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Sample records for laser heating arrangement

  1. Arrangement in a heat recovery unit

    SciTech Connect

    Gustavsson, K.A.; Jansson, K.A.; Kruse, R.A.

    1983-03-22

    A heat recovery unit is adapted for installing in a cookery cupboard or the like space in a dwelling. Within a casing the unit has a lamella heat exchanger, which is arranged on one corner edge and has two of its defining surfaces provided with openings for passages facing upwards and two downwards. The heat exchanger has its end walls oriented in vertical planes. It is adapted for heating supply air through heat take-up from exhaust air. Four vertical wall portions form a cross above the heat exchanger, thus providing four chambers for the ingoing and outgoing air flows. By means of portions airtightly sealed against the casing and wall portions the heat exchanger is divided into two portions, each having a cross-stream course between supply air and exhaust air, with its passages for supply air and exhaust air arranged in series with the corresponding passages of the other portion. The heat exchanger is removable as a unit after opening the front of the casing.

  2. Liquid heat capacity lasers

    DOEpatents

    Comaskey, Brian J.; Scheibner, Karl F.; Ault, Earl R.

    2007-05-01

    The heat capacity laser concept is extended to systems in which the heat capacity lasing media is a liquid. The laser active liquid is circulated from a reservoir (where the bulk of the media and hence waste heat resides) through a channel so configured for both optical pumping of the media for gain and for light amplification from the resulting gain.

  3. Liquid heat capacity lasers

    DOEpatents

    Comaskey, Brian J.; Scheibner, Karl F.; Ault, Earl R.

    2007-05-01

    The heat capacity laser concept is extended to systems in which the heat capacity lasing media is a liquid. The laser active liquid is circulated from a reservoir (where the bulk of the media and hence waste heat resides) through a channel so configured for both optical pumping of the media for gain and for light amplification from the resulting gain.

  4. Laser Processed Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Hansen, Scott

    2017-01-01

    The Laser Processed Heat Exchanger project will investigate the use of laser processed surfaces to reduce mass and volume in liquid/liquid heat exchangers as well as the replacement of the harmful and problematic coatings of the Condensing Heat Exchangers (CHX). For this project, two scale unit test articles will be designed, manufactured, and tested. These two units are a high efficiency liquid/liquid HX and a high reliability CHX.

  5. Expedient arrangement of newly constructed systems for centralized heat supply

    NASA Astrophysics Data System (ADS)

    Zeigarnik, Yu. A.; Rotinov, A. G.

    2008-11-01

    It is shown that for newly constructed combined-cycle cogeneration plants and nuclear cogeneration plants, the optimum arrangement of the centralized heat supply system is the combination of a cogeneration plant and a district heat-supply station (a boiler house).

  6. Laser-heated thruster

    NASA Technical Reports Server (NTRS)

    Kemp, N. H.; Krech, R. H.

    1980-01-01

    The development of computer codes for the thrust chamber of a rocket of which the propellant gas is heated by a CW laser beam was investigated. The following results are presented: (1) simplified models of laser heated thrusters for approximate parametric studies and performance mapping; (3) computer programs for thrust chamber design; and (3) shock tube experiment to measure absorption coefficients. Two thrust chamber design programs are outlined: (1) for seeded hydrogen, with both low temperature and high temperature seeds, which absorbs the laser radiation continuously, starting at the inlet gas temperature; and (2) for hydrogen seeded with cesium, in which a laser supported combustion wave stands near the gas inlet, and heats the gas up to a temperature at which the gas can absorb the laser energy.

  7. Arrangement for damping the resonance in a laser diode

    NASA Technical Reports Server (NTRS)

    Katz, J.; Yariv, A.; Margalit, S. (Inventor)

    1985-01-01

    An arrangement for damping the resonance in a laser diode is described. This arrangement includes an additional layer which together with the conventional laser diode form a structure (35) of a bipolar transistor. Therein, the additional layer serves as the collector, the cladding layer next to it as the base, and the active region and the other cladding layer as the emitter. A capacitor is connected across the base and the collector. It is chosen so that at any frequency above a certain selected frequency which is far below the resonance frequency the capacitor impedance is very low, effectively shorting the base to the collector.

  8. Laser-heated thruster

    NASA Technical Reports Server (NTRS)

    Kemp, N. H.; Lewis, P. F.

    1980-01-01

    The development of a computer program for the design of the thrust chamber for a CW laser heated thruster was examined. Hydrodgen was employed as the propellant gas and high temperature absorber. The laser absorption coefficient of the mixture/laser radiation combination is given in temperature and species densities. Radiative and absorptive properties are given to determine radiation from such gas mixtures. A computer code for calculating the axisymmetric channel flow of a gas mixture in chemical equilibrium, and laser energy absorption and convective and radiative heating is described. It is concluded that: (1) small amounts of cesium seed substantially increase the absorption coefficient of hydrogen; (2) cesium is a strong radiator and contributes greatly to radiation of cesium seeded hydrogen; (3) water vapor is a poor absorber; and (4) for 5.3mcm radiation, both H2O/CO and NO/CO seeded hydrogen mixtures are good absorbers.

  9. Thermosyphon coil arrangement for heat pump outdoor unit

    DOEpatents

    Draper, R.

    1984-05-22

    For a heat pump, the outdoor unit is provided with a coil and a refrigerant flow arrangement there for which is such that in the heating mode of operation of the heat pump they operate in a thermosyphon fashion. The coil has a feed portion and an exit portion leading to a separator drum from which liquid refrigerant is returned through downcomer line for recirculation to the feed portion. The coil is tilted upwardly from entry to exit by the angle alpha to enhance the clearance of the two phases of refrigerant from each other in the heating mode of operation. There is no thermosyphon function in the cooling mode of operation. 9 figs.

  10. Thermosyphon coil arrangement for heat pump outdoor unit

    DOEpatents

    Draper, Robert

    1984-01-01

    For a heat pump, the outdoor unit is provided with a coil and a refrigerant flow arrangement therefor which is such that in the heating mode of operation of the heat pump they operate in a thermosyphon fashion. The coil 32 has a feed portion 30 and an exit portion 34 leading to a separator drum 36 from which liquid refrigerant is returned through downcomer line 42 for recirculation to the feed portion. The coil is tilted upwardly from entry to exit by the angle alpha to enhance the clearance of the two phases of refrigerant from each other in the heating mode of operation. There is no thermosyphon function in the cooling mode of operation.

  11. Examination of Coil Arrangement for Higher Quality Heating of the Induction Heating Cooker

    NASA Astrophysics Data System (ADS)

    Yonetsu, Daigo; Kawata, Kohei; Hara, Takehisa; Ujiie, Satoshi; Joto, Takaya; Masuda, Tadashi

    This paper proposes effective and practical design method of higher quality heating for induction-heating cooker. The IH cooker which has the simple pancake-shaped coil arrangement produces slightly nonuniform temperature distribution along the heating plate. The object of this research is to achieve the better heating performance by adjusting the arrangement of the coil. Easiness of coil winding is added to the evaluation basis. Eddy current analysis is made by the finite element method for calculating the heat distribution of the heating plate. After this, heat transfer analysis is made by the finite element method for calculating the temperature distribution of the heating plate. Multi-objective genetic algorithm is employed for obtaining the optimum arrangement of the coil. The two objectives that mean the uniformity of temperature distribution and the easiness of coil winding are both evaluated. By using the proposed method, we could obtain the expected coil arrangement easily. The temperature distribution approaches closer to uniform distribution by using the obtained coil arrangement which is not difficult to wind.

  12. Octahedral spherical hohlraum and its laser arrangement for inertial fusion

    SciTech Connect

    Lan, Ke; He, Xian-Tu; Liu, Jie; Zheng, Wudi; Lai, Dongxian

    2014-05-15

    A recent publication [K. Lan et al., Phys. Plasmas 21, 010704 (2014)] proposed a spherical hohlraum with six laser entrance holes of octahedral symmetry at a specific hohlraum-to-capsule radius ratio of 5.14 for inertial fusion study, which has robust high symmetry during the capsule implosion and superiority on low backscatter without supplementary technology. This paper extends the previous one by studying the laser arrangement and constraints of octahedral hohlraum in detail. As a result, it has serious beam crossing at θ{sub L}≤45°, and θ{sub L}=50° to 60° is proposed as the optimum candidate range for the golden octahedral hohlraum, here θ{sub L} is the opening angle that the laser quad beam makes with the Laser Entrance Hole (LEH) normal direction. In addition, the design of the LEH azimuthal angle should avoid laser spot overlapping on hohlraum wall and laser beam transferring outside hohlraum from a neighbor LEH. The octahedral hohlraums are flexible and can be applicable to diverse inertial fusion drive approaches. This paper also applies the octahedral hohlraum to the recent proposed hybrid indirect-direct drive approach.

  13. Heat exchanger and water tank arrangement for passive cooling system

    DOEpatents

    Gillett, James E.; Johnson, F. Thomas; Orr, Richard S.; Schulz, Terry L.

    1993-01-01

    A water storage tank in the coolant water loop of a nuclear reactor contains a tubular heat exchanger. The heat exchanger has tubesheets mounted to the tank connections so that the tubesheets and tubes may be readily inspected and repaired. Preferably, the tubes extend from the tubesheets on a square pitch and then on a rectangular pitch therebetween. Also, the heat exchanger is supported by a frame so that the tank wall is not required to support all of its weight.

  14. Laser-heated rocket studies

    NASA Technical Reports Server (NTRS)

    Kemp, N. H.; Root, R. G.; Wu., P. K. S.; Caledonia, G. E.; Pirri, A. N.

    1976-01-01

    CW laser heated rocket propulsion was investigated in both the flowing core and stationary core configurations. The laser radiation considered was 10.6 micrometers, and the working gas was unseeded hydrogen. The areas investigated included initiation of a hydrogen plasma capable of absorbing laser radiation, the radiation emission properties of hot, ionized hydrogen, the flow of hot hydrogen while absorbing and radiating, the heat losses from the gas and the rocket performance. The stationary core configuration was investigated qualitatively and semi-quantitatively. It was found that the flowing core rockets can have specific impulses between 1,500 and 3,300 sec. They are small devices, whose heating zone is only a millimeter to a few centimeters long, and millimeters to centimeters in radius, for laser power levels varying from 10 to 5,000 kW, and pressure levels of 3 to 10 atm. Heat protection of the walls is a vital necessity, though the fraction of laser power lost to the walls can be as low as 10% for larger powers, making the rockets thermally efficient.

  15. Heat exchanger and water tank arrangement for passive cooling system

    DOEpatents

    Gillett, J.E.; Johnson, F.T.; Orr, R.S.; Schulz, T.L.

    1993-11-30

    A water storage tank in the coolant water loop of a nuclear reactor contains a tubular heat exchanger. The heat exchanger has tube sheets mounted to the tank connections so that the tube sheets and tubes may be readily inspected and repaired. Preferably, the tubes extend from the tube sheets on a square pitch and then on a rectangular pitch there between. Also, the heat exchanger is supported by a frame so that the tank wall is not required to support all of its weight. 6 figures.

  16. Stability of laser heated flows

    NASA Technical Reports Server (NTRS)

    Wu, P. K. S.; Pirri, A. N.

    1976-01-01

    A local stability analysis is utilized to determine the stability of disturbances generated at each point along a nozzle of variable area ratio for a one-dimensional flow heated by laser radiation entering from the upstream direction. The governing equations for the quasi-one-dimensional flow without viscous dissipation, diffusion, and thermal conduction but including radiative heat transfer are given. The governing equations are combined to yield a relationship which governs the Mach number variation through the nozzle. The complete steady-state solution can be calculated from knowledge of the Mach number profile, the inlet conditions, and the laser power. The local stability analysis permits obtaining contour (or contours) of neutral stability. Solutions have been obtained for various nozzle configurations, but only one set of example calculations is presented. The results obtained indicate that the analysis serves as an important indicator as to where potential absorption wave phenomena may be initiated.

  17. Extreme heat arrangements in South Australia: an assessment of trigger temperatures.

    PubMed

    Williams, Susan; Nitschke, Monika; Tucker, Graeme; Bi, Peng

    2011-12-01

    The high mortality and morbidity associated with the 2009 heat wave across South Eastern Australia highlighted the need for effective heat-related health promotion and preventive strategies. The adverse health effects of extreme heat are largely preventable, and heat-related health promotion can advise the public about the dangers of hot weather and how to reduce health risks. The South Australian State Emergency Service has outlined a co-ordinated response system in their Extreme Heat Arrangements for South Australia. This paper evaluates the health impacts at the temperature trigger levels incorporated in this plan. Heat events in Adelaide between 1994 and 2009 were compared in terms of heat duration, heat intensity and their impact on mortality and ambulance call-outs.The health impacts for events meeting specific temperature triggers were estimated. Individual heat events varied in terms of estimated excess mortality and ambulance call-outs. Increased mortality was associated with heat events of 3 or more consecutive days with maximum temperature (T(max)) > or = 43 degrees C or average daily temperature (ADT) > or = 34 degrees C, while ambulance call-outs increased significantly at lower T(max) levels.The two events reaching the temperature triggers for an extreme heat warning were associated with a 44% (95% CI 26-63%) increase in mortality. The results support the temperature trigger for an extreme heat warning within the Extreme Heat Arrangements for Adelaide, and indicate a limited health impact at lower temperature triggers.

  18. Stress and Heat Transfer Analyses for Different Channel Arrangements of PCHE

    SciTech Connect

    Jong B. Lim; Robert G. Shrake; Eung S. Kim; Chang H. Oh

    2008-11-01

    Stress and heat transfer analyses are being performed on the different channel arrangements of Printed Circuit Heat Exchanger (PCHE) proposed for application of VHTRs using ABAQUS [ABAQUS, 2007] and COMSOL [COMSOL, 2007], respectively. The work is being done to determine the configuration that would result in minimum stress for the same heat performance. This paper discusses the effects of shifting the coolant channels in every other row to reduce stress.

  19. Compact laser through improved heat conductance

    NASA Technical Reports Server (NTRS)

    Yang, L. C.

    1975-01-01

    A 16-joule-pulse laser has been developed in which a boron nitride heat-conductor enclosure is used to remove heat from the elements. Enclosure is smaller and lighter than systems in which cooling fluids are used.

  20. Numerical investigation of thermal performance of a water-cooled mini-channel heat sink for different chip arrangement

    SciTech Connect

    Tikadar, Amitav Hossain, Md. Mahamudul; Morshed, A. K. M. M.

    2016-07-12

    Heat transfer from electronic chip is always challenging and very crucial for electronic industry. Electronic chips are assembled in various manners according to the design conditions and limitationsand thus the influence of chip assembly on the overall thermal performance needs to be understand for the efficient design of electronic cooling system. Due to shrinkage of the dimension of channel and continuous increment of thermal load, conventional heat extraction techniques sometimes become inadequate. Due to high surface area to volume ratio, mini-channel have the natural advantage to enhance convective heat transfer and thus to play a vital role in the advanced heat transfer devices with limited surface area and high heat flux. In this paper, a water cooled mini-channel heat sink was considered for electronic chip cooling and five different chip arrangements were designed and studied, namely: the diagonal arrangement, parallel arrangement, stacked arrangement, longitudinal arrangement and sandwiched arrangement. Temperature distribution on the chip surfaces was presented and the thermal performance of the heat sink in terms of overall thermal resistance was also compared. It is found that the sandwiched arrangement of chip provides better thermal performance compared to conventional in line chip arrangement.

  1. Numerical investigation of thermal performance of a water-cooled mini-channel heat sink for different chip arrangement

    NASA Astrophysics Data System (ADS)

    Tikadar, Amitav; Hossain, Md. Mahamudul; Morshed, A. K. M. M.

    2016-07-01

    Heat transfer from electronic chip is always challenging and very crucial for electronic industry. Electronic chips are assembled in various manners according to the design conditions and limitationsand thus the influence of chip assembly on the overall thermal performance needs to be understand for the efficient design of electronic cooling system. Due to shrinkage of the dimension of channel and continuous increment of thermal load, conventional heat extraction techniques sometimes become inadequate. Due to high surface area to volume ratio, mini-channel have the natural advantage to enhance convective heat transfer and thus to play a vital role in the advanced heat transfer devices with limited surface area and high heat flux. In this paper, a water cooled mini-channel heat sink was considered for electronic chip cooling and five different chip arrangements were designed and studied, namely: the diagonal arrangement, parallel arrangement, stacked arrangement, longitudinal arrangement and sandwiched arrangement. Temperature distribution on the chip surfaces was presented and the thermal performance of the heat sink in terms of overall thermal resistance was also compared. It is found that the sandwiched arrangement of chip provides better thermal performance compared to conventional in line chip arrangement.

  2. Heating of solid targets with laser pulses

    NASA Technical Reports Server (NTRS)

    Bechtel, J. H.

    1975-01-01

    Analytical and numerical solutions to the heat-conduction equation are obtained for the heating of absorbing media with pulsed lasers. The spatial and temporal form of the temperature is determined using several different models of the laser irradiance. Both surface and volume generation of heat are discussed. It is found that if the depth of thermal diffusion for the laser-pulse duration is large compared to the optical-attenuation depth, the surface- and volume-generation models give nearly identical results. However, if the thermal-diffusion depth for the laser-pulse duration is comparable to or less than the optical-attenuation depth, the surface-generation model can give significantly different results compared to the volume-generation model. Specific numerical results are given for a tungsten target irradiated by pulses of different temporal durations and the implications of the results are discussed with respect to the heating of metals by picosecond laser pulses.

  3. An Experimental Study of a Radially Arranged Thin Film Heat Flux Gauge

    NASA Technical Reports Server (NTRS)

    Cho, Christoper S. K.; Fralick, Gustave C.; Bhatt, Hemanshu D.

    1997-01-01

    A new thin-film heat-flux gauge was designed and fabricated on three different substrate materials. Forty pairs of Pt-Pt/10% Rh thermocouple junctions were deposited in a circular pattern on the same plane of the substrate. Over the thermocouples, 5 and 10 micron thick thermal resistance layers were deposited to create a temperature gradient across those layers. Calibration and testing of these gauges were carried out in an arc-lamp calibration facility. The heat flux calculated from the gauge output is in good agreement with the value obtained from the pre-calibrated standard sensor. A CO2 laser was also used to test the steady-state and dynamic responses of the heat-flux gauge. During the steady-state test, the time constant for the heating period was 30 s. The frequency response of the heat-flux gauge was measured in the frequency domain using a CO2 laser and a chopper. The responses from an infrared detector and the heat-flux gauge were measured simultaneously and compared. It was found that the thin-film heat-flux gauge has a dynamic frequency response of 3 kHz.

  4. Compact pulsed laser having improved heat conductance

    NASA Technical Reports Server (NTRS)

    Yang, L. C. (Inventor)

    1977-01-01

    A highly efficient, compact pulsed laser having high energy to weight and volume ratios is provided. The laser utilizes a cavity reflector that operates as a heat sink and is essentially characterized by having a high heat conductivity, by being a good electrical insulator and by being substantially immune to the deleterious effects of ultra-violet radiation. Manual portability is accomplished by eliminating entirely any need for a conventional circulating fluid cooling system.

  5. Joining of materials using laser heating

    DOEpatents

    Cockeram, Brian V.; Hicks, Trevor G.; Schmid, Glenn C.

    2003-07-01

    A method for diffusion bonding ceramic layers such as boron carbide, zirconium carbide, or silicon carbide uses a defocused laser beam to heat and to join ceramics with the use of a thin metal foil insert. The metal foil preferably is rhenium, molybdenum or titanium. The rapid, intense heating of the ceramic/metal/ceramic sandwiches using the defocused laser beam results in diffusive conversion of the refractory metal foil into the ceramic and in turn creates a strong bond therein.

  6. Plasma heating effects during laser welding

    NASA Astrophysics Data System (ADS)

    Lewis, G. K.; Dixon, R. D.

    Laser welding is a relatively low heat input process used in joining precisely machined components with minimum distortion and heat affects to surrounding material. The CO2 (10.6 (MU)m) and Nd-YAG (1.06 (MU)m) lasers are the primary lasers used for welding in industry today. Average powers range up to 20 kW for CO2 and 400 W for Nd-YAG with pulse lengths of milliseconds to continuous wave. Control of the process depends on an understanding of the laser-plasma-material interaction and characterization of the laser beam being used. Inherent plasma formation above the material surface and subsequent modulation of the incident laser radiation directly affect the energy transfer to the target material. The temporal and spatial characteristics of the laser beam affect the available power density incident on the target, which is important in achieving repeatability in the process. Other factors such as surface texture, surface contaminants, surface chemistry, and welding environment affect plasma formation which determines the weld penetration. This work involves studies of the laser-plasma-material interaction process and particularly the effect of the plasma on the coupling of laser energy to a material during welding. A pulsed Nd-YAG laser was used with maximum average power of 400 W.

  7. Acoustic Levitator With Furnace And Laser Heating

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B.; Stoneburner, James D.

    1991-01-01

    Acoustic-levitation apparatus incorporates electrical-resistance furnace for uniform heating up to temperature of about 1,000 degrees C. Additional local heating by pair of laser beams raise temperature of sample to more than 1,500 degrees C. High temperature single-mode acoustic levitator generates cylindrical-mode accoustic resonance levitating sample. Levitation chamber enclosed in electrical-resistance furnace. Infrared beams from Nd:YAG laser provide additional local heating of sample. Designed for use in containerless processing of materials in microgravity or in normal Earth gravity.

  8. Measurement of heat pump processes induced by laser radiation

    NASA Technical Reports Server (NTRS)

    Garbuny, M.; Henningsen, T.

    1983-01-01

    A series of experiments was performed in which a suitably tuned CO2 laser, frequency doubled by a Tl3AsSe37 crystal, was brought into resonance with a P-line or two R-lines in the fundamental vibration spectrum of CO. Cooling or heating produced by absorption in CO was measured in a gas-thermometer arrangement. P-line cooling and R-line heating could be demonstrated, measured, and compared. The experiments were continued with CO mixed with N2 added in partial pressures from 9 to 200 Torr. It was found that an efficient collisional resonance energy transfer from CO to N2 existed which increased the cooling effects by one to two orders of magnitude over those in pure CO. Temperature reductions in the order of tens of degrees Kelvin were obtained by a single pulse in the core of the irradiated volume. These measurements followed predicted values rather closely, and it is expected that increase of pulse energies and durations will enhance the heat pump effects. The experiments confirm the feasibility of quasi-isentropic engines which convert laser power into work without the need for heat rejection. Of more immediate potential interest is the possibility of remotely powered heat pumps for cryogenic use, such applications are discussed to the extent possible at the present stage.

  9. Replicated diffractive optical lens components for laser-diode-to-fiber coupling in optical bench arrangements

    NASA Astrophysics Data System (ADS)

    Soechtig, Juergen; Schift, Helmut; Patterson, Bruce D.; Westenhoefer, S.

    1997-09-01

    We report on the fabrication of lens components, based on diffractive optical elements, for the purpose of imaging laser-diode emission onto fibers or photodetectors, or for collimation applications. The miniature optical elements are arranged in arrays with 250 micrometer pitch which make them well suited for applications with fiber ribbons. Test optical plates were made of polycarbonate using hot stamper replication technology. The imaging properties of these optical plates from single-mode fibers onto single-mode fibers or from lasers onto single-mode fibers are discussed. The addition of 3D-marker structures to the outline borders of such plates made them suitable for use in micro-optical benches with built-in mechanical registration structures. We fabricated the optical bench inserts with built-in passive alignment elements using deep x-ray LIGA technology (LIGA is a German acronym for 'lithographie, galvanik und abformung' meaning lithography, electroforming and molding). This technology offers high mechanical precision even for the 500 micrometer thick optical bench inserts which we fabricated by injection molding out of transparent and thermally stable polycarbonate. We report on first arrangements of plastic optical bench inserts into micro-optical benches. With the aim towards a fully replicated micro-optical bench made out of plastic we also report on a mounting concept for laser-didoes with built-in alignment trenches. The fabrication process and important properties of these special lasers which we recently developed for transceiver applications are described. We use these lasers for imaging onto single-mode fibers applying the diffractive optical element plates already mentioned.

  10. Same magnetic nanoparticles, different heating behavior: Influence of the arrangement and dispersive medium

    NASA Astrophysics Data System (ADS)

    Andreu, Irene; Natividad, Eva; Solozábal, Laura; Roubeau, Olivier

    2015-04-01

    The heating ability of the same magnetic nanoparticles (MNPs) dispersed in different media has been studied in the 170-310 K temperature range. For this purpose, the biggest non-twinned nanoparticles have been selected among a series of magnetite nanoparticles of increasing sizes synthesized via a seeded growth method. The sample with nanoparticles dispersed in n-tetracosane, thermally quenched from 100 °C and solid in the whole measuring range, follows the linear response theoretical behavior for non-interacting nanoparticles, and displays a remarkably large maximum specific absorption rate (SAR) value comparable to that of magnetosomes at the alternating magnetic fields used in the measurements. The other samples, with nanoparticles dispersed either in alkane solvents of sub-ambient melting temperatures or in epoxy resin, display different thermal behaviors and maximum SAR values ranging between 11 and 65% of that achieved for the sample with n-tetracosane as dispersive medium. These results highlight the importance of the MNPs environment and arrangement to maintain optimal SAR values, and may help to understand the disparity sometimes found between MNPs heating performance measured in a ferrofluid and after injection in an animal model, where MNP arrangement and environment are not the same.

  11. Heat profiles of laser-irradiated nails.

    PubMed

    Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A; Kendler, Michael; Simon, Jan C; Grunewald, Sonja

    2014-01-01

    Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.

  12. Heat profiles of laser-irradiated nails

    NASA Astrophysics Data System (ADS)

    Paasch, Uwe; Nenoff, Pietro; Seitz, Anna-Theresa; Wagner, Justinus A.; Kendler, Michael; Simon, Jan C.; Grunewald, Sonja

    2014-01-01

    Onychomycosis is a worldwide problem with no tendency for self-healing, and existing systemic treatments achieve disease-free nails in only 35 to 76% of cases. Recently, treatment of nail fungus with a near-infrared laser has been introduced. It is assumed that fungal eradication is mediated by local heat. To investigate if laser treatment has the potential to eradicate fungal hyphae and arthrospores, laser heat application and propagation needs to be studied in detail. This study aimed to measure nail temperatures using real-time videothermography during laser irradiation. Treatment was performed using 808- and 980-nm linear scanning diode lasers developed for hair removal, enabling contact-free homogeneous irradiation of a human nail plate in one pass. Average and peak temperatures increased pass by pass, while the laser beam moved along the nail plates. The achieved mean peak temperatures (808 nm: 74.1 to 112.4°C, 980 nm: 45.8 to 53.5°C), as well as the elevation of average temperatures (808 nm: 29.5 to 38.2°C, 980 nm: 27.1 to 32.6°C) were associated with pain that was equivalent to that of hair removal procedures and was not significantly different for various wavelengths. The linear scanning laser devices provide the benefits of contact-free homogeneous heating of the human nail while ensuring adequate temperature rises.

  13. Heat pump processes induced by laser radiation

    NASA Technical Reports Server (NTRS)

    Garbuny, M.; Henningsen, T.

    1980-01-01

    A carbon dioxide laser system was constructed for the demonstration of heat pump processes induced by laser radiation. The system consisted of a frequency doubling stage, a gas reaction cell with its vacuum and high purity gas supply system, and provisions to measure the temperature changes by pressure, or alternatively, by density changes. The theoretical considerations for the choice of designs and components are dicussed.

  14. Heat Transfer Characteristics of Impinging Jets by Four Circular Nozzles Arranged in Square-type

    NASA Astrophysics Data System (ADS)

    Ichimiya, Koichi

    This paper presents the experimental results on the impingement heat transfer by 4-circular nozzles arranged in square type. Experiments were performed for the dimensionless space H(= h/D)=0.5-8,the Reynolds number Re(= VoD/v)=3000-40000, and the dimensionless pitch Pi(= pi/D)=8. The two-dimensional behavior of the local Nusselt number was corresponded to the flow visualization by oil film method on the impingement surface. The average Nusselt number was expressed by the geometric function and Re2/3. The maximum average Nusselt number was obtained at the dimensionless nozzle-impingement surface spacing H=2 for constant Reynolds number.

  15. Laser-heated rocket thruster

    NASA Technical Reports Server (NTRS)

    Shoji, J. M.

    1977-01-01

    A space vehicle application using 5,000-kw input laser power was conceptually evaluated. A detailed design evaluation of a 10-kw experimental thruster including plasma size, chamber size, cooling, and performance analyses, was performed for 50 psia chamber pressure and using hydrogen as a propellant. The 10-kw hardware fabricated included a water cooled chamber, an uncooled copper chamber, an injector, igniters, and a thrust stand. A 10-kw optical train was designed.

  16. Laser-Heated Rocket Thruster.

    DTIC Science & Technology

    1977-05-01

    chamber assembly , thrust stand, and plasma initiation system). A space vehicle application using 5000kw input laser power was conceptually evaluated...State Temperature Distribution 137 89. 10-KW Optical Train Assembly (M = 2.0) 139/140 90. 10-KW Optical Train Assembly (M = 1.523) 141/142 91...10-KW Water-Cooled Chamber Assembly and Detail . . . 149/150 95. 10-KW Thruster Assembly . . 153/154 96. Uncooled Chamber Assembly . 155/156 97

  17. Heat accumulation during pulsed laser materials processing.

    PubMed

    Weber, Rudolf; Graf, Thomas; Berger, Peter; Onuseit, Volkher; Wiedenmann, Margit; Freitag, Christian; Feuer, Anne

    2014-05-05

    Laser materials processing with ultra-short pulses allows very precise and high quality results with a minimum extent of the thermally affected zone. However, with increasing average laser power and repetition rates the so-called heat accumulation effect becomes a considerable issue. The following discussion presents a comprehensive analytical treatment of multi-pulse processing and reveals the basic mechanisms of heat accumulation and its consequence for the resulting processing quality. The theoretical findings can explain the experimental results achieved when drilling microholes in CrNi-steel and for cutting of CFRP. As a consequence of the presented considerations, an estimate for the maximum applicable average power for ultra-shorts pulsed laser materials processing for a given pulse repetition rate is derived.

  18. Laser Processed Condensing Heat Exchanger Technology Development

    NASA Technical Reports Server (NTRS)

    Hansen, Scott; Wright, Sarah; Wallace, Sarah; Hamilton, Tanner; Dennis, Alexander; Zuhlke, Craig; Roth, Nick; Sanders, John

    2017-01-01

    The reliance on non-permanent coatings in Condensing Heat Exchanger (CHX) designs is a significant technical issue to be solved before long-duration spaceflight can occur. Therefore, high reliability CHXs have been identified by the Evolvable Mars Campaign (EMC) as critical technologies needed to move beyond low earth orbit. The Laser Processed Condensing Heat Exchanger project aims to solve these problems through the use of femtosecond laser processed surfaces, which have unique wetting properties and potentially exhibit anti-microbial growth properties. These surfaces were investigated to identify if they would be suitable candidates for a replacement CHX surface. Among the areas researched in this project include microbial growth testing, siloxane flow testing in which laser processed surfaces were exposed to siloxanes in an air stream, and manufacturability.

  19. Convective heat flux in a laser-heated thruster

    NASA Technical Reports Server (NTRS)

    Wu, P. K. S.

    1978-01-01

    An analysis is performed to estimate the convective heating to the wall in a laser-heated thruster on the basis of a solution of the laminar boundary-layer equations with variable transport properties. A local similiarity approximation is used, and it is assumed that the gas phase is in equilibrium. For the thruster described by Wu (1976), the temperature and pressure distributions along the nozzle are obtained from the core calculation. The similarity solutions and heat flux are obtained from the freestream conditions of the boundary layer, in order to determine if it is necessary to couple the boundary losses directly to the core calculation. In addition, the effects of mass injection on the convective heat transfer across the boundary layer with large density-viscosity product gradient are examined.

  20. Laser-Induced Heating in Optical Traps

    PubMed Central

    Peterman, Erwin J. G.; Gittes, Frederick; Schmidt, Christoph F.

    2003-01-01

    In an optical tweezers experiment intense laser light is tightly focused to intensities of MW/cm2 in order to apply forces to submicron particles or to measure mechanical properties of macromolecules. It is important to quantify potentially harmful or misleading heating effects due to the high light intensities in biophysical experiments. We present a model that incorporates the geometry of the experiment in a physically correct manner, including heat generation by light absorption in the neighborhood of the focus, balanced by outward heat flow, and heat sinking by the glass surfaces of the sample chamber. This is in contrast to the earlier simple models assuming heat generation in the trapped particle only. We find that in the most common experimental circumstances, using micron-sized polystyrene or silica beads, absorption of the laser light in the solvent around the trapped particle, not in the particle itself, is the most important contribution to heating. To validate our model we measured the spectrum of the Brownian motion of trapped beads in water and in glycerol as a function of the trapping laser intensity. Heating both increases the thermal motion of the bead and decreases the viscosity of the medium. We measured that the temperature in the focus increased by 34.2 ± 0.1 K/W with 1064-nm laser light for 2200-nm-diameter polystyrene beads in glycerol, 43.8 ± 2.2 K/W for 840-nm polystyrene beads in glycerol, 41.1 ± 0.7 K/W for 502-nm polystyrene beads in glycerol, and 7.7 ± 1.2 K/W for 500-nm silica beads and 8.1 ± 2.1 K/W for 444-nm silica beads in water. Furthermore, we observed that in glycerol the heating effect increased when the bead was trapped further away from the cover glass/glycerol interface as predicted by the model. We show that even though the heating effect in water is rather small it can have non-negligible effects on trap calibration in typical biophysical experimental circumstances and should be taken into consideration when laser

  1. Rapid heating of matter using high power lasers

    SciTech Connect

    Bang, Woosuk

    2016-04-08

    This slide presentation describes motivation (uniform and rapid heating of a target, opportunity to study warm dense matter, study of nuclear fusion reactions), rapid heating of matter with intense laser-driven ion beams, visualization of the expanding warm dense gold and diamond, and nuclear fusion experiments using high power lasers (direct heating of deuterium spheres (radius ~ 10nm) with an intense laser pulse.

  2. The Effect of Circuiting Arrangement on the Thermal Performance of Refrigeration Mixtures in Tube-and-Fin Condensing Heat Exchangers

    SciTech Connect

    Chen, D.T.; Conklin, J.C.

    1999-03-15

    For the pure or azeotropic refrigerants typically used in present air conditioning and refrigeration applications, the refrigerant changes phase at a constant temperature. Thus, the refrigerant circuiting arrangement such as crossfiow, counterfiow, or cross-counterflow, has no effect on the thermal performance. For zeotropic refrigerant mixtures, however, the phase-change occurs over a temperature range, or "glide", and the refrigerant circuiting arrangement, or flow path through the heat exchanger, can affect the thermal performance of both the heat exchangers as well as the overall efficiency of the vapor compression cooling cycle. The effects of tsvo diflerent circuiting arrangements on the thermal performance of a zeotropic retligerant mixture and an almost azeotropic refrigerant mixture in a four-row cross-countertlow heat exchanger arrangement are reported here. The two condensers differ only in the manner of circuiting the refrigerant tubes, where one has refrigerant always flowing downward in the active heat transfer region ("identical order") and the other has refrigerant alternating flow direction in the active heat transfer region ("inverted order"). All other geometric parameters, such as bce are% fin louver geometry, refrigerant tube size and enhancement etc., are the same for both heat exchangers. One refrigerant mixture (R-41OA) un&rgoes a small temperature change ("low glide") during phase change, and the other retligerant mixture (a multi- component proprietary mixture) has a substantial temperature change ("high glide") of approximately 10"C during the phase change process. The overall thermal conductance, two-phase conductance, and pressure drop are presented. For the flow conditions of these tests, which are representative of resi&ntial cooling conditions, inverted order circuiting is more desirable than identical order. The potential thermal advantages of the i&ntical order arrangement for high-glide zeotropic refrigerant mixtures are negated

  3. Hybrid heat capacity-moving slab solid-state laser

    DOEpatents

    Stappaerts, Eddy A.

    2005-03-01

    Laser material is pumped and its stored energy is extracted in a heat capacity laser mode at a high duty factor. When the laser material reaches a maximum temperature, it is removed from the lasing region and a subsequent volume of laser material is positioned into the lasing region to repeat the lasing process. The heated laser material is cooled passively or actively outside the lasing region.

  4. Laser-heated emissive plasma probe

    SciTech Connect

    Schrittwieser, Roman; Ionita, Codrina; Balan, Petru; Gstrein, Ramona; Grulke, Olaf; Windisch, Thomas; Brandt, Christian; Klinger, Thomas; Madani, Ramin; Amarandei, George; Sarma, Arun K.

    2008-08-15

    Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.

  5. The Solid-State Heat-Capacity Laser

    SciTech Connect

    Rotter, M D; Dane, C B; Gonzales, S A; Merrill, R D; Mitchell, S C; Parks, C W; Yamamoto, R M

    2003-12-08

    Heat-capacity operation of a laser is a novel method by which high average powers can be generated. In this paper, we present the principles behind heat-capacity operation, in addition to describing the results of recent experiments.

  6. Laser-heated rotating specimen autoignition test

    NASA Technical Reports Server (NTRS)

    Au, A. C.

    1988-01-01

    Specimens of 440 C steel were rotated in a chamber pressurized with oxygen gas and heated with a 5-kW CO2 laser to determine the temperature required for autoignition to occur. Tests included exposures of static and rotating (25,000 rpm) specimens in oxygen pressurized to 5.51 MPa, and with focused laser fluences of more than 3.5 billion W/sq m. Specimen surface temperatures were monitored with a scanning infrared camera. Temperature measurement difficulties were experienced due to a problem with internal reflection inside the test chamber; however, posttest specimen examinations confirmed that surface melt (1371 C) was achieved in several tests. No sustained combustion was initiated in any rotating specimen. One static specimen was ignited. Results indicated that conditions necessary for autoignition of 440 C steel are more dependent on specimen geometry and available heat removal mechanisms. Sustained combustion occurred in the ignited static specimen with an estimated 130 C/sec cooling rate due to conduction. The rotating specimens could not sustain combustion due to a greater conductive/convective cooling rate of about 4000 C/sec and ejection of molten material. These results were applied to the Space Shuttle Main Engine (SSME) oxygen turbopump bearings to conclude that the LOX-cooled 440 C steel bearings cannot sustain combustion initiated by skidding friction.

  7. Radial Distribution of Absorption in a Cesium Heat Pipe with Axial Laser Heating

    DTIC Science & Technology

    2011-03-01

    Diode Pumped Alkali Lasers (DPAL) have been scaled to greater than 100 W and exhibit slope efficiencies...Iodine Laser DoD Department of Defense DoE Department of Energy DPAL Diode Pumped Alkali Laser DPSSL Diode Pumped Solid State Laser FWHM Full Width...PIPE WITH AXIAL LASER HEATING I. Introduction 1. Background Diode Pumped Alkali Lasers (DPALs) have recently been demonstrated

  8. In situ monitoring of plasma etch processes with a quantum cascade laser arrangement in semiconductor industrial environment

    NASA Astrophysics Data System (ADS)

    Lang, N.; Röpcke, J.; Zimmermann, H.; Steinbach, A.; Wege, S.

    2009-03-01

    Concentrations of the etch product SiF4 were measured online and in situ in technological etch plasmas with an especially designed quantum cascade laser arrangement for application in semiconductor industrial environment, the Q-MACS Etch. The combination of quantum cascade lasers and infra red absorption spectroscopy (QCLAS) opens up new attractive possibilities for plasma process monitoring and control. With the realization of a specific interface the Q-MACS Etch system is synchronized to the etch process and allows therefore automated measurements, which is important in a high volume production environment.

  9. A heated vapor cell unit for dichroic atomic vapor laser lock in atomic rubidium

    NASA Astrophysics Data System (ADS)

    McCarron, Daniel J.; Hughes, Ifan G.; Tierney, Patrick; Cornish, Simon L.

    2007-09-01

    The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D2 transitions in atomic rubidium is described. A 5 cm long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude.

  10. A heated vapor cell unit for dichroic atomic vapor laser lock in atomic rubidium.

    PubMed

    McCarron, Daniel J; Hughes, Ifan G; Tierney, Patrick; Cornish, Simon L

    2007-09-01

    The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D(2) transitions in atomic rubidium is described. A 5 cm long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude.

  11. High-intensity laser heating in liquids: Multiphoton absorption

    SciTech Connect

    Longtin, J.P.; Tien, C.L.

    1995-12-31

    At high laser intensities, otherwise transparent liquids can absorb strongly by the mechanism of multiphoton absorption, resulting in absorption and heating several orders of magnitude greater than classical, low-intensity mechanisms. The use of multiphoton absorption provides a new mechanism for strong, controlled energy deposition in liquids without bulk plasma formation, shock waves, liquid ejection, etc., which is of interest for many laser-liquid applications, including laser desorption of liquid films, laser particle removal, and laser water removal from microdevices. This work develops a microscopically based model of the heating during multiphoton absorption in liquids. The dependence on pulse duration, intensity, wavelength, repetition rate, and liquid properties is discussed. Pure water exposed to 266 nm laser radiation is investigated, and a novel heating mechanism for water is proposed that uses multiple-wavelength laser pulses.

  12. Solid-State Heat-Capacity-Laser Review

    SciTech Connect

    Rotter, M D; Dane, C B

    2002-05-07

    We describe our recent progress in the area of solid-state heat-capacity-lasers (SSHCL). In particular, we examine the physics of heat-capacity operation of a solid state laser and give the present technology status of our 10 kW flashlamp-pumped laser The current status of work leading to a diode-pumped Nd:GGG HCL is also described.

  13. Laser Measurement Of Convective-Heat-Transfer Coefficient

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.

    1994-01-01

    Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.

  14. Laser Measurement Of Convective-Heat-Transfer Coefficient

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.; Keith, Theo G., Jr.

    1994-01-01

    Coefficient of convective transfer of heat at spot on surface of wind-tunnel model computed from measurements acquired by developmental laser-induced-heat-flux technique. Enables non-intrusive measurements of convective-heat-transfer coefficients at many points across surfaces of models in complicated, three-dimensional, high-speed flows. Measurement spot scanned across surface of model. Apparatus includes argon-ion laser, attenuator/beam splitter electronic shutter infrared camera, and subsystem.

  15. Absorptivity Measurements and Heat Source Modeling to Simulate Laser Cladding

    NASA Astrophysics Data System (ADS)

    Wirth, Florian; Eisenbarth, Daniel; Wegener, Konrad

    The laser cladding process gains importance, as it does not only allow the application of surface coatings, but also additive manufacturing of three-dimensional parts. In both cases, process simulation can contribute to process optimization. Heat source modeling is one of the main issues for an accurate model and simulation of the laser cladding process. While the laser beam intensity distribution is readily known, the other two main effects on the process' heat input are non-trivial. Namely the measurement of the absorptivity of the applied materials as well as the powder attenuation. Therefore, calorimetry measurements were carried out. The measurement method and the measurement results for laser cladding of Stellite 6 on structural steel S 235 and for the processing of Inconel 625 are presented both using a CO2 laser as well as a high power diode laser (HPDL). Additionally, a heat source model is deduced.

  16. Thermal control of a lidar laser system using a non-conventional ram air heat exchanger

    NASA Technical Reports Server (NTRS)

    Killough, Brian D.; Alexander, William, Jr.; Swofford, Doyle P.

    1990-01-01

    This paper describes the analysis and performance testing of a uniquely designed external heat exchanger. The heat exchanger is attached externally to an aircraft and is used to cool a laser system within the fuselage. Estimates showed insufficient cooling capacity with a conventional staggered tube array in the limited space available. Thus, a non-conventional design wes developed with larger tube and fin area exposed to the ram air to increase the heat transfer performance. The basic design consists of 28 circular finned aluminum tubes arranged in two parallel banks. Wind tunnel tests were performed to simulate air and liquid flight conditions for the non-conventional parallel bank arrangement and the conventional staggered tube arrangement. Performance comparisons of each of the two designs are presented. Test results are used in a computer model of the heat exchanger to predict the operating performance for the entire flight profile. These analyses predict significantly improved performance over the conventional design and show adequate thermal control margins.

  17. Thermal control of a lidar laser system using a non-conventional ram air heat exchanger

    NASA Technical Reports Server (NTRS)

    Killough, Brian D.; Alexander, William, Jr.; Swofford, Doyle P.

    1990-01-01

    This paper describes the analysis and performance testing of a uniquely designed external heat exchanger. The heat exchanger is attached externally to an aircraft and is used to cool a laser system within the fuselage. Estimates showed insufficient cooling capacity with a conventional staggered tube array in the limited space available. Thus, a non-conventional design wes developed with larger tube and fin area exposed to the ram air to increase the heat transfer performance. The basic design consists of 28 circular finned aluminum tubes arranged in two parallel banks. Wind tunnel tests were performed to simulate air and liquid flight conditions for the non-conventional parallel bank arrangement and the conventional staggered tube arrangement. Performance comparisons of each of the two designs are presented. Test results are used in a computer model of the heat exchanger to predict the operating performance for the entire flight profile. These analyses predict significantly improved performance over the conventional design and show adequate thermal control margins.

  18. INTERACTION OF LASER RADIATION WITH MATTER: Estimates of phase-transition heats in steels and ceramics heated by laser radiation

    NASA Astrophysics Data System (ADS)

    Tsar'kova, O. G.; Garnov, Sergei V.

    2003-08-01

    Measurements of the high-temperature dependences of the heat capacity of solids heated by high-power laser radiation and the model of formation of structural point defects (vacancies) are used to estimate the heats of sublimation, evaporation and melting, as well as enthalpy of phase transformations for modern processing of steels and ceramics.

  19. Mathematical study of probe arrangement and nanoparticle injection effects on heat transfer during cryosurgery.

    PubMed

    Mirkhalili, Seyyed Mostafa; Ramazani S A, Ahmad; Nazemidashtarjandi, Saeed

    2015-11-01

    Blood vessels, especially large vessels have a greater thermal effect on freezing tissue during cryosurgery. Vascular networks act as heat sources in tissue, and cause failure in cryosurgery and reappearance of cancer. The aim of this study is to numerically simulate the effect of probe location and multiprobe on heat transfer distribution. Furthermore, the effect of nanoparticles injection is studied. It is shown that the small probes location near large blood vessels could help to reduce the necessary time for tissue freezing. Nanoparticles injection shows that the thermal effect of blood vessel in tissue is improved. Using Au, Ag and diamond nanoparticles have the most growth of ice ball during cryosurgery. However, polytetrafluoroethylene (PTFE) nanoparticle can be used to protect normal tissue around tumor cell due to its influence on reducing heat transfer in tissue. Introduction of Au, Ag and diamond nanoparticles combined with multicryoprobe in this model causes reduction of tissue average temperature about 50% compared to the one probe.

  20. Comparison of Hydrodynamic and Thermal Performance of Micro Heat Sinks with Inline and Staggered Arrangements of Cylindrical Micro Pin Fins

    NASA Astrophysics Data System (ADS)

    Mohammadi, Ali; Kosar, Ali; Faculty Of Engineering; Natural Sciences (Fens) Collaboration; Nanotechnology Research; Application Center (Sunum) Collaboration

    2016-11-01

    This computational study compares the hydrodynamic and thermal characteristics of flow inside a rectangular microchannel with different in-line and staggered arrangements of cylindrical micro pin fins (MPF). The channel dimensions are 5000 x 1500 x 100 µm3 (l x w x h) while the height and diameter of MPFs are both 100 µm which results in the H/D ratio of 1. Two different values of 1.5 and 3 are considered for the horizontal and vertical pitch ratios (SL/D and ST/D) among MPFs in each of the in-line and staggered arrangements which results in eight configurations. A constant heat flux of 30 W/cm2 is applied through the bottom section of microchannel as well as the liquid interacting surfaces of MPFs. The flow field is simulated at five different Reynolds numbers of 20, 40, 80, 120 and 160 using ANSYS FLUENT v.14.5. Four parameters of pressure drop, friction factor, Nusselt number and Thermal Performance Index (TPI) are used to analyze the hydrodynamic and thermal performance of micro heat sinks. Results show a great dependency of evaluating parameters on the vertical pitch ratios while minor dependencies are seen on the horizontal pitch ratio.

  1. In-volume heating using high-power laser diodes

    NASA Astrophysics Data System (ADS)

    Denisenkov, Valentin S.; Kiyko, Vadim V.; Vdovin, Gleb V.

    2015-03-01

    High-power lasers are useful instruments suitable for applications in various fields; the most common industrial applications include cutting and welding. We propose a new application of high-power laser diodes as in-bulk heating source for food industry. Current heating processes use surface heating with different approaches to make the heat distribution more uniform and the process more efficient. High-power lasers can in theory provide in-bulk heating which can sufficiently increase the uniformity of heat distribution thus making the process more efficient. We chose two media (vegetable fat and glucose) for feasibility experiments. First, we checked if the media have necessary absorption coefficients on the wavelengths of commercially available laser diodes (940-980 nm). This was done using spectrophotometer at 700-1100 nm which provided the dependences of transmission from the wavelength. The results indicate that vegetable fat has noticeable transmission dip around 925 nm and glucose has sufficient dip at 990 nm. Then, after the feasibility check, we did numerical simulation of the heat distribution in bulk using finite elements method. Based on the results, optimal laser wavelength and illuminator configuration were selected. Finally, we carried out several pilot experiments with high-power diodes heating the chosen media.

  2. Laser heating of metallic nanoparticles for photothermal ablation applications

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoming; Shan, Guangshuai; Yu, Junsheng; Yang, Wei; Ren, Zhaodi; Wang, Xiaohui; Xie, Xi; Chen, Hui-jiuan; Chen, Xiaodong

    2017-02-01

    In order to search for a suitable frequency and material with higher photothermal efficacy for hyperthermia application in cancer treatment, a comparative study on laser heating of Au/Ag nanoparticles and Ag nanowires has been conducted. It is found that gold nanoparticles are more photothermal efficient in comparison with silver nanoparticles and silver nanowires at 450nm and 532 nm. Gold nanoparticles are more heated by 532 nm laser than 450 nm laser. In contrast, silver nanoparticles show slightly less temperature rise at 532 nm than 450 nm laser. For silver nanowires, no significant photothermal effect has been observed. Size-dependent effect study indicates that the absorption efficiency of single gold nanoparticles of larger diameter is higher than that of smaller diameter, in the diameter range of 0-50nm. A mathematical model for describing the heating profile in the heating sample has been built. The mathematical model can be utilized to predict the optimal treatment size of tumor.

  3. Simulation study on laser cladding on preplaced powder layer with a tailored laser heat source

    NASA Astrophysics Data System (ADS)

    Tseng, W. C.; Aoh, J. N.

    2013-06-01

    This study proposes a tailored laser heat source model for the finite element analysis of the laser cladding process. The beam characteristics, including wavelength, beam radius, TEM mode and focusing conditions, were comprehensively considered in the heat source model. The model was integrated in a SYSWELD package to predict the temperature distribution and clad bead profile during laser cladding of preplaced cobalt powder layer on a steel substrate. Cladding process parameters were evaluated by varying the TEM mode, focusing conditions, wavelength and scanning speed. Single mode and tailored multi-mode TEMmixed laser beams were established for simulation. The numerical results were verified by performing a laser cladding experiment under the same conditions as the numerical model. The clad bead geometries predicted from the numerical simulation agreed well with those obtained from experiment. Thanks to the comprehensive feature of the proposed tailored laser heat source model, it also could be well applied to the numerical simulation of other laser material processes.

  4. Laser heating of dielectric particles for medical and biological applications.

    PubMed

    Tribelsky, Michael I; Fukumoto, Yasuhide

    2016-07-01

    We consider the general problem of laser pulse heating of a spherical dielectric particle embedded in a liquid. The discussed range of the problem parameters is typical for medical and biological applications. We focus on the case, when the heat diffusivity in the particle is of the same order of magnitude as that in the fluid. We perform quantitative analysis of the heat transfer equation based on interplay of four characteristic scales of the problem, namely the particle radius, the characteristic depth of light absorption in the material of the particle and the two heat diffusion lengths: in the particle and in the embedding liquid. A new quantitative characteristic of the laser action, that is the cooling time, describing the temporal scale of the cooling down of the particle after the laser pulse is over, is introduced and discussed. Simple analytical formulas for the temperature rise in the center of the particle and at its surface as well as for the cooling time are obtained. We show that at the appropriate choice of the problem parameters the cooling time may be by many orders of magnitude larger the laser pulse duration. It makes possible to minimize the undesirable damage of healthy tissues owing to the finite size of the laser beam and scattering of the laser radiation, simultaneously keeping the total hyperthermia period large enough to kill the pathogenic cells. An example of application of the developed approach to optimization of the therapeutic effect at the laser heating of particles for cancer therapy is presented.

  5. Numerical modeling of laser isochoric heating of hot dense matter

    NASA Astrophysics Data System (ADS)

    Sentoku, Yasuhiko

    2005-10-01

    Ultra-intense short-pulse lasers are important tools for creating short-lived high energy plasmas, however to date, it has not been possible to create several hundred eV solid density matter because of the rapid transport of the laser-generated hot electrons throughout the target volume. We proposed a new way to isochorically heat matter at solid density to extreme temperatures by magnetic confinement of laser- generated hot electrons for several picoseconds by application of a multi-MG external field. In advance of an experiment at the Nevada Terawatt Facility (NTF), using a 100 TW- class laser, which will be synchronized to a 1MA Z-pinch machine, we have performed theoretical studies using a collisional particle-in-cell codes PICLS, which is optimized for a study of isochoric heating of solid density plasmas. One of the critical issues of the PIC simulation of the the laser isochoric heating is significant numerical heating, which makes difficult to simulate 100 eV solid density plasmas over picoseconds by PIC. In this talk, we introduce a couple of numerical techniques to extend the grid size with suppressing the numerical heating and also the full relativistic collision model to simulate the isochoric heating by ultra-intense lasers. This work was supported by DOE/NNSA-UNR grant DE-FC52-01NV14050.

  6. Manipulation of heat-diffusion channel in laser thermal lithography.

    PubMed

    Wei, Jingsong; Wang, Yang; Wu, Yiqun

    2014-12-29

    Laser thermal lithography is a good alternative method for forming small pattern feature size by taking advantage of the structural-change threshold effect of thermal lithography materials. In this work, the heat-diffusion channels of laser thermal lithography are first analyzed, and then we propose to manipulate the heat-diffusion channels by inserting thermal conduction layers in between channels. Heat-flow direction can be changed from the in-plane to the out-of-plane of the thermal lithography layer, which causes the size of the structural-change threshold region to become much smaller than the focused laser spot itself; thus, nanoscale marks can be obtained. Samples designated as "glass substrate/thermal conduction layer/thermal lithography layer (100 nm)/thermal conduction layer" are designed and prepared. Chalcogenide phase-change materials are used as thermal lithography layer, and Si is used as thermal conduction layer to manipulate heat-diffusion channels. Laser thermal lithography experiments are conducted on a home-made high-speed rotation direct laser writing setup with 488 nm laser wavelength and 0.90 numerical aperture of converging lens. The writing marks with 50-60 nm size are successfully obtained. The mark size is only about 1/13 of the focused laser spot, which is far smaller than that of the light diffraction limit spot of the direct laser writing setup. This work is useful for nanoscale fabrication and lithography by exploiting the far-field focusing light system.

  7. Heat Transfer and Pressure Drop Data for Circular Cylinders in Ducts and Various Arrangements

    DTIC Science & Technology

    1951-09-01

    cities - and Constant Spacing iii Scinch, Duct - ~-^ - - -r =• -~ - -- - - - - 37;, Single, Cylinder’ and Three- Cylinders in line" with Yard...heating coils surrounded by .a 3/Scinch thicis shell of ^anslte, .an asbest -cs-cemens material; oo’CiSlstljig of 35 per cent Portland cement .and lä per...gradients did, not permit very accurate de-* teraiinationä--&t low flois veio- cities because of ihseösitivity af She fee generalization of the, pressure

  8. Laser production and heating of plasma for MHD application

    NASA Technical Reports Server (NTRS)

    Jalufka, N. W.

    1988-01-01

    Experiments have been made on the production and heating of plasmas by the absorption of laser radiation. These experiments were performed to ascertain the feasibility of using laser-produced or laser-heated plasmas as the input for a magnetohydrodynamic (MHD) generator. Such a system would have a broad application as a laser-to-electricity energy converter for space power transmission. Experiments with a 100-J-pulsed CO2 laser were conducted to investigate the breakdown of argon gas by a high-intensity laser beam, the parameters (electron density and temperature) of the plasma produced, and the formation and propagation of laser-supported detonation (LSD) waves. Experiments were also carried out using a 1-J-pulsed CO2 laser to heat the plasma produced in a shock tube. The shock-tube hydrogen plasma reached electron densities of approximately 10 to the 17th/cu cm and electron temperatures of approximately 1 eV. Absorption of the CO2 laser beam by the plasma was measured, and up to approximately 100 percent absorption was observed. Measurements with a small MHD generator showed that the energy extraction efficiency could be very large with values up to 56 percent being measured.

  9. Study, optimization, and design of a laser heat engine

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Laser heat engine concepts, proposed for satellite applications, were analyzed to determine which engine concepts best meet the requirements of high efficiency (50 percent or better) continuous operation in space. The best laser heat engine for a near-term experimental demonstration, selected on the basis of high overall operating efficiency, high power-to-weight characteristics, and availability of the required technology, is an Otto/Diesel cycle piston engine using a diamond window to admit CO2 laser radiation. The technology with the greatest promise of scaling to megawatt power levels in the long term is the energy exchanger/gas turbine combination.

  10. Thermoluminescence for nonlinear heating profiles with application to laser heated emissions

    SciTech Connect

    Lawless, John L.; Lo, D.

    2001-06-01

    A general formula is found to predict thermoluminescence emission over a wide range of heating profiles. This is particularly useful for rapid laser heating which generates very nonlinear temperature{endash}time profiles. Special cases of the general formula are considered for power-law and logarithmic temperature{endash}time curves. The results compare well to previous CO{sub 2} laser heated thermoluminescence experiments. The agreement between theory and experiment extends over several orders of magnitude change in the heating rate. {copyright} 2001 American Institute of Physics.

  11. Laser beat frequency heating of a rippled density plasma

    NASA Astrophysics Data System (ADS)

    Vijay, A.; Tripathi, V. K.

    2016-09-01

    Two collinear laser beams propagating through a rippled density plasma, with their frequency difference close to plasma frequency, resonantly excite a large amplitude plasma wave. The density ripple of suitable wavenumber slows down the plasma wave very significantly, leading to strong electron heating via the Landau damping of the plasma wave. An analytical framework of the process is developed and the electron temperature scaling with plasma density, laser power and laser frequency have been obtained. Its relevance to recent experiments on intense short pulse laser plasma interaction has been discussed.

  12. Update on Modular Laser Launch System and Heat Exchanger Thruster

    NASA Astrophysics Data System (ADS)

    Kare, Jordin T.

    2011-11-01

    The heat-exchanger (HX) thruster and modular laser array provide a comparatively low-risk route to a ground-to-orbit laser launch system. Recently, the reference designs for the propulsion system, laser array, and overall launch system have evolved significantly. By combining a variable flow of dense propellant with the primary hydrogen propellant, the heat exchanger thruster can trade reduced Isp for increased thrust at liftoff, with minimal increase in tank mass. Single-mode CW fiber lasers up to 10 kW power allow a beam module to be built with off-the-shelf commercial lasers. Low-cost high-radiance laser diode arrays can deliver launch-level fluxes of 5-10 MW/m2 over tens of kilometers, sufficient to power a vehicle through the atmosphere, and high enough to hand off propulsion to a main laser array several hundred kilometers downrange. These and other enhancements enable a system design with a true single-stage vehicle in which the only component not yet demonstrated is the silicon-carbide heat exchanger itself.

  13. Tissue Heating With A Pulsed Nd-YAG Laser

    NASA Astrophysics Data System (ADS)

    Grossweiner, Leonard I.; Al-Karmi, Anan M.

    1988-06-01

    Neodymium-yttrium aluminum garnet (Nd-YAG) lasers are finding increasing appli-cations in laser surgery of vascular tissues because of their good hemostatic properties. Heat penetration is deeper than the carbon dioxide laser, because the 1064 nm Nd-YAG emission is located in a "window" between the strong absorptions of oxyhemoglobin and tissue water. The basic physics of laser-tissue interactions suggests that damage to peripheral tissues can be confined by using sufficiently short pulses. In continuous mode (CW) operation, heat flow driven by temperature gradients leads to tissue heating external to the optical absorption profile. When the energy is delivered in pulses, however, conductive heat flow is minimized if the pulse duration (tn) is shorter than the thermal relaxation time constant (t ). Pulsed operation should be especially useful for the Nd-YAG laser, where the 1/e optical penetration depth (5) at 1064 nm is the order of 0.3 to 0.5 cm. Taking t" =2/2a, where a is the thermal diffusivity (the order of 0.001 cm2/s for tissues), typical values of t* for heat conduction are the order of 1-2 min. Heat removal by blood flow augments thermal conduction in vascularized tissues. The rate of this process is characterized by 1/Q, where Q is the volume blood perfusion rate. Values 1/Q range from the order of 15 s for human kidney and thyroid to more than 15 min for muscle.1 Accordingly, heat removal by conduction and blood flow during the pulse duration can be neglected for many tissues exposed to Nd-YAG laser pulses. This paper describes an analytical solution to the two dimensional laser bioheat equation applicable to pulsed operation. The theory was applied to measur-ements on potato tuber heated by low-power pulses from a clinical Nd-YAG laser. The initial temperature elevations are in satisfactory agreement with the analysis, but thermal relaxation was faster than predicted. The suggested explanation for the discrepancy involves evaporative heat transfer to

  14. Laser three-dimensional printing microchannel heat sink for high-power diode laser array

    NASA Astrophysics Data System (ADS)

    Jia, Guannan; Qiu, Yuntao; Yan, Anru; Yao, Shun; Wang, Zhiyong

    2016-09-01

    To improve the heat management of high-power diode lasers, a microchannel heat sink is obtained, whose structure is optimized in method of numerical simulation. Following such a design, the microchannel heat sink is fabricated by nickel-based doping rare earth materials by laser three-dimensional (3-D) printing procedure. Since the noncorrosion property of such material has been preliminarily demonstrated by salt spray test, there is no necessity to plate the interior of the laser 3-D printing microchannel heat sink with gold. The coefficient of thermal expansion of such material is 11 ppm/K. The diode laser array (LDA) with 80-W cw output power, 2-mm cavity length, 100-μm emitter width, and 20% fill-factors is mounted on it for the thermal resistance test, and the result is 0.40 K/W. Moreover, the smile effect of the mounted LDA is merely 0.8 μm.

