold surfaces was assessed by means of IR and rentgen spetorscopy. Quantitative data were analysed using the Mann-Whitney test (P ≤ 0.05). Our results indicate that application of chemical polishing correlates with significant drop of biofilm-forming pseudomonal cells on the manufactured Ti-6Al-7Nb scaffolds ( p = 0.0133, Mann-Whitney test) compared to the number of biofilm-forming cells on non-polished scaffolds. As X-ray photoelectron spectroscopy revealed the presence of fluoride and nitrogen on the surface of scaffold, we speculate that drop of biofilm forming cells may be caused by biofilm-supressing activity of these two elements.

  8. Controllable generation of reactive oxygen species by femtosecond-laser irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Wei; He, Hao, E-mail: haohe@tju.edu.cn; Wang, Yintao; Wang, Yisen; Hu, Minglie; Wang, Chingyue [Ultrafast Laser Laboratory, Key Laboratory of Optoelectronic Information Technology (Ministry of Education), College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin (China)

    2014-02-24

    Femtosecond lasers have been advancing Biophotonics research in the past two decades with multiphoton microscopy, microsurgery, and photodynamic therapy. Nevertheless, laser irradiation is identified to bring photodamage to cells via reactive oxygen species (ROS) generation with unclear mechanism. Meanwhile, currently in biological researches, there is no effective method to provide controllable ROS production precisely, which originally is leaked from mitochondria during respiration and plays a key role in a lot of important cellular processes and cellular signaling pathways. In this study, we show the process of how the tightly focused femtosecond-laser induces ROS generation solely in mitochondria at the very beginning and then release to cytosol if the stimulus is intense enough. At certain weak power levels, the laser pulses induce merely moderate Ca{sup 2+} release but this is necessary for the laser to generate ROS in mitochondria. Cellular original ROS are also involved with a small contribution. When the power is above a threshold, ROS are then released to cytosol, indicating photodamage overwhelming cellular repair ability. The mechanisms in those two cases are quite different. Those results clarify parts of the mechanism in laser-induced ROS generation. Hence, it is possible to further this optical scheme to provide controllable ROS generation for ROS-related biological researches including mitochondrial diseases and aging.

  9. Polarization and wavelength insensitive optical feedback control systems for stabilizing CO2 lasers

    Science.gov (United States)

    Jebali, M. A.

    2016-03-01

    Power scaling of multi-kilowatt fiber lasers has been driving the development of glass and fiber processing technology. Designed for processing of large diameter fibers, this technology is used for the fabrication of fiber-based components such as end-pump and side pump combiners, large diameter endcaps, ball lenses for collimators and focusers… The use of 10.6um CO2 lasers as a heating element provides incomparable flexibility, process control and repeatability when compared to conventional heating methods. This low maintenance technology provides an accurate, adjustable and uniform heating area by absorption of fused silica of the 10.6m laser radiation. However, commercially available CO2 lasers can experience power, polarization and mode instability, which becomes important at 20W levels and higher of output power. This paper presents a polarization and wavelength insensitive optical feedback control system for stabilizing commercially available CO2 lasers. Less than 1% power fluctuation was achieved at different laser power levels, ranging from as 5 to 40W.

  10. Laser driven self-assembly of shape-controlled potassium nanoparticles in porous glass

    CERN Document Server

    Marmugi, L; Burchianti, A; Veronesi, S; Moi, L; Marinelli, C

    2014-01-01

    We observe growth of shape-controlled potassium nanoparticles inside a random network of glass nanopores, exposed to low-power laser radiation. Visible laser light plays a dual role: it increases the desorption probability of potassium atoms from the inner glass walls and induces the self-assembly of metastable metallic nanoparticles along the nanopores. By probing the sample transparency and the atomic light-induced desorption flux into the vapour phase, the dynamics of both cluster formation/evaporation and atomic photo-desorption processes are characterized. Results indicate that laser light not only increases the number of nanoparticles embedded in the glass matrix but also influences their structural properties. By properly choosing the laser frequency and the illumination time, we demonstrate that it is possible to tailor the nanoparticles'shape distribution. Furthermore, a deep connection between the macroscopic behaviour of atomic desorption and light-assisted cluster formation is observed. Our result...

  11. Transverse-mode controlling of a large-mode-area multimode fiber laser

    Institute of Scientific and Technical Information of China (English)

    Libo Li; Qihong Lou; Jun Zhou; Jingxing Dong; Yunrong Wei; Bing He; Jinyan Li

    2007-01-01

    @@ Coiling technique is used to control the transverse mode of a large-mode-area (LMA) multimode fiber laser. By winding the fiber to a coil with different radius, high-order modes of a multimode fiber laser are suppressed one by one and finally 15.4-W single-transverse-mode output is achieved when the coil radius is 20 mm. It is found that as the coil radius decreases, the beam quality of a multimode fiber laser gets better but the slope efficiency drops for higher-order modes are discriminated. During the experiment, as the coil radius of multimode fiber changes, output characteristic of the laser has been measured. Meanwhile,the mode loss of different modes is calculated theoretically. It is proved that the experimental measured results fit well with the theoretically calculated results.

  12. Enhancement of Laser Power Efficiency by Control of Spatial Hole Burning Interactions

    CERN Document Server

    Ge, Li; Tureci, Hakan E

    2014-01-01

    The laser is an out-of-equilibrium nonlinear wave system where the interplay of the cavity geometry and nonlinear wave interactions, mediated by the gain medium, determines the self-organized oscillation frequencies and the associated spatial field patterns. In the steady state, a constant energy flux flows through the laser from the pump to the far field, with the ratio of the total output power to the input power determining the power-efficiency. While nonlinear wave interactions have been modeled and well understood since the early days of laser theory, their impact on the power-efficiency of a laser system is poorly understood. Here, we show that spatial hole burning interactions generally decrease the power efficiency. We then demonstrate how spatial hole burning interactions can be controlled by a spatially tailored pump profile, thereby boosting the power-efficiency, in some cases by orders of magnitude.

  13. Simple locking of infrared and ultraviolet diode lasers to a visible laser using a LabVIEW proportional-integral-derivative controller on a Fabry-Perot signal

    Science.gov (United States)

    Kwolek, J. M.; Wells, J. E.; Goodman, D. S.; Smith, W. W.

    2016-05-01

    Simultaneous laser locking of infrared (IR) and ultraviolet lasers to a visible stabilized reference laser is demonstrated via a Fabry-Perot (FP) cavity. LabVIEW is used to analyze the input, and an internal proportional-integral-derivative algorithm converts the FP signal to an analog locking feedback signal. The locking program stabilized both lasers to a long term stability of better than 9 MHz, with a custom-built IR laser undergoing significant improvement in frequency stabilization. The results of this study demonstrate the viability of a simple, computer-controlled, non-temperature-stabilized FP locking scheme for our applications, laser cooling of Ca+ ions, and its use in other applications with similar modest frequency stabilization requirements.

  14. Locking IR and UV diode lasers to a visible laser using a LabVIEW PID controller on a Fabry-Perot signal

    CERN Document Server

    Kwolek, J M; Goodman, D S; Smith, W W

    2015-01-01

    Simultaneous laser locking of IR and UV lasers to a visible reference laser is demonstrated via a Fabry-Perot cavity. LabVIEW is used to analyze the input and an internal PID algorithm converts the Fabry-Perot signal to an analog locking feedback signal. The locking program stabilized both lasers to a long term stability of less than 12 MHz, with the lab-built IR laser undergoing signi?cant improvement in frequency stabilization. The results of this study demonstrate the viability of a simple computer-controlled, non temperature-stabilized Fabry-Perot locking scheme for our applications, laser cooling of Ca+ ions, and its use in other applications with similar modest frequency stabilization requirements.

  15. Simple locking of infrared and ultraviolet diode lasers to a visible laser using a LabVIEW proportional-integral-derivative controller on a Fabry-Perot signal.

    Science.gov (United States)

    Kwolek, J M; Wells, J E; Goodman, D S; Smith, W W

    2016-05-01

    Simultaneous laser locking of infrared (IR) and ultraviolet lasers to a visible stabilized reference laser is demonstrated via a Fabry-Perot (FP) cavity. LabVIEW is used to analyze the input, and an internal proportional-integral-derivative algorithm converts the FP signal to an analog locking feedback signal. The locking program stabilized both lasers to a long term stability of better than 9 MHz, with a custom-built IR laser undergoing significant improvement in frequency stabilization. The results of this study demonstrate the viability of a simple, computer-controlled, non-temperature-stabilized FP locking scheme for our applications, laser cooling of Ca(+) ions, and its use in other applications with similar modest frequency stabilization requirements.

  16. Computational molecular technology towards macroscopic chemical phenomena-molecular control of complex chemical reactions, stereospecificity and aggregate structures

    Energy Technology Data Exchange (ETDEWEB)

    Nagaoka, Masataka [Graduate School of Information Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601 (Japan); Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Honmachi, Kawaguchi 332-0012 (Japan); ESICB, Kyoto University, Kyodai Katsura, Nishikyo-ku, Kyoto 615-8520 (Japan)

    2015-12-31

    A new efficient hybrid Monte Carlo (MC)/molecular dynamics (MD) reaction method with a rare event-driving mechanism is introduced as a practical ‘atomistic’ molecular simulation of large-scale chemically reactive systems. Starting its demonstrative application to the racemization reaction of (R)-2-chlorobutane in N,N-dimethylformamide solution, several other applications are shown from the practical viewpoint of molecular controlling of complex chemical reactions, stereochemistry and aggregate structures. Finally, I would like to mention the future applications of the hybrid MC/MD reaction method.

  17. Magneto-optic Crystal Polarization Controller Assisted Mode-Locked Fiber Laser

    Institute of Scientific and Technical Information of China (English)

    ZHAO Guang-Zhen; GUI Li-Li; XIAO Xiao-Sheng; YANG Chang-Xi

    2011-01-01

    We report a passively mode-locked erbium-doped fiber laser based on a compact magneto-optic crystal polarization controller. The length of the polarization controller consisting of four magneto-optic crystal rotators and two quarter wave-plates is only 10cm.Adjusting the polarization controller, central wavelength around 1559nm and repetition rate 21.10 MHz mode-locked pulse are obtained. Pulse duration and 3 dB spectrum width are 598.4fs and 6.24nm respectively. Single pulse energy is about 151.7pJ. Because of its small size, low insertion loss,good controllability and negligible dispersion, the magneto-optic crystal polarization controller could be an ideal polarization controller in fiber lasers.

  18. Higher order sliding mode control of laser pointing for orbital debris mitigation

    Science.gov (United States)

    Palosz, Arthur

    This thesis explores the use of a space-based laser to clean up small orbital debris from near Earth space. This system's challenge is to quickly and precisely aim the laser beam at very small (Kalman Filter (KF) is designed to accurately track the orbital debris and generate a command signal for the controller. A second order Super Twisting Sliding Mode Controller (2-SMC) is designed to follow the command signal generated by the KF and to overcome the parametric uncertainties and external disturbances. The performance of the system is validated with a computer simulation created in MATLAB and Simulink.

  19. A simple readout electronics for automatic power controlled self-mixing laser diode systems.

    Science.gov (United States)

    Cattini, Stefano; Rovati, Luigi

    2008-08-01

    The paper describes a simple electronic circuit to drive a laser diode for self-mixing interferometry. The network integrates a stable commercial automatic power controller and a current mirror based readout of the interferometric signal. The first prototype version of the circuit has been realized and characterized. The system allows easily performing precise interferometric measurements with no thermostatic circuitry to stabilize the laser diode temperature and an automatic control gain network to compensate emitted optical power fluctuations. To achieve this result, in the paper a specific calibration procedure to be performed is described.

  20. Indoor SLAM Using Laser and Camera with Closed-Loop Controller for NAO Humanoid Robot

    Directory of Open Access Journals (Sweden)

    Shuhuan Wen

    2014-01-01

    Full Text Available We present a SLAM with closed-loop controller method for navigation of NAO humanoid robot from Aldebaran. The method is based on the integration of laser and vision system. The camera is used to recognize the landmarks whereas the laser provides the information for simultaneous localization and mapping (SLAM . K-means clustering method is implemented to extract data from different objects. In addition, the robot avoids the obstacles by the avoidance function. The closed-loop controller reduces the error between the real position and estimated position. Finally, simulation and experiments show that the proposed method is efficient and reliable for navigation in indoor environments.

  1. Experimental Observation of Laser Control: Electronic Branching in the Photodissociation of Na2

    Science.gov (United States)

    Shnitman, A.; Sofer, I.; Golub, I.; Yogev, A.; Shapiro, M.; Chen, Z.; Brumer, P.

    1996-04-01

    Control over the product branching ratio in the photodissociation of Na2 into Na\\(3s\\)+Na\\(3p\\) and Na\\(3s\\)+Na\\(3d\\) is demonstrated using a two-photon incoherent interference control scenario. Ordinary pulsed nanosecond lasers are used and Na2 is at thermal equilibrium in a heat pipe. Results show a depletion in the Na\\(3d\\) product of at least 25% and a concomitant increase in the Na\\(3p\\) yield as the relative frequency of the two lasers is scanned.

  2. Advanced design of conductive polymeric arrays with controlled electrical resistance using direct laser interference patterning

    Energy Technology Data Exchange (ETDEWEB)

    Lasagni, A.F. [Saarland University, Department of Materials Science, Chair of Functional Materials, Building C 6.3, 7. Stock, P.O. Box 15 11 50, Saarbruecken (Germany); George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA (United States); Acevedo, D.F. [Saarland University, Department of Materials Science, Chair of Functional Materials, Building C 6.3, 7. Stock, P.O. Box 15 11 50, Saarbruecken (Germany); Universidad Nacional de Rio Cuarto, Departamento de Quimica, Cordoba (Argentina); Barbero, C.A. [Universidad Nacional de Rio Cuarto, Departamento de Quimica, Cordoba (Argentina); Muecklich, F. [Saarland University, Department of Materials Science, Chair of Functional Materials, Building C 6.3, 7. Stock, P.O. Box 15 11 50, Saarbruecken (Germany)

    2008-06-15

    In this work, we report a simple method for the fabrication of regular conducting polyaniline periodic arrays on large areas of glass or gold substrates using direct laser interference patterning. Additionally, by controlling the laser intensity it is possible to precisely tune the width of the periodic arrays and consequently the electrical resistance of the polyaniline strips. The periodic arrays were characterized using scanning electron microscopy, white light interferometry and cyclic voltametry. The great importance of the method reported lies both in its versatility and the ability to control the properties of the modified polymer electrodes with high precision. This is important for prospective applications such as electrochemical sensors. (orig.)

