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- Commercial Applications of Lasers and E-beams
- Modification of Materials and Surfaces
- Pulse Power for Lasers and Accelerators
- Environmental Related Technologies
- Environmental Related Technologies: Fluids and Solids
- Dual-Use Application of Lasers: Manufacturing
- Dual-Use Applications of Lasers: LIDAR
- Dual-Use Applications of Lasers: Medical
Commercial Applications of Lasers and E-beams
Application of lasers and pulsed power to coating removal
Chris M. Young,
William M. Moeny,
Randy D. Curry,
et al.
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Lasers and other pulsed power systems are uniquely suited for removal of coatings from a wide variety of substrates. Coatings which can be removed by these systems include paint, adhesives, epoxies, dips, rust, scale, and bird droppings. Suitable substrates include wood, metal, cloth, stone, ceramic, plastics, and even skin. These systems have the advantage over chemical stripping or mechanical abrasion in that the substrate is left virtually unharmed and in many cases the residue is reduced to a form that is more easily disposed of without toxic byproducts or expensive refurbishment. Furthermore, laser and other pulsed power based systems can be operated using only local containment without the need for special operator protective gear or complete enclosure of the substrate structure. Additional advantages are gained in these systems because they typically combine multiple removal mechanisms for greater effectiveness. For example, pulsed lasers create rapid heating of the coating. This rapid heating can result in chemical breakdown of the coating, thermomechanical stress induced dislocation, shock wave agitation, and physical ablation. This paper presents some of the latest research findings on coating removal using these systems. A comparative survey of the system technology, effectiveness, cost, and application is presented. Also presented is a survey of the commercial potential for the systems. Systems which are presented include lasers (CW, pulsed, Infrared, UV, etc.), flashlamps, electro-cathodic debonders, electron beams, and glow discharges.
High-energy electron beams for ceramic joining
Bob N. Turman,
S. J. Glass,
J. A. Halbleib,
et al.
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Joining of structural ceramics is possible using high melting point metals such as Mo and Pt that are heated with a high energy electron beam, with the potential for high temperature joining. A 10 MeV electron beam can penetrate through 1 cm of ceramic, offering the possibility of buried interface joining. Because of transient heating and the lower heat capacity of the metal relative to the ceramic, a pulsed high power beam has the potential for melting the metal without decomposing or melting the ceramic. We have demonstrated the feasibility of the process with a series of 10 MeV, 1 kW electron beam experiments. Shear strengths up to 28 MPa have been measured. This strength is comparable to that reported in the literature for bonding silicon nitride (Si3N4) to molybdenum with copper-silver-titanium braze, but weaker than that reported for Si3N4 - Si3N4 with gold-nickel braze. The bonding mechanism appears to be formation of a thin silicide layer. Beam damage to the Si3N4 was also assessed.
Laser curing of thermosetting powder coatings
Lala Abhinandan,
Manoj Kumar,
M. K. Trivedi,
et al.
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In this paper, we report the curing of therrnosetting powder coating with CO2 laser radiation as a substitute for conventional oven curing. The main advantages of this process are rapid curing, negligible heating of the substrate and extremely versatile processing to suit curing of different powders.
Marble cutting with cw CO2 laser
Manoj Kumar,
A. K. Biswas,
K. Srinivas,
et al.
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In this paper we present results of marble cutting with high power CO2 laser. The dependence of various parameters such as thickness of marble, laser power, cutting speed, assist gas and its pressure on cutting process was studied. Structural properties of marble like crystal size have been found to affect the cut quality. The average severance energy (P/vt, P = laser power, v = cutting speed, t = thickness) for marble was approximately found to be 9.0 J/mm2. This agrees very closely with the calculated value based on energy balance.
Selective laser photolysis of organic molecules in complex matrices
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Natural extracts or essences are largely used in several fields (farm- produce industry, cosmetic, perfumery, biochemistry, etc.). However, most of these complex extracts contain also toxic, carcinogenic or non desirable molecules. By using a laser directly tuned to an absorption band of the unwanted molecules, selective elimination is obtained. Advantages of this procedure are the rapidity, in situ reaction and the possibility to perform quantitative elimination. Examples such as the destruction of thujone in extract of Salvia, bergaptene in essence of Bergamote, phycocyanin in Porphyridium Cruentum or simply dye will be presented and discussed.