  15. Surface heat transfer coefficient, heat efficiency, and temperature of pulsed solid-state lasers

    SciTech Connect

    Mann, K.; Weber, H.

    1988-08-01

    The temperature of solid-state lasers is a critical parameter. Efficiency and output power are strongly influenced by it. The two parameters which determine the temperature are the heat generation efficiency (HGE) and the surface heat transfer coefficient (SHTC) of the laser rod. These parameters allow the scaling of the rod temperature up to high pumping powers. Moreover, from the temperature inside the rod, the temperature gradients and the mechanical stress can be evaluated. Using transient temperature measurements, the SHTC and the HGE were determined for air- and water-cooled Nd:YAG and alexandrite lasers. The SHTC can be confirmed by theoretical considerations.

  16. Heating of blood vessels exposed to laser light

    NASA Astrophysics Data System (ADS)

    Astafyeva, Liudmila G.; Zheltov, Georgy; Schmidt, Wolf-Dieter

    2003-10-01

    An advanced model of blood vessel heating by laser radiation is proposed for tasks of laser skin surgery and therapy. Blood vessel is modeled by infinite circular cylinder situated in skin dermis. Heat conduction equation taking into account the inhomogeneous internal source function is calculated. The source function inside the blood vessel is calculated according to the theory of diffraction of electromagnetic radiation on infinite circular cylinder. Dynamics of the temperature fields inside the vessels as a function of vessel diameters and duration of irradiance is calculated for the wavelength of 0.532 μm. It is determined the irradiance conditions whereby the near-homogeneous heating along the perimeter of walls of blood vessels on minimum laser exposure to surrounding tissues is achieved.

  17. Near-Term Laser Launch Capability: The Heat Exchanger Thruster

    NASA Astrophysics Data System (ADS)

    Kare, Jordin T.

    2003-05-01

    The heat exchanger (HX) thruster concept uses a lightweight (up to 1 MW/kg) flat-plate heat exchanger to couple laser energy into flowing hydrogen. Hot gas is exhausted via a conventional nozzle to generate thrust. The HX thruster has several advantages over ablative thrusters, including high efficiency, design flexibility, and operation with any type of laser. Operating the heat exchanger at a modest exhaust temperature, nominally 1000 C, allows it to be fabricated cheaply, while providing sufficient specific impulse (~600 seconds) for a single-stage vehicle to reach orbit with a useful payload; a nominal vehicle design is described. The HX thruster is also comparatively easy to develop and test, and offers an extremely promising route to near-term demonstration of laser launch.

  18. Laser heating of dielectric particles for medical and biological applications

    PubMed Central

    Tribelsky, Michael I.

    2016-01-01

    We consider the general problem of laser pulse heating of a spherical dielectric particle embedded in a liquid. The discussed range of the problem parameters is typical for medical and biological applications. We focus on the case, when the heat diffusivity in the particle is of the same order of magnitude as that in the fluid. We perform quantitative analysis of the heat transfer equation based on interplay of four characteristic scales of the problem, namely the particle radius, the characteristic depth of light absorption in the material of the particle and the two heat diffusion lengths: in the particle and in the embedding liquid. A new quantitative characteristic of the laser action, that is the cooling time, describing the temporal scale of the cooling down of the particle after the laser pulse is over, is introduced and discussed. Simple analytical formulas for the temperature rise in the center of the particle and at its surface as well as for the cooling time are obtained. We show that at the appropriate choice of the problem parameters the cooling time may be by many orders of magnitude larger the laser pulse duration. It makes possible to minimize the undesirable damage of healthy tissues owing to the finite size of the laser beam and scattering of the laser radiation, simultaneously keeping the total hyperthermia period large enough to kill the pathogenic cells. An example of application of the developed approach to optimization of the therapeutic effect at the laser heating of particles for cancer therapy is presented. PMID:27446706

  19. Laser-heated X-ray flashlamp brightness measurements

    SciTech Connect

    Matthews, D.L.; Campbell, E.M.; Hagelstein, P.; Halsey, W.; Kauffman, R.L.; Koppel, L.; Phillion, D.; Price, R.; Toor, A.

    1983-12-01

    The authors present measurements of the X-ray emission characteristics of laser-irradiated flashlamp foils which are candidates to produce by resonant photoexcitation a population inversion in either a neon or fluorine lasant gas. Using the Shiva 1.06 ..mu.. laser, the authors heated Fe, Cr, and Ni foils to study the brightness and centroid energies of X-ray lines stemming from L-M transitions. Results indicate that appropriately bright and uniform sources can be produced.

  20. Experimental study on EHD heat transfer enhancement from flush-mounted ribbons with different arrangements of wire electrodes in a channel

    NASA Astrophysics Data System (ADS)

    Alami nia, Amin; Campo, Antonio

    2016-12-01

    In the present study, the heat transfer enhancement of a bundle of flush-mounted ribbons placed on the floor of a rectangular duct was investigated experimentally. The flush-mounted ribbons act as heat sources and the cooling happens with air. The air flow was three-dimensional, steady, viscous and incompressible under both laminar and turbulent conditions (500 ≤ {Re}_{{Dh }} ≤ 4500). The hydrodynamics and heat transfer behavior of the air flow was studied by means of an active method with application of corona wind. The state of the art of this work revolves around an experimental investigation of an electrohydrodynamics (EHD) active method and heat transfer enhancement from the surfaces of the flush-mounted ribbons. Due to the intricacies of the required experiment, a special apparatus needed to be designed and constructed. The aim of this work is application of EHD active method for convective heat transfer enhancement. In this method the different arrangement of wire electrodes has been achieved. The results show that in same Reynolds numbers and voltages of wires, the heat transfer enhancement was increase in arrangement 1 than other 4 arrangements.

  1. Laser-heating wire bonding on MEMS packaging

    NASA Astrophysics Data System (ADS)

    Liu, Yuetao; Sun, Lining

    2014-03-01

    Making connections is critical in fabrication of MEMS (Micro-Electro-Mechanical Systems). It is also complicated, because the temperature during joining affects both the bond produced and the structure and mechanical properties of the moving parts of the device. Specifications for MEMS packaging require that the temperature not exceed 240 °C. However, usually, temperatures can reach up to 300 °C during conventional thermosonic wire bonding. Such a temperature will change the distribution of dopants in CMOS (Complementary Metal Oxide Semiconductor) circuits. In this paper we propose a new heating process. A semiconductor laser (wavelength 808 nm) is suggested as the thermal source for wire bonding. The thermal field of this setup was analyzed, and specific mathematical models of the field were built. Experimental results show that the heating can be focused on the bonding pad, and that much lower heat conduction occurs, compared with that during the normal heating method. The bond strength increases with increasing laser power. The bond strengths obtained with laser heating are slightly lower than those obtained with the normal heating method, but can still meet the strength requirements for MEMS.

  2. Advanced Flat Top Laser Heating System for High Pressure Research

    NASA Astrophysics Data System (ADS)

    Prakapenka, V.; Kantor, I.; Kuznetsov, A.; Dera, P. K.; Rivers, M. L.; Sutton, S. R.

    2009-12-01

    Double-sided laser heating combined with synchrotron x-ray radiation for in-situ studies in the DAC using diffraction, emission and inelastic scattering methods has been the most productive and widely used high temperature-high pressure technique in past two decades. Equation of state, phase transformations, element partitioning, electronic and optical properties of various materials have been successfully studied at conditions relevant to the Earth’s interior with help of lasers. High temperature data collected in the DAC are mostly consistent, however, there are some discrepancies in reported results among high pressure research groups performing experiments at different facilities, particularly for determinations of melting temperatures, Clapeyron slopes, elastic constants, and thermal expansion coefficients. Although differences in the samples themselves cannot be ruled out, an important contributor to inconsistent results is related to temperature non-uniformity in the analyzed volume. Here we report a new development in on-line, double-sided, laser heating systems based on diode pumped fiber lasers coupled with beam-shaping optics that allows control of the shape of the focused laser beam spot on the sample surface in the DAC with variable diameter from 8 to 40 μm. Varying the settings of the laser heating system, we were able to shape the beam to almost any desired intensity profile and size on the surface of the sample in the DAC including tight focus, flat top, trident and doughnut types. The significant advantages and excellent performance of the flat top laser heating (FTLH) technique will be demonstrated in melting experiments on germanium and iron compounds. During FT laser heating the molten sample doesn’t escape from the homogeneously heated area as is usually observed for Gaussian or doughnut type laser spots in the DAC. The capability to maintain the molten sample in the DAC for a relatively long time (at least 60 s) allowed us to collect high

  3. Radiative heat transport instability in a laser produced inhomogeneous plasma

    SciTech Connect

    Bychenkov, V. Yu.; Rozmus, W.

    2015-08-15

    A laser produced high-Z plasma in which an energy balance is achieved due to radiation emission and radiative heat transfer supports ion acoustic instability. A linear dispersion relation is derived, and instability is compared to the radiation cooling instability [R. G. Evans, Plasma Phys. Controlled Fusion 27, 751 (1985)]. Under conditions of indirect drive fusion experiments, the driving term for the instability is the radiative heat flux and, in particular, the density dependence of the radiative heat conductivity. A specific example of thermal Bremsstrahlung radiation source has been considered. This instability may lead to plasma jet formation and anisotropic x-ray generation, thus affecting inertial confinement fusion related experiments.

  4. How to detect melting in laser heating diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Liuxiang, Yang

    2016-07-01

    Research on the melting phenomenon is the most challenging work in the high pressure/temperature field. Until now, large discrepancies still exist in the melting curve of iron, the most interesting and extensively studied element in geoscience research. Here we present a summary about techniques detecting melting in the laser heating diamond anvil cell.

  5. Laser-heating-based active optics for synchrotron radiation applications.

    PubMed

    Yang, Fugui; Li, Ming; Gao, Lidan; Sheng, Weifan; Liu, Peng; Zhang, Xiaowei

    2016-06-15

    Active optics has attracted considerable interest from researchers in synchrotron radiation facilities because of its capacity for x-ray wavefront correction. Here, we report a novel and efficient technique for correcting or modulating a mirror surface profile based on laser-heating-induced thermal expansion. An experimental study of the characteristics of the surface thermal deformation response indicates that the power of a milliwatt laser yields a bump height as low as the subnanometer scale and that the variation of the spot size modulates the response function width effectively. In addition, the capacity of the laser-heating technique for free-form surface modulation is demonstrated via a one-dimensional surface correction experiment. The developed method is a promising new approach toward effective x-ray active optics coupled with at-wavelength metrology techniques.

  6. Modeling thermionic emission from laser-heated nanoparticles

    SciTech Connect

    Mitrani, J. M.; Shneider, M. N.; Stratton, B. C.; Raitses, Y.

    2016-02-01

    An adjusted form of thermionic emission is applied to calculate emitted current from laser-heated nanoparticles and to interpret time-resolved laser-induced incandescence (TR-LII) signals. This adjusted form of thermionic emission predicts significantly lower values of emitted current compared to the commonly used Richardson-Dushman equation, since the buildup of positive charge in a laser-heated nanoparticle increases the energy barrier for further emission of electrons. Thermionic emission influences the particle's energy balance equation, which can influence TR-LII signals. Additionally, reports suggest that thermionic emission can induce disintegration of nanoparticle aggregates when the electrostatic Coulomb repulsion energy between two positively charged primary particles is greater than the van der Waals bond energy. Furthermore, since the presence and size of aggregates strongly influences the particle's energy balance equation, using an appropriate form of thermionic emission to calculate emitted current may improve interpretation of TR-LII signals.

  7. Modeling thermionic emission from laser-heated nanoparticles

    DOE PAGES

    Mitrani, J. M.; Shneider, M. N.; Stratton, B. C.; ...

    2016-02-01

    An adjusted form of thermionic emission is applied to calculate emitted current from laser-heated nanoparticles and to interpret time-resolved laser-induced incandescence (TR-LII) signals. This adjusted form of thermionic emission predicts significantly lower values of emitted current compared to the commonly used Richardson-Dushman equation, since the buildup of positive charge in a laser-heated nanoparticle increases the energy barrier for further emission of electrons. Thermionic emission influences the particle's energy balance equation, which can influence TR-LII signals. Additionally, reports suggest that thermionic emission can induce disintegration of nanoparticle aggregates when the electrostatic Coulomb repulsion energy between two positively charged primary particles ismore » greater than the van der Waals bond energy. Furthermore, since the presence and size of aggregates strongly influences the particle's energy balance equation, using an appropriate form of thermionic emission to calculate emitted current may improve interpretation of TR-LII signals.« less

  8. Single cell viability and impact of heating by laser absorption.

    PubMed

    Wetzel, Franziska; Rönicke, Susanne; Müller, Karla; Gyger, Markus; Rose, Daniel; Zink, Mareike; Käs, Josef

    2011-09-01

    Optical traps such as tweezers and stretchers are widely used to probe the mechanical properties of cells. Beyond their large range of applications, the use of infrared laser light in optical traps causes significant heating effects in the cell. This study investigated the effect of laser-induced heating on cell viability. Common viability assays are not very sensitive to damages caused in short periods of time or are not practicable for single cell analysis. We used cell spreading, a vital ability of cells, as a new sensitive viability marker. The optical stretcher, a two beam laser trap, was used to simulate heat shocks that cells typically experience during measurements in optical traps. The results show that about 60% of the cells survived heat shocks without vital damage at temperatures of up to 58 ± 2°C for 0.5 s. By varying the duration of the heat shocks, it was shown that 60% of the cells stayed viable when exposed to 48 ± 2°C for 5 s.

  9. Sub-second laser heating of thermal impulse sensors

    NASA Astrophysics Data System (ADS)

    Gunawidjaja, Ray; Anderson, Benjamin R.; Price, Patrick; Diez-y-Riega, Helena; Eilers, Hergen

    2017-01-01

    We have developed thermal impulse sensors to measure and record temperature and heating duration in explosive fireballs. The functionality of these sensors is similar to that of our temperature-only sensors - rare-earth ions are used to monitor temperature-induced phase changes. However, in this case two sensor materials, p-Dy:Y2O3 and p-Eu:ZrO2, with different phase change kinetics are mixed. In addition, a fluorescence standard, Ho:ZrO2, is included. Also, using laser heating, we have now reduced the shortest heating duration for our calibration measurements from the previously reported 2 s to 100 ms, and we have evaluated these sensors for temperatures between 400 °C and 900 °C, and heating times between 100 ms and 1000 ms. Using spectral matching, we determine the temperature and heating duration.

  10. Heating model for metals irradiated by a subpicosecond laser pulse

    SciTech Connect

    Chimier, B.; Tikhonchuk, V. T.; Hallo, L.

    2007-05-15

    We propose a model describing the heating and ablation of a metallic target irradiated by a subpicosecond laser pulse. It takes into account the temperature equilibration between the electrons and ions and the density variation of the target material during the heating process. A simple analytical equation of state is developed, which allows one to calculate the total pressure in the heated layer for different electron and ion temperatures. The thermodynamic behavior of a nonequilibrium system is discussed, and nonequilibrium spinodals and cohesion limits are introduced. The model is applied for a description of the thermal ablation process driven by a sub-ps laser pulse. Aluminum and copper targets are considered, and it is shown that the dominant ablation process is due to breaking the nonequilibrium cohesion limit. The numerical results are in good agreement with recent experimental data.

  11. Laser-induced incandescence from laser-heated silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Menser, Jan; Daun, Kyle; Dreier, Thomas; Schulz, Christof

    2016-11-01

    This work describes the application of temporally and spectrally resolved laser-induced incandescence to silicon nanoparticles synthesized in a microwave plasma reactor. Optical properties for bulk silicon presented in the literature were extended for nanostructured particles analyzed in this paper. Uncertainties of parameters in the evaporation submodel, as well as measurement noise, are incorporated into the inference process by Bayesian statistics. The inferred nanoparticle sizes agree with results from transmission electron microscopy, and the determined accommodation coefficient matches the values of the preceding study.

  12. Review of controlled fusion research using laser heating.

    NASA Technical Reports Server (NTRS)

    Hertzberg, A.

    1973-01-01

    Development of methods for generating high laser pulse energy has stimulated research leading to new ideas for practical controlled thermonuclear fusion machines. A review is presented of some important efforts in progress, and two different approaches have been selected as examples for discussion. One involves the concept of very short pulse lasers with power output tailored, in time, to obtain a nearly isentropic compression of a deuterium-tritium pellet to very high densities and temperatures. A second approach utilizing long wavelength, long pulse, efficient gas lasers to heat a column of plasma contained in a solenoidal field is also discussed. The working requirements of the laser and various magnetic field geometries of this approach are described.

  13. Simulation of planetary entry radiative heating with a CO2 gasdynamic laser

    NASA Technical Reports Server (NTRS)

    Lundell, J. H.; Dickey, R. R.; Howe, J. T.

    1975-01-01

    Heating encountered during entry into the atmospheres of Jupiter, Saturn, and Uranus is described, followed by a discussion of the use of a CO2 gasdynamic laser to simulate the radiative component of the heating. Operation and performance of the laser is briefly described. Finally, results of laser tests of some candidate heat-shield materials are presented.

  14. Simulation of planetary entry radiative heating with a CO2 gasdynamic laser

    NASA Technical Reports Server (NTRS)

    Lundell, J. H.; Dickey, R. R.; Howe, J. T.

    1975-01-01

    Heating encountered during entry into the atmospheres of Jupiter, Saturn, and Uranus is described, followed by a discussion of the use of a CO2 gasdynamic laser to simulate the radiative component of the heating. Operation and performance of the laser is briefly described. Finally, results of laser tests of some candidate heat-shield materials are presented.

  15. Plasma column development in the CO2 laser-heated solenoid

    NASA Astrophysics Data System (ADS)

    Tighe, W.; Offenberger, A. A.; Capjack, C. E.

    1987-08-01

    Axial and radial plasma dynamics in the CO2 laser-heated solenoid have been studied experimentally and numerically. The axial behavior is found to be well described by a self-regulated bleaching wave model. The radial expansion is found to be strongly dependent on the focusing ratio of the input laser beam. With a fast focus ( f/5), the early radial expansion rate is twice that found with a slower focusing arrangement ( f/15). The faster focusing ratio also results in a significantly wider plasma column. On the other hand, no significant dependence of f/♯ on the axial propagation was found. A finite ionization time and the rapid formation of a density minimum on axis are observed and verify earlier experimental results. Detailed comparisons are made with a 2-D magnetohydrodynamic (MHD) and laser propagation code. The axial and radial plasma behavior and, in particular, the dependence of the radial behavior on the focal ratio of the laser are reasonably well supported by the simulation results. Computational results are also in good agreement with experimental measurements of temperature and density using stimulated scattering (Brillouin, Raman) and interferometry diagnostic techniques.

  16. Bio-heat transfer simulation of retinal laser irradiation.

    PubMed

    Narasimhan, Arunn; Jha, Kaushal Kumar

    2012-05-01

    Retinopathy is a surgical process in which maladies of the human eye are treated by laser irradiation. A two-dimensional numerical model of the human eye geometry has been developed to investigate transient thermal effects due to laser radiation. In particular, the influence of choroidal pigmentation and that of choroidal blood convection-parameterized as a function of choroidal blood perfusion-are investigated in detail. The Pennes bio-heat transfer equation is invoked as the governing equation, and finite volume formulation is employed in the numerical method. For a 500-μm diameter spot size, laser power of 0.2 W, and 100% absorption of laser radiation in the retinal pigmented epithelium (RPE) region, the peak RPE temperature is observed to be 103 °C at 100 ms of the transient simulation of the laser surgical period. Because of the participation of pigmented layer of choroid in laser absorption, peak temperature is reduced to 94 °C after 100 ms of the laser surgery period. The effect of choroidal blood perfusion on retinal cooling is found to be negligible during transient simulation of retinopathy. A truncated three-dimensional model incorporating multiple laser irradiation of spots is also developed to observe the spatial effect of choroidal blood perfusion and choroidal pigmentation. For a circular array of seven uniformly distributed spots of identical diameter and laser power of 0.2 W, transient temperature evolution using simultaneous and sequential mode of laser surgical process is presented with analysis.

  17. Plasma Heating and Ultrafast Semiconductor Laser Modulation Through a Terahertz Heating Field

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Ning, C. Z.

    2000-01-01

    Electron-hole plasma heating and ultrafast modulation in a semiconductor laser under a terahertz electrical field are investigated using a set of hydrodynamic equations derived from the semiconductor Bloch equations. The self-consistent treatment of lasing and heating processes leads to the prediction of a strong saturation and degradation of modulation depth even at moderate terahertz field intensity. This saturation places a severe limit to bandwidth achievable with such scheme in ultrafast modulation. Strategies for increasing modulation depth are discussed.

  18. Hyperbolic Heat Conduction In Pulsed Laser Irradiation Of Tissue

    NASA Astrophysics Data System (ADS)

    Rastegar, Sohi

    1989-08-01

    The use of lasers for ablation of biological tissues is becoming common place in many medical and surgical applications. However, the complete nature of the ablation mechanism is yet to be understood. Many authors have contributed to the theoretical understanding and modeling of the thermodynamics of ablation process by a laser. Some examples are [LANGERHOLC,1979; VAN GEMERT et al., 1985; ARMON and LAUFER, 1986; MCKENZIE, 1986; PARTOVI et al., 1987; RASTEGAR et al., 1988]. In a previous theoretical work the effect of optical properties on the ablation process has been shown [RASTEGAR et al., 19881)]. The effect of variation of power and exposure time over a constant fluence delivered on the tissue volume removed and the damage incurred on the surrounding tissue is shown in figure 1 [ RASTEGAR et al., 1988a]. This shows that for a given fluence, as power is increased and exposure duration is decreased the change on the volume removed is not significant while the damage to the surrounding tissue is significantly lessened. However these results, and those of the above references, are based on Fourier's law of heat conduction which is valid for relatively low power CW laser irradiation. The interaction of short pulsed high power lasers with tissues manifests a different behavior and application of Fourier's heat conduction law becomes questionable. In particular, in some experimental observations application of pulsed lasers has shown no apparent thermal damage to the surrounding tissue.

  19. High temperature thermographic measurements of laser heated silica

    SciTech Connect

    Elhadj, S; Yang, S T; Matthews, M J; Cooke, D J; Bude, J D; Johnson, M; Feit, M; Draggoo, V; Bisson, S E

    2009-11-02

    In situ spatial and temporal surface temperature profiles of CO{sub 2} laser-heated silica were obtained using a long wave infrared (LWIR) HgCdTe camera. Solutions to the linear diffusion equation with volumetric and surface heating are shown to describe the temperature evolution for a range of beam powers, over which the peak surface temperature scales linearly with power. These solutions were used with on-axis steady state and transient experimental temperatures to extract thermal diffusivity and conductivity for a variety of materials, including silica, spinel, sapphire, and lithium fluoride. Experimentally-derived thermal properties agreed well with reported values and, for silica, thermal conductivity and diffusivity are shown to be approximately independent of temperature between 300 and 2800K. While for silica our analysis based on a temperature independent thermal conductivity is shown to be accurate, for other materials studied this treatment yields effective thermal properties that represent reasonable approximations for laser heating. Implementation of a single-wavelength radiation measurement in the semi-transparent regime is generally discussed, and estimates of the apparent temperature deviation from the actual outer surface temperature are also presented. The experimental approach and the simple analysis presented yield surface temperature measurements that can be used to validate more complex physical models, help discriminate dominant heat transport mechanisms, and to predict temperature distribution and evolution during laser-based material processing.

  20. High temperature thermographic measurements of laser heated silica

    NASA Astrophysics Data System (ADS)

    Elhadj, Selim; Yang, Steven T.; Matthews, Manyalibo J.; Cooke, Diane J.; Bude, Jeffrey D.; Johnson, Michael; Feit, Michael; Draggoo, Vaughn; Bisson, Scott E.

    2009-10-01

    In situ spatial and temporal surface temperature profiles of CO2 laser-heated silica were obtained using a long wave infrared (LWIR) HgCdTe camera. Solutions to the linear diffusion equation with volumetric and surface heating are shown to describe the temperature evolution for a range of beam powers, over which the peak surface temperature scales linearly with power. These solutions were used with on-axis steady state and transient experimental temperatures to extract thermal diffusivity and conductivity for a variety of materials, including silica, spinel, sapphire, and lithium fluoride. Experimentally-derived thermal properties agreed well with reported values and, for silica, thermal conductivity and diffusivity are shown to be approximately independent of temperature between 300 and 2800K. While for silica our analysis based on a temperature independent thermal conductivity is shown to be accurate, for other materials studied this treatment yields effective thermal properties that represent reasonable approximations for laser heating. Implementation of a single-wavelength radiation measurement in the semi-transparent regime is generally discussed, and estimates of the apparent temperature deviation from the actual outer surface temperature are also presented. The experimental approach and the simple analysis presented yield surface temperature measurements that can be used to validate more complex physical models, help discriminate dominant heat transport mechanisms, and to predict temperature distribution and evolution during laser-based material processing.

  1. High power laser heating of low absorption materials

    SciTech Connect

    Olson, K.; Talghader, J.; Ogloza, A.; Thomas, J.

    2014-09-28

    A model is presented and confirmed experimentally that explains the anomalous behavior observed in continuous wave (CW) excitation of thermally isolated optics. Distributed Bragg Reflector (DBR) high reflective optical thin film coatings of HfO₂ and SiO₂were prepared with a very low absorption, about 7 ppm, measured by photothermal common-path interferometry. When illuminated with a 17 kW CW laser for 30 s, the coatings survived peak irradiances of 13 MW/cm², on 500 μm diameter spot cross sections. The temperature profile of the optical surfaces was measured using a calibrated thermal imaging camera for illuminated spot sizes ranging from 500 μm to 5 mm; about the same peak temperatures were recorded regardless of spot size. This phenomenon is explained by solving the heat equation for an optic of finite dimensions and taking into account the non-idealities of the experiment. An analytical result is also derived showing the relationship between millisecond pulse to CW laser operation where (1) the heating is proportional to the laser irradiance (W/m²) for millisecond pulses, (2) the heating is proportional to the beam radius (W/m) for CW, and (3) the heating is proportional to W/m∙ tan⁻¹(√(t)/m) in the transition region between the two.

  2. A numerical study of the supercritical CO2 plate heat exchanger subject to U-type, Z-type, and multi-pass arrangements

    NASA Astrophysics Data System (ADS)

    Zhu, Chen-Xi; Wang, Chi-Chuan

    2017-07-01

    This study proposes a numerical model for plate heat exchanger that is capable of handling supercritical CO2 fluid. The plate heat exchangers under investigation include Z-type (1-pass), U-type (1-pass), and 1-2 pass configurations. The plate spacing is 2.9 mm with a plate thickness of 0.8 mm, and the size of the plate is 600 mm wide and 218 mm in height with 60 degrees chevron angle. The proposed model takes into account the influence of gigantic change of CO2 properties. The simulation is first compared with some existing data for water-to-water plate heat exchangers with good agreements. The flow distribution, pressure drop, and heat transfer performance subject to the supercritical CO2 in plate heat exchangers are then investigated. It is found that the flow velocity increases consecutively from the entrance plate toward the last plate for the Z-type arrangement, and this is applicable for either water side or CO2 side. However, the flow distribution of the U-type arrangement in the water side shows opposite trend. Conversely, the flow distribution for U-type arrangement of CO2 depends on the specific flow ratio (C*). A lower C* like 0.1 may reverse the distribution, i.e. the flow velocity increases moderately alongside the plate channel like Z-type while a large C* of 1 would resemble the typical distribution in water channel. The flow distribution of CO2 side at the first and last plate shows a pronounced drop/surge phenomenon while the channels in water side does not reveal this kind of behavior. The performance of 2-pass plate heat exchanger, in terms of heat transfer rate, is better than that of 1-pass design only when C* is comparatively small (C* < 0.5). Multi-pass design is more effective when the dominant thermal resistance falls in the CO2 side.

  3. Space and Time Resolved Measurements of the Heating of Solids to Ten Million Kelvin by a Petawatt Laser

    SciTech Connect

    Nakatsutsumi, M.; Davies, J.R.; Kodama, R.; Green, J.S.; Lancaster, K.L.; Akli, K.U.; Beg, F.N.; Chen, S.N.; Clark, D.; Freeman, R.R.; Gregory, C.D.; Habara, H.; Heathcote, R.; Hey, D.S.; Highbarger, K.; Jaanimagi, P.; Key, M.H.; Krushelnick, K.; Ma, T.; MacPhee, A.; MacKinnon, A.J.; Nakamura, H.; Stephens, R.B.; Storm, M.; Tampo, M.; Theobald, W.; Van Woerkom, L.; Weber, R.L.; Wei, M.S.; Woolsey, N.C.; Norreys, P.A.

    2008-04-29

    The heating of plane solid targets by the Vulcan petawatt laser at powers of 0.32-0.73 PW and intensities of up to 4 x 10^20 W cm^-2 has been diagnosed with a temporal resolution of 17 ps and a spatial resolution of 30 um, by measuring optical emission from the opposite side of the target to the laser with a streak camera. Second harmonic emission was filtered out and the target viewed at an angle to eliminate optical transition radiation. Spatial resolution was obtained by imaging the emission onto a bundle of fibre optics, arranged into a one-dimensional array at the camera entrance. The results show that a region 160 um in diameter can be heated to a temperature of ~10^7 K (kT/e ~ keV) in solid targets from 10 to 20 um thick and that this temperature is maintained for at least 20 ps, confirming the utility of PW lasers in the study of high energy density physics. Hybrid code modelling shows that magnetic field generation prevents increased target heating by electron refluxing above a certain target thickness and that the absorption of laser energy into electrons entering the solid target was between 15-30%, and tends to increase with laser energy.

  4. Laser heating of aqueous samples on a micro-optical-electro-mechanical system

    DOEpatents

    Beer, Neil Reginald; Kennedy, Ian

    2013-12-17

    A system of heating a sample on a microchip includes the steps of providing a microchannel flow channel in the microchip; positioning the sample within the microchannel flow channel, providing a laser that directs a laser beam onto the sample for heating the sample; providing the microchannel flow channel with a wall section that receives the laser beam and enables the laser beam to pass through wall section of the microchannel flow channel without being appreciably heated by the laser beam; and providing a carrier fluid in the microchannel flow channel that moves the sample in the microchannel flow channel wherein the carrier fluid is not appreciably heated by the laser beam.

  5. Laser heating of aqueous samples on a micro-optical-electro-mechanical system

    DOEpatents

    Beer, Neil Reginald; Kennedy, Ian

    2013-12-17

    A system of heating a sample on a microchip includes the steps of providing a microchannel flow channel in the microchip; positioning the sample within the microchannel flow channel, providing a laser that directs a laser beam onto the sample for heating the sample; providing the microchannel flow channel with a wall section that receives the laser beam and enables the laser beam to pass through wall section of the microchannel flow channel without being appreciably heated by the laser beam; and providing a carrier fluid in the microchannel flow channel that moves the sample in the microchannel flow channel wherein the carrier fluid is not appreciably heated by the laser beam.

  6. Laser heating of aqueous samples on a micro-optical-electro-mechanical system

    DOEpatents

    Beer, Neil Reginald; Kennedy, Ian

    2013-02-05

    A system of heating a sample on a microchip includes the steps of providing a microchannel flow channel in the microchip; positioning the sample within the microchannel flow channel, providing a laser that directs a laser beam onto the sample for heating the sample; providing the microchannel flow channel with a wall section that receives the laser beam and enables the laser beam to pass through wall section of the microchannel flow channel without being appreciably heated by the laser beam; and providing a carrier fluid in the microchannel flow channel that moves the sample in the microchannel flow channel wherein the carrier fluid is not appreciably heated by the laser beam.

  7. Calibrated Heat Flow Model for Determining the Heat Conduction Losses in Laser Cutting of CFRP

    NASA Astrophysics Data System (ADS)

    Mucha, P.; Weber, R.; Speker, N.; Berger, P.; Sommer, B.; Graf, T.

    Laser machining has great potential regarding automation in fabrication of CFRP (carbon-fiber-reinforced plastics) parts, due to the nearly force and tool-wear free processing at high process speeds. The high vaporization temperatures and the large heat conductivity of the carbon fibers lead to a large heat transport into the sample. This causes the formation of a heat-affected zone and a decrease of the process speed. In the present paper,an analytical heat flow model was adapted in order to understand and investigate the heat conduction losses. Thermal sensors were embedded in samples at different distances from the kerf to fit the calculated to the measured temperatures. Heat conduction losses of up to 30% of the laser power were determined. Furthermore, the energy not absorbed by the sample, the energy for sublimating the composite material in the kerf, the energy for the formation of the HAZ, and the residual heat in the sample are compared in an energy balance.

  8. Convection flows driven by laser heating of a liquid layer

    NASA Astrophysics Data System (ADS)

    Rivière, David; Selva, Bertrand; Chraibi, Hamza; Delabre, Ulysse; Delville, Jean-Pierre

    2016-02-01

    When a fluid is heated by the absorption of a continuous laser wave, the fluid density decreases in the heated area. This induces a pressure gradient that generates internal motion of the fluid. Due to mass conservation, convection eddies emerge in the sample. To investigate these laser-driven bulk flows at the microscopic scale, we built a setup to perform temperature measurements with a fluorescent-sensitive dye on the one hand, and measured the flow pattern at different beam powers, using a particle image velocimetry technique on the other hand. Temperature measurements were also used in numerical simulations in order to compare predictions to the experimental velocity profiles. The combination of our numerical and experimental approaches allows a detailed description of the convection flows induced by the absorption of light, which reveals a transition between a thin and a thick liquid layer regime. This supports the basis of optothermal approaches for microfluidic applications.

  9. Nanoscale heating of laser irradiated single gold nanoparticles in liquid.

    PubMed

    Honda, Mitsuhiro; Saito, Yuika; Smith, Nicholas I; Fujita, Katsumasa; Kawata, Satoshi

    2011-06-20

    Biological applications where nanoparticles are used in a cell environment with laser irradiation are rapidly emerging. Investigation of the localized heating effect due to the laser irradiation on the particle is required to preclude unintended thermal effects. While bulk temperature rise can be determined using macroscale measurement methods, observation of the actual temperature within the nanoscale domain around the particle is difficult and here we propose a method to measure the local temperature around a single gold nanoparticle in liquid, using white light scattering spectroscopy. Using 40-nm-diameter gold nanoparticles coated with thermo-responsive polymer, we monitored the localized heating effect through the plasmon peak shift. The shift occurs due to the temperature-dependent refractive index change in surrounding polymer medium. The results indicate that the particle experiences a temperature rise of around 10 degrees Celsius when irradiated with tightly focused irradiation of ~1 mW at 532 nm.

  10. Effect of Heat Treatment on Microstructure Characteristics of Laser Composites

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Zhang, Yuanbin; Li, Yajiang; Yang, Qingqing; Liu, Yan; Ren, Guocheng

    2014-12-01

    In this paper, effect of heat treatment on the microstructures and wear properties of laser alloying (LA) composites is investigated. LA of the T-Co50/FeSi/TiC/TiN/CeO2 mixed powders on substrate of 45 steel can form the hard composites, which increased the wear resistance of substrate greatly. Such LA composites were investigated by means of a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The tempering promoted the growth of the block-shape hard phases, favoring an enhancement of the integrity of block-shape hard phases; and tempering also improved greatly the formation mechanism, guarantying the composites to have enough ability of intensity transfer. This research provided essential experiment and theoretical basis to promote the application of the laser and heat treatment technologies in the field of surface modification.

  11. Heat pipe array heat exchanger

    DOEpatents

    Reimann, Robert C.

    1987-08-25

    A heat pipe arrangement for exchanging heat between two different temperature fluids. The heat pipe arrangement is in a ounterflow relationship to increase the efficiency of the coupling of the heat from a heat source to a heat sink.

  12. Synergistic skin heat shock protein expression in response to combined laser treatment with a diode laser and ablative fractional lasers.

    PubMed

    Paasch, Uwe; Sonja, Grunewald; Haedersdal, Merete

    2014-06-01

    Diode laser-based skin heating has been shown to minimise scars by interfering with wound healing responses through the induction of heat shock proteins (HSP). HSP are also induced after ablative fractional laser (AFXL) wound healing. AFXL itself is highly recommended for scar treatment. Therefore, the sequential combination of both modalities may produce superior outcomes. The aim of this study was to examine the pretreatment effects of a diode laser before AFXL on wound healing responses in terms of HSP up-regulation in an in vitro model. Immediate responses and responses on days 1, 3 or 6 post-procedure were studied in an in vitro porcine skin model (n = 240). Untreated samples served as control. Immunohistochemical investigation (Hsp70) was performed in all untreated controls, diode laser-, AFXL-, and in diode laser + AFXL-treated samples. Hsp70 was shown to be up-regulated by all interventions between days 1 and 6 after interventions. The largest effect was caused by the combination of a diode laser and an AFXL procedure. Diode laser exposure induces a skin HSP response that can be further enhanced by sequential AFXL treatment. Clinical studies are necessary to investigate the dose response of HSP on scar formation and refine suitable laser exposure settings.

  13. Strongly-coupled plasmas formed from laser-heated solids

    PubMed Central

    Lyon, M.; Bergeson, S. D.; Hart, G.; Murillo, M. S.

    2015-01-01

    We present an analysis of ion temperatures in laser-produced plasmas formed from solids with different initial lattice structures. We show that the equilibrium ion temperature is limited by a mismatch between the initial crystallographic configuration and the close-packed configuration of a strongly-coupled plasma, similar to experiments in ultracold neutral plasmas. We propose experiments to demonstrate and exploit this crystallographic heating in order to produce a strongly coupled plasma with a coupling parameter of several hundred. PMID:26503293

  14. Ballistic heat transport in laser generated nano-bubbles.

    PubMed

    Lombard, Julien; Biben, Thierry; Merabia, Samy

    2016-08-04

    Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications.

  15. Temperature field around a laser-heated coal particle

    SciTech Connect

    Feng, B.; Liu, Y.H.; Zhou, Y.B.; Liu, Z.H.; Zheng, C.G.

    1997-12-31

    Holography was used to measure the temperature field around a laser heated coal particle. A man-made coal particle (with the size of 5mm in diameter and 5mm in length) was ignited by a laser beam (with the maximum power of 15W). And then the temperature distribution around the particle was obtained from the holograph which was developed by the authors. A bituminous coal, an anthracite and a sub-bituminous coal were used. It was interesting to find that there exists a zone near the particle surface where the temperature is higher than that at the surface for the bituminous coal during the combustion of the coal although the phenomenon was not found for the other coals. A mathematical model taking into account the laser induced energy was developed to calculate the temperature field around the particle. The predicted results were compared with the experimental ones.

  16. Laser heated pedestal growth system commissioning and fiber processing

    NASA Astrophysics Data System (ADS)

    Buric, Michael; Yip, M. J.; Chorpening, Ben; Ohodnicki, Paul

    2016-05-01

    A new Laser Heated Pedestal Growth system was designed and fabricated using various aspects of effective legacy designs for the growth of single-crystal high-temperature-compatible optical fibers. The system is heated by a 100-watt, DC driven, CO2 laser with PID power control. Fiber diameter measurements are performed using a telecentric video system which identifies the molten zone and utilizes edge detection algorithms to report fiber-diameter. Beam shaping components include a beam telescope; along with gold-coated reflaxicon, turning, and parabolic focusing mirrors consistent with similar previous systems. The optical system permits melting of sapphire-feedstock up to 1.5mm in diameter for growth. Details regarding operational characteristics are reviewed and properties of single-crystal sapphire fibers produced by the system are evaluated. Aspects of the control algorithm efficacy will be discussed, along with relevant alternatives. Finally, some new techniques for in-situ processing making use of the laser-heating system are discussed. Ex-situ fiber modification and processing are also examined for improvements in fiber properties.

  17. Quantum cascade lasers that emit more light than heat

    NASA Astrophysics Data System (ADS)

    Bai, Yanbo; Slivken, Steven; Kuboya, Shigeyuki; Darvish, Shaban R.; Razeghi, Manijeh

    2010-02-01

    For any semiconductor lasers, the wall plug efficiency, that is, the portion of the injected electrical energy that can be converted into output optical energy, is one of the most important figures of merit. A device with a higher wall plug efficiency has a lower power demand and prolonged device lifetime due to its reduced self-heating. Since its invention, the power performance of the quantum cascade laser has improved tremendously. However, although the internal quantum efficiency can be engineered to be greater than 80% at low temperatures, the wall plug efficiency of a quantum cascade laser has never been demonstrated above 50% at any temperature. The best wall plug efficiency reported to date is 36% at 120 K (ref. 9). Here, we overcome the limiting factors using a single-well injector design and demonstrate 53% wall plug efficiency at 40 K with an emitting wavelength of 5 µm. In other words, we demonstrate a quantum cascade laser that produces more light than heat.

  18. Tritium Removal by Laser Heating and Its Application to Tokamaks

    SciTech Connect

    C.H. Skinner; C.A. Gentile; G. Guttadora; A. Carpe; S. Langish; K.M. Young; M. Nishi; W. Shu

    2001-11-16

    A novel laser heating technique has recently been applied to removing tritium from carbon tiles that had been exposed to deuterium-tritium (DT) plasmas in the Tokamak Test Fusion Reactor (TFTR). A continuous wave neodymium laser, of power up to 300 watts, was used to heat the surface of the tiles. The beam was focused to an intensity, typically 8 kW/cm{sup 2}, and rapidly scanned over the tile surface by galvanometer-driven scanning mirrors. Under the laser irradiation, the surface temperature increased dramatically, and temperatures up to 2,300 degrees C were recorded by an optical pyrometer. Tritium was released and circulated in a closed-loop system to an ionization chamber that measured the tritium concentration. Most of the tritium (up to 84%) could be released by the laser scan. This technique appears promising for tritium removal in a next-step DT device as it avoids oxidation, the associated deconditioning of the plasma facing surfaces, and the expense of processing large quantities of tritium oxide. Some engineering aspects of the implementation of this method in a next-step fusion device will be discussed.

  19. Tritium Removal by Laser Heating and Its Application to Tokamaks

    SciTech Connect

    C.H. Skinner; C.A. Gentile; G. Guttadora; A. Carpe; S. Langish; K.M. Young; M. Nishi; W. Shu

    2001-11-16

    A novel laser heating technique has recently been applied to removing tritium from carbon tiles that had been exposed to deuterium-tritium (DT) plasmas in the Tokamak Test Fusion Reactor (TFTR). A continuous wave neodymium laser, of power up to 300 watts, was used to heat the surface of the tiles. The beam was focused to an intensity, typically 8 kW/cm{sup 2}, and rapidly scanned over the tile surface by galvanometer-driven scanning mirrors. Under the laser irradiation, the surface temperature increased dramatically, and temperatures up to 2,300 degrees C were recorded by an optical pyrometer. Tritium was released and circulated in a closed-loop system to an ionization chamber that measured the tritium concentration. Most of the tritium (up to 84%) could be released by the laser scan. This technique appears promising for tritium removal in a next-step DT device as it avoids oxidation, the associated deconditioning of the plasma facing surfaces, and the expense of processing large quantities of tritium oxide. Some engineering aspects of the implementation of this method in a next-step fusion device will be discussed.

  20. Ballistic heat transport in laser generated nano-bubbles

    NASA Astrophysics Data System (ADS)

    Lombard, Julien; Biben, Thierry; Merabia, Samy

    2016-08-01

    Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications.Nanobubbles generated by laser heated plasmonic nanoparticles are of interest for biomedical and energy harvesting applications. Of utmost importance is the maximal size of these transient bubbles. Here, we report hydrodynamic phase field simulations of the dynamics of laser induced nanobubbles, with the aim to understand which physical processes govern their maximal size. We show that the nanobubble maximal size and lifetime are to a large extent controlled by the ballistic thermal flux which is present inside the bubble. Taking into account this thermal flux, we can reproduce the fluence dependence of the maximal nanobubble radius as reported experimentally. We also discuss the influence of the laser pulse duration on the number of nanobubbles generated and their maximal size. These studies represent a significant step toward the optimization of the nanobubble size, which is of crucial importance for photothermal cancer therapy applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR02144A

  1. Combined Laser Ultrasonics, Laser Heating and Raman Scattering in Diamond Anvil Cell System

    NASA Astrophysics Data System (ADS)

    Zinin, P.; Prakapenka, V.; Odake, S.; Zhang, Y.; Ming, L.; Burgess, K.

    2012-12-01

    We developed a unique and multifunctional in-situ measurement system under high pressure equipped with laser ultrasonics system [1], Raman device, and laser heating system (LH-LU-DAC) at the University of Hawaii (Fig. 1). The sketch of the LH-LU-DAC system is shown in Fig. 1b. The system consists of four components: (1) LU-DAC system (probe and pump lasers, photodetector, and oscilloscope); (2) a fiber laser (100 W, 1064 nm), which is designed to allow precise control of the total power in the range from 2 to 100W by changing the diode current, for heating samples; (3) a spectrometer for measuring the temperature of the sample, fluorescence spectrum (spectrum of the ruby for pressure measurement), and Raman scattering measurements inside DAC under high pressure and high temperature (HPHT) conditions; and (4) an optical system for focusing laser beams (pump, probe, and 100W CW lasers) on the sample in DAC and for imaging a sample inside the DAC. The imaging optical system includes power regulators, combining optics, laser power detector, beam splitter, and focusing system (Fig. 2). The system allows us to: (a) measure acoustical properties of materials under HPHT; (b) synthesize new phases under HPHT; and (c) measure Raman scattering under HPHT conditions for detection of phase transition. [1]. N. Chigarev, P. Zinin, M. Li-Chung, G. Amulele, A. Bulou, V. Gusev, Appl. Phys. Lett. 93, 181905 (2008).; Image of the combined LU-DAC, laser heating, and Raman scattering system at the University of Hawaii. ; Sketch of the LH-LU-DAC system.

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

    PubMed

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

    2012-08-01

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

  3. Electron heating enhancement by frequency-chirped laser pulses

    NASA Astrophysics Data System (ADS)

    Yazdani, E.; Sadighi-Bonabi, R.; Afarideh, H.; Riazi, Z.; Hora, H.

    2014-09-01

    Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic field is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a0 = 5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about ne ≈ 6nc, where nc is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.

  4. Electron heating enhancement by frequency-chirped laser pulses

    SciTech Connect

    Yazdani, E.; Afarideh, H.; Sadighi-Bonabi, R.; Riazi, Z.; Hora, H.

    2014-09-14

    Propagation of a chirped laser pulse with a circular polarization through an uprising plasma density profile is studied by using 1D-3V particle-in-cell simulation. The laser penetration depth is increased in an overdense plasma compared to an unchirped pulse. The induced transparency due to the laser frequency chirp results in an enhanced heating of hot electrons as well as increased maximum longitudinal electrostatic field at the back side of the solid target, which is very essential in target normal sheath acceleration regime of proton acceleration. For an applied chirp parameter between 0.008 and 0.01, the maximum amount of the electrostatic field is improved by a factor of 2. Furthermore, it is noticed that for a chirped laser pulse with a₀=5, because of increasing the plasma transparency length, the laser pulse can penetrate up to about n{sub e}≈6n{sub c}, where n{sub c} is plasma critical density. It shows 63% increase in the effective critical density compared to the relativistic induced transparency regime for an unchirped condition.

  5. High frequency alternating current chip nano calorimeter with laser heating

    SciTech Connect

    Shoifet, E.; Schick, C.; Chua, Y. Z.; Huth, H.

    2013-07-15

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3ω-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (∼1 μm) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 μm thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 μm{sup 2}). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10{sup −3} Hz and 10{sup 6} Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  6. High frequency alternating current chip nano calorimeter with laser heating.

    PubMed

    Shoifet, E; Chua, Y Z; Huth, H; Schick, C

    2013-07-01

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3ω-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (~1 μm) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 μm thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 μm(2)). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10(-3) Hz and 10(6) Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  7. High frequency alternating current chip nano calorimeter with laser heating

    NASA Astrophysics Data System (ADS)

    Shoifet, E.; Chua, Y. Z.; Huth, H.; Schick, C.

    2013-07-01

    Heat capacity spectroscopy at frequencies up to 100 kHz is commonly performed by thermal effusivity measurements applying the 3ω-technique. Here we show that AC-calorimetry using a thin film chip sensor allows for the measurement of frequency dependent heat capacity in the thin film limit up to about 1 MHz. Using films thinner than the thermal length of the thermal wave (˜1 μm) at such frequencies is advantageous because it provides heat capacity alone and not in combination with other quantities like thermal conductivity, at least on a qualitative basis. The used calorimetric sensor and the sample are each less than 1 μm thick. For high frequency AC-calorimetry, high cooling rates at very small temperature differences are required. This is realized by minimizing the heated spot to the size of the on chip thermocouple (3 × 6 μm2). A modulated laser beam shaped and positioned by a glass fiber is used as the heat source. The device was used to measure the complex heat capacity in the vicinity of the dynamic glass transition (structural relaxation) of poly(methyl methacrylate). Combining different calorimeters finally provides data between 10-3 Hz and 106 Hz. In this frequency range the dynamic glass transition shifts about 120 K.

  8. Combined Laser Ultrasonics, Laser Heating and Raman Scattering in Diamond Anvil Cell System

    NASA Astrophysics Data System (ADS)

    Zinin, Pavel; Prakapenka, Vitali; Odake, Shoko; Burgess, Katherine

    2013-06-01

    We developed a unique and multifunctional in-situ measurement system under high pressure equipped with laser ultrasonics system, Raman device, and laser heating system (LH-LU-DAC) at the University of Hawaii. The system consists of four components: (1) LU-DAC system (probe and pump lasers, photodetector, and oscilloscope); (2) a fiber laser (1064 nm), which is designed to allow precise control of the total power in the range from 2 to 100 W by changing the diode current, for heating samples; (3) a spectrometer for measuring the temperature of the sample (using Black body radiation), fluorescence spectrum (spectrum of the ruby for pressure measurement), and Raman scattering measurements inside DAC under high pressure and high temperature (HPHT) conditions; and (4) an optical system for focusing laser beams (pump, probe, and 100 W CW lasers) on the sample in DAC and for imaging a sample inside the DAC. The system allows us to: (a) measure acoustical properties of materials under HPHT; (b) synthesize new phases under HPHT; and (c) measure Raman scattering under HPHT conditions for detection of phase transition. This work was supported by the U.S. DOE Grant, NO. DE-FG02-07ER46408, and NSF Grant, NO. EAR-1215796.

  9. High energy bursts from a solid state laser operated in the heat capacity limited regime

    SciTech Connect

    Albrecht, G.; George, E.V.; Krupke, W.

    1994-12-31

    Solid state laser technology is a very well developed field and numerous embodiments and modes of operation have been demonstrated. A more recent development has been the pumping of a solid state laser active medium with an array of diode lasers (diode pumping, for short). These diode pump packages have previously been developed to pump solid state lasers with good efficiency, but low average power. This invention is a method and the resulting apparatus for operating a solid state laser in the heat capacity mode. Instead of cooling the laser, the active medium will heat up until it reaches some maximum acceptable temperature. The waste heat is stored in the active medium itself.

  10. A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

    NASA Technical Reports Server (NTRS)

    Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

    1991-01-01

    A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high speed flow fields.

  11. A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

    NASA Technical Reports Server (NTRS)

    Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

    1991-01-01

    A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high-speed flowfields.

  12. A laser-induced heat flux technique for convective heat transfer measurements in high speed flows

    NASA Technical Reports Server (NTRS)

    Porro, A. R.; Keith, T. G., Jr.; Hingst, W. R.

    1991-01-01

    A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to the heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the local surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimentally determined convective heat transfer coefficients were generally higher than the theoretical predictions for flat plate laminar boundary layers. However, the results indicate that this nonintrusive optical measurement technique has the potential to measure surface convective heat transfer coefficients in high-speed flowfields.

  13. Spin diffusion induced by pulsed-laser heating and the role of spin heat accumulation

    NASA Astrophysics Data System (ADS)

    Kimling, Johannes; Cahill, David G.

    2017-01-01

    We present a model for describing spin diffusion in normal-metal/ferromagnetic-metal heterostructures induced by pulsed-laser heating. The model is based on the assumptions that electronic heat currents give rise to the spin-dependent Seebeck effect and that ultrafast demagnetization generates spin accumulation with a rate proportional to the demagnetization rate measured. Spin-diffusion currents are then driven by gradients in spin accumulation and electron temperature. The model considers spin-dependent thermal conductivity and electron-phonon coupling, which can give rise to different effective temperatures for majority and minority spins, known as spin heat accumulation. We find that spin heat accumulation can significantly enhance the spin-dependent Seebeck effect.

  14. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Study of symmetrising action of laser prepulse on inhomogeneity of thin foil heating

    NASA Astrophysics Data System (ADS)

    Ilyasov, A. O.; Lebo, I. G.; Mikhailov, Yu A.; Rozanov, Vladislav B.; Sklizkov, G. V.; Starodub, Aleksandr N.; Tishkin, V. F.

    2005-07-01

    The results of theoretical and experimental studies of plasma heating by laser radiation having an inhomogeneous spatial structure are presented as well as the results of investigation of the symmetrising action of a laser prepulse on the inhomogeneity of heating of thin foils modelling thin-walled laser thermonuclear synthesis targets. The high efficiency of the method of ablation pressure symmetrisation by a laser prepulse is demonstrated.

  15. Performance and heat transfer characteristics of the laser-heated rocket - A future space transportation system

    NASA Technical Reports Server (NTRS)

    Shoji, J. M.; Larson, V. R.

    1976-01-01

    The application of advanced liquid-bipropellant rocket engine analysis techniques has been utilized for prediction of the potential delivered performance and the design of thruster wall cooling schemes for laser-heated rocket thrusters. Delivered specific impulse values greater than 1000 lbf-sec/lbm are potentially achievable based on calculations for thrusters designed for 10-kW and 5000-kW laser beam power levels. A thruster wall-cooling technique utilizing a combination of regenerative cooling and a carbon-seeded hydrogen boundary layer is presented. The flowing carbon-seeded hydrogen boundary layer provides radiation absorption of the heat radiated from the high-temperature plasma. Also described is a forced convection thruster wall cooling design for an experimental test thruster.

  16. Performance and heat transfer characteristics of the laser-heated rocket - A future space transportation system

    NASA Technical Reports Server (NTRS)

    Shoji, J. M.; Larson, V. R.

    1976-01-01

    The application of advanced liquid-bipropellant rocket engine analysis techniques has been utilized for prediction of the potential delivered performance and the design of thruster wall cooling schemes for laser-heated rocket thrusters. Delivered specific impulse values greater than 1000 lbf-sec/lbm are potentially achievable based on calculations for thrusters designed for 10-kW and 5000-kW laser beam power levels. A thruster wall-cooling technique utilizing a combination of regenerative cooling and a carbon-seeded hydrogen boundary layer is presented. The flowing carbon-seeded hydrogen boundary layer provides radiation absorption of the heat radiated from the high-temperature plasma. Also described is a forced convection thruster wall cooling design for an experimental test thruster.

  17. Quasi-passive heat sink for high-power laser diodes

    NASA Astrophysics Data System (ADS)

    Vetrovec, John

    2009-02-01

    We report on a novel heat sink for high-power laser diodes offering unparalleled capacity in high-heat flux handling and temperature control. The heat sink uses a liquid coolant flowing at high speed in a miniature closed and sealed loop. Diode waste heat is received at high flux and transferred to environment, coolant fluid, heat pipe, or structure at a reduced flux. When pumping solid-state or alkali vapor lasers, diode wavelength can be electronically tuned to the absorption features of the laser gain medium. This paper presents the heat sink physics, engineering design, performance modeling, and configurations.

  18. Combined laser ultrasonics, laser heating, and Raman scattering in diamond anvil cell system

    NASA Astrophysics Data System (ADS)

    Zinin, Pavel V.; Prakapenka, Vitali B.; Burgess, Katherine; Odake, Shoko; Chigarev, Nikolay; Sharma, Shiv K.

    2016-12-01

    We developed a multi-functional in situ measurement system under high pressure equipped with a laser ultrasonics (LU) system, Raman device, and laser heating system (LU-LH) in a diamond anvil cell (DAC). The system consists of four components: (1) a LU-DAC system (probe and pump lasers, photodetector, and oscilloscope) and DAC; (2) a fiber laser, which is designed to allow precise control of the total power in the range from 2 to 100 W by changing the diode current, for heating samples; (3) a spectrometer for measuring the temperature of the sample (using black body radiation), fluorescence spectrum (spectrum of the ruby for pressure measurement), and Raman scattering measurements inside a DAC under high pressure and high temperature (HPHT) conditions; and (4) an optical system to focus laser beams on the sample and image it in the DAC. The system is unique and allows us to do the following: (a) measure the shear and longitudinal velocities of non-transparent materials under HPHT; (b) measure temperature in a DAC under HPHT conditions using Planck's law; (c) measure pressure in a DAC using a Raman signal; and (d) measure acoustical properties of small flat specimens removed from the DAC after HPHT treatment. In this report, we demonstrate that the LU-LH-DAC system allows measurements of velocities of the skimming waves in iron at 2580 K and 22 GPa.

  19. Combined laser ultrasonics, laser heating, and Raman scattering in diamond anvil cell system.

    PubMed

    Zinin, Pavel V; Prakapenka, Vitali B; Burgess, Katherine; Odake, Shoko; Chigarev, Nikolay; Sharma, Shiv K

    2016-12-01

    We developed a multi-functional in situ measurement system under high pressure equipped with a laser ultrasonics (LU) system, Raman device, and laser heating system (LU-LH) in a diamond anvil cell (DAC). The system consists of four components: (1) a LU-DAC system (probe and pump lasers, photodetector, and oscilloscope) and DAC; (2) a fiber laser, which is designed to allow precise control of the total power in the range from 2 to 100 W by changing the diode current, for heating samples; (3) a spectrometer for measuring the temperature of the sample (using black body radiation), fluorescence spectrum (spectrum of the ruby for pressure measurement), and Raman scattering measurements inside a DAC under high pressure and high temperature (HPHT) conditions; and (4) an optical system to focus laser beams on the sample and image it in the DAC. The system is unique and allows us to do the following: (a) measure the shear and longitudinal velocities of non-transparent materials under HPHT; (b) measure temperature in a DAC under HPHT conditions using Planck's law; (c) measure pressure in a DAC using a Raman signal; and (d) measure acoustical properties of small flat specimens removed from the DAC after HPHT treatment. In this report, we demonstrate that the LU-LH-DAC system allows measurements of velocities of the skimming waves in iron at 2580 K and 22 GPa.

  20. Temperature distributions in the laser-heated diamond anvil cell from 3-D numerical modeling

    SciTech Connect

    Rainey, E. S. G.; Kavner, A.; Hernlund, J. W.

    2013-11-28

    We present TempDAC, a 3-D numerical model for calculating the steady-state temperature distribution for continuous wave laser-heated experiments in the diamond anvil cell. TempDAC solves the steady heat conduction equation in three dimensions over the sample chamber, gasket, and diamond anvils and includes material-, temperature-, and direction-dependent thermal conductivity, while allowing for flexible sample geometries, laser beam intensity profile, and laser absorption properties. The model has been validated against an axisymmetric analytic solution for the temperature distribution within a laser-heated sample. Example calculations illustrate the importance of considering heat flow in three dimensions for the laser-heated diamond anvil cell. In particular, we show that a “flat top” input laser beam profile does not lead to a more uniform temperature distribution or flatter temperature gradients than a wide Gaussian laser beam.

  1. Study, optimization, and design of a laser heat engine. [for satellite applications

    NASA Technical Reports Server (NTRS)

    Taussig, R. T.; Cassady, P. E.; Zumdieck, J. F.

    1978-01-01

    Laser heat engine concepts, proposed for satellite applications, are analyzed to determine which engine concept best meets the requirements of high efficiency (50 percent or better), continuous operation in space using near-term technology. The analysis of laser heat engines includes the thermodynamic cycles, engine design, laser power sources, collector/concentrator optics, receiving windows, absorbers, working fluids, electricity generation, and heat rejection. Specific engine concepts, optimized according to thermal efficiency, are rated by their technological availability and scaling to higher powers. A near-term experimental demonstration of the laser heat engine concept appears feasible utilizing an Otto cycle powered by CO2 laser radiation coupled into the engine through a diamond window. Higher cycle temperatures, higher efficiencies, and scalability to larger sizes appear to be achievable from a laser heat engine design based on the Brayton cycle and powered by a CO laser.

  2. Elastic characterization of platinum/rhodium alloy at high temperature by combined laser heating and laser ultrasonic techniques.