  3. Simulations of Erosion/Corrosion Surface Chemical Reactions with a Laser Beam,

    Science.gov (United States)

    1983-11-01

    wt% in alpha iron at 875°C,s and it may be SIMS and Metallographic Observations substantially lower.9 Consequently, the high sur- face concentration of...surfaces as a result of air contamina- is of the order of 0.004 wt% in alpha iron at tion than by laser-pulsing in nitrogen and ammo- 873°C, 0.025 wt% in...that may have occurred during laser-pulsing pre- and alpha iron .1 4 sented an interesting predicament. Evidence of 44 The extensive oxidation and

  4. Monotonic convergent optimal control theory with strict limitations on the spectrum of optimized laser fields.

    Science.gov (United States)

    Gollub, Caroline; Kowalewski, Markus; de Vivie-Riedle, Regina

    2008-08-15

    We present a modified optimal control scheme based on the Krotov method, which allows for strict limitations on the spectrum of the optimized laser fields. A frequency constraint is introduced and derived mathematically correct, without losing monotonic convergence of the algorithm. The method guarantees a close link to learning loop control experiments and is demonstrated for the challenging control of nonresonant Raman transitions, which are used to implement a set of global quantum gates for molecular vibrational qubits.

  5. Electrically controllable liquid crystal random lasers below the Fréedericksz transition threshold.

    Science.gov (United States)

    Lee, Chia-Rong; Lin, Jia-De; Huang, Bo-Yuang; Lin, Shih-Hung; Mo, Ting-Shan; Huang, Shuan-Yu; Kuo, Chie-Tong; Yeh, Hui-Chen

    2011-01-31

    This investigation elucidates for the first time electrically controllable random lasers below the threshold voltage in dye-doped liquid crystal (DDLC) cells with and without adding an azo-dye. Experimental results show that the lasing intensities and the energy thresholds of the random lasers can be decreased and increased, respectively, by increasing the applied voltage below the Fréedericksz transition threshold. The below-threshold-electric-controllability of the random lasers is attributable to the effective decrease of the spatial fluctuation of the orientational order and thus of the dielectric tensor of LCs by increasing the electric-field-aligned order of LCs below the threshold, thereby increasing the diffusion constant and decreasing the scattering strength of the fluorescence photons in their recurrent multiple scattering. This can result in the decrease in the lasing intensity of the random lasers and the increase in their energy thresholds. Furthermore, the addition of an azo-dye in DDLC cell can induce the range of the working voltage below the threshold for the control of the random laser to reduce.

  6. Zebra Mussel Chemical Control Guide, Version 2.0

    Science.gov (United States)

    2015-07-01

    28 Ammonia ...controlling zebra mussels (Dreissena polymorpha): A synthesis of recent laboratory and field studies. In: Zebra mussels: Biology, impacts, and control, ed. T...15-9 18 These FAC compounds react with ammonia and other nitrogen-containing compounds to make chloramines, which also contribute to disinfection

  7. On the design of chemical processes with improved controllability characteristics

    NARCIS (Netherlands)

    Meeuse, F.M.

    2003-01-01

    Traditionally, process design and control system design are carried out sequentially. The premise underlying this sequential approach is that the decisions made in the process design phase do not limit the control design. However, it is generally known that incongruent designs can occur quite easily

  8. Chemical analysis of substrates with controlled release fertilizer

    NARCIS (Netherlands)

    Kreij, de C.

    2004-01-01

    Water-soluble fertilizer added to media containing controlled release fertilizer cannot be analysed with the 1:1.5 volume water extract, because the latter increases the element content in the extract. During storage and stirring or mixing the substrate with the extractant, part of the controlled re

  9. femtosecond laser ablation

    OpenAIRE

    Margetic, Vanja

    2003-01-01

    Femtosecond laser ablation was investigated as a solid sampling method for elemental chemical analysis. In comparison to the sampling with longer laser pulses, two aspects could be improved by using ultrashort pulses: elimination of the elemental fractionation from the ablation crater, which is necessary for an accurate quantitative analysis, and better control of the material removal (especially for metals), which increases the spatial resolution of microanalysis. Basic aspects of ultrashort...

  10. Theoretical Study of Laser-Stimulated Chemical Vapor Deposition Processes of Importance in Microelectronics.

    Science.gov (United States)

    1983-12-01

    fundamental microscopic theory for the laser-induced periodic surface structure ( LIPSS ), which includes electronic and vibrational degrees of freedom of the...deposition rate. The dynamics of subsequent multilayer LIPSS formation is treated using a metal-metal interaction potential obtained by combining MO theory

  11. Multi-Disciplinary Research for High Energy Chemical Lasers, Closed-Cycle ElectricOIL Technology

    Science.gov (United States)

    2007-10-31

    ARLINGTO 5d. PROJECT NUMBER 5o. TASK NUMBER 5f. WORK UNIT NUMBER 8. PERFORMING ORGANIZATION REPORT 10. SPONSORyMONITOR’S ACRONYM(S) USAF, AFRL...supersonic section and absorption in the subsonic section. Frequency (MHz) Laser power measurements were made with a Scientech Astral ™ model AC2500/AC25H

  12. Laser synthesis, structure and chemical properties of colloidal nickel-molybdenum nanoparticles for the substitution of noble metals in heterogeneous catalysis.

    Science.gov (United States)

    Marzun, Galina; Levish, Alexander; Mackert, Viktor; Kallio, Tanja; Barcikowski, Stephan; Wagener, Philipp

    2017-03-01

    Platinum and iridium are rare and expensive noble metals that are used as catalysts for different sectors including in heterogeneous chemical automotive emission catalysis and electrochemical energy conversion. Nickel and its alloys are promising materials to substitute noble metals. Nickel based materials are cost-effective with good availability and show comparable catalytic performances. The nickel-molybdenum system is a very interesting alternative to platinum in water electrolysis. We produced ligand-free nickel-molybdenum nanoparticles by laser ablation in water and acetone. Our results show that segregated particles were formed in water due to the oxidation of the metals. X-ray diffraction shows a significant change in the lattice parameter due to a diffusion of molybdenum atoms into the nickel lattice with increasing activity in the electrochemical oxygen evolution reaction. Even though the solubility of molecular oxygen in acetone is higher than in water, there were no oxides and a more homogeneous metal distribution in the particles in acetone as seen by TEM-EDX. This showed that dissolved molecular oxygen does not control oxide formation. Overall, the laser ablation of pressed micro particulate mixtures in liquids offers a combinational synthesis approach that allows the screening of alloy nanoparticles for catalytic testing and can convert micro-mixtures into nano-alloys.

  13. Wettability control by laser texturing process generating localized gold nanoparticles on polymeric thin films.

    Science.gov (United States)

    Spano, F; Castellano, A; Massaro, A; Fragouli, D; Cingolani, R; Athanassiou, A

    2012-06-01

    In this work a new approach is introduced for surface properties control by laser texturing process. By UV laser irradiation, we are able to control the surface wettability of a chitosan polymeric film in which is introduced a chloroauric acid salt by immersion. Specifically the UV irradiation is responsible for the creation of gold nanoparticles at the irradiated surface of the polymeric film. This photolytic process allows us to localize and design accurately surface patterns and moreover to tune metallic particle size in the range of nanoscale. After the characterization of our gold textured surfaces by atomic force and scanning electron microscopies, we demonstrate the link between wettability surface properties and gold nanoparticles size. The experimental results indicate the influence of the laser intensity, the irradiation time and the polymer film thickness (by increasing the gold concentration) on the gold nanoparticle density and size.

  14. Final Report - ADVANCED LASER-BASED SENSORS FOR INDUSTRIAL PROCESS CONTROL

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Manish; Baer, Douglas

    2013-09-30

    The objective of this work is to capture the potential of real-time monitoring and overcome the challenges of harsh industrial environments, Los Gatos Research (LGR) is fabricating, deploying, and commercializing advanced laser-based gas sensors for process control monitoring in industrial furnaces (e.g. electric arc furnaces). These sensors can achieve improvements in process control, leading to enhanced productivity, improved product quality, and reduced energy consumption and emissions. The first sensor will utilize both mid-infrared and near-infrared lasers to make rapid in-situ measurements of industrial gases and associated temperatures in the furnace off-gas. The second sensor will make extractive measurements of process gases. During the course of this DOE project, Los Gatos Research (LGR) fabricated, tested, and deployed both in-situ tunable diode laser absorption spectrometry (TDLAS) analyzers and extractive Off-Axis Integrated Cavity Output Spectroscopy (Off-Axis ICOS) analyzers.

  15. Etching and Chemical Control of the Silicon Nitride Surface.

    Science.gov (United States)

    Brunet, Marine; Aureau, Damien; Chantraine, Paul; Guillemot, François; Etcheberry, Arnaud; Gouget-Laemmel, Anne Chantal; Ozanam, François

    2017-01-25

    Silicon nitride is used for many technological applications, but a quantitative knowledge of its surface chemistry is still lacking. Native oxynitride at the surface is generally removed using fluorinated etchants, but the chemical composition of surfaces still needs to be determined. In this work, the thinning (etching efficiency) of the layers after treatments in HF and NH4F solutions has been followed by using spectroscopic ellipsometry. A quantitative estimation of the chemical bonds found on the surface is obtained by a combination of infrared absorption spectroscopy in ATR mode, X-ray photoelectron spectroscopy, and colorimetry. Si-F bonds are the majority species present at the surface after silicon nitride etching; some Si-OH and a few Si-NHx bonds are also present. No Si-H bonds are present, an unfavorable feature for surface functionalization in view of the interest of such mildly reactive groups for achieving stable covalent grafting. Mechanisms are described to support the experimental results, and two methods are proposed for generating surface SiH species: enriching the material in silicon, or submitting the etched surface to a H2 plasma treatment.

  16. Control of dynamical self-assembly of strongly Brownian nanoparticles through convective forces induced by ultrafast laser

    Science.gov (United States)

    Ilday, Serim; Akguc, Gursoy B.; Tokel, Onur; Makey, Ghaith; Yavuz, Ozgun; Yavuz, Koray; Pavlov, Ihor; Ilday, F. Omer; Gulseren, Oguz

    We report a new dynamical self-assembly mechanism, where judicious use of convective and strong Brownian forces enables effective patterning of colloidal nanoparticles that are almost two orders of magnitude smaller than the laser beam. Optical trapping or tweezing effects are not involved, but the laser is used to create steep thermal gradients through multi-photon absorption, and thereby guide the colloids through convective forces. Convective forces can be thought as a positive feedback mechanism that helps to form and reinforce pattern, while Brownian motion act as a competing negative feedback mechanism to limit the growth of the pattern, as well as to increase the possibilities of bifurcation into different patterns, analogous to the competition observed in reaction-diffusion systems. By steering stochastic processes through these forces, we are able to gain control over the emergent pattern such as to form-deform-reform of a pattern, to change its shape and transport it spatially within seconds. This enables us to dynamically initiate and control large patterns comprised of hundreds of colloids. Further, by not relying on any specific chemical, optical or magnetic interaction, this new method is, in principle, completely independent of the material type being assembled.

  17. Controlling two plasmon decay instability in intense femtosecond laser driven plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Prashant Kumar; Adak, Amitava; Lad, Amit D.; Chatterjee, Gourab; Ravindra Kumar, G., E-mail: grk@tifr.res.in [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400005 (India); Brijesh, P. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400005 (India); UM-DAE Centre for Excellence in Basic Sciences, Mumbai 400098 (India)

    2015-11-15

    We investigate the onset of the two-plasmon-decay (TPD) instability in intense femtosecond laser-solid interaction. In particular, this instability, originating at the quarter critical electron density surface in the inhomogeneous plasma, is explored for a wide range of laser parameters-energy, pulse duration, and intensity contrast. By varying these laser parameters, we demonstrate ways to excite and control the growth of the TPD process. The pulse duration scan carried out under a constant laser fluence reveals the pulse width dependent nature of TPD growth. The spectral splitting of the TPD induced three-halves harmonic emission is used to infer the electron temperature near the quarter critical density surface. Moreover, by varying the laser contrast over four orders of magnitude, we find that the intensity threshold of three-halves harmonic emission increases by nearly two orders of magnitude. This contrast dependent intensity threshold for the emission of three-halves harmonic can be a useful diagnostic of the laser contrast.

  18. 3D mapping of chemical distribution from melting at lower mantle conditions in the laser-heated diamond anvil cell

    Science.gov (United States)

    Dorfman, S. M.; Nabiei, F.; Cantoni, M.; Badro, J.; Gaal, R.; Gillet, P.

    2014-12-01

    The laser-heated diamond anvil cell is a unique tool for subjecting materials to pressures over few hundreds of GPa and temperatures of thousands of Kelvins which enables us to experimentally simulate the inaccessible interiors of planets. However, small sample size, laser profile and thermally conductive diamonds cause temperature gradients of 1000s K over a few microns which also affects chemical and structural distribution of phases in the sample. We have examined samples of San Carlos olivine (Mg,Fe)2SiO3 powder melted in the diamond anvil cell by double-sided and single-sided laser heating for 3-6 minutes to ~3000 K at 35-37 GPa. Moreover, MgO is used as an insulating media in one of the sample. Recovered samples were analyzed by a combination of focused ion beam (FIB) and scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) detector. Images and chemical maps were acquired for ~300 slices with ~70 nm depth from each sample, comprising about half of the heated zone. Detailed chemical and structural analysis by transmission electron microscopy (TEM) of lamellas prepared from the remaining section of the samples will also be presented. In all samples the heated zone included (Mg,Fe)SiO3 perovskite-structured bridgmanite (PV) phase and two (Mg, Fe)O phases, one of which, magnesiowüstite (MW), is richer in iron than the other one, ferropericlase (FP). In double-side heated samples we observe a Fe-rich quenched melt core surrounded by MW phase. Our results show that with increasing heating time, Fe migrates to the molten center of the sample. In the single-side heated sample, the Fe-rich MW phase is concentrated in the center of heated zone. In all samples a FP crust was observed around the heated zone. This crust, however, is broken in the upper part (colder part) of the single-side heated sample due the high asymmetrical temperature gradient within the sample. The results confirm the importance of double-side heating and insulating media

  19. Development of Chemical Process Design and Control for Sustainability

    Science.gov (United States)

    This contribution describes a novel process systems engineering framework that couples advanced control with sustainability evaluation and decision making for the optimization of process operations to minimize environmental impacts associated with products, materials, and energy....