Modification of Materials and Surfaces
Surface modification of polymers using excimer lasers and short-pulse flashlamps
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Exposure of oriented, semicrystalline polymers, such as poly(ethylene terephthalate), poly(ethylene naphthalate) and polyimides, to the output of pulsed light sources, such as excimer lasers or short pulse flashlamps, at energy densities less than the ablation threshold can produce an amorphous layer on the polymer surfaces. Time resolved spectroscopy has shown that this amorphous layer is produced by a transient heating of the surface region to temperatures exceeding the polymer melting point (300-500 degree(s)C) resulting in rapid melting and the production of the thin disordered surface layer. Static SIMS, XPS, and infrared spectroscopy measurements have shown that this surface amorphization occurs without any decomposition or crosslinking of the polymer surface. The amorphous layers produced by this rapid thermal process provide increased adhesion of a wide range of coatings and films to the treated polymers due to the increased fracture toughness of their disordered morphology. The amorphous surface layer also can antireflect the polymers, provide increased autoadhesion, and increase coating penetration into the treated polymer substrates. This last characteristic can be exploited to provide photoimaging properties, as negative photoresists, to polyimides. The rapid thermal surface modification technology shows potential for economic industrial implementation, using short pulse flashlamps, provided that reliable, large-scale flashlamp systems can be made available.
Use of pulsed e-beams for the initiation of spectral luminescence in solids
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The work is devoted to the pulsed cathodoluminescence (PCL) of solids that occurs upon irradiating them later by high-current pulsed e-beams. The parameters of e-beams that cause no irreversible disintegration in the material under investigation are given. The conclusion has been made that PCL can be used in a spectral-emission analysis of solids being single-piece structures, thereby offering a new field of application of electron beams.
Use of the microsecond plasma opening switch for material surface modification
Vitaly M. Bystritskii,
I. V. Lisitsyn,
A. V. Sinebryukhov,
et al.
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The application of Plasma Opening Switch (POS) with microsecond current rise time duration for a source of a high power pulsed ion beam, used for surface treatment is being considered. The experiments are considered on the stored current amplitude in the POS of 200 kA with ion beam duration of 40-80 ns, energy about 1 MeV and current density of 20- 150 A/cm2. The cross-section of this beam reached 1000 cm2. The scaling studies analysis is given which proves the reliability and potential of the said approach for technology needs. The method could be used for processing metal parts with big areas, complicated shapes and surfaces to get enhanced microhardness, corrosion strength, especially in case of stainless steel.
Pulsed-power microwave surface discharge in vacuum for diamond-like films deposition
Alexander A. Ravaev,
Alexander V. Medvedovsky,
Pavel S. Chernyshev
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This paper is devoted to a new method of depositing diamond-like films onto various substrates by use of a plasma flare generated by a surface discharge on a carbon target in vacuum under action of intense pulsed microwave (MW) beam. The first part of the report presents a brief review of experimental investigations of nonlinear interaction of strong microwaves (X-band, MW intensities of 0.01-10 MW/cm2, and pulse duration of 50-100 ns, 1-100 microsecond(s) ) with a plasma flare. A generation of strong Lengmuir waves and the following electron acceleration in a plasma resonance region cause an effective transformation of a MW energy into a plasma flare, a creation of high plasma potentials, and a production of ions with energies from thermal to as high as tens keV. The second part reflects the first experiments on pulsed MW deposition of diamond-like films on various substrates. Deposition rate up to 0.5 micrometers per 1 sec of a 'net' MW irradiation time was reached, and diamond- like films with good optical characteristics were obtained. The small plasma-reactor bench, other obtained practical results, and technique perspectives are discussed in detail.