    PubMed

    Burgess, K; Prakapenka, V; Hellebrand, E; Zinin, P V

    2014-04-01

    We demonstrate an innovative pump-probe technique combined with laser heating to determine the velocity of a surface Rayleigh wave at high temperature. Laser ultrasonics in a point-source-point-receiver configuration was combined with laser heating to evaluate the elastic properties of micron size specimens. The measurements of the velocity of the surface Rayleigh wave (SRW) were conducted at 1070K. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. 21nm x-ray laser Thomson scattering of laser-heated exploding foil plasmas

    SciTech Connect

    Dunn, J; Rus, B; Mocek, T; Nelson, A J; Foord, M E; Rozmus, W; Baldis, H A; Shepherd, R L; Kozlova, M; Polan, J; Homer, P; Stupka, M

    2007-09-26

    Recent experiments were carried out on the Prague Asterix Laser System (PALS) towards the demonstration of a soft x-ray laser Thomson scattering diagnostic for a laser-produced exploding foil. The Thomson probe utilized the Ne-like zinc x-ray laser which was double-passed to deliver {approx}1 mJ of focused energy at 21.2 nm wavelength and lasting {approx}100 ps. The plasma under study was heated single-sided using a Gaussian 300-ps pulse of 438-nm light (3{omega} of the PALS iodine laser) at laser irradiances of 10{sup 13}-10{sup 14} W cm{sup -2}. Electron densities of 10{sup 20}-10{sup 22} cm{sup -3} and electron temperatures from 200 to 500 eV were probed at 0.5 or 1 ns after the peak of the heating pulse during the foil plasma expansion. A flat-field 1200 line mm{sup -1} variable-spaced grating spectrometer with a cooled charge-coupled device readout viewed the plasma in the forward direction at 30{sup o} with respect to the x-ray laser probe. We show results from plasmas generated from {approx}1 {micro}m thick targets of Al and polypropylene (C{sub 3}H{sub 6}). Numerical simulations of the Thomson scattering cross-sections will be presented. These simulations show electron peaks in addition to a narrow ion feature due to collective (incoherent) Thomson scattering. The electron features are shifted from the frequency of the scattered radiation approximately by the electron plasma frequency {+-}{omega}{sub pe} and scale as n{sub e}{sup 1/2}.

  4. Compact laser molecular beam epitaxy system using laser heating of substrate for oxide film growth

    NASA Astrophysics Data System (ADS)

    Ohashi, S.; Lippmaa, M.; Nakagawa, N.; Nagasawa, H.; Koinuma, H.; Kawasaki, M.

    1999-01-01

    A high-temperature, oxygen compatible, and compact laser molecular beam epitaxy (laser MBE) system has been developed. The 1.06 μm infrared light from a continuous wave neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was used to achieve a wide range and rapid control of substrate temperature in ultrahigh vacuum and at up to 1 atm oxygen pressure. The maximum usable temperature was limited to 1453 °C by the melting point of the nickel sample holder. To our knowledge, this is the highest temperature reported for pulsed laser deposition of oxide films. The efficient laser heating combined with temperature monitoring by a pyrometer and feedback control of the Nd:YAG laser power by a personal computer made it possible to regulate the substrate temperature accurately and to achieve high sample heating and cooling rates. The oxygen pressure and ablation laser triggering were also controlled by the computer. The accurate growth parameter control was combined with real-time in situ surface structure monitoring by reflection high energy electron diffraction to investigate oxide thin film growth in detail over a wide range of temperatures, oxygen partial pressures, and deposition rates. We have demonstrated the performance of this system by the fabrication of homoepitaxial SrTiO3 films as well as heteroepitaxial Sr2RuO4, and SrRuO3 films on SrTiO3 substrates at temperatures of up to 1300 °C. This temperature was high enough to change the film growth mode from layer by layer to step flow.

  5. SiC growth by Solvent-Laser Heated Floating Zone

    NASA Technical Reports Server (NTRS)

    Woodworth, Andrew A.; Neudeck, Philip G.; Sayir, Ali; Spry, David J.; Trunek, Andrew J.; Powell, J. Anthony

    2011-01-01

    In an effort to grow single crystal SiC fibers for seed crystals the following two growth methods have been coupled in this work: traveling solvent and laser heated floating zone to create the solvent-laser heated floating zone (Solvent-LHFZ) crystal growth method. This paper discusses the results of these initial experiments, which includes: source material, laser heating, and analysis of the first ever Solvent-LHFZ SiC crystals (synchrotron white beam x-ray topography confirmed).

  6. SiC growth by Solvent-Laser Heated Floating Zone

    NASA Technical Reports Server (NTRS)

    Woodworth, Andrew A.; Neudeck, Philip G.; Sayir, Ali; Spry, David J.; Trunek, Andrew J.; Powell, J. Anthony

    2011-01-01

    In an effort to grow single crystal SiC fibers for seed crystals the following two growth methods have been coupled in this work: traveling solvent and laser heated floating zone to create the solvent-laser heated floating zone (Solvent-LHFZ) crystal growth method. This paper discusses the results of these initial experiments, which includes: source material, laser heating, and analysis of the first ever Solvent-LHFZ SiC crystals (synchrotron white beam x-ray topography confirmed).

  7. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Smoothing of ablation pressure nonuniformities in the laser-plasma corona during heating of laser fusion targets

    NASA Astrophysics Data System (ADS)

    Zhurovich, M. A.; Zhitkova, O. A.; Lebo, I. G.; Mikhailov, Yu A.; Sklizkov, G. V.; Starodub, Aleksandr N.; Tishkin, V. F.

    2009-06-01

    A method for smoothing ablation pressure nonuniformities during heating of laser fusion targets is described which utilises an extra laser pulse preceding the main pulse. Theoretical and experimental data are presented on heating of thin (3-10 μm) foils (simulating the target shell) by a spatially nonuniform laser beam. In the experiments, the laser pulse width at half maximum was 2 ns and the pulse energy was 2-30 J, which ensured a power density on the target surface from 1013 to 1014 W cm-2. The experimental data are analysed using two-dimensional numerical simulations. The experimental and simulation results demonstrate that this approach is sufficiently effective. The optimal laser prepulse parameters are determined.

  8. Direct heating of a laser-imploded core using ultraintense laser LFEX

    NASA Astrophysics Data System (ADS)

    Kitagawa, Y.; Mori, Y.; Ishii, K.; Hanayama, R.; Nishimura, Y.; Okihara, S.; Nakayama, S.; Sekine, T.; Takagi, M.; Watari, T.; Satoh, N.; Kawashima, T.; Komeda, O.; Hioki, T.; Motohiro, T.; Azuma, H.; Sunahara, A.; Sentoku, Y.; Arikawa, Y.; Abe, Y.; Miura, E.; Ozaki, T.

    2017-07-01

    A CD shell was preimploded by two counter-propagating green beams from the GEKKO laser system GXII (based at the Institute of Laser Engineering, Osaka University), forming a dense core. The core was predominantly heated by energetic ions driven by the laser for fast-ignition-fusion experiment, an extremely energetic ultrashort pulse laser, that is illuminated perpendicularly to the GXII axis. Consequently, we observed the D(d, n)3 He-reacted neutrons (DD beam-fusion neutrons) at a yield of 5× {{10}8} n/4π sr. The beam-fusion neutrons verified that the ions directly collided with the core plasma. Whereas the hot electrons heated the whole core volume, the energetic ions deposited their energies locally in the core. As evidenced in the spectrum, the process simultaneously excited thermal neutrons with a yield of 6× {{10}7} n/4π sr, raising the local core temperature from 0.8 to 1.8 keV. The shell-implosion dynamics (including the beam fusion and thermal fusion initiated by fast deuterons and carbon ions) can be explained by the one-dimensional hydrocode STAR 1D. Meanwhile, the core heating due to resistive processes driven by hot electrons, and also the generation of fast ions were well-predicted by the two-dimensional collisional particle-in-cell code. Together with hot electrons, the ion contribution to fast ignition is indispensable for realizing high-gain fusion. By virtue of its core heating and ignition, the proposed scheme can potentially achieve high-gain fusion.

  9. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Transient heat conduction in laser diodes

    NASA Astrophysics Data System (ADS)

    Enders, P.; Galley, J.

    1988-11-01

    The dynamics of heat transfer in stripe GaAlAs laser diodes is investigated by solving the linear diffusion equation for a quasitwo-dimensional multilayer structure. The calculations are rationalized drastically by the transfer matrix method and also using for the first time the asymptotes of the decay constants. Special attention is given to the convergence of the Fourier series. A comparison with experimental results reveals however that this is essentially the Stefan problem (with moving boundary conditions).

  10. EFFECT OF LASER LIGHT ON MATTER. LASER PLASMAS: X-ray spectral diagnostics of plasmas heated by picosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Bryunetkin, B. A.; Skobelev, I. Yu; Faenov, A. Ya; Khakhalin, S. Ya; Kalashnikov, M. P.; Nickles, P. V.; Schnürer, M.

    1993-06-01

    The properties of a magnesium plasma heated by picosecond laser pulses have been determined by x-ray spectral methods. Experiments were carried out at a laser power density ~ 1.5 · 1018 W/cm2. The x-ray spectra were detected by spectrographs with a plane CsAP crystal and a mica crystal bent into part of a spherical surface 10 cm in radius. The experimental data are compared with predictions of a calculation on the time-varying kinetics of multiply charged magnesium ions.

  11. Electromagnetic instability in plasmas heated by a laser field.

    PubMed

    Bendib, A; Bendib-Kalache, K; Cros, B; Deutsch, C; Maynard, G

    2017-02-01

    Electromagnetic instability is investigated in homogeneous plasmas heated by a laser wave in the range α=v_{0}^{2}/v_{t}^{2}≤2, where v_{0} is the electron quiver velocity and v_{t} is the thermal velocity. The anisotropic electron distribution function that drives unstable quasistatic electromagnetic modes is calculated numerically with the Vlasov-Landau equation in the high ion charge number approximation. A dispersion relation of electromagnetic waves which accounts for further nonlinear terms on v_{0}^{2} from previous results is derived. In typical simulation with ion charge number Z=13, a temperature T=5keV, a density n=9.8×10^{20}cm^{-3}, and a laser wavelength λ_{laser}=1.06μm, growth rates larger than 10^{12}s^{-1} in the quasicollisionless wave-number range were found for α≥1. In the same physical conditions and in the mildly collisional range a growth rate about 10^{11}s^{-1} was also obtained. The extent of the growth wave-number region increases significantly with increasing α.

  12. Laser heating method for estimation of carbon nanotube purity

    NASA Astrophysics Data System (ADS)

    Terekhov, S. V.; Obraztsova, E. D.; Lobach, A. S.; Konov, V. I.

    A new method of a carbon nanotube purity estimation has been developed on the basis of Raman spectroscopy. The spectra of carbon soot containing different amounts of nanotubes were registered under heating from a probing laser beam with a step-by-step increased power density. The material temperature in the laser spot was estimated from a position of the tangential Raman mode demonstrating a linear thermal shift (-0.012 cm-1/K) from the position 1592 cm-1 (at room temperature). The rate of the material temperature rise versus the laser power density (determining the slope of a corresponding graph) appeared to correlate strongly with the nanotube content in the soot. The influence of the experimental conditions on the slope value has been excluded via a simultaneous measurement of a reference sample with a high nanotube content (95 vol.%). After the calibration (done by a comparison of the Raman and the transmission electron microscopy data for the nanotube percentage in the same samples) the Raman-based method is able to provide a quantitative purity estimation for any nanotube-containing material.

  13. Electromagnetic instability in plasmas heated by a laser field

    NASA Astrophysics Data System (ADS)

    Bendib, A.; Bendib-Kalache, K.; Cros, B.; Deutsch, C.; Maynard, G.

    2017-02-01

    Electromagnetic instability is investigated in homogeneous plasmas heated by a laser wave in the range α =v02/vt2≤2 , where v0 is the electron quiver velocity and vt is the thermal velocity. The anisotropic electron distribution function that drives unstable quasistatic electromagnetic modes is calculated numerically with the Vlasov-Landau equation in the high ion charge number approximation. A dispersion relation of electromagnetic waves which accounts for further nonlinear terms on v02 from previous results is derived. In typical simulation with ion charge number Z =13 , a temperature T =5 keV , a density n =9.8 ×1020c m-3 , and a laser wavelength λlaser=1.06 μ m , growth rates larger than 1012s-1 in the quasicollisionless wave-number range were found for α ≥1 . In the same physical conditions and in the mildly collisional range a growth rate about 1011s-1 was also obtained. The extent of the growth wave-number region increases significantly with increasing α .

  14. Spectroscopic study of the effect of laser heating on collagen stability: implications for tissue welding

    NASA Astrophysics Data System (ADS)

    Small, Ward, IV; Da Silva, Luiz B.; Matthews, Dennis L.

    1998-07-01

    Collagen is believed to play a major role in laser tissue welding. Furthermore, the fundamental fusion mechanism(s) may include thermal denaturation of the collagen fibers. An in vitro investigation of the effect of laser heating (1.9 micrometer diode laser) on collagen conformation was performed. Fourier transform infrared (FTIR) spectra of native and heated porcine cornea were obtained. A low-frequency shift in the amide A band of collagen around 3320 cm-1 indicated that conformational changes associated with denaturation occurred. Samples heated using a temperature feedback controlled 1.9 micrometer diode laser showed a gradual decrease in the amide A peak frequency with increasing temperature, as did samples heated in a water bath. Complete denaturation was achieved at temperatures above 85 degrees Celsius for both heating protocols. Water loss induced by laser heating may have reduced the mobility of the collagen polypeptide chains, and contributed to the elevated denaturation temperature.

  15. Regularly arranged indium islands on glass/molybdenum substrates upon femtosecond laser and physical vapor deposition processing

    SciTech Connect

    Ringleb, F.; Eylers, K.; Teubner, Th.; Boeck, T.; Symietz, C.; Bonse, J.; Andree, S.; Krüger, J.; Heidmann, B.; Schmid, M.; Lux-Steiner, M.

    2016-03-14

    A bottom-up approach is presented for the production of arrays of indium islands on a molybdenum layer on glass, which can serve as micro-sized precursors for indium compounds such as copper-indium-gallium-diselenide used in photovoltaics. Femtosecond laser ablation of glass and a subsequent deposition of a molybdenum film or direct laser processing of the molybdenum film both allow the preferential nucleation and growth of indium islands at the predefined locations in a following indium-based physical vapor deposition (PVD) process. A proper choice of laser and deposition parameters ensures the controlled growth of indium islands exclusively at the laser ablated spots. Based on a statistical analysis, these results are compared to the non-structured molybdenum surface, leading to randomly grown indium islands after PVD.

  16. Customer Overview of Pulsed Laser Heating for Evaluation of Gun Bore Materials

    DTIC Science & Technology

    2015-05-01

    Technical Report ARWSB-TR-15003 Customer Overview of Pulsed Laser Heating for Evaluation of Gun Bore Materials Mark E. Todaro...SUBTITLE Customer Overview of Pulsed Laser Heating for Evaluation of Gun Bore Materials 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  17. Direct heating of a laser-imploded core by ultraintense laser-driven ions.

    PubMed

    Kitagawa, Y; Mori, Y; Komeda, O; Ishii, K; Hanayama, R; Fujita, K; Okihara, S; Sekine, T; Satoh, N; Kurita, T; Takagi, M; Watari, T; Kawashima, T; Kan, H; Nishimura, Y; Sunahara, A; Sentoku, Y; Nakamura, N; Kondo, T; Fujine, M; Azuma, H; Motohiro, T; Hioki, T; Kakeno, M; Miura, E; Arikawa, Y; Nagai, T; Abe, Y; Ozaki, S; Noda, A

    2015-05-15

    A novel direct core heating fusion process is introduced, in which a preimploded core is predominantly heated by energetic ions driven by LFEX, an extremely energetic ultrashort pulse laser. Consequently, we have observed the D(d,n)^{3}He-reacted neutrons (DD beam-fusion neutrons) with the yield of 5×10^{8} n/4π sr. Examination of the beam-fusion neutrons verified that the ions directly collide with the core plasma. While the hot electrons heat the whole core volume, the energetic ions deposit their energies locally in the core, forming hot spots for fuel ignition. As evidenced in the spectrum, the process simultaneously excited thermal neutrons with the yield of 6×10^{7} n/4π sr, raising the local core temperature from 0.8 to 1.8 keV. A one-dimensional hydrocode STAR 1D explains the shell implosion dynamics including the beam fusion and thermal fusion initiated by fast deuterons and carbon ions. A two-dimensional collisional particle-in-cell code predicts the core heating due to resistive processes driven by hot electrons, and also the generation of fast ions, which could be an additional heating source when they reach the core. Since the core density is limited to 2 g/cm^{3} in the current experiment, neither hot electrons nor fast ions can efficiently deposit their energy and the neutron yield remains low. In future work, we will achieve the higher core density (>10 g/cm^{3}); then hot electrons could contribute more to the core heating via drag heating. Together with hot electrons, the ion contribution to fast ignition is indispensable for realizing high-gain fusion. By virtue of its core heating and ignition, the proposed scheme can potentially achieve high gain fusion.

  18. Collaborative Arrangements.

    ERIC Educational Resources Information Center

    Cota-Robles, Eugene; Doby, Winston

    Two conference papers describing various collaborative arrangements within the educational community among teachers, students and others are presented in this document. The first paper, "Successful Collaborations" (Eugene Cota-Robles), describes the following projects in California that seek to forge collaborations to improve the…

  19. High energy bursts from a solid state laser operated in the heat capacity limited regime

    DOEpatents

    Albrecht, Georg; George, E. Victor; Krupke, William F.; Sooy, Walter; Sutton, Steven B.

    1996-01-01

    High energy bursts are produced from a solid state laser operated in a heat capacity limited regime. Instead of cooling the laser, the active medium is thermally well isolated. As a result, the active medium will heat up until it reaches some maximum acceptable temperature. The waste heat is stored in the active medium itself. Therefore, the amount of energy the laser can put out during operation is proportional to its mass, the heat capacity of the active medium, and the temperature difference over which it is being operated. The high energy burst capacity of a heat capacity operated solid state laser, together with the absence of a heavy, power consuming steady state cooling system for the active medium, will make a variety of applications possible. Alternately, cooling takes place during a separate sequence when the laser is not operating. Industrial applications include new material working processes.

  20. High energy bursts from a solid state laser operated in the heat capacity limited regime

    DOEpatents

    Albrecht, G.; George, E.V.; Krupke, W.F.; Sooy, W.; Sutton, S.B.

    1996-06-11

    High energy bursts are produced from a solid state laser operated in a heat capacity limited regime. Instead of cooling the laser, the active medium is thermally well isolated. As a result, the active medium will heat up until it reaches some maximum acceptable temperature. The waste heat is stored in the active medium itself. Therefore, the amount of energy the laser can put out during operation is proportional to its mass, the heat capacity of the active medium, and the temperature difference over which it is being operated. The high energy burst capacity of a heat capacity operated solid state laser, together with the absence of a heavy, power consuming steady state cooling system for the active medium, will make a variety of applications possible. Alternately, cooling takes place during a separate sequence when the laser is not operating. Industrial applications include new material working processes. 5 figs.

  1. Infrared laser heating for studies of cellulose degradation

    SciTech Connect

    Jackson, J.P.; Arthurs, E.; Schwalbe, L.A.; Sega, R.M.; Windish, D.; Long, W.H.; Stappaerts, E.A.

    1988-09-15

    We describe a new technique for studying thermally induced chemical transformations in cellulose. The apparatus consists of a carbon dioxide laser for heating, an IR thermometer, and an optical reflectance spectrometer for tracking the progressive discoloration of the sample. To illustrate the technique, we present measurements from a single piece of sample linen along five isotherms in the 200--290/sup 0/C range. We derive an algebraic expression for the reflectivity of the sample as a function of the areal concentrations of the chromophoric states produced at temperature. The results are then explained in terms of first-order chemical rate theory and a four-step model. From the measurements we derive the activation energies, Arrhenius constants, and reflectivities of the chromophoric states.

  2. Heating of blood by low-intensity laser radiation

    NASA Astrophysics Data System (ADS)

    Korolevich, Alexander N.; Astafyeva, Liudmila G.; Dubina, Natali S.; Vecherinski, Sergei I.; Belsley, Michael S.

    2003-10-01

    Theoretical and experimental studies of the influence of low-intensity laser radiation, on the velocity of microcirculation of the erythrocytes of patients with the cardiovascular disease "in vivo" are carried out. Dynamic light scattering techniques were used to monitor the variation in the perfusion of micro capillary blood flow during irradiation under "in vivo" conditions and compared to the change in average size of aggregates of the blood effects observed "in vitro" using static scattering of light. It is shown that the process of the fragmentation of erythrocytes depends on amount of energy absorbed by biological tissues. This conclusion is supported by the good qualitative agreement with the theoretical model, based on the heat transfer theory within the dermis.

  3. High-definition color image in dye thermal transfer printing by laser heating

    NASA Astrophysics Data System (ADS)

    Kitamura, Takashi

    1999-12-01

    In laser thermal transfer printing using dye sublimation type medium, a high definition and continuous tone image can be obtained easily because the laser beam is focused to small spot and heat energy can be controlled by the pulse width modulation of laser light. The donor ink sheet is composed of the laser absorbing layer and sublimation dye layer. The tone reproduction was depend on the mixture ratio of dye to binder and thickness of ink layer. The four color ink sheets such as cyan, magenta, yellow and black were prepared for color printing image which have a high resolution and good continuous tone reproduction using sublimation dye transfer printing by laser heating.

  4. Laser heating of finite two-dimensional dust clusters: A. Experiments

    SciTech Connect

    Schablinski, Jan; Block, Dietmar; Piel, Alexander; Melzer, Andre; Thomsen, Hauke; Kaehlert, Hanno; Bonitz, Michael

    2012-01-15

    Laser manipulation allows to control the kinetic particle temperature in dusty plasmas. Different methods of laser heating for plasma crystals are benchmarked experimentally. The methods are analyzed with respect to homogeneity and isotropy in a spatial, temporal, and statistical sense. It is shown that it is possible to achieve particle dynamics very close to thermal equilibrium and that laser heating methods allow for a detailed study of phase transitions in finite size systems.

  5. Single-crystal Rare-earth Doped YAG Fiber Lasers Grown by the Laser-heated Pedestal Growth Technique

    DTIC Science & Technology

    2014-02-04

    thulium have been successfully doped into single crystal (SC) yttrium aluminum garnet (YAG, Y3Al5O12) fibers by use of the laser heated pedestal growth...holmium and thulium have been successfully doped into single crystal (SC) yttrium aluminum garnet (YAG, Y3Al5O12) fibers by use of the laser heated...Ann Arbor, MI 48109 dSPAWAR System Center, San Diego, CA ABSTRACT High concentrations of the rare-earth elements erbium, holmium and thulium

  6. Theoretical model for the heat diffusion in an electrically calibrated laser power meter

    NASA Astrophysics Data System (ADS)

    Sporea, Dan G.; Miron, Nicolae; Dumitru, Gabriel; Timus, Bogdan

    1995-09-01

    The theoretical model for the heat diffusion in the case of a high power IR electrically calibrated laser powermeter, developed at the Institute for Atomic Physics in Bucharest, is presented. The IR laser beam falls onto a laser detector, a special design copper disc wafer which absorbs the laser beam, heats its center. A daisy-chain of thermocouple elements having one set of junctions thermally connected to the central region of the disc and the other ones to the disc's boundary is used to detect temperature rise induced by the exposure to the laser beam. For calibration, the copper disc is electrically heated and the electric power that produces the same temperature rise as one induced by an incident laser beam, should equal the laser beam power. The electric heater is designed to provide a uniform heating of the copper disc. The solution for heat diffusion equation was searched as a series of Bessel functions of zero order, the cold junction's temperature was imposed as boundary condition and the heat induced by the laser beam in the disc's center was regarded as input data. To find the correct solutions, there must be taken into account the designing elements of the copper disc: termic material's properties (caloric capacity, termic conductibility), laser detector's geometry, copper's density. The electric power for calibration was injected using a precision power injection circuit which allows a stability of the calibration power, better than 0.1%.

  7. Laser reflector arrangement on H2A-lRE satellite for monitoring spin rate and optical degradation.

    PubMed

    Otsubo, Toshimichi; Kunimori, Hiroo; Yoshihara, Keisuke; Hashimoto, Hidekazu

    2002-09-20

    We devised a unique array of cube-corner reflectors on a spherical satellite so that laser ranging could be used to detect the spin rate and the optical degradation. On the H2A-LRE satellite, there are reflectors made of synthetic silica and ones made of BK7 glass. We report that the degradation of the BK7 reflectors, as well as the spin rate of the satellite, can be monitored through a spectral analysis of laser-ranging data. The center-of-mass correction of the Laser Ranging Equipment satellite was calculated at 210 +/- 10 mm for all possible systems and throughout the degradation process of the BK7 reflectors.

  8. Analysis of heat and mass transfer enhancement in porous material subjected to electric fields (effects of particle sizes and layered arrangement)

    SciTech Connect

    Chaktranond, Chainarong; Rattanadecho, Phadungsak

    2010-11-15

    This research experimentally investigates the influences of electrical voltage, particle sizes and layer arrangement on the heat and mass transfer in porous packed bed subjected to electrohydrodynamic drying. The packed bed consists of a single and double layers of glass beads, water and air. Sizes of glass beads are 0.125 and 0.38 mm in diameter. Electric fields are applied in the range of 0-15 kV. Average velocity and temperature of hot airflow are controlled at 0.33 m/s and 60 C, respectively. The results show that the convective heat transfer coefficient and drying rate are enhanced considerably with a Corona wind. In the single-layered case, due to effects of porosity, the packed bed containing small beads has capillary pressure higher than that with big beads, resulting in higher removal rate of water and higher rate of heat transfer. Considering the effect of capillary pressure difference, temperature distribution and removal rate of moisture in the double-layered case appear to be different than those observed in the single-layered case. Moreover, in the double-layered case, the fine-coarse packed bed gives drying rate higher than that given by the coarse-fine packed bed. (author)

  9. Time differentiated nuclear resonance spectroscopy coupled with pulsed laser heating in diamond anvil cells

    SciTech Connect

    Kupenko, I. Strohm, C.; McCammon, C.; Cerantola, V.; Petitgirard, S.; Dubrovinsky, L.; Glazyrin, K.; Vasiukov, D.; Aprilis, G.; Chumakov, A. I.; Rüffer, R.

    2015-11-15

    Developments in pulsed laser heating applied to nuclear resonance techniques are presented together with their applications to studies of geophysically relevant materials. Continuous laser heating in diamond anvil cells is a widely used method to generate extreme temperatures at static high pressure conditions in order to study the structure and properties of materials found in deep planetary interiors. The pulsed laser heating technique has advantages over continuous heating, including prevention of the spreading of heated sample and/or the pressure medium and, thus, a better stability of the heating process. Time differentiated data acquisition coupled with pulsed laser heating in diamond anvil cells was successfully tested at the Nuclear Resonance beamline (ID18) of the European Synchrotron Radiation Facility. We show examples applying the method to investigation of an assemblage containing ε-Fe, FeO, and Fe{sub 3}C using synchrotron Mössbauer source spectroscopy, FeCO{sub 3} using nuclear inelastic scattering, and Fe{sub 2}O{sub 3} using nuclear forward scattering. These examples demonstrate the applicability of pulsed laser heating in diamond anvil cells to spectroscopic techniques with long data acquisition times, because it enables stable pulsed heating with data collection at specific time intervals that are synchronized with laser pulses.

  10. Small-scale heat detection using catalytic microengines irradiated by laser.

    PubMed

    Liu, Zhaoqian; Li, Jinxing; Wang, Jiao; Huang, Gaoshan; Liu, Ran; Mei, Yongfeng

    2013-02-21

    We demonstrate a novel approach to modulating the motion speed of catalytic microtubular engines via laser irradiation/heating with regard to small-scale heat detection. Laser irradiation on the engines leads to a thermal heating effect and thus enhances the engine speed. During a laser on/off period, the motion behaviour of a microengine can be repeatable and reversible, demonstrating a regulation of motion speeds triggered by laser illumination. Also, the engine velocity exhibits a linear dependence on laser power in various fuel concentrations, which implies an application potential as local heat sensors. Our work may hold great promise in applications such as lab on a chip, micro/nano factories, and environmental detection.

  11. The genome of Trypanosoma cruzi contains a constitutively expressed, tandemly arranged multicopy gene homologous to a major heat shock protein.

    PubMed Central

    Dragon, E A; Sias, S R; Kato, E A; Gabe, J D

    1987-01-01

    cDNA libraries have been constructed in the plasmid vector pUC18 with mRNA isolated from both epimastigotes and trypomastigotes of the Peru strain of Trypanosoma cruzi. Pools of randomly selected clones were analyzed by hybridization-selection-translation. Translation products were immunoprecipitated either with normal human sera or with sera from patients with Chagas' disease (chagasic sera), and the immunoprecipitates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. With this approach, a cDNA clone (pEC5) was identified which encodes a portion of an 85,000-Mr polypeptide. A genomic clone was subsequently isolated (FG1) by using oligonucleotide probes derived from the DNA sequence of this cDNA clone. A portion of this clone was isolated and sequenced, and the coding region for the protein was identified. Computer analysis of the predicted protein sequence indicates that this protein is closely related to the 83,000-Mr heat shock protein (hsp83) of Drosophila melanogaster, the hsp90 of Saccharomyces cerevisiae, and the hsp90 of chicken. This gene is tandemly organized in the T. cruzi genome as a cluster of 6 to 10 copies. Images PMID:3550435

  12. Seal arrangement

    DOEpatents

    Lundholm, Gunnar

    1987-01-01

    A seal arrangement is provided for preventing gas leakage along a reciprocating piston rod or other reciprocating member passing through a wall which separates a high pressure gas chmber and a low pressure gas chamber. Liquid lubricant is applied to the lower pressure side of a sealing gland surrounding the piston rod to prevent the escape of gas between the rod and the gland. The sealing gland is radially forced against the piston rod by action of a plurality of axially stacked O-rings influenced by an axially acting spring as well as pressure from the gas.

  13. The UC2-x - Carbon eutectic: A laser heating study

    NASA Astrophysics Data System (ADS)

    Manara, D.; Boboridis, K.; Morel, S.; De Bruycker, F.

    2015-11-01

    The UC2-x - carbon eutectic has been studied by laser heating and fast multi-wavelength pyrometry under inert atmosphere. The study has been carried out on three compositions, two of which close to the phase boundary of the UC2-x - C miscibility gap (with C/U atomic ratios 2 and 2.1), and one, more crucial, with a large excess of carbon (C/U = 2.82). The first two compositions were synthesised by arc-melting. This synthesis method could not be applied to the last composition, which was therefore completed directly by laser irradiation. The U - C - O composition of the samples was checked by using a combustion method in an ELTRA® analyser. The eutectic temperature, established to be 2737 K ± 20 K, was used as a radiance reference together with the cubic - tetragonal (α → β) solid state transition, fixed at 2050 K ± 20 K. The normal spectral emissivity of the carbon-richer compounds increases up to 0.7, whereas the value 0.53 was established for pure hypostoichiometric uranium dicarbide at the limit of the eutectic region. This increase is analysed in the light of the demixing of excess carbon, and used for the determination of the liquidus temperature (3220 K ± 50 K for UC2.82). Due to fast solid state diffusion, also fostered by the cubic - tetragonal transition, no obvious signs of a lamellar eutectic structure could be observed after quenching to room temperature. The eutectic surface C/UC2-x composition could be qualitatively, but consistently, followed during the cooling process with the help of the recorded radiance spectra. Whereas the external liquid surface is almost entirely constituted by uranium dicarbide, it gets rapidly enriched in demixed carbon upon freezing. Demixed carbon seems to quickly migrate towards the inner bulk during further cooling. At the α → β transition, uranium dicarbide covers again the almost entire external surface.

  14. Laser surface heat treatment of electroless Ni-P-SiC coating on Al356 alloy

    NASA Astrophysics Data System (ADS)

    Hashemi, Sayed Hamid; Shoja-Razavi, Reza

    2016-11-01

    Electroless Ni-P-SiC coatings are recognized for their hardness and wear resistance. In the present study, electroless Ni-P coatings containing SiC particles were co-deposited on Al356 substrate. Laser surface heat treatment was performed using 700 W Nd:YAG pulsed laser. Effects of different laser operating parameters, such as laser scan rate, laser average power and defocusing distance on microstructures were investigated by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). The results of microstructural characterization indicated that the laser treatment under different operating conditions produced composite coating contained nanocrystallined Ni-based matrix with SiC particles Ni3P, Ni12P5, Ni5P2, Ni8P3 precipitates. The microhardness measurements showed that the hardness of the coating was increased up to 60%, due to laser heat treatment, without effect on base metal.

  15. Experiments at high temperature and pressure - Laser heating through the diamond cell

    NASA Technical Reports Server (NTRS)

    Jeanloz, R.; Heinz, D. L.

    1984-01-01

    CW laser heating through a diamond anvil cell by means of a focused Nd:YAG laser has resulted in the achievement of temperatures in the 1500-5000 K range for pressures of 10-100 GPa. Temperatures are determined radiometrically, with an accuracy of about 200 K, and temperature variation across the laser-heated spot is derived by means of spatial filtering with a slit that can be scanned. Melting temperatures are thus determined either on the basis of observed temperature at the liquid-solid interface or on that of the peak temperature at which glass is first produced with increasing laser power.

  16. Experiments at high temperature and pressure - Laser heating through the diamond cell

    NASA Technical Reports Server (NTRS)

    Jeanloz, R.; Heinz, D. L.

    1984-01-01

    CW laser heating through a diamond anvil cell by means of a focused Nd:YAG laser has resulted in the achievement of temperatures in the 1500-5000 K range for pressures of 10-100 GPa. Temperatures are determined radiometrically, with an accuracy of about 200 K, and temperature variation across the laser-heated spot is derived by means of spatial filtering with a slit that can be scanned. Melting temperatures are thus determined either on the basis of observed temperature at the liquid-solid interface or on that of the peak temperature at which glass is first produced with increasing laser power.

  17. Laser heating of an absorbing and conducting media applied to laser flash property measurements

    SciTech Connect

    Gritzo, L.A.; Anderson, E.E.

    1993-12-31

    The laser flash technique is widely used for determining the thermal diffusivity of a sample. In this work, the temperature distribution throughout the sample is investigated, identifying localized, highly-heated regions near the front surface of the sample as a function of: (1) pulse duration, (2) incident beam uniformity, and (3) sample opacity. These high-temperature regions result in an increase in the uncertainty due to temperature-dependent properties, an increase in the heat loss from the sample, and an increased risk of sample damage. The temperature within a semi-transparent media is also investigated in order to establish a regime for which the media can reasonably be considered as opaque. This analysis illustrates that, for same total energy deposition, treatment of the incident energy as a continuous heat source, as opposed to an infinitesimal pulse of energy, results in a factor of 2 increase in the front surface temperature during heating. Also, for the same total energy deposition and approximate beam size, use of a Gaussian intensity distribution increases the front surface temperature during heating by more than a factor of 2 as compared to the use of a uniform temperature distribution. By analyzing the front surface temperature of an absorbing and conducting semi-transparent sample subjected to a Gaussian intensity distribution, it is concluded that the media can be treated as opaque, (i.e. the energy can be applied as a boundary condition) for {var_epsilon} = kd > 50, where k is the extinction coefficient and d is the beam diameter. For materials with a sufficiently small absorption coefficient and thermal diffusivity, a closed-form solution suitable for design use is presented for the front-surface temperature at a location coincident with the beam centerline.

  18. Thermal effects and upconversion in the Er3+:YAG solid-state heat-capacity laser

    NASA Astrophysics Data System (ADS)

    Eichhorn, Marc

    2010-10-01

    Although seen as nearly being impossible to realize, a quasi-three-level laser medium can be used in heat-capacity operation. In this operation mode, the laser medium is not cooled during lasing in order to avoid strong thermal lensing, which, in actively cooled operation, would result in a low beam quality or would even destabilize the laser cavity. Thus, in heat-capacity mode, the laser medium will substantially heat up during operation, which will cause an increase in re-absorption for a quasi-three-level laser medium, resulting in a general drop in output power over time. However, laser power, temperature rise, fluorescence and inversion are coupled by the temperaturedependent spectroscopic properties of the laser medium in a complex way. This paper presents an investigation on these thermal effects and upconversion in the resonantly pumped Er3+:YAG solid-state heat-capacity laser (SSHCL) system. These effects are important for the scaling properties on this laser towards medium- or high-energy systems, and to obtain a good beam quality from the laser itself. It is shown that the expected power drop of this quasi-three-level medium due to the rise in crystal temperature is very low, allowing for high-power operation on substantial time scales. The experimental results and the theoretical background will be explained in detail. The effect of fluorescence re-absorption on the laser properties, especially on threshold and laser efficiency will also be discussed. This fluorescence re-pumping, applicable in general to a large variety of lasers, can drastically increase the output power and thus laser efficiency at a given pump power. Up to 125 W and 89 J in 2 s are achieved using optimized doping levels for upconversion reduction.

  19. Energy coupling and plume dynamics during high power laser heating of metals

    SciTech Connect

    Jeong, S. |

    1997-05-01

    High power laser heating of metals was studied utilizing experimental and numerical methods with an emphasis on the laser energy coupling with a target and on the dynamics of the laser generated vapor flow. Rigorous theoretical modeling of the heating, melting, and evaporation of metals due to laser radiation with a power density below the plasma shielding threshold was carried out. Experimentally, the probe beam deflection technique was utilized to measure the propagation of a laser induced shock wave. The effects of a cylindrical cavity in a metal surface on the laser energy coupling with a solid were investigated utilizing photothermal deflection measurements. A numerical calculation of target temperature and photothermal deflection was performed to compare with the measured results. Reflection of the heating laser beam inside the cavity was found to increase the photothermal deflection amplitude significantly and to enhance the overall energy coupling between a heating laser beam and a solid. Next, unsteady vaporization of metals due to nanosecond pulsed laser heating with an ambient gas at finite pressure was analyzed with a one dimensional thermal evaporation model for target heating and one dimensional compressible flow equations for inviscid fluid for the vapor flow. Lastly, the propagation of a shock wave during excimer laser heating of aluminum was measured with the probe beam deflection technique. The transit time of the shock wave was measured at the elevation of the probe beam above the target surface; these results were compared with the predicted behavior using ideal blast wave theory. The propagation of a gaseous material plume was also observed from the deflection of the probe beam at later times.

  20. Welding of Semiconductor Nanowires by Coupling Laser-Induced Peening and Localized Heating

    NASA Astrophysics Data System (ADS)

    Rickey, Kelly M.; Nian, Qiong; Zhang, Genqiang; Chen, Liangliang; Suslov, Sergey; Bhat, S. Venkataprasad; Wu, Yue; Cheng, Gary J.; Ruan, Xiulin

    2015-11-01

    We demonstrate that laser peening coupled with sintering of CdTe nanowire films substantially enhances film quality and charge transfer while largely maintaining basic particle morphology. During the laser peening phase, a shockwave is used to compress the film. Laser sintering comprises the second step, where a nanosecond pulse laser beam welds the nanowires. Microstructure, morphology, material content, and electrical conductivities of the films are characterized before and after treatment. The morphology results show that laser peening can decrease porosity and bring nanowires into contact, and pulsed laser heating fuses those contacts. Multiphysics simulations coupling electromagnetic and heat transfer modules demonstrate that during pulsed laser heating, local EM field enhancement is generated specifically around the contact areas between two semiconductor nanowires, indicating localized heating. The characterization results indicate that solely laser peening or sintering can only moderately improve the thin film quality; however, when coupled together as laser peen sintering (LPS), the electrical conductivity enhancement is dramatic. LPS can decrease resistivity up to a factor of ~10,000, resulting in values on the order of ~105 Ω-cm in some cases, which is comparable to CdTe thin films. Our work demonstrates that LPS is an effective processing method to obtain high-quality semiconductor nanocrystal films.

  1. Welding of Semiconductor Nanowires by Coupling Laser-Induced Peening and Localized Heating

    PubMed Central

    Rickey, Kelly M.; Nian, Qiong; Zhang, Genqiang; Chen, Liangliang; Suslov, Sergey; Bhat, S. Venkataprasad; Wu, Yue; Cheng, Gary J.; Ruan, Xiulin

    2015-01-01

    We demonstrate that laser peening coupled with sintering of CdTe nanowire films substantially enhances film quality and charge transfer while largely maintaining basic particle morphology. During the laser peening phase, a shockwave is used to compress the film. Laser sintering comprises the second step, where a nanosecond pulse laser beam welds the nanowires. Microstructure, morphology, material content, and electrical conductivities of the films are characterized before and after treatment. The morphology results show that laser peening can decrease porosity and bring nanowires into contact, and pulsed laser heating fuses those contacts. Multiphysics simulations coupling electromagnetic and heat transfer modules demonstrate that during pulsed laser heating, local EM field enhancement is generated specifically around the contact areas between two semiconductor nanowires, indicating localized heating. The characterization results indicate that solely laser peening or sintering can only moderately improve the thin film quality; however, when coupled together as laser peen sintering (LPS), the electrical conductivity enhancement is dramatic. LPS can decrease resistivity up to a factor of ~10,000, resulting in values on the order of ~105 Ω-cm in some cases, which is comparable to CdTe thin films. Our work demonstrates that LPS is an effective processing method to obtain high-quality semiconductor nanocrystal films. PMID:26527570

  2. Research and application of surface heat treatment for multipulse laser ablation of materials

    NASA Astrophysics Data System (ADS)

    Cai, Song; Chen, Genyu; Zhou, Cong

    2015-11-01

    This study analysed a laser ablation platform and built heat transfer equations for multipulse laser ablation of materials. The equations include three parts: laser emission after the material melt and gasification; end of laser emission after the material melts and there is the presence of a super-hot layer and solid-phase heat transfer changes during material ablation. For each of the three parts, the effects of evaporation, plasma shielding and energy accumulation under the pulse interval were considered. The equations are reasonable, and all the required parameters are only related to the laser parameters and material properties, allowing the model to have a certain versatility and practicability. The model was applied for numerical simulation of the heat transfer characteristics in the multipulse laser ablation of bronze and diamond. Next, experiments were conducted to analyse the topography of a bronze-bonded diamond grinding wheel after multipulse laser ablation. The theoretical analysis and experimental results showed that multipulse laser can merge the truing and dressing on a bronze-bonded diamond grinding wheel. This study provides theoretical guidance for optimising the process parameters in the laser ablation of a bronze-bonded diamond grinding wheel. A comparative analysis showed that the numerical solution to the model is in good agreement with the experimental data, thus verifying the correctness and feasibility of the heat transfer model.

  3. Bone tissue heating and ablation by short and ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Letfullin, Renat R.; Rice, Colin E. W.; George, Thomas F.

    2010-02-01

    Biological hard tissues, such as those found in bone and teeth, are complex tissues that build a strong mineral structure over an organic matrix framework. The laser-matter interaction for bone hard tissues holds great interest to laser surgery and laser dentistry; the use of short/ultrashort pulses, in particular, shows interesting behaviors not seen in continuous wave lasers. High laser energy densities in ultrashort pulses can be focused on a small irradiated surface (spot diameter is 10-50 μm) leading to rapid temperature rise and thermal ablation of the bone tissue. Ultrashort pulses, specifically those in the picosecond and femtosecond ranges, impose several challenges in modeling bone tissue response. In the present paper we perform time-dependent thermal simulations of short and ultrashort pulse laser-bone interactions in singlepulse and multipulse (set of ultrashort pulses) modes of laser heating. A comparative analysis for both radiation modes is discussed for laser heating of different types of the solid bone on the nanosecond, picosecond and femtosecond time scales. It is shown that ultrashort laser pulses with high energy densities can ablate bone tissue without heating tissues bordering the ablation creator. This reaction is particularly desirable as heat accumulation and thermal damage are the main factors affecting tissue regrowth rates, and thus patient recovery times.

  4. An inductively heated hot cavity catcher laser ion source

    NASA Astrophysics Data System (ADS)

    Reponen, M.; Moore, I. D.; Pohjalainen, I.; Rothe, S.; Savonen, M.; Sonnenschein, V.; Voss, A.

    2015-12-01

    An inductively heated hot cavity catcher has been constructed for the production of low-energy ion beams of exotic, neutron-deficient Ag isotopes. A proof-of-principle experiment has been realized by implanting primary 107Ag21+ ions from a heavy-ion cyclotron into a graphite catcher. A variable-thickness nickel foil was used to degrade the energy of the primary beam in order to mimic the implantation depth expected from the heavy-ion fusion-evaporation recoils of N = Z 94Ag. Following implantation, the silver atoms diffused out of the graphite and effused into the catcher cavity and transfer tube, where they were resonantly laser ionized using a three-step excitation and ionization scheme. Following mass separation, the ions were identified by scanning the frequency of the first resonant excitation step while recording the ion count rate. Ion release time profiles were measured for different implantation depths and cavity temperatures with the mean delay time varying from 10 to 600 ms. In addition, the diffusion coefficients for silver in graphite were measured for temperatures of 1470 K, 1630 K, and 1720 K, from which an activation energy of 3.2 ± 0.3 eV could be determined.

  5. An inductively heated hot cavity catcher laser ion source

    SciTech Connect

    Reponen, M.; Moore, I. D. Pohjalainen, I.; Savonen, M.; Voss, A.; Rothe, S.; Sonnenschein, V.

    2015-12-15

    An inductively heated hot cavity catcher has been constructed for the production of low-energy ion beams of exotic, neutron-deficient Ag isotopes. A proof-of-principle experiment has been realized by implanting primary {sup 107}Ag{sup 21+} ions from a heavy-ion cyclotron into a graphite catcher. A variable-thickness nickel foil was used to degrade the energy of the primary beam in order to mimic the implantation depth expected from the heavy-ion fusion-evaporation recoils of N = Z {sup 94}Ag. Following implantation, the silver atoms diffused out of the graphite and effused into the catcher cavity and transfer tube, where they were resonantly laser ionized using a three-step excitation and ionization scheme. Following mass separation, the ions were identified by scanning the frequency of the first resonant excitation step while recording the ion count rate. Ion release time profiles were measured for different implantation depths and cavity temperatures with the mean delay time varying from 10 to 600 ms. In addition, the diffusion coefficients for silver in graphite were measured for temperatures of 1470 K, 1630 K, and 1720 K, from which an activation energy of 3.2 ± 0.3 eV could be determined.

  6. Warm dense matter created by isochoric laser heating

    NASA Astrophysics Data System (ADS)

    Ping, Y.; Correa, A. A.; Ogitsu, T.; Draeger, E.; Schwegler, E.; Ao, T.; Widmann, K.; Price, D. F.; Lee, E.; Tam, H.; Springer, P. T.; Hanson, D.; Koslow, I.; Prendergast, D.; Collins, G.; Ng, A.

    2010-06-01

    Warm Dense Matter (WDM) physics has been a growing field of high energy density physics, driven by the fundamental urge to understand the convergence between plasma and condensed matter physics, and the practical need to understand dynamic behavior of materials under extreme conditions. A platform for creating and probing WDM by isochoric heating of free-standing nano-foils has been developed recently to study the non-equilibrium processes. Results of optical measurements reveal the existence of a quasi-steady state in the time history, during which the interband component of the dielectric function shows both enhancement and a red shift. First-principles calculations of the dielectric function suggest that the enhanced red shift of the interband transition peak might be explained by a positive charge state of the gold foil due to ejection of electrons by the high intensity laser pulse. The impact on optical properties by the formation of an electronic sheath was examined by the Thomas-Fermi theory with local equilibrium approximation.

  7. Characterization of Heat-Wave Propagation through Laser-Driven Ti-Doped Underdense Plasma

    SciTech Connect

    Tanabe, M; Nishimura, H; Ohnishi, N; Fournier, K B; Fujioka, S; Iwamae, A; Hansen, S B; Nagai, K; Girard, F; Primout, M; Villette, B; Brebion, D; Mima, K

    2009-02-23

    The propagation of a laser-driven heat-wave into a Ti-doped aerogel target was investigated. The temporal evolution of the electron temperature was derived by means of Ti K-shell x-ray spectroscopy, and compared with two-dimensional radiation hydrodynamic simulations. Reasonable agreement was obtained in the early stage of the heat-wave propagation. In the later phase, laser absorption, the propagation of the heat wave, and hydrodynamic motion interact in a complex manner, and the plasma is mostly re-heated by collision and stagnation at the target central axis.

  8. Continuum-atomistic simulation of picosecond laser heating of copper with electron heat capacity from ab initio calculation

    NASA Astrophysics Data System (ADS)

    Ji, Pengfei; Zhang, Yuwen

    2016-03-01

    On the basis of ab initio quantum mechanics (QM) calculation, the obtained electron heat capacity is implemented into energy equation of electron subsystem in two temperature model (TTM). Upon laser irradiation on the copper film, energy transfer from the electron subsystem to the lattice subsystem is modeled by including the electron-phonon coupling factor in molecular dynamics (MD) and TTM coupled simulation. The results show temperature and thermal melting difference between the QM-MD-TTM integrated simulation and pure MD-TTM coupled simulation. The successful construction of the QM-MD-TTM integrated simulation provides a general way that is accessible to other metals in laser heating.

  9. Gas cooler arrangement

    SciTech Connect

    Zabelka, J.

    1985-01-15

    The gas cooler arrangement includes a first pressure vessel in which heat is yielded by radiation and a following convection gas cooler. The pressure vessel of the convection gas cooler includes a faller flue and at least one riser flue for cooling the gas. The flues comprise heat-removing tubes which are parts of a steam generator. The bottom of the pressure vessel contains an ash collection chamber which is connected to the ends of the flues and which can be emptied via a suitable closure element.

  10. Porcine cadaver iris model for iris heating during corneal surgery with a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Fan, Zhongwei; Wang, Jiang; Yan, Ying; Juhasz, Tibor; Kurtz, Ron

    2015-03-01

    Multiple femtosecond lasers have now been cleared for use for ophthalmic surgery, including for creation of corneal flaps in LASIK surgery. Preliminary study indicated that during typical surgical use, laser energy may pass beyond the cornea with potential effects on the iris. As a model for laser exposure of the iris during femtosecond corneal surgery, we simulated the temperature rise in porcine cadaver iris during direct illumination by the femtosecond laser. Additionally, ex-vivo iris heating due to femtosecond laser irradiation was measured with an infrared thermal camera (Fluke corp. Everett, WA) as a validation of the simulation.

  11. Femtosecond laser heat affected zones profiled in Co/Si multilayer thin films

    SciTech Connect

    Picard, Yoosuf N.; Yalisove, Steven M.

    2008-01-07

    In this letter, we describe an approach for assessing collateral thermal damage resulting from high intensity, femtosecond laser irradiation. Polycrystalline Co thin films deposited on Si (100) substrates and buried under an amorphous Si film were prepared for plan-view transmission electron microscopy (TEM) prior to laser irradiation by femtosecond laser pulses. A heat affected zone (HAZ) resulting from single pulse irradiation at a fluence of 0.9 J/cm{sup 2} was determined by TEM imaging and point-wise selected area diffraction. The spatially Gaussian laser pulse generated a HAZ extending up to 3 {mu}m radially from the femtosecond laser irradiated region.

  12. Thermal denaturation of egg protein under nanosecond pulsed laser heating of gold nanoparticles

    SciTech Connect

    Meshalkin, Yu P; Lapin, I N; Svetlichnyi, Valery A

    2011-08-31

    Thermal denaturation of egg protein in the presence of gold nanoparticles via their heating at the plasmon resonance wavelength by the pulsed radiation of the second harmonic of an Nd:YAG laser (532 nm) is investigated. The experimental dependence of the protein denaturation time on the mean laser power is obtained. The heating temperature of the medium with gold nanoparticles is calculated. The numerical estimates of the temperature of the heated medium containing protein and gold nanoparticles (45.3 deg. C at the moment of protein denaturation) are in good agreement with the literature data on its thermal denaturation and with the data of pyrometric measurements (42.0 {+-} 1.5 deg. C). The egg protein may be successfully used to investigate the specific features of laser heating of proteins in the presence of metal nanoparticles under their excitation at the plasmon resonance wavelength. (laser methods in biology)

  13. Investigation of laser heating effect of metallic nanoparticles on cancer treatment

    NASA Astrophysics Data System (ADS)

    Shan, G. S.; Liu, X. M.; Chen, H. J.; Yu, J. S.; Chen, X. D.; Yao, Y.; Qi, L. M.; Chen, Z. J.

    2016-07-01

    Metallic nanoparticles can be applied for hyperthermia therapy of cancer treatment to enhance the efficacy because of their high absorption rate. The absorption of laser energy by metallic nanoparticles is strongly dependent on the concentration, shape, material of nanoparticles and the wavelength of the laser. However, there is no systematic investigation on the heating effect involving different material, concentration and laser wavelength. In this paper, gold nanoparticles (AuNPs), sliver nanoparticles (AgNPs) and sliver nanowires (AgNWs) with different concentrations are heated by 450nm and 532nm wavelength laser to investigate the heating effect. The result shows that the temperature distribution of heated metallic nanoparticles is non-uniform.

  14. Laser-enhanced high-intensity focused ultrasound heating in an in vivo small animal model

    NASA Astrophysics Data System (ADS)

    Jo, Janggun; Yang, Xinmai

    2016-11-01

    The enhanced heating effect during the combination of high-intensity focused ultrasound (HIFU) and low-optical-fluence laser illumination was investigated by using an in vivo murine animal model. The thighs of murine animals were synergistically irradiated by HIFU and pulsed nano-second laser light. The temperature increases in the target region were measured by a thermocouple under different HIFU pressures, which were 6.2, 7.9, and 9.8 MPa, in combination with 20 mJ/cm2 laser exposures at 532 nm wavelength. In comparison with conventional laser therapies, the laser fluence used here is at least one order of magnitude lower. The results showed that laser illumination could enhance temperature during HIFU applications. Additionally, cavitation activity was enhanced when laser and HIFU irradiation were concurrently used. Further, a theoretical simulation showed that the inertial cavitation threshold was indeed decreased when laser and HIFU irradiation were utilized concurrently.

  15. Direct evidence of strongly inhomogeneous energy deposition in target heating with laser-produced ion beams

    SciTech Connect

    Brambrink, E.; Audebert, P.; Schlegel, T.; Malka, G.; Aleonard, M. M.; Claverie, G.; Gerbaux, M.; Gobet, F.; Hannachi, F.; Scheurer, J. N.; Tarisien, M.; Amthor, K. U.; Meot, V.; Morel, P.

    2007-06-15

    We report on strong nonuniformities in target heating with intense, laser-produced proton beams. The observed inhomogeneity in energy deposition can strongly perturb equation of state (EOS) measurements with laser-accelerated ions which are planned in several laboratories. Interferometric measurements of the target expansion show different expansion velocities on the front and rear surfaces, indicating a strong difference in local temperature. The nonuniformity indicates at an additional heating mechanism, which seems to originate from electrons in the keV range.

  16. Direct evidence of strongly inhomogeneous energy deposition in target heating with laser-produced ion beams.

    PubMed

    Brambrink, E; Schlegel, T; Malka, G; Amthor, K U; Aléonard, M M; Claverie, G; Gerbaux, M; Gobet, F; Hannachi, F; Méot, V; Morel, P; Nicolai, P; Scheurer, J N; Tarisien, M; Tikhonchuk, V; Audebert, P

    2007-06-01

    We report on strong nonuniformities in target heating with intense, laser-produced proton beams. The observed inhomogeneity in energy deposition can strongly perturb equation of state (EOS) measurements with laser-accelerated ions which are planned in several laboratories. Interferometric measurements of the target expansion show different expansion velocities on the front and rear surfaces, indicating a strong difference in local temperature. The nonuniformity indicates at an additional heating mechanism, which seems to originate from electrons in the keV range.

  17. Surface heating of electrons in atomic clusters irradiated by ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Krainov, V. P.; Sofronov, A. V.

    2014-04-01

    We consider a mechanism for electron heating in atomic clusters at the reflections of free electrons from the cluster surface. Electrons acquire energy from the external laser field during these reflections. A simple analytical expression has been obtained for acquired electron kinetic energy during the laser pulse. We find conditions when this mechanism dominates compared to the electron heating due to the well-known induced inverse bremsstrahlung at the electron-ion collisions inside clusters.

  18. Effects of the arrangement of triangle-winglet-pair vortex generators on heat transfer performance of the shell side of a double-pipe heat exchanger enhanced by helical fins

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Shang, Bojun; Meng, Huibo; Li, Yaxia; Wang, Cuihua; Gong, Bin; Wu, Jianhua

    2017-01-01

    To improve heat transfer performance of the shell side of a double-pipe heat exchanger enhanced by helical fins, triangle-winglet-pair vortex generators (VG) were installed along the centerline of the helical channel with rectangular cross section. The effects of the arrangement of the triangle-winglet-pair VG, such as the geometry, the angle of attack and the quantity on heat transfer performance and pressure drop characteristics have been investigated experimentally to find out the optimal design of the VG. Air was used as working fluid within the range of Re from 680 to 16,000. The results show that, the heat exchange effectiveness of the shell side with VG is 16.6 % higher than that without VG. The vortices and the unsteadiness of the flow introduced by the VG make a great contribution to the increase. Under identical pressure drop condition, the angle of attack of 30° is the best choice compared with 45° and 60°. Under the three constraints, i.e., identical mass flow rate, identical pressure drop and identical pumping power, the largest VG size can achieve the best enhancement effect. Installation of three pairs of VG within one pitch is an optimal design for the shell side used in the present experiments. The enhancement effect of isosceles right triangle is better than that of right triangle in which one acute angle is 30°.

  19. Processing constraints resulting from heat accumulation during pulsed and repetitive laser materials processing.

    PubMed

    Weber, Rudolf; Graf, Thomas; Freitag, Christian; Feuer, Anne; Kononenko, Taras; Konov, Vitaly I

    2017-02-20

    In any pulsed and repetitive laser process a part of the absorbed laser energy is thermalized and stays in the material as residual heat. This residual heat is accumulating from pulse to pulse, continuously increasing the temperature, if the time between two pulses does not allow the material to sufficiently cool down. Controlling this so-called heat accumulation is one of the major challenges for materials processing with high average power pulsed lasers and repetitive processing. Heat accumulation caused by subsequent pulses (HAP) on the same spot and heat accumulation caused by subsequent scans (HAS) over the same spot can significantly reduce process quality, e.g., when the temperature increase caused by heat accumulation exceeds the melting temperature. In both cases, HAS and HAP, it is of particular interest to know the limiting number of pulses or scans after which the heat accumulation temperature exceeds a critical temperature and a pause has to be introduced. Approximation formulas for the case, where the duration of the heat input is short compared to the time between two subsequent heat inputs are derived in this paper, providing analytical scaling laws for the heat accumulation as a function of the processing parameters. The validity of these approximations is confirmed for HAP with an example of surface ablation of CrNi-steel and for HAS with multi-scan cutting of carbon fiber reinforced plastics (CFRP), both with a picosecond laser at an average power of up to 1.1 kW. It is shown that for the important case of 1-dimensional heat flow the limiting number of heat inputs decreases with the inverse of the square of the average laser power.

  20. Laser heated high density fluids probed by coherent anti-Stokes Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Baer, Bruce J.; Yoo, Choong-Shik

    2005-01-01

    We describe experiments integrating coherent anti-Stokes Raman spectroscopy (CARS), laser-heating and diamond-anvil cell (DAC) technologies for probing molecular vibrations of transparent molecular fluids at the pressure-temperature conditions of energetic detonation and interiors of giant planets. In these experiments, we use a microfabricated metal toroid and a cw Nd:YLF laser to conductively heat a surrounding transparent sample in a DAC. The laser is operated at a TEM01* mode to match the shape of the toroid and thus produces a uniform heating area. The CARS probe utilizes two pulsed lasers with similar cavity lengths: a commercial narrow-band mode-locked Q-switched Nd:YAG laser and a homebuilt broadband dye laser. A strong CARS signal is then produced from the sample in the central region of laser-heated metal toroid where the two laser pulses spatially and temporally coincide. In this article, we demonstrate that this technique is capable of producing high quality vibrational spectra from nitrogen fluid above 2000 K and 13 GPa, where the application of spontaneous Raman spectroscopy is limited because of intense thermal radiation.

  1. Survey of research and applications of laser heat treatment in China

    NASA Astrophysics Data System (ADS)

    Qian, Hongbin; Su, Baorong

    1996-09-01

    This paper reports the fruits of the research on fundamental theory, application basis and application of laser heat treatment since 1979 in China. Also the technical development and spreading of laser heat treatment is reported. Over 20 academic exchange activities home or abroad were organized by our country. In China, there are near 1,000 units and about 5,000 intermediate and senior scientists and engineers engaged in the research, development and production of laser heat treatment. More than 3,000 academia articles have been published home and abroad. About 2,000 Bachelors, Masters and Doctors whose major is laser application have been cultivated. In domestic plants, near 1,000 production lines of laser heat treatment on the cylinder bodies and covers of automobiles and tractors have been set up, which were deeply welcomed by the automobile makers and repairmen. There are other production lines running in some factories and making good effects, such as laser glazing production line for steel ring, laser quenching production line for master reed in elastic shaft coupling and laser quenching production line for big gears, etc.

  2. Laser Heated High Density Fluids Probed by Coherent Anti-Stokes Raman Spectroscopy

    SciTech Connect

    Baer, B J; Yoo, C

    2004-05-19

    We describe an integrated experimental method of Coherent Antistoke Raman Spectroscopy (CARS), laser-heating and diamond-anvil cell (DAC) technologies probing molecular vibrations of transparent molecular fluids at the pressure-temperature conditions of energetic detonation and Giant planetary interiors. In this method, we use a microfabricated metal toroid to conductively heat a surrounding transparent sample in a DAC, using a CW Nd:YLF laser. The laser is operated at a TEM{sub 01*} mode to match the shape of the toroid and thus produces a uniform heating area. The CARS probe utilizes two pulsed lasers with similar cavity lengths: a commercial narrow-band mode-locked Q-switched Nd:YAG laser and a home-built broadband dye laser. A strong CARS signal is then produced from the sample in the central region of laser-heated metal toroid where the two laser pulses spatially and temporally coincide. In this paper, we will demonstrate that this technique is capable of producing high quality vibrational spectra from nitrogen fluid above 2000 K and 13 GPa, where the application of spontaneous Raman spectroscopy is limited because of intense thermal radiation.