  20. Controlled modification of the structure of polymer surfaces by chemically grafting inorganic species

    Directory of Open Access Journals (Sweden)

    Rodrigo Lambert Oréfice

    1999-07-01

    Full Text Available Many chemical and physical methods, such as plasma, e-beam, sputtering, CVD and others, have been used to modify the structure of polymer surfaces by depositing thin inorganic films. Most of these techniques are based upon the use of high energy sources that ultimately can damage either chemically or physically polymer surfaces. Moreover, these methods are usually not versatile enough to allow the design of structurally and chemically tailored surfaces through the control of the distribution of chemical functionalities throughout the surface. In this work, inorganic species were introduced onto polymer substrates in a controlled manner by performing a sequence of chemical reactions at the surface. Sulfonation followed by silanization reactions were used to graft alkoxysilane species at the surface of poly(aryl sulfones. The heterogeneous chemical modification of poly(aryl sulfones was monitored by FTIR-ATR (Attenuated Total Reflection - FTIR. Model compounds were used to study the chemical reactions occurring during the grafting procedure. The results showed that the developed procedure can allow a controlled introduction of inorganic species onto polymer surfaces. Furthermore, in order to prove that this procedure enables the deposition of specific chemical functionalities onto polymer surfaces that can be used to create chemically and structurally tailored surfaces, silicate films were deposited on previously silanated PAS bioactive glass composites. In vitro tests showed that the surface modified composite can enhance the rates of hydroxy-carbonate-apatite precipitation.

  1. Cooling molecular vibrations with shaped laser pulses: Optimal control theory exploiting the timescale separation between coherent excitation and spontaneous emission

    CERN Document Server

    Reich, Daniel M

    2013-01-01

    Laser cooling of molecules employing broadband optical pumping involves a timescale separation between laser excitation and spontaneous emission. Here, we optimize the optical pumping step using shaped laser pulses. We derive two optimization functionals to drive population into those excited state levels that have the largest spontaneous emission rates to the target state. We show that, when using optimal control, laser cooling of molecules works even if the Franck-Condon map governing the transitions is preferential to heating rather than cooling. Our optimization functional is also applicable to the laser cooling of other degrees of freedom provided the cooling cycle consists of coherent excitation and dissipative deexcitation steps whose timescales are separated.

  2. Techniques to control and position laser targets. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Jones, T.B.

    1978-06-01

    The purpose of the work was to investigate the potential role of various electrohydrodynamic phenomena in the fabrication of small spherical particles and shells for laser target applications. A number of topics were considered. These included charged droplet levitation, specifically the combined effects of the Rayleigh limit and droplet elongation in the presence of electric fields. Two new levitation schemes for uncharged dielectric particles were studied. A dynamic dielectrophoretic levitation scheme was proposed and unsuccessful attempts were made to observe levitation with it. Another static dielectrophoretic levitation scheme was studied and used extensively. A theory was developed for this type of levitation, and a dielectric constant measurement scheme proposed. A charged droplet generator for the production of single droplets (< 1 mm dia of insulating liquids was developed. The synchronous DEP pumping of bubbles and spheres has been considered. Finally, some preliminary experiments with SiH/sub 4//O/sub 2/ bubbles in Viscasil silicone fluid were conducted to learn about the possibility of using silane to form SiO/sub 2/ microballons from bubbles.

  3. High accuracy jog CD control on OPC pattern by advanced laser writer Sigma7500

    Science.gov (United States)

    Chin, Tomas; Wu, Wen-Bin; Shih, Chiang-Lin

    2008-10-01

    With the progress of mask writer technology, 50 KV electron beam writers always perform with better pattern fidelity and critical dimension (CD) control than traditional laser raster-scan writers because laser spot size is confined by the laser longer wavelength relative to electron beam. As far as Optical Proximity Correction (OPC) pattern fidelity is concerned, critical masks with OPC process have to choose Variable-Shape-Beam (VSB) electron beam writer presently. However, the over-aggressive OPC fragmentation induces data volume abrupt explosion, longer writing time, higher mask cost and even mask quality degradation 1. Micronic Sigma7500 laser writer introduces a novel imaging system combining partial coherent light and DUV spatial light modulation (SLM) to generate a high-quality pattern image 2. The benefit of raster-scan laser writer is high throughput with consistent writing time regardless of pattern geometry, complexity and data size. However, pattern CD accuracy still needs improvement. This study is to evaluate jog CD control capability of Sigma7500 on OPC typical line-and-space test patterns with different orientations of 0°, 90°, 45° and 135°. In addition, mask CD uniformity and OPC jog height linearity will also be demonstrated.

  4. Liver repair and hemorrhage control using laser soldering of liquid albumin in a porcine model

    Science.gov (United States)

    Wadia, Yasmin; Xie, Hua; Kajitani, Michio; Gregory, Kenton W.; Prahl, Scott A.

    2000-05-01

    The purpose of this study was to evaluate laser soldering using liquid albumin for welding liver lacerations and sealing raw surfaces created by segmental resection of a lobe. Major liver trauma has a high mortality due to immediate exsanguination and a delayed morbidity and mortality from septicemia, peritonitis, biliary fistulae and delayed secondary hemorrhage. Eight laceration injuries (6 cm long X 2 cm deep) and eight non-anatomical resection injuries (raw surface 6 cm X 2 cm) were repaired. An 805 nm laser was used to weld 53% liquid albumin-ICG solder to the liver surface, reinforcing it with a free autologous omental scaffold. The animals were heparinized to simulate coagulation failure and hepatic inflow occlusion was used for vascular control. For both laceration and resection injuries, eight soldering repairs each were evaluated at three hours. A single suture repair of each type was evaluated at three hours. All 16 laser mediated liver repairs were accompanied by minimal blood loss as compared to the suture controls. No dehiscence, hemorrhage or bile leakage was seen in any of the laser repairs after three hours. In conclusion laser fusion repair of the liver is a quick and reliable technique to gain hemostasis on the cut surface as well as weld lacerations.

  5. Development of Chemical Process Design and Control for Sustainability

    Directory of Open Access Journals (Sweden)

    Shuyun Li

    2016-07-01

    Full Text Available This contribution describes a novel process systems engineering framework that couples advanced control with sustainability evaluation for the optimization of process operations to minimize environmental impacts associated with products, materials and energy. The implemented control strategy combines a biologically-inspired method with optimal control concepts for finding more sustainable operating trajectories. The sustainability assessment of process operating points is carried out by using the U.S. EPA’s Gauging Reaction Effectiveness for the ENvironmental Sustainability of Chemistries with a multi-Objective Process Evaluator (GREENSCOPE tool that provides scores for the selected indicators in the economic, material efficiency, environmental and energy areas. The indicator scores describe process performance on a sustainability measurement scale, effectively determining which operating point is more sustainable if there are more than several steady states for one specific product manufacturing. Through comparisons between a representative benchmark and the optimal steady states obtained through the implementation of the proposed controller, a systematic decision can be made in terms of whether the implementation of the controller is moving the process towards a more sustainable operation. The effectiveness of the proposed framework is illustrated through a case study of a continuous fermentation process for fuel production, whose material and energy time variation models are characterized by multiple steady states and oscillatory conditions.

  6. Automatic quality control in the production of ceramic substrates by pulsed laser cutting

    DEFF Research Database (Denmark)

    Morace, Renate Erica; Hansen, Hans Nørgaard; De Chiffre, Leonardo

    2004-01-01

    This paper deals with the use of optical coordinate measuring machines (CMMs) in the quality control of ceramic substrates produced by a CO2 pulsed laser. A procedure of automatic measurements on a CMM equipped with a CCD camera was developed. In particular, the number and the distribution...

  7. Spectroscopic closed loop control of penetration depth in laser beam welding process

    NARCIS (Netherlands)

    Sibillano, T.; Ancona, A.; Rizzi, D.; Mezzapesa, F.; Konuk, A.R.; Aarts, R.G.K.M.; Huis in 't Veld, A.J.; Lugara, P.M.

    2012-01-01

    In-process monitoring and feedback control are fundamental actions for stable and good quality laser welding process. In particular, penetration depth is one of the most critical features to be monitored. In this research, overlap welding of stainless steel is investigated to stably reproduce a fixe

  8. Real-time seam tracking for robotic laser welding using trajectory-based control

    NARCIS (Netherlands)

    Graaf, de Menno; Aarts, Ronald; Jonker, Ben; Meijer, Johan

    2010-01-01

    In this paper a real-time seam tracking algorithm is proposed that can cope with the accuracy demands of robotic laser welding. A trajectory-based control architecture is presented, which had to be developed for this seam tracking algorithm. Cartesian locations (position and orientation) are added t

  9. Laser-pulse-shape control of photofragmentation in the weak-field limit

    DEFF Research Database (Denmark)

    Tiwari, Ashwani Kumar; Dey, Diptesh; Henriksen, Niels Engholm

    2014-01-01

    We demonstrate theoretically that laser-induced coherent quantum interference control of asymptotic states of dissociating molecules is possible even in the (one-photon) weak-field limit starting from a single vibrational eigenstate. Thus, phase dependence in the interaction with a fixed energy...

  10. Broadband field-resolved terahertz detection via laser induced air plasma with controlled optical bias.

    Science.gov (United States)

    Li, Chia-Yeh; Seletskiy, Denis V; Yang, Zhou; Sheik-Bahae, Mansoor

    2015-05-04

    We report a robust method of coherent detection of broadband THz pulses using terahertz induced second-harmonic (TISH) generation in a laser induced air plasma together with a controlled second harmonic optical bias. We discuss a role of the bias field and its phase in the process of coherent detection. Phase-matching considerations subject to plasma dispersion are also examined.

  11. Coherent Control of Photofragment Distributions Using Laser Phase Modulation in the Weak-Field Limit

    DEFF Research Database (Denmark)

    Garcia-Vela, Alberto; Henriksen, Niels Engholm

    2015-01-01

    The possibility of quantum interference control of the final state distributions of photodissociation fragments by means of pure phase modulation of the pump laser pulse in the weak-field regime is demonstrated theoretically for the first time. The specific application involves realistic wave pac...

  12. Methodological demonstration of laser beam pointing control for space gravitational wave detection missions.

    Science.gov (United States)

    Dong, Yu-Hui; Liu, He-Shan; Luo, Zi-Ren; Li, Yu-Qiong; Jin, Gang

    2014-07-01

    In space laser interferometer gravitational wave (G.W.) detection missions, the stability of the laser beam pointing direction has to be kept at 10 nrad/√Hz. Otherwise, the beam pointing jitter noise will dominate the noise budget and make the detection of G.W. impossible. Disturbed by the residue non-conservative forces, the fluctuation of the laser beam pointing direction could be a few μrad/√Hz at frequencies from 0.1 mHz to 10 Hz. Therefore, the laser beam pointing control system is an essential requirement for those space G.W. detection missions. An on-ground test of such beam pointing control system is performed, where the Differential Wave-front Sensing technique is used to sense the beams pointing jitter. An active controlled steering mirror is employed to adjust the beam pointing direction to compensate the jitter. The experimental result shows that the pointing control system can be used for very large dynamic range up to 5 μrad. At the interested frequencies of space G.W. detection missions, between 1 mHz and 1 Hz, beam pointing stability of 6 nrad/√Hz is achieved.

  13. CHEMICALS

    CERN Multimedia

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  14. Chemical analysis of pharmaceuticals and explosives in fingermarks using matrix-assisted laser desorption ionization/time-of-flight mass spectrometry.

    Science.gov (United States)

    Kaplan-Sandquist, Kimberly; LeBeau, Marc A; Miller, Mark L

    2014-02-01

    Chemical analysis of latent fingermarks, "touch chemistry," has the potential of providing intelligence or forensically relevant information. Matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI/TOF MS) was used as an analytical platform for obtaining mass spectra and chemical images of target drugs and explosives in fingermark residues following conventional fingerprint development methods and MALDI matrix processing. There were two main purposes of this research: (1) develop effective laboratory methods for detecting drugs and explosives in fingermark residues and (2) determine the feasibility of detecting drugs and explosives after casual contact with pills, powders, and residues. Further, synthetic latent print reference pads were evaluated as mimics of natural fingermark residue to determine if the pads could be used for method development and quality control. The results suggest that artificial amino acid and sebaceous oil residue pads are not suitable to adequately simulate natural fingermark chemistry for MALDI/TOF MS analysis. However, the pads were useful for designing experiments and setting instrumental parameters. Based on the natural fingermark residue experiments, handling whole or broken pills did not transfer sufficient quantities of drugs to allow for definitive detection. Transferring drugs or explosives in the form of powders and residues was successful for preparing analytes for detection after contact with fingers and deposition of fingermark residue. One downfall to handling powders was that the analyte particles were easily spread beyond the original fingermark during development. Analyte particles were confined in the original fingermark when using transfer residues. The MALDI/TOF MS was able to detect procaine, pseudoephedrine, TNT, and RDX from contact residue under laboratory conditions with the integration of conventional fingerprint development methods and MALDI matrix. MALDI/TOF MS is a nondestructive

  15. Solution-based Chemical Strategies to Purposely Control the Microstructure of Functional Materials

    Institute of Scientific and Technical Information of China (English)

    Fei LIU; Congting SUN; Chenglin YAN; Dongfeng XUE

    2008-01-01

    Micro/nanostructured crystals with controlled architectures are desirable for many applications in optics, electronics, biology, medicine, and energy conversions. Low-temperature, aqueous chemical routes have been widely investigated for the synthesis of particles, and arrays of oriented nanorods and nanotubes. In this paper, based on the ideal crystal shapes predicted by the chemical bonding theory, we have developed some potential chemical strategies to tune the microstructure of functional materials, ZnS and Nb2O5 nanotube arrays, MgO wiskers and nestlike spheres, and cubic phase Cu2O microcrystals were synthesized here to elucidate these strategies. We describe their controlled crystallization processes and illustrate the detailed key factors controlling their growth by examining various reaction parameters. Current results demonstrate that our designed chemical strategies for tuning microstructure of functional materials are applicable to several technologically important materials, and therefore may be used as a versatile and effective route to the controllable synthesis of other inorganic functional materials.