Modification of defect structure of metallic materials by high-power-pulsed microwaves
Yurii P. Sharkeev,
Natalya V. Girsova,
Andrey N. Didenko,
et al.
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The results of electron microscopy investigation of dislocation structures in annealed copper by exposure to high power pulsed microwave (HPPM) are presented. It was established that exposure of copper targets to HPPM results in the dislocation structure formation into the skin layer and outside it. Such modification of dislocation structure in metab surface layers may results in essentially increasing of mechanical properties of metals.
Pulse Power for Lasers and Accelerators
Technological ion source and its applications
Nikolay Vasilievic Gavrilov,
V. N. Mizgulin,
Sergey Pavlovich Nikulin,
et al.
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An ion beam source based on a glow discharge in a magnetic field has been developed to produce gas and carbon ion beams with a cross sectional area of up to 200 cm2. The source comes in two modifications, one of which, generating continuous beams of low-energy ions with a current of up to 150 mA, is used to treat material surfaces before deposition of coatings. The other, generating pulse-repetitive ion beams with a current of up to 1 A, ion energy up to 40 keV, pulse duration of 1 ms at a frequency of 3-50 Hz, is used to implant ions into materials. The source features a straightforward design and power circuit, high reliability and long lifetime, these advantages being ensured through the use of cold cathode discharge needing no initiating system.
High-regulation, capacitor-charging power supplies
Ed Strickland,
F. Cathell,
Kevin Harris,
et al.
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Advanced applications in the impulse radar, RF accelerator and laser industries require a high voltage capacitor charging power supply capable of voltage regulation <EQ+/- 0.05% for load capacitances on the order of 100 nF. This regulation may be necessary at rep-rates up to 1 kHz. This paper discusses several topologies considered and the performance trade-offs of both the power converter when combined with the typical control scheme. Based on measurement criteria such as efficiency, size, weight, cost and reliability for given component stresses, the series resonant power converter provides the optimum enabling technology to maximize the value of the high voltage capacitor charging power supply. However, the series resonant topology when combined with the classical pulse rate modulation (PRM) control scheme is limited in achieving a high degree of regulation for small value capacitive loads. This paper discusses a series resonant power supply combined with a patented control scheme which has demonstrated regulation <EQ+/- 0.05% for capacitive loads >= 20 nF. This regulation has been demonstrated over a product family having output powers from 2 to 10 kJ/s and output voltage up to 50 kV. The power converter utilizes IGBT switches and a transformer rectifier high voltage topology.
Novel nanosecond semiconductor opening switch for megavolt repetitive pulsed power technology: experiment and applications
Yu. A. Kotov,
Gennady A. Mesyats,
S. N. Rukin,
et al.
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A novel nanosecond semiconductor opening switch (SOS) has been developed which has a pulsed power of the GW range and voltage levels of up to a few 100's of kV. The SOS is based on high-voltage solid state rectifiers and is designed for pulsed power generators with inductive energy storage. A 30 ns opening phase duration, a 45 kA interrupted current, and a 450 kV opened SOS voltage have been attained with the use of a three-stage, 2 kJ, 150 kV open circuit Marx generator as the SOS driver. On the basis of the experimental results obtained, we have developed and tested repetitive high-current generators and accelerators with a 0.5 MV output voltage and a 15 to 100 ns pulse width. The ideology is presented of constructing high-power megavolt pulsed generators with an all-solid- state switching system. A description is provided of the setups developed on this principle. We discuss features peculiar to the setups developed and prospects of developing these further.
Modulating the output of a XeCl* laser by a pulsed-power electrical soliton generator
Stephen A. Fairlie
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A new pulsed power technique is described for exciting a XeCl* excimer laser to produce a sequence of high recurrence frequency output pulses. A novel driving circuit is demonstrated, centered around capacitors made from a nonlinear ferroelectric ceramic dielectric material. If certain conditions are met, then a discrete component transmission line built with these capacitors can generate an array of high-power electrical soliton pulses from a single input pulse. For a quasi-cw laser, such as a rare-gas-halide excimer, the modulation of the laser pump power generated by such a nonlinear transmission line, is passed on to produce a similarly modulated laser output. Experimental results are presented showing laser output modulation and further studies are described with regard to improving the generation soliton arrays suitable for driving lasers at high pulse recurrence frequencies.