  3. Heat generation during ablation of porcine skin with erbium:YAG laser vs a novel picosecond infrared laser.

    PubMed

    Jowett, Nathan; Wöllmer, Wolfgang; Mlynarek, Alex M; Wiseman, Paul; Segal, Bernard; Franjic, Kresimir; Krötz, Peter; Böttcher, Arne; Knecht, Rainald; Miller, R J Dwayne

    2013-08-01

    Despite significant advances in surgery, most surgical tools remain basic. Lasers provide a means of precise surgical ablation, but their clinical use has remained limited because of undesired thermal, ionizing, or acoustic stress effects leading to tissue injury. A novel ultrafast, nonionizing, picosecond infrared laser (PIRL) system has recently been developed and is capable, in theory, of ablation with negligible thermal or acoustic stress effects. To measure and compare heat generation by means of thermography during ablation of ex vivo porcine skin by conventional microsecond-pulsed erbium:YAG (Er:YAG) laser and picosecond infrared laser (PIRL). This study was conducted in an optics laboratory and used a pretest-posttest experimental design comparing 2 methods of laser ablation of tissue with each sample acting as its own control. Ex vivo porcine skin was ablated in a 5-mm line pattern with both Er:YAG laser and PIRL at fluence levels marginally above ablation threshold (2 J/cm² and 0.6 J/cm², respectively). Peaks and maxima of skin temperature rises were determined using a thermography camera. Means of peak temperature rises were compared using the paired sample t test. Ablation craters were assessed by means of digital microscopy. RESULTS Mean peak rise in skin surface temperature for the Er:YAG laser and PIRL was 15.0°C and 1.68°C, respectively (P < .001). Maximum peak rise in skin surface temperature was 18.85°C for the Er:YAG laser and 2.05°C for the PIRL. Ablation craters were confirmed on digital microscopy. Picosecond infrared laser ablation results in negligible heat generation, considerably less than Er:YAG laser ablation, which confirms the potential of this novel technology in minimizing undesirable thermal injury associated with lasers currently in clinical use.

  4. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum

    SciTech Connect

    Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.; Smith, R. Scott; Joly, Alan G.; Tonkyn, Russell G.; Kay, Bruce D.; Kimmel, Greg A.

    2016-04-26

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond timescale in ultrahigh vacuum (UHV). Details of the design, implementation and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ~1010 K/s for temperature increases of ~100 – 200 K are obtained. Subsequent rapid cooling (~5 × 109 K/s) quenches the film, permitting in-situ, post-mortem analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ~ ± 3% leading to a temperature uncertainty of ~ ± 5 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.

  5. Numerical investigation of mixed convection heat transfer from two isothermal circular cylinders in tandem arrangement: buoyancy, spacing ratio, and confinement effects

    NASA Astrophysics Data System (ADS)

    Salcedo, Erick; Cajas, Juan C.; Treviño, César; Martínez-Suástegui, Lorenzo

    2016-11-01

    This paper presents a two-dimensional numerical study for mixed convection in a laminar cross-flow with a pair of stationary equal-sized isothermal cylinders in tandem arrangement confined in a channel. The governing equations are solved using the control volume method on a nonuniform orthogonal Cartesian grid, and the immersed boundary method is employed to identify the cylinders placed in the flow field. The numerical scheme is first validated against standard cases of symmetrically confined isothermal circular cylinders in plane channels, and grid convergence tests were also examined. The objective of the present study was to investigate the influence of buoyancy and the blockage ratio constraint on the flow and heat transfer characteristics of the immersed cylinder array. Using a fixed Reynolds number based on cylinder diameter of ReD = 200 , a fixed value of the Prandtl number of Pr = 7 , and a blockage ratio of D/H = 0.2 , all possible flow regimes are considered by setting the longitudinal spacing ratio (σ = L/D ) between the cylinder axes to 2, 3, and 5 for values of the buoyancy parameter (Richardson number) in the range -1≤ Ri≤ 4 . The interference effects and complex flow features are presented in the form of mean and instantaneous velocity, vorticity, and temperature distributions. The results demonstrate how the buoyancy, spacing ratio, and wall confinement affect the wake structure and vortex dynamics. In addition, local and average heat transfer characteristics of both cylinders are comprehensively presented for a wide range in the parametric space.

  6. Numerical investigation of mixed convection heat transfer from two isothermal circular cylinders in tandem arrangement: buoyancy, spacing ratio, and confinement effects

    NASA Astrophysics Data System (ADS)

    Salcedo, Erick; Cajas, Juan C.; Treviño, César; Martínez-Suástegui, Lorenzo

    2017-04-01

    This paper presents a two-dimensional numerical study for mixed convection in a laminar cross-flow with a pair of stationary equal-sized isothermal cylinders in tandem arrangement confined in a channel. The governing equations are solved using the control volume method on a nonuniform orthogonal Cartesian grid, and the immersed boundary method is employed to identify the cylinders placed in the flow field. The numerical scheme is first validated against standard cases of symmetrically confined isothermal circular cylinders in plane channels, and grid convergence tests were also examined. The objective of the present study was to investigate the influence of buoyancy and the blockage ratio constraint on the flow and heat transfer characteristics of the immersed cylinder array. Using a fixed Reynolds number based on cylinder diameter of ReD = 200, a fixed value of the Prandtl number of Pr = 7, and a blockage ratio of D/H = 0.2, all possible flow regimes are considered by setting the longitudinal spacing ratio (σ = L/D) between the cylinder axes to 2, 3, and 5 for values of the buoyancy parameter (Richardson number) in the range -1≤ Ri≤ 4. The interference effects and complex flow features are presented in the form of mean and instantaneous velocity, vorticity, and temperature distributions. The results demonstrate how the buoyancy, spacing ratio, and wall confinement affect the wake structure and vortex dynamics. In addition, local and average heat transfer characteristics of both cylinders are comprehensively presented for a wide range in the parametric space.

  7. Effect of Pulsed Laser Ablation and Continuous Laser Heating on the Adhesion and Cohesion of Cold Sprayed Ti-6Al-4V Coatings

    NASA Astrophysics Data System (ADS)

    Perton, M.; Costil, S.; Wong, W.; Poirier, D.; Irissou, E.; Legoux, J.-G.; Blouin, A.; Yue, S.

    2012-12-01

    The individual and cumulative effects of in situ pulsed laser ablation and continuous laser pre-heating on adhesion and cohesion strength of cold sprayed Ti-6Al-4V coatings are investigated. Laser beams were coupled to a cold spray gun in order to ablate and pre-heat the substrate surface a few milliseconds prior to the impact of the spray particles. Cohesion and adhesion strength were evaluated by scratch test, standard ASTM C633 pull test and laser shock (LASAT) technique. The effects of laser ablation before and during cold spray operations were investigated. Results demonstrate that laser ablation of the substrate before cold spraying led to a smooth surface which improved adhesion strength. However, when laser ablation was maintained throughout the cold spray process, i.e., in between the coating layers, a reduction of cohesion and adhesion was observed. These negative effects were circumvented when laser ablation and laser pre-heating were combined.

  8. Heating dynamics and extreme ultraviolet radiation emission of laser-produced Sn plasmas

    SciTech Connect

    Yuspeh, S.; Sequoia, K. L.; Tao, Y.; Tillack, M. S.; Burdt, R. A.; Najmabadi, F.

    2010-06-28

    The impact of 1.064 mum laser absorption depth on the heating and in-band (2% bandwidth) 13.5 nm extreme ultraviolet emissions in Sn plasmas is investigated experimentally and numerically. In-band emission lasting longer than the laser pulse and separation between the laser absorption and in-band emission region are observed. Maximum efficiency is achieved by additional heating of the core of the plasma to allow the optimal temperature to expand to a lower and more optically thin density. This leads to higher temperature plasma that emits less in-band light as compared to CO{sub 2} produced plasma sources for the same application.

  9. Very high temperature laser heated furnace for Knudsen cell mass spectrometry

    SciTech Connect

    Colle, Jean-Yves; Capone, Franco

    2008-05-15

    A very high temperature furnace (up to 3000 deg. C) for the Knudsen cell mass spectrometry (KCMS) based on a laser heating technique has been developed. It is demonstrated that this system overcomes some of the typical technological problems encountered by the standard methods and can be more easily handled in special environments such as gloveboxes or hot cells. This paper describes the laser heated KCMS general design. The technology of the laser furnace along with its advantages, disadvantages, and applications is presented. Mechanical designs, some technical details, and the importance of the temperature control are also discussed.

  10. Mixed field dosimetry using focused and unfocused laser heating of thermoluminescent materials

    SciTech Connect

    Han, Seungjae

    1994-03-01

    The incidents at the Three Mile Island and Chernobyl have triggered the need for better personnel dosimetry methods in mixed radiation fields. This thesis presents a detailed computational study of a new method for mixed radiation field dosimetry using single-element TL dosimeters with pulsed laser heating schemes. The main objective of this study was to obtain an optimum heating scheme so that the depth-dose distribution in a thick TL dosimeter could be accurately determined. The major parts of the study include: (a) heat conduction calculations for TL dosimeters with various heating schemes, (b) glow curve calculations for TL dosimeters based on a first-order kinetic model, (c) unfolding of the depth-dose distribution based on the glow curve data, and (d) estimation of shallow and deep doses from the unfolded depth-dose distribution. Two optimum heating schemes were obtained in this study. The first one was obtained for a focused laser beam, and the second one was obtained for a uniform laser beam. Both heating schemes consist of two processes: top surface heating and bottom surface heating, and each process in turn consists of a sequence of laser pulses with various heating durations and power levels. Compared to the ``true`` depth-dose distribution obtained using Monte Carlo transport code EGS4, relative errors associated with the shallow and deep doses obtained from the unfolded depth-dose distributions are 5% and 25%, respectively, for the focused laser beam, and 15% in both doses for the uniform laser beam. 74 refs., 148 figs.

  11. Laser generated proton beam focusing and high temperature isochoric heating of solid matter

    SciTech Connect

    Snavely, R. A.; Hatchett, S. P.; Key, M. H.; Langdon, A. B.; Lasinski, B. F.; MacKinnon, A. J.; Patel, P.; Town, R.; Wilks, S. C.; Zhang, B.; Akli, K.; Hey, D.; King, J.; Chen, Z.; Izawa, Y.; Kitagawa, Y.; Kodama, R.; Lei, A.; Tampo, M.; Tanaka, K. A.

    2007-09-15

    The results of laser-driven proton beam focusing and heating with a high energy (170 J) short pulse are reported. Thin hemispherical aluminum shells are illuminated with the Gekko petawatt laser using 1 {mu}m light at intensities of {approx}3x10{sup 18} W/cm{sup 2} and measured heating of thin Al slabs. The heating pattern is inferred by imaging visible and extreme-ultraviolet light Planckian emission from the rear surface. When Al slabs 100 {mu}m thick were placed at distances spanning the proton focus beam waist, the highest temperatures were produced at 0.94x the hemisphere radius beyond the equatorial plane. Isochoric heating temperatures reached 81 eV in 15 {mu}m thick foils. The heating with a three-dimensional Monte Carlo model of proton transport with self-consistent heating and proton stopping in hot plasma was modeled.

  12. Low-level laser effects on bacterial cultures submitted to heat stress

    NASA Astrophysics Data System (ADS)

    Gonçalves, E. M.; Guimarães, O. R.; Geller, M.; Paoli, F.; Fonseca, A. S.

    2016-06-01

    Low-level lasers have been used worldwide to treat a number of diseases, pain relief, and wound healing. Some studies demonstrated that low-level laser radiations induce effects depending on the physiological state and DNA repair mechanisms of cells. In this work we evaluated the effects of low-level red and infrared lasers on Escherichia coli cells deficient in SOS responses submitted to heat stress. Exponential and stationary E. coli cultures of wild type (AB1157), RecA deficient (AB2463) and LexA deficient (AB2494), both SOS response deficient, were exposed to low-level red and infrared lasers at different fluences and submitted to heat stress (42 °C, 20 min). After that, cell survival and morphology were evaluated. Previous exposure to red, but not infrared lasers, increases survival fractions and decreases the area ratios of E. coli AB1157 cells submitted to heat stress. Our research suggests that a low-level red laser increases cell viability and protects cells from morphological alteration in E. coli cultures submitted to heat stress depending on laser wavelength and SOS response.

  13. In situ laser heating and radial synchrotron X-ray diffraction ina diamond anvil cell

    SciTech Connect

    Kunz, Martin; Caldwell, Wendel A.; Miyagi, Lowell; Wenk,Hans-Rudolf

    2007-06-29

    We report a first combination of diamond anvil cell radialx-ray diffraction with in situ laser heating. The laser-heating setup ofALS beamline 12.2.2 was modified to allow one-sided heating of a samplein a diamond anvil cell with an 80 W yttrium lithium fluoride laser whileprobing the sample with radial x-ray diffraction. The diamond anvil cellis placed with its compressional axis vertical, and perpendicular to thebeam. The laser beam is focused onto the sample from the top while thesample is probed with hard x-rays through an x-ray transparentboron-epoxy gasket. The temperature response of preferred orientation of(Fe,Mg)O is probed as a test experiment. Recrystallization was observedabove 1500 K, accompanied by a decrease in stress.

  14. In situ laser heating and radial synchrotron x-ray diffraction in a diamond anvil cell

    SciTech Connect

    Kunz, Martin; Caldwell, Wendel A.; Miyagi, Lowell; Wenk, Hans-Rudolf

    2007-06-15

    We report a first combination of diamond anvil cell radial x-ray diffraction with in situ laser heating. The laser-heating setup of ALS beamline 12.2.2 was modified to allow one-sided heating of a sample in a diamond anvil cell with an 80 W yttrium lithium fluoride laser while probing the sample with radial x-ray diffraction. The diamond anvil cell is placed with its compressional axis vertical, and perpendicular to the beam. The laser beam is focused onto the sample from the top while the sample is probed with hard x-rays through an x-ray transparent boron-epoxy gasket. The temperature response of preferred orientation of (Fe,Mg)O is probed as a test experiment. Recrystallization was observed above 1500 K, accompanied by a decrease in stress.

  15. Imaging laser heated subsurface chromophores in biological materials: determination of lateral physical dimensions.

    PubMed

    Milner, T E; Goodman, D M; Tanenbaum, B S; Anvari, B; Svaasand, L O; Nelson, J S

    1996-01-01

    We describe a non-contact method using infrared radiometry to determine lateral physical dimensions of laser heated subsurface chromophores in biological materials. An imaging equation is derived that relates measured radiometric temperature change to the reduced two-dimensional temperature increase of laser heated chromophores. From measured images of radiometric temperature change, the lateral physical dimensions of chromophores positioned in an in vitro model of human skin are determined by deconvolution of the derived imaging equation using a non-negative constrained conjugate gradient algorithm. Conditions for optimum spatial resolution are found by analysis of a derived radiometric transfer function and correspond to superficial chromophores and/or weak infrared absorption in a laser irradiated biological material. Analysis indicates that if the infrared attenuation coefficient is sufficiently small (i.e., less than 10mm-1), infrared radiometry in combination with a deconvolution algorithm allows estimation of lateral physical dimensions of laser heated subsurface chromophores in human skin.

  16. Change in the optical properties of hyaline cartilage heated by the near-IR laser radiation

    SciTech Connect

    Bagratashvili, Viktor N; Bagratashvili, N V; Omel'chenko, A I; Sviridov, A P; Sobol', E N; Tsypina, S I; Gapontsev, V P; Minaev, V P; Samartsev, I E; Makhmutova, G Sh

    2001-06-30

    The in vitro dynamics of the change in optical properties of hyaline cartilage heated by fibre lasers at wavelengths 0.97 and 1.56 {mu}m is studied. The laser-induced bleaching (at 1.56 {mu}m) and darkening (at 0.97 {mu}m) of the cartilage, caused by the heating and transport of water as well as by a change in the cartilage matrix, were observed and studied. These effects should be taken into account while estimating the depth of heating of the tissue. The investigated dynamics of light scattering in the cartilage allows one to choose the optimum radiation dose for laser plastic surgery of cartilage tissues. (laser applications and other topics in quantum electronics)

  17. In situ laser heating and radial synchrotron x-ray diffraction in a diamond anvil cell.

    PubMed

    Kunz, Martin; Caldwell, Wendel A; Miyagi, Lowell; Wenk, Hans-Rudolf

    2007-06-01

    We report a first combination of diamond anvil cell radial x-ray diffraction with in situ laser heating. The laser-heating setup of ALS beamline 12.2.2 was modified to allow one-sided heating of a sample in a diamond anvil cell with an 80 W yttrium lithium fluoride laser while probing the sample with radial x-ray diffraction. The diamond anvil cell is placed with its compressional axis vertical, and perpendicular to the beam. The laser beam is focused onto the sample from the top while the sample is probed with hard x-rays through an x-ray transparent boron-epoxy gasket. The temperature response of preferred orientation of (Fe,Mg)O is probed as a test experiment. Recrystallization was observed above 1500 K, accompanied by a decrease in stress.

  18. Monte Carlo model for determination of the role of heat generation in laser-irradiated tissue.

    PubMed

    Welch, A J; Gardner, C M

    1997-11-01

    A Monte Carlo model is described for modeling photo propagation in a scattering medium. The fraction of locally absorbed photons is proportional to the local rate of heat generation in laser-irradiated tissue and the associated distribution of light (fluence rate) is obtained by dividing the rate of heat generation by the local absorption coefficient. Examples of computed distributions of the rate of heat generation are presented for situations where light scattering in tissue is important. The method is applied to analyze treatment of Port Wine Stain and the selection of laser wavelengths for cyclophotocoagulation.

  19. Rapid heating of matter using high power lasers

    SciTech Connect

    Bang, Woosuk

    2015-11-05

    This report describes rapid heating technology with ion sources. LANL calculated the expected heating per atom and temperatures of the target materials, used alumium ion beams to heat gold and diamond, produced deuterium fusion plasmas and then measured the ion temperature at the time of the fusion reactions.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  1. Tailored boron steel sheet component properties by selective laser heat treatment

    NASA Astrophysics Data System (ADS)

    Asnafi, N.; Andersson, R.; Persson, M.; Liljengren, M.

    2016-11-01

    This investigation is focused on the stamping behaviour of boron steel, the properties of which are modified by selective laser heat treatment. Both CO2 and fibre lasers are tested. By using different laser processing parameters, the hardening depth in the 1 mm thick boron steel sheet Boloc 02 is varied. Four routes are tested and verified. The forming operation (in which a so-called flexrail beam is produced) in all four routes is conducted at ambient (room) temperature. The Reference route comprises stamping of the sheet. The GridBlank route starts with selective laser heat treatment of the blank, after which the blank is allowed to cool down, moved to a hydraulic press and stamped. In the GridTube route, the blank is first stamped, after which the part is moved to a laser cell and selectively laser heat treated. The fourth route, the RapidLaser route, is similar to the GridBlank route, but a higher laser speed is used to promote higher total productivity. The GridBlank route results in the highest hardness values and the best shape accuracy. The initial sheet material exhibits a hardness of 200 HV, while the parts produced in the GridBlank route exhibit a hardness of 700 HV.

  2. Measurement of preheating due to radiation and nonlocal electron heat transport in laser-irradiated targets

    SciTech Connect

    Otani, K.; Shigemori, K.; Kadono, T.; Hironaka, Y.; Nakai, M.; Shiraga, H.; Azechi, H.; Mima, K.; Ozaki, N.; Kimura, T.; Miyanishi, K.; Kodama, R.; Sakaiya, T.; Sunahara, A.

    2010-03-15

    This paper reports an experimental study on preheating of laser-irradiated targets. We performed temperature measurements at the rear surface of laser-irradiated targets under conditions of two different laser wavelengths (0.35 or 0.53 mum) and several intensities (2x10{sup 13}-1x10{sup 14} W/cm{sup 2}) in order to verify an effect of radiation and nonlocal electron heat transport. The preheating temperature was evaluated by observing self-emission, reflectivity, and expansion velocity at the rear surface of planar polyimide foils. The experimental results show that the x-ray radiation is dominant for preheating for 0.35-mum laser irradiation, but contribution of nonlocal electron heat transport is not negligible for 0.53-mum laser irradiation conditions.

  3. Surface-selective laser sintering of thermolabile polymer particles using water as heating sensitizer

    SciTech Connect

    Antonov, E N; Krotova, L I; Minaev, N V; Minaeva, S A; Mironov, A V; Popov, V K; Bagratashvili, V N

    2015-11-30

    We report the implementation of a novel scheme for surface-selective laser sintering (SSLS) of polymer particles, based on using water as a sensitizer of laser heating and sintering of particles as well as laser radiation at a wavelength of 1.94 μm, corresponding to the strong absorption band of water. A method of sintering powders of poly(lactide-co-glycolide), a hydrophobic bioresorbable polymer, after modifying its surface with an aqueous solution of hyaluronic acid is developed. The sintering thresholds for wetted polymer are by 3 – 4 times lower than those for sintering in air. The presence of water restricts the temperature of the heated polymer, preventing its thermal destruction. Polymer matrices with a developed porous structure are obtained. The proposed SSLS method can be applied to produce bioresorbable polymer matrices for tissue engineering. (interaction of laser radiation with matter. laser plasma)

  4. Selective laser sintering with heat of formation by using reactive materials

    NASA Astrophysics Data System (ADS)

    Kamitani, Takayuki; Yamada, Osamu; Marutani, Yoji

    2000-11-01

    In this paper, we propose a new method of fabricating 3-D models of the high-temperature structural materials such as ceramics by selective laser sintering (SLS). To save the laser energy, we adopted the combustion synthesis which is the exothermic reaction between the raw materials. By adding chemical reaction heat to laser heat, the particles of the products of the reaction were bonded together by relatively low laser energy. The combinations of the raw materials and the laser scanning conditions for solidifying the products and laminating the solidified layers were investigated experimentally. Since burning in the furnace is unnecessary in the proposed method, it is possible to fabricate the models in a short time.

  5. Electron heating in subpicosecond laser interaction with overdense and near-critical plasmas

    NASA Astrophysics Data System (ADS)

    Cialfi, L.; Fedeli, L.; Passoni, M.

    2016-11-01

    In this work we investigate electron heating induced by intense laser interaction with micrometric flat solid foils in the context of laser-driven ion acceleration. We propose a simple law to predict the electron temperature in a wider range of laser parameters with respect to commonly used existing models. An extensive two-dimensional (2D) and 3D numerical campaign shows that electron heating is due to the combined actions of j ×B and Brunel effect. Electron temperature can be well described with a simple function of pulse intensity and angle of incidence, with parameters dependent on pulse polarization. We then combine our model for the electron temperature with an existing model for laser-ion acceleration, using recent experimental results as a benchmark. We also discuss an exploratory attempt to model electron temperature for multilayered foam-attached targets, which have been proven recently to be an attractive target concept for laser-driven ion acceleration.

  6. Laser irradiation of carbon nanotube films: Effects and heat dissipation probed by Raman spectroscopy

    SciTech Connect

    Mialichi, J. R.; Brasil, M. J. S. P.; Iikawa, F.; Verissimo, C.; Moshkalev, S. A.

    2013-07-14

    We investigate the thermal properties of thin films formed by single- and multi-walled carbon nanotubes submitted to laser irradiation using Raman scattering as a probe of both the tube morphology and the local temperature. The nanotubes were submitted to heating/cooling cycles attaining high laser intensities ({approx}1.4 MW/cm{sup 2}) under vacuum and in the presence of an atmosphere, with and without oxygen. We investigate the heat diffusion of the irradiated nanotubes to their surroundings and the effect of laser annealing on their properties. The presence of oxygen during laser irradiation gives rise to an irreversible increase of the Raman efficiency of the carbon nanotubes and to a remarkable increase of the thermal conductivity of multi-walled films. The second effect can be applied to design thermal conductive channels in devices based on carbon nanotube films using laser beams.

  7. Modified Laser Flash Method for Thermal Properties Measurements and the Influence of Heat Convection

    NASA Technical Reports Server (NTRS)

    Lin, Bochuan; Zhu, Shen; Ban, Heng; Li, Chao; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

    2003-01-01

    The study examined the effect of natural convection in applying the modified laser flash method to measure thermal properties of semiconductor melts. Common laser flash method uses a laser pulse to heat one side of a thin circular sample and measures the temperature response of the other side. Thermal diffusivity can be calculations based on a heat conduction analysis. For semiconductor melt, the sample is contained in a specially designed quartz cell with optical windows on both sides. When laser heats the vertical melt surface, the resulting natural convection can introduce errors in calculation based on heat conduction model alone. The effect of natural convection was studied by CFD simulations with experimental verification by temperature measurement. The CFD results indicated that natural convection would decrease the time needed for the rear side to reach its peak temperature, and also decrease the peak temperature slightly in our experimental configuration. Using the experimental data, the calculation using only heat conduction model resulted in a thermal diffusivity value is about 7.7% lower than that from the model with natural convection. Specific heat capacity was about the same, and the difference is within 1.6%, regardless of heat transfer models.

  8. Modified Laser Flash Method for Thermal Properties Measurements and the Influence of Heat Convection

    NASA Technical Reports Server (NTRS)

    Lin, Bochuan; Zhu, Shen; Ban, Heng; Li, Chao; Scripa, Rosalia N.; Su, Ching-Hua; Lehoczky, Sandor L.

    2003-01-01

    The study examined the effect of natural convection in applying the modified laser flash method to measure thermal properties of semiconductor melts. Common laser flash method uses a laser pulse to heat one side of a thin circular sample and measures the temperature response of the other side. Thermal diffusivity can be calculations based on a heat conduction analysis. For semiconductor melt, the sample is contained in a specially designed quartz cell with optical windows on both sides. When laser heats the vertical melt surface, the resulting natural convection can introduce errors in calculation based on heat conduction model alone. The effect of natural convection was studied by CFD simulations with experimental verification by temperature measurement. The CFD results indicated that natural convection would decrease the time needed for the rear side to reach its peak temperature, and also decrease the peak temperature slightly in our experimental configuration. Using the experimental data, the calculation using only heat conduction model resulted in a thermal diffusivity value is about 7.7% lower than that from the model with natural convection. Specific heat capacity was about the same, and the difference is within 1.6%, regardless of heat transfer models.

  9. Laser heating dynamics and glow spectra of carbon-, titanium- and erbium-containing optothermal fibre converters for laser medicine

    NASA Astrophysics Data System (ADS)

    Belikov, A. V.; Skrypnik, A. V.

    2017-07-01

    Titanium- and erbium-containing optothermal fibre converters of laser radiation mounted at the distal end of quartz-quartz optical fibre are discussed for the first time. Technology of fabricating such converters is described. Carbon-containing converters are also considered. The laser heating dynamics of the converters and the glow spectra are studied by irradiating converters of each type by a 980 ± 10 nm semiconductor laser with an average power up to 4 W. It is shown that alongside with broadband thermal radiation accompanying the laser heating of all three types of converters in the temperature range 600-1100 °C, only in the spectrum of the erbium-containing converter the intense bands with the maxima at wavelengths 493, 523, 544, 660, and 798 nm, corresponding to the erbium radiative transitions 4F7/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, 4F9/2 → 4I15/2 and 4I9/2 → 4I15/2, respectively, are present. Such converters can be used in laser medicine for tissue surgery as well as in procedures combining laser, thermal, biostimulation or photodynamic action.

  10. Thermal elasto-plastic stress analysis during laser heating of a metal plate

    NASA Astrophysics Data System (ADS)

    Chen, Yanbei; Lu, Jian; Ni, Xiaowu

    2008-03-01

    During laser heating of a metal material, the continuity of material confines its free expansion, thermal stresses arise. On one hand the thermal expansion of the heated zone of the material increases with the increase of temperature, the thermal stress level increases correspondingly; on the other hand the mechanical properties of the material will change with the increase of temperature, especially the elastic modulus, yield strength and tensile strength drop significantly, which is the so-called thermal softening problem. Due to the effect of the two factors, as the heating time or the intensity of the laser beam increases, it is possible that the stress levels of the heated zone of the material exceed the yield strength, which leads the material to come into a plastic stage. Thus, a thermal plastic problem occurs. In this study, thermal elasto-plastic stresses during laser heating of a metal plate are computed by the finite element method (FEM) based on thermal elasto-plastic constitutive theory. The mechanical behaviors of the metal material during the laser heating are analyzed. By the analysis of the results, it is found that thermal expansion leads to the increase of stress level early during the laser irradiating, and thermal softening causes the decrease of stress levels in the plastic zone and the slow growth and even decrease of stress levels in elastic zone later. The radial stresses are all compressive stresses, and the hoop stresses are compressive stresses within about the laser spot and are tensile stresses at other place. This work may be beneficial to the laser processing of metal materials.

  11. Scattering effect in radiative heat transfer during selective laser sintering of polymers

    NASA Astrophysics Data System (ADS)

    Liu, Xin; Boutaous, M'hamed; Xin, Shihe

    2016-10-01

    The aim of this work is to develop an accurate model to simulate the selective laser sintering (SLS) process, in order to understand the multiple phenomena occurring in the material and to study the influence of each parameter on the quality of the sintered parts. A numerical model, coupling radiative and conductive heat transfers in a polymer powder bed providing a local temperature field, is proposed. To simulate the polymer sintering by laser heating as in additive manufacturing, a double-lines scanning of a laser beam over a thin layer of polymer powder is studied. An effective volumetric heat source, using a modified Monte Carlo method, is estimated from laser radiation scattering and absorption in a semi-transparent polymer powder bed. In order to quantify the laser-polymer interaction, the heating and cooling of the material is modeled and simulated with different types heat sources by both finite elements method (FEM) and discrete elements method (DEM). To highlight the importance of introducing a semi-transparent behavior of such materials and in order to validate our model, the results are compared with works taken from the literature.

  12. Development of a laser-induced heat flux technique for measurement of convective heat transfer coefficients in a supersonic flowfield

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert; Keith, Theo G., Jr.; Hingst, Warren R.; Chriss, Randall M.; Seablom, Kirk D.

    1991-01-01

    A technique is developed to measure the local convective heat transfer coefficient on a model surface in a supersonic flow field. The technique uses a laser to apply a discrete local heat flux at the model test surface, and an infrared camera system determines the local temperature distribution due to heating. From this temperature distribution and an analysis of the heating process, a local convective heat transfer coefficient is determined. The technique was used to measure the load surface convective heat transfer coefficient distribution on a flat plate at nominal Mach numbers of 2.5, 3.0, 3.5, and 4.0. The flat plate boundary layer initially was laminar and became transitional in the measurement region. The experimental results agreed reasonably well with theoretical predictions of convective heat transfer of flat plate laminar boundary layers. The results indicate that this non-intrusive optical measurement technique has the potential to obtain high quality surface convective heat transfer measurements in high speed flowfields.

  13. Numerical simulation of heat transfer and fluid flow in laser drilling of metals

    NASA Astrophysics Data System (ADS)

    Zhang, Tingzhong; Ni, Chenyin; Zhou, Jie; Zhang, Hongchao; Shen, Zhonghua; Ni, Xiaowu; Lu, Jian

    2015-05-01

    Laser processing as laser drilling, laser welding and laser cutting, etc. is rather important in modern manufacture, and the interaction of laser and matter is a complex phenomenon which should be detailed studied in order to increase the manufacture efficiency and quality. In this paper, a two-dimensional transient numerical model was developed to study the temperature field and molten pool size during pulsed laser keyhole drilling. The volume-of-fluid method was employed to track free surfaces, and melting and evaporation enthalpy, recoil pressure, surface tension, and energy loss due to evaporating materials were considered in this model. Besides, the enthalpy-porosity technique was also applied to account for the latent heat during melting and solidification. Temperature fields and melt pool size were numerically simulated via finite element method. Moreover, the effectiveness of the developed computational procedure had been confirmed by experiments.

  14. Industrial femtosecond lasers for machining of heat-sensitive polymers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Hendricks, Frank; Bernard, Benjamin; Matylitsky, Victor V.

    2017-03-01

    Heat-sensitive materials, such as polymers, are used increasingly in various industrial sectors such as medical device manufacturing and organic electronics. Medical applications include implantable devices like stents, catheters and wires, which need to be structured and cut with minimum heat damage. Also the flat panel display market moves from LCD displays to organic LED (OLED) solutions, which utilize heat-sensitive polymer substrates. In both areas, the substrates often consist of multilayer stacks with different types of materials, such as metals, dielectric layers and polymers with different physical characteristic. The different thermal behavior and laser absorption properties of the materials used makes these stacks difficult to machine using conventional laser sources. Femtosecond lasers are an enabling technology for micromachining of these materials since it is possible to machine ultrafine structures with minimum thermal impact and very precise control over material removed. An industrial femtosecond Spirit HE laser system from Spectra-Physics with pulse duration <400 fs, pulse energies of >120 μJ and average output powers of >16 W is an ideal tool for industrial micromachining of a wide range of materials with highest quality and efficiency. The laser offers process flexibility with programmable pulse energy, repetition rate, and pulse width. In this paper, we provide an overview of machining heat-sensitive materials using Spirit HE laser. In particular, we show how the laser parameters (e.g. laser wavelength, pulse duration, applied energy and repetition rate) and the processing strategy (gas assisted single pass cut vs. multi-scan process) influence the efficiency and quality of laser processing.

  15. Laser heat hyperalgesia is not a feature of non-specific chronic low back pain.

    PubMed

    Franz, M; Ritter, A; Puta, C; Nötzel, D; Miltner, W H R; Weiss, T

    2014-11-01

    Based upon studies using mechanical pin-prick, pressure, electrical or heat stimuli applied to painful and/or pain-free parts of the body, chronic low back pain (CLBP) has been shown to be associated with generalized and enhanced pain sensitivity and altered brain responses to noxious stimuli. To date, no study examined the processing of noxious laser heat pulses, which are known to selectively excite thermal nociceptors located in the superficial skin layers, in CLBP. We studied laser heat pain thresholds (LHPTs) and nociceptive laser-evoked brain electrical potentials (LEPs) following skin stimulation of the pain-affected back and the pain-free abdomen using noxious laser heat stimulation in 16 CLBP patients and 16 age- and gender-matched healthy controls (HCs). We observed no statistically significant differences in LHPTs between CLBP patients and HCs, neither on the back nor on the abdomen. Furthermore, we found no evidence for altered brain responses between CLBP patients and HCs in response to stimulation of the back and abdomen in single-trial latencies and amplitudes of LEP components (N2, P2). The results are in contrast to previous studies showing hypersensitivity to different experimental noxious stimuli (e.g., contact heat). We argue that these discrepancies may be due to low spatial and temporal summation within the central nervous system following laser heat stimulation. Our results indicate important methodological differences between laser heat and thermode stimulation that should be taken into account when interpreting results, such as from thermal quantitative sensory testing. © 2014 European Pain Federation - EFIC®

  16. Growing Crystaline Sapphire Fibers By Laser Heated Pedestal Techiques

    DOEpatents

    Phomsakha, Vongvilay; Chang, Robert S. F.; Djeu, Nicholas I.

    1997-03-04

    An improved system and process for growing crystal fibers comprising a means for creating a laser beam having a substantially constant intensity profile through its cross sectional area, means for directing the laser beam at a portion of solid feed material located within a fiber growth chamber to form molten feed material, means to support a seed fiber above the molten feed material, means to translate the seed fiber towards and away from the molten feed material so that the seed fiber can make contact with the molten feed material, fuse to the molten feed material and then be withdrawn away from the molten feed material whereby the molten feed material is drawn off in the form of a crystal fiber. The means for creating a laser beam having a substantially constant intensity profile through its cross sectional area includes transforming a previously generated laser beam having a conventional gaussian intensity profile through its cross sectional area into a laser beam having a substantially constant intensity profile through its cross sectional area by passing the previously generated laser beam through a graded reflectivity mirror. The means for directing the laser beam at a portion of solid feed material is configured to direct the laser beam at a target zone which contains the molten feed material and a portion of crystal fiber drawn off the molten feed material by the seed fiber. The means to support the seed fiber above the molten feed material is positioned at a predetermined height above the molten feed material. This predetermined height provides the seed fiber with sufficient length and sufficient resiliency so that surface tension in the molten feed material can move the seed fiber to the center of the molten feed material irrespective of where the seed fiber makes contact with the molten feed material. The internal atmosphere of the fiber growth chamber is composed substantially of Helium gas.

  17. Thermal transport in shock wave–compressed solids using pulsed laser heating

    SciTech Connect

    La Lone, B. M.; Capelle, G.; Stevens, G. D.; Turley, W. D.; Veeser, L. R.

    2014-07-01

    A pulsed laser heating method was developed for determining thermal transport properties of solids under shock-wave compression. While the solid is compressed, a laser deposits a known amount of heat onto the sample surface, which is held in the shocked state by a transparent window. The heat from the laser briefly elevates the surface temperature and then diffuses into the interior via one-dimensional heat conduction. The thermal effusivity is determined from the time history of the resulting surface temperature pulse, which is recorded with optical pyrometry. Thermal effusivity is the square root of the product of thermal conductivity and volumetric heat capacity and is the key thermal transport parameter for relating the surface temperature to the interior temperature of the sample in a dynamic compression experiment. Therefore, this method provides information that is needed to determine the thermodynamic state of the interior of a compressed metal sample from a temperature measurement at the surface. The laser heat method was successfully demonstrated on tin that was shock compressed with explosives to a stress and temperature of ~25 GPa and ~1300 K. In this state, tin was observed to have a thermal effusivity of close to twice its ambient value. The implications on determining the interior shock wave temperature of tin are discussed.

  18. Thermal transport in shock wave–compressed solids using pulsed laser heating

    SciTech Connect

    La Lone, B. M. Capelle, G.; Stevens, G. D.; Turley, W. D.; Veeser, L. R.

    2014-07-15

    A pulsed laser heating method was developed for determining thermal transport properties of solids under shock-wave compression. While the solid is compressed, a laser deposits a known amount of heat onto the sample surface, which is held in the shocked state by a transparent window. The heat from the laser briefly elevates the surface temperature and then diffuses into the interior via one-dimensional heat conduction. The thermal effusivity is determined from the time history of the resulting surface temperature pulse, which is recorded with optical pyrometry. Thermal effusivity is the square root of the product of thermal conductivity and volumetric heat capacity and is the key thermal transport parameter for relating the surface temperature to the interior temperature of the sample in a dynamic compression experiment. Therefore, this method provides information that is needed to determine the thermodynamic state of the interior of a compressed metal sample from a temperature measurement at the surface. The laser heat method was successfully demonstrated on tin that was shock compressed with explosives to a stress and temperature of ∼25 GPa and ∼1300 K. In this state, tin was observed to have a thermal effusivity of close to twice its ambient value. The implications on determining the interior shock wave temperature of tin are discussed.

  19. A nanosecond pulsed laser heating system for studying liquid and supercooled liquid films in ultrahigh vacuum

    NASA Astrophysics Data System (ADS)

    Xu, Yuntao; Dibble, Collin J.; Petrik, Nikolay G.; Smith, R. Scott; Joly, Alan G.; Tonkyn, Russell G.; Kay, Bruce D.; Kimmel, Greg A.

    2016-04-01

    A pulsed laser heating system has been developed that enables investigations of the dynamics and kinetics of nanoscale liquid films and liquid/solid interfaces on the nanosecond time scale in ultrahigh vacuum (UHV). Details of the design, implementation, and characterization of a nanosecond pulsed laser system for transiently heating nanoscale films are described. Nanosecond pulses from a Nd:YAG laser are used to rapidly heat thin films of adsorbed water or other volatile materials on a clean, well-characterized Pt(111) crystal in UHV. Heating rates of ˜1010 K/s for temperature increases of ˜100-200 K are obtained. Subsequent rapid cooling (˜5 × 109 K/s) quenches the film, permitting in-situ, post-heating analysis using a variety of surface science techniques. Lateral variations in the laser pulse energy are ˜±2.7% leading to a temperature uncertainty of ˜±4.4 K for a temperature jump of 200 K. Initial experiments with the apparatus demonstrate that crystalline ice films initially held at 90 K can be rapidly transformed into liquid water films with T > 273 K. No discernable recrystallization occurs during the rapid cooling back to cryogenic temperatures. In contrast, amorphous solid water films heated below the melting point rapidly crystallize. The nanosecond pulsed laser heating system can prepare nanoscale liquid and supercooled liquid films that persist for nanoseconds per heat pulse in an UHV environment, enabling experimental studies of a wide range of phenomena in liquids and at liquid/solid interfaces.

  20. Determination of the heat transfer capability of laser mirrors with cooled cells

    NASA Astrophysics Data System (ADS)

    Zhernovyi, Yu. V.; Odnorozhenko, I. G.; Potyagailo, D. B.; Romanchuk, Ya. P.

    1992-09-01

    A mathematical model of steady-state heat transfer in a laser mirror involving cooled prismatically shaped cells has been developed. Using cooling systems with hexahedral and tetrahedral cells (by the number of side walls) as examples, the influence of the mirror illumination nonuniformity, reflector thickness, and other parameters on the effective heat-transfer coefficient and thermal head coefficient is investigated; the physical limits for heat-transfer characteristics in the case of an unlimited increase in heat transfer from the surfaces of the cell walls have been determined.

  1. High-speed measurement of an air transect's temperature shift heated by laser beam

    NASA Astrophysics Data System (ADS)

    Li, WenYu; Jiang, ZongFu; Xi, Fengjie; Li, Qiang; Xie, Wenke

    2005-02-01

    Laser beam heat the air on the optic path, Beam-deflection optical tomography is a non-intrusive method to measure the 2-dimension temperature distribution in the transect. By means of linear Hartmann Sensor at the rate of 27kHz, the optic path was heated by a 2.7μm HF laser, continuous and high time resolution gradients of optic phase were obtained. the result of analysing and calculation showed the temperament shift in the heated beam path was not higher than 50K when the HF laser power was 9W. The experiment showed that it is a practical non-intrusive temperature shift measurement method for a small area aero-optical medium.

  2. Calibrated heat flow model for the determination of different heat-affected zones in single-pass laser-cut CFRP using a cw CO2 laser

    NASA Astrophysics Data System (ADS)

    Mucha, P.; Berger, P.; Weber, R.; Speker, N.; Sommer, B.; Graf, T.

    2015-03-01

    Laser machining has great potential for automated manufacturing of parts made of carbon-fiber-reinforced plastic (CFRP) due to the nearly force and tool-wear free processing. The high vaporization temperatures and the large heat conductivity of the carbon fibers, however, lead to unintentional heat conduction into the material causing damage in zones close to the process. In this paper, the matrix damage zone (MDZ) is subdivided into a matrix sublimation zone (MSZ) where the matrix material was sublimated and a zone where the temperature temporarily exceeded a value causing structural damage in the matrix. In order to investigate the extent of these zones, a one-dimensional heat flow model was applied, which was calibrated by cutting experiments using temperature sensors embedded in the CFRP samples. The investigations showed that the extents of the MSZ and MDZ are dominated by a total interaction time, which includes the passage of the laser beam and the continued interaction of the cloud of hot ablation products with the carbon fibers at the kerf wall and that from a practical point of view, the experimentally determined effective heat conductivity is suitable for simple estimations of the heat-affected zones in CFRP.

  3. Heat generation and thermo-mechanical effect modeling in longitudinally diode-pumped solid state lasers

    NASA Astrophysics Data System (ADS)

    Lakhdari, Fouad; Osmani, Ismahen; Tabet, Saida

    2015-09-01

    Thermal management in solid state laser is a challenge to the high power laser industry's ability to provide continued improvements in device and system performance. In this work an investigation of heat generation and thermo-mechanical effect in a high-power Nd:YAG and Yb:YAG cylindrical-type solid state laser pumped longitudinally with different power by fibre coupled laser diode is carried out by numerical simulation based on the finite element method (FEM). Impact of the dopant concentration on the power conversion efficiency is included in the simulation. The distribution of the temperature inside the lasing material is resolute according to the thermal conductivity. The thermo-mechanical effect is explored as a function of pump power in order to determine the maximum pumping power allowed to prevent the crystal's fracture. The presented simulations are in broad agreement with analytical solutions; provided that the boundary condition of the pump induced heat generation is accurately modelled.

  4. Infrared testing for engine blades crack defects with laser scanning automatic heat loading

    NASA Astrophysics Data System (ADS)

    Bai, Fengming; Song, Nuan; Wang, Lixiao

    2008-12-01

    In this paper, automatic scanning infrared laser nondestructive testing methods, such as aero-engine blades crack detection of defects; Use of thermal heating differential equations and leaves the surface temperature distribution in the infrared detection system to allow resolution under discussion laser scanning heating infrared detection engine blades crack defects. The method can be nondestructive testing of metal parts of the internal defects, such as micro-cracks, loose, porosity and so on, like the thin parts more effective. First introduced in the infrared detection system works as using laser scans of the work piece to be seized automatic heating pretreatment, to detect internal defects part of the nature and characteristics of purpose. The paper also build a two-dimensional analysis model of detected objects because of defective parts and non-defective parts of the geometry and physical properties of heat there is an obvious difference in surface temperature caused by the different response, therefore, can discuss affect of the temperature distribution of information, to determine the appropriate method. Discuss and analysis interaction between the loading heat flux density, length and depth of defects, and do some heat transfer analysis to measured the surface temperature distribution. Through load a constant heat flow to blades, the infrared detection system can obtain the surface temperature field of existence the temperature difference, which blades cracks determine the existence and its location.

  5. Heat shock protein expression as guidance for the therapeutic window of retinal laser therapy

    NASA Astrophysics Data System (ADS)

    Wang, Jenny; Huie, Philip; Dalal, Roopa; Lee, Seungjun; Tan, Gavin; Lee, Daeyoung; Lavinksy, Daniel; Palanker, Daniel

    2016-03-01

    Unlike conventional photocoagulation, non-damaging retinal laser therapy (NRT) limits laser-induced heating to stay below the retinal damage threshold and therefore requires careful dosimetry. Without the adverse effects associated with photocoagulation, NRT can be applied to critical areas of the retina and repeatedly to manage chronic disorders. Although the clinical benefits of NRT have been demonstrated, the mechanism of therapeutic effect and width of the therapeutic window below damage threshold are not well understood. Here, we measure activation of heat shock response via laser-induced hyperthermia as one indication of cellular response. A 577 nm laser is used with the Endpoint Management (EpM) user interface, a titration algorithm, to set experimental pulse energies relative to a barely visible titration lesion. Live/dead staining and histology show that the retinal damage threshold in rabbits is at 40% of titration energy on EpM scale. Heat shock protein 70 (HSP70) expression in the retinal pigment epithelium (RPE) was detected by whole-mount immunohistochemistry after different levels of laser treatment. We show HSP70 expression in the RPE beginning at 25% of titration energy indicating that there is a window for NRT between 25% and 40% with activation of the heat shock protein expression in response to hyperthermia. HSP70 expression is also seen at the perimeter of damaging lesions, as expected based on a computational model of laser heating. Expression area for each pulse energy setting varied between laser spots due to pigmentation changes, indicating the relatively narrow window of non-damaging activation and highlighting the importance of proper titration.

  6. Effect of electron emission on solids heating by femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Svirina, V. V.; Sergaeva, O. N.; Yakovlev, E. B.

    2011-02-01

    Ultrashort laser pulse interaction with material involves a number of specialities as compared to longer irradiations. We study laser heating of metal by femtosecond pulse with taking into account electron photo- and thermionic emission leading to accumulation of a high positive charge on the target surface and, thus, to the generation of the electric field which causes Coulomb explosion (an electronic mechanism of ablation). Also emission slightly influences the thermal and optical properties of solids.

  7. Effect of electron emission on solids heating by femtosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Svirina, V. V.; Sergaeva, O. N.; Yakovlev, E. B.

    2010-07-01

    Ultrashort laser pulse interaction with material involves a number of specialities as compared to longer irradiations. We study laser heating of metal by femtosecond pulse with taking into account electron photo- and thermionic emission leading to accumulation of a high positive charge on the target surface and, thus, to the generation of the electric field which causes Coulomb explosion (an electronic mechanism of ablation). Also emission slightly influences the thermal and optical properties of solids.

  8. Improving the efficiency of high-power diode lasers using diamond heat sinks

    SciTech Connect

    Parashchuk, Valentin V; Baranov, V V; Telesh, E V; Mien, Vu Doan; Luc, Vu Van; Truong, Pham Van; Belyaeva, A K

    2010-06-23

    Using multifunctional ion beam and magnetron sputtering systems, we have developed chemical and vacuum techniques for producing metallic coatings firmly adherent to various surfaces, with application to copper and diamond heat sinks for diode lasers. Conditions have been optimised for mounting diode lasers and bars using the proposed metallisation processes, and significant improvements in the output parameters of the devices have been achieved. The power output of cw laser diodes on diamond heat sinks increases by up to a factor of 2, the linear (working) portion of their power-current characteristic becomes markedly broader, and their slope efficiency increases by a factor of 1.5 - 2 relative to that of lasers on copper heat spreaders. The use of diamond heat sinks extends the drive current range of pulsed diode bars by a factor of 2 - 3 and enables them to operate at more than one order of magnitude longer pump pulse durations (up to milliseconds) when the pulse repetition rate is at least 10 Hz. (lasers)

  9. Equation of State Measurements of Dense Plasmas Heated by Laser Accelerated MeV Protons

    NASA Astrophysics Data System (ADS)

    Dyer, Gilliss; Bernstein, Aaron; Cho, Byoung-Ick; Grigsby, Will; Dalton, Allen; Shepherd, Ronnie; Ping, Yuan; Chen, Hui; Widmann, Klaus; Ozterhoz, Jens; Ditmire, Todd

    2008-04-01

    Using a fast proton beam generated with an ultra intense laser we have generated and measured the equation of state of solid density plasma at temperatures near 20 eV, a regime in which there have been few previous experimental measurements. The laser accelerated a directional, short pulse of MeV protons, which isochorically heated a solid slab of aluminum. Using two simultaneous, temporally resolved measurements we observed the thermal emission and expansion of the heated foil with picosecond time resolution. With these data we were able to confirm, to within 10%, the SESAME equation-of-state table in this dense plasma region.

  10. Heat accumulation in ultra-short pulsed scanning laser ablation of metals.

    PubMed

    Bauer, Franziska; Michalowski, Andreas; Kiedrowski, Thomas; Nolte, Stefan

    2015-01-26

    High average laser powers can have a serious adverse impact on the ablation quality in ultra-short pulsed laser material processing of metals. With respect to the scanning speed, a sharp transition between a smooth, reflective and an uneven, dark ablated surface is observed. Investigating the influence of the sample temperature, it is experimentally shown that this effect stems from heat accumulation. In a numerical heat flow simulation, the critical scanning speed indicating the change in ablation quality is determined in good agreement with the experimental data.

  11. A New Method to Grow SiC: Solvent-Laser Heated Floating Zone

    NASA Technical Reports Server (NTRS)

    Woodworth, A. A.; Neudeck, Philip G.; Sayir, Ali

    2012-01-01

    The solvent-laser heated floating zone (solvent-LHFZ) growth method is being developed to grow long single crystal SiC fibers. The technique combines the single crystal fiber growth ability of laser heated floating zone with solvent based growth techniques (e.g. traveling solvent method) ability to grow SiC from the liquid phase. Initial investigations reported in this paper show that the solvent-LHFZ method readily grows single crystal SiC (retains polytype and orientation), but has a significant amount of inhomogeneous strain and solvent rich inclusions.

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

    NASA Astrophysics Data System (ADS)

    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 mm3) consisting of SiC, Ni/NiOx, 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 H2 gas ambient due to the higher thermal conductivity, temperatures up to 1000°C were achieved even in 200 Torr H2. 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. Management of heat in laser tissue welding using NIR cover window material.

    PubMed

    Sriramoju, Vidyasagar; Savage, Howard; Katz, Alvin; Muthukattil, Ronex; Alfano, Robert R

    2011-12-01

    Laser tissue welding (LTW) is a novel method of surgical wound closure by the use of laser radiation to induce fusion of the biological tissues. Molecular dynamics associated with LTW is a result of thermal and non-thermal mechanisms. This research focuses exclusively on better heat management to reduce thermal damage of tissues in LTW using a near infrared laser radiation. An infrared continuous-wave (CW) laser radiation at 1,450 nm wavelength corresponding to the absorption band from combination vibrational modes of water is used to weld together ex vivo porcine aorta. In these studies we measured the optimal laser power and scan speed, for better tensile strength of the weld and lesser tissue dehydration. Significant amount of water loss from the welded tissue results in cellular death and tissue buckling. Various thermally conductive optical cover windows were used as heat sinks to reduce thermal effects during LTW for the dissipation of the heat. The optimal use of the method prevents tissue buckling and minimizes the water loss. Diamond, sapphire, BK7, fused silica, and IR quartz transparent optical cover windows were tested. The data from this study suggests that IR-quartz as the material with optimal thermal conductivity is ideal for laser welding of the porcine aorta. Copyright © 2011 Wiley Periodicals, Inc.

  14. Laser-Induced Heating for DNA Replication in a Microfluidics

    NASA Astrophysics Data System (ADS)

    Hung, Min-Sheng; Chen, Chin-Pin

    In this study, we integrated microfluidics and a laser to develop a microfluidic system that performs target DNA replication. To achieve replication of targeted position of DNA, DNA fibers are stretched and both ends immobilized onto an electrode through dielectrophoresis. During the process, 2 designed primers, as well as DNA polymerase and its substrates, are fed into the microfluidics, and a focused infrared laser is used to irradiate the center of the DNA strand. An on-off switching mechanism is used to create thermal cycling. A polymerase chain reaction is then used to confirm the successfully replicated DNA.

  15. Laser heating of a transparent crystal via adsorbed atoms

    NASA Astrophysics Data System (ADS)

    van Smaalen, Sander; Arnoldus, Henk F.; George, Thomas F.

    1987-01-01

    A coated surface of a crystal is irradiated by intense infrared light. The optically active atomic bonds absorb photons from the laser field, and the subsequent spontaneous decay goes together with emissions of phonons into the crystal. This photon-to-phonon conversion results in an energy flux into the crystal. An equation for this flux is derived from the master equation for the level populations of the dressed atomic states. The saturation limit is discussed, and the general theory is illustrated with two examples. Furthermore, it is outlined with qualitative arguments that the quantum yield of photodesorption is not sensitive to the laser power.

  16. Visualization of expanding warm dense gold and diamond heated uniformly by laser-generated ion beams

    NASA Astrophysics Data System (ADS)

    Bang, W.; Albright, B. J.; Bradley, P. A.; Gautier, D. C.; Palaniyappan, S.; Vold, E. L.; Santiago Cordoba, M. A.; Hamilton, C. E.; Fernández, J. C.

    2015-11-01

    With a laser-generated beam of quasi-monoenergetic ions, a solid density target can be heated uniformly and isochorically. On the LANL Trident laser facility, we have used a beam of quasi-monoenergetic aluminum ions to heat gold and diamond foils. We visualized directly the expanding warm dense gold and diamond with an optical streak camera. Furthermore, we present a new technique to determine the initial temperatures of these heated samples from the measured expansion speeds of gold and diamond into vacuum. These temperatures are in good agreement with the expected temperatures calculated using the total deposited energy into the cold targets and SESAME equation-of-state tables at solid densities. We anticipate the uniformly heated solid density target will allow for direct quantitative measurements of equation-of-state, conductivity, opacity, and stopping power of warm dense matter, benefiting plasma physics, astrophysics, and nuclear physics. *This work is sponsored by the LANL LDRD Program.

  17. Stochastic heating of electrons by intense laser radiation in the presence of electrostatic potential well

    NASA Astrophysics Data System (ADS)

    Krasheninnikov, Sergei

    2014-10-01

    Previous model used for the study of synergistic effects of electrostatic potential well and laser radiation where electric field in electrostatic potential was slowing down electrons moving in the direction of the laser field propagation, is extended for the opposite case, where electric field of the well is accelerating electrons moving in the direction of the laser field propagation. It was found that in both cases the rate of stochastic heating of energetic electrons remains virtually the same. This work was supported by the USDOE Grant DE-NA0001858 at UCSD and Grant 14.Y26.31.008 of the MES of the Russian Federation at MEPhI.

  18. Two-dimensional Lagrangian calculation of a laser-heated solenoid

    NASA Astrophysics Data System (ADS)

    Makomaski, A. H.; Pietrzyk, Z. A.

    1980-02-01

    A two-dimensional Lagrangian code is used to model a laser-heated solenoid. The results indicate important two-dimensional effects and the global behavior of the plasma is found to be different from the predictions of one-dimensional theories. Most of the laser energy transferred to the plasma appears in the form of internal energy, suggesting that the bleaching wave approach for reactor calculations is correct. The plasma parameters are significantly changed when the peak of the laser beam profile is flattened.

  19. Substrate heating and emitter dopant effects in laser-annealed solar cells

    NASA Astrophysics Data System (ADS)

    Young, R. T.; Wood, R. F.; Christie, W. H.; Jellison, G. E., Jr.

    1981-08-01

    Experimental evidence is presented to demonstrate that substrate heating during pulsed-laser annealing (PLA) of ion-implanted silicon can significantly improve the electrical properties of the laser-recrystallized region, due to regrowth velocity reduction. Use of the optimum PLA condition shows qualitative agreement with theoretical predictions in that (1) the open-circuit voltage and fill factor of ion-implanted, laser-annealed solar cells are improved by the increase of emitter dopant concentrations, while (2) the short-circuit current remains fairly constant.

  20. Time-resolved X-ray conversion efficiencies of laser-heated plasmas

    NASA Astrophysics Data System (ADS)

    Ze, F.; Kauffman, R. L.; Lasinski, B.; Suter, L.; Langer, S.; Kornblum, H.; Tietbohl, G.; Thiessen, T.; Montgomery, D.; Drake, R. P.

    Experiments to obtain time-resolved, soft X-ray emission from laser-driven plasmas are succinctly described. The spectra (0.19 keV less than or equal to h nu 1.3 keV) at various times have been deconvolved and energy-integrated to obtain time-resolved yields from Au disk targets. The temporal profiles of the total thermal X-ray output power follow the overall laser temporal shape but do not show the high frequency fluctuation observed in the laser pulse. The behavior of the ratio of the instantaneous X-ray yields over the laser absorption is studied. The studies were done at the LLNL Nova laser facility. Single-pulse and pulses in picket fence configuration were used to heat gold targets.

  1. Time-resolved x-ray conversion efficiencies of laser-heated plasmas

    NASA Astrophysics Data System (ADS)

    Ze, F.; Kauffman, R. L.; Lasinski, B.; Suter, L.; Langer, S.; Kornblum, H.; Tietbohl, G.; Thiessen, T.; Montgomery, D.; Drake, R. P.; Campbell, E. M.

    1988-08-01

    Experiments to obtain time-resolved, soft-x-ray emission from laser-driven plasmas are succinctly described. The spectra (0.19 keV ≤ hν ≤ 1.3 keV) at various times have been deconvolved and energy integrated to obtain time-resolved yields from Au disk targets. The temporal profiles of the total thermal x-ray output power follow the overall laser temporal shape but do not show the high-frequency fluctuation observed in the laser pulse. The behavior of the ratio of the instantaneous x-ray yields over the laser absorption is studied. The studies were done at the LLNL Nova laser facility. Single pulses and pulses in ``picket fence'' configuration were used to heat the gold targets.

  2. Energy balance between vaporization and heating in the absorption of CO2 laser radiation by water

    NASA Astrophysics Data System (ADS)

    Mueller, Robert E.; Yam, Henry; Duley, Walter W.

    1997-03-01

    The use of lasers in industrial and medical procedures continues to increase. A fundamental question in many laser- material interactions is how is the incident laser power transferred to the target material, and how is the power distributed among the phases (solid, liquid, vapor) of the material. This paper describes the results of a fundamental calorimetry experiment to determine the fraction of incident carbon-dioxide laser energy which is used to vaporize water from a target volume, and the fraction of power used to simply heat the remaining liquid. The experiment was performed over a range of incident laser powers from 60 to 300 W. Over most of the range of incident power, the fraction used to vaporize water is 30 to 35 percent. This fraction increases at the lowest powers.

  3. The birth and development of laser heating in diamond anvil cells

    NASA Astrophysics Data System (ADS)

    Bassett, William A.

    2001-02-01

    In 1968 Taro Takahashi and I observed a phase transition that resulted from laser heating under pressure in a diamond anvil cell. Using a ruby laser, we successfully converted graphite to diamond. We soon realized that the ruby laser had such limited capabilities that we acquired a yttrium-aluminum-garnet (YAG) laser that could be used in both continuous and pulsed modes. The road to successfully applying the technique was not without a few bumps. Thirty years later, these seem more amusing than they did at the time. It was with the YAG laser that Ming and Liu investigated a number of silicate phase transitions important to our understanding of the earth's mantle. Since then it has been gratifying to watch as others have adopted the technique and made many important contributions with it.