  16. Environmental Assessment Marsh Vegetation Rehabilitation Chemical Control of Phragmites at Prime Hook National Wildlife Refuge

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This proposal describes a rehabilitation program for up to 3,000 acres of marsh vegetation. The primary objectives are: 1) to chemically control the dense stands of...

  17. Chemical control of Diabrotica virgifera virgifera LeConte

    NARCIS (Netherlands)

    Rozen, van K.; Ester, A.

    2010-01-01

    The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is one of the most important pest species of maize in several countries of Central and Eastern Europe. This pest insect has invaded from the USA and is mainly controlled by insecticides in the EU. In the U

  18. Phase control of a Zeeman-split He-Ne gas laser by variation of the gaseous discharge voltage.

    Science.gov (United States)

    Shelton, W N; Hunt, R H

    1992-07-20

    Zeeman-split lasers are useful for precise positioning or motion control. In applications that employ such a laser to control closely the position of a moving system, phase noise in the Zeeman frequency is a serious problem. Control of low-frequency phase noise can be obtained through variation of the external magnetic field by way of a solenoid wound around the laser tube. It is the finding in this work that control of the residual higher-frequency noise of a He-Ne laser can be obtained through small variations of the high voltage that is used to effect the gaseous discharge in the laser tube. The application of the present system is to the control of the path difference in a Fourier-transform interferometric spectrometer.

  19. Adrenal metastases: CT-guided and MR-thermometry-controlled laser-induced interstitial thermotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Vogl, Thomas J.; Lehnert, Thomas; Eichler, Katrin; Proschek, Dirk; Floeter, Julius; Mack, Martin G. [Johann Wolfgang Goethe University, Department of Diagnostic and Interventional Radiology, University Hospital of Frankfurt, Frankfurt am Main (Germany)

    2007-08-15

    The aim of the study was to evaluate the feasibility, safety and effectiveness of CT-guided and MR-thermometry-controlled laser-induced interstitial thermotherapy (LITT) in adrenal metastases. Nine patients (seven male, two female; average age 65.0 years; range 58.7-75.0 years) with nine unilateral adrenal metastases (mean diameter 4.3 cm) from primaries comprising colorectal carcinoma (n = 5), renal cell carcinoma (n = 1), oesophageal carcinoma (n = 1), carcinoid (n = 1), and hepatocellular carcinoma (n = 1) underwent CT-guided, MR-thermometry-controlled LITT using a 0.5 T MR unit. LITT was performed with an internally irrigated power laser application system with an Nd:YAG laser. A thermosensitive, fast low-angle shot 2D sequence was used for real-time monitoring. Follow-up studies were performed at 24 h and 3 months and, thereafter, at 6-month intervals (median 14 months). All patients tolerated the procedure well under local anaesthesia. No complications occurred. Average number of laser applicators per tumour: 1.9 (range 1-4); mean applied laser energy 33 kJ (range 15.3-94.6 kJ), mean diameter of the laser-induced coagulation necrosis 4.5 cm (range 2.5-7.5 cm). Complete ablation was achieved in seven lesions, verified by MR imaging; progression was detected in two lesions in the follow-up. The preliminary results suggest that CT-guided, MR-thermometry-controlled LITT is a safe, minimally invasive and promising procedure for treating adrenal metastases. (orig.)

  20. High-performance laser power feedback control system for cold atom physics

    Institute of Scientific and Technical Information of China (English)

    Bo Lu; Thibault Vogt; Xinxing Liu; Xiaoji Zhou; Xuzong Chen

    2011-01-01

    @@ A laser power feedback control system that features fast response,large-scale performance,low noise,and excellent stability is presented.Some essential points used for optimization are described.Primary optical lattice experiments are given as examples to show the performance of this system.With these performance characteristics,the power control system is useful for applications in cold atom physics and precision measurements.%A laser power feedback control system that features fast response, large-scale performance, low noise, and excellent stability is presented. Some essential points used for optimization are described. Primary optical lattice experiments are given as examples to show the performance of this system. With these performance characteristics, the power control system is useful for applications in cold atom physics and precision measurements.

  1. Laser-Shot-Induced Chemical Reactions inside Nanotubes: a TDDFT investigation

    Science.gov (United States)

    Zhang, Hong; Miyamoto, Yoshiyuki; Rubio, Angel

    2011-03-01

    We present the application of the time-dependent density functional theory (TDDFT) on ultrafast laser pulse which induces dynamics in molecules encapsulated by a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond-stretch of an HCl molecule inside both C and BN nanotubes. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different. We also observed a radial motion of the nanotube and vacancies appear on the tube wall when the HCl is perpendicular to tube axis. Furthermore, the disintegration of HCl molecules took place when their molecular axis tilted to tube axis. These simulations are important to analyze light-induced nanochemistry and manipulation of nanostructures encapsulated in organic and inorganic nanotubes. The computational scheme used in present work was a combination of the molecular dynamics and real-time propagation of electron wave functions under presence of strong optical field [2,3]. The energy conservation rule was checked to monitor the numerical stability.

  2. UV laser with an acousto-optic intra-cavity control for GaN-sapphire cut

    Science.gov (United States)

    Gradoboev, Yury G.; Kazaryan, Mishik A.; Mokrushin, Yury M.; Shakin, Oleg V.

    2012-09-01

    A copper vapor laser is proposed as the basic component of the installation for processing of sapphire substrates with a GaN-coating. Laser radiation is transformed to UV range by optical frequency doubling. Powerful UV lasers are prospective tools for crystal cutting, photolithography and recording of the fiber Bragg gratings. The proposed approach is more promising in comparison with the use of excimer radiation because of instabilities of excimer laser generation and low coherence of its radiation, which makes difficult precise focusing and using interference pattern of UV radiation for exposing materials. UV laser based on second harmonic radiation of copper vapors laser has been designed. The UV laser system of high operation stability has been developed with output power 1 W at wavelengths 255.5 nm, 271.1 nm, 289.1 nm and coherence length radiation about 4 cm. The original intra-cavity acousto-optic control of output radiation is developed. It is allows adjusting frequency and on-off time ratio of output laser pulses with high accuracy. The stable heat regime was achieved for an active element of copper vapor laser̤ The laser system allows to select an optimum mode of ultra-violet radiation exposition for production of different optical elements. Intra-cavity acousto-optic cell was used for controlling of single pulse amplitude and number of pulses without any power supply tuning providing the stable operation of the laser system.

  3. Coherent beam combination of adaptive fiber laser array with tilt-tip and phase-locking control

    Institute of Scientific and Technical Information of China (English)

    Wang Xiong; Wang Xiao-Lin; Zhou Pu; Su Rong-Tao; Geng Chao; Li Xin-Yang; Xu Xiao-Jun

    2013-01-01

    We present an experimental study on tilt-tip (TT) and phase-locking (PL) control in a coherent beam combination (CBC) system of adaptive fiber laser array.The TT control is performed using the adaptive fiber-optics collimator (AFOC),and the PL control is realized by the phase modulator (PM).Cascaded and simultaneous controls of TT and PL using stochastic parallel gradient descent (SPGD) algorithm are investigated in this paper.Two-fiber-laser-,four-fiber-laser-,and six-fiber-laser-arrays are employed to study the TT and PL control.In the cascaded control system,only one high-speed CMOS camera is used to collect beam data and a computer is used as the controller.In a simultaneous control system one high-speed CMOS camera and one photonic detector (PD) are employed,and a computer and a control circuit based on field programmable gate array (FPGA) are used as the controllers.Experimental results reveal that both cascaded and simultaneous controls of TT using AFOC and PL using PM in fiber laser array are feasible and effective.Cascaded control is more effective in static control situation and simultaneous control can be applied to the dynamic control system directly.The control signals of simultaneous PL and TT disturb each other obviously and TT and PL control may compete with each other,so the control effect is limited.

  4. Acute toxicity of fire-control chemicals, nitrogenous chemicals, and surfactants to rainbow trout

    Science.gov (United States)

    Buhl, Kevin J.; Hamilton, Steven J.

    2000-01-01

    Laboratory studies were conducted to determine the acute toxicity of three ammonia-based fire retardants (Fire-Trol LCA-F, Fire-Trol LCM-R, and Phos-Chek 259F), five surfactant-based fire-suppressant foams (FireFoam 103B, FireFoam 104, Fire Quench, ForExpan S, and Pyrocap B-136), three nitrogenous chemicals (ammonia, nitrate, and nitrite), and two anionic surfactants (linear alkylbenzene sulfonate [LAS] and sodium dodecyl sulfate [SDS]) to juvenile rainbow trout Oncorhynchus mykiss in soft water. The descending rank order of toxicity (96-h concentration lethal to 50% of test organisms [96-h LC50]) for the fire retardants was as follows: Phos-Chek 259F (168 mg/L) > Fire-Trol LCA-F (942 mg/L) = Fire-Trol LCM-R (1,141 mg/L). The descending rank order of toxicity for the foams was as follows: FireFoam 103B (12.2 mg/L) = FireFoam 104 (13.0 mg/L) > ForExpan S (21.8 mg/L) > Fire Quench (39.0 mg/L) > Pyrocap B-136 [156 mg/L). Except for Pyrocap B-136, the foams were more toxic than the fire retardants. Un-ionized ammonia (NH3; 0.125 mg/L as N) was about six times more toxic than nitrite (0.79 mg/L NO2-N) and about 13,300 times more toxic than nitrate (1,658 mg/L NO3-N). Linear alkylbenzene sulfonate (5.0 mg/L) was about five times more toxic than SDS (24.9 mg/L). Estimated total ammonia and NH3 concentrations at the 96-h LC50s of the fire retardants indicated that ammonia was the primary toxic component in these formulations. Based on estimated anionic surfactant concentrations at the 96-h LC50s of the foams and reference surfactants, LAS was intermediate in toxicity and SDS was less toxic to rainbow trout when compared with the foams. Comparisons of recommended application concentrations to the test results indicate that accidental inputs of these chemicals into streams require substantial dilutions (100-1,750-fold to reach concentrations nonlethal to rainbow trout.

  5. Phase-controlled entanglement in a quantum-beat laser: application to quantum lithography

    Science.gov (United States)

    Sete, Eyob A.; Dorfman, Konstantin E.; Dowling, Jonathan P.

    2011-11-01

    We study entanglement generation and control in a quantum-beat laser coupled to a two-mode squeezed vacuum reservoir. We show that the generated entanglement is robust against cavity losses and environmental decoherence and can be controlled by tuning the phases of the microwave and the squeezed input fields. Moreover, we discuss two-photon correlations, absorption and implementations in quantum optical lithography.

  6. Internally coupled Fabry-Perot interferometer for high precision wavelength control of tunable diode lasers

    Energy Technology Data Exchange (ETDEWEB)

    Reich, M.; Schieder, R.; Clar, H.J.; Winnewisser, G.

    1986-01-01

    An internally coupled confocal Fabry-Perot interferometer (FPI) has been developed for both high precision wavelength calibration and stabilization of tunable diode lasers (TDL). Our FPI is tunable and thermally stable and works over a large wavelength range (0.6--30 ..mu..m)-characteristics that cannot be simultaneously realized with conventional etalons. As part of a versatile wavelength control system the instrument has already considerably improved the quality of our diode laser spectra and will facilitate the use of TDLs in sub-Doppler spectroscopy and as local oscillators in heterodyne radiometers.

  7. Controlling electron localization of H$_2^+$ by intense plasmon-enhanced laser fields

    CERN Document Server

    Yavuz, I; Chacón, A; Altun, Z; Lewenstein, M

    2015-01-01

    We present a theoretical study of the wave packet dynamics of the H$_2^+$ molecular ion in plasmon-enhanced laser fields. Such fields may be produced, for instance, when metallic nano-structures are illuminated by a laser pulse of moderated intensity. Their main property is that they vary in space on nanometer scales. We demonstrate that the spatial inhomogeneous character of these plasmonic fields leads to an enhancement of electron localization, an instrumental phenomenon that controls molecular fragmentation. We suggest that the charge-imbalance induced by the surface-plasmon resonance near the metallic nano-structures is the origin of the increase in the electron localization.

  8. Legal requirements and guidelines for the control of harmful laser generated particles, vapours and gases

    Science.gov (United States)

    Horsey, John

    2015-07-01

    This paper is a review of the Health and Safety laws and guidelines relating to laser generated emissions into the workplace and outside environment with emphasis on the differences between legal requirements and guideline advice. The types and nature of contaminants released by various laser processes (i.e. cutting, coding, engraving, marking etc) are discussed, together with the best methods for controlling them to within legal exposure limits. A brief description of the main extract air filtration techniques, including the principles of particulate removal and the action of activated carbon for gas/vapour/odour filtration, is given.

  9. Particles control in selective laser melting in-situ oxide dispersion strengthened method

    Science.gov (United States)

    Zhou, Xin; An, Zhibin; Shen, Zhijian; Liu, Wei; Yao, Chenguang

    2017-01-01

    Stainless steel selective laser melting (SLM) can be considered as a new possible approach for in-situ formation of oxide dispersion strengthened (ODS) steels because of the dispersion of amorphous oxide nano-particles due to the trace amounts of laser chamber oxygen and in-situ internal oxidation of reactive elements. In this paper it is demonstrated that the particle sizes and distributions can be adjusted by choosing different chamber oxygen level through controlling the quantity of initial reactive cores and the available reactive solutes of each core.