Concepts in the integration of photoconductive systems with electro-optics and gain media
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Light activated semiconductor switches (LASS), when operated in the linear regime, have demonstrated the highest power and fastest rise-time of any other solid state switch. This, in conjunction with their picosecond jitter, allows their integration with electro-optic and magneto-optic devices to serve as an optically controlled optical switches (OCOS). The combination of OCOS with various other optical elements and gain media allows the assembly of various optical circuits that are faster, smaller in size and operate at a higher power density. This paper will discuss the underlying principles of such optical circuits. In addition, experimental results of a microlaser which is Q- switched with an LASS driven Pockets cell with a rise-time of 70 ps will be described, and future laser development based on LASS technology will be presented.
Present status of the bistable optically controlled semiconductor switch (BOSS)
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The Bistable Optically controlled Semiconductor Switch (BOSS) is currently the only completely controllable high power solid state switch which operates on sub-nanosecond to microsecond time scales. The present state of BOSS technology is discussed, including the present limits of operation and potential extensions of these limits. Current and novel applications which take best advantage of the BOSS performance characteristics are described.
Ultrawideband current sensor based on the Faraday effect in semimagnetic semiconductors
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Very fast current transients (10 A, 5 GHz) have been measured using the Faraday rotation in CdMnTe sample. RF magnetic fields with an amplitude of < 10 G have been measured, despite the laser intensity noise (at these bandwidths) and the noisy environments. This paper describes a technique whereby the insertion loss is minimized and the effect of the laser intensity noise reduced, enabling these small RF fields to be measured for the first time.
Environmental Related Technologies
Pulsed electron beams for flue-gas treatment
Gennady A. Mesyats,
Yuri N. Novoselov,
D. L. Kuznetsov
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The development of industrial society creates serious threats to the safe existence of the biosphere, including man. Cleaning air from toxic exhausts becomes therefore one of the challenges. The global problem of air cleaning can be solved in a number of ways. We restrict our attention to one of the possible methods, the use of pulsed electron beams to clean sulfur oxides from the flue gases of power plants. Irradiation of flue gases by the increased density of pulsed electron beams permits a charges, excited particle concentration that is optical for the removal of specific toxic impurities. We present the most important results of these experiments.
The e-SCRUB Machine: an 800-kV, 500-kW average power pulsed electron beam generator for flue-gas scrubbing
James R. Cooper,
Ray Briggs,
Walter F.J. Crewson,
et al.
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This paper gives an overview of electron beam dry scrubbing (EBDS) to remove SOx and NOx from flue gases of coal-fired power plants. It also describes the e-SCRUB program, a program currently underway to commercialize this process with an integrated pulsed electron beam. The electron beam, together with injected water and ammonia, causes chemical reactions which convert the SOx and NOx into commercial grade agricultural fertilizer, a usable byproduct. The e-SCRUB facility is a test bed to demonstrate the feasibility and performance of a repetitive, reliable pulsed electron beam generator operating at average power levels of up to 1 MW. This facility contains the electron beam generator and all the auxiliary and support systems required by the machine, including a computer driven central experiment control system, a 100,000 SCFM flowing dry nitrogen load which simulates the characteristics of a power plant flue, and a 2 MVA dedicated electrical service to power the machine. The e-SCRUB electron beam machine is designed to produce an 800 kV pulsed electron beam with a repetition rate of 667 pps. The energy per pulse deposited into the flue gas is approximately 750 J. The pulsed power system converts the utility power input to a 667 pps, 800 kV pulse train which powers the electron gun. The functional units of the pulsed power system will be discussed in the paper, along with some preliminary experimental results.
Flue-gas cleaning using heterogeneously pulsed discharge
E. Yankelevitch,
Vitaly M. Bystritskii,
A. V. Sinebryukhov,
et al.