  4. 980-nm, 15-W cw laser diodes on F-mount-type heat sinks

    SciTech Connect

    Bezotosnyi, V V; Krokhin, O N; Oleshchenko, V A; Pevtsov, V F; Popov, Yu M; Cheshev, E A

    2015-12-31

    We have studied the key optical emission parameters of laser diodes (emission wavelength, 980 nm; stripe contact width, 95 μm) mounted directly on F- and C-mount-type copper heat sinks, without intermediate elements (submounts). When effectively cooled by a thermoelectric microcooler, the lasers on the F-mount operated stably at output powers up to 20 W. The lasers were tested for reliable operation at an output power of 15 W for 100 h, and no decrease in output power was detected to within measurement accuracy. The experimentally determined maximum total efficiency is 71.7% and the efficiency at a nominal output power of 15 W is 61%. We compare parameters of the laser diodes mounted on C- and F-mounts and discuss the advantages of the F-mounts. (lasers)

  5. Structural changes in nanostructured catalytic oxides monitored by Raman spectroscopy: Effect of the laser heating

    NASA Astrophysics Data System (ADS)

    Oliveira, Alcemira C.; da Silva, Antonio N.; Junior, Jose Alves L.; Freire, Paulo T. C.; Oliveira, Alcineia C.; Filho, Josué M.

    2017-03-01

    The laser power effects on the structural properties of nanostructured oxides were studied by Raman spectroscopy. The nanostructured CeO2, ZrO2, SnO2, TiO2 and MnOx oxides were prepared by a nanocasting route and characterized through various physicochemical techniques. The structural features of the solids were accompanied by varying the incident laser power from 2.0 to 9.1 mW. The laser caused local heating on the surface of the nanostructured solids and influenced on their particle sizes. The CeO2, TiO2 and MnOx spectra exhibited particle size changes due to thermal effects. Elevated laser power up to 9.1 mW accelerated the sintering of CeO2, TiO2 and MnOx particles in contrast to SnO2 counterparts. Simultaneously, the creation of defects in the aforesaid oxide structures was suggested upon increasing the laser power from 2.0 to 9.1 mW. The phase transformation from MnOx-related phases to α-Mn2O3 and the oxidation of these phases were observed. Tetragonal ZrO2 showed a very stable structure under laser heating, envisaging further catalytic applications upon using mild laser power.

  6. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Effect of laser light on the kinetics of the oxidation of titanium films during heat treatment

    NASA Astrophysics Data System (ADS)

    Chaplanov, A. M.; Shibko, A. N.

    1993-02-01

    The application of laser light to materials in a heated state stimulates oxidation-reduction reactions in them. The illumination of titanium films by a beam of photons with hν =1.96 eV during annealing in vacuum stimulates photochemical processes of a nonthermal nature in addition to recrystallization.

  7. The numerical simulation of heat transfer during a hybrid laser-MIG welding using equivalent heat source approach

    NASA Astrophysics Data System (ADS)

    Bendaoud, Issam; Matteï, Simone; Cicala, Eugen; Tomashchuk, Iryna; Andrzejewski, Henri; Sallamand, Pierre; Mathieu, Alexandre; Bouchaud, Fréderic

    2014-03-01

    The present study is dedicated to the numerical simulation of an industrial case of hybrid laser-MIG welding of high thickness duplex steel UR2507Cu with Y-shaped chamfer geometry. It consists in simulation of heat transfer phenomena using heat equivalent source approach and implementing in finite element software COMSOL Multiphysics. A numerical exploratory designs method is used to identify the heat sources parameters in order to obtain a minimal required difference between the numerical results and the experiment which are the shape of the welded zone and the temperature evolution in different locations. The obtained results were found in good correspondence with experiment, both for melted zone shape and thermal history.

  8. Indirect Versus Direct Heating of Sheet Materials: Superplastic Forming and Diffusion Bonding Using Lasers

    NASA Astrophysics Data System (ADS)

    Jocelyn, Alan; Kar, Aravinda; Fanourakis, Alexander; Flower, Terence; Ackerman, Mike; Keevil, Allen; Way, Jerome

    2010-06-01

    Many from within manufacturing industry consider superplastic forming (SPF) to be ‘high tech’, but it is often criticized as too complicated, expensive, slow and, in general, an unstable process when compared to other methods of manipulating sheet materials. Perhaps, the fundamental cause of this negative perception of SPF, and also of diffusion bonding (DB), is the fact that the current process of SPF/DB relies on indirect sources of heating to produce the conditions necessary for the material to be formed. Thus, heat is usually derived from the electrically heated platens of hydraulic presses, to a lesser extent from within furnaces and, sometimes, from heaters imbedded in ceramic moulds. Recent evaluations of these isothermal methods suggest they are slow, thermally inefficient and inappropriate for the process. In contrast, direct heating of only the material to be formed by modern, electrically efficient, lasers could transform SPF/DB into the first choice of designers in aerospace, automotive, marine, medical, architecture and leisure industries. Furthermore, ‘variable temperature’ direct heating which, in theory, is possible with a laser beam(s) may provide a means to control material thickness distribution, a goal of enormous importance as fuel efficient, lightweight structures for transportation systems are universally sought. This paper compares, and contrasts, the two systems and suggests how a change to laser heating might be achieved.

  9. Laser-assisted heating of a plasmonic nanofluid in a microchannel

    NASA Astrophysics Data System (ADS)

    Walsh, Timothy

    The work presented in this study analyses the theoretical modeling and experimentation of laser-assisted heating of plasmonic nanofluids (PNFs) in a microchannel for accurate, efficient, and ultra-fast heating of a microdroplet. Suspended plasmonic nanoparticles exhibit strong light absorption and scattering upon the excitation of localized surface plasmons (LSPs), resulting in intense and rapid photothermal heating. Several multi-stepped computational models were utilized to theoretically characterize and verify the laser-assisted heating behavior of gold nanoshells (GNS) and gold nanorod (GNR) plasmonic nanofluid droplets in a microchannel. From the experimental investigation, a full range of controllable steady-state temperatures, room temperature to 100°C, are confirmed to be achievable for the 780-nm-tuned plasmonic nanofluid. Droplet fluid heating is verified to occur as a result of LSP excitation, in time scales of milliseconds, and to be repeatable over many cycles. Additionally, the significance and effects of parameters in the process, such as nanoparticle structure, volumetric concentration, microchannel depth, and laser power density are established. The obtained results in this research may be integrated into other existing microfluidic technologies and biological techniques, such as the polymerase chain reaction, where accurate and ultra-fast heating of microdroplets in a microchannel can greatly improve efficiency.

  10. Heat generation caused by ablation of dental restorative materials with an ultra short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Braun, Andreas; Wehry, Richard; Brede, Olivier; Frentzen, Matthias; Schelle, Florian

    2011-03-01

    The aim of this study was to assess heat generation in dental restoration materials following laser ablation using an Ultra Short Pulse Laser (USPL) system. Specimens of phosphate cement (PC), ceramic (CE) and composite (C) were used. Ablation was performed with an Nd:YVO4 laser at 1064 nm and a pulse length of 8 ps. Heat generation during laser ablation depended on the thickness of the restoration material. A time delay for temperature increase was observed in the PC and C group. Employing the USPL system for removal of restorative materials, heat generation has to be considered.

  11. Inverse bremsstrahlung heating rate for dense plasmas in laser fields

    NASA Astrophysics Data System (ADS)

    Dey, R.; Roy, A. C.

    2013-07-01

    We report a theoretical analysis of inverse bremsstrahlung heating rate in the eikonal approximation. The present analysis is performed for a dense plasma using the screened electron-ion interaction potential for the ion charge state Zi = 1 and for both the weak and strong plasma screening cases. We have also compared the eikonal results with the first Born approximation (FBA) [M. Moll et al., New J. Phys. 14, 065010 (2012)] calculation. We find that the magnitudes of inverse bremsstrahlung heating rate within the eikonal approximation (EA) are larger than the FBA values in the weak screening case (κ = 0.03 a.u.) in a wide range of field strength for three different initial electron momenta (2, 3, and 4 a.u.). But for strong screening case (κ = 0.3 a.u.), the heating rates predicted by the two approximations do not differ much after reaching their maximum values. Furthermore, the individual contribution of photoemission and photoabsorption processes to heating rate is analysed for both the weak and strong screening cases. We find that the single photoemission and photoabsorption rates are the same throughout the field strength while the multiphoton absorption process dominates over the multiphoton emission process beyond the field strength ≈ 4×108 V/cm. The present study of the dependence of heating rate on the screening parameter ranging from 0.01 to 20 shows that whereas the heating rate predicted by the EA is greater than the FBA up to the screening parameter κ = 0.3 a.u., the two approximation methods yield results which are nearly identical beyond the above value.

  12. Inverse bremsstrahlung heating rate for dense plasmas in laser fields

    SciTech Connect

    Dey, R.; Roy, A. C.

    2013-07-15

    We report a theoretical analysis of inverse bremsstrahlung heating rate in the eikonal approximation. The present analysis is performed for a dense plasma using the screened electron-ion interaction potential for the ion charge state Z{sub i} = 1 and for both the weak and strong plasma screening cases. We have also compared the eikonal results with the first Born approximation (FBA) [M. Moll et al., New J. Phys. 14, 065010 (2012)] calculation. We find that the magnitudes of inverse bremsstrahlung heating rate within the eikonal approximation (EA) are larger than the FBA values in the weak screening case (κ = 0.03 a.u.) in a wide range of field strength for three different initial electron momenta (2, 3, and 4 a.u.). But for strong screening case (κ = 0.3 a.u.), the heating rates predicted by the two approximations do not differ much after reaching their maximum values. Furthermore, the individual contribution of photoemission and photoabsorption processes to heating rate is analysed for both the weak and strong screening cases. We find that the single photoemission and photoabsorption rates are the same throughout the field strength while the multiphoton absorption process dominates over the multiphoton emission process beyond the field strength ≈ 4×10{sup 8} V/cm. The present study of the dependence of heating rate on the screening parameter ranging from 0.01 to 20 shows that whereas the heating rate predicted by the EA is greater than the FBA up to the screening parameter κ = 0.3 a.u., the two approximation methods yield results which are nearly identical beyond the above value.

  13. Voltage generation of piezoelectric cantilevers by laser heating

    PubMed Central

    Hsieh, Chun-Yi; Liu, Wei-Hung; Chen, Yang-Fang; Shih, Wan Y.; Gao, Xiaotong; Shih, Wei-Heng

    2012-01-01

    Converting ambient thermal energy into electricity is of great interest in harvesting energy from the environment. Piezoelectric cantilevers have previously been shown to be an effective biosensor and a tool for elasticity mapping. Here we show that a single piezoelectric (lead-zirconate titanate (PZT)) layer cantilever can be used to convert heat to electricity through pyroelectric effect. Furthermore, piezoelectric-metal (PZT-Ti) bi-layer cantilever showed an enhanced induced voltage over the single PZT layer alone due to the additional piezoelectric effect. This type of device can be a way for converting heat energy into electricity. PMID:23258941

  14. Optimization of the design and mode of operation of a QD laser for reducing the heat-to-bitrate ratio

    SciTech Connect

    Zhukov, A. E. Savelyev, A. V.; Maximov, M. V.; Kryzhanovskaya, N. V.; Gordeev, N. Yu.; Shernyakov, Yu. M.; Payusov, A. S.; Nadtochiy, A. M.; Zubov, F. I.; Korenev, V. V.

    2013-08-15

    Heat dissipation under the high-speed modulation of quantum dot edge-emitting lasers is considered. It is shown that, for a given laser diode, there is a bias current at which the heat-to-bitrate ratio is minimized. Moreover, there exists a certain optimal optical loss of the laser cavity at which the lowest heat-to-bitrate ratio is provided for any design of edge-emitting lasers that can be fabricated from an epitaxial structure. The heat-to-bitrate ratio and the corresponding bitrate are numerically calculated and analytical expressions are derived. It is demonstrated that the heat-to-bitrate ratio of quantum dot edge-emitting lasers can be less than 0.4 pJ/bit at a bitrate exceeding 10 Gbit/s.

  15. Radiation temperature measurements in laser-heated hohlraums

    SciTech Connect

    Cobble, J.A.; Goldman, S.R.; Bessarab, A.V.; Kunin, A.V.; Tokarev, V.A.

    1997-11-01

    Two x-ray spectrographs have been used on the Trident laser at LANL to monitor the radiation temperature of small Au hohlraums. The cylindrical targets are smaller than 1 mm. The x radiation produced by {approximately} 400 J of 0.53-{micro}m laser light is detected with a 7-channel VNIIEF soft-x-ray spectrometer. Each channel employs a multi-layer mirror and a filter to limit the channel bandwidth to 1--3% of the channel energy. X rays are detected with calibrated Al x-ray diodes. A second spectrometer is based on a free-standing Au transmission grating for spectral dispersion and a multi-channel diamond photo-conductive device detector. The small hohlraum results are consistent with radiation temperatures exceeding 100 eV. Simple computer modeling shows that late in the plasma discharge, radiation of this temperature is emitted from the target.

  16. Soft x-ray spectra from laser heated lithium targets

    SciTech Connect

    Nica, Petru-Edward; Miyamoto, Shuji; Amano, Sho; Inoue, Takahiro; Shimoura, Atsusi; Kaku, Kakyo; Mochizuki, Takayasu

    2006-07-24

    The extreme ultraviolet emission characteristics of laser-produced lithium plasma are experimentally and theoretically investigated. Taking into account the target oxidation, the ion fractional populations are analyzed and the averaged plasma parameters are obtained. Theoretical results show an insignificant influence of oxygen on the temperature dependence of the lithium ion fractional number. A comparison between the theoretical spectrum for stationary and homogenous plasma and experiments shows a reasonable agreement.

  17. Laser surface modification of medical grade alloys for reduced heating in a magnetic resonance imaging environment

    SciTech Connect

    Benafan, O. E-mail: raj@ucf.edu; Vaidyanathan, R. E-mail: raj@ucf.edu; Chen, S.-Y.; Kar, A.

    2015-12-15

    Nanoscale surface modification of medical grade metallic alloys was conducted using a neodymium-doped yttrium aluminum garnet laser-based dopant diffusion technique. The objective of this approach was to minimize the induction heating by reducing the absorbed radio frequency field. Such an approach is advantageous in that the dopant is diffused into the alloy and is not susceptible to detachment or spallation as would an externally applied coating, and is expected to not deteriorate the mechanical and electrical properties of the base alloy or device. Experiments were conducted using a controlled environment laser system with the ability to control laser properties (i.e., laser power, spot size, and irradiation time) and dopant characteristics (i.e., temperature, concentration, and pressure). The reflective and transmissive properties of both the doped and untreated samples were measured in a radio frequency (63.86 MHz) magnetic field using a system comprising a high power signal generator, a localized magnetic field source and sensor, and a signal analyzer. The results indicate an increase in the reflectivity of the laser-treated samples compared to untreated samples. The effect of reflectivity on the heating of the alloys is investigated through a mathematical model incorporating Maxwell’s equations and heat conduction.

  18. Laser surface modification of medical grade alloys for reduced heating in a magnetic resonance imaging environment

    NASA Astrophysics Data System (ADS)

    Benafan, O.; Chen, S.-Y.; Kar, A.; Vaidyanathan, R.

    2015-12-01

    Nanoscale surface modification of medical grade metallic alloys was conducted using a neodymium-doped yttrium aluminum garnet laser-based dopant diffusion technique. The objective of this approach was to minimize the induction heating by reducing the absorbed radio frequency field. Such an approach is advantageous in that the dopant is diffused into the alloy and is not susceptible to detachment or spallation as would an externally applied coating, and is expected to not deteriorate the mechanical and electrical properties of the base alloy or device. Experiments were conducted using a controlled environment laser system with the ability to control laser properties (i.e., laser power, spot size, and irradiation time) and dopant characteristics (i.e., temperature, concentration, and pressure). The reflective and transmissive properties of both the doped and untreated samples were measured in a radio frequency (63.86 MHz) magnetic field using a system comprising a high power signal generator, a localized magnetic field source and sensor, and a signal analyzer. The results indicate an increase in the reflectivity of the laser-treated samples compared to untreated samples. The effect of reflectivity on the heating of the alloys is investigated through a mathematical model incorporating Maxwell's equations and heat conduction.

  19. Laser surface modification of medical grade alloys for reduced heating in a magnetic resonance imaging environment.

    PubMed

    Benafan, O; Chen, S-Y; Kar, A; Vaidyanathan, R

    2015-12-01

    Nanoscale surface modification of medical grade metallic alloys was conducted using a neodymium-doped yttrium aluminum garnet laser-based dopant diffusion technique. The objective of this approach was to minimize the induction heating by reducing the absorbed radio frequency field. Such an approach is advantageous in that the dopant is diffused into the alloy and is not susceptible to detachment or spallation as would an externally applied coating, and is expected to not deteriorate the mechanical and electrical properties of the base alloy or device. Experiments were conducted using a controlled environment laser system with the ability to control laser properties (i.e., laser power, spot size, and irradiation time) and dopant characteristics (i.e., temperature, concentration, and pressure). The reflective and transmissive properties of both the doped and untreated samples were measured in a radio frequency (63.86 MHz) magnetic field using a system comprising a high power signal generator, a localized magnetic field source and sensor, and a signal analyzer. The results indicate an increase in the reflectivity of the laser-treated samples compared to untreated samples. The effect of reflectivity on the heating of the alloys is investigated through a mathematical model incorporating Maxwell's equations and heat conduction.

  20. The role of radiation transport in the thermal response of semitransparent materials to localized laser heating

    SciTech Connect

    Colvin, Jeffrey; Shestakov, Aleksei; Stolken, James; Vignes, Ryan

    2011-03-09

    Lasers are widely used to modify the internal structure of semitransparent materials for a wide variety of applications, including waveguide fabrication and laser glass damage healing. The gray diffusion approximation used in past models to describe radiation cooling is not adequate for these materials, particularly near the heated surface layer. In this paper we describe a computational model based upon solving the radiation transport equation in 1D by the Pn method with ~500 photon energy bands, and by multi-group radiationdiffusion in 2D with fourteen photon energy bands. The model accounts for the temperature-dependent absorption of infrared laser light and subsequent redistribution of the deposited heat by both radiation and conductive transport. We present representative results for fused silica irradiated with 2–12 W of 4.6 or 10.6 µm laser light for 5–10 s pulse durations in a 1 mm spot, which is small compared to the diameter and thickness of the silica slab. Furthermore, we show that, unlike the case for bulk heating, in localized infrared laser heatingradiation transport plays only a very small role in the thermal response of silica.

  1. Observation of extremely strong shock waves in solids launched by petawatt laser heating

    NASA Astrophysics Data System (ADS)

    Lancaster, K. L.; Robinson, A. P. L.; Pasley, J.; Hakel, P.; Ma, T.; Highbarger, K.; Beg, F. N.; Chen, S. N.; Daskalova, R. L.; Freeman, R. R.; Green, J. S.; Habara, H.; Jaanimagi, P.; Key, M. H.; King, J.; Kodama, R.; Krushelnick, K.; Nakamura, H.; Nakatsutsumi, M.; MacKinnon, A. J.; MacPhee, A. G.; Stephens, R. B.; Van Woerkom, L.; Norreys, P. A.

    2017-08-01

    Understanding hydrodynamic phenomena driven by fast electron heating is important for a range of applications including fast electron collimation schemes for fast ignition and the production and study of hot, dense matter. In this work, detailed numerical simulations modelling the heating, hydrodynamic evolution, and extreme ultra-violet (XUV) emission in combination with experimental XUV images indicate shock waves of exceptional strength (200 Mbar) launched due to rapid heating of materials via a petawatt laser. We discuss in detail the production of synthetic XUV images and how they assist us in interpreting experimental XUV images captured at 256 eV using a multi-layer spherical mirror.

  2. Millimeter wave tokamak heating and current drive with a high power free electron laser

    SciTech Connect

    Thomassen, K.I.

    1987-01-01

    Experiments on microwave generation using a free electron laser (FEL) have shown this to be an efficient way to generate millimeter wave power in short, intense pulses. Short pulse FEL's have several advantages that make them attractive for application to ECR heating of tokamak fusion reactors. This paper reports on plans made to demonstrate the technology at the Microwave Tokamak Experiment (MTX) Facility.

  3. Single-crystal Brillouin spectroscopy with CO{sub 2} laser heating and variable q

    SciTech Connect

    Zhang, Jin S.; Bass, Jay D.; Zhu, Gaohua

    2015-06-15

    We describe a Brillouin spectroscopy system integrated with CO{sub 2} laser-heating and Raman spectroscopic capabilities. Temperature is determined by measurements of the grey-body thermal radiation emitted by the hot sample, with the system response calibrated relative to a standard tungsten ribbon lamp. High-pressure laser-heating Brillouin scattering measurements of acoustic velocities on liquid water and ice compressed in a diamond-anvil cell were performed at temperatures up to 2500 ± 150 K at high pressure. Single-crystal laser-heating Brillouin measurements were made on the (111) plane of San Carlos olivine at ∼13 GPa, 1300 ± 200 K. The pressure as measured by ruby fluorescence is shown to be within ±0.5 GPa of the pressure on the olivine sample during laser heating when KCl and KBr are used as pressure-transmitting media. In addition, the system is designed for continuously variable scattering angles from forward scattering (near 0° scattering angle) up to near back scattering (∼141°). This novel setup allows us to probe a wide range of wave vectors q for investigation of phonon dispersion on, for example, crystals with large unit cells (on the scale of hundreds of nm)

  4. Single-crystal Brillouin spectroscopy with CO2 laser heating and variable q

    NASA Astrophysics Data System (ADS)

    Zhang, Jin S.; Bass, Jay D.; Zhu, Gaohua

    2015-06-01

    We describe a Brillouin spectroscopy system integrated with CO2 laser-heating and Raman spectroscopic capabilities. Temperature is determined by measurements of the grey-body thermal radiation emitted by the hot sample, with the system response calibrated relative to a standard tungsten ribbon lamp. High-pressure laser-heating Brillouin scattering measurements of acoustic velocities on liquid water and ice compressed in a diamond-anvil cell were performed at temperatures up to 2500 ± 150 K at high pressure. Single-crystal laser-heating Brillouin measurements were made on the (111) plane of San Carlos olivine at ˜13 GPa, 1300 ± 200 K. The pressure as measured by ruby fluorescence is shown to be within ±0.5 GPa of the pressure on the olivine sample during laser heating when KCl and KBr are used as pressure-transmitting media. In addition, the system is designed for continuously variable scattering angles from forward scattering (near 0° scattering angle) up to near back scattering (˜141°). This novel setup allows us to probe a wide range of wave vectors q for investigation of phonon dispersion on, for example, crystals with large unit cells (on the scale of hundreds of nm).

  5. Mechanical Properties of Laser Heat Treated 6 mm Thick UHSS-Steel

    SciTech Connect

    Jaervenpaeae, Antti; Maentyjaervi, Kari; Maeaettae, Antti; Hietala, Mikko; Merklein, Marion; Karjalainen, Jussi

    2011-05-04

    In this work abrasion resistant (AR) steel with a sheet thickness of 6 mm was heat treated by a 4 kW Nd:YAG and a 4 kW Yb:Yag-laser, followed by self-quenching. In the delivered condition, test material blank (B27S) is water quenched from 920 deg. C. In this condition, fully martensitic microstructure provides excellent hardness of over 500 HB. The test material is referred to AR500 from now onwards. Laser heat treatment was carried out only on top surface of the AR500 sheet: the achieved maximum temperature in the cross-section varies as a function of the depth. Consequently, the microstructure and mechanical properties differ between the surfaces and the centre of the cross-section (layered microstructure). For better understanding, all layers were tested in tensile tests. For a wide heat treatment track, the laser beam was moved by scanning. Temperatures were measured using thermographic camera and thermocouples. Laser heat treated AR500 samples were tested in hardness tests and by air bending using a press brake machine. Microstructures were studied using a light microscope and FE-SEM/SEM-EBSD. At least three kind of microstructure layers were observed: 1) Dual-Phase ferritic/martensitic (T = A{sub C1}-A{sub C3}), 2) ferritic (T{approx}A{sub C3}) and 3) bainitic/martensitic (T>A{sub C3}).

  6. Physical and mathematical models of the heat action of laser radiation on biotissues

    NASA Astrophysics Data System (ADS)

    Ivanov, Andrei V.; Molodykh, E. I.; Romanovsky, Yury M.; Schetinkina, T. A.; Borisov, D. V.

    1995-01-01

    A mathematical model of contact laser destruction of normal and tumor liver tissues by radiation of YAG:Nd laser is described. We present the results of the simulation of tissue heat destruction, taking into account the influence of blood and lymph circulation on the processes of heat transfer. The problem is adapted to the case of liver tissue with tumor. A liver is considered as a capillary-porous body with internal blood circulation. Heatconductivity and tissue-blood heat transfer are considered. Heat action is assumed to be implemented with contact laser scalpel. The mathematical model consists of two inhomogeneous nonlinear equations of heatconductivity with spherical symmetry. Nonstationary temperature fields of tissue and blood are determined. The power of laser radiation (LR) was taken into account in boundary conditions set for the center of coagulated tissue volume. We also took into account the processes connected with changing of substance phase (vaporization). The original computer programs allow one to solve the problem varying in a wide range of the main parameters. Reasonable agreement was found between the calculation results and the experimental data for operations on macrosamples and on test animals.

  7. Determining heat-transfer coefficients of solid objects by laser photothermal IR radiometry

    NASA Astrophysics Data System (ADS)

    Aleksandrov, S. E.; Gavrilov, G. A.; Kapralov, A. A.; Muratikov, K. L.; Sotnikova, G. Yu.

    2017-07-01

    A simple method for determining heat-transfer coefficients of solid objects is proposed that is based on direct measurement of the sample surface temperature dynamics. The object is probed by a laser beam with preset temporal variation of the radiation power, and the thermal response is detected by photodiodes operating in the mid-IR spectral range without forced cooling.

  8. Transmission line model for strained quantum well lasers including carrier transport and carrier heating effects.

    PubMed

    Xia, Mingjun; Ghafouri-Shiraz, H

    2016-03-01

    This paper reports a new model for strained quantum well lasers, which are based on the quantum well transmission line modeling method where effects of both carrier transport and carrier heating have been included. We have applied this new model and studied the effect of carrier transport on the output waveform of a strained quantum well laser both in time and frequency domains. It has been found that the carrier transport increases the turn-on, turn-off delay times and damping of the quantum well laser transient response. Also, analysis in the frequency domain indicates that the carrier transport causes the output spectrum of the quantum well laser in steady state to exhibit a redshift which has a narrower bandwidth and lower magnitude. The simulation results of turning-on transients obtained by the proposed model are compared with those obtained by the rate equation laser model. The new model has also been used to study the effects of pump current spikes on the laser output waveforms properties, and it was found that the presence of current spikes causes (i) wavelength blueshift, (ii) larger bandwidth, and (iii) reduces the magnitude and decreases the side-lobe suppression ratio of the laser output spectrum. Analysis in both frequency and time domains confirms that the new proposed model can accurately predict the temporal and spectral behaviors of strained quantum well lasers.

  9. Numerical estimation of phase transformations in solid state during Yb:YAG laser heating of steel sheets

    SciTech Connect

    Kubiak, Marcin Piekarska, Wiesława; Domański, Tomasz; Saternus, Zbigniew; Stano, Sebastian

    2015-03-10

    This work concerns the numerical modeling of heat transfer and phase transformations in solid state occurring during the Yb:YAG laser beam heating process. The temperature field is obtained by the numerical solution into transient heat transfer equation with convective term. The laser beam heat source model is developed using the Kriging interpolation method with experimental measurements of Yb:YAG laser beam profile taken into account. Phase transformations are calculated on the basis of Johnson - Mehl - Avrami (JMA) and Koistinen - Marburger (KM) kinetics models as well as continuous heating transformation (CHT) and continuous cooling transformation (CCT) diagrams for S355 steel. On the basis of developed numerical algorithms 3D computer simulations are performed in order to predict temperature history and phase transformations in Yb:YAG laser heating process.

  10. Surface-selective laser sintering of thermolabile polymer particles using water as heating sensitizer

    NASA Astrophysics Data System (ADS)

    Antonov, E. N.; Krotova, L. I.; Minaev, N. V.; Minaeva, S. A.; Mironov, A. V.; Popov, V. K.; Bagratashvili, V. N.

    2015-11-01

    We report the implementation of a novel scheme for surface-selective laser sintering (SSLS) of polymer particles, based on using water as a sensitizer of laser heating and sintering of particles as well as laser radiation at a wavelength of 1.94 μm, corresponding to the strong absorption band of water. A method of sintering powders of poly(lactide-co-glycolide), a hydrophobic bioresorbable polymer, after modifying its surface with an aqueous solution of hyaluronic acid is developed. The sintering thresholds for wetted polymer are by 3 - 4 times lower than those for sintering in air. The presence of water restricts the temperature of the heated polymer, preventing its thermal destruction. Polymer matrices with a developed porous structure are obtained. The proposed SSLS method can be applied to produce bioresorbable polymer matrices for tissue engineering.

  11. Analysis of laser ablation dynamics of CFRP in order to reduce heat affected zone

    NASA Astrophysics Data System (ADS)

    Sato, Yuji; Tsukamoto, Masahiro; Nariyama, Tatsuya; Nakai, Kazuki; Matsuoka, Fumihiro; Takahashi, Kenjiro; Masuno, Shinichiro; Ohkubo, Tomomasa; Nakano, Hitoshi

    2014-03-01

    A carbon fiber reinforced plastic [CFRP], which has high strength, light weight and weather resistance, is attractive material applied for automobile, aircraft and so on. The laser processing of CFRP is one of suitable way to machining tool. However, thermal affected zone was formed at the exposure part, since the heat conduction property of the matrix is different from that of carbon fiber. In this paper, we demonstrated that the CFRP plates were cut with UV nanosecond laser to reduce the heat affected zone. The ablation plume and ablation mass were investigated by laser microscope and ultra-high speed camera. Furthermore, the ablation model was constructed by energy balance, and it was confirmed that the ablation rate was 0.028 μg/ pulse in good agreement with the calculation value of 0.03 μg/ pulse.

  12. Interferometric measurement of laser heating in praseodymium-doped YAG crystal.

    PubMed

    Farley, Carlton W; Reddy, B Rami

    2011-02-01

    Temperature measurement is required for many applications but can be difficult in some cases. Laser heating or cooling studies demand accurate measurements of temperature changes. A Michelson interferometer configuration has been used to investigate laser heating in solids. An analytical formula was derived to estimate the temperature change from the fringe count by taking into account the temperature dependence of the sample length and refractive index. When 115 mW of a focused Ar+ laser beam (488 nm) passes through a Pr(3+)-doped YAG sample, its temperature increased by 11.7±1.0 K along the beam path due to nonradiative relaxation. The power dependence of the fringe count/movement was recorded. The temperature change was estimated by the interferometric method and is in agreement with that measured by a thermocouple.

  13. Interferometric measurement of laser heating in praseodymium-doped YAG crystal

    SciTech Connect

    Farley, Carlton W. III; Reddy, B. Rami

    2011-02-01

    Temperature measurement is required for many applications but can be difficult in some cases. Laser heating or cooling studies demand accurate measurements of temperature changes. A Michelson interferometer configuration has been used to investigate laser heating in solids. An analytical formula was derived to estimate the temperature change from the fringe count by taking into account the temperature dependence of the sample length and refractive index. When 115 mW of a focused Ar{sup +} laser beam (488 nm) passes through a Pr{sup 3+}-doped YAG sample, its temperature increased by 11.7{+-}1.0 K along the beam path due to nonradiative relaxation. The power dependence of the fringe count/movement was recorded. The temperature change was estimated by the interferometric method and is in agreement with that measured by a thermocouple.

  14. Influence of heat input on HAZ liquation cracking in laser welded GH909 alloy

    NASA Astrophysics Data System (ADS)

    Yan, Fei; Hu, Chongjing; Zhang, Xiong; Cai, Yuanzheng; Wang, Chunming; Wang, Jun; Hu, Xiyuan

    2017-07-01

    In this paper, we describe influence of heat input on HAZ liquation cracking in laser welded GH909 alloy. The results demonstrated that more cracks were produced using high laser power and welding speed. The presence of cracks greatly weakened the hot ductility of this material and the binding force between the adjacent grains, resulting in reducing the tensile strength of welded joints. The occurrence of HAZ cracking was mainly attributable to the coarseness of microstructures and large tensile stresses. A new method was proposed to prevent HAZ liquation cracking using low laser power and welding speed at a constant heat input. The simulated results were consistent with the experimental results, verifying the correctness and feasibility of the method.

  15. Laser-assisted photothermal heating of a plasmonic nanoparticle-suspended droplet in a microchannel.

    PubMed

    Walsh, Timothy; Lee, Jungchul; Park, Keunhan

    2015-03-07

    The present article reports the numerical and experimental investigations on the laser-assisted photothermal heating of a nanoliter-sized droplet in a microchannel when plasmonic particles are suspended in the droplet. Plasmonic nanoparticles exhibit strong light absorption and scattering upon the excitation of localized surface plasmons (LSPs), resulting in intense and rapid photothermal heating in a microchannel. Computational models are implemented to theoretically verify the photothermal behavior of gold nanoshell (GNS) and gold nanorod (GNR) particles suspended in a liquid microdroplet. Experiments were conducted to demonstrate rapid heating of a sub-100 nL droplet up to 100 °C with high controllability and repeatability. The heating and cooling time to the steady state is on the order of 1 second, while cooling requires less time than heating. The effects of core parameters, such as nanoparticle structure, volumetric concentration, microchannel depth, and laser power density on heating are studied. The obtained results can be integrated into existing microfluidic technologies that demand accurate and rapid heating of microdroplets in a microchannel.

  16. Heat transfer and thermal lensing in large-mode high-power laser diodes

    NASA Astrophysics Data System (ADS)

    Chan, Paddy K. L.; Pipe, Kevin P.; Plant, Jason J.; Swint, Reuel B.; Juodawlkis, Paul W.

    2007-02-01

    In semiconductor lasers, key parameters such as threshold current, efficiency, wavelength, and lifetime are closely related to temperature. These dependencies are especially important for high-power lasers, in which device heating is the main cause of decreased performance and failure. Heat sources such as non-radiative recombination in the active region typically cause the temperature to be highly peaked within the device, potentially leading to large refractive index variation with bias. Here we apply high-resolution charge-coupled device (CCD) thermoreflectance to generate two dimensional (2D) maps of the facet temperatures of a high power laser with 500 nm spatial resolution. The device under test is a slab-coupled optical waveguide laser (SCOWL) which has a large single mode and high power output. These characteristics favor direct butt-coupling the light generated from the laser diode into a single mode optical fiber. From the high spatial resolution temperature map, we can calculate the non-radiative recombination power and the optical mode size by thermal circuit and finite-element model (FEM) respectively. Due to the thermal lensing effect at high bias, the size of the optical mode will decrease and hence the coupling efficiency between the laser diode and the single mode fiber increases. At I=10I th, we found that the optical mode size has 20% decrease and the coupling efficiency has 10% increase when comparing to I=2I th. This suggests SCOWL is very suitable fr optical communication system.

  17. Influence of non-collisional laser heating on the electron dynamics in dielectric materials

    NASA Astrophysics Data System (ADS)

    Barilleau, L.; Duchateau, G.; Chimier, B.; Geoffroy, G.; Tikhonchuk, V.

    2016-12-01

    The electron dynamics in dielectric materials induced by intense femtosecond laser pulses is theoretically addressed. The laser driven temporal evolution of the energy distribution of electrons in the conduction band is described by a kinetic Boltzmann equation. In addition to the collisional processes for energy transfer such as electron-phonon-photon and electron-electron interactions, a non-collisional process for photon absorption in the conduction band is included. It relies on direct transitions between sub-bands of the conduction band through multiphoton absorption. This mechanism is shown to significantly contribute to the laser heating of conduction electrons for large enough laser intensities. It also increases the time required for the electron distribution to reach the equilibrium state as described by the Fermi-Dirac statistics. Quantitative results are provided for quartz irradiated by a femtosecond laser pulse with a wavelength of 800 nm and for intensities in the range of tens of TW cm-2, lower than the ablation threshold. The change in the energy deposition induced by this non-collisional heating process is expected to have a significant influence on the laser processing of dielectric materials.

  18. Numerical Investigation of Radiative Heat Transfer in Laser Induced Air Plasmas

    NASA Technical Reports Server (NTRS)

    Liu, J.; Chen, Y. S.; Wang, T. S.; Turner, James E. (Technical Monitor)

    2001-01-01

    Radiative heat transfer is one of the most important phenomena in the laser induced plasmas. This study is intended to develop accurate and efficient methods for predicting laser radiation absorption and plasma radiative heat transfer, and investigate the plasma radiation effects in laser propelled vehicles. To model laser radiation absorption, a ray tracing method along with the Beer's law is adopted. To solve the radiative transfer equation in the air plasmas, the discrete transfer method (DTM) is selected and explained. The air plasma radiative properties are predicted by the LORAN code. To validate the present nonequilibrium radiation model, several benchmark problems are examined and the present results are found to match the available solutions. To investigate the effects of plasma radiation in laser propelled vehicles, the present radiation code is coupled into a plasma aerodynamics code and a selected problem is considered. Comparisons of results at different cases show that plasma radiation plays a role of cooling plasma and it lowers the plasma temperature by about 10%. This change in temperature also results in a reduction of the coupling coefficient by about 10-20%. The present study indicates that plasma radiation modeling is very important for accurate modeling of aerodynamics in a laser propelled vehicle.

  19. Inverse bremsstrahlung heating beyond the first Born approximation for dense plasmas in laser fields

    NASA Astrophysics Data System (ADS)

    Moll, M.; Schlanges, M.; Bornath, Th; Krainov, V. P.

    2012-06-01

    Inverse bremsstrahlung (IB) heating, an important process in the laser-matter interaction, involves two different kinds of interaction—the interaction of the electrons with the external laser field and the electron-ion interaction. This makes analytical approaches very difficult. In a quantum perturbative approach to the IB heating rate in strong laser fields, usually the first Born approximation with respect to the electron-ion potential is considered, whereas the influence of the electric field is taken exactly in the Volkov wave functions. In this paper, a perturbative treatment is presented adopting a screened electron-ion interaction potential. As a new result, we derive the momentum-dependent, angle-averaged heating rate in the first Born approximation. Numerical results are discussed for a broad range of field strengths, and the conditions for the applicability of a linear approximation for the heating rate are analyzed in detail. Going a step further in the perturbation series, we consider the transition amplitude in the second Born approximation, which enables us to calculate the heating rate up to the third order of the interaction strength.

  20. Heat management prevents tissue buckling and collateral damage in NIR-laser welding

    NASA Astrophysics Data System (ADS)

    Sriramoju, Vidyasagar; Savage, Howard E.; Halder, Rabindra; Rosen, Richard B.; Katz, A.; Alfano, R. R.

    2006-02-01

    In this study, a NIR erbium fiber laser tuned to a water vibrational overtone absorption band at 1455 nm was used to weld directly, in vitro, seventy-six porcine aorta tissues without the need for extrinsic solder materials. The tissues were divided into eleven groups based on the multiple and variable parameters that were used to weld the tissues. The effectiveness of the parameters used in each of the weld groups was evaluated directly at the time of the weld and also by tensile strength measurements done at the termination of the weld. Management of heat produced in tissues is of critical importance for good laser tissue welding (LTW). To address heat management issues, we report LTW using a transparent cover over the tissue specimen as a heat sink. Multiple scanning helps distribute the laser-generated heat and allows the tissue to cool between scans, reducing thermal damage. Better heat management using a transparent cover slide enhances the welding success. It reduces collateral damage and limits water evaporation and control the buckling of tissue around the line of apposition so that the two pieces that are welded do not move apart along the line of apposition due to buckling pressure and ensure a full-length weld.

  1. Laser heating of scanning probe tips for thermal near-field spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    O'Callahan, Brian T.; Raschke, Markus B.

    2017-02-01

    Spectroscopy and microscopy of the thermal near-field yield valuable insight into the mechanisms of resonant near-field heat transfer and Casimir and Casimir-Polder forces, as well as providing nanoscale spatial resolution for infrared vibrational spectroscopy. A heated scanning probe tip brought close to a sample surface can excite and probe the thermal near-field. Typically, tip temperature control is provided by resistive heating of the tip cantilever. However, this requires specialized tips with limited temperature range and temporal response. By focusing laser radiation onto AFM cantilevers, we achieve heating up to ˜1800 K, with millisecond thermal response time. We demonstrate application to thermal infrared near-field spectroscopy (TINS) by acquiring near-field spectra of the vibrational resonances of silicon carbide, hexagonal boron nitride, and polytetrafluoroethylene. We discuss the thermal response as a function of the incident excitation laser power and model the dominant cooling contributions. Our results provide a basis for laser heating as a viable approach for TINS, nanoscale thermal transport measurements, and thermal desorption nano-spectroscopy.

  2. Using laser radiation for the formation of capillary structure in flat ceramic heat pipes

    NASA Astrophysics Data System (ADS)

    Nikolaenko, Yu. E.; Rotner, S. M.

    2012-12-01

    The possibility of using laser radiation with a wavelength of 1.064 μm for the formation of a capillary structure in the evaporation zone of flat ceramic heat pipes has been experimentally confirmed. Using a technological regime with established parameters, a capillary structure was formed in AlN and Al2O3 ceramic plates with a thickness of 1-2 mm and lateral dimensions of 48 × 60 and 100 × 100 mm, which ensured absorption of heat-transfer fluids (distilled water, ethyl alcohol, acetone) to a height of 100 mm against gravity forces. The thermal resistance of flat ceramic heat pipes with this capillary structure reaches 0.07°C/W, which is quite acceptable for their use as heat sinks in systems of thermal regime control for electronic components and as heat exchange plates for large-size thermoelectric conversion units.

  3. Characterization of a heat flux sensor using short pulse laser calibration.

    PubMed

    Löhle, Stefan; Battaglia, Jean-Luc; Batsale, Jean-Christophe; Enouf, Olivier; Dubard, Jimmy; Filtz, Jean-Remy

    2007-05-01

    A method to calibrate classical heat flux sensors is presented. The classical approach to measure the temperature inside a known material by using a thermocouple fails when the measurement time is very short. In this work the surface heat flux is determined by solving the inverse heat conduction problem using a noninteger identified system as a direct model for the estimation process. Using short pulse laser calibration measurements the crucial design aspects of the sensor that play a significant role when assuming one-dimensional, semi-infinite heat transfer have been accounted for. The theoretical approach as well as the calibration results are presented and comparisons to the classical approach and results from finite element modeling are shown. It is concluded that the new method ameliorate the heat flux sensor significantly and extend its application to very short measurement times.

  4. Comprehensive analytical model for CW laser induced heat in turbid media.

    PubMed

    Erkol, Hakan; Nouizi, Farouk; Luk, Alex; Unlu, Mehmet Burcin; Gulsen, Gultekin

    2015-11-30

    In this work, we present a new analytical approach to model continuous wave laser induced temperature in highly homogeneous turbid media. First, the diffusion equation is used to model light transport and a comprehensive solution is derived analytically by obtaining a special Greens' function. Next, the time-dependent bio-heat equation is used to describe the induced heat increase and propagation within the medium. The bio-heat equation is solved analytically utilizing the separation of variables technique. Our theoretical model is successfully validated using numerical simulations and experimental studies with agarose phantoms and ex-vivo chicken breast samples. The encouraging results show that our method can be implemented as a simulation tool to determine important laser parameters that govern the magnitude of temperature rise within homogenous biological tissue or organs.

  5. Comprehensive analytical model for CW laser induced heat in turbid media

    PubMed Central

    Erkol, Hakan; Nouizi, Farouk; Luk, Alex; Unlu, Mehmet Burcin; Gulsen, Gultekin

    2015-01-01

    In this work, we present a new analytical approach to model continuous wave laser induced temperature in highly homogeneous turbid media. First, the diffusion equation is used to model light transport and a comprehensive solution is derived analytically by obtaining a special Greens’ function. Next, the time-dependent bio-heat equation is used to describe the induced heat increase and propagation within the medium. The bio-heat equation is solved analytically utilizing the separation of variables technique. Our theoretical model is successfully validated using numerical simulations and experimental studies with agarose phantoms and ex-vivo chicken breast samples. The encouraging results show that our method can be implemented as a simulation tool to determine important laser parameters that govern the magnitude of temperature rise within homogenous biological tissue or organs. PMID:26698736

  6. Electron-phonon equilibration in laser-heated gold films

    NASA Astrophysics Data System (ADS)

    White, T. G.; Mabey, P.; Gericke, D. O.; Hartley, N. J.; Doyle, H. W.; McGonegle, D.; Rackstraw, D. S.; Higginbotham, A.; Gregori, G.

    2014-07-01

    By irradiating a thin metal foil with an intense short-pulse laser, we have created a uniform system far from equilibrium. The deposited energy is initially deposited only within the electronic subsystem, and the subsequent evolution of the system is determined by the details of the electron-phonon coupling. Here, we measure the time evolution of the lattice parameter through multilayer Bragg diffraction and compare the result to classical molecular dynamic simulations to determine the lattice temperature. The electron-ion coupling constant for gold is then determined by comparison with the evolution of a two-temperature electron-phonon system.

  7. Raman Studies of Surface Temperature in Laser-Heated Semiconductors.

    DTIC Science & Technology

    1985-02-07

    and A. Compaan, Appi. Phys. Lett. 38, 3 (1981). 3. M. C. Lee, It. W. Lo, A. Aydinli , and A. Compaan, Appl. Phys. Lett. 38, 7 (1981). 4. A. Compaan, H...W. Lo, A. Aydinli , and M. C. Lee, Laser and Electron- Beam Solid Interactions and Materials Procesin ed. by Gibbons. Hess and Sigmon (Elsevier North...Holland, Amsterdam, 1981), p. 15. ~.A. Aydinli , H. W. La, M. C. Lee, and A. Comnpaan, Phys. Rev. Lett. 4 46, 25 (1981). 6. A. Aydinli , A. Compaan, H

  8. Heating dynamics of CO{sub 2}-laser irradiated silica particles with evaporative shrinking: Measurements and modeling

    SciTech Connect

    Elhadj, S.; Qiu, S. R.; Stolz, C. J.; Monterrosa, A. M.

    2012-05-01

    The heating dynamics of CO{sub 2}-laser heated micron-sized particles were determined for temperatures <3500 K measured using infrared imaging. A coupled mass and energy conservation model is derived to predict single particle temperatures and sizes, which were compared with data from particles deposited on non-absorbing substrates to assess the relevant heat transfer processes. Analysis reveals substrate conduction dominates all other heat losses, while laser absorption determined from Mie theory is strongly modulated by particle evaporative shrinking. This study provides insights into the light coupling and heating of particle arrays where the material optical properties are temperature-dependent and particle size changes are significant.

  9. Human cadaver retina model for retinal heating during corneal surgery with a femtosecond laser

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Fan, Zhongwei; Yun, Jin; Zhao, Tianzhuo; Yan, Ying; Kurtz, Ron M.; Juhasz, Tibor

    2014-02-01

    Femtosecond lasers are widely used in everyday clinical procedures to perform minimally invasive corneal refractive surgery. The intralase femtosecond laser (AMO Corp. Santa Ana, CA) is a common example of such a laser. In the present study a numerical simulation was developed to quantify the temperature rise in the retina during femtosecond intracorneal surgery. Also, ex-vivo retinal heating due to laser irradiation was measured with an infrared thermal camera (Fluke Corp. Everett, WA) as a validation of the simulation. A computer simulation was developed using Comsol Multiphysics to calculate the temperature rise in the cadaver retina during femtosecond laser corneal surgery. The simulation showed a temperature rise of less than 0.3 degrees for realistic pulse energies for the various repetition rates. Human cadaver retinas were irradiated with a 150 kHz Intralase femtosecond laser and the temperature rise was measured withan infrared thermal camera. Thermal camera measurements are in agreement with the simulation. During routine femtosecond laser corneal surgery with normal clinical parameters, the temperature rise is well beneath the threshold for retina damage. The simulation predictions are in agreement with thermal measurements providing a level of experimental validation.

  10. Heat-Pipe Bismuth Laser; Examination of Laser Action at 4722A in Bismuth Vapor

    DTIC Science & Technology

    1976-11-01

    Terminating Laser Transitions in Calcium and Strontium. " IEEE J. Quantum Electron. QE-4, 474 (1968). 7. P.Cahuzac, "Raies Laser Infrarouges dans les Vapeurs... Spectroscopy 19. 282(1065). 13. P.A. Rice and D. V. Ragone, "Simultaneous Determination of f Values and Vapor Pressures from Optical Absorption Measurements...approaching 10%6. Beam foil spectroscopy can be included with these more accurate methods if one can be certain that there is no unrecognized

  11. Laser resection of lung tissue: heat accumulation from adjacent laser application and how to cool it down.

    PubMed

    Kirschbaum, Andreas; Rexin, Peter; Pehl, Anika; Bartsch, Detlef; Quint, Karl

    2014-06-01

    Heat accumulation might induce thermal damage of the surrounding lung tissue, especially when multiple lesions are resected in one session. The present study aimed to investigate whether heat accumulates in the immediate vicinity of the resection surface and leads to thermal damage of the lung parenchyma, and what is the most effective cooling strategy in this situation. In normothermic perfused paracardial swine lobes (n = 6), four punctiform laser lesions forming a square were created. Each lesion was lasered at a power of 100 W for 5 seconds. Two test conditions with square sides of either 1.0 or 0.5 cm were compared. Temperatures were recorded immediately after completing the laser procedure in the square center and in the corners using a thermal camera and continued during the cooling process at 10-second intervals until normothermia (37°C). We examined two cooling methods: rinsing with ice-cold (4°C) Ringer solution during the laser procedure (group B, n = 6) or submerging the lung in ice-cold water for 5 seconds immediately after laser application (group C, n = 6). In the control group A (n = 6), there was no cooling. In the 0.5 cm squares, mean temperature in the center immediately after laser application was 103.17 ± 8.56°C, significantly higher than in the corners (76.39 ± 2.87°C, p < 0.05). Normothermia in the quadrant corners was reached after 81 ± 14 and after 108 ± 29 seconds in the centers. Tissue in the square center revealed histological signs of thermic cell damage. In the 1.0 cm squares, mean temperature in the center was 64 ± 5°C, and in the corners was 77 ± 3.1°C (p < 0.05). Normothermia was regained after 93 ± 22 seconds in the center and 120 ± 21 seconds in the corners. Histological examination in the 1.0-quadrant centers revealed no signs of thermic cell damage. Submerging the lobe into ice-cold water lowered the temperature rapidly to under 40°C, and

  12. Modelling and simulation of the lubricant depletion process induced by laser heating in heat-assisted magnetic recording system

    NASA Astrophysics Data System (ADS)

    Wu, Lin

    2007-05-01

    A model for lubricant flow dynamics under a scanning laser beam has been constructed for a heat-assisted magnetic recording system. The effects of evaporation, thermocapillary stress and thermoviscosity on the lubricant depletion on both glass and aluminium disks are systematically studied. Our results indicate that both evaporation and thermocapillary stress are able to deplete non-negligible amount of Z-type PFPE lubricants with a low molecular weight from the disk surface within nanoseconds. Evaporation is the dominant lubricant removal mechanism when low molecular weight lubricant is used. Evaporation is significantly reduced when high molecular weight PFPE lubricants are used. Our simulations show that the performance of head/disk interface of heat-assisted magnetic recording systems may be significantly deteriorated when lubricants with improper properties are used.

  13. Spectroscopic models for laser-heated silicon and copper nanoparticles

    NASA Astrophysics Data System (ADS)

    Daun, Kyle; Menser, Jan; Mansmann, Raphael; Moghaddam, Sina Talabi; Dreier, Thomas; Schulz, Christof

    2017-08-01

    Interpreting laser-induced incandescence (LII) measurements on aerosolized nanoparticles requires a spectroscopic model that relates the measured spectral incandescence to the temperature of the nanoparticles. We present spectroscopic models for molten silicon and copper nanoparticles, which are evaluated through extinction and incandescence measurements on nanoaerosols. Measurements on molten silicon nanoparticles are consistent with the Drude theory in the Rayleigh limit of Mie theory. The copper nanoparticles were initially assumed to coalesce into spheres, but the observed spectral incandescence does not show a surface plasmon polariton (SPP) peak in the vicinity of 600 nm expected of spheres. A simulation based on the discrete dipole approximation (DDA) suggests that this effect could be explained by the structure of the copper aggregates.

  14. Heating of a sample with a laser pulse

    NASA Astrophysics Data System (ADS)

    Logvinov, G. N.; Drogobitskiy, Yu. V.; de Rivera, Luis Niño; Gurevich, Yu. G.

    2007-05-01

    The transient temperature associated with the bulk absorption of a rectangular laser pulse in a solidstate sample of finite size is calculated analytically and analyzed. Radiation is incident on the frontal surface with an arbitrary surface thermal conductivity. The opposite surface is thermostatically controlled and maintained at a constant equilibrium temperature. The general solution is obtained for pulses of arbitrary duration. The pulse duration is determined with respect to the relaxation time of the nonstationary thermal diffusion (it is the characteristic time of the problem). The limiting cases of the adiabatic insulation and isothermal contact at the frontal surface are considered, and the criteria for surface and bulk light absorption are derived for both cases. The temperature distributions are numerically simulated and examined for long and short pulses, as well as for different values of the light absorption coefficient and the surface thermal conductivity of the frontal surface.

  15. Conversion of heat to light using Townes' maser-laser engine: Quantum optics and thermodynamic analysis

    SciTech Connect

    Ooi, C. H. Raymond

    2011-04-15

    It is shown that thermal energy from a heat source can be converted to useful work in the form of maser-laser light by using a combination of a Stern-Gerlach device and stimulated emissions of excited particles in a maser-laser cavity. We analyze the populations of atoms or quantum dots exiting the cavity, the photon statistics, and the internal entropy as a function of atomic transit time, using the quantum theory of masers and lasers. The power of the laser light is estimated to be sufficiently high for device applications. The thermodynamics of the heat converter is analyzed as a heat engine operating between two reservoirs of different temperature but is generalized to include the change of internal quantum states. The von Neumann entropies for the internal degree are obtained. The sum of the internal and external entropies increases after each cycle and the second law is not violated, even if the photon entropy due to finite photon number distribution is not included. An expression for efficiency relating to the Carnot efficiency is obtained. We resolve the subtle paradox on the reduction of the internal entropy with regards to the path separation after the Stern-Gerlach device.

  16. X-ray Emissivities from Well Characterized Underdense, Laser-Heated Gas Targets

    SciTech Connect

    Fournier, K B; Back, C A; Constantin, C; Miller, M C; Suter, L J; Chung, H

    2004-06-18

    Maximizing the conversion efficiency (CE) of laser energy into multi-keV x-rays is a general concern to many areas of high-energy-density plasma physics. Bright x-ray sources are needed for backlighters in order to radiograph targets in inertial-confinement fusion (ICF) experiments. As the targets get larger, and as compression in the targets increases, the backlighter sources need to be brighter and the backlighter-photon energies must increase. To this end, for a given laser power, backlighters can become brighter by becoming more efficient at converting the drive beams to multi-keV x-rays. Volumetric heating of low-density gas targets has been shown to be a very efficient method of producing x-rays. Recently, laser heating of an underdense aerogel target has demonstrated efficient x-ray production. Ongoing experiments are optimizing these designs; this paper reports on detailed calculations of the x-ray yield from L-shell Kr in laser-heated targets.

  17. Probing heat diffusion after pulsed-laser-induced breakdown in a metal vapor

    SciTech Connect

    Zapka, W.; Tam, A.C.

    1982-02-01

    We have used a pulsed dye-laser beam at 6010 A, of 1-..mu..sec duration and < or approx. =1-mJ energy, to produce a line plasma in a Cs metal vapor. This produces a line source of large thermal energy. The heat diffusion after the laser pulse can be studied by transmission monitoring of a weak cw He--Ne laser beam that is parallel to but separated from the pulse laser beam by an adjustable displacement. This is possible because the He--Ne beam is absorbed by the minority Cs/sub 2/ molecules but not by the majority Cs atoms; as the heat pulse diffuses through the probe beam, the transient temperature increase causes a corresponding change in the population distribution of the Cs/sub 2/ molecules and hence a transient increase in transmission of the probe beam. In other words, the Cs/sub 2/ workd like a thermometer. Our work demonstrates a new and simple method to measure heat diffusion in a well-defined geometry, and it is especially suitable for use in a hot corrosive system because it is a noncontact method.

  18. Ionization heating in rare-gas clusters under intense XUV laser pulses

    SciTech Connect

    Arbeiter, Mathias; Fennel, Thomas

    2010-07-15

    The interaction of intense extreme ultraviolet (XUV) laser pulses ({lambda}=32 nm, I=10{sup 11}-10{sup 14} W/cm{sup 2}) with small rare-gas clusters (Ar{sub 147}) is studied by quasiclassical molecular dynamics simulations. Our analysis supports a very general picture of the charging and heating dynamics in finite samples under short-wavelength radiation that is of relevance for several applications of free-electron lasers. First, up to a certain photon flux, ionization proceeds as a series of direct photoemission events producing a jellium-like cluster potential and a characteristic plateau in the photoelectron spectrum as observed in Bostedt et al. [Phys. Rev. Lett. 100, 133401 (2008)]. Second, beyond the onset of photoelectron trapping, nanoplasma formation leads to evaporative electron emission with a characteristic thermal tail in the electron spectrum. A detailed analysis of this transition is presented. Third, in contrast to the behavior in the infrared or low vacuum ultraviolet range, the nanoplasma energy capture proceeds via ionization heating, i.e., inner photoionization of localized electrons, whereas collisional heating of conduction electrons is negligible up to high laser intensities. A direct consequence of the latter is a surprising evolution of the mean energy of emitted electrons as function of laser intensity.

  19. Heat generation above break-even from laser-induced fusion in ultra-dense deuterium

    SciTech Connect

    Holmlid, Leif

    2015-08-15

    Previous results from laser-induced processes in ultra-dense deuterium D(0) give conclusive evidence for ejection of neutral massive particles with energy >10 MeV u{sup −1}. Such particles can only be formed from nuclear processes like nuclear fusion at the low laser intensity used. Heat generation is of interest for future fusion energy applications and has now been measured by a small copper (Cu) cylinder surrounding the laser target. The temperature rise of the Cu cylinder is measured with an NTC resistor during around 5000 laser shots per measured point. No heating in the apparatus or the gas feed is normally used. The fusion process is suboptimal relative to previously published studies by a factor of around 10. The small neutral particles H{sub N}(0) of ultra-dense hydrogen (size of a few pm) escape with a substantial fraction of the energy. Heat loss to the D{sub 2} gas (at <1 mbar pressure) is measured and compensated for under various conditions. Heat release of a few W is observed, at up to 50% higher energy than the total laser input thus a gain of 1.5. This is uniquely high for the use of deuterium as fusion fuel. With a slightly different setup, a thermal gain of 2 is reached, thus clearly above break-even for all neutronicity values possible. Also including the large kinetic energy which is directly measured for MeV particles leaving through a small opening gives a gain of 2.3. Taking into account the lower efficiency now due to the suboptimal fusion process, previous studies indicate a gain of at least 20 during long periods.

  20. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Efficient heating of near-surface plasmas with femtosecond laser pulses stimulated by nanoscale inhomogeneities

    NASA Astrophysics Data System (ADS)

    Mikhailova, Yu M.; Platonenko, Viktor T.; Savel'ev, Andrei B.

    2005-01-01

    The interaction of intense (1016 - 1018 W cm-2) ultrashort (50-200 fs) laser pulses with the dense plasmas produced at the surfaces of the porous target is numerically simulated by the particle-in-cell technique. Nanostructure-enhanced absorption of femtosecond pulses in high-porous (P>4) targets is demonstrated. We show that the presence of plasma inhomogeneities essentially alters the heating of plasma electrons and ions; in particular, it stimulates the significant increase in the mean energy and number of hot electrons. The numerical investigation of the dynamics of plasma electrons made it possible to reveal the physical mechanisms behind their heating in a porous medium.

  1. Coupling statistics and heat transfer to study laser-induced crystal damage by nanosecond pulses.

    PubMed

    Duchateau, Guillaume; Dyan, Anthony

    2007-04-16

    By coupling statistics and heat transfer, we investigate numerically laser-induced crystal damage by multi-gigawatt nanosecond pulses. Our model is based on the heating of nanometric absorbing defects that may cooperate when sufficiently aggregated. In that configuration, they induce locally a strong increase of temperature that may lead to a subsequent damage. This approach allows to predict cluster size distribution and damage probabilities as a function of the laser fluence. By studying the influence of the pulse duration onto the laser-induced damage threshold, we have established scaling laws that link the critical laser fluence to its pulse duration tau. In particular, this approach provides an explanation to the deviation from the standard tau(1/2) scaling law that has been recently observed in laser-induced damage experiments with KH(2)PO(4) (KDP) crystals [J.J. Adams et al., Proc. of SPIE 5991, 5991R-1 (2005)]. In the present paper, despite the 3D problem is tackled, we focus our attention on a 1D modeling of thermal diffusion that is shown to provide more reliable predictions than the 3D one. These results indicate that absorbers involved in KDP damage may be associated with a collection of planar defects. First general comparisons with some experimental facts have been performed.