  10. Fuzzy logic based feedback control system for laser beam pointing stabilization.

    Science.gov (United States)

    Singh, Ranjeet; Patel, Kiran; Govindarajan, J; Kumar, Ajai

    2010-09-20

    This paper reports a fuzzy logic based feedback control system for beam pointing stabilization of a high-power nanosecond Nd:YAG laser operating at 30 Hz. This is achieved by generating the correcting signal for each consequent pulse from the error in the pointing position of the previous laser pulse. We have successfully achieved a reduction of beam position fluctuation from ±60 to ±5.0 μrad without the focusing optics and ±0.9 μrad with focusing optics.

  11. Control of lateral divergence in high-power, broad-area photonic crystal lasers

    Science.gov (United States)

    Rong, Jiamin; Xing, Enbo; Wang, Lijie; Shu, Shili; Tian, Sicong; Tong, Cunzhu; Wang, Lijun

    2016-07-01

    One-dimensional photonic bandgap crystal (PBC) lasers have demonstrated ultra-low vertical divergence and record brightness; however, their future development is limited by their lateral beam quality. In this paper, a fishbone microstructure is proposed to control the lateral modes in broad-area PBC lasers. The findings reveal that the introduction of the microstructure improves the full width at half maximum of the lateral far field by 22.2% and increases the output power to a small extent. The detailed measurements show that the lateral beam parameter product decreases by 15.9%.

  12. Control of light polarization using optically spin-injected vertical external cavity surface emitting lasers

    Energy Technology Data Exchange (ETDEWEB)

    Frougier, J., E-mail: julien.frougier@thalesgroup.com; Jaffrès, H.; Deranlot, C.; George, J.-M. [Unité Mixte de Physique CNRS-Thales and Université Paris Sud 11, 1 av. Fresnel, 91767 Palaiseau (France); Baili, G.; Dolfi, D. [Thales Research and Technology, 1 av. Fresnel, 91767 Palaiseau (France); Alouini, M. [Institut de Physique de Rennes, 263 Avenue Général Leclerc, 35042 Rennes (France); Sagnes, I. [Laboratoire de Photonique et de Nanostructures, Route de Nozay, 91460 Marcoussis (France); Garnache, A. [Institut d' électronique du Sud CNRS UMR5214, Université Montpellier 2 Place Eugene Bataillon, 34095 Montpellier (France)

    2013-12-16

    We fabricated and characterized an optically pumped (100)-oriented InGaAs/GaAsP multiple quantum well Vertical External Cavity Surface Emitting Laser (VECSEL). The structure is designed to allow the integration of a Metal-Tunnel-Junction ferromagnetic spin-injector for future electrical injection. We report here the control at room temperature of the electromagnetic field polarization using optical spin injection in the active medium of the VECSEL. The switching between two highly circular polarization states had been demonstrated using an M-shaped extended cavity in multi-modes lasing. This result witnesses an efficient spin-injection in the active medium of the LASER.

  13. Controllable optical delay line using a Brillouin optical fiber ring laser

    Institute of Scientific and Technical Information of China (English)

    Yongkang Dong; Zhiwei Lü; Qiang Li; Wei Gao

    2006-01-01

    A controllable optical delay line using a Brillouin optical fiber ring laser is demonstrated and a large timedelay is obtained by cascading two optical fiber segments. In experiment, a single-mode Brillouin opticalfiber ring laser is used to provide Stokes wave as probe wave. We achieve a maximum tunable time delayof 61 ns using two cascading optical fiber segments, about 1.5 times of the input probe pulse width of 40ns. In the meantime, a considerable pulse broadening is observed, which agrees well with the theoreticalprediction based on linear theory.

  14. Analyzing the Chemical and Spectral Effects of Pulsed Laser Irradiation to Simulate Space Weathering of a Carbonaceous Chondrite

    Science.gov (United States)

    Thompson, M. S.; Keller, L. P.; Christoffersen, R.; Loeffler, M. J.; Morris, R. V.; Graff, T. G.; Rahman, Z.

    2017-01-01

    Space weathering processes alter the chemical composition, microstructure, and spectral characteristics of material on the surfaces of airless bodies. The mechanisms driving space weathering include solar wind irradiation and the melting, vaporization and recondensation effects associated with micrometeorite impacts e.g., [1]. While much work has been done to understand space weathering of lunar and ordinary chondritic materials, the effects of these processes on hydrated carbonaceous chondrites is poorly understood. Analysis of space weathering of carbonaceous materials will be critical for understanding the nature of samples returned by upcoming missions targeting primitive, organic-rich bodies (e.g., OSIRIS-REx and Hayabusa 2). Recent experiments have shown the spectral properties of carbonaceous materials and associated minerals are altered by simulated weathering events e.g., [2-5]. However, the resulting type of alteration i.e., reddening vs. bluing of the reflectance spectrum, is not consistent across all experiments [2-5]. In addition, the microstructural and crystal chemical effects of many of these experiments have not been well characterized, making it difficult to attribute spectral changes to specific mineralogical or chemical changes in the samples. Here we report results of a pulsed laser irradiation experiment on a chip of the Murchison CM2 carbonaceous chondrite to simulate micrometeorite impact processing.

  15. Light Controlled Modulation of Gene Expression by Chemical Optoepigenetic Probes

    Science.gov (United States)

    Reis, Surya A.; Ghosh, Balaram; Hendricks, J. Adam; Szantai-Kis, D. Miklos; Törk, Lisa; Ross, Kenneth N.; Lamb, Justin; Read-Button, Willis; Zheng, Baixue; Wang, Hongtao; Salthouse, Christopher; Haggarty, Stephen J.; Mazitschek, Ralph

    2016-01-01

    Epigenetic gene regulation is a dynamic process orchestrated by chromatin-modifying enzymes. Many of these master regulators exert their function through covalent modification of DNA and histone proteins. Aberrant epigenetic processes have been implicated in the pathophysiology of multiple human diseases. Small-molecule inhibitors have been essential to advancing our understanding of the underlying molecular mechanisms of epigenetic processes. However, the resolution offered by small molecules is often insufficient to manipulate epigenetic processes with high spatio-temporal control. Here, we present a novel and generalizable approach, referred to as ‘Chemo-Optical Modulation of Epigenetically-regulated Transcription’ (COMET), enabling high-resolution, optical control of epigenetic mechanisms based on photochromic inhibitors of human histone deacetylases using visible light. COMET probes may translate into novel therapeutic strategies for diseases where conditional and selective epigenome modulation is required. PMID:26974814

  16. Efficiency and cost of chemical control of alternaria brown spot

    OpenAIRE

    Adimara Bentivoglio Colturato; Tatiana Paulossi; Wilson Story Venâncio; Edson Luiz Furtado

    2009-01-01

    A mancha de alternaria, causada por Alternaria alternata f. sp. citri, afeta tangelos Minneola, tangerinas Dancy, tangores Murcote e, menos freqüentemente, tangelos Orlando, tangerinas Novas, Lees e Sunburst. Esta doença causa desfolha grave, queda de frutos e manchas nas frutas. O objetivo deste trabalho foi estabelecer o melhor fungicida e a melhor dose para o controle da mancha marrom de alternaria. O delineamento experimental foi de parcelas subdivididas em blocos, com 10 tratamentos prin...

  17. Adaptive-feedback spectral-phase control for interactions with transform-limited ultrashort high-power laser pulses.

    Science.gov (United States)

    Liu, Cheng; Zhang, Jun; Chen, Shouyuan; Golovin, Gregory; Banerjee, Sudeep; Zhao, Baozhen; Powers, Nathan; Ghebregziabher, Isaac; Umstadter, Donald

    2014-01-01

    Fourier-transform-limited light pulses were obtained at the laser-plasma interaction point of a 100-TW peak-power laser in vacuum. The spectral-phase distortion induced by the dispersion mismatching between the stretcher, compressor, and dispersive materials was fully compensated for by means of an adaptive closed-loop. The coherent temporal contrast on the sub-picosecond time scale was two orders of magnitude higher than that without adaptive control. This novel phase control capability enabled the experimental study of the dependence of laser wakefield acceleration on the spectral phase of intense laser light.

  18. Laser pulse trains for controlling excited state dynamics of adenine in water.

    Science.gov (United States)

    Petersen, Jens; Wohlgemuth, Matthias; Sellner, Bernhard; Bonačić-Koutecký, Vlasta; Lischka, Hans; Mitrić, Roland

    2012-04-14

    We investigate theoretically the control of the ultrafast excited state dynamics of adenine in water by laser pulse trains, with the aim to extend the excited state lifetime and to suppress nonradiative relaxation processes. For this purpose, we introduce the combination of our field-induced surface hopping method (FISH) with the quantum mechanical-molecular mechanical (QM/MM) technique for simulating the laser-driven dynamics in the condensed phase under explicit inclusion of the solvent environment. Moreover, we employ parametric pulse shaping in the frequency domain in order to design simplified laser pulse trains allowing to establish a direct link between the pulse parameters and the controlled dynamics. We construct pulse trains which achieve a high excitation efficiency and at the same time keep a high excited state population for a significantly extended time period compared to the uncontrolled dynamics. The control mechanism involves a sequential cycling of the population between the lowest and higher excited states, thereby utilizing the properties of the corresponding potential energy surfaces to avoid conical intersections and thus to suppress the nonradiative decay to the ground state. Our findings provide a means to increase the fluorescence yield of molecules with an intrinsically very short excited state lifetime, which can lead to novel applications of shaped laser fields in the context of biosensing.

  19. Intense laser-driven ion beams in the relativistic-transparency regime: acceleration, control and applications

    Science.gov (United States)

    Fernandez, Juan C.

    2016-10-01

    Laser-plasma interactions in the novel regime of relativistically-induced transparency have been harnessed to generate efficiently intense ion beams with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at ``table-top'' scales. We have discovered and utilized a self-organizing scheme that exploits persisting self-generated plasma electric ( 0.1 TV/m) and magnetic ( 104 Tesla) fields to reduce the ion-energy (Ei) spread after the laser exits the plasma, thus separating acceleration from spread reduction. In this way we routinely generate aluminum and carbon beams with narrow spectral peaks at Ei up to 310 MeV and 220 MeV, respectively, with high efficiency ( 5%). The experimental demonstration has been done at the LANL Trident laser with 0.12 PW, high-contrast, 0.65 ps Gaussian laser pulses irradiating planar foils up to 250 nm thick. In this regime, Ei scales empirically with laser intensity (I) as I 1 / 2. Our progress is enabled by high-fidelity, massive computer simulations of the experiments. This work advances next-generation compact accelerators suitable for new applications. E . g ., a carbon beam with Ei 400 MeV and 10% energy spread is suitable for fast ignition (FI) of compressed DT. The observed scaling suggests that is feasible with existing target fabrication and PW-laser technologies, using a sub-ps laser pulse with I 2.5 ×1021 W/cm2. These beams have been used on Trident to generate warm-dense matter at solid-densities, enabling us to investigate its equation of state and mixing of heterogeneous interfaces purely by plasma effects distinct from hydrodynamics. They also drive an intense neutron-beam source with great promise for important applications such as active interrogation of shielded nuclear materials. Considerations on controlling ion-beam divergence for their increased utility are discussed. Funded by the LANL LDRD program.

  20. Fractional Nonablative 1540 nm Laser Resurfacing for Thermal Burn Scars: A Randomized Controlled Trial

    DEFF Research Database (Denmark)

    Haedersdal, M.; Moreau, K.E.R.; Beyer, D.M.

    2009-01-01

    fractional laser treatments and (ii) no treatment. Blinded on-site response evaluations were performed 4 and 12 weeks after final treatment. Primary endpoints were change in skin texture (0-10 categorical scale), pain and adverse effects. Secondary endpoints were change in skin color and patient satisfaction......Background and Objective: Burn scars cause permanent and disfiguring problems for many patients and limited treatments are available. Nonablative fractional lasers induce a wound healing response, which may lead to remodeling of burn sear texture. This randomized trial evaluates efficacy...... and adverse effects of 1540 nm fractional laser versus untreated control for burn scars. Materials and Methods: Seventeen adult patients with burn scars of 1 year or older and Fitzpatrick skin types I-III were included in the study. Side-by-side test areas were randomized to (i) three monthly 1540 nm...

  1. Production of Transverse Controllable Laser Density Distribution in Fermilab/NICADD Photoinjector

    CERN Document Server

    Li, Jianliang; Tikhoplav, Rodion

    2005-01-01

    The Fermilab/NICADD photoinjector laboratory consist of a photoemission electron source based on an L band rf-gun. The CsTe photocathode is illuminated by an ultrashort UV laser. The transport line from the laser to the photocathode was recently upgraded to allow imaging of an object plane located ~20 m from the photocathode. This upgrade allows the generation of transverse laser distributions with controlled nonuniformity, yielding the production of an electron beam with various transverse densities patterns. Measuring the evolution of the artificial pattern on the electron bunch provides information that can be used to benchmark numerical simulations and investigate the impact of space charge. Preliminary data on these investigations are presented in the present paper.

  2. Laser Control of Self-Organization Process in Microscopic Region and Fabrication of Fine Microporous Structure

    Directory of Open Access Journals (Sweden)

    Yukimasa Matsumura

    2012-01-01

    Full Text Available We present a controlling technique of microporous structure by laser irradiation during self-organization process. Self-organization process is fabrication method of microstructure. Polymer solution was dropped on the substrate at high humid condition. Water in air appears dropping air temperature below the dew point. The honeycomb structure with regularly aligned pores on the film was fabricated by attaching water droplets onto the solution surface. We demonstrate that it was possible to prevent forming pores at the region of laser irradiation and flat surface was fabricated. We also demonstrated that a combination structure with two pore sizes and flat surface was produced by a single laser-pulse irradiation. Our method is a unique microfabrication processing technique that combines the advantages of bottom-up and top-down techniques. This method is a promising technique that can be applied to produce for photonic crystals, biological cell culturing, surface science and electronics fields, and so forth.