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A new promising electro physical method for cleaning flue gases from sulfur and nitrogen oxides has been proposed. This method is based on the initiation of repetitive arc micro discharges in an air-water mixture. The report gives a description of the setup used in an experimental verification of the method, the experimental results obtained, and the results of their analyses. It has been demonstrated that the proposed method has some advantages over other electro physical methods, such as simplicity to realize and operability in a highly humidified gas stream, which substantially extends the realize of its possible applications. The energy required to remove harmful impurity is 200 eV/mol and 23 eV/mol for gas mixtures with NO and SO2, respectively, which is an excellent result for an electro physical method of gas cleaning.
Reduction of aluminum, silicon, and boron oxides in a carbon plasma of pulsed-power microwave discharge
Alexander A. Ravaev,
Iskander K. Tagirov,
Pavel S. Chernyshev
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The high stability of aluminum, silicon and boron oxides is well known. A thermodynamic analysis of usual reactions of a carbon reduction of these oxides indicates that a degree of their conversion is quite low: for example, less than 0.3% for the alumina reduction at temperatures approximately equals 1900 K. On the other hand, a high efficiency of plasma-chemical processes and advantages of the user of microwave produced plasmas for materials processing are not a secret too. It was very interesting, from this viewpoint, to conduct mentioned reactions in a plasma of the pulsed power microwave (PPMW) discharge. Experiments were carried out in the focal zone of a focused PPMW beam at intensities up to 5 X 104 MW/cm2 (wavelength - 4 cm, pulse duration - 1...1000 microsecond(s) , repetition rate - 10 Hz). Quartz retorts containing powdered mixtures of outlined oxides with stoichiometric quantities of a carbon-black were pumped down to initial pressures of approximately equals 1 Torr. During the plasma treatment the pressure inside retorts grew and reached values of 100-200 Torr. After that retorts were pumped down again, and the process was continued. The total time of powders processing was of 20-60 min, and the samples' temperatures did not exceed 1300 K. Thus, for example, at the time of reduction of mixtures Al2O3 + C in amounts of 2 g, about 0.3 'normal' liters of gases were evolved, that corresponds to approximately equals 30% degree of the alumina conversion. Simultaneously, a strong influence of the steamer-like PPMW discharge in the atmosphere outside retorts on the reduction process was observed. Obviously, the reactions proceed at a higher rate due to the inducing role of a intense UV- radiation of such discharges. It is an important practical result too.
Environmental Related Technologies: Fluids and Solids
Commercial applications of electron beam advanced oxidation technology
Randy D. Curry,
John T. Bosma
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Emerging commercial applications of electron-beam advanced oxidation technology offer a significant advancement in the treatment of waste steams. Both electron beam and X-ray (Brehmsstrahlung) advanced oxidation processes have been shown to be effective in the destruction of volatile and semivolatile organic compounds. Emerging commercial applications, however, far exceed in scope current applications of oxidation technologies for the destruction of simple semivolatile and volatile organic compounds in water. Emerging applications include direct treatment of contaminated soil, removal of metal ions from water and sterilization of water, sludges, and food. Application of electron beam advanced oxidation technologies are reviewed, along with electron- beam-generated X-ray (Brehmsstrahlung) advanced oxidation processes. Advantages of each technology are discussed along with advanced accelerator technologies which are applicable for commercial processing of waste streams. An overview of the U.S. companies and laboratories participating in this research area are included in this discussion.
Advances in the development of the nested high-voltage generator
Richard J. Adler,
Robert J. Richter-Sand,
M. Lobitz
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The Nested High Voltage Generator (NHVG) is a high voltage accelerator/power supply topology which can potentially satisfy a variety of requirements for a compact, reliable inexpensive DC accelerator in the 0.25 10 MeV range. Applications for this technology include the generation of high voltage, high current pulsed electron beams for microwave generation (for example in the NLC or Next Linear Collider), medical product sterilization, polymer curing, waste water sterilization, waste water remediation, and medical waste sterilization. This technology has recently been demonstrated in an accelerator which has operated at 500 kV with an electron beam in a 36 inch long, 17 inch diameter device. In this paper, we briefly describe the technology, and the capabilities of our 500 kV machine. We also describe the capabilities of a machine of further reduced size.