  2. Direct-drive Energetics of laser-Heated Foam Liners for Hohlraums

    NASA Astrophysics Data System (ADS)

    Moore, Alastair; Thomas, Cliff; Baker, Kevin; Morton, John; Baumann, Ted; Biener, Monika; Bhandarkar, Suhas; Hinkel, Denise; Jones, Oggie; Meezan, Nathan; Moody, John; Nikroo, Abbas; Rosen, Mordy; Hsing, Warren

    2016-10-01

    Lining the walls of a high-Z hohlraum cavity with a low-density foam is predicted to mitigate the challenge presented by hohlraum wall expansion. Once heated, wall material quickly fills the cavity and can impede laser beam propagation. To avoid this, ignition hohlraums are typically filled with a gas or irradiated with a short (< 10 ns) laser pulse. A gas-fill has the disadvantage that it can cause laser plasma instabilities (LPI), while a short laser pulse limits the design space to reach low-adiabat implosions. Foam-liners offer a potential route to reduce wall motion in a low gas-fill hohlraum with little LPI. Results from quasi 1-D experiments performed at the NIF are presented These characterize the x-ray conversion efficiency, backscattered laser energy and heat propagation in a 250 μm thick Ta2O5 or ZnO foam-liners spanning a range of densities from underdense to overdense, when irradiated at up to 4.9 x 1014 W/cm2 is incident on a planar foam sample, backed by a Au foil and generates a radiation temperature of up to 240eV - conditions equivalent to a single outer cone beam-spot in an ignition hohlraum. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  3. Managing tissue heating in laser therapy to enable double-blind clinical study

    NASA Astrophysics Data System (ADS)

    Catanzaro, Brian; de Taboada, Luis; Streeter, Jackson

    2006-02-01

    Laser devices in clinical applications must eventually be tested via clinical trials. An essential component in clinical trials is the double-blind study whereby the patient and the treating physician have no knowledge as to whether a given treatment is active or placebo. In pharmaceuticals, the problem is easily addressed. With laser therapy this can be very challenging. For some optical therapies, laser heating of tissue, by even as little as a few degrees can indicate to the patient and/or the physician that the device is active, un-blinding the study. This problem has been analyzed for a specific laser therapy using a combination of clinical data, analytical methods, finite element modeling, and laboratory testing. The methods used arrived at a solution, but not necessarily one that could have been predicted easily. This paper will present a model of tissue heating and the methods used to mask the effects from the laser in an effort to make active treatment and placebo indistinguishable.

  4. Implosion and heating experiments of fast ignition targets by Gekko-XII and LFEX lasers

    NASA Astrophysics Data System (ADS)

    Shiraga, H.; Fujioka, S.; Nakai, M.; Watari, T.; Nakamura, H.; Arikawa, Y.; Hosoda, H.; Nagai, T.; Koga, M.; Kikuchi, H.; Ishii, Y.; Sogo, T.; Shigemori, K.; Nishimura, H.; Zhang, Z.; Tanabe, M.; Ohira, S.; Fujii, Y.; Namimoto, T.; Sakawa, Y.; Maegawa, O.; Ozaki, T.; Tanaka, K. A.; Habara, H.; Iwawaki, T.; Shimada, K.; Key, M.; Norreys, P.; Pasley, J.; Nagatomo, H.; Johzaki, T.; Sunahara, A.; Murakami, M.; Sakagami, H.; Taguchi, T.; Norimatsu, T.; Homma, H.; Fujimoto, Y.; Iwamoto, A.; Miyanaga, N.; Kawanaka, J.; Kanabe, T.; Jitsuno, T.; Nakata, Y.; Tsubakimoto, K.; Sueda, K.; Kodama, R.; Kondo, K.; Morio, N.; Matsuo, S.; Kawasaki, T.; Sawai, K.; Tsuji, K.; Murakami, H.; Sarukura, N.; Shimizu, T.; Mima, K.; Azechi, H.

    2013-11-01

    The FIREX-1 project, the goal of which is to demonstrate fuel heating up to 5 keV by fast ignition scheme, has been carried out since 2003 including construction and tuning of LFEX laser and integrated experiments. Implosion and heating experiment of Fast Ignition targets have been performed since 2009 with Gekko-XII and LFEX lasers. A deuterated polystyrene shell target was imploded with the 0.53- μm Gekko-XII, and the 1.053- μm beam of the LFEX laser was injected through a gold cone attached to the shell to generate hot electrons to heat the imploded fuel plasma. Pulse contrast ratio of the LFEX beam was significantly improved. Also a variety of plasma diagnostic instruments were developed to be compatible with harsh environment of intense hard x-rays (γ rays) and electromagnetic pulses due to the intense LFEX beam on the target. Large background signals around the DD neutron signal in time-of-flight record of neutron detector were found to consist of neutrons via (γ,n) reactions and scattered gamma rays. Enhanced neutron yield was confirmed by carefully eliminating such backgrounds. Neutron enhancement up to 3.5 × 107 was observed. Heating efficiency was estimated to be 10-20% assuming a uniform temperature rise model.

  5. Time- and space- resolved pyrometry of dense plasmas heated by laser accelerated ion beams

    NASA Astrophysics Data System (ADS)

    Dyer, Gilliss; Roycroft, Rebecca; McCary, Eddie; Wagner, Craig; Jiao, Xuejing; Kupfer, Rotem; Gauthier, D. Cort; Bang, Woosuk; Palaniyappan, Sasikumar; Bradley, Paul A.; Hamilton, Christopher; Santiago Cordoba, Miguel A.; Vold, Erik L.; Yin, Lin; Fernandez, Juan C.; Alibright, Brian J.; Ditmire, Todd; Hegelich, Bjorn Manuel

    2016-10-01

    Laser driven ion sources have a variety of possible applications, including the rapid heating of matter to dense plasma states of several eV. Recent experiments at LANL and The University of Texas have explored ion heating in the context of mixing at high-Z / low-Z plasma interfaces, using different laser-based ion acceleration schemes. Quasi-monoenergetic and highly directed Al ions from ultra-thin foils were used in one set of experiments, while TNSA accelerated protons from an F/40 focused petawatt laser were used in the other. Using spatially and temporally resolved streaked optical pyrometry we have gained insight into the degree and uniformity of heating from various configurations of ion source and sample target. Here we present data and analysis from three experimental runs along with hydrodynamic modeling of the heated targets and geometric considerations. This work was supported by NNSA cooperative agreement DE- NA0002008 and the Los Alamos National Laboratory Directed Research and Development Program under the auspices of the U.S. DOE NNSAS, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-0.

  6. Enhanced Thermo-Optical Switching of Paraffin-Wax Composite Spots under Laser Heating.

    PubMed

    Said, Asmaa; Salah, Abeer; Fattah, Gamal Abdel

    2017-05-12

    Thermo-optical switches are of particular significance in communications networks where increasingly high switching speeds are required. Phase change materials (PCMs), in particular those based on paraffin wax, provide wealth of exciting applications with unusual thermally-induced switching properties, only limited by paraffin's rather low thermal conductivity. In this paper, the use of different carbon fillers as thermal conductivity enhancers for paraffin has been investigated, and a novel structure based on spot of paraffin wax as a thermo-optic switch is presented. Thermo-optical switching parameters are enhanced with the addition of graphite and graphene, due to the extreme thermal conductivity of the carbon fillers. Differential Scanning Calorimetry (DSC) and Scanning electron microscope (SEM) are performed on paraffin wax composites, and specific heat capacities are calculated based on DSC measurements. Thermo-optical switching based on transmission is measured as a function of the host concentration under conventional electric heating and laser heating of paraffin-carbon fillers composites. Further enhancements in thermo-optical switching parameters are studied under Nd:YAG laser heating. This novel structure can be used in future networks with huge bandwidth requirements and electric noise free remote aerial laser switching applications.

  7. Enhanced Thermo-Optical Switching of Paraffin-Wax Composite Spots under Laser Heating

    PubMed Central

    Said, Asmaa; Salah, Abeer; Abdel Fattah, Gamal

    2017-01-01

    Thermo-optical switches are of particular significance in communications networks where increasingly high switching speeds are required. Phase change materials (PCMs), in particular those based on paraffin wax, provide wealth of exciting applications with unusual thermally-induced switching properties, only limited by paraffin’s rather low thermal conductivity. In this paper, the use of different carbon fillers as thermal conductivity enhancers for paraffin has been investigated, and a novel structure based on spot of paraffin wax as a thermo-optic switch is presented. Thermo-optical switching parameters are enhanced with the addition of graphite and graphene, due to the extreme thermal conductivity of the carbon fillers. Differential Scanning Calorimetry (DSC) and Scanning electron microscope (SEM) are performed on paraffin wax composites, and specific heat capacities are calculated based on DSC measurements. Thermo-optical switching based on transmission is measured as a function of the host concentration under conventional electric heating and laser heating of paraffin-carbon fillers composites. Further enhancements in thermo-optical switching parameters are studied under Nd:YAG laser heating. This novel structure can be used in future networks with huge bandwidth requirements and electric noise free remote aerial laser switching applications. PMID:28772884

  8. Proton Beam Focusing and Heating in Petawatt Laser-Solid Interactions

    SciTech Connect

    Snavely, R A; Gu, P; King, J; Hey, D; Akli, K; Zhang, B B; Freeman, R; Hatchett, S; Key, M H; Koch, J; Langdon, A B; Lasinsky, B; MacKinnon, A; Patel, P; Town, R; Wilks, S; Stephens, R; Tsutsumi, T; Chen, Z; Yabuuchi, T; Kurahashi, T; Sato, T; Adumi, K; Toyama, Y; Zheng, J; Kodama, R; Tanaka, K A; Yamanaka, T

    2003-08-13

    It has recently been demonstrated that femtosecond-laser generated proton beams may be focused. These protons, following expansion of the Debye sheath, emit off the inner concave surface of hemispherical shell targets irradiated at their outer convex pole. The sheath normal expansion produces a rapidly converging proton beam. Such focused proton beams provide a new and powerful means to achieve isochoric heating to high temperatures. They are potentially important for measuring the equation of state of materials at high energy density and may provide an alternative route to fast ignition. We present the first results of proton focusing and heating experiments performed at the Petawatt power level at the Gekko XII Laser Facility at ILE Osaka Japan. Solid density Aluminum slabs are placed in the proton focal region at various lengths. The degree of proton focusing is measured via XUV imaging of Planckian emission of the heated zone. Simultaneous with the XUV measurement a streaked optical imaging technique, HISAK, gave temporal optical emission images of the focal region. Results indicate excellent coupling between the laser-proton conversion and subsequent heating.

  9. Effect of quantum correction on nonlinear thermal wave of electrons driven by laser heating

    NASA Astrophysics Data System (ADS)

    Nafari, F.; Ghoranneviss, M.

    2016-08-01

    In thermal interaction of laser pulse with a deuterium-tritium (DT) plane, the thermal waves of electrons are generated instantly. Since the thermal conductivity of electron is a nonlinear function of temperature, a nonlinear heat conduction equation is used to investigate the propagation of waves in solid DT. This paper presents a self-similar analytic solution for the nonlinear heat conduction equation in a planar geometry. The thickness of the target material is finite in numerical computation, and it is assumed that the laser energy is deposited at a finite initial thickness at the initial time which results in a finite temperature for electrons at initial time. Since the required temperature range for solid DT ignition is higher than the critical temperature which equals 35.9 eV, the effects of quantum correction in thermal conductivity should be considered. This letter investigates the effects of quantum correction on characteristic features of nonlinear thermal wave, including temperature, penetration depth, velocity, heat flux, and heating and cooling domains. Although this effect increases electron temperature and thermal flux, penetration depth and propagation velocity are smaller. This effect is also applied to re-evaluate the side-on laser ignition of uncompressed DT.

  10. External bleaching therapy with activation by heat, light or laser--a systematic review.

    PubMed

    Buchalla, Wolfgang; Attin, Thomas

    2007-05-01

    External bleaching procedures utilizing highly concentrated 30-35% hydrogen peroxide solutions or hydrogen peroxide releasing agents can be used for tooth whitening. To enhance or accelerate the whitening process, heat-activation of the bleaching agent by light, heat or laser is described in the literature. The aim of the present review article was to summarize and discuss the available information concerning the efficacy, effects and side effects of activated bleaching procedures. Information from all original scientific full papers or reviews listed in PubMed or ISI Web of Science (search term: (bleaching OR brightening OR whitening OR colour) AND (light OR laser OR heat OR activation)) were included in the review. Existing literature reveals that activation of bleaching agents by heat, light or laser may have an adverse effect on pulpal tissue due to an increase of intra-pulpal temperature exceeding the critical value of 5.5 degrees C. Available studies do not allow for a final judgment whether tooth whitening can either be increased or accelerated by additional activation. Therefore, application of activated bleaching procedures should be critically assessed considering the physical, physiological and patho-physiological implications.

  11. Effect of quantum correction on nonlinear thermal wave of electrons driven by laser heating

    SciTech Connect

    Nafari, F.; Ghoranneviss, M.

    2016-08-15

    In thermal interaction of laser pulse with a deuterium-tritium (DT) plane, the thermal waves of electrons are generated instantly. Since the thermal conductivity of electron is a nonlinear function of temperature, a nonlinear heat conduction equation is used to investigate the propagation of waves in solid DT. This paper presents a self-similar analytic solution for the nonlinear heat conduction equation in a planar geometry. The thickness of the target material is finite in numerical computation, and it is assumed that the laser energy is deposited at a finite initial thickness at the initial time which results in a finite temperature for electrons at initial time. Since the required temperature range for solid DT ignition is higher than the critical temperature which equals 35.9 eV, the effects of quantum correction in thermal conductivity should be considered. This letter investigates the effects of quantum correction on characteristic features of nonlinear thermal wave, including temperature, penetration depth, velocity, heat flux, and heating and cooling domains. Although this effect increases electron temperature and thermal flux, penetration depth and propagation velocity are smaller. This effect is also applied to re-evaluate the side-on laser ignition of uncompressed DT.

  12. Petri dish PCR: laser-heated reactions in nanoliter droplet arrays.

    PubMed

    Kim, Hanyoup; Vishniakou, Siarhei; Faris, Gregory W

    2009-05-07

    We report high-speed real-time PCR performed on an unmodified disposable polystyrene Petri dish. The reaction cycle relies solely on an infrared laser for heating; no conventional heater is required. Nanoliter droplets of PCR mixture as water-in-oil emulsions printed in an array format served as individual PCR microreactors. A simple contact printing technique was developed to generate a large array of uniform sized nanoliter droplets using disposable pipette tips. Printed droplets showed variation of less than 10% in volume and the oil/water/polystyrene interface formed a compact droplet microreactor approximately spherical in shape. The uniform droplet array was used to optimize the laser power required for the two heating steps of PCR, annealing/extension and melting, while the ambient conditions were at room temperature. The optical heating allows for an extremely fast heating rate due to the selective absorption of the infrared laser by PCR buffer only and not the oil or polystyrene Petri dish, allowing completion of 40 amplification cycles in approximately 6 minutes. The quantitative assay capability of the system is also presented and discussed.

  13. Noncontact sub-10 nm temperature measurement in near-field laser heating.

    PubMed

    Yue, Yanan; Chen, Xiangwen; Wang, Xinwei

    2011-06-28

    An extremely focused optical field down to sub-10 nm in an apertureless near-field scanning optical microscope has been used widely in surface nanostructuring and structure characterization. The involved sub-10 nm near-field heating has not been characterized quantitatively due to the extremely small heating region. In this work, we present the first noncontact thermal probing of silicon under nanotip focused laser heating at a sub-10 nm scale. A more than 200 °C temperature rise is observed under an incident laser of 1.2 × 10(7) W/m(2), while the laser polarization is well aligned with the tip axis. To explore the mechanism of heating and thermal transport at sub-10 nm scale, a simulation is conducted on the enhanced optical field by the AFM tip. The high intensity of the optical field generated in this region results in nonlinear photon absorption. The optical field intensity under low polarization angles (∼10(14) W/m(2) within 1 nm region for 15° and 30°) exceeds the threshold for avalanche breakdown in silicon. The measured high-temperature rise is a combined effect of the low thermal conductivity due to ballistic thermal transport and the nonlinear photon absorption in the enhanced optical field. Quantitative analysis reveals that under the experimental conditions the temperature rise can be about 235 and 105 °C for 15° and 30° laser polarization angles, agreeing well with the measurement result. Evaluation of the thermal resistances of the tip-substrate system concludes that little heat in the substrate can be transferred to the tip because of the very large thermal contact resistance between them.

  14. Model of a laser heated plasma interacting with walls arising in laser keyhole welding

    NASA Astrophysics Data System (ADS)

    Tix, C.; Simon, G.

    1994-07-01

    In laser welding with laser intensities of approximately 1011 W/m2, a hole, called a keyhole, is formed in the material. In this keyhole a plasma is detected, which is characterized by high pressure as well as being influenced by the boundary of the keyhole. Experimental data on plasma parameters are rare and difficult to obtain [W. Sokolowski, G. Herziger, and E. Beyer, in High Power Lasers and Laser Machining Technology, edited by A. Quenzer, SPIE Proc. Vol. 1132 (SPIE, Bellingham, WA, 1989), pp. 288-295]. In a previous paper [C. Tix and G. Simon, J. Phys. D 26, 2066 (1993)] we considered just a simple plasma model without excited states and with constant ion-neutral-atom temperature. Therefore we neglected radiative transport of excitations and underestimated the ion-neutral-atom temperature and the ionization rate. Here we extend our previous model for a continuous CO2 laser and iron and take into account radiative transfer of excitations and a variable ion-neutral-atom temperature. We consider singly charged ions, electrons, and three excitation states of neutral atoms. The plasma is divided in plasma bulk, presheath, and sheath. The transport equations are solved with boundary conditions mainly determined through the appearance of walls. Some effort is made to clarify the energy transport mechanism from the laser beam into the material. Dependent on the incident laser power, the mean electron temperature and density are obtained to be 1.0-1.3 eV and 2.5×1023-3×1023 m-3. Radiative transport of excitations does not contribute significantly to the energy transport.

  15. Effect of heat input on cracking in laser solid formed DZ4125 superalloy

    NASA Astrophysics Data System (ADS)

    Hu, Y. L.; Lin, X.; Song, K.; Jiang, X. Y.; Yang, H. O.; Huang, W. D.

    2016-12-01

    DZ4125 superalloy, which processes a high hot cracking sensitivity, is deposited on an as-cast substrate using laser solid forming (LSF) in order to investigate the effect of heat input on the cracking in the deposit and the heat affected zone (HAZ) in the substrate. It is shown that the liquation cracks occurred in LSFed sample with the lower heat input. The propagation extent of the cracks can be reduced with increasing the heat input. The crack-free deposits are achieved when the heat input reaches 150 J/mm. The variation of the residual stress in the LSFed sample with the heat input are discussed based on the micro-indentation analysis. It can be found that the elimination of the cracks with the high heat input can be attributed to the lower temperature gradient and thermal stresses in the LSFed sample. Besides, the backfilling of the liquid melt from the molten pool to the crack is also observed with the high heat input, which is also beneficial to the healing of crack in the HAZ of the molten pool.

  16. Thomson scattering measurements of heat flow in a laser-produced plasma

    NASA Astrophysics Data System (ADS)

    Hawreliak, J.; Chambers, D. M.; Glenzer, S. H.; Gouveia, A.; Kingham, R. J.; Marjoribanks, R. S.; Pinto, P. A.; Renner, O.; Soundhauss, P.; Topping, S.; Wolfrum, E.; Young, P. E.; Wark, J. S.

    2004-04-01

    Measurements of the electron distribution and heat flow between the critical and ablation surfaces in a laser-produced plasma have been obtained using Thomson scattering. A frequency-quadrupled probe beam was used to obtain Thomson spectra at above-critical densities in a plasma produced by irradiation of solid targets with the fundamental laser light at irradiances of 3 × 1014 W cm-2. Comparison of Thomson spectra at the ion acoustic frequency (sensitive to the cold return current) with simulated spectra shows that the data are consistent with Fokker-Planck simulations of the electron distribution function, providing the first direct information on the electron distribution function.

  17. Nonlinear collisional absorption and induced anisotropy in plasmas heated by an intense laser field

    NASA Astrophysics Data System (ADS)

    Bendib, A.

    2017-07-01

    The inverse bremsstrahlung absorption of a laser wave by electrons in homogeneous plasmas is investigated in the range α=v02/vt2≤2 , where v0 is the electron quiver velocity and vt is the thermal velocity. For α≪1 , previous results are recovered. In the range α≥1 , the interplay of collisional absorption and induced plasma anisotropy led to significant new results regarding the electron distribution function and the laser wave damping rate. By increasing α, the low-energy electron population increases, while the collisional absorption rate is still reduced. The temperature anisotropy induced by electron heating is also estimated.

  18. Laser remote heating in vacuum environment to study temperature dependence of optical properties for bulk materials

    NASA Astrophysics Data System (ADS)

    Minissale, Marco; Bisson, Regis; Gallais, Laurent

    2016-12-01

    The knowledge of optical and thermal properties of materials at high temperatures is of crucial importance in the field of high power laser/material interactions. We report in this contribution on the development of a spectroscopic ellipsometry system dedicated to the measurement of optical properties of solid materials from the ambient to high temperatures (<1000 K). The experimental setup is based on a fiber-coupled high power laser diodes system operating at 800 nm used as remote heating, a supercontinuum source as probing beam, a fiber-optic spectrometer to measure reflected light and optical pyrometers for temperature monitoring.

  19. Ultrafast electron diffraction from non-equilibrium phonons in femtosecond laser heated Au films

    NASA Astrophysics Data System (ADS)

    Chase, T.; Trigo, M.; Reid, A. H.; Li, R.; Vecchione, T.; Shen, X.; Weathersby, S.; Coffee, R.; Hartmann, N.; Reis, D. A.; Wang, X. J.; Dürr, H. A.

    2016-01-01

    We use ultrafast electron diffraction to detect the temporal evolution of non-equilibrium phonons in femtosecond laser-excited ultrathin single-crystalline gold films. From the time-dependence of the Debye-Waller factor, we extract a 4.7 ps time-constant for the increase in mean-square atomic displacements. The observed increase in the diffuse scattering intensity demonstrates that the energy transfer from laser-heated electrons to phonon modes near the X and K points in the Au fcc Brillouin zone proceeds with timescales of 2.3 and 2.9 ps, respectively, faster than the Debye-Waller average mean-square displacement.

  20. Ultrafast electron diffraction from non-equilibrium phonons in femtosecond laser heated Au films

    SciTech Connect

    Chase, T.; Trigo, M.; Reid, A. H.; Dürr, H. A.; Li, R.; Vecchione, T.; Shen, X.; Weathersby, S.; Coffee, R.; Hartmann, N.; Wang, X. J.; Reis, D. A.

    2016-01-25

    We use ultrafast electron diffraction to detect the temporal evolution of non-equilibrium phonons in femtosecond laser-excited ultrathin single-crystalline gold films. From the time-dependence of the Debye-Waller factor, we extract a 4.7 ps time-constant for the increase in mean-square atomic displacements. The observed increase in the diffuse scattering intensity demonstrates that the energy transfer from laser-heated electrons to phonon modes near the X and K points in the Au fcc Brillouin zone proceeds with timescales of 2.3 and 2.9 ps, respectively, faster than the Debye-Waller average mean-square displacement.

  1. Ultrafast electron diffraction from non-equilibrium phonons in femtosecond laser heated Au films

    SciTech Connect

    Chase, T.; Trigo, M.; Reid, A. H.; Li, R.; Vecchione, T.; Shen, X.; Weathersby, S.; Coffee, R.; Hartmann, N.; Reis, D. A.; Wang, X. J.; Dürr, H. A.

    2016-01-25

    We use ultrafast electron diffraction to detect the temporal evolution of non-equilibrium phonons in femtosecond laser-excited ultrathin single-crystalline gold films. From the time-dependence of the Debye-Waller factor, we extract a 4.7 ps time-constant for the increase in mean-square atomic displacements. The observed increase in the diffuse scattering intensity demonstrates that the energy transfer from laser-heated electrons to phonon modes near the X and K points in the Au fcc Brillouin zone proceeds with timescales of 2.3 and 2.9 ps, respectively, faster than the Debye-Waller average mean-square displacement.

  2. Heating process and damage threshold analysis of Au film coated on Cu substrate for femtosecond laser

    NASA Astrophysics Data System (ADS)

    Wang, Tingfeng; Guo, Jin; Shao, Junfeng; Sun, Tao; Chen, Anmin; Liu, Hang; Ding, Dajun

    2012-07-01

    The heating processes of a two-layer film assembly of Au padded with Cu irradiated by femtosecond laser pulse are studied using a two-temperature model. It is found that the chosen substantially influence the energy transport, and consequently the temperature variation, and thermal equilibrium time. At the same laser fluence, the different thickness of gold film leads to a change of gold surface temperature. By choosing the thickness of the gold layer in the two-layer film assemblies, the damage threshold of the gold film can be maximized. The results can be used to optimize the damage threshold of gold coating optical components.

  3. Rapid embedded wire heating via resistive guiding of laser-generated fast electrons as a hydrodynamic driver

    SciTech Connect

    Robinson, A. P. L.; Schmitz, H.; Pasley, J.

    2013-12-15

    Resistively guiding laser-generated fast electron beams in targets consisting of a resistive wire embedded in lower Z material should allow one to rapidly heat the wire to over 100 eV over a substantial distance without strongly heating the surrounding material. On the multi-ps timescale, this can drive hydrodynamic motion in the surrounding material. Thus, ultra-intense laser solid interactions have the potential as a controlled driver of radiation hydrodynamics in solid density material. In this paper, we assess the laser and target parameters needed to achieve such rapid and controlled heating of the embedded wire.

  4. Quantitative analysis of the local phase transitions induced by the laser heating

    SciTech Connect

    Levlev, Anton V.; Susner, Michael A.; McGuire, Michael A.; Maksymovych, Petro; Kalinin, Sergei V.

    2015-11-04

    Functional imaging enabled by scanning probe microscopy (SPM) allows investigations of nanoscale material properties under a wide range of external conditions, including temperature. However, a number of shortcomings preclude the use of the most common material heating techniques, thereby limiting precise temperature measurements. Here we discuss an approach to local laser heating on the micron scale and its applicability for SPM. We applied local heating coupled with piezoresponse force microscopy and confocal Raman spectroscopy for nanoscale investigations of a ferroelectric-paraelectric phase transition in the copper indium thiophosphate layered ferroelectric. Bayesian linear unmixing applied to experimental results allowed extraction of the Raman spectra of different material phases and enabled temperature calibration in the heated region. Lastly, the obtained results enable a systematic approach for studying temperature-dependent material functionalities in heretofore unavailable temperature regimes.

  5. Quantitative analysis of the local phase transitions induced by the laser heating

    DOE PAGES

    Levlev, Anton V.; Susner, Michael A.; McGuire, Michael A.; ...

    2015-11-04

    Functional imaging enabled by scanning probe microscopy (SPM) allows investigations of nanoscale material properties under a wide range of external conditions, including temperature. However, a number of shortcomings preclude the use of the most common material heating techniques, thereby limiting precise temperature measurements. Here we discuss an approach to local laser heating on the micron scale and its applicability for SPM. We applied local heating coupled with piezoresponse force microscopy and confocal Raman spectroscopy for nanoscale investigations of a ferroelectric-paraelectric phase transition in the copper indium thiophosphate layered ferroelectric. Bayesian linear unmixing applied to experimental results allowed extraction of themore » Raman spectra of different material phases and enabled temperature calibration in the heated region. Lastly, the obtained results enable a systematic approach for studying temperature-dependent material functionalities in heretofore unavailable temperature regimes.« less

  6. Melting of troilite at high pressure in a diamond cell by laser heating

    NASA Technical Reports Server (NTRS)

    Bassett, William A.; Weathers, Maura S.

    1987-01-01

    A system for measuring melting temperatures at high pressures is described. The sample is heated with radiation from a YAG laser. The beam is reflected downward through a microscope objective, through the upper diamond anvil, and focused onto the sample. Hense, intense heating is produced only at the sample and not within the diamond anvils. A vidicon system is used to observe the sample during heating. Incandescent light from the heated sample passes back through the objective lens into a grating spectrometer. The spectrum of the incandescent light is received by the photodiode array and stored in the multichannel analyzer. These data can then be transferred to floppy disk for analysis. A curve fitting program is used to compare the spectra with standard blackbody curves and to determine the temperature. Pressure is measured by the ruby fluorescence method. The system was used to study the melting behavior of natural troilite (FeS).

  7. The heat-pipe resembling action of boiling bubbles in endovenous laser ablation.

    PubMed

    van der Geld, Cees W M; van den Bos, Renate R; van Ruijven, Peter W M; Nijsten, Tamar; Neumann, H A Martino; van Gemert, Martin J C

    2010-11-01

    Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heat pipe, where very efficient heat transport maintains a constant temperature, the saturation temperature of 100 degrees C, over the volume where these non-condensing bubbles exist. During EVLA the above-mentioned observations indicate that a venous cylindrical volume with a length of about 20 mm is kept at 100 degrees C. Pullback velocities of a few mm/s then cause at least the upper part of the treated vein wall to remain close to 100 degrees C for a time sufficient to cause irreversible injury. In conclusion, we propose that the mechanism of action of boiling bubbles during EVLA is an efficient heat-pipe resembling way of heating of the vein wall.

  8. Photoactivation of neurons by laser-generated local heating

    NASA Astrophysics Data System (ADS)

    Migliori, Benjamin; Di Ventra, Massimiliano; Kristan, William

    2012-09-01

    We present a method for achieving temporally and spatially precise photoactivation of neurons without the need for genetic expression of photosensitive proteins. Our method depends upon conduction of thermal energy via absorption by chemically inert carbon particles and does not require the presence of voltage-gated channels to create transmembrane currents. We demonstrate photothermal initiation of action potentials in Hirudo verbana neurons within an intact ganglion and of transmembrane currents in Xenopus oocytes. Thermal energy is delivered by focused 50 ms, 650 nm laser pulses with total pulse energies between 250 and 3500 μJ. We document an optical delivery system for targeting specific neurons that can be expanded for multiple target sites. Our method achieves photoactivation reliably (70 - 90% of attempts) and can issue multiple pulses (6-9) with minimal changes to cellular properties as measured by intracellular recording. Direct photoactivation presents a significant step towards all-optical analysis of neural circuits in animals such as Hirudo verbana where genetic expression of photosensitive compounds is not feasible.

  9. Collisional and collision-less surface heating in intense laser matter interaction

    NASA Astrophysics Data System (ADS)

    Kemp, Andreas; Divol, Laurent

    2015-11-01

    We explore the interaction of high-contrast intense sub-100 fs laser pulses with solid density tar- gets, using numerically converged collisional particle-in-cell simulations in one two and three dimen- sions. We observe a competition between two mechanisms that can lead to plasma heating. Inverse bremsstrahlung at solid density on one hand, and electrons scattering off plasma waves on the other, can both heat the skin layer to keV temperatures on a femtosecond time scale, facilitating a heat wave and a source of MeV electrons that penetrate and heat the bulk target. Collision-less effects heat the surface effectively starting at the relativistic intensity threshold, independent of plasma density. Our numerical results show that a high-contrast 1J/100fs laser can drive a solid target into the warm dense matter regime. This system is suitable to ab-initio modeling and experimental probing. Work performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  10. Stationary bubble formation and Marangoni convection induced by CW laser heating of a single gold nanoparticle.

    PubMed

    Setoura, Kenji; Ito, Syoji; Miyasaka, Hiroshi

    2017-01-05

    Gold nanoparticles (Au NPs) efficiently convert incident light into heat under the resonant conditions of localized surface plasmon. Controlling mass transfer through plasmonic heating of Au NPs has potential applications such as manipulation and fabrication within a small space. Here, we describe the formation of stationary microbubbles and subsequent fluid convection induced by CW laser heating of Au NPs in water. Stationary bubbles of about 1-20 μm in diameter were produced by irradiating individual Au NPs with a CW laser. Spatial profiles and velocity distribution of fluid convection around the microbubbles were visualized by the wide-field fluorescence imaging of tracer nanospheres. To evaluate the bubble-induced convection, numerical simulations were performed on the basis of general heat diffusion and Navier-Stokes equations. A comparison between the experimental and computational results revealed that a temperature derivative of surface tension at the bubble surface is a key factor to control the fluid convection. Temperature differences of a few Kelvin at the bubble surface resulted in convective velocities ranging from 10(2) to 10(3) μm s(-1). The convective velocity gradually increased with increasing bubble diameter. This article covers both natural and Marangoni convection induced by plasmonic heating of Au NPs.

  11. Induction-linac based free-electron laser amplifiers for plasma heating

    SciTech Connect

    Jong, R.A.

    1988-08-22

    We describe an induction-linac based free-electron laser amplifier that is presently under construction at the Lawrence Livermore National Laboratory. It is designed to produce up to 2 MW of average power at a frequency of 250 GHz for plasma heating experiments in the Microwave Tokamak Experiment. In addition, we shall describe a FEL amplifier design for plasma heating of advanced tokamak fusion devices. This system is designed to produce average power levels of about 10 MW at frequencies ranging form 280 to 560 GHz. 7 refs., 1 tab.

  12. Induction-linac based free-electron laser amplifiers for plasma heating

    NASA Astrophysics Data System (ADS)

    Jong, R. A.

    1988-08-01

    We describe an induction-linac based free-electron laser amplifier that is presently under construction at the Lawrence Livermore National Laboratory. It is designed to produce up to 2 MW of average power at a frequency of 250 GHz for plasma heating experiments in the Microwave Tokamak Experiment. In addition, we shall describe a FEL amplifier design for plasma heating of advanced tokamak fusion devices. This system is designed to produce average power levels of about 10 MW at frequencies ranging from 280 to 560 GHz.

  13. Energy deposition, heat flow, and rapid solidification during laser and electron beam irradiation of materials

    SciTech Connect

    White, C.W.; Aziz, M.J.

    1985-10-01

    The fundamentals of energy deposition, heat flow, and rapid solidification during energy deposition from lasers and electron beams is reviewed. Emphasis is placed on the deposition of energy from pulsed sources (10 to 100 ns pulse duration time) in order to achieve high heating and cooling rates (10/sup 8/ to 10/sup 10/ /sup 0/C/s) in the near surface region. The response of both metals and semiconductors to pulsed energy deposition is considered. Guidelines are presented for the choice of energy source, wavelength, and pulse duration time.

  14. Electric current heating calibration of a laser holographic nondestructive test system

    NASA Technical Reports Server (NTRS)

    Liu, H.-K.; Kurtz, R. L.

    1975-01-01

    Holographic NDT was used to measure small surface displacements controlled by electric heating by detecting the difference of the interference fringe patterns as viewed through the hologram on a real time basis. A perforated aluminum test plate, with the holes used to position thin metal foils, was used in the experiment. One of the foils was connected to an electric power source and small displacements of the foil were caused and controlled by Ohmic heating. An He-Ne laser was used to perform the holography.

  15. Heat transfer and material flow during laser assisted multi-layer additive manufacturing

    SciTech Connect

    Manvatkar, V.; De, A.; DebRoy, T.

    2014-09-28

    A three-dimensional, transient, heat transfer, and fluid flow model is developed for the laser assisted multilayer additive manufacturing process with coaxially fed austenitic stainless steel powder. Heat transfer between the laser beam and the powder particles is considered both during their flight between the nozzle and the growth surface and after they deposit on the surface. The geometry of the build layer obtained from independent experiments is compared with that obtained from the model. The spatial variation of melt geometry, cooling rate, and peak temperatures is examined in various layers. The computed cooling rates and solidification parameters are used to estimate the cell spacings and hardness in various layers of the structure. Good agreement is achieved between the computed geometry, cell spacings, and hardness with the corresponding independent experimental results.

  16. A method to achieve rapid localised deep heating in a laser irradiated solid density target

    NASA Astrophysics Data System (ADS)

    Schmitz, H.; Robinson, A. P. L.

    2016-09-01

    Rapid heating of small buried regions by laser generated fast electrons may be useful for applications such as extreme ultraviolet (XUV) radiation sources or as drivers for shock experiments. In non-structured targets, the heating profile possesses a global maximum near the front surface. This paper presents a new target design that uses resistive guiding to concentrate the fast electron current density at a finite depth inside the target. The choice of geometry uses principles of non-imaging optics. A global temperature maximum at depths up to 50 μ m into the target is achieved. Although theoretical calculations suggest that small source sizes should perform better than large ones, simulations show that a large angular spread at high intensities results in significant losses of the fast electrons to the sides. A systematic parameter scan suggests an optimal laser intensity. A ratio of 1.6 is demonstrated between the maximum ion temperature and the ion temperature at the front surface.

  17. The effect of quantum correction on plasma electron heating in ultraviolet laser interaction

    NASA Astrophysics Data System (ADS)

    Zare, S.; Yazdani, E.; Sadighi-Bonabi, R.; Anvari, A.; Hora, H.

    2015-04-01

    The interaction of the sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in the collision frequency, the electron heating and the ion block generation in plasma are studied. It is found that due to the quantum correction, the electron heating increases considerably and the electron temperature uniformly reaches up to the maximum value of 4.91 × 107 K. Considering the quantum correction, the electron temperature at the laser initial coupling stage is improved more than 66.55% of the amount achieved in the classical model. As a consequence, by the modified collision frequency, the ion block is accelerated quicker with higher maximum velocity in comparison with the one by the classical collision frequency. This study proves the necessity of considering a quantum mechanical correction in the collision frequency at high plasma temperatures.

  18. Supersonic Heat Wave Propagation in Laser-Produced Underdense Plasma for Efficient X-Ray Generation

    SciTech Connect

    Tanabe, M; Nishimura, H; Fujioka, S; Nagai, K; Iwamae, A; Ohnishi, N; Fournier, K B; Girard, F; Primout, M; Villette, B; Tobin, M; Mima, K

    2008-06-12

    We have observed supersonic heat wave propagation in a low-density aerogel target ({rho} {approx} 3.2 mg/cc) irradiated at the intensity of 4 x 10{sup 14} W/cm{sup 2}. The heat wave propagation was measured with a time-resolved x-ray imaging diagnostics, and the results were compared with simulations made with the two-dimensional radiation-hydrodynamic code, RAICHO. Propagation velocity of the ionization front gradually decreased as the wave propagates into the target. The reason of decrease is due to increase of laser absorption region as the front propagates and interplay of hydrodynamic motion and reflection of laser propagation. These features are well reported with the simulation.

  19. The effect of quantum correction on plasma electron heating in ultraviolet laser interaction

    SciTech Connect

    Zare, S.; Sadighi-Bonabi, R. Anvari, A.; Yazdani, E.; Hora, H.

    2015-04-14

    The interaction of the sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in the collision frequency, the electron heating and the ion block generation in plasma are studied. It is found that due to the quantum correction, the electron heating increases considerably and the electron temperature uniformly reaches up to the maximum value of 4.91 × 10{sup 7 }K. Considering the quantum correction, the electron temperature at the laser initial coupling stage is improved more than 66.55% of the amount achieved in the classical model. As a consequence, by the modified collision frequency, the ion block is accelerated quicker with higher maximum velocity in comparison with the one by the classical collision frequency. This study proves the necessity of considering a quantum mechanical correction in the collision frequency at high plasma temperatures.

  20. A reaction cell with sample laser heating for in situ soft X-ray absorption spectroscopy studies under environmental conditions.

    PubMed

    Escudero, Carlos; Jiang, Peng; Pach, Elzbieta; Borondics, Ferenc; West, Mark W; Tuxen, Anders; Chintapalli, Mahati; Carenco, Sophie; Guo, Jinghua; Salmeron, Miquel

    2013-05-01

    A miniature (1 ml volume) reaction cell with transparent X-ray windows and laser heating of the sample has been designed to conduct X-ray absorption spectroscopy studies of materials in the presence of gases at atmospheric pressures. Heating by laser solves the problems associated with the presence of reactive gases interacting with hot filaments used in resistive heating methods. It also facilitates collection of a small total electron yield signal by eliminating interference with heating current leakage and ground loops. The excellent operation of the cell is demonstrated with examples of CO and H2 Fischer-Tropsch reactions on Co nanoparticles.

  1. Extreme Ultraviolet Imaging of Electron Heated Targets in Petawatt Laser Experiments

    SciTech Connect

    Ma, T; MacPhee, A; Key, M; Akli, K; Mackinnon, A; Chen, C; Barbee, T; Freeman, R; King, J; Link, A; Offermann, D; Ovchinnikov, V; Patel, P; Stephens, R; VanWoerkom, L; Zhang, B; Beg, F

    2007-11-29

    The study of the transport of electrons, and the flow of energy into a solid target or dense plasma, is instrumental in the development of fast ignition inertial confinement fusion. An extreme ultraviolet (XUV) imaging diagnostic at 256 eV and 68 eV provides information about heating and energy deposition within petawatt laser-irradiated targets. XUV images of several irradiated solid targets are presented.

  2. Thermal radiation of laser heated niobium clusters Nb(+)(N), 8 ⩽ N ⩽ 22.

    PubMed

    Hansen, Klavs; Li, Yejun; Kaydashev, Vladimir; Janssens, Ewald

    2014-07-14

    The thermal radiation from small, laser heated, positively charged niobium clusters has been measured. The emitted power was determined by the quenching effect on the metastable decay, employing two different experimental protocols. The radiative power decreases slightly with cluster size and shows no strong size-to-size variations. The magnitude is 40-50 keV/s at the timescale of several microseconds, which is the measured crossover time from evaporative to radiative cooling.

  3. Laser-Heated Floating Zone Production of Single-Crystal Fibers

    NASA Technical Reports Server (NTRS)

    Ritzert, Frank; Westfall, Leonard

    1996-01-01

    This report describes how a laser-heated floating zone apparatus can be used to investigate single-crystal fibers of various compositions. A feedrod with a stoichiometric composition of high-purity powders was connected to a pedestal and fed into a laser scan where it combined with a single-crystal fiber seed. A molten zone was formed at this junction. As the feedrod was continuously fed into the laser scan, a single-crystal fiber of a prescribed orientation was withdrawn from the melt. The resultant fibers, whose diameters ranged from 100 to 250 gm, could then be evaluated on the basis of their growth behavior, physical properties, mechanical properties, and fiber perfection.

  4. Material transport in laser-heated diamond anvil cell melting experiments

    NASA Technical Reports Server (NTRS)

    Campbell, Andrew J.; Heinz, Dion L.; Davis, Andrew M.

    1992-01-01

    A previously undocumented effect in the laser-heated diamond anvil cell, namely, the transport of molten species through the sample chamber, over distances large compared to the laser beam diameter, is presented. This effect is exploited to determine the melting behavior of high-pressure silicate assemblages of olivine composition. At pressures where beta-spinel is the phase melted, relative strengths of partitioning can be estimated for the incompatible elements studied. Iron was found to partition into the melt from beta-spinel less strongly than calcium, and slightly more strongly than manganese. At higher pressures, where a silicate perovskite/magnesiowuestite assemblage is melted, it is determined that silicate perovskite is the liquidus phase, with iron-rich magnesiowuestite accumulating at the end of the laser-melted stripe.

  5. Breathing, crawling, budding, and splitting of a liquid droplet under laser heating.

    PubMed

    Song, Chaeyeon; Moon, Jong Kyun; Lee, Kyuyong; Kim, Kipom; Pak, Hyuk Kyu

    2014-04-21

    The manipulation of droplets with sizes on the millimetre scale and below has attracted considerable attention over the past few decades for applications in microfluidics, biology, and chemistry. In this paper, we report the response of an oil droplet floating in an aqueous solution to local laser heating. Depending on the laser power, distinct dynamic transitions of the shape and motion of the droplet are observed, namely, breathing, crawling, budding, and splitting. We found that the selection of the dynamic modes is determined by dynamic instabilities due to the interplay between the convection flows and capillary effects. Our findings can be useful for constructing microfluidic devices to control the motion and shape of a small droplet by simply altering the laser power, and for understanding thermal convective systems with fully soft boundaries.

  6. High enthalpy arc-heated plasma flow diagnostics by tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Lin, Xin; Chen, Lianzhong; Zeng, Hui; Ou, Dongbin; Dong, Yonghui

    2017-05-01

    This paper reports the laser absorption measurements of atomic oxygen in the FD04 arc-heater at China Academy of Aerospace Aerodynamics (CAAA). An atomic oxygen absorption line at 777.19 nm is utilizied for detecting the population of electronically excited oxygen atom in an air plasma flow. A scanned-wavelength direct absorption mode is used in this study. The laser is scanned in wavelength across the absorption feature at a rate of 200 Hz. Under the assumption of thermal equilibrium, time-resolved temperature measurements are obtained on one line-of-sight in the arc-heater. The good agreement of the temperature inferred from the sonic throat method suggests the equilibrium assumption is valid. These results illustrate the feasibility of the diode laser sensors for flow parameters in high enthalpy arc-heated facilities.

  7. The rapid growth of vertically aligned carbon nanotubes using laser heating.

    PubMed

    Park, J B; Jeong, S H; Jeong, M S; Lim, S C; Lee, I H; Lee, Y H

    2009-05-06

    Growth of densely packed vertically aligned carbon nanotubes (VA-CNTs) using laser-induced chemical vapor deposition with visible laser (lambda = 532 nm) irradiation at room temperature is reported. Using a multiple-catalyst layer (Fe/Al/Cr) on quartz as the substrate and an acetylene-hydrogen mixture as the precursor gas, VA-CNT pillars with 60 microm height and 4 microm diameter were grown at a high rate of around 1 microm s(-1) with good reproducibility. It is demonstrated that the fabrication of uniform pillar arrays of VA-CNTs can be achieved with a single irradiation for each pillar using LCVD with no annealing or preprocessing of the substrate. Here, laser fast heating is considered the primary mechanism facilitating the growth of VA-CNT pillars. Field emission characteristics of an array of VA-CNT pillars were then examined to investigate their potential application in vacuum electronic devices.

  8. Material transport in laser-heated diamond anvil cell melting experiments

    NASA Technical Reports Server (NTRS)

    Campbell, Andrew J.; Heinz, Dion L.; Davis, Andrew M.

    1992-01-01

    A previously undocumented effect in the laser-heated diamond anvil cell, namely, the transport of molten species through the sample chamber, over distances large compared to the laser beam diameter, is presented. This effect is exploited to determine the melting behavior of high-pressure silicate assemblages of olivine composition. At pressures where beta-spinel is the phase melted, relative strengths of partitioning can be estimated for the incompatible elements studied. Iron was found to partition into the melt from beta-spinel less strongly than calcium, and slightly more strongly than manganese. At higher pressures, where a silicate perovskite/magnesiowuestite assemblage is melted, it is determined that silicate perovskite is the liquidus phase, with iron-rich magnesiowuestite accumulating at the end of the laser-melted stripe.

  9. Isochoric heating of reduced mass targets by ultra-intense laser produced relativistic electrons

    SciTech Connect

    Neumayer, P; Lee, H J; Offerman, D; Shipton, E; Kemp, A; Kritcher, A L; Doppner, T; Back, C A; Glenzer, S H

    2009-02-04

    We present measurements of the chlorine K-alpha emission from reduced mass targets, irradiated with ultra-high intensity laser pulses. Chlorinated plastic targets with diameters down to 50 micrometers and mass of a few 10{sup -8} g were irradiated with up to 7 J of laser energy focused to intensities of several 10{sup 19} W/cm{sup 2}. The conversion of laser energy to K-alpha radiation is measured, as well as high resolution spectra that allow observation of line shifts, indicating isochoric heating of the target up to 18 eV. A zero-dimensional 2-temperature equilibration model, combined with electron impact K-shell ionization and post processed spectra from collisional radiative calculations reproduces the observed K-alpha yields and line shifts, and shows the importance of target expansion due to the hot electron pressure.

  10. Oil fence arrangement

    SciTech Connect

    Muto, I.; Tatsuguchi, M.

    1984-01-10

    An oil fence arrangement for effectively preventing oil spills from spreading or diffusing over the surface of the sea. The arrangement is of a double wall construction and can fold into a small space.

  11. The effect of uniaxial tension on the stability of collagen fibers under the conditions of nonuniform laser heating

    NASA Astrophysics Data System (ADS)

    Zakharkina, O. L.; Ignat'eva, N. Yu.; Iksanov, R. R.; Kamenskii, V. A.; Sobol', E. N.; Lunin, V. V.

    2009-02-01

    Collagen degradation caused by IR laser irradiation in ligament tissues was studied by thermal analysis and cross-polarization optical coherent tomography. It was found that, at 60°C, laser-induced modification of the quasi-crystalline packing of ordered collagen fibers occurred without the helix-coil molecular conformation transition. It was shown that, for uniaxial tension of ligaments, laser irradiation caused serious distortions in the structure of collagen and increased the fraction of macromolecules in the random coil state. It was assumed that the thermomechanical effect of laser treatment during laser heating played an important role.

  12. Transient thermal and nonthermal electron and phonon relaxation after short-pulsed laser heating of metals

    SciTech Connect

    Giri, Ashutosh; Hopkins, Patrick E.

    2015-12-07

    Several dynamic thermal and nonthermal scattering processes affect ultrafast heat transfer in metals after short-pulsed laser heating. Even with decades of measurements of electron-phonon relaxation, the role of thermal vs. nonthermal electron and phonon scattering on overall electron energy transfer to the phonons remains unclear. In this work, we derive an analytical expression for the electron-phonon coupling factor in a metal that includes contributions from equilibrium and nonequilibrium distributions of electrons. While the contribution from the nonthermal electrons to electron-phonon coupling is non-negligible, the increase in the electron relaxation rates with increasing laser fluence measured by thermoreflectance techniques cannot be accounted for by only considering electron-phonon relaxations. We conclude that electron-electron scattering along with electron-phonon scattering have to be considered simultaneously to correctly predict the transient nature of electron relaxation during and after short-pulsed heating of metals at elevated electron temperatures. Furthermore, for high electron temperature perturbations achieved at high absorbed laser fluences, we show good agreement between our model, which accounts for d-band excitations, and previous experimental data. Our model can be extended to other free electron metals with the knowledge of the density of states of electrons in the metals and considering electronic excitations from non-Fermi surface states.

  13. X-ray diffraction of periclase in a laser-heated diamond-anvil cell

    NASA Astrophysics Data System (ADS)

    Fiquet, G.; Andrault, D.; Itié, J. P.; Gillet, P.; Richet, P.

    1996-05-01

    Periclase (MgO) has been studied up to 16 GPa and temperatures in excess of 3000 K by X-ray diffraction in an energy-dispersive configuration at the DCI storage ring of LURE (Laboratoire pour l'Utilisation du Royonnement Electromagnétique, Orsay, France). The experiments were conducted in a diamond-anvil cell heated with a CO 2 laser with argon as a pressure transmitting medium. With this newly developed experimental set-up, the molar volume of periclase was measured as a function of pressure and temperature, which were both measured on-line. The thermal expansion coefficient (α) determined in these preliminary experiments has apparently too strong a pressure dependence, decreasing for instance from 4.9 10 -5 K -1 at room pressure to 7.5 10 -6 K -1 at 13.0 GPa. These results would yield a very high Anderson-Grüneisen parameter ( δT = 25-30), in disagreement with the expected δT = 6.5-4.3, as calculated for MgO or obtained by Fei et al. (1992a) on magnesiowüstite from room temperature to 900 K. This difference indicates that thermal pressure in the laser-heated spot can be significant and should be addressed in laser-heated diamond-anvil cell experiments.

  14. Laser Pre-Heat Studies for MagLIF with Z-Beamlet

    NASA Astrophysics Data System (ADS)

    Geissel, Matthias; Harvey-Thompson, Adam J.; Awe, T. J.; Gomez, M. R.; Harding, E.; Jennings, C.; Kimmel, M. W.; Knapp, P.; Peterson, K.; Schollmeier, M.; Sefkow, A. B.; Shores, J. E.; Sinars, D. B.; Slutz, S. A.; Smith, I. C.; Speas, C. S.; Vesey, R. A.; Porter, J. L.; Campbell, E. M.; Lewis, S. M.

    2015-11-01

    Magnetized Liner Inertial Confinement Fusion (MagLIF) relies on strong pre-heat of the fuel, typically hundreds of eV. Z-Beamlet delivers up to 4 kJ of laser energy to the target to achieve this goal. Over the last year, several experimental campaigns at the Pecos target area of Sandia's Z-Backlighter Facility and in the center section of the Z-Accelerator have been performed to investigate pre-heat. Primary objectives of these campaigns were the transmission through the laser entrance hole (LEH) in dependence of window thicknesses and focus parameters (including phase plate smoothing), as well as energy coupling to the gaseous fuel. The applied diagnostic suite included a wide range of time integrated and time-resolved X-ray imaging devices, spectrometers, backscatter monitors, a full-beam laser transmission calorimeter, and X-ray diodes.We present the findings of these studies, looking ahead towards a standard pre-heat platform. Sandia National Labs is a multi-program laboratory managed and operated by Sandia Corp., a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Dept. of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. An in situ approach to study trace element partitioning in the laser heated diamond anvil cell

    SciTech Connect

    Petitgirard, S.; Mezouar, M.; Borchert, M.; Appel, K.; Liermann, H.-P.; Andrault, D.

    2012-01-15

    Data on partitioning behavior of elements between different phases at in situ conditions are crucial for the understanding of element mobility especially for geochemical studies. Here, we present results of in situ partitioning of trace elements (Zr, Pd, and Ru) between silicate and iron melts, up to 50 GPa and 4200 K, using a modified laser heated diamond anvil cell (DAC). This new experimental set up allows simultaneous collection of x-ray fluorescence (XRF) and x-ray diffraction (XRD) data as a function of time using the high pressure beamline ID27 (ESRF, France). The technique enables the simultaneous detection of sample melting based to the appearance of diffuse scattering in the XRD pattern, characteristic of the structure factor of liquids, and measurements of elemental partitioning of the sample using XRF, before, during and after laser heating in the DAC. We were able to detect elements concentrations as low as a few ppm level (2-5 ppm) on standard solutions. In situ measurements are complimented by mapping of the chemical partitions of the trace elements after laser heating on the quenched samples to constrain the partitioning data. Our first results indicate a strong partitioning of Pd and Ru into the metallic phase, while Zr remains clearly incompatible with iron. This novel approach extends the pressure and temperature range of partitioning experiments derived from quenched samples from the large volume presses and could bring new insight to the early history of Earth.

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

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

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

  17. Propagation of a laser beam in a time-varying waveguide. [plasma heating for controlled fusion

    NASA Technical Reports Server (NTRS)

    Chapman, J. M.; Kevorkian, J.

    1978-01-01

    The propagation of an axisymmetric laser beam in a plasma column having a radially parabolic electron density distribution is reported. For the case of an axially uniform waveguide it is found that the basic characteristics of alternating focusing and defocusing beams are maintained. However, the intensity distribution is changed at the foci and outer-beam regions. The features of paraxial beam propagation are discussed with reference to axially varying waveguides. Laser plasma coupling is considered noting the case where laser heating produces a density distribution radially parabolic near the axis and the energy absorbed over the focal length of the plasma is small. It is found that: (1) beam-propagation stability is governed by the relative magnitude of the density fluctuations existing in the axial variation of the waveguides due to laser heating, and (2) for beam propagation in a time-varying waveguide, the global instability of the propagation is a function of the initial fluctuation growth rate as compared to the initial time rate of change in the radial curvature of the waveguide.

  18. Semianalytical thermal analysis of the heat capacity of YAG laser rods

    SciTech Connect

    Shi Peng; Bai Bing; Zhang Linli; Li Long; Xin Yu

    2009-12-10

    Based on the theory of semianalytical thermal analysis, we investigate the heat capacity of Nd:YAG laser rods for pumping and cooling. A general expression for the temperature field within Nd:YAG laser rod crystals is obtained for the pumping stage and the relation of the maximum temperature rise with pumping time. We also achieve an expression for the temperature field for the cooling stage and the relation of the maximum temperature rise with cooling time. These results show that, when using the output power of 300 W LD pumped Nd:YAG laser rod crystals for 5 s, the maximum temperature rise in the center of the pump face is 154.79 deg. C. After we stop the pumping for 30 s, the maximum temperature rise drops to 0.8%. These results are in agreement with those reported by others. Our results provide a theoretical basis for the optimized design of a LD end-pumped heat capacity laser.

  19. Initiation of long, free-standing Z-discharges by CO2 laser gas heating

    SciTech Connect

    Nieman, C.; Tauschwitz, A.; Penache, D.; Neff, S.; Knobloch, R.; Birkner, R.; Presura, R.; Hoffmann, D.H.H.; Yu, S.S.; Sharp, W.M.

    2004-04-19

    High current discharge channels can neutralize both current and space charge of very intense ion beams. Therefore they are considered as an interesting alternative for the final focus and beam transport in a heavy ion beam fusion reactor. At the GSI accelerator facility, 50 cm long, stable, free-standing discharge channels with currents in excess of 40 kA in 2 to 25 mbar ammonia (NH{sub 3}) gas are investigated for heavy ion beam transport studies. The discharges are initiated by a CO{sub 2} laser pulse along the channel axis before the discharge is triggered. Resonant absorption of the laser, tuned to the {nu}{sub 2} vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. This paper describes the laser-gas interaction and the discharge initiation mechanism. We report on the channel stability and evolution, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a hydrocode simulation.

  20. Geoscience Laser Altimeter System (GLAS) Loop Heat Pipes: An Eventual First Year On-Orbit

    NASA Technical Reports Server (NTRS)

    Grob, E.; Baker, C.; McCarthy, T.

    2004-01-01

    Goddard Space Flight Center's Geoscience Laser Altimeter System (GLAS) is the sole scientific instrument on the Ice, Cloud and land Elevation Satellite (ICESat) that was launched on January 12, 2003 from Vandenberg AFB. A thermal control architecture based on propylene Loop Heat Pipe technology was developed to provide selectable/stable temperature control for the lasers and other electronics over the widely varying mission environment. Following a nominal LHP and instrument start-up, the mission was interrupted with the failure of the first laser after only 36 days of operation. During the 5-month failure investigation, the two GLAS LHPs and the electronics operated nominally, using heaters as a substitute for the laser heat load. Just prior to resuming the mission, following a seasonal spacecraft yaw maneuver, one of the LHPs deprimed and created a thermal runaway condition that resulted in an emergency shutdown of the GLAS instrument. This paper presents details of the LHP anomaly, the resulting investigation and recovery, along with on-orbit flight data during these critical events.

  1. Propagation of a laser beam in a time-varying waveguide. [plasma heating for controlled fusion

    NASA Technical Reports Server (NTRS)

    Chapman, J. M.; Kevorkian, J.

    1978-01-01

    The propagation of an axisymmetric laser beam in a plasma column having a radially parabolic electron density distribution is reported. For the case of an axially uniform waveguide it is found that the basic characteristics of alternating focusing and defocusing beams are maintained. However, the intensity distribution is changed at the foci and outer-beam regions. The features of paraxial beam propagation are discussed with reference to axially varying waveguides. Laser plasma coupling is considered noting the case where laser heating produces a density distribution radially parabolic near the axis and the energy absorbed over the focal length of the plasma is small. It is found that: (1) beam-propagation stability is governed by the relative magnitude of the density fluctuations existing in the axial variation of the waveguides due to laser heating, and (2) for beam propagation in a time-varying waveguide, the global instability of the propagation is a function of the initial fluctuation growth rate as compared to the initial time rate of change in the radial curvature of the waveguide.

  2. Isochoric heating of solid gold targets with the PW-laser-driven ion beams (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Steinke, Sven; Ji, Qing; Bulanov, Stepan S.; Barnard, John; Vincenti, Henri; Schenkel, Thomas; Esarey, Eric H.; Leemans, Wim P.

    2017-05-01

    We present first results on ion acceleration with the BELLA PW laser as well as end-to-end simulation for isochoric heating of solid gold targets using PW-laser generated ion beams: (i) 2D Particle-In-Cell (PIC) simulations are applied to study the ion source characteristics of the PW laser-target interaction at the long focal length (f/65) beamline at laser intensities of ˜[5×10]^19 Wcm-2 at spot size of 0=53 μm on a CH target. (ii) In order to transport the ion beams to an EMP-free environment, an active plasma lens will be used. This was modeled [1] by calculating the Twiss parameters of the ion beam from the appropriate transport matrixes taking the source parameters obtained from the PIC simulation. (iii) Hydrodynamic simulations indicate that these ion beams can isochorically heat a 1 mm3 gold target to the Warm Dense Matter state. Reference: J. van Tilborg et al, Phys. Rev. Lett. 115, 184802 (2015). This work was supported by Laboratory Directed Research and Development (LDRD) funding from Lawrence Berkeley National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  3. Initiation of long, free-standing z discharges by CO2 laser gas heating

    NASA Astrophysics Data System (ADS)

    Niemann, C.; Tauschwitz, A.; Penache, D.; Neff, S.; Knobloch, R.; Birkner, R.; Presura, R.; Hoffmann, D. H. H.; Yu, S. S.; Sharp, W. M.

    2002-01-01

    High current discharge channels can neutralize both current and space charge of very intense ion beams. Therefore, they are considered an interesting solution for final focus and beam transport in a heavy ion beam fusion reactor. At the Gesellschaft für Schwerionenforschung accelerator facility, 50 cm long, free-standing discharge channels were created in a 60 cm diameter metallic chamber. Discharges with currents of 45 kA in 2 to 25 mbar ammonia (NH3) gas are initiated by a CO2 laser pulse along the channel axis before the capacitor bank is triggered. Resonant absorption of the laser, tuned to the v2 vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. The influence of an electric prepulse on the high current discharge was investigated. This article describes the laser-gas interaction and the discharge initiation mechanism. We found that channels are magnetohydrodynamic stable up to currents of 45 kA, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a one-dimensional Lagrangian fluid code (CYCLOPS) and is identified as the dominant initiation mechanism of the discharge.

  4. Uniform heating of materials into the warm dense matter regime with laser-driven quasimonoenergetic ion beams.

    PubMed

    Bang, W; Albright, B J; Bradley, P A; Vold, E L; Boettger, J C; Fernández, J C

    2015-12-01

    In a recent experiment at the Trident laser facility, a laser-driven beam of quasimonoenergetic aluminum ions was used to heat solid gold and diamond foils isochorically to 5.5 and 1.7 eV, respectively. Here theoretical calculations are presented that suggest the gold and diamond were heated uniformly by these laser-driven ion beams. According to calculations and SESAME equation-of-state tables, laser-driven aluminum ion beams achievable at Trident, with a finite energy spread of ΔE/E∼20%, are expected to heat the targets more uniformly than a beam of 140-MeV aluminum ions with zero energy spread. The robustness of the expected heating uniformity relative to the changes in the incident ion energy spectra is evaluated, and expected plasma temperatures of various target materials achievable with the current experimental platform are presented.