  3. Laser control of complete vibrational transfer in Na$_2$ using resonance coalescence

    CERN Document Server

    Atabek, Osman; Lepers, M; Jaouadi, Amine; Dulieu, Olivier; Kokoouline, V

    2010-01-01

    With a specific choice of laser parameters resulting into a so-called exceptional point in the wavelength-intensity plane, it is possible to produce the coalescence of two Floquet resonances describing the photodissociation of the molecule Na$_2$, which is one of the candidates for molecular cooling. Appropriately tuning laser parameters, following a contour around the exceptional point, the resonances exchange their labels. This represents a laser control of the vibrational transfer from one field-free state to another, through an adiabatic transport involving these resonances. The proportion of undissociated molecules at the end of the pulse is checked through Floquet adiabatic theory. A vibrational cooling scenario can be proposed based on a complete vibrational transfer which is predicted, with only 20 percent of molecules undergoing dissociation.

  4. Chaos synchronization based on a continuous chaos control method in semiconductor lasers with optical feedback.

    Science.gov (United States)

    Murakami, A; Ohtsubo, J

    2001-06-01

    Chaos synchronization using a continuous chaos control method was studied in two identical chaotic laser systems consisting of semiconductor lasers and optical feedback from an external mirror. Numerical calculations for rate equations indicate that the stability of chaos synchronization depends significantly on the external mirror position. We performed a linear stability analysis for the rate equations. Our results show that the stability of the synchronization is much influenced by the mode interaction between the relaxation oscillation frequency of the semiconductor laser and the external cavity frequency. Due to this interaction, an intensive mode competition between the two frequencies destroys the synchronization, but stable synchronization can be achieved when the mode competition is very weak.

  5. Laser-induced thermotherapy of benign and malignant tumors controlled by color-coded duplex sonography

    Science.gov (United States)

    Philipp, Carsten M.; Rohde, Ewa; Waldschmidt, Juergen; Berlien, Hans-Peter

    1994-12-01

    Since 1984 we use the interstitial application of laser induced thermotherapy (LITT) for the treatment of congenital vascular disorders (CVD) such as hemangiomas and vascular malformations. In most of the procedures a 600 micron core bare fiber is used to deliver the radiation of a cw Nd:YAG laser emitting at 1064 nm into the diseased tissue. As most of the CVD treated this way are located subcutaneously, the localization of the fiber and the interstitial laser coagulation (ILC) is controlled by transillumination and palpitation of the heat expansion of the skin surface, this way a crepitation can also be detected during the ILC. As the ILC in deeper body structures cannot be controlled directly we use color coded duplex sonography (CCDS), both for diagnostic and treatment control. In the procedures where we use the B-scan image for puncture control, a color signal is displayed representing tissue movements. These movements caused by degasification and vapor are those detectable as crepitations when using direct control. The color signal starts, changes, and moves in a reproducible pattern following the heat distribution and the subsequently occurring degasification in the tissue. Also the changes in perfusion are detectable by the means of CCDS. The precise extent of the coagulation is visible in the B-scan several minutes after laser exposure. The clinical experience and an extensive experimental evaluation has proven that CCDS is a valuable real time method to monitor the tissue reaction in ILC-procedures. For two years we have performed ILC-procedures with CCDS control in patients with CVD (n equals 65) successfully. Because of its reliable imaging and the clinical advantages recently we applied this type of ILC-control to the palliative treatment of nonresectable primary and secondary liver tumors (n equals 3) and subcutaneous metastases of mamma carcinoma. (n equals 6).

  6. Sensory quality control of alcoholic beverages using fast chemical sensors

    OpenAIRE

    2010-01-01

    Control de calidad sensorial de bebidas alcohólicas utilizando rápidos sensores químicosEn la presente tesis Doctoral, han sido aplicados dos sensores artificiales para el análisis debebidas alcohólicas: la nariz electrónica basada en la espectrometría de masas (MS) y la lenguaelectrónica basada en la espectroscopía infrarroja con transformada de Fourier (FTIR). Elpropósito fue desarrollar nuevas estrategias para analizar la autenticidad de estos productos,desde un punto de vista sensorial, p...

  7. Chemical and mineralogical analyses of planetary rocks using a laser ablation mass spectrometer for in situ space research

    Science.gov (United States)

    Brigitte Neuland, Maike; Mezger, Klaus; Riedo, Andreas; Tulej, Marek; Wurz, Peter

    2015-04-01

    The context chemical analysis is of considerable importance in space research. High resolution in situ studies of planetary materials can yield important information on surface heterogeneity, basic grain mineralogy and chemical composition of surface and subsurface. In turn, these data are the basis for our understanding of the physical and chemical processes which led to the formation and alteration of planetary material [1] [2]. A highly heterogeneous sample of Allende meteorite, representative for extraterrestrial material, is investigated by LMS, a miniature laser ablation mass spectrometer designed for space research [3]. In the current setup a fs-laser ablation ion source is applied, allowing chemical analysis with lateral resolution of about 10-15 μm and sub-micrometre depth resolution [4]. The reflectron TOF mass analyser is used to measure elemental and isotopic composition of the sampled surface. The LMS instrument supports mass resolution 400 and dynamic range of 108 [5]. In the current studies with the fs-ablation ion source significant improvements in the detection efficiency of several metals e.g., Ni, Co, and non-metals e.g., Si, P, S and O, was achieved comparing to our previous setup [6]. Also the values of sensitivity coefficients for these elements are determined to be close to one, which resulted in the substantial improvements of the quantitative element analysis of the sample. Since the ablation crater depth is expected to be about 1 nm/laser shot also the possible changes of the main element or isotope distribution in depth can be analysed to assess their influence on the mineralogical analysis [7]. Several areas on an Allende sample were investigated and the chemical composition across the surface was determined from the mass spectrometric analysis. Also accurate isotope analysis could be conducted for most of main elements with sufficiently high signal to noise ratio. Correlation of elements was conducted and yielded mineralogical maps

  8. Non-textured laser modification of silica glass surface: Wettability control and flow channel formation

    Science.gov (United States)

    Aono, Yuko; Hirata, Atsushi; Tokura, Hitoshi

    2016-05-01

    Local wettability of silica glass surface is modified by infrared laser irradiation. The silica glass surface exhibits hydrophobic property in the presence of sbnd CF3 or sbnd (CH3)2 terminal functional groups, which are decomposed by thermal treatment, and degree of the decomposition depends on the applied heat. Laser irradiation can control the number of remaining functional groups according to the irradiation conditions; the contact angle of deionized water on the laser modified surfaces range from 100° to 40°. XPS analysis confirms that the variation in wettability corresponds to the number of remaining sbnd CF3 groups. The laser irradiation achieves surface modification without causing any cracks or damages to the surface, as observed by SEM and AFM; moreover, surface transparency to visible light and surface roughness remains unaffected. The proposed method is applied to plane flow channel systems. Dropped water spreads only on the hydrophilic and invisible line modified by the laser irradiation without formation of any grooves. This indicates that the modified line can act as a surface channel. Furthermore, self-transportation of liquid is also demonstrated on a channel with gradually-varied wettability along its length. A water droplet on a hydrophobic side is self-transported to a hydrophilic side due to contact-angle hysteresis force without any actuators or external forces.

  9. Low Intensity laser therapy in patients with burning mouth syndrome: a randomized, placebo-controlled study

    Directory of Open Access Journals (Sweden)

    Norberto Nobuo SUGAYA

    Full Text Available Abstract The aim of this study was to assess the effectiveness of low intensity laser therapy in patients with Burning Mouth Syndrome (BMS. Thirty BMS subjects were randomized into two groups – Laser (LG and Placebo (CG. Seven patients dropped out, leaving 13 patients in LG and 10 patients in CG. Each patient received 4 irradiations (laser or placebo twice a week, for two consecutive weeks (blinded to the type of irradiation received. Infrared laser (AsGaAI irradiations were applied to the affected mucosa in scanning mode, wavelength of 790 nm, output power of 20 mW and fluence of 6 J/cm2. A visual analogue scale (VAS was used to assess the therapeutic effect before and after each irradiation, and at all the control time periods: 7, 14, 30, 60 and 90 days after the last irradiation. One researcher delivered irradiation and another recorded the results. Both researchers were blinded, the first to the results, and the second to the type of radiation applied. The results were categorized according to the percentage of symptom level variation, and showed a statistically better response in LG in only two categories of the control checkpoints (p=0.02; Fisher’s Exact Test. According to the protocol used in this study, low intensity laser therapy is as beneficial to patients with BMS as placebo treatment, indicating a great emotional component of involvement in BMS symptomatology. Nevertheless, there were positive results in some statistical analyses, thus encouraging further research in BMS laser therapy with other irradiation parameters.

  10. Control and analysis software for a laser scanning microdensitometer

    Indian Academy of Sciences (India)

    H R Bundel; C P Navathe; P A Naik; P D Gupta

    2006-02-01

    A PC-based control software and data acquisition system is developed for an existing commercial microdensitometer (Biomed make model No. SL-2D/1D UV/VIS) to facilitate scanning and analysis of X-ray films. The software is developed in Labview, which includes operation of the microdensitometer in 1D and 2D scans and analysis of spatial or spectral data on X-ray films, such as optical density, intensity and wavelength. It provides a user-friendly Graphical User Interface (GUI) to analyse the scanned data and also store the analysed data/image in popular formats like data in Excel and images in jpeg. It has also on-line calibration facility with standard optical density tablets. The control software and data acquisition system is simple, inexpensive and versatile.

  11. Optical properties and chemical behavior of Laser-dye Coumarin-500 and the influence of atmospheric corona discharges.

    Science.gov (United States)

    Keskin, S Sinan; Aslan, Necdet; Bayrakçeken, Fuat

    2009-03-01

    Structure elucidation of Coumarin-500 Laser-dye in cyclohexane at room temperature has been studied by UV-Vis, Raman, and FTIR spectroscopic techniques. Optical properties and chemical behavior under the influence of atmospheric positive electric pulsed corona discharges were also examined. The effects of UV-Vis irradiation changed some optical parameters, such as decrease in optical density on the absorption spectrum and formation of photoproducts, due to the chromaticity removal. No significant optical changes were observed in the light absorption upon UV-irradiation but large changes in absorption spectrum were observed after positive electric corona discharge treatments, FTIR and Raman spectra in non-polar solvent are recorded and interpreted.

  12. Pulse Operation of Chemical Oxygen-Iodine Laser by Pulsed Gas Discharge with the Assistance of Spark Pre-ionization

    Institute of Scientific and Technical Information of China (English)

    LI Guo-Fu; YU Hai-Jun; DUO Li-Ping; JIN Yu-Qi; WANG Jian; SANG Feng-Ting; FANG Ben-Jie; WANG De-Zhen

    2009-01-01

    The continuous wavelength chemical oxygen-iodine laser can be turned into pulse operation mode in order to obtain high energy and high pulse power. We propose an approach to produce iodine atoms instantaneously by pulsed gas discharge with the assistance of spark pre-ionization to achieve the pulsed goal. The influence of spark pre-ionization on discharge homogeneity is discussed. Voltage-current characteristics are shown and discussed in existence of the pre-ionization capacitor and peaking capacitor. The spark pre-ionization and peaking capacitor are very helpful in obtaining a stable and homogeneous discharge. The lasing is achieved at the total pressure of 2.2-2.9 kPa and single pulse energy is up to 180m J, the corresponding specific output energy is 1.0 J/L.

  13. Chemically assisted ion beam etching of laser diode facets on nonpolar and semipolar orientations of GaN

    Science.gov (United States)

    Kuritzky, L. Y.; Becerra, D. L.; Saud Abbas, A.; Nedy, J.; Nakamura, S.; DenBaars, S. P.; Cohen, D. A.

    2016-07-01

    We demonstrate a vertical (beam etching (CAIBE) in Cl2 chemistry that is suitable for forming laser diode (LD) facets on nonpolar and semipolar oriented III-nitride devices. The etch profiles were achieved with photoresist masks and optimized CAIBE chamber conditions including the platen tilt angle and Cl2 flow rate. Co-loaded studies showed similar etch rates of ˜60 nm min-1 for (20\\bar{2}\\bar{1}),(20\\bar{2}1), and m-plane orientations. The etched surfaces of LD facets on these orientations are chemically dissimilar (Ga-rich versus N-rich), but were visually indistinguishable, thus confirming the negligible orientation dependence of the etch. Continuous-wave blue LDs were fabricated on the semipolar (20\\bar{2}\\bar{1}) plane to compare CAIBE and reactive ion etch (RIE) facet processes. The CAIBE process resulted in LDs with lower threshold current densities due to reduced parasitic mirror loss compared with the RIE process. The LER, degree of verticality, and model of the 1D vertical laser mode were used to calculate a maximum uncoated facet reflection of 17% (94% of the nominal) for the CAIBE facet. The results demonstrate the suitability of CAIBE for forming high quality facets for high performance nonpolar and semipolar III-N LDs.

  14. PROCESS CONTROL IN THE EDUCATION OF ORGANIC CHEMICAL TECHNOLOGY

    Directory of Open Access Journals (Sweden)

    lstván Csontos

    2001-06-01

    Full Text Available Las prácticas de laboratorio demuestran la importancia de los modernos procesos de control en las tecnologías de química orgánica. Se necesitaba desarrollar un sistema que une las ventajas de los calorímetros de reacción con las de modelo de los reactores controladas de la industria. El diseño de hardware y de software se permite trasladar el programa desarrollado en el laboratorio para el nivel industrial. El algoritmo general para las reacciones de diazotación y clormetilación es aplicado para el sintésis del cloruro de benzo-diazonio y cloruro de dietoxi-benzil en las prácticas de laboratorio.