Effect of submicrosecond electric fields on microorganisms: experiments and applications
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Previous studies on the effect of microsecond pulsed electric fields on bacteria have shown that the lethality increases linearly with pulse duration and exponentially with electric field strength. In order to determine the validity of this law for submicrosecond pulses, we applied pulses of fifty nanosecond duration to two strains of E. coli and to a marine crustacean. The results indicated that even at this short pulse duration, the empirical law not only holds for bacteria, but also for more complicated organisms. Theoretical considerations, however, and the observation of a pronounced difference in the field induced lethality of two strains of E. coli led us to believe that a change in the effect can be expected when the pulse duration is reduced further. The observed dependance of micro-organism lethality or temporary damage on field strength and pulse duration allows us to improve the energy efficiency of systems which make use of the effect. Examples are sterilizers (e.g., for food and water) and electrical filters for the prevention of biofouling in cooling systems.
Dual-Use Application of Lasers: Manufacturing
Possible diagnostic signal for monitoring CO2 laser welding of aluminum alloy sheets
Hongping Gu,
Walter W. Duley
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In an effort to look for a diagnostic signals for in-line monitoring during laser welding of aluminum alloy, a pyroelectric detector was used to record the reflected laser radiation from the weld pool when a CO2 laser welds aluminum alloy sheets. The signals were processed with a fast-Fourier transform (FFT). From the FFT spectrum strong components of the reflected laser radiation in the low frequency range were found to be a strong function of laser welding variables. When the laser intensity is kept constant, a minimum signal is found at a particular welding speed. At speeds of either slower or faster than that particular speed, the signals increase up to a factor of 3 or more. No corresponding components were noticed in the photodiode signals. Analysis of the weldments indicates that optimum welding is produced around this specific speed.
Efficient mid-infrared conversion technologies
Charles I. Miyake,
Dennis D. Lowenthal
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Average power scaling of mid-infrared Optical Parametric Oscillators are presently limited by nonlinear material bulk absorption and resulting thermal gradients and thermally induced focusing and higher order aberrations. We discuss an optical correction scheme that corrects higher order aberrations typically present in gaussian intensity profile beams used for pumping OPO's to reduce the nonlinear dephasing by one- half. While correction of thermal focus has been shown to improve the power scaling in an OPO, further improvements can be made by correcting the remaining higher order aberrations. Such reduction in dephasing should significantly improve the power scaling potential of solid state lasers and OPO's.
Dual-use applications for e-beam-pumped semiconductor lasers
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The collapse of the Soviet Union opened many areas of laser technology to the West. E-beam-pumped semiconductor lasers were pursued for 25 years in several Soviet institutes. Thin single crystal screens of II-VI alloys (ZnCdxSe1-x, CdSxSe1-x) were incorporated in laser CRTs to produce scanned visible laser beams at average powers greater than 10 W. Resolutions of 2500 lines were demonstrated by the Russians. MDA-W is performing a contract for ARPA to assess e-beam- pumped semiconductor laser technology for high brightness, high resolution RGB laser projection application. Transfer of II-VI crystal growth and screen processing technology is underway, and initial results will be reported. Various techniques (cathodoluminescence, one- and two- photon laser pumping, etc.) were used to assess material quality and screen processing damage. High voltage (75 kV) video electronics were designed and procured in the U.S. to operate test laser tubes obtained from Russian sources. The primary military applications of interest to MDA are flight simulator visuals, command center large screen projection and possibly cockpit display. Laser radar, designation, and communication are secondary applications. Some of the commercial applications included electronic cinema, teleconference display, university auditorium display, laser microscopy, and optical computing. Applications and plans for commercialization will be discussed.