  5. Uniform heating of materials into the warm dense matter regime with laser-driven quasimonoenergetic ion beams

    NASA Astrophysics Data System (ADS)

    Bang, W.; Albright, B. J.; Bradley, P. A.; Vold, E. L.; Boettger, J. C.; Fernández, J. C.

    2015-12-01

    In a recent experiment at the Trident laser facility, a laser-driven beam of quasimonoenergetic aluminum ions was used to heat solid gold and diamond foils isochorically to 5.5 and 1.7 eV, respectively. Here theoretical calculations are presented that suggest the gold and diamond were heated uniformly by these laser-driven ion beams. According to calculations and SESAME equation-of-state tables, laser-driven aluminum ion beams achievable at Trident, with a finite energy spread of ΔE /E ˜20 %, are expected to heat the targets more uniformly than a beam of 140-MeV aluminum ions with zero energy spread. The robustness of the expected heating uniformity relative to the changes in the incident ion energy spectra is evaluated, and expected plasma temperatures of various target materials achievable with the current experimental platform are presented.

  6. Uniform heating of materials into the warm dense matter regime with laser-driven quasimonoenergetic ion beams

    SciTech Connect

    Bang, W.; Albright, B. J.; Bradley, P. A.; Vold, E. L.; Boettger, J. C.; Fernández, J. C.

    2015-12-01

    In a recent experiment at the Trident laser facility, a laser-driven beam of quasimonoenergetic aluminum ions was used to heat solid gold and diamond foils isochorically to 5.5 and 1.7 eV, respectively. Here theoretical calculations are presented that suggest the gold and diamond were heated uniformly by these laser-driven ion beams. According to calculations and SESAME equation-of-state tables, laser-driven aluminum ion beams achievable at Trident, with a finite energy spread of ΔE/E~20%, are expected to heat the targets more uniformly than a beam of 140-MeV aluminum ions with zero energy spread. As a result, the robustness of the expected heating uniformity relative to the changes in the incident ion energy spectra is evaluated, and expected plasma temperatures of various target materials achievable with the current experimental platform are presented.

  7. Air leak seal for lung dissection plane with diode laser irradiation: monitoring heat-denature with auto-fluorescence

    NASA Astrophysics Data System (ADS)

    Gotoh, Maya; Arai, Tsunenori

    2008-02-01

    We studied the monitoring of heat-denature by autofluorescence spectrum from lung dissection plane during laser air leak sealing procedure. In order to seal the air leakage from lung in thoracotomy, we proposed novel laser sealing method with the combination of the diode laser (810nm wavelength) irradiation and indocyanine green staining (peak absorption wavelength: 805 nm). This sealing method is expected to preserve the postoperative ventilatory capacity and achieve minimally invasive surgery. We previously reported that this laser sealing only requires thin sealing margin (less than 300 μm in thickness) compared with that of the suturing or stapling. The most serious issue on the laser air leak sealing might be re-air-leakage due to rigid surface layer caused by excessive heat-denature, such as carbonization. We should achieve laser air leak sealing minimizing the degree of heat denature. Dissection planes of isolated porcine lung with /without the diode laser irradiation were prepared as samples. We measured the auto-fluorescence from these samples using a spectrometer. When the diode laser was irradiated with 400J/cm2, the surface of diode laser irradiated lung was fully carbonized. The ration of auto-fluorescence emission of 450nm / 500 nm, with 280 nm excitation wavelength was decreased less tha 50 % of initial value. That of 600 nm / 500 nm was increased over 700 % of initial value. The decreasing of the 450 nm auto-fluorescence intensity might be attributed to the heat-denaturing of the interstitial collagen in lung. However, increasing of the 600 nm didn't specify the origins, we suppose it might be originated from heat-denature substance, like carbonization. We could establish the useful monitoring for lung heat-denaturing with simple methodology. We think the auto-fluorescence measurement can be helpful not only for understanding the sealing mechanism, but also for controlling the degree of heat-denaturing during the procedure.

  8. Absorption of the S-polarized short laser pulse in underdense plasma by considering the electrons ohmic heating and the laser pulse ponderomotive force effects

    NASA Astrophysics Data System (ADS)

    Panahi, Naser; Ettehadi-Abari, Mehdi; Hosseinnejad, Mohammad-Taghi

    2017-03-01

    With the advent of ultrashort high intensity laser pulses, laser absorption during laser-plasma interactions has received significant attention during the past two decades since it is related to a variety of applications of high intensity lasers, including the hot electron production for fast ignition of fusion targets, bright X-ray and gamma-ray sources, ion acceleration, compact neutron sources, and generally the creation of high energy density matters. Although some absorption mechanisms appear for short laser pulses with nanosecond duration time, they usually appear for some nonlinear phenomena as electron ohmic heating and laser pulse ponderomotive force are not considered. In this paper, the absorption of the S-polarized laser pulse through an interaction with an underdense plasma in attendance of electron ohmic heating and ponderomotive nonlinearities is analyzed. It is shown that, due to the effect of the ponderomotive force in both isothermal and non-isothermal plasmas, the increasing laser radiation angle leads to the increasing electric field wavelength. Also, since the ponderomotive force modifies the electron density and temperature distribution, it is shown that the decreasing radiation angle leads to the steepening of the electron density profile and the narrowing of electron bunching. Furthermore, by increasing the radiation angle, the absorption coefficient is decreased strongly. It is found that due to the heat of the plasma at the expanse of the wave energy in the case of a non-thermal plasma, the absorption coefficient is increased intensively in comparison to a collisional plasma.

  9. Melting temperature of water at high pressure measured in a laser-heated diamond anvil cell with CO2 laser

    NASA Astrophysics Data System (ADS)

    Kimura, T.; Kuwayama, Y.

    2012-12-01

    The phase relations and physical properties of water at high pressures and temperatures are important physical, geophysical, and planetary problems. For example, recent molecular dynamics calculations suggest that water is superionic at high densities relevant to planets such as Uranus and Neptune [1, 2], and this predicted property plays a key role in dynamo models to explain the unusual non-dipolar magnetic field structure of these planets [3, 4]. The advances in combining techniques such as synchrotron x-ray diffraction or in situ optical Raman spectroscopy with diamond anvil cell (DAC) technologies allow us to measure the melting temperature of water to within a few percent for pressures up to 20 GPa [5-8]. However, at pressures above 20 GPa, recently reported values of melting temperature exhibit significant differences with each other [7-10]. This discrepancy should be caused by a chemical reaction occurred between the metal absorber contained in the DAC and the dissociated water. By using CO2 laser for sample heating, the metal is not necessary because water has significant absorption in the wavelength range of CO2 laser (10.6 μm). We report the melting temperature of water in a diamond anvil cell more than 20 GPa using CO2 laser heating system. References [1] M. French et al., Phys. Rev. B 79, 054107 (2009). [2] M. French et al., Phys. Rev. B 82, 174108 (2010). [3] S. Stanley and J. Bloxham, Nature 428, 151 (2004). [4] R. Redmer et al., Icarus 211, 798 (2011). [5] F. Datch et al., Phys. Rev. B 61, 6335 (2000). [6] JF. Lin et al., J. Chem. Phys 121, 8423 (2004). [7] JF. Lin et al., Geophys. Res. Lett. 32, L11306 (2005). [8] AF. Goncharov et al., Phys. Rev. Lett. 94, 125504 (2005). [9] B. Schwager et al., J. Phys. Condens. Matter 16, 51177 (2004). [10] AF. Goncharov et al., J. Chem. Phys. 130, 124514 (2009).

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  11. Limits of applicability of a two-temperature model under nonuniform heating of metal by an ultrashort laser pulse

    SciTech Connect

    Polyakov, D S; Yakovlev, E B

    2015-10-31

    The heating of metals (silver and aluminium) by ultrashort laser pulses is analysed proceeding from a spatially nonuniform kinetic equation for the electron distribution function. The electron subsystem thermalisation is estimated in a wide range of absorbed pulse energy density. The limits of applicability are determined for the two-temperature model. (interaction of laser radiation with matter)

  12. Heat generation caused by ablation of dental hard tissues with an ultrashort pulse laser (USPL) system.

    PubMed

    Braun, Andreas; Krillke, Raphael Franz; Frentzen, Matthias; Bourauel, Christoph; Stark, Helmut; Schelle, Florian

    2015-02-01

    Heat generation during the removal of dental hard tissues may lead to a temperature increase and cause painful sensations or damage dental tissues. The aim of this study was to assess heat generation in dental hard tissues following laser ablation using an ultrashort pulse laser (USPL) system. A total of 85 specimens of dental hard tissues were used, comprising 45 specimens of human dentine evaluating a thickness of 1, 2, and 3 mm (15 samples each) and 40 specimens of human enamel with a thickness of 1 and 2 mm (20 samples each). Ablation was performed with an Nd:YVO4 laser at 1,064 nm, a pulse duration of 9 ps, and a repetition rate of 500 kHz with an average output power of 6 W. Specimens were irradiated for 0.8 s. Employing a scanner system, rectangular cavities of 1-mm edge length were generated. A temperature sensor was placed at the back of the specimens, recording the temperature during the ablation process. All measurements were made employing a heat-conductive paste without any additional cooling or spray. Heat generation during laser ablation depended on the dental hard tissue (enamel or dentine) and the thickness of the respective tissue (p < 0.05). Highest temperature increase could be observed in the 1-mm thickness group for enamel. Evaluating the 1-mm group for dentine, a significantly lower temperature increase could be measured (p < 0.05) with lowest values in the 3-mm group (p < 0.05). A time delay for temperature increase during the ablation process depending on the material thickness was observed for both hard tissues (p < 0.05). Employing the USPL system to remove dental hard tissues, heat generation has to be considered. Especially during laser ablation next to pulpal tissues, painful sensations and potential thermal injury of pulp tissue might occur.

  13. A study of the flow boiling heat transfer in a minichannel for a heated wall with surface texture produced by vibration-assisted laser machining

    NASA Astrophysics Data System (ADS)

    Piasecka, Magdalena; Strąk, Kinga; Maciejewska, Beata; Grabas, Bogusław

    2016-09-01

    The paper presents results concerning flow boiling heat transfer in a vertical minichannel with a depth of 1.7 mm and a width of 16 mm. The element responsible for heating FC-72, which flowed laminarly in the minichannel, was a plate with an enhanced surface. Two types of surface textures were considered. Both were produced by vibration-assisted laser machining. Infrared thermography was used to record changes in the temperature on the outer smooth side of the plate. Two-phase flow patterns were observed through a glass pane. The main aim of the study was to analyze how the two types of surface textures affect the heat transfer coefficient. A two-dimensional heat transfer approach was proposed to determine the local values of the heat transfer coefficient. The inverse problem for the heated wall was solved using a semi-analytical method based on the Trefftz functions. The results are presented as relationships between the heat transfer coefficient and the distance along the minichannel length and as boiling curves. The experimental data obtained for the two types of enhanced heated surfaces was compared with the results recorded for the smooth heated surface. The highest local values of the heat transfer coefficient were reported in the saturated boiling region for the plate with the type 1 texture produced by vibration-assisted laser machining.

  14. Investigating the laser heating of underdense plasmas at conditions relevant to MagLIF

    NASA Astrophysics Data System (ADS)

    Harvey-Thompson, Adam

    2015-11-01

    The magnetized Liner Inertial Fusion (MagLIF) scheme has achieved thermonuclear fusion yields on Sandia's Z Facility by imploding a cylindrical liner filled with D2 fuel that is preheated with a multi-kJ laser and pre-magnetized with an axial field Bz = 10 T. The challenge of fuel preheating in MagLIF is to deposit several kJ's of energy into an underdense (ne/ncrit<0.1) fusion fuel over ~ 10 mm target length efficiently and without introducing contaminants that could contribute to unacceptable radiative losses during the implosion. Very little experimental work has previously been done to investigate laser heating of gas at densities, scale lengths, modest intensities (Iλ2 ~ 1014 watts- μm2 /cm2) and magnetization parameters (ωceτe ~ 10) necessary for MagLIF. In particular, magnetization of the preheated plasma suppresses electron thermal conduction, which can modify laser energy coupling. Providing an experimental dataset in this regime is essential to not only understand the dynamics of a MagLIF implosion and stagnation, but also to validate magnetized transport models and better understand the physics of laser propagation in magnetized plasmas. In this talk, we present data and analysis of several experiments conducted at OMEGA-EP and at Z to investigate laser propagation and plasma heating in underdense D2 plasmas under a range of conditions, including densities (ne = 0.05-0.1 nc) and magnetization parmaters (ωceτe ~ 0-10). The results show differences in the electron temperature of the heated plasma and the velocity of the laser burn wave with and without an applied magnetic field. We will show comparisons of these experimental results to 2D and 3D HYDRA simulations, which show that the effect of the magnetic field on the electron thermal conduction needs to be taken into account when modeling laser preheat. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the National Nuclear Security Administration

  15. Improved heat sinking for laser-diode arrays using microchannels in CVD diamond

    SciTech Connect

    Goodson, K.E.; Kurabayashi, K.; Pease, R.F.W.

    1995-12-31

    This work proposes a novel cooling system for high-power laser-diode arrays, for which the maximum optical output power density per unit surface area is limited by the temperature rise due to self heating. The proposed system uses a microchannel heat sink made of chemical-vapor-deposited (CVD) diamond, whose high thermal conductivity increases the efficiency of the channel wall-fins and reduces the array-to-coolant thermal resistance. The thermal resistance is further reduced in the proposed system by minimizing the separation between active regions and the diamond using epitaxial lift-off (ELO) and grafting technology. This work predicts the array-to-coolant thermal resistance using a simple model for the combined conduction and convection problem. The resistance is calculated to be 75% less than that for a conventional configuration using a silicon microchannel heat sink. The present analysis strongly motivates a future experimental study.

  16. Laser Heating of Solid Matter by Light-Pressure-Driven Shocks at Ultrarelativistic Intensities

    SciTech Connect

    Akli, K.U.; Hansen, S.B.; Kemp, A.J.; Freeman, R.R.; Beg, F.N.; Clark, D.C.; Chen, S.D.; Hey, D.; Hatchett, S.P.; Highbarger, K.; Giraldez, E.; Green, J.S.; Gregori, G.; Lancaster, K.L.; Ma, T.; MacKinnon, A.J.; Norreys, P.; Patel, N.; Pasley, J.; Shearer, C.; Stephens, R.B.; Stoeckl, C.; Storm, M.; Theobald, W.; Van Woerkom, L.D.; Weber, R.; Key, M.H.

    2008-04-29

    The heating of solid targets irradiated by 5 x 10^20 W cm^-2, 0.8 ps, 1.05 um wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo, and V. A surface layer is heated to ~5 keV with an axial temperature gradient of 0.6 um scale length. Images of Ni Ly sub-alpha show the hot region has <25 um diameter. These data are consistent with collisional particle-in-cell simulations using preformed plasma density profiles from hydrodynamic modeling which show that the >100 Gbar light pressure compresses the preformed plasma and dries a shock into the solid, heating a thin layer.

  17. Laser heating of solid matter by light pressure-driven shocks

    SciTech Connect

    Akli, K; Hansen, S B; Kemp, A J; Freeman, R R; Beg, F N; Clark, D; Chen, S; Hey, D; Highbarger, K; Giraldez, E; Green, J; Gregori, G; Lancaster, K; Ma, T; MacKinnon, A J; Norreys, P A; Patel, N; Patel, P; Shearer, C; Stephens, R B; Stoeckl, C; Storm, M; Theobald, W; Van Woerkom, L; Weber, R; Key, M H

    2007-05-04

    Heating by irradiation of a solid surface in vacuum with 5 x 10{sup 20} W cm{sup -2}, 0.8 ps, 1.05 {micro}m wavelength laser light is studied by x-ray spectroscopy of the K-shell emission from thin layers of Ni, Mo and V. A surface layer is heated to {approx} 5 keV with an axial temperature gradient of 0.6 {micro}m scale length. Images of Ni Ly{sub {alpha}} show the hot region has a {approx} 25 {micro}m diameter, much smaller than {approx} 70 {micro}m region of K{sub {alpha}} emission. 2D particle-in-cell (PIC) simulations suggest that the surface heating is due to a light pressure driven shock.

  18. Residual Stress Measurements with Laser Speckle Correlation Interferometry and Local Heat Treating

    SciTech Connect

    Pechersky, M.J.; Miller, R.F.; Vikram, C.S.

    1994-01-06

    A new experimental technique has been devised to measure residual stresses in ductile materials with a combination of laser speckle pattern interferometry and spot heating. The speckle pattern interferometer measures in-plane deformations while the heating provides for very localized stress relief. The residual stresses are determined by the amount of strain that is measured subsequent to the heating and cool-down of the region being interrogated. A simple lumped parameter model is presented to provide a description of the method. This description is followed by presentations of the results of finite element analyses and experimental results with uniaxial test specimens. Excellent agreement between the experiments and the computer analyses were obtained.

  19. An investigation into the output characteristics of a discharge-heated copper vapor laser

    NASA Astrophysics Data System (ADS)

    Wang, Tieh C.; Yang, Ching Y.

    1989-11-01

    The laser output characteristics of a discharge-heated copper vapor laser (CVL) were investigated at a charging voltage of 14.5 kV, laser tube temperature of 1450 C, pulse repetition rate (PRR) range from 0.5 to 9.5 kHz, and buffer gas pressures of 20 and 75 Torr. Changing buffer gas pressure from 20 to 75 Torr causes no significant variation of the rates of relaxation of metastable atoms. Increase of the current rise of pumping pulse with increasing PRR is the predominant factor for improving the laser behavior when PRR is greater than 3.5 kHz with buffer gas pressure of 20 Torr and when PRR is less than 4.5 kHz with buffer gas pressure of 75 Torr. For short pulse applications, the CVL is preferably operated at high PRR and low buffer gas regime. For the 25-W CVL used here, the prepulse electron density should be higher than 10 to the 13th/cu cm for efficient laser operation. The output power of this CVL can be increased to much higher than 30 W if the thermal insulation is optimized and the PRR is increased.

  20. Femtosecond filament initiated, microwave heated cavity-free nitrogen laser in air

    NASA Astrophysics Data System (ADS)

    Kartashov, Daniil; Shneider, Mikhail N.

    2017-03-01

    We present the results of numerical modeling of the igniter-heater concept for initiation of standoff, cavity free lasing action in the atmosphere when a femtosecond laser filament is used for plasma generation (igniter) and a microwave heater provides electron-collision pumping of electronic states in molecular nitrogen. By solving numerically the kinetic equation for the energy distribution function of electrons, generated in a femtosecond laser filament and heated by a microwave beam, we identify the conditions enabling single-pass, standoff UV-laser from molecular nitrogen in the atmosphere. The plasma density, the minimum amplitude of the microwave field, and the small-signal gain, necessary to achieve the lasing, are determined. We demonstrate that lasing build up time can be minimized and efficiency improved by using elliptically polarized laser pulses for filamentation. It is shown that realization of the filament-igniter, microwave-heater concept of the sky laser at low altitudes would require a microwave source of hundreds of kilowatt-megawatt power. The required microwave power can be reduced by several orders of magnitude when the igniter-heater scheme is used at the 10-30 km range of altitudes.

  1. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Transient deformation of the surface of a thermocapillary liquid by laser heating

    NASA Astrophysics Data System (ADS)

    Rozniakowski, K.

    1995-02-01

    Deformation self-focusing of a laser beam (0.6328 μm, 5 mW) on the surface of a strongly absorbing viscous liquid was studied experimentally. It was found that the approach described can be used to evaluate the surface tension.

  2. Effect of soft-core potentials on inverse bremsstrahlung heating during laser matter interactions

    NASA Astrophysics Data System (ADS)

    Pandit, Rishi R.; Sentoku, Yasuhiko; Becker, Valerie R.; Barrington, Kasey; Thurston, Jeremy; Cheatham, Jonathan; Ramunno, Lora; Ackad, Edward

    2017-07-01

    Inverse bremsstrahlung heating (IBH) is studied by using scattering theory for the interaction of intense lasers with matter using soft-core potentials. This involves three different kinds of interactions: (i) the interaction of the electrons with the external laser field, (ii) the electron-ion interaction, and (iii) the electron-electron interaction. In the interaction of rare-gas clusters with ultrashort laser pulses, nano-plasmas with high densities are created. A new scaling for the differential cross-section and the rate of energy absorption via IBH is derived which depends on the external laser field as well as electric field due to the other particles. When the particles are treated as charge distributions, the electric fields due to the other particles depend on a parameter of the non-Coulombic soft-core field, the potential depth, often used to avoid the Coulomb singularity. Thus, the rate of IBH also depends on the potential depth. Calculations are performed for electrons in a range of wavelength regimes from the vacuum ultraviolet to the mid-infrared. The rate of energy absorption via IBH is found to increase rapidly with increases in the potential depth and then quickly becomes mostly saturated at the Coulomb value for greater depths. The rate of energy absorption via IBH is found to be non-linear with laser intensities. The differential cross-section as well as the rate of energy absorption of IBH is found to increase with increases in laser wavelength. Finally, lower laser intensities saturate more slowly, requiring a larger potential depth to saturate.

  3. Laser Non-Uniform Heating of Moving Thin Wires Below the Biot Number Criterion of Uniform Temperature

    NASA Astrophysics Data System (ADS)

    Wickramasooriya, Thiwanka; Vaidyanathan, Raj; Kar, Aravinda

    2016-06-01

    An analytic solution is obtained for three-dimensional quasi-steady state temperature distribution during laser heating of moving thin wires. The wire moves at a constant speed through a vacuum chamber, which is back-filled with an inert gas such as argon, and a laser beam of rectangular cross-section is incident on the wire. The ambient gas provides a convection heat transfer mechanism, which yields a Biot number, Bi, for the heating process to determine whether the temperature distribution would be uniform or nonuniform in the cross-section of the wire. Generally, the criterion of Bi less than 0.1 is applied to assume spatially uniform temperature distribution in a solid. The temperature distribution is determined for different Bi numbers and the variation of the temperature in the azimuthal direction is analyzed. The method of solution involves the Fourier transform in the azimuthal direction and the Hankel transform in the radial direction for a three-dimensional quasi-steady state heat conduction equation containing an advection term that accounts for the motion of the wire. The thermal and optical properties of the material is assumed to be constant in the temperature range of this study. The heat loss due to radiation heat transfer between the wire surface and the surrounding environment is neglected due to the small laser-heated surface area. Using this model, the temperature profile is studied for different process parameters such as the incident laser power, laser beam profile, Biot number, and wire speed.

  4. Laser speckle strain and deformation sensor using linear array image cross-correlation method for specifically arranged triple-beam triple-camera configuration

    NASA Technical Reports Server (NTRS)

    Sarrafzadeh-Khoee, Adel K. (Inventor)

    2000-01-01

    The invention provides a method of triple-beam and triple-sensor in a laser speckle strain/deformation measurement system. The triple-beam/triple-camera configuration combined with sequential timing of laser beam shutters is capable of providing indications of surface strain and structure deformations. The strain and deformation quantities, the four variables of surface strain, in-plane displacement, out-of-plane displacement and tilt, are determined in closed form solutions.

  5. Laser-heating-induced displacement of surfactants on the water surface.

    PubMed

    Backus, Ellen H G; Bonn, Daniel; Cantin, Sophie; Roke, Sylvie; Bonn, Mischa

    2012-03-08

    We report a combined vibrational sum-frequency generation (SFG) spectroscopy, Brewster angle microscopy (BAM), and ellipsometry study of different surfactants on water as a function of surfactant density. Vibrational SFG spectra of surfactants on the water surface in a Langmuir trough have been measured in both the surfactant CH and the water OH stretch regions. At low densities, the SFG signal generated at the surface in the presence of the surfactant is indistinguishable from the SFG signal generated at the clean water-air interface. When the surfactant density increases, i.e., upon compressing the monolayer, a very sudden increase in the SFG signal in both the CH and OH spectral regions is observed. For higher laser fluences, this stepwise increase occurs at increasingly higher surfactant densities. Since BAM shows that surfactant molecules are clearly present at these low densities, we conclude that at low surfactant density the laser beam displaces relatively high-density domains with surfactants in the liquid expanded phase out of the region of the laser focus. This is a consequence of the thermal gradient induced by local heating of the water phase with the monolayer on top due to repetitive laser excitation at 1 kHz. It can be circumvented by using a rotating trough. In this manner, the sampled surface area can be refreshed, allowing artifact-free vibrational SFG spectra to be measured down to the very lowest surfactant densities. In ellipsometry experiments, a similar step can be noticed, which, however, is of a different nature; i.e., it is not related to heating (the laser fluence is very low and the light nonresonant) but to a molecular transition. The occurrence of the step in ellipsometry as a function of area per molecule depends critically on the preparation of the monolayer. By giving the molecules time and space to relax during the preparation of the monolayer, this step could also be eliminated.

  6. Laser Beam Failure Mode Effects and Analysis (FMEA) of the Solid State Heat Capacity Laser (SSHCL)

    SciTech Connect

    King, J.

    2015-09-07

    A laser beam related FMEA of the SSHCL was performed to determine potential personnel and equipment safety issues. As part of the FMEA, a request was made to test a sample of the drywall material used for walls in the room for burn-through. This material was tested with a full power beam for five seconds. The surface paper material burned off and the inner calcium carbonate turned from white to brown. The result of the test is shown in the photo below.

  7. Measurement of the equation of state of solid-density copper heated with laser-accelerated protons

    NASA Astrophysics Data System (ADS)

    Feldman, S.; Dyer, G.; Kuk, D.; Ditmire, T.

    2017-03-01

    We present equation of state (EOS) measurements of solid-density copper heated to 5-10 eV. A copper sample was heated isochorically by hydrogen ions accelerated from an adjacent foil by a high intensity pulsed laser, and probed optically. The measured temperature and expansion are compared against simulations using the most up-to-date wide range EOS tables available.

  8. Non-Maxwellian effects in underdense plasmas heated by non-uniform laser beams

    NASA Astrophysics Data System (ADS)

    Matte, Jean-Pierre

    2005-10-01

    The collisionl heating of plasmas by intense laser beams is known to drive the electron distribution function into a super-Gaussian [1] or ``DLM'' [2] shape. This reduces the absorption [1], and the reduction is stronger if the beam is very non-uniform, for a given average intensity, as there is a depletion of slow electrons, compared to a Maxwellian of the same density and average energy. If the beam irradiates most or a good fraction of the plasma volume, these non-Maxwellian effects also imply a depletion of high energy electrons, with the resulting strong reduction of Landau damping of Langmuir waves [2], contrary to the results of Brunner and Valeo [3] which were obtained in the limit of a narrow beam heating a wide plasma. The depletion of fast electrons depends essentially on the average laser intensity. We will show how these two aspects vary with the laser and plasma parameters.[1] A.B. Langdon, Phys. Rev. Lett. 44, 575 (1980) [2] B.B. Afeyan, A.E. Chou, J.P. Matte et al., Phys. Rev. Lett. 80, 2322 (1998). [3] S. Brunner and E. Valeo, Phys. Plasmas 9, 923 (2002).

  9. High Heat Flux Interactions and Tritium Removal from Plasma Facing Components by a Scanning Laser

    SciTech Connect

    C.H. Skinner; C.A. Gentile; A. Hassanein

    2002-01-28

    A new technique for studying high heat flux interactions with plasma facing components is presented. The beam from a continuous wave 300 W neodymium laser was focused to 80 W/mm2 and scanned at high speed over the surface of carbon tiles. These tiles were previously used in the TFTR [Tokamak Fusion Test Reactor] inner limiter and have a surface layer of amorphous hydrogenated carbon that was codeposited during plasma operations. Laser scanning released up to 84% of the codeposited tritium. The temperature rise of the codeposit on the tiles was significantly higher than that of the manufactured material. In one experiment, the codeposit surface temperature rose to 1,770 C while for the same conditions, the manufactured surface increased to only 1,080 C. The peak temperature did not follow the usual square-root dependence on heat pulse duration. Durations of order 100 ms resulted in brittle destruction and material loss from the surface, while a duration of approximately 10 ms showed minimal change. A digital microscope imaged the codeposit before, during, and after the interaction with the laser and revealed hot spots on a 100-micron scale. These results will be compared to analytic modeling and are relevant to the response of plasma facing components to disruptions and vertical displacement events (VDEs) in next-step magnetic fusion devices.

  10. X-ray diffraction in the pulsed laser heated diamond anvil cell

    NASA Astrophysics Data System (ADS)

    Goncharov, Alexander F.; Prakapenka, Vitali B.; Struzhkin, Viktor V.; Kantor, Innokenty; Rivers, Mark L.; Dalton, D. Allen

    2010-11-01

    We have developed in situ x-ray synchrotron diffraction measurements of samples heated by a pulsed laser in the diamond anvil cell at pressure up to 60 GPa. We used an electronically modulated 2-10 kHz repetition rate, 1064-1075 nm fiber laser with 1-100 μs pulse width synchronized with a gated x-ray detector (Pilatus) and time-resolved radiometric temperature measurements. This enables the time domain measurements as a function of temperature in a microsecond time scale (averaged over many events, typically more than 10 000). X-ray diffraction data, temperature measurements, and finite element calculations with realistic geometric and thermochemical parameters show that in the present experimental configuration, samples 4 μm thick can be continuously temperature monitored (up to 3000 K in our experiments) with the same level of axial and radial temperature uniformities as with continuous heating. We find that this novel technique offers a new and convenient way of fine tuning the maximum sample temperature by changing the pulse width of the laser. This delicate control, which may also prevent chemical reactivity and diffusion, enables accurate measurement of melting curves, phase changes, and thermal equations of state.

  11. New techniques for high-temperature melting measurements in volatile refractory materials via laser surface heating.

    PubMed

    Manara, D; Sheindlin, M; Heinz, W; Ronchi, C

    2008-11-01

    An original technique for the measurement of high-temperature phase transitions was implemented based on a laser-heating method, enabling chemically unstable, refractory materials to be melted under controlled conditions. This technique includes two independent but correlated methods: In the first, fast multichannel pyrometry is employed to measure thermograms and spectral emissivity; in the second, a low-power probe laser beam is used for the detection of reflectivity changes induced by phase transitions on the sample surface. The experiments are carried out under medium ( approximately 10(2) kPa) or high ( approximately 10(2) MPa) inert-gas pressures in order to kinetically suppress evaporation in volatile or chemically instable samples. Two models for the simulation of the laser-heating pulses are as well introduced. Some results are presented about the successful application of this technique to the study of the melting behavior of oxides such as UO(2+x), ZrO(2), and their mixed oxides. The method can be extended to a broad class of refractory materials.

  12. Picosecond x-ray laser photoelectron spectroscopy of room temperature and heated materials

    SciTech Connect

    Dunn, J; Nelson, A J; van Buuren, T; Hunter, J R

    2004-08-03

    An 84.5 eV Ni-like Pd ion 4d - 4p x-ray laser source generated by the LLNL Compact Multipulse Terawatt (COMET) tabletop system has been used to probe the electronic structure of various metals and semiconductors. In addition to the {approx}4 - 5 ps time resolution, the probe provides the necessary high photon flux (>10{sup 12}/pulse), narrow line width ({Delta}E/E{approx}2 x 10{sup -5}) and coherence for studying valence band and shallow core electronic structure levels in a single shot. We show some preliminary results of room temperature and heated thin foil samples consisting of 50 nm Cu coated on a 20 nm C substrate. A 527 nm wavelength 400 fs laser pulse containing 0.1 - 2.5 mJ laser energy is focused in a large 500 x 700 {micro}m{sup 2} (FWHM) spot to create heated conditions of 0.07 - 1.8 x 1012 W cm{sup -2} intensity.

  13. 3D model for laser heating of a heterogeneous turbid medium

    NASA Astrophysics Data System (ADS)

    Rossacci, Michael J.; DiMarzio, Charles A.; Lindberg, Scott C.; Pankratov, Michail M.

    1997-05-01

    In order to better understand the interaction of laser light with biological tissue, a light-transport model is integrated with a heat-transport model. The outputs include temperature as a function of position and time, given the illumination conditions and the optical and thermal properties of the tissue. The optical portion of the algorithm is based on the theory of radiative transfer through a turbid medium. Our computer program models multiple scattering in three dimensions using seven discrete irradiances which approximate the radiative transport equation. The distribution of absorbed light in the tissue is calculated and used as the source term in a discrete approximation to the thermal diffusion equation. Recently, we have been using the model to better understand the laser-heating of heterogeneous tissue. Rather than modeling a homogeneous mixture having properties given by weighted averages of those of tissue and blood, we model this medium as an array of blood vessels in a bloodless dermis background. We are currently analyzing temporal and spatial variations of temperature in homogeneous and heterogeneous tissue having identical blood concentrations. A particular application of the model is to the study of laser coagulation tonsillectomy.

  14. Isochoric heating of solid gold targets with the PW-laser-driven ion beams

    NASA Astrophysics Data System (ADS)

    Steinke, Sven; Ji, Qing; Bulanov, Stepan; Barnard, John; Schenkel, Thomas; Esarey, Eric; Leemans, Wim

    2016-10-01

    We present an end-to-end simulation for isochoric heating of solid gold targets using ion beams produced with the BELLA PW laser at LBNL: (i) 2D Particle-In-Cell (PIC) simulations are applied to study the ion source characteristics of the PW laser-target interaction at the long focal length (f/#65) beamline at laser intensities of 5x1019W/cm2 at spot size of ω0 = 52 μm on a CH target. (ii) In order to transport the ion beams to an EMP-free environment, an active plasma lens will be used. This was modeled by calculating the Twiss parameters of the ion beam from the appropriate transport matrixes using the source parameters obtained from the PIC simulation. Space charge effects were considered as well. (iii) Hydrodynamic simulations indicate that these ion beams can isochorically heat a 1 mm3 gold target to the Warm Dense Matter state. This work was supported by Fusion Energy Science, and LDRD funding from Lawrence Berkeley National Laboratory, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

  15. X-ray diffraction in the pulsed laser heated diamond anvil cell

    SciTech Connect

    Goncharov, Alexander F.; Prakapenka, Vitali B.; Struzhkin, Viktor V.; Kantor, Innokenty; Rivers, Mark L.; Dalton, D. Allen

    2010-11-19

    We have developed in situ x-ray synchrotron diffraction measurements of samples heated by a pulsed laser in the diamond anvil cell at pressure up to 60 GPa. We used an electronically modulated 2-10 kHz repetition rate, 1064-1075 nm fiber laser with 1-100 {micro}s pulse width synchronized with a gated x-ray detector (Pilatus) and time-resolved radiometric temperature measurements. This enables the time domain measurements as a function of temperature in a microsecond time scale (averaged over many events, typically more than 10,000). X-ray diffraction data, temperature measurements, and finite element calculations with realistic geometric and thermochemical parameters show that in the present experimental configuration, samples 4 {micro}m thick can be continuously temperature monitored (up to 3000 K in our experiments) with the same level of axial and radial temperature uniformities as with continuous heating. We find that this novel technique offers a new and convenient way of fine tuning the maximum sample temperature by changing the pulse width of the laser. This delicate control, which may also prevent chemical reactivity and diffusion, enables accurate measurement of melting curves, phase changes, and thermal equations of state.

  16. X-ray diffraction in the pulsed laser heated diamond anvil cell

    SciTech Connect

    Goncharov, Alexander F.; Struzhkin, Viktor V.; Dalton, D. Allen; Prakapenka, Vitali B.; Kantor, Innokenty; Rivers, Mark L.

    2010-11-15

    We have developed in situ x-ray synchrotron diffraction measurements of samples heated by a pulsed laser in the diamond anvil cell at pressure up to 60 GPa. We used an electronically modulated 2-10 kHz repetition rate, 1064-1075 nm fiber laser with 1-100 {mu}s pulse width synchronized with a gated x-ray detector (Pilatus) and time-resolved radiometric temperature measurements. This enables the time domain measurements as a function of temperature in a microsecond time scale (averaged over many events, typically more than 10 000). X-ray diffraction data, temperature measurements, and finite element calculations with realistic geometric and thermochemical parameters show that in the present experimental configuration, samples 4 {mu}m thick can be continuously temperature monitored (up to 3000 K in our experiments) with the same level of axial and radial temperature uniformities as with continuous heating. We find that this novel technique offers a new and convenient way of fine tuning the maximum sample temperature by changing the pulse width of the laser. This delicate control, which may also prevent chemical reactivity and diffusion, enables accurate measurement of melting curves, phase changes, and thermal equations of state.

  17. X-ray diffraction in the pulsed laser heated diamond anvil cell

    SciTech Connect

    Goncharov, Alexander F.; Prakapenka, Vitali B.; Struzhkin, Viktor V.; Kantor, Innokenty; Rivers, Mark L.; Dalton, D. Allen

    2010-11-03

    We have developed in situ x-ray synchrotron diffraction measurements of samples heated by a pulsed laser in the diamond anvil cell at pressure up to 60 GPa. We used an electronically modulated 2–10 kHz repetition rate, 1064–1075 nm fiber laser with 1–100 μs pulse width synchronized with a gated x-ray detector (Pilatus) and time-resolved radiometric temperature measurements. This enables the time domain measurements as a function of temperature in a microsecond time scale (averaged over many events, typically more than 10,000). X-ray diffraction data, temperature measurements, and finite element calculations with realistic geometric and thermochemical parameters show that in the present experimental configuration, samples 4 μm thick can be continuously temperature monitored (up to 3000 K in our experiments) with the same level of axial and radial temperature uniformities as with continuous heating. We find that this novel technique offers a new and convenient way of fine tuning the maximum sample temperature by changing the pulse width of the laser. This delicate control, which may also prevent chemical reactivity and diffusion, enables accurate measurement of melting curves, phase changes, and thermal equations of state.

  18. Computing specific intensity distributions for laser material processing by solving an inverse heat conduction problem

    NASA Astrophysics Data System (ADS)

    Völl, Annika; Stollenwerk, Jochen; Loosen, Peter

    2016-03-01

    Laser beam intensity distribution profiles for material processing techniques are most of the time restricted to be either of Gaussian or tophat shape. This often leads to different kind of problems especially at the edges of the laser-heated tracks, examples are energy losses or unnecessary overlaps. Thus, machining quality and process efficiency could be much improved by using application specific intensity profiles to generate optimal temperature distributions in the processed material. In this work, we present a numerical method to derive a specific intensity profile for a given temperature distribution. As this problem belongs to the set of inverse heat conduction problems, which are ill-posed, special regularization algorithms are needed. The only method to solve this inverse problem in reasonable time is the conjugate gradient method which we extend to the given problem of laser material processing applications. This method is an iterative approach where in each step the actual temperature distribution is calculated by using the finite element method. In general, the proposed method is applicable for materials with constant or temperature dependent coefficients, for static and dynamic distributions as well as for plane or complex geometries. However, restricting ourselves to plane geometries, intensity distributions that create tophat- or stepped temperature distributions on the plane surface of the processed material are derived and will be presented. In future work, we intend to verify these results using freeform optics as well as singly addressable V(E)CSEL arrays.

  19. Changes in dental enamel oven heated or irradiated with Er,Cr:YSGG laser. Analysis by FTIR

    NASA Astrophysics Data System (ADS)

    Rabelo, J. S.; Ana, P. A.; Benetti, C.; Valério, M. E. G.; Zezell, D. M.

    2010-04-01

    This study evaluated the change that occurs in dental enamel under action of oven heating or Er,Cr:YSGG laser irradiation aiming to obtain a structure more resistant to demineralization. Enamel powder was obtained from bovine teeth. Samples were subjected to oven heating at temperatures of 200, 400, 600, 800, and 1000°C or during laser irradiation with energy densities of 7.53, 10.95, and 13.74 J/cm2. The infrared thermography was used to measure the surface temperature generated in the solid samples of enamel during lasers irradiation. The samples were analyzed by Fourier transform infrared spectroscopy (FTIR), which shows changes on enamel oven heated or laser irradiated, due to treatments, related to carbonates, adsorbed water and hydroxyl content. These compositional effects were more evident in lased samples. These changes may alter the material properties such as its solubility, and decrese of demineralization that is important for caries prevention.

  20. Characterization of the respiration of 3T3 cells by laser-induced fluorescence during a cyclic heating process

    NASA Astrophysics Data System (ADS)

    Beuthan, J.; Dressler, C.; Zabarylo, U.; Minet, O.

    2010-04-01

    The use of lasers in the near infrared spectral range for laser-induced tumor therapy (LITT) demands a new understanding of the thermal responses to repetitive heat stress. The analysis of laser-induced fluorescence during vital monitoring offers an excellent opportunity to solve many of the related issues in this field. The laser-induced fluorescence of the cellular coenzyme NADH was investigated for its time and intensity behavior under heat stress conditions. Heat was applied to vital 3T3 cells (from 22°C to 50°C) according to a typical therapeutical time regime. A sharp increase in temperature resulted in non-linear time behavior when the concentration of this vital coenzyme changed. There are indications that biological systems have a delayed reaction on a cellular level. These results are therefore important for further dosimetric investigations.

  1. Heat-fraction-limited CW Yb:YAG cryogenic solid-state laser with 100% photon slope efficiency.

    PubMed

    Brown, David C; Bruno, Thomas M; Singley, Joseph M

    2010-08-02

    We report the demonstration of a heat-fraction-limited CW Yb:YAG laser operating near 77 K with output at 1029 nm, pumped with a diffraction-limited room-temperature CW Nd:YAG laser operating at 946 nm. With a 50% reflectivity outcoupler, the average threshold absorbed pump power was 18.8 mW and the average slope efficiency 91.9%, close to the heat-fraction limited value of 91.5%. Average optical to optical and photon slope efficiencies are 84% and 100% respectively. To the best of our knowledge this solid-state laser is the first to operate at the heat-fraction-limit and demonstrates record slope, photon slope and optical-optical efficiencies for optically-pumped solid-state lasers.

  2. Uniform heating of materials into the warm dense matter regime with laser-driven quasimonoenergetic ion beams

    DOE PAGES

    Bang, W.; Albright, B. J.; Bradley, P. A.; ...

    2015-12-01

    In a recent experiment at the Trident laser facility, a laser-driven beam of quasimonoenergetic aluminum ions was used to heat solid gold and diamond foils isochorically to 5.5 and 1.7 eV, respectively. Here theoretical calculations are presented that suggest the gold and diamond were heated uniformly by these laser-driven ion beams. According to calculations and SESAME equation-of-state tables, laser-driven aluminum ion beams achievable at Trident, with a finite energy spread of ΔE/E~20%, are expected to heat the targets more uniformly than a beam of 140-MeV aluminum ions with zero energy spread. As a result, the robustness of the expected heatingmore » uniformity relative to the changes in the incident ion energy spectra is evaluated, and expected plasma temperatures of various target materials achievable with the current experimental platform are presented.« less

  3. Modeling target bulk heating resulting from ultra-intense short pulse laser irradiation of solid density targets

    SciTech Connect

    Antici, P.; Gremillet, L.; Grismayer, T.; Audebert, P.; Mančic, A.; Fuchs, J.; Borghesi, M.; Cecchetti, C. A.

    2013-12-15

    Isochoric heating of solid-density matter up to a few tens of eV is of interest for investigating astrophysical or inertial fusion scenarios. Such ultra-fast heating can be achieved via the energy deposition of short-pulse laser generated electrons. Here, we report on experimental measurements of this process by means of time- and space-resolved optical interferometry. Our results are found in reasonable agreement with a simple numerical model of fast electron-induced heating.

  4. A new analytical approach for heat generation in tissue due to laser excitation (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Erkol, Hakan; Nouizi, Farouk; Luk, Alex T.; Unlu, Mehmet B.; Gulsen, Gultekin

    2016-03-01

    In this study, we present a fast analytical approach for laser induced temperature increase in biological tissue. The whole problem consists of two main steps. These steps are the light propagation and heat transfer in tissue. We first obtain a detailed analytical solution for the diffusion equation based on an integral approach for specific boundary conditions. Secondly, we also solve the Pennes' bio-heat transfer equation analytically using the separation of variables technique and obtain the temperature induced by optical absorption of tissue. Here, heat source term consists of the local absorption and photon density, which will be determined from the diffusion equation. We find a very comprehensive solution for the diffusion equation by using an integral method for the Robin boundary condition. In other words, we obtain a particular Green's function in a different way. Next, we use this solution as a source term in the Pennes' bio-heat equation by utilizing the heat convection boundary condition. It is important to note that these boundary conditions are good approximations for imaging of biological tissue. As a result, we obtain spatio-temporal temperature distribution inside the medium. First, our approach is validated by a numerical approach using a Finite Element Method (FEM). Next, we also validate our method by performing phantom and tissue experiments. Experimental data corresponding to spatio-temporal temperature distribution are recorded using magnetic resonance thermometry. The analytical results obtained by our method are in a very good agreement with ones obtained by the FEM and experiment.

  5. Use of a laser-induced fluorescence thermal imaging system for film cooling heat transfer measurement

    SciTech Connect

    Chyu, M.K.

    1995-10-01

    This paper describes a novel approach based on fluorescence imaging of thermographic phosphor that enables the simultaneous determination of both local film effectiveness and local heat transfer on a film-cooled surface. The film cooling model demonstrated consists of a single row of three discrete holes on a flat plate. The transient temperature measurement relies on the temperature-sensitive fluorescent properties of europium-doped lanthanum oxysulfide (La{sub 2}O{sub 2}S:EU{sup 3+}) thermographic phosphor. A series of full-field surface temperatures, mainstream temperatures, and coolant film temperatures were acquired during the heating of a test surface. These temperatures are used to calculate the heat transfer coefficients and the film effectiveness simultaneously. Because of the superior spatial resolution capability for the heat transfer data reduced from these temperature frames, the laser-induced fluorescence (LIF) imaging system, the present study observes the detailed heat transfer characteristics over a film-protected surface. The trend of the results agrees with those obtained using other conventional thermal methods, as well as the liquid crystal imaging technique. One major advantage of this technique is the capability to record a large number of temperature frames over a given testing period. This offers multiple-sample consistency.

  6. Testing of the Geoscience Laser Altimeter System (GLAS) Prototype Loop Heat Pipe

    NASA Technical Reports Server (NTRS)

    Douglas, Donya; Ku, Jentung; Kaya, Tarik

    1998-01-01

    This paper describes the testing of the prototype loop heat pipe (LHP) for the Geoscience Laser Altimeter System (GLAS). The primary objective of the test program was to verify the loop's heat transport and temperature control capabilities under conditions pertinent to GLAS applications. Specifically, the LHP had to demonstrate a heat transport capability of 100 W, with the operating temperature maintained within +/-2K while the condenser sink was subjected to a temperature change between 273K and 283K. Test results showed that this loop heat pipe was more than capable of transporting the required heat load and that the operating temperature could be maintained within +/-2K. However, this particular integrated evaporator-compensation chamber design resulted in an exchange of energy between the two that affected the overall operation of the system. One effect was the high temperature the LHP was required to reach before nucleation would begin due to inability to control liquid distribution during ground testing. Another effect was that the loop had a low power start-up limitation of approximately 25 W. These Issues may be a concern for other applications, although it is not expected that they will cause problems for GLAS under micro-gravity conditions.

  7. Use of a laser-induced fluorescence thermal imaging system for film cooling heat transfer measurement

    SciTech Connect

    Chyu, M.K.

    1996-04-01

    This paper describes a novel approach based on fluorescence imaging of thermographic phosphor that enables the simultaneous determination of both local film effectiveness and local heat transfer on a film-cooled surface. The film cooling model demonstrated consists of a single row of three discrete holes on a flat plate. The transient temperature measurement relies on the temperature-sensitive fluorescent properties of europium-doped lanthanum oxysulfide (La{sub 2}O{sub 2}S:Eu{sup +3}) thermographic phosphor. A series of full-field surface temperatures, mainstream temperatures, and coolant film temperatures were acquired during the heating of a test surface. These temperatures are used to calculate the heat transfer coefficients and the film effectiveness simultaneously. Because of the superior spatial resolution capability for the heat transfer data reduced from these temperature frames, the laser-induced fluorescence (LIF) imaging system, the present study observes the detailed heat transfer characteristics over a film-protected surface. The trend of the results agrees with those obtained using other conventional thermal methods, as well as the liquid crystal imaging technique. One major advantage of this technique is the capability to record a large number of temperature frames over a given testing period. This offers multiple-sample consistency.

  8. Enhanced Raman scattering for temperature measurement of a laser-heated atomic force microscope tip

    NASA Astrophysics Data System (ADS)

    McCarthy, Brendan; Zhao, Yanming; Grover, Ranjan; Sarid, Dror

    2005-03-01

    Illuminating a silicon cantilever of an atomic force microscope with a focused laser beam creates heat that can be funneled into a nanoscale area at the apex of its tip. To characterize the heating dynamics and measure the temperature of the tip, a Raman scattering pump-and-probe method is used. It is found that at the apex of the tip the intensity of the Raman Stokes and anti-Stokes components are significantly enhanced relative to those obtained on a bulk silicon sample. Modeling the temperature rise at the tip of the cantilever by a closed-form analytical expression gives good agreement with the Raman measurements. This model can be used to design the structure of the cantilever so that the heat delivery to its tip is optimized. Such an optimized cantilever can potentially be used in high-density, heat-assisted magnetic recording, optical data storage using phase-change media and thermomechanical recording systems, for example, where nanoscale heated regions are of importance.

  9. Heat accumulation regime of femtosecond laser writing in fused silica and Nd:phosphate glass

    NASA Astrophysics Data System (ADS)

    Bukharin, M. A.; Khudyakov, D. V.; Vartapetov, S. K.

    2015-04-01

    We investigated refractive index induced by direct femtosecond laser writing inside fused silica and Nd:phosphate glass in heat accumulation regime. Spatial profile and magnitude of induced refractive index were investigated at various pulse repetition rates and translation velocities. It was shown that the magnitude of induced refractive index significantly rises with decreasing in time interval between successive laser pulses below the time for thermal diffusion. Going from nonthermal regime to heat accumulation regime, we achieved induced refractive index growth from 4 × 10-3 up to 6.5 × 10-3 in fused silica and from -6 × 10-3 to -9 × 10-3 in Nd:phosphate glass. Aspect ratio of treated area decreased from 2.1 down to less than 1.5 without correcting optical elements. It was shown that in heat accumulation regime, the treated area was surrounded by region of alternatively changed refractive index with significant magnitude up to -2 × 10-3. Wide regions of decreased refractive index enable fabrication of depressed cladding waveguides. We demonstrated low-loss (0.3 dB/cm) tubular waveguide inside fused silica. For orthogonal polarizations of guiding light, we achieved a small difference between losses as 0.1 dB/cm using highly symmetric written tracks forming the cladding. The desired structure was simulated with the beam propagation method, and the results were in good agreement with experiment data.

  10. Equation of state studies of warm dense matter samples heated by laser produced proton beams

    NASA Astrophysics Data System (ADS)

    Hoarty, D. J.; Guymer, T.; James, S. F.; Gumbrell, E.; Brown, C. R. D.; Hill, M.; Morton, J.; Doyle, H.

    2012-03-01

    Heating of matter by proton beams produced by short pulse, laser-solid target interaction has been demonstrated over the last ten years by a number of workers. In the work described in this paper heating by a pulse of laser produced protons has been combined with high-resolution soft x-ray radiography to record the expansion of thin wire targets. Analysis of the radiographs yields material properties in the warm dense matter regime. These measurements imply initial temperatures in the experimental samples over a range from 14 eV up to 40 eV; the sample densities varied from solid to a tenth solid density. Assuming an adiabatic expansion after the initial proton heating phase isentropes of the aluminium sample material were inferred and compared to tabulated data from the SESAME equation of state library. The proton spectrum was also measured using calibrated magnetic spectrometers and radiochromic film. The accuracy of the technique used to infer material data is discussed along with possible future development.

  11. Heating of nonequilibrium electrons by laser radiation in solid transparent dielectrics

    SciTech Connect

    Nikiforov, A. M. Epifanov, A. S.; Garnov, S. V.

    2011-01-15

    A computer simulation of the heating of nonequilibrium electrons by an intense high-frequency electromagnetic field leading to the bulk damage of solid transparent dielectrics under single irradiation has been carried out. The dependences of the avalanche ionization rate on threshold field strength have been derived. Using the Fokker-Planck equation with a flux-doubling boundary condition is shown to lead to noticeable errors even at a ratio of the photon energy to the band gap {approx}0.1. The series of dependences of the critical fields on pulse duration have been constructed for various initial lattice temperatures and laser wavelengths, which allow the electron avalanche to be identified as a limiting breakdown mechanism. The ratio of the energy stored in the electron subsystem to the excess (with respect to the equilibrium state) energy of the phonon subsystem by the end of laser pulse action has been calculated both with and without allowance for phonon heating. The influence of phonon heating on the impact avalanche ionization rate is analyzed.

  12. Nucleation dynamics around single microabsorbers in water heated by nanosecond laser irradiation

    SciTech Connect

    Neumann, Joerg; Brinkmann, Ralf

    2007-06-01

    Suspensions containing micro- and nanoabsorbers, which are irradiated by short laser pulses, are used for a manifold of procedures in medicine, biotechnology, and other fields. Detailed knowledge of the bubble nucleation and dynamics, which is induced by the heat transfer from the absorber to the surrounding transparent water, is essential for understanding the underlying processes occurring on a microscopic scale. We investigated the rapid phase change phenomena including temperature, heating rates, pressure generation, bubble nucleation, and initial bubble growth around absorbing micron-sized melanin particles (retinal pigment epithelial melanosomes) during irradiation with 12 ns (full width at half maximum) laser pulses at a wavelength of 532 nm. The melanosomes were heated at rates in the order of 10{sup 10} K/s. A mean bubble nucleation temperature of 136 deg. C was found. The initial bubble expansion was observed by time-resolved microscopy. The expansion velocities range from 10 m/s at 1.5-fold to 85 m/s at 8.5-fold threshold radiant exposure for bubble formation, respectively. The expansion velocity increases in the investigated range almost linearly with the applied radiant exposure.

  13. Manufacturing of a high-temperature resistojet heat exchanger by selective laser melting

    NASA Astrophysics Data System (ADS)

    Romei, F.; Grubišić, A. N.; Gibbon, D.

    2017-09-01

    The paper presents the design, manufacturing and postproduction analysis of a novel high-temperature spacecraft resistojet heat exchanger manufactured through selective laser melting to validate the manufacturing approach. The work includes the analysis of critical features of a heat exchanger with integrated converging-diverging nozzle as a single piece element. The metrology of the component is investigated using optical analysis and profilometry to verify the integrity of components. High-resolution micro-Computed Tomography (CT) is applied as a tool for volumetric non-destructive inspection and conformity since the complex geometry of the thruster does not allow internal examination. The CT volume data is utilised to determine a surface mesh on which a novel perform coordinate measurement technique is applied for nominal/actual comparison and wall thickness analysis. A thin-wall concentric tubular heat exchanger design is determined to meet dimensional accuracy requirements. The work indicates the production of fine structures with feature sizes below 200 μm in 316L stainless via selective laser melting is feasible and opens up new possibilities for the future developments in multiple industries.

  14. Heating of nonequilibrium electrons by laser radiation in solid transparent dielectrics

    NASA Astrophysics Data System (ADS)

    Nikiforov, A. M.; Epifanov, A. S.; Garnov, S. V.

    2011-01-01

    A computer simulation of the heating of nonequilibrium electrons by an intense high-frequency electromagnetic field leading to the bulk damage of solid transparent dielectrics under single irradiation has been carried out. The dependences of the avalanche ionization rate on threshold field strength have been derived. Using the Fokker-Planck equation with a flux-doubling boundary condition is shown to lead to noticeable errors even at a ratio of the photon energy to the band gap ˜0.1. The series of dependences of the critical fields on pulse duration have been constructed for various initial lattice temperatures and laser wavelengths, which allow the electron avalanche to be identified as a limiting breakdown mechanism. The ratio of the energy stored in the electron subsystem to the excess (with respect to the equilibrium state) energy of the phonon subsystem by the end of laser pulse action has been calculated both with and without allowance for phonon heating. The influence of phonon heating on the impact avalanche ionization rate is analyzed.

  15. Pulsed laser Raman spectroscopy in the laser-heated diamond anvil cell

    SciTech Connect

    Goncharov, A F; Crowhurst, J C

    2005-03-24

    We describe the design and operation of a spatially-filtered Raman/fluorescence spectrometer that incorporates a pulsed 532 nm laser excitation source and a synchronized and electronically gated CCD detector. This system permits the suppression of undesired continuous radiation from various sources by a factor of up to 50,000 providing the possibility of acquiring Raman signals at temperatures exceeding 5,000 K. We present performance comparisons of this system with that of a state-of-the-art conventional CW system using a 458 nm excitation source. We also demonstrate that the pulsed system is capable of suppressing an impurity-induced (single nitrogen defects) fluorescence in diamond, and further suggest that this capability can be used to suppress the stress-induced fluorescence in diamond that may appear at pressures near or above 150 GPa.

  16. Metal vapor laser including hot electrodes and integral wick

    DOEpatents

    Ault, E.R.; Alger, T.W.

    1995-03-07

    A metal vapor laser, specifically one utilizing copper vapor, is disclosed herein. This laser utilizes a plasma tube assembly including a thermally insulated plasma tube containing a specific metal, e.g., copper, and a buffer gas therein. The laser also utilizes means including hot electrodes located at opposite ends of the plasma tube for electrically exciting the metal vapor and heating its interior to a sufficiently high temperature to cause the metal contained therein to vaporize and for subjecting the vapor to an electrical discharge excitation in order to lase. The laser also utilizes external wicking arrangements, that is, wicking arrangements located outside the plasma tube. 5 figs.

  17. Metal vapor laser including hot electrodes and integral wick

    DOEpatents

    Ault, Earl R.; Alger, Terry W.

    1995-01-01

    A metal vapor laser, specifically one utilizing copper vapor, is disclosed herein. This laser utilizes a plasma tube assembly including a thermally insulated plasma tube containing a specific metal, e.g., copper, and a buffer gas therein. The laser also utilizes means including hot electrodes located at opposite ends of the plasma tube for electrically exciting the metal vapor and heating its interior to a sufficiently high temperature to cause the metal contained therein to vaporize and for subjecting the vapor to an electrical discharge excitation in order to lase. The laser also utilizes external wicking arrangements, that is, wicking arrangements located outside the plasma tube.

  18. Experimental Analysis of Heat Flux to a Blunt Body in Hypersonic Flow with Upstream Laser Energy Deposition — Preliminary Results

    NASA Astrophysics Data System (ADS)

    Salvador, I. I.; Minucci, M. A. S.; Toro, P. G. P.; Oliveira, A. C.; Channes, J. B.; Myrabo, L. N.; Nagamatsu, H. T.

    2006-05-01

    Due to high heat transfer rates in hypersonic flight and its consequent necessity of prohibitively massive thermal protection system, new methods of flow control are required to enable flight in such regimes. Here arises the Direct Energy Air Spike concept, where electromagnetic energy (laser/microwaves) is focalized upstream of the model causing the breakdown of the air and the generation of a Laser Supported Detonation wave which diverts the incoming stream parabolically. In this preliminary work, the heat transfer rates to the surface of a blunt body, downstream the laser induced shock wave, were qualitatively measured and compared with the results without the DEAS. These measurements were conducted with the use of fast response coaxial thermocouples and piezoelectric pressure transducers installed on the surface of the model in the 0.30m IEAv's T2 Hypersonic Shock Tunnel. The laser energy was supplied by a CO2 TEA Laser.

  19. Characterization of proton and heavier ion acceleration in ultrahigh-intensity laser interactions with heated target foils.

    PubMed

    McKenna, P; Ledingham, K W D; Yang, J M; Robson, L; McCanny, T; Shimizu, S; Clarke, R J; Neely, D; Spohr, K; Chapman, R; Singhal, R P; Krushelnick, K; Wei, M S; Norreys, P A

    2004-09-01

    Proton and heavy ion acceleration in ultrahigh intensity ( approximately 2 x 10(20) W cm(-2) ) laser plasma interactions has been investigated using the new petawatt arm of the VULCAN laser. Nuclear activation techniques have been applied to make the first spatially integrated measurements of both proton and heavy ion acceleration from the same laser shots with heated and unheated Fe foil targets. Fe ions with energies greater than 10 MeV per nucleon have been observed. Effects of target heating on the accelerated ion energy spectra and the laser-to-ion energy conversion efficiencies are discussed. The laser-driven production of the long-lived isotope (57 )Co (271 days) via a heavy ion induced reaction is demonstrated.

  20. Monitoring annealing via carbon dioxide laser heating of defect populations in fused silica surfaces using photoluminescence microscopy

    SciTech Connect

    Raman, R N; Matthews, M J; Adams, J J; Demos, S G

    2010-02-01

    Photoluminescence (PL) microscopy and spectroscopy under 266 nm and 355 nm laser excitation are explored as a means of monitoring defect populations in laser-modified sites on the surface of fused silica and their subsequent response to heating to different temperatures via exposure to a CO{sub 2} laser beam. Laser-induced temperature changes were estimated using an analytic solution to the heat flow equation and compared to changes in the PL emission intensity. The results indicate that the defect concentrations decrease significantly with increasing CO{sub 2} laser exposure and are nearly eliminated when the peak surface temperature exceeds the softening point of fused silica ({approx}1900K), suggesting that this method might be suitable for in situ monitoring of repair of defective sites in fused silica optical components.

  1. Pulsed Nd:YAG laser welding of cardiac pacemaker batteries with reduced heat input

    SciTech Connect

    Fuerschbach, P.W.; Hinkley, D.A.