  15. Development of a deep-sea laser-induced breakdown spectrometer for in situ multi-element chemical analysis

    Science.gov (United States)

    Thornton, Blair; Takahashi, Tomoko; Sato, Takumi; Sakka, Tetsuo; Tamura, Ayaka; Matsumoto, Ayumu; Nozaki, Tatsuo; Ohki, Toshihiko; Ohki, Koichi

    2015-01-01

    Spectroscopy is emerging as a technique that can expand the envelope of modern oceanographic sensors. The selectivity of spectroscopic techniques enables a single instrument to measure multiple components of the marine environment and can form the basis for versatile tools to perform in situ geochemical analysis. We have developed a deep-sea laser-induced breakdown spectrometer (ChemiCam) and successfully deployed the instrument from a remotely operated vehicle (ROV) to perform in situ multi-element analysis of both seawater and mineral deposits at depths of over 1000 m. The instrument consists of a long-nanosecond duration pulse-laser, a spectrometer and a high-speed camera. Power supply, instrument control and signal telemetry are provided through a ROV tether. The instrument has two modes of operation. In the first mode, the laser is focused directly into seawater and spectroscopic measurements of seawater composition are performed. In the second mode, a fiber-optic cable assembly is used to make spectroscopic measurements of mineral deposits. In this mode the laser is fired through a 4 m long fiber-optic cable and is focused onto the target's surface using an optical head and a linear stage that can be held by a ROV manipulator. In this paper, we describe the instrument and the methods developed to process its measurements. Exemplary measurements of both seawater and mineral deposits made during deployments of the device at an active hydrothermal vent field in the Okinawa trough are presented. Through integration with platforms such as underwater vehicles, drilling systems and subsea observatories, it is hoped that this technology can contribute to more efficient scientific surveys of the deep-sea environment.

  16. Mirror deflection control for a confocal scanning laser microscope employing a time-modulated laser and a linear diode array

    Science.gov (United States)

    Aslund, Nils R.; Patwardhan, Ardan; Trepte, Oliver

    1994-04-01

    A mirror deflection device for a CSLM has been developed. It performs repetitive scanning according to a preset waveform which can be chosen arbitrarily. It can also be used to perform stationary positioning at arbitrarily chosen points. A digital memory, comprising dual banks, is used to allow switching from one actuating waveform to another. The movement of the mirror is recorded very accurately. A burst of sequential pulse from a diode laser is deflected by the mirror and recorded by means of a linear diode array. The target pattern is analyzed digitally. The objective is to implement a control strategy whereby a new actuating waveform can be derived in order to correct any deviation between the desired waveform and the recorded one. Some results obtained with the device are reported. Foreseen applications encompass spectral analysis of selected regions and kinetic studies where a trade-off between speed and number of image points is necessary.

  17. Morphology, thermoelectric properties and wet-chemical doping of laser-sintered germanium nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Stoib, Benedikt; Langmann, Tim; Matich, Sonja; Sachsenhauser, Matthias; Stutzmann, Martin; Brandt, Martin S. [Walter Schottky Institut, Technische Universitaet Muenchen, Am Coulombwall 4, 85748 Garching (Germany); Petermann, Nils; Wiggers, Hartmut [Institut fuer Verbrennung und Gasdynamik and Center for Nanointegration, Universitaet Duisburg-Essen, Lotharstr. 1, 47048 Duisburg (Germany)

    2013-01-15

    Porous, highly doped semiconductors are potential candidates for thermoelectric energy conversion elements. We report on the fabrication of thin films of Ge via short-pulse laser-sintering of Ge nanoparticles (NPs) in vacuum and study the macroporous morphology of the samples by secondary electron microscopy (SEM) imaging. The temperature dependence of the electrical conductivity and the Seebeck coefficient of undoped Ge is discussed in conjunction with the formation of a defect band near the valence band. We further introduce a versatile method of doping the resulting films with a variety of common dopant elements in group-IV semiconductors by using a liquid containing the dopant atoms. This method is fully compatible with laser-direct writing and suited to fabricate small scale thermoelectric generators. The incorporation of the dopants is verified by X-ray photoelectron spectroscopy (XPS) and their electrical activation is studied by conductivity and thermopower measurements. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Optical methods for diagnostics and feedback control in laser-induced regeneration of spine disc and joint cartilages

    Science.gov (United States)

    Sobol, Emil; Sviridov, Alexander; Omeltchenko, Alexander; Baum, Olga; Baskov, Andrey; Borchshenko, Igor; Golubev, Vladimir; Baskov, Vladimir

    2011-03-01

    In 1999 we have introduced a new approach for treatment of spine diseases based on the mechanical effect of nondestructive laser radiation on the nucleus pulposus of the intervertebral disc. Laser reconstruction of spine discs (LRD) involves puncture of the disc and non-destructive laser irradiation of the nucleus pulposus to activate reparative processes in the disc tissues. In vivo animal study has shown that LRD allows activate the growth of hyaline type cartilage in laser affected zone. The paper considers physical processes and mechanisms of laser regeneration, presents results of investigations aimed to optimize laser settings and to develop feedback control system for laser reparation in cartilages of spine and joints. The results of laser reconstruction of intervertebral discs for 510 patients have shown substantial relief of back pain for 90% of patients. Laser technology has been experimentally tested for reparation of traumatic and degenerative diseases in joint cartilage of 20 minipigs. It is shown that laser regeneration of cartilage allows feeling large (more than 5 mm) defects which usually never repair on one's own. Optical techniques have been used to promote safety and efficacy of the laser procedures.

  19. Computer Control of the Spectral Composition of the Powerful Laser System Irradiation with a Wide Range of Laser Transitions on Metal Vapors

    Directory of Open Access Journals (Sweden)

    Soldatov Anatoly

    2016-01-01

    Full Text Available The results of the experimental study cycle of the multiwave metal vapor laser system on the basis of the original configuration of the multimedia laser emitter. The spectral parameters of the setup have been controlled using a personal computer (PC. This allows carrying out their independent optimization according to excitation conditions, and, therefore, promptly allocating the output set of oscillating wavelengths and their relative distribution in power, which makes the system attractive for scientific and technological application.

  20. Direct chemical analysis of frozen ice cores by UV-laser ablation ICPMS

    DEFF Research Database (Denmark)

    Müller, Wolfgang; Shelley, J. Michael G.; Rasmussen, Sune Olander

    2011-01-01

    Cryo-cell UV-LA-ICPMS is a new technique for direct chemical analysis of frozen ice cores at high spatial resolution (ice and reveals sea ice/dust records and annual layer signatures at unprecedented spatial/time resolution. Uniquely......, the location of cation impurities relative to grain boundaries in recrystallized ice can be assessed....

  1. Similarity between the mechanisms of soft-laser radiation and chemical adaptogen action

    Science.gov (United States)

    Reznikov, Leonid L.; Pavlova, Rimma N.; Murzin, Alexander G.; Boiko, Vladimir A.; Pupkova, Ludmila S.; Soms, Leonid N.

    1993-07-01

    The comparative studies of SLR effects vs chemical adaptogens effects on animals poisoned by industrial poisons and SLR as compared to traditional radio-protectors effects on gamma- irradiated animals were carried out. Obtained results show the stressed adaptogenous effect of SLR.

  2. Controlled manufacturing of nanoparticles by the laser pyrolysis: Application to cementite iron carbide

    Science.gov (United States)

    Morjan, I.; Alexandrescu, R.; Scarisoreanu, M.; Fleaca, C.; Dumitrache, F.; Soare, I.; Popovici, E.; Gavrila, L.; Vasile, E.; Ciupina, V.; Popa, N. C.

    2009-09-01

    The laser pyrolysis is an attractive technique for the synthesis of different nanostructures from gas-phase precursors. The characteristics of this synthesized method are here exemplified by the production of almost pure cementite Fe 3C nanomaterials, obtained by the pyrolysis of methyl methacrylate and iron pentacarbonyl (vapors). Those nanopowders exhibited core (Fe 3C)-shell (MMA polymer-based) morphologies and mean particle diameters of about 8-9 nm. Preliminary magnetic measurements indicate rather high values for the saturation magnetization. By irradiating the same reactive mixture with a lower intensity radiation, the chemical content of nanopowders shifts towards mixtures of iron and maghemite/magnetite iron oxides.

  3. Control of combustion and detonation by means of resonance laser radiation: analysis and potentialities

    Science.gov (United States)

    Starik, Alexander M.; Titova, Nataliya S.; Loukhovitski, Boris I.

    2003-07-01

    The theoretical and computational studies based on the novel physical and mathematical model of nonequilibrium chemical processes involving vibrationally and electronically exited molecules have shown that selective excitation of reacting species by laser radiation results in a considerable reduction of self-ignition temperature, decrease of induction and combustion times, and initiates detonation in supersonic flow at relatively low radiation energy inputted into the mixture. These effects are due to production of the novel channels of high reactive radicals formation and enhancement of chain mechanism of combustion and are not associated with the thermal action of absorbed radiation.

  4. Timing control of an intense picosecond pulse laser to the SPring-8 synchrotron radiation pulses

    Science.gov (United States)

    Tanaka, Yoshihito; Hara, Toru; Kitamura, Hideo; Ishikawa, Tetsuya

    2000-03-01

    We have developed a control system to synchronize intense picosecond laser pulses to the hard x-ray synchrotron radiation (SR) pulses of SPring-8. A regeneratively amplified mode-locked Ti:sapphire laser is synchronized to 40 ps SR pulses by locking the laser to the radio frequency of the ring. The synchronization of the pulses is monitored by detecting both beams simultaneously on a gold photocathode of a streak camera. This method enabled us to make a precise measurement of the time interval between the beams, even if the trigger of the streak camera drifts. Synchronization between the laser and the SR pulses has been achieved with a precision of ±2 ps for some hours. The stable timing control ensures the possibility of making two-photon excitation and pump-probe experiments with time resolution of a few tens of ps (limited by the pulse duration of the SR). We have used this system to show that closing undulator gaps in the storage ring shifts the arrival time of the SR pulses, in accord with expectations for the increased power loss.

  5. Carrier Envelope Phase Controlled High-Order Harmonic Generation in Ultrashort Laser Pulse

    Institute of Scientific and Technical Information of China (English)

    WANG Bing-Bing; CHEN Jing; LIU Jie; LI Xiao-Feng; FU Pan-Ming

    2005-01-01

    @@ We investigate the carrier envelope phase (CEP) effects on high-order harmonic generation (HHG) in ultrashort pulses with the pulse duration 2.5fs when the laser intensity is high enough so that the initial state is ionized effectively during the laser pulse but remains about 20% population at the end of the laser pulse. We find that the ionization process of the initial state is very sensitive to the CEP during the laser pulse. The ionization process of the initial state determines the continuum state population and hence influences dramatically the weights of the classical trajectories that contribute to HHG. In such a case we can not predict the cutoff and the structure of the harmonic spectrum only by the number and the kinetic energy of the classical trajectories. The harmonic spectrum exhibits abundant characters for different CEP cases. As a result, we can control the cutoff frequency and the plateau structure of the harmonic spectrum with CEP by controlling the time behaviour of the ionization of the initial state.

  6. Optimization of ultra-fast interactions using laser pulse temporal shaping controlled by a deterministic algorithm

    Science.gov (United States)

    Galvan-Sosa, M.; Portilla, J.; Hernandez-Rueda, J.; Siegel, J.; Moreno, L.; Ruiz de la Cruz, A.; Solis, J.

    2014-02-01

    Femtosecond laser pulse temporal shaping techniques have led to important advances in different research fields like photochemistry, laser physics, non-linear optics, biology, or materials processing. This success is partly related to the use of optimal control algorithms. Due to the high dimensionality of the solution and control spaces, evolutionary algorithms are extensively applied and, among them, genetic ones have reached the status of a standard adaptive strategy. Still, their use is normally accompanied by a reduction of the problem complexity by different modalities of parameterization of the spectral phase. Exploiting Rabitz and co-authors' ideas about the topology of quantum landscapes, in this work we analyze the optimization of two different problems under a deterministic approach, using a multiple one-dimensional search (MODS) algorithm. In the first case we explore the determination of the optimal phase mask required for generating arbitrary temporal pulse shapes and compare the performance of the MODS algorithm to the standard iterative Gerchberg-Saxton algorithm. Based on the good performance achieved, the same method has been applied for optimizing two-photon absorption starting from temporally broadened laser pulses, or from laser pulses temporally and spectrally distorted by non-linear absorption in air, obtaining similarly good results which confirm the validity of the deterministic search approach.

  7. Vibration-Assisted Femtosecond Laser Drilling with Controllable Taper Angles for AMOLED Fine Metal Mask Fabrication

    Directory of Open Access Journals (Sweden)

    Wonsuk Choi

    2017-02-01

    Full Text Available This study investigates the effect of focal plane variation using vibration in a femtosecond laser hole drilling process on Invar alloy fabrication quality for the production of fine metal masks (FMMs. FMMs are used in the red, green, blue (RGB evaporation process in Active Matrix Organic Light-Emitting Diode (AMOLED manufacturing. The taper angle of the hole is adjusted by attaching the objective lens to a micro-vibrator and continuously changing the focal plane position. Eight laser pulses were used to examine how the hole characteristics vary with the first focal plane’s position, where the first pulse is focused at an initial position and the focal planes of subsequent pulses move downward. The results showed that the hole taper angle can be controlled by varying the amplitude of the continuously operating vibrator during femtosecond laser hole machining. The taper angles were changed between 31.8° and 43.9° by adjusting the vibrator amplitude at a frequency of 100 Hz. Femtosecond laser hole drilling with controllable taper angles is expected to be used in the precision micro-machining of various smart devices.

  8. Controlling Properties and Cytotoxicity of Chitosan Nanocapsules by Chemical Grafting

    Directory of Open Access Journals (Sweden)

    Laura De Matteis

    2016-09-01

    Full Text Available The tunability of the properties of chitosan-based carriers opens new ways for the application of drugs with low water-stability or high adverse effects. In this work, the combination of a nanoemulsion with a chitosan hydrogel coating and the following poly (ethylene glycol (PEG grafting is proven to be a promising strategy to obtain a flexible and versatile nanocarrier with an improved stability. Thanks to chitosan amino groups, a new easy and reproducible method to obtain nanocapsule grafting with PEG has been developed in this work, allowing a very good control and tunability of the properties of nanocapsule surface. Two different PEG densities of coverage are studied and the nanocapsule systems obtained are characterized at all steps of the optimization in terms of diameter, Z potential and surface charge (amino group analysis. Results obtained are compatible with a conformation of PEG molecules laying adsorbed on nanoparticle surface after covalent linking through their amino terminal moiety. An improvement in nanocapsule stability in physiological medium is observed with the highest PEG coverage density obtained. Cytotoxicity tests also demonstrate that grafting with PEG is an effective strategy to modulate the cytotoxicity of developed nanocapsules. Such results indicate the suitability of chitosan as protective coating for future studies oriented toward drug delivery.

  9. Controlling Properties and Cytotoxicity of Chitosan Nanocapsules by Chemical Grafting

    Science.gov (United States)

    De Matteis, Laura; Alleva, Maria; Serrano-Sevilla, Inés; García-Embid, Sonia; Stepien, Grazyna; Moros, María; de la Fuente, Jesús M.

    2016-01-01

    The tunability of the properties of chitosan-based carriers opens new ways for the application of drugs with low water-stability or high adverse effects. In this work, the combination of a nanoemulsion with a chitosan hydrogel coating and the following poly (ethylene glycol) (PEG) grafting is proven to be a promising strategy to obtain a flexible and versatile nanocarrier with an improved stability. Thanks to chitosan amino groups, a new easy and reproducible method to obtain nanocapsule grafting with PEG has been developed in this work, allowing a very good control and tunability of the properties of nanocapsule surface. Two different PEG densities of coverage are studied and the nanocapsule systems obtained are characterized at all steps of the optimization in terms of diameter, Z potential and surface charge (amino group analysis). Results obtained are compatible with a conformation of PEG molecules laying adsorbed on nanoparticle surface after covalent linking through their amino terminal moiety. An improvement in nanocapsule stability in physiological medium is observed with the highest PEG coverage density obtained. Cytotoxicity tests also demonstrate that grafting with PEG is an effective strategy to modulate the cytotoxicity of developed nanocapsules. Such results indicate the suitability of chitosan as protective coating for future studies oriented toward drug delivery. PMID:27706041

  10. Chemical atributes of an oxisol submitted to weed control in coffee

    OpenAIRE

    2015-01-01

    In coffee culture, the inadequate control of invasive plants can degrade the soil used then managements practices to contribute to the improvement of quality physical, chemical and biological of the soil. Should be used the aim of this work were evaluated the influence of various weed control methods on some chemical properties of a Red-Yellow Latosol (RYL) cultivated with coffee. The experimental design was randomized block with strip plots, making a 9x2 factorial, nine control methods and t...

  11. Development of Computational Approaches for Simulation and Advanced Controls for Hybrid Combustion-Gasification Chemical Looping

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, Abhinaya; Lou, Xinsheng; Neuschaefer, Carl; Chaudry, Majid; Quinn, Joseph

    2012-07-31

    This document provides the results of the project through September 2009. The Phase I project has recently been extended from September 2009 to March 2011. The project extension will begin work on Chemical Looping (CL) Prototype modeling and advanced control design exploration in preparation for a scale-up phase. The results to date include: successful development of dual loop chemical looping process models and dynamic simulation software tools, development and test of several advanced control concepts and applications for Chemical Looping transport control and investigation of several sensor concepts and establishment of two feasible sensor candidates recommended for further prototype development and controls integration. There are three sections in this summary and conclusions. Section 1 presents the project scope and objectives. Section 2 highlights the detailed accomplishments by project task area. Section 3 provides conclusions to date and recommendations for future work.

  12. Chemical control over the energy-level alignment in a two-terminal junction

    Science.gov (United States)

    Yuan, Li; Franco, Carlos; Crivillers, Núria; Mas-Torrent, Marta; Cao, Liang; Sangeeth, C. S. Suchand; Rovira, Concepció; Veciana, Jaume; Nijhuis, Christian A.

    2016-07-01

    The energy-level alignment of molecular transistors can be controlled by external gating to move molecular orbitals with respect to the Fermi levels of the source and drain electrodes. Two-terminal molecular tunnelling junctions, however, lack a gate electrode and suffer from Fermi-level pinning, making it difficult to control the energy-level alignment of the system. Here we report an enhancement of 2 orders of magnitude of the tunnelling current in a two-terminal junction via chemical molecular orbital control, changing chemically the molecular component between a stable radical and its non-radical form without altering the supramolecular structure of the junction. Our findings demonstrate that the energy-level alignment in self-assembled monolayer-based junctions can be regulated by purely chemical modifications, which seems an attractive alternative to control the electrical properties of two-terminal junctions.

  13. Setup of a beam control system for high power laser system at DLR

    Science.gov (United States)

    Buske, Ivo; Walther, Andreas

    2016-10-01

    Different types of high power or high energy lasers in the multi kW class are currently available or are under development with promising progress reports. A major challenge is to deliver as much as possible of the available power onto a small and fast moving target over a long distance through a disturbing atmosphere. High resolution imaging is a common way to identify the category of targets dedication and to determine the spatial position relative to the observer. By illuminating the target with a laser the imaging system becomes more resilient towards ambient light and the exposure time can be reduced drastically. Fast and deterministic control loops are demanding for the moving parts in order to maintain a high accuracy for the pointing of the turret and aiming of the laser countermeasure system. Here, we report on the progress of such a beam control system developed at the Institute of Technical Physics of DLR. In an overview we present the beam control system and explain different sub-systems. Performance tests were taken at our test. At a distance we simulated various scenarios for probing the limits of the tracking and pointing accuracy with a target on a fast moving linear stage. We present first results of the beam control system performance.

  14. Laser therapy of muscle injuries.

    Science.gov (United States)

    Dawood, Munqith S; Al-Salihi, Anam Rasheed; Qasim, Amenah Wala'a

    2013-05-01

    Low-level lasers are used in general therapy and healing process due to their good photo-bio-stimulation effects. In this paper, the effects of diode laser and Nd:YAG laser on the healing process of practically managed skeletal muscle trauma has been successfully studied. Standard impact trauma was induced by using a specially designed mechanical device. The impacted muscle was left for 3 days for complete development of blunt trauma. After that it was irradiated by five laser sessions for 5 days. Two types of lasers were used; 785-nm diode laser and 1.064-nm Nd:YAG laser, both in continuous and pulsed modes. A special electronic circuit was designed and implemented to modulate the diode laser for this purpose. Tissue samples of crushed skeletal muscle have been dissected from the injured irradiated muscle then bio-chemically analyzed for the regeneration of contractile and collagenous proteins using Lowry assay for protein determination and Reddy and Enwemeka assay for hydroxyproline determination. The results showed that both lasers stimulate the regeneration capability of traumatized skeletal muscle. The diode laser in CW and pulsed modes showed better results than the Nd:YAG in accelerating the preservation of the normal tissue content of collagenous and contractile proteins beside controlling the regeneration of non-functional fibrous tissue. This study proved that the healing achieved by the laser treatment was faster than the control group by 15-20 days.

  15. Low threshold 1.55 {mu}m wavelength InAsP/InGaAsP strained multiquantum well laser diode grown by chemical beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Carlin, J.F.; Syrbu, A.V.; Berseth, C.A.; Behrend, J.; Rudra, A.; Kapon, E. [Institut de Micro- et Optoelectronique, Departement de Physique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

    1997-07-01

    By using chemical beam epitaxy at growth temperatures as low as 460{endash}480{degree}C, we have overcome strain relaxation problems that prevented so far the successful use of InAsP quantum wells in 1.55 {mu}m lasers. Five quantum well InAsP/InGaAsP horizontal cavity lasers showed 88{percent} internal efficiency, 1.6cm{sup {minus}1} losses per well, and 33A/cm{sup 2} transparency current density per well, which equal or even surpass the best published characteristics for 1.55 {mu}m wavelength lasers based on any material system. Moreover, up to 17 quantum wells were integrated in a strain-balanced laser, which showed equally good characteristics. {copyright} {ital 1997 American Institute of Physics.}

  16. Multivariate analysis of laser-induced breakdown spectroscopy chemical signatures for geomaterial classification

    Energy Technology Data Exchange (ETDEWEB)

    Gottfried, Jennifer L., E-mail: jennifer.gottfried@us.army.mi [US Army Research Laboratory, Aberdeen Proving Ground, MD 21005-5069 (United States); Harmon, Russell S. [ARL Army Research Office, PO Box 12211, Research Triangle Park, NC 27709-2211 (United States); De Lucia, Frank C.; Miziolek, Andrzej W. [US Army Research Laboratory, Aberdeen Proving Ground, MD 21005-5069 (United States)

    2009-10-15

    A large suite of natural carbonate, fluorite and silicate geological materials was studied using laser-induced breakdown spectroscopy (LIBS). Both single- and double-pulse LIBS spectra were acquired using close-contact benchtop and standoff (25 m) LIBS systems. Principal components analysis (PCA) and partial least squares discriminant analysis (PLS-DA) were used to identify the distinguishing characteristics of the geological samples and to classify the materials. Excellent discrimination was achieved with all sample types using PLS-DA and several techniques for improving sample classification were identified. The laboratory double-pulse LIBS system did not provide any advantage for sample classification over the single-pulse LIBS system, except in the case of the soil samples. The standoff LIBS system provided comparable results to the laboratory systems. This work also demonstrates how PCA can be used to identify spectral differences between similar sample types based on minor impurities.

  17. Forced convection and transport effects during hyperbaric laser chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Maxwell, James L [Los Alamos National Laboratory; Chavez, Craig A [Los Alamos National Laboratory; Espinoza, Miguel [Los Alamos National Laboratory; Black, Marcie [Los Alamos National Laboratory; Maskaly, Karlene [Los Alamos National Laboratory; Boman, Mats [UPPSALA UNIV

    2009-01-01

    This work explores mass transport processes during HP-LCYD, including the transverse forced-flow of precursor gases through a nozzle to enhance fiber growth rates. The use of laser trapping and suspension of nano-scale particles in the precursor flow is also described, providing insights into the nature of the gas flow, including jetting from the fiber tip and thermodiffusion processes near the reaction zone. The effects of differing molecular-weight buffer gases is also explored in conjunction with the Soret effect, and it is found that nucleation at the deposit surface (and homogeneous nucleation in the gas phase) can be enhanced/ retarded, depending on the buffer gas molecular weight. To demonstrate that extensive microstructures can be grown simultaneously, three-dimensional fiber arrays are also grown in-parallel using diffractive optics--without delatory effects from neighboring reaction sites.

  18. Mitigation of organic laser damage precursors from chemical processing of fused silica.

    Science.gov (United States)

    Baxamusa, S; Miller, P E; Wong, L; Steele, R; Shen, N; Bude, J

    2014-12-01

    Increases in the laser damage threshold of fused silica have been driven by the successive elimination of near-surface damage precursors such as polishing residue, fractures, and inorganic salts. In this work, we show that trace impurities in ultrapure water used to process fused silica optics may be responsible for the formation of carbonaceous deposits. We use surrogate materials to show that organic compounds precipitated onto fused silica surfaces form discrete damage precursors. Following a standard etching process, solvent-free oxidative decomposition using oxygen plasma or high-temperature thermal treatments in air reduced the total density of damage precursors to as low as inorganic compounds are more likely to cause damage when they are tightly adhered to a surface, which may explain why high-temperature thermal treatments have been historically unsuccessful at removing extrinsic damage precursors from fused silica.

  19. A precise length etalon generator controlled by femtosecond mode-locked laser

    Science.gov (United States)

    Šmid, Radek; Čip, Ondřej; Lazar, Josef

    2007-09-01

    The progress in the field of optical frequency standards is oriented to femtosecond mode-locked lasers stabilized by technique of the optical frequency synthesis. Such a laser produces a supercontinuum light, which is composed of a cluster of coherent frequency components in certain interval of wavelengths. A value of the repetition rate of femtosecond pulses determines (in the frequency domain) spacing of these coherent components. If we control the mode-locked laser by means of i.e. atomic clocks we ensure frequency of these components very stable. With respect to definition of SI unit "one meter" on basis of speed of light the stabilized mode-locked laser can be used for implementation of this definition by non-traditional way. In the work we present our proposal of a system, which converts excellent frequency stability of components generated by the mode-locked laser to a net of discrete absolute lengths represented by a distance of two mirrors of an optical resonator. On basis of theory, the optical resonator with a cavity length has a periodic frequency spectrum Similarly the frequency of i-th comb component could be written as: f i = f ceo + i f rep, where f ceo is the comb offset frequency and f rep is the repetition rate. For the simplicity we presume the offset frequency f ceo equals to zero. If the supercontinuum beam of the mode-locked laser illuminates the resonator and at the same time the cavity length L is adjusted to length L p = c / (2 p f rep ) then both spectra fit. The symbol 'p' is an integer value. It produces intensity maximum in the output of the cavity, which is detected by a photodetector and locked in the servo-loop. For absolute discrete values of cavity lengths L p that well satisfy the condition above we obtain precise etalons of length.

  20. Pain Reduction After Laser Acupuncture Treatment in Geriatric Patients with Knee Osteoarthritis: a Randomized Controlled Trial

    Directory of Open Access Journals (Sweden)

    Dwi R Helianthi

    2016-09-01

    Full Text Available Aim: to compare the effectiveness of active laser acupuncture with placebo on reducing pain intensity and improving functional outcome in geriatric patients with knee osteoarthritis (OA. Methods: a double-blind randomized controlled trial was conducted in geriatrics with knee OA at Medical Acupuncture Outpatient Clinic, Integrated Geriatric Outpatient Clinic, Rheumatology Outpatient Clinic of Cipto Mangunkusumo Hospital, Jakarta, during May to October 2015. Sixty two patients with knee OA  were randomly assigned into two groups: active laser acupuncture group or placebo laser acupuncture group. Interventions were carried out using a gallium aluminum arsenide laser device at the ST35 Dubi, ST36 Zusanli, SP9 Yinlingquan, GB34 Yanglingquan and EX - LE - 4 Neixiyan acupuncture points on the affected knee for ten sessions of treatment, i.e. twice a week. Patients were assessed using a visual analogue scale (VAS and Lequesne index at baseline, after four sessions, after nine sessions and at 2 weeks after the treatment had been stopped. Results: the VAS scores were significantly improved in the active laser acupuncture group compared to the placebo group. The evaluation of VAS scores was carried out after four treatment sessions (mean difference: 0.39; p<0.001, after nine treatment sessions (mean difference: 37.48; p<0.001 and at 2 weeks post intervention (mean difference: 39.15; p<0.001. The evaluation also showed significant improvement of Lequesne index after four treatment sessions (mean difference: 4.68; p<0.001, after nine treatment sessions (mean difference: 5.90; p<0.001 and at 2 weeks post intervention (mean difference: 6.48; p<0.001. Conclusion: active laser acupuncture is effective in reducing pain.