Influence of laser-induced capillary waves on heat and mass transfer in the arc-augmented laser processing of metals
Andrey Valentinov Levin,
Alexandre E. Zaikin,
Alexei L. Petrov
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An experimental study is reported of the influence of capillary waves on heat and mass transfer in molten metal during gas tungsten arc (GTA)- augmented laser processing by cw CO2-laser radiation of q approximately equals 2- 4.5 MW/cm2 intensity. Capillary waves excited on the melt surface by a periodic pulsed reaction of a metal vapor jet had complex dynamics. An analysis of the experimental results indicated a considerable change in heat and mass transfer in the melt when three-dimensional vibrations were excited, compared with the processes that occur at q < 2 MW/cm2. Such changes enhanced the mixing of an alloying elements (compared with the familiar alloying methods) and established the optimal (for surface processing of metals) shape of a molten bath.
Dual-Use Applications of Lasers: LIDAR
Mid-infrared DIAL lidar for petroleum exploration and pipeline monitoring
Allen R. Geiger,
S. N. Prasad
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The chemical absorption spectra of the light hydrocarbons in the infrared region from 3 to 4 micrometers allows the use of DIAL techniques for monitoring these chemicals. The light hydrocarbons; methane, ethane, propane, and butane can be used as petroleum deposit indicators for petroleum exploration, or as gases associated with pipeline leaks. Both of these applications have direct economic and environmental applications. A prototype light hydrocarbon lidar using optical parametric oscillator (OPO) technology has been built for Phillips Petroleum Co.. Advances in OPO technology as a result of this effort will result in light weight airborne DIAL lidars for exploration and pipeline monitoring.
Intersatellite-laser-ranging experiment for global-change sensing and 21st century satellite control
David M. Gleason
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The optimal integration of precise multiple-antenna GPS receivers, advanced cryogenic inertial measurement units (IMU's), and ultra-stable frequency laser ranging devices on two low altitude, copolar orbiting spacecraft forms the basis of a multifaceted/interdisciplinary proposal. Scientific objectives are to (1) sense geodynamic gravitation changes and (2) substantially improve a variety of temporal geophysical models. Such models will make the Air Force Satellite Control Network's orbit determination process more accurate and affordable. The use of differential GPS (DGPS) observations, as external updates in an elaborate Kalman filter optimally integrating the three data types, puts a bound on the low frequency IMU and laser error buildups. In the filter the DGPS, IMU, and laser data streams aid each other to obtain the experiment's two navigation goals: determining the satellites' positions and orientations to centimeter and arc second accuracies. If each satellite also possesses stereo optical (3D) and multispectral sensors, global 3D Earth background image files could be built in both the visible and IR regimes.
Remote and point sensing with near-IR tunable diode lasers
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Near-infrared semiconductor diode lasers are useful for spectroscopic monitoring of a number of chemical species at parts-per-million levels and below. Although these devices are typically used in point sensing geometries, they can also be used in several remote sensing configurations. In this paper we discuss some of the properties of these lasers that are relevant for point detection, and we discuss a simple scheme to measure temperature and pressure. In the context of remote sensing, we discuss several modulation methods that allow for range- resolved detection of chemicals and aerosols using continuous wave diode lasers.
Multipurpose cw CO2 autodyne lidar
Eugeni P. Gordov,
Gennady S. Khmelnitskii
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Laser monitoring of atmospheric and polluting gas concentrations in the atmosphere as well as laser detection and imaging are still need in sensitive and simple in design and operation lidar instruments especially in those which can perform the above both types of measurements simultaneously. Autodyne lidars appear to be quite candidate to this end. Reported are results of design of a laboratory prototype of cw CO2 multipurpose lidar based on suggested earlier approach performing the both tasks, i.e. for path gas analysis and remote determination of optical and dynamical characteristics of a retroreflector (distant mirror, aerosol layer or topographical target).
Dual-Use Applications of Lasers: Medical
Portable semiconductor laser system to stop internal bleeding
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One significant cause of death during a sever trauma (gun wound or stab wound) is internal bleeding. A semiconductor diode laser system has been used in in vitro studies of cauterizing veins and arteries to stop bleeding. The conditions of laparoscopic surgery