    1997-03-01

    The effects of Nd:YAG laser beam welding process parameters on the resulting heat input in 304L stainless steel cardiac pacemaker batteries have been studied. By careful selection of process parameters, the results can be used to reduce temperatures near glass-to-metal seals and assure hermeticity in laser beam welding of high reliability components. Three designed response surface experiments were used to compare welding performance with lenses of varying focal lengths. The measured peak temperatures at the glass-to-metal seals varied from 65 to 140 C (149 to 284 F) and depended strongly on the levels of the experimental factors. It was found that welds of equivalent size can be made with significantly reduced temperatures. The reduction in battery temperatures has been attributed to an increase in the melting efficiency. This increase is thought to be due primarily to increased travel speeds, which were facilitated by high peak powers and low pulse energies. For longer focal length lenses, weld fusion zone widths were found to be greater even without a corresponding increase in the size of the weld. It was also found that increases in laser beam irradiance either by higher peak powers or smaller spot sizes created deeper and larger welds. These gains were attributed to an increase in the laser energy transfer efficiency.

  2. Microthermometry of laser-heated Chinese hamster ovary cells and sperm cells

    NASA Astrophysics Data System (ADS)

    Liu, Yagang; Sonek, Gregory J.; Chapman, Curtis F.; Tromberg, Bruce J.; Patrizio, Pasquale; Tadir, Yona; Berns, Michael W.

    1995-05-01

    Microthermometric measurements on optically-trapped Chinese Hamster Ovary (CHO) cells and sperms cells re reported, using a noninvasive microfluorometric detection technique. Within an optical tweezer system that has been outfitted with a spectral fluorescence excitation and detection capability, the changes in temperature induced by the process of sample confinement by a focused laser beam has been quantified over micron-sized spatial regions of both motile and immotile cells. Our measurement technique is based on the use of environmentally sensitive fluorophores that can be incorporated into the cell membrane and used to sense local changes in temperature when the cell membrane is perturbed optically or via other environmental stress factors. Using a cw 1.064 micrometers Nd:YAG laser for trapping CHO and human sperm cells, a temperature increase of approximately equals 1°C per 100 mW laser power was observed. At this infrared wavelength, cellular heating as result of laser confinement appears to be mainly due to radiation absorption by water.

  3. Single-pulse excimer laser nanostructuring of silicon: A heat transfer problem and surface morphology

    SciTech Connect

    Eizenkop, Julia; Avrutsky, Ivan; Georgiev, Daniel G.; Chaudchary, Vipin

    2008-05-01

    We present computer modeling along with experimental data on the formation of sharp conical tips on silicon-based three-layer structures that consist of a single-crystal Si layer on a 1 {mu}m layer of silica on a bulk Si substrate. The upper Si layers with thicknesses in the range of 0.8-4.1 {mu}m were irradiated by single pulses from a KrF excimer laser focused onto a spot several micrometers in diameter. The computer simulation includes two-dimensional time-dependent heat transfer and phase transformations in Si films that result from the laser irradiation (the Stefan problem). After the laser pulse, the molten material self-cools and resolidifies, forming a sharp conical structure, the height of which can exceed 1 {mu}m depending on the irradiation conditions. We also performed computer simulations for experiments involving single-pulse irradiation of bulk silicon, reported by other groups. We discuss conditions under which different types of structures (cones versus hollows) emerge. We confirm a correlation between the presence of the lateral resolidification condition after the laser pulse and the presence of conical structures on a solidified surface.

  4. LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Change in the optical properties of hyaline cartilage heated by the near-IR laser radiation

    NASA Astrophysics Data System (ADS)

    Bagratashvili, Viktor N.; Bagratashvili, N. V.; Gapontsev, V. P.; Makhmutova, G. Sh; Minaev, V. P.; Omel'chenko, A. I.; Samartsev, I. E.; Sviridov, A. P.; Sobol', E. N.; Tsypina, S. I.

    2001-06-01

    The in vitro dynamics of the change in optical properties of hyaline cartilage heated by fibre lasers at wavelengths 0.97 and 1.56 μm is studied. The laser-induced bleaching (at 1.56 μm) and darkening (at 0.97 μm) of the cartilage, caused by the heating and transport of water as well as by a change in the cartilage matrix, were observed and studied. These effects should be taken into account while estimating the depth of heating of the tissue. The investigated dynamics of light scattering in the cartilage allows one to choose the optimum radiation dose for laser plastic surgery of cartilage tissues.

  5. Dynamic Face Seal Arrangement

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher (Inventor)

    1999-01-01

    A radial face seal arrangement is disclosed comprising a stationary seal ring that is spring loaded against a seal seat affixed to a rotating shaft. The radial face seal arrangement further comprises an arrangement that not only allows for preloading of the stationary seal ring relative to the seal seat, but also provides for dampening yielding a dynamic seating response for the radial face seal arrangement. The overall seal system, especially regarding the selection of the material for the stationary seal ring, is designed to operate over a wide temperature range from below ambient up to 900 C.

  6. Three-dimensional modelling of heat transfer and fluid flow in laser full-penetration welding

    NASA Astrophysics Data System (ADS)

    Ye, Xiao-Hu; Chen, Xi

    2002-05-01

    Modelling results are presented concerning the laser full-penetration welding characteristics. The effects of welding speed, Marangoni convection and natural convection on melt flow and heat transfer are all included in the modelling, and thus a three-dimensional (3-D) approach is employed. Comparison of the present 3-D modelling results with corresponding two-dimensional ones shows that besides the welding speed, Marangoni convection also plays critical role in determining the temperature distribution in the workpiece and melt flow in the weld pool and cannot be ignored even for the full-penetration welding of a thin plate. A method is described concerning how to use the present 3-D modelling results to estimate the keyhole radius or predict the energy efficiency in the laser full-penetration welding.

  7. Coupled light transport-heat diffusion model for laser dosimetry with dynamic optical properties

    SciTech Connect

    London, R.A.; Glinsky, M.E.; Zimmerman, G.B.; Eder, D.C.; Jacques, S.L.

    1995-03-01

    The effect of dynamic optical properties on the spatial distribution of light in laser therapy is studied via numerical simulations. A two-dimensional, time dependent computer program called LATIS is used. Laser light transport is simulated with a Monte Carlo technique including anisotropic scattering and absorption. Thermal heat transport is calculated with a finite difference algorithm. Material properties are specified on a 2-D mesh and can be arbitrary functions of space and time. Arrhenius rate equations are solved for tissue damage caused by elevated temperatures. Optical properties are functions of tissue damage, as determined by previous measurements. Results are presented for the time variation of the light distribution and damage within the tissue as the optical properties of the tissue are altered.

  8. Prediction of laser cutting heat affected zone by extreme learning machine

    NASA Astrophysics Data System (ADS)

    Anicic, Obrad; Jović, Srđan; Skrijelj, Hivzo; Nedić, Bogdan

    2017-01-01

    Heat affected zone (HAZ) of the laser cutting process may be developed based on combination of different factors. In this investigation the HAZ forecasting, based on the different laser cutting parameters, was analyzed. The main goal was to predict the HAZ according to three inputs. The purpose of this research was to develop and apply the Extreme Learning Machine (ELM) to predict the HAZ. The ELM results were compared with genetic programming (GP) and artificial neural network (ANN). The reliability of the computational models were accessed based on simulation results and by using several statistical indicators. Based upon simulation results, it was demonstrated that ELM can be utilized effectively in applications of HAZ forecasting.

  9. Highly textured fresnoite thin films synthesized in situ by pulsed laser deposition with CO2 laser direct heating

    NASA Astrophysics Data System (ADS)

    Lorenz, Michael; de Pablos-Martin, Araceli; Patzig, Christian; Stölzel, Marko; Brachwitz, Kerstin; Hochmuth, Holger; Grundmann, Marius; Höche, Thomas

    2014-01-01

    Fresnoite Ba2TiSi2O8 (BTS) thin films were grown and crystallized in situ using pulsed laser deposition (PLD) with CO2 laser direct heating of the a-plane sapphire (1 1 0) substrates up to 1250 °C. Starting with 775 °C growth temperature, (0 0 1)- and (1 1 0)-textured BTS and BaTiO3 phases, respectively, could be assigned in the films, and the typical fern-like BTS crystallization patterns appear. For higher process temperatures of 1100 to 1250 °C, atomically smooth, terraced surface of the films was found, accompanied by crystalline high-temperature phases of Ba-Ti-Si oxides. HAADF micrographs taken in both scanning transmission electron microscopy and energy-dispersive x-ray spectrometry mode show details of morphology and elemental distribution inside the films and at the interface. To balance the inherent Si deficiency of the BTS films, growth from glassy BTS × 2 SiO2 and BTS × 2.5 SiO2 targets was considered as well. The latter targets are ideal for PLD since the employed glasses possess 100% of the theoretical density and are homogeneous at the atomic scale.

  10. Melting of nanocrystals embedded in a crystal matrix heated by nanosecond laser pulses

    SciTech Connect

    Zinoviev, V. A. Dvurechenskii, A. V.; Smagina, Zh. V.; Ivlev, G. D.; Gatskevich, E. I.; Malevich, V. L.

    2012-09-15

    The kinetics of phase transformations of nanocrystals in a crystal matrix is considered upon non-stationary heating by laser pulses. The melting and crystallization kinetics of nanocrystals is described taking into account their size, shape, elemental composition, and elastic deformations appearing due to the mismatch of the lattice constants for nanocrystals and the matrix. The possibility of decreasing the dispersion of nanocrystals over their size in heterostructures with quantum dots is predicted. As an example, melting of Ge nanocrystals in a Si matrix is considered.

  11. Planarization of metal films for multilevel interconnects by pulsed laser heating

    DOEpatents

    Tuckerman, David B.

    1987-01-01

    In the fabrication of multilevel integrated circuits, each metal layer is planarized by heating to momentarily melt the layer. The layer is melted by sweeping laser pulses of suitable width, typically about 1 microsecond duration, over the layer in small increments. The planarization of each metal layer eliminates irregular and discontinuous conditions between successive layers. The planarization method is particularly applicable to circuits having ground or power planes and allows for multilevel interconnects. Dielectric layers can also be planarized to produce a fully planar multilevel interconnect structure. The method is useful for the fabrication of VLSI circuits, particularly for wafer-scale integration.

  12. Laser-heat puncturing as highly effective method of post-tuberculous cystalgia treatment

    NASA Astrophysics Data System (ADS)

    Koultchavenia, Ekaterina V.

    1999-07-01

    The tuberculosis of an urine bladder in men develops is authentic less often, and recovery is authentic more often, than in the women. In 39,1 percent of the women with nephrotuberculosis and urocystis and urocystis tuberculosis a specific cystitides is finished in development of post- tuberculous cystalgia. One of starting mechanism of dysuria after the transferred urocystis tuberculosis in the women in menopause is hormonal insufficiency. The method of laser heat puncturing, developed by us, for the treatment this complication is highly effective, does not require additional introduction of medicines, can be executed as in hospitals, and in our-patient.

  13. Acceleration to High Velocities and Heating by Impact Using Nike KrF Laser

    DTIC Science & Technology

    2010-01-01

    Acceleration to high velocities and heating by impact using Nike KrF laser. Max Karasik,1, ∗ J. L. Weaver,1 Y. Aglitskiy,2 T. Watari ,3 Y. Arikawa,3 T...Azechi, T. Sakaiya, T. Watari , M. Karasik, H. Saito, K. Ohtani, K. Takeda, H. Hosoda, H. Shiraga, M. Nakai, et al., Phys. Rev. Lett. 102, 235002 (2009...Fusion Res. 83, 831 (2007). [17] S. Y. Gus’kov, H. Azechi, N. N. Demchenko, I. Y. Doskoch, M. Murakami, V. B. Rozanov, T. Sakaiya, T. Watari , and N. V

  14. Thermophysical processes initiated by inert-matrix-hosted nanoparticles heated by laser pulses of different durations

    NASA Astrophysics Data System (ADS)

    Kalenskii, A. V.; Zvekov, A. A.; Nikitin, A. P.; Aduev, B. P.

    2016-03-01

    In the present study, a model for the heating of inert-matrix-hosted metal nanoparticles with laser radiation taking into account the melting processes is examined. The calculations were performed using the characteristics of gold and pentaerythritol tetranitrate materials. The kinetic dependences of the temperature and molten-layer thickness on nanoparticle surface were calculated. The main non-dimensional governing parameters of the model were identified. An expression for the maximum thickness of molten layer was obtained. The results can be used in predicting the stability of nonlinear-optics devices with hosted gold nanoparticles, in raising the efficiency of hyperthermia cancer therapy, and in optimizing the optical detonators.

  15. Acceleration to high velocities and heating by impact using Nike KrF laser

    SciTech Connect

    Karasik, Max; Weaver, J. L.; Velikovich, A. L.; Zalesak, S. T.; Bates, J. W.; Obenschain, S. P.; Schmitt, A. J.; Aglitskiy, Y.; Watari, T.; Arikawa, Y.; Sakaiya, T.; Murakami, M.; Azechi, H.; Oh, J.

    2010-05-15

    The Nike krypton fluoride laser [S. P. Obenschain, S. E. Bodner, D. Colombant, et al., Phys. Plasmas 3, 2098 (1996)] is used to accelerate planar plastic foils to velocities that for the first time reach 1000 km/s. Collision of the highly accelerated deuterated polystyrene foil with a stationary target produces approxGbar shock pressures and results in heating of the foil to thermonuclear temperatures. The impact conditions are diagnosed using DD fusion neutron yield, with approx10{sup 6} neutrons produced during the collision. Time-of-flight neutron detectors are used to measure the ion temperature upon impact, which reaches 2-3 keV.

  16. CONTROL OF LASER RADIATION PARAMETERS: Compensation for thermally induced aberrations in optical elements by means of additional heating by CO2 laser radiation

    NASA Astrophysics Data System (ADS)

    Soloviev, A. A.; Kozhevatov, I. E.; Palashov, O. V.; Khazanov, E. A.

    2006-10-01

    A method is proposed for compensating thermally induced phase distortions of laser radiation in absorbing optical elements. The method is based on supplementary heating of the peripheral region of the distorting element by the radiation from an auxiliary laser. A programme code has been developed for calculating the optimal parameters of supplementary radiation for minimising phase distortions. This code is based on the numerical solution of the thermal conductivity and static elasticity equations for a nonuniformly heated solid of cylindrical symmetry. Experiments reveal a high efficiency of the method for compensating distortions resulting from absorption of radiation with a Gaussian intensity profile.

  17. First Results from Laser-Driven MagLIF Experiments on OMEGA: Time Evolution of Laser Gas Heating Using Soft X-Ray Diagnostics

    NASA Astrophysics Data System (ADS)

    Barnak, D. H.; Betti, R.; Chang, P.-Y.; Davies, J. R.

    2015-11-01

    Magnetized liner inertial fusion (MagLIF) is a promising inertial confinement fusion scheme comprised of three stages: axial magnetization, laser heating of the deuterium -tritium gas fill, and compression of the gas by the liner. To study the physics of MagLIF, a scaled-down version has been designed and implemented on the OMEGA-60 laser. This talk will focus primarily on the heating process of a MagLIF target using a 351-nm laser. A neon-doped deuterium gas capsule was heated using a 2.5-ns square pulse delivering 200 J of laser energy. Spectral analysis of the x-ray emission from the side and the laser entrance hole of the capsule is used to infer the time evolution of the gas temperature. The x-ray spectra for a grid of possible gas temperatures and densities are simulated using Spect3D atomic modeling software. The simulation results are then used to deconvolve the raw signals and obtain density and temperature estimations. A gas temperature lower bound of 100 eV at 1.3 ns after the start of the laser pulse can be inferred from these estimations. The estimations are then compared to 2-D hydrocode modeling. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and by DE-FG02-04ER54786 and DE-FC02-04ER54789 (Fusion Science Center).

  18. Incubation behavior of silicon nanowire growth investigated by laser-assisted rapid heating

    SciTech Connect

    Ryu, Sang-gil; Kim, Eunpa; Grigoropoulos, Costas P.; Allen, Frances I.; Minor, Andrew M.; Hwang, David J.

    2016-08-15

    We investigate the early stage of silicon nanowire growth by the vapor-liquid-solid mechanism using laser-localized heating combined with ex-situ chemical mapping analysis by energy-filtered transmission electron microscopy. By achieving fast heating and cooling times, we can precisely determine the nucleation times for nanowire growth. We find that the silicon nanowire nucleation process occurs on a time scale of ∼10 ms, i.e., orders of magnitude faster than the times reported in investigations using furnace processes. The rate-limiting step for silicon nanowire growth at temperatures in the vicinity of the eutectic temperature is found to be the gas reaction and/or the silicon crystal growth process, whereas at higher temperatures it is the rate of silicon diffusion through the molten catalyst that dictates the nucleation kinetics.

  19. Study of heat sources interacting in integrated circuits by laser mirage effect

    SciTech Connect

    Perpiñà, X.; Jordà, X.; Vellvehi, M.; Altet, J.

    2014-08-25

    This work exploits the mirage effect to analyze multiple heat sources thermally interacting in an integrated circuit (IC) by means of a probe IR laser beam, which strikes on the die lateral walls and passes through the die substrate. Under such conditions, the criteria for locating such hot spots, as well as their relative power dissipation, are discussed on the basis of a theoretical model inferred in this work. Finally, the technique feasibility is shown in a real application scenario, obtaining 5-μm spatial lateral resolution and an error in power dissipation measurements below 5%. This method may become a practical alternative to usual off-chip techniques for inspecting hot spots in ICs and to experimentally characterize heat flow in the semiconductor substrate.

  20. Air side thermal performance of wavy fin heat exchangers produced by selective laser melting

    NASA Astrophysics Data System (ADS)

    Kuehndel, J.; Kerler, B.; Karcher, C.

    2016-09-01

    Wavy fins are widely used for off-road vehicle coolers, due to their dust resistance. In this study, heat exchanger elements with wavy fins were examined in an experimental study. Due to independence of tooling and degrees of freedom in design, rapid prototyping technique selective laser melting was used to produce heat exchanger elements with high dimensional accuracy. Tests were conducted for air side Reynolds number Re of 1400-7400 varying wavy amplitude and wave length at a constant water flow rate of 9.0m3/h inside the tubes. The effects of wavy amplitude and wave length on the air side thermal performance were studied. Experimental correlation equations for Nu and ­ were derived by regression analysis.

  1. Study of heat sources interacting in integrated circuits by laser mirage effect

    NASA Astrophysics Data System (ADS)

    Perpiñà, X.; Jordà, X.; Vellvehi, M.; Altet, J.

    2014-08-01

    This work exploits the mirage effect to analyze multiple heat sources thermally interacting in an integrated circuit (IC) by means of a probe IR laser beam, which strikes on the die lateral walls and passes through the die substrate. Under such conditions, the criteria for locating such hot spots, as well as their relative power dissipation, are discussed on the basis of a theoretical model inferred in this work. Finally, the technique feasibility is shown in a real application scenario, obtaining 5-μm spatial lateral resolution and an error in power dissipation measurements below 5%. This method may become a practical alternative to usual off-chip techniques for inspecting hot spots in ICs and to experimentally characterize heat flow in the semiconductor substrate.

  2. High-rate laser metal deposition of Inconel 718 component using low heat-input approach

    NASA Astrophysics Data System (ADS)

    Kong, C. Y.; Scudamore, R. J.; Allen, J.

    Currently many aircraft and aero engine components are machined from billets or oversize forgings. This involves significant cost, material wastage, lead-times and environmental impacts. Methods to add complex features to another component or net-shape surface would offer a substantial cost benefit. Laser Metal Deposition (LMD), currently being applied to the repair of worn or damaged aero engine components, was attempted in this work as an alternative process route, to build features onto a base component, because of its low heat input capability. In this work, low heat input and high-rate deposition was developed to deposit Inconel 718 powder onto thin plates. Using the optimised process parameters, a number of demonstrator components were successfully fabricated.

  3. Incubation behavior of silicon nanowire growth investigated by laser-assisted rapid heating

    NASA Astrophysics Data System (ADS)

    Ryu, Sang-gil; Kim, Eunpa; Allen, Frances I.; Hwang, David J.; Minor, Andrew M.; Grigoropoulos, Costas P.

    2016-08-01

    We investigate the early stage of silicon nanowire growth by the vapor-liquid-solid mechanism using laser-localized heating combined with ex-situ chemical mapping analysis by energy-filtered transmission electron microscopy. By achieving fast heating and cooling times, we can precisely determine the nucleation times for nanowire growth. We find that the silicon nanowire nucleation process occurs on a time scale of ˜10 ms, i.e., orders of magnitude faster than the times reported in investigations using furnace processes. The rate-limiting step for silicon nanowire growth at temperatures in the vicinity of the eutectic temperature is found to be the gas reaction and/or the silicon crystal growth process, whereas at higher temperatures it is the rate of silicon diffusion through the molten catalyst that dictates the nucleation kinetics.

  4. Laser thinning for monolayer graphene formation: heat sink and interference effect.

    PubMed

    Han, Gang Hee; Chae, Seung Jin; Kim, Eun Sung; Güneş, Fethullah; Lee, Il Ha; Lee, Sang Won; Lee, Si Young; Lim, Seong Chu; Jeong, Hae Kyung; Jeong, Mun Seok; Lee, Young Hee

    2011-01-25

    Despite the availability of large-area graphene synthesized by chemical vapor deposition (CVD), the control of a uniform monolayer graphene remained challenging. Here, we report a method of acquiring monolayer graphene by laser irradiation. The accumulation of heat on graphene by absorbing light, followed by oxidative burning of upper graphene layers, which strongly relies on the wavelength of light and optical parameters of the substrate, was in situ measured by the G-band shift in Raman spectroscopy. The substrate plays a crucial role as a heat sink for the bottom monolayer graphene, resulting in no burning or etching. Oscillatory thinning behavior dependent on the substrate oxide thickness was evaluated by adopting a simple Fresnel's equation. This paves the way for future research in utilizing monolayer graphene for high-speed electronic devices.

  5. Laser-bar stack using ELF heat-sinks mounted kinematically for double-sided cooling

    NASA Astrophysics Data System (ADS)

    Chin, A. K.; Manni, J. G.; Chin, R. H.; Levy, J.; Dogan, M.; Jacob, J. H.; Pathak, R.; Wessling, C.; Lang, K. D.; Eppich, H.; Fryer, J.; Haverkamp, T.

    2013-02-01

    We present a novel, high-power stack of 20% fill-factor, 976nm, laser-diode bars, each directly attached to an enhanced lateral-flow (ELF), copper-based, water-cooled heat-sink. The heat-sinks contain mounting screws that form a kinematic mount to minimize detrimental mechanical-stress on the diode bars while also providing beneficial, double-side cooling of the bars. A stack of 18-bars, emitting 2.54kW, was constructed to validate the technology. Using standard optics and a polarization multiplexer, a 320μm diameter, 0.3NA focus is achieved with a 6-bar stack that robustly couples 450W, with a ~67% coupling efficiency, from a passive, 400μm, 046NA doubleclad fiber.

  6. Novel thermal effect at nanoshell heating by pulsed laser irradiation: hoop-shaped hot zone formation.

    PubMed

    Avetisyan, Yuri A; Yakunin, Alexander N; Tuchin, Valery V

    2012-10-01

    Photonic nanotechnologies have good perspectives to be widely used in biophotonics. In this study we have developed an approach for calculation of nanoparticle temperature field accounting for absorbed local intensity at pulse laser radiation of composite spherical nanoparticles (nanoshells). This approach allowed us to analyze spatial inhomogeneities of light field diffracted into a nanoshell and corresponding distribution of the absorption energy and to provide numerical solution of time-dependent heat conduction equation accounting for corresponding spatially inhomogeneous distribution of heating sources. We were able to predict the appearance of a novel thermal effect - hoop-shaped hot zone on the nanoshell surface. The observed effect has potential applications in cell biology and medicine for controlled cell optoporation and nanosurgery, as well as cancer cell killing.

  7. Jet-type, water-cooled heat sink that yields 255-W continuous-wave laser output at 808 nm from a 1-cm laser diode bar.

    PubMed

    Miyajima, Hirofumi; Kan, Hirofumi; Kanzaki, Takeshi; Furuta, Shin-ichi; Yamanaka, Masanobu; Izawa, Yasukazu; Nakai, Sadao

    2004-02-01

    A newly designed jet-type, water-cooled heat sink (the funryu heat sink, meaning fountain flow in Japanese) yielded 255-W cw laser output at 808 nm from a 1-cm bar made from InGaAsP/InGaP quantum-well active layers with a 67% fill factor [70 quantum-well laser diode (LD) array along the 1-cm bar]. A funryu heat sink measuring 1.1 mm in thickness gave the LD 0.25 degrees C/W thermal resistance, one of the lowest values achieved with a 1-cm LD bar. Over a short period of operation, the device reached a maximum cw power of 255 W. To the best of our knowledge, this is the highest power ever achieved in 808-nm LD operation. In the future, the funryu heat sink may be capable of 80-W cw operation over an extended lifetime of several thousand hours.

  8. CALUTRON PLANT ARRANGEMENT

    DOEpatents

    Waite, L.O.

    1959-06-01

    A description is given of an arrangement for calutrons in which the tanks and magnets are placed alternately in a race track'' figure. Pump connections are through the floor to the pumps below where roughing and finishing headers are provided. The arrangement provides more efficient and exonomical operaton, economy of construction, and saving of space. (T.R.H.)

  9. Teaching Arrangement Inductively.

    ERIC Educational Resources Information Center

    Mendelson, Michael

    1988-01-01

    Argues that teaching arrangement inductively offers an alternative to the standard imitation of business communication text models. Asserts that the inductive method stimulates individual rather than formulaic responses to the problems of organization, and that inductively-trained writers see arrangements as a powerful element in persuasive…

  10. Dicing of high-power white LEDs in heat sinks with the water jet-guided laser

    NASA Astrophysics Data System (ADS)

    Mai, Tuan Anh; Housh, Roy; Brulé, Arnaud; Richerzhagen, Bernold

    2007-02-01

    High-brightness LEDs are compound semiconductor devices and distinguish themselves from conventional LEDs by their exceptional luminosity. Today they are increasingly used as light sources, replacing conventional incandescent and fluorescent lamp technologies. HB LEDs are difficult to manufacture, as they must be grown by sophisticated epitaxial growth techniques such as MOCVD. They are packaged like power semiconductors, using surface mount technology and thermal pads. After having been successfully applied to GaN scribing for side-emitting LEDs, the Laser MicroJet (R) is used today for cutting heat sinks of HB white LEDs. Due to the high-emitted light power, the generated heat must be dissipated through a heat sink. Materials typically employed are metals with high heat conductivity, notably CuW and molybdenum. Applying the Laser MicroJet (R) the achieved cutting quality in these metals is outstanding - smooth edges, no contamination, no burrs, no heat damage, no warping - all this at high speed.

  11. Novel mono-static arrangement of the ASDEX Upgrade high field side reflectometers compatible with electron cyclotron resonance heating stray radiationa)

    NASA Astrophysics Data System (ADS)

    Silva, A.; Varela, P.; Meneses, L.; Manso, M.; ASDEX Upgrade Team

    2012-10-01

    The ASDEX Upgrade frequency modulated continuous wave broadband reflectometer system uses a mono-static antenna configuration with in-vessel hog-horns and 3 dB directional couplers. The operation of the new electron cyclotron resonance heating (ECRH) launcher and the start of collective Thomson scattering experiments caused several events where the fragile dummy loads inside the high field side directional couplers were damaged, due to excessive power resulting from the ECRH stray fields. In this paper, we present a non-conventional application of the existing three-port directional coupler that hardens the system to the ECRH stray fields and at the same time generates the necessary reference signal. Electromagnetic simulations and laboratory tests were performed to validate the proposed solution and are compared with the in-vessel calibration tests.

  12. Novel mono-static arrangement of the ASDEX Upgrade high field side reflectometers compatible with electron cyclotron resonance heating stray radiation.

    PubMed

    Silva, A; Varela, P; Meneses, L; Manso, M

    2012-10-01

    The ASDEX Upgrade frequency modulated continuous wave broadband reflectometer system uses a mono-static antenna configuration with in-vessel hog-horns and 3 dB directional couplers. The operation of the new electron cyclotron resonance heating (ECRH) launcher and the start of collective Thomson scattering experiments caused several events where the fragile dummy loads inside the high field side directional couplers were damaged, due to excessive power resulting from the ECRH stray fields. In this paper, we present a non-conventional application of the existing three-port directional coupler that hardens the system to the ECRH stray fields and at the same time generates the necessary reference signal. Electromagnetic simulations and laboratory tests were performed to validate the proposed solution and are compared with the in-vessel calibration tests.

  13. Numerical modeling of heat transfer and fluid flow in laser metal deposition by powder injection

    NASA Astrophysics Data System (ADS)

    Fan, Zhiqiang

    Laser metal deposition is an additive manufacturing technique which allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. A self-consistent three-dimensional model was developed for the laser metal deposition process by powder injection, which simulates heat transfer, phase changes, and fluid flow in the melt pool. The governing equations for solid, liquid and gas phases in the calculation domain have been formulated using the continuum model. The free surface in the melt pool has been tracked by the Volume of Fluid (VOF) method, while the VOF transport equation was solved using the Piecewise Linear Interface Calculation (PLIC) method. Surface tension was modeled by taking the Continuum Surface Force (CSF) model combined with a force-balance flow algorithm. Laser-powder interaction was modeled to account for the effects of laser power attenuation and powder temperature rise during the laser metal deposition process. The governing equations were discretized in the physical space using the finite volume method. The advection terms were approximated using the MUSCL flux limiter scheme. The fluid flow and energy equations were solved in a coupled manner. The incompressible flow equations were solved using a two-step projection method, which requires a solution of a Poisson equation for the pressure field. The discretized pressure Poisson equation was solved using the ICCG (Incomplete Cholesky Conjugate Gradient) solution technique. The energy equation was solved by an enthalpy-based method. Temperature-dependent thermal-physical material properties were considered in the numerical implementation. The numerical model was validated by comparing simulations with experimental measurements.

  14. Conceptual design of a laser-fusion power plant. Part II. Two technical options: 1. JADE reactor; 2. Heat transfer by heat pipes

    SciTech Connect

    Not Available

    1981-07-01

    A laser fusion reactor concept is described that employs liquid metal walls. The concept envisions a porous medium, called the JADE, of specific geometry lining the reactor cavity. Some advantages and disadvantages of the concept are pointed out. The possibility of using heat pipes for passive cooling in ICF reactors is discussed. Some of the problems are outlined. (MOW)

  15. Intermittent cryogen spray cooling for optimal heat extraction during dermatologic laser treatment.

    PubMed

    Majaron, Boris; Svaasand, Lars O; Aguilar, Guillermo; Nelson, J Stuart

    2002-09-21

    Fast heat extraction is critically important to obtain the maximal benefit of cryogen spray cooling (CSC) during laser therapy of shallow skin lesions, such as port wine stain birthmarks. However, a film of liquid cryogen can build up on the skin surface, impairing heat transfer due to the relatively low thermal conductivity and higher temperature of the film as compared to the impinging spray droplets. In an attempt to optimize the cryogen mass flux, while minimally affecting other spray characteristics, we apply a series of 10 ms spurts with variable duty cycles. Heat extraction dynamics during such intermittent cryogen sprays were measured using a custom-made metal-disc detector. The highest cooling rates were observed at moderate duty cycle levels. This confirms the presence, and offers a practical way to eliminate the adverse effect of liquid cryogen build-up on the sprayed surface. On the other hand, lower duty cycles allow a substantial reduction in the average rate of heat extraction, enabling less aggressive and more efficient CSC for treatment of deeper targets, such as hair follicles.

  16. Specific heat treatment of selective laser melted Ti-6Al-4V for biomedical applications

    NASA Astrophysics Data System (ADS)

    Huang, Qianli; Liu, Xujie; Yang, Xing; Zhang, Ranran; Shen, Zhijian; Feng, Qingling

    2015-12-01

    The ductility of as-fabricated Ti-6Al-4V falls far short of the requirements for biomedical titanium alloy implants and the heat treatment remains the only applicable option for improvement of their mechanical properties. In the present study, the decomposition of as-fabricated martensite was investigated to provide a general understanding on the kinetics of its phase transformation. The decomposition of asfabricated martensite was found to be slower than that of water-quenched martensite. It indicates that specific heat treatment strategy is needed to be explored for as-fabricated Ti-6Al-4V. Three strategies of heat treatment were proposed based on different phase transformation mechanisms and classified as subtransus treatment, supersolvus treatment and mixed treatment. These specific heat treatments were conducted on selective laser melted samples to investigate the evolutions of microstructure and mechanical properties. The subtransus treatment leaded to a basket-weave structure without changing the morphology of columnar prior β grains. The supersolvus treatment resulted in a lamellar structure and equiaxed β grains. The mixed treatment yielded a microstructure that combines both features of the subtransus treatment and supersolvus treatment. The subtransus treatment is found to be the best choice among these three strategies for as-fabricated Ti-6Al-4V to be used as biomedical implants.

  17. Intermittent cryogen spray cooling for optimal heat extraction during dermatologic laser treatment

    NASA Astrophysics Data System (ADS)

    Majaron, Boris; Svaasand, Lars O.; Aguilar, Guillermo; Nelson, J. Stuart

    2002-09-01

    Fast heat extraction is critically important to obtain the maximal benefit of cryogen spray cooling (CSC) during laser therapy of shallow skin lesions, such as port wine stain birthmarks. However, a film of liquid cryogen can build up on the skin surface, impairing heat transfer due to the relatively low thermal conductivity and higher temperature of the film as compared to the impinging spray droplets. In an attempt to optimize the cryogen mass flux, while minimally affecting other spray characteristics, we apply a series of 10 ms spurts with variable duty cycles. Heat extraction dynamics during such intermittent cryogen sprays were measured using a custom-made metal-disc detector. The highest cooling rates were observed at moderate duty cycle levels. This confirms the presence, and offers a practical way to eliminate the adverse effect of liquid cryogen build-up on the sprayed surface. On the other hand, lower duty cycles allow a substantial reduction in the average rate of heat extraction, enabling less aggressive and more efficient CSC for treatment of deeper targets, such as hair follicles.

  18. The heat-pipe resembling action of boiling bubbles in endovenous laser ablation

    PubMed Central

    van den Bos, Renate R.; van Ruijven, Peter W. M.; Nijsten, Tamar; Neumann, H. A. Martino; van Gemert, Martin J. C.

    2010-01-01

    Endovenous laser ablation (EVLA) produces boiling bubbles emerging from pores within the hot fiber tip and traveling over a distal length of about 20 mm before condensing. This evaporation-condensation mechanism makes the vein act like a heat pipe, where very efficient heat transport maintains a constant temperature, the saturation temperature of 100°C, over the volume where these non-condensing bubbles exist. During EVLA the above-mentioned observations indicate that a venous cylindrical volume with a length of about 20 mm is kept at 100°C. Pullback velocities of a few mm/s then cause at least the upper part of the treated vein wall to remain close to 100°C for a time sufficient to cause irreversible injury. In conclusion, we propose that the mechanism of action of boiling bubbles during EVLA is an efficient heat-pipe resembling way of heating of the vein wall. PMID:20644976

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

    NASA Astrophysics Data System (ADS)

    Colvin, J. D.; Pérez, F.; Fournier, K. B.; May, M. J.; Felter, T. E.; Bagge-Hansen, M.; Kucheyev, S.

    2014-10-01

    We showed earlier that the laser-driven heat front propagation velocity in low-density Ti-silica aerogel and TiO2 foam targets was slower than that simulated with a 2D radiation-hydrodynamics code incorporating an atomic kinetics model in non-LTE and assuming initially homogeneous material (F. Pérez et al., Physics of Plasmas 21, 023102 (2014)). Some theoretical models suggest that the heat front is slowed over what it would be in a homogeneous medium by the microstructure of the foam. In more recent experiments with Cu-loaded carbon nanotube foam, however, we find the opposite behavior; that is, the simulations under-predict the measured heat-front velocity. We present details of the Cu foam experiments and comparisons with simulations, and then discuss implications for models of heat-front slowing in foams of a more-recent gas vs. foam comparison experiment. F. Pérez presents the design and results of this comparison experiment in a companion presentation. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract No. DE-AC52-07NA27344, with partial support from a DTRA Basic Research grant.

  20. Strategies for in situ laser heating in the diamond anvil cell at an X-ray diffraction beamline

    PubMed Central

    Petitgirard, Sylvain; Salamat, Ashkan; Beck, Pierre; Weck, Gunnar; Bouvier, Pierre

    2014-01-01

    An overview of several innovations regarding in situ laser-heating techniques in the diamond anvil cell at the high-pressure beamline ID27 of the European Synchrotron Radiation Facility is presented. Pyrometry measurements have been adapted to allow simultaneous double-sided temperature measurements with the installation of two additional online laser systems: a CO2 and a pulsed Nd:YAG laser system. This reiteration of laser-heating advancements at ID27 is designed to pave the way for a new generation of state-of-the-art experiments that demand the need for synchrotron diffraction techniques. Experimental examples are provided for each major development. The capabilities of the double pyrometer have been tested with the Nd:YAG continuous-wave lasers but also in a time-resolved configuration using the nanosecond-pulsed Nd:YAG laser on a Fe sample up to 180 GPa and 2900 K. The combination of time-resolved X-ray diffraction with in situ CO2 laser heating is shown with the crystallization of a high-pressure phase of the naturally found pyrite mineral MnS2 (11 GPa, 1100–1650 K). PMID:24365921

  1. Propogation of the 1(mu) High-Power Beam from a Solid-State Heat-Capacity Laser

    SciTech Connect

    Dane, C B; Moriss, J R; Rubenchik, A M; Boley, C D

    2002-06-25

    A solid-state laser system, used as a directed energy defensive weapon, possesses many compelling logistical advantages over high-average-power chemical laser systems. As an electrically-powered laser, it uses no chemicals, generates no effluents, and requires no specialized logistics support--the laser is recharged by running the vehicle engine. It provides stealth, having low signature operation without the generation of temperature, smoke, or visible light. It is silent in operation, limited only by the onboard vehicle electrical charging and propulsion system. Using the heat-capacity mode of operation, scaling of average power from a solid-state laser has been demonstrated beyond 10kW and work in progress will result in the demonstration of a 100 kW solid-state heat-capacity laser (SSHCL). The heat-capacity approach provides unprecedented power-to-weight ratios in a compact platform that is readily adapted to mobile operation. A conceptual engineering and packaging study has resulted in a 100kW SSHCL design that we believe can be integrated onto a hybrid-electric HMMWV or onto new vehicle designs emerging from the future combat system (FCS) development. 100 kW has been proposed as a power level that demonstrates a significant scaling beyond what has been demonstrated for a solid-state laser system and which could have a significant lethality against target sets of interest. However, the characteristics of heat-capacity laser scaling are such that designs with output powers in excess of 1 MW can be readily formulated. An important question when addressing the military utility of a high-power solid-state laser system is that of the required average power during engagement with a target. The answer to this question is complex, involving atmospheric propagation, beam interaction with the target, and the damage response of the target. Successful target shoot-downs with the THEL deuterium fluoride (DF) laser system provide what is probably the best understanding of

  2. Temperature distribution and modification mechanism inside glass with heat accumulation during 250 kHz irradiation of femtosecond laser pulses

    SciTech Connect

    Sakakura, Masaaki; Shimotsuma, Yasuhiko; Shimizu, Masahiro; Miura, Kiyotaka; Hirao, Kazuyuki

    2008-12-08

    Heat accumulation by high repetition rate femtosecond laser irradiation inside glass generates a much larger modification than that by a single pulse. In this study, we determined the temperature distribution due to heat accumulation and the characteristic temperature for heat modification inside a soda lime glass by analyzing the relationship between the radius of modification and glass temperature. The validity of the analysis was confirmed by reproducing the modification due to two-beam irradiation. The determined characteristic temperature suggested that the temperature distribution and the spatial dependence of the stress relaxation are important in the mechanism of heat modification.

  3. Isochoric heating of solids by laser-accelerated protons: Experimental characterization and self-consistent hydrodynamic modeling

    NASA Astrophysics Data System (ADS)

    Mancic, A.; Robiche, J.; Antici, P.; Audebert, P.; Blancard, C.; Combis, P.; Dorchies, F.; Faussurier, G.; Fourmaux, S.; Harmand, M.; Kodama, R.; Lancia, L.; Mazevet, S.; Nakatsutsumi, M.; Peyrusse, O.; Recoules, V.; Renaudin, P.; Shepherd, R.; Fuchs, J.

    2010-01-01

    A study of isochoric heating of Al foil by laser-accelerated proton beam is presented, coupling self-consistent hydrodynamic simulations (including proton stopping) with experimental measurements. The proton source that induces the heating has been characterized experimentally and the induced heating has been inferred through critical density expansion velocity measurement. The low-energy part of the proton spectrum that plays the dominant part in the heating process has been studied in detail. The experimental results are compared with the results of 1-dimensional hydrodynamic simulations that use as input the measured proton source and good agreement between the two is found using the SESAME EOS.

  4. Measurement of laser heating in spin exchange optical pumping by NMR diffusion sensitization gradients

    SciTech Connect

    Parnell, Steven R.; Deppe, Martin H.; Ajraoui, Salma; Parra-Robles, Juan; Wild, Jim M.; Boag, Stephen

    2010-05-15

    This paper details pulsed gradient NMR measurements of the {sup 3}He diffusion coefficient in sealed cells during spin exchange optical pumping. The potential of ultra low field magnetic resonance imgaing (MRI) and NMR for noninvasive measurement of cell pressure is demonstrated. Diffusion sensitization gradients allow measurement of the {sup 3}He diffusion coefficient from which the pressure and/or temperature of the gas can be determined during optical pumping. The pressure measurements were compared with neutron time of flight transmission measurements. Good agreement was observed between the temperature/pressure measurements and predictions based on Chapman-Enskog theory. The technique had sufficient sensitivity to observe the diffusion coefficient increasing with temperature in a sealed cell. With this method, evidence for laser heating of the {sup 3}He during optical pumping was found. The results show that NMR diffusion measurements allow noninvasive measurement of the cell temperature and/or pressure in an optical pumping setup. The method can be expanded using MRI to probe the spatial distribution of the diffusion coefficient. These techniques can be applied to the further investigation of polarization limiting effects such as laser heating.

  5. Reversible Electron Beam Heating for Suppression of Microbunching Instabilities at Free-Electron Lasers

    SciTech Connect

    Behrens, Christopher; Huang, Zhirong; Xiang, Dao; /SLAC

    2012-05-30

    The presence of microbunching instabilities due to the compression of high-brightness electron beams at existing and future x-ray free-electron lasers (FELs) results in restrictions on the attainable lasing performance and renders beam imaging with optical transition radiation impossible. The instability can be suppressed by introducing additional energy spread, i.e., heating the electron beam, as demonstrated by the successful operation of the laser heater system at the Linac Coherent Light Source. The increased energy spread is typically tolerable for self-amplified spontaneous emission FELs but limits the effectiveness of advanced FEL schemes such as seeding. In this paper, we present a reversible electron beam heating system based on two transverse deflecting radio-frequency structures (TDSs) upstream and downstream of a magnetic bunch compressor chicane. The additional energy spread is introduced in the first TDS, which suppresses the microbunching instability, and then is eliminated in the second TDS. We show the feasibility of the microbunching gain suppression based on calculations and simulations including the effects of coherent synchrotron radiation. Acceptable electron beam and radio-frequency jitter are identified, and inherent options for diagnostics and on-line monitoring of the electron beam's longitudinal phase space are discussed.

  6. Modeling Antimortar Lethality by a Solid-State Heat-Capacity Laser

    SciTech Connect

    Boley, C D; Rubenchik, A M

    2005-02-15

    We have studied the use of a solid-state heat-capacity laser (SSHCL) in mortar defense. This type of laser, as built at LLNL, produces high-energy pulses with a wavelength of about 1 {micro}m and a pulse repetition rate of 200 Hz. Currently, the average power is about 26 kW. Our model of target interactions includes optical absorption, two-dimensional heat transport in the metal casing and explosive, melting, wind effects (cooling and melt removal), high-explosive reactions, and mortar rotation. The simulations continue until HE initiation is reached. We first calculate the initiation time for a range of powers on target and spot sizes. Then we consider an engagement geometry in which a mortar is fired at an asset defended by a 100-kW SSHCL. Propagation effects such as diffraction, turbulent broadening, scattering, and absorption are calculated for points on the trajectory, by means of a validated model. We obtain kill times and fluences, as functions of the rotation rate. These appear quite feasible.

  7. Local heating as a predilatation method for measurement of vasoconstrictor responses with laser-Doppler flowmetry.

    PubMed

    Henricson, Joakim; Tesselaar, Erik; Baiat, Yashma; Nilsson, Gert; Sjöberg, Folke

    2011-04-01

    Studying microvascular responses to iontophoresis of vasoconstricting drugs contributes to a better understanding of the regulatory mechanisms of cutaneous vessels, but measuring these responses with laser-Doppler flowmetry at basal blood flow conditions is technically challenging. This study aimed to investigate whether the measurement of cutaneous vasoconstrictor responses to noradrenaline (NA) and phenylephrine (PE), delivered by iontophoresis, is facilitated by predilatation of the microvascular bed using local heating. We used different drug delivery rates (100 s × 0.12 mA, 200 s × 0.06 mA, 300 s × 0.04 mA) to investigate whether predilatation affects the local drug dynamics by an increased removal of drugs from the skin. In a predilatated vascular bed, iontophoresis of NA and PE resulted in a significant decrease in perfusion from the thermal plateau (p < 0.001). The decrease was 25-33%, depending on drug delivery rate. In unheated skin, a significant vasoconstriction was observed (p < 0.001), with 17% and 14% decrease from baseline for NA and PE, respectively. These results indicate that predilatating the cutaneous vascular bed by local heating facilitates measurement of vasoconstriction with laser-Doppler flowmetry and does not seem to significantly affect the result by an increased removal of drugs from the skin.

  8. Laser selective cutting of biological tissues by impulsive heat deposition through ultrafast vibrational excitations.

    PubMed

    Franjic, Kresimir; Cowan, Michael L; Kraemer, Darren; Miller, R J Dwayne

    2009-12-07

    Mechanical and thermodynamic responses of biomaterials after impulsive heat deposition through vibrational excitations (IHDVE) are investigated and discussed. Specifically, we demonstrate highly efficient ablation of healthy tooth enamel using 55 ps infrared laser pulses tuned to the vibrational transition of interstitial water and hydroxyapatite around 2.95 microm. The peak intensity at 13 GW/cm(2) was well below the plasma generation threshold and the applied fluence 0.75 J/cm(2) was significantly smaller than the typical ablation thresholds observed with nanosecond and microsecond pulses from Er:YAG lasers operating at the same wavelength. The ablation was performed without adding any superficial water layer at the enamel surface. The total energy deposited per ablated volume was several times smaller than previously reported for non-resonant ultrafast plasma driven ablation with similar pulse durations. No micro-cracking of the ablated surface was observed with a scanning electron microscope. The highly efficient ablation is attributed to an enhanced photomechanical effect due to ultrafast vibrational relaxation into heat and the scattering of powerful ultrafast acoustic transients with random phases off the mesoscopic heterogeneous tissue structures.

  9. Carbon ion beam focusing using laser irradiated heated diamond hemispherical shells

    SciTech Connect

    Offermann, Dustin T; Flippo, Kirk A; Gaillard, Sandrine A

    2009-01-01

    Experiments preformed at the Los Alamos National Laboratory's Trident Laser Facility were conducted to observe the acceleration and focusing of carbon ions via the TNSA mechanism using hemispherical diamond targets. Trident is a 200TW class laser system with 80J of 1 {micro}m, short-pulse light delivered in 0.5ps, with a peak intensity of 5 x 10{sup 20} W/cm{sup 2}. Targets where Chemical Vapor Deposition (CVD) diamonds formed into hemispheres with a radius of curvature of 400{micro}m and a thickness of 5{micro}m. The accelerated ions from the hemisphere were diagnosed by imaging the shadow of a witness copper mesh grid located 2mm behind the target onto a film pack located 5cm behind the target. Ray tracing was used to determine the location of the ion focal spot. The TNSA mechanism favorably accelerates hydrogen found in and on the targets. To make the carbon beam detectable, targets were first heated to several hundred degrees Celsius using a CW, 532nm, 8W laser. Imaging of the carbon beam was accomplished via an auto-radiograph of a nuclear activated lithium fluoride window in the first layer of the film pack. The focus of the carbon ion beam was determined to be located 630 {+-} 110 {micro}m from the vertex of the hemisphere.

  10. Determination of the conditions of boronizing steel with heating by laser radiation

    SciTech Connect

    Lyakhovich, L.S.; Isakov, S.A.; Kartoshkin, V.M.; Pakhadnya, V.P.

    1986-05-01

    The purpose of the authors' investigations is to determine the conditions of obtaining boride coatings on steels heated by laser radiation. The investigations were carried out on an experimental installation containing a continuous-wave CO/sub 2/ laser with a power of up to 800 W (wavelength 10.6 mu m), a device for gripping and shifting the specimens with specified speed, focusing lens of KC1 with focal length 223 mm. It was determined that a boride layer of high quality, 80-120 mu m thick, is attained with a power density of the laser radiation on the surface of steel 45 equal to 0.4 GW/m/sup 2/ and a speed of shifting the specimen of 6-8 mm/sec. Basically, the boride layer consists of the phases Fe/sub 2/B and FeB. The structure and phase composition of the boride layer are predominantly affected by the thickness of the layer of amorphous boron applied to the surface of the specimen.

  11. All-optical fiber anemometer based on laser heated fiber Bragg gratings.

    PubMed

    Gao, Shaorui; Zhang, A Ping; Tam, Hwa-Yaw; Cho, L H; Lu, Chao

    2011-05-23

    A fiber-optic anemometer based on fiber Bragg gratings (FBGs) is presented. A short section of cobalt-doped fiber was utilized to make a fiber-based "hot wire" for wind speed measurement. Fiber Bragg gratings (FBGs) were fabricated in the cobalt-doped fiber using 193 nm laser pulses to serve as localized temperature sensors. A miniature all-optical fiber anemometer is constructed by using two FBGs to determine the dynamic thermal equilibrium between the laser heating and air flow cooling through monitoring the FBGs' central wavelengths. It was demonstrated that the sensitivity of the sensor can be adjusted through the power of pump laser or the coating on the FBG. Experimental results reveal that the proposed FBG-based anemometer exhibits very good performance for wind speed measurement. The resolution of the FBG-based anemometer is about 0.012 m/s for wind speed range between 2.0 m/s and 8.0 m/s.

  12. Intracavity, adaptive correction of a high-average-power, solid-state, heat-capacity laser

    SciTech Connect

    LaFortune, K N; Hurd, R L; Brase, J M; Yamamoto, R M

    2005-01-05

    The Solid-State, Heat-Capacity Laser (SSHCL) program at Lawrence Livermore National Laboratory is a multigeneration laser development effort scalable to the megawatt power levels. Wavefront quality is a driving metric of its performance. A deformable mirror with over 100 degrees of freedom situated within the cavity is used to correct both the static and dynamic aberrations sensed with a Shack-Hartmann wavefront sensor. The laser geometry is an unstable, confocal resonator with a clear aperture of 10 cm x 10 cm. It operates in a pulsed mode at a high repetition rate (up to 200 Hz) with a correction being applied before each pulse. Wavefront information is gathered in real-time from a low-power pick-off of the high-power beam. It is combined with historical trends of aberration growth to calculate a correction that is both feedback and feed-forward driven. The overall system design, measurement techniques and correction algorithms are discussed. Experimental results are presented.

  13. Absorption coefficient measurements of particle-laden filters using laser heating: Validation with nigrosin

    NASA Astrophysics Data System (ADS)

    Presser, Cary

    2012-05-01

    A laser-heating technique, referred as the laser-driven thermal reactor, was used in conjunction with laser transmissivity measurements to determine the absorption coefficient of particle-laden substrates (e.g., quartz-fiber filters). The novelty of this approach is that it analyzes a wide variety of specific samples (not just filtered samples) and overcomes measurement issues (e.g., absorption enhancement) associated with other filter-based particle absorption techniques. The absorption coefficient was determined for nigrosin-laden, quartz-fiber filters and the effect of the filter on the absorption measurements was estimated when compared to the isolated nigrosin results. The isolated nigrosin absorption coefficient compared favorably with Lorenz-Mie calculations for an idealized polydispersion of spherical particles (based on a measured nigronsin/de-ionized water suspension size distribution) dispersed throughout a volume equivalent to that of the nigrosin-laden filter. To validate the approach, the absorption coefficient of a nigrosin/de-ionized water suspension was in good agreement with results obtained from an ultraviolet/visible spectrometer. In addition, the estimated imaginary part of the refractive index from the Lorenz-Mie calculations compared well with literature values and was used to estimate the absorption coefficient of optically opaque packed nigrosin.

  14. A virtual experiment control and data acquisition system for in situ laser heated diamond anvil cell Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Subramanian, N.; Struzhkin, Viktor V.; Goncharov, Alexander F.; Hemley, Russell J.

    2010-09-01

    Doubled-sided laser heated diamond anvil cell methods allow simultaneous in situ confocal Raman measurements of materials up to megabar pressures and high temperatures. This paper describes a virtual control and data acquisition system developed to automate setups for simultaneous Raman/laser heating experiments. The system enables reduction of experiment time by ˜90% in comparison to manual operations, allowing measurements of high quality Raman spectra of even highly reactive or diffusive samples, such as hydrogen at extreme conditions using continuous wave laser heating. These types of measurements are very difficult and often impossible to obtain in a manual operation mode. Complete data archiving and accurate control of various experimental parameters (e.g., on-the-fly temperature determination and self-adjusting data collection time to avoid signal saturation) can be done, and open up possibilities of other types of experiments involving extreme conditions.

  15. Experimental study on heat transmission to the vestibule during CO2 laser use in revision stapes surgery.

    PubMed

    Szymański, M; Morshed, K; Mills, R

    2007-01-01

    We studied the transmission of heat to the vestibule during revision stapes surgery with a piston in situ, using a CO2 laser, in an in vitro model. A type K thermocouple was placed around the medial end of stainless steel and fluoroplastic wire pistons in a 'vestibule' filled with saline. The effect of laser hits on fluoroplastic wire and stainless steel stapes prostheses was investigated. The effect of introducing a vein graft to seal the stapedotomy was also examined. Greater temperature rises occurred with stainless steel than with fluoroplastic wire pistons. The addition of the vein graft reduced heat transmission. Application of the CO2 laser to fluoroplastic wire pistons, using the power settings suggested by the manufacturer, is not likely to damage the inner-ear structures. Application of 6 W laser energy to stainless steel pistons can potentially disturb the inner-ear function.

  16. Time-Domain X-ray Diffraction in the Pulsed Laser Heated Diamond Anvil Cell

    NASA Astrophysics Data System (ADS)

    Prakapenka, V.; Goncharov, A. F.; Struzhkin, V.; Kantor, I.; Rivers, M. L.; Dalton, D. A.

    2011-12-01

    We have developed in situ x-ray synchrotron diffraction measurements of samples heated by a pulsed laser in the diamond anvil cell (DAC) at pressure up to 100 GPa and 3500 K. We used an electronically modulated 2-10 kHz repetition rate, 1064-1075 nm fiber laser with 1-100 microseconds pulse width synchronized with a gated x-ray detector (Pilatus) and time resolved radiometric temperature measurements. For the special APS hybrid mode, the measurements were also synchronized with a 500 ns long bunch carrying 88% of the ring current. This setup enables time domain measurements as a function of temperature in a micrometers time scale (averaged over many events, typically more than 10,000). X-ray diffraction data, temperature measurements, and finite element calculations with realistic geometric and thermochemical parameters show that in the present experimental configuration samples 4 micrometers thick can be continuously temperature monitored (up to 3000 K in our experiments) with the same level of axial and radial temperature uniformity as with continuous heating. We find that this novel technique offers a new and convenient way of fine tuning the maximum sample temperature by changing the pulse width of the laser. We will show examples of studies of the melting, thermal equation of state, and chemical reactivity. We acknowledge support from NSF EAR-0842057, DOE/ NNSA (CDAC), and EFree, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award No. DESC0001057. X-ray diffraction measurements were performed at GSECARS (APS) supported by DOE Contract No.W-31-109- Eng-38.

  17. Second generation laser-heated microfurnace for the preparation of microgram-sized graphite samples

    NASA Astrophysics Data System (ADS)

    Yang, Bin; Smith, A. M.; Long, S.

    2015-10-01

    We present construction details and test results for two second-generation laser-heated microfurnaces (LHF-II) used to prepare graphite samples for Accelerator Mass Spectrometry (AMS) at ANSTO. Based on systematic studies aimed at optimising the performance of our prototype laser-heated microfurnace (LHF-I) (Smith et al., 2007 [1]; Smith et al., 2010 [2,3]; Yang et al., 2014 [4]), we have designed the LHF-II to have the following features: (i) it has a small reactor volume of 0.25 mL allowing us to completely graphitise carbon dioxide samples containing as little as 2 μg of C, (ii) it can operate over a large pressure range (0-3 bar) and so has the capacity to graphitise CO2 samples containing up to 100 μg of C; (iii) it is compact, with three valves integrated into the microfurnace body, (iv) it is compatible with our new miniaturised conventional graphitisation furnaces (MCF), also designed for small samples, and shares a common vacuum system. Early tests have shown that the extraneous carbon added during graphitisation in each LHF-II is of the order of 0.05 μg, assuming 100 pMC activity, similar to that of the prototype unit. We use a 'budget' fibre packaged array for the diode laser with custom built focusing optics. The use of a new infrared (IR) thermometer with a short focal length has allowed us to decrease the height of the light-proof safety enclosure. These innovations have produced a cheaper and more compact device. As with the LHF-I, feedback control of the catalyst temperature and logging of the reaction parameters is managed by a LabVIEW interface.

  18. Creating metallic under-dense radiators by electron beam heating prior to laser impact

    SciTech Connect

    Garcia, M

    1998-12-15

    A pulsed, relativistic electron beam can heat a metal foil to a plasma state, and initiate an expanding flow into vacuum. At a given time in its evolution, this flow fills a nearly spherical volume with nearly uniform density, assuming a rapid expansion prior to any condensation. A metal cloud produced in this way can serve as a target of intense laser illumination to create an under-dense radiator of x-rays. The phrase ''under-dense radiator'' means that the cloud, assumed ionized, has a plasma density that is less than the critical density for the wavelength of the laser light. The example described here is of a 2 {micro}g copper foil 23 {micro}m thick and 0.16 mm in diameter, heated by 8 mJ of electron beam energy in as short a time as possible, perhaps under 50 ns. The electron beam pulse must be at least 140 nC at 100 keV in order to transit the foil and deposit 8 mJ. A 50 ns pulse focused on the target would have a current of 2.8 A, and a current density of 14 kA/cm{sup 2}. The initial plasma temperature is 0.5 eV. After 300 ns, the flow has expanded to fill a nearly spherical volume of 1 mm diameter, with a nearly uniform copper density of 1.5 x 10{sup 20} cm{sup {minus}3}. The leading edge of the cloud is expanding at 1700 m/s, while flow at the original position of the foil surface expands at 150 m/s. This cloud is nearly stationary during the short time of a laser pulse at the National Ignition Facility (NIF).

  19. Impact of heat on metabolic and hemodynamic changes in transcranial infrared laser stimulation measured by broadband near-infrared spectroscopy.

    PubMed

    Wang, Xinlong; Reddy, Divya D; Nalawade, Sahil S; Pal, Suvra; Gonzalez-Lima, F; Liu, Hanli

    2018-01-01

    Transcranial infrared laser stimulation (TILS) has shown effectiveness in improving human cognition and was investigated using broadband near-infrared spectroscopy (bb-NIRS) in our previous study, but the effect of laser heating on the actual bb-NIRS measurements was not investigated. To address this potential confounding factor, 11 human participants were studied. First, we measured time-dependent temperature increases on forehead skin using clinical-grade thermometers following the TILS experimental protocol used in our previous study. Second, a subject-averaged, time-dependent temperature alteration curve was obtained, based on which a heat generator was controlled to induce the same temperature increase at the same forehead location that TILS was delivered on each participant. Third, the same bb-NIRS system was employed to monitor hemodynamic and metabolic changes of forehead tissue near the thermal stimulation site before, during, and after the heat stimulation. The results showed that cytochrome-c-oxidase of forehead tissue was not significantly modified by this heat stimulation. Significant differences in oxyhemoglobin, total hemoglobin, and differential hemoglobin concentrations were observed during the heat stimulation period versus the laser stimulation. The study demonstrated a transient hemodynamic effect of heat-based stimulation distinct to that of TILS. We concluded that the observed effects of TILS on cerebral hemodynamics and metabolism are not induced by heating the skin.

  20. Dynamics of bulk electron heating and ionization in solid density plasmas driven by ultra-short relativistic laser pulses

    SciTech Connect

    Huang, L. G. Kluge, T.; Cowan, T. E.

    2016-06-15

    The dynamics of bulk heating and ionization is investigated both in simulations and theory, which determines the crucial plasma parameters such as plasma temperature and density in ultra-short relativistic laser-solid target interactions. During laser-plasma interactions, the solid density plasma absorbs a fraction of laser energy and converts it into kinetic energy of electrons. A portion of the electrons with relativistic kinetic energy goes through the solid density plasma and transfers energy into the bulk electrons, which results in bulk electron heating. The bulk electron heating is finally translated into the processes of bulk collisional ionization inside the solid target. A simple model based on the Ohmic heating mechanism indicates that the local and temporal profile of bulk return current is essential to determine the temporal evolution of bulk electron temperature. A series of particle-in-cell simulations showing the local heating model is robust in the cases of target with a preplasma and without a preplasma. Predicting the bulk electron heating is then benefit for understanding the collisional ionization dynamics inside the solid targets. The connection of the heating and ionization inside the solid target is further studied using Thomas-Fermi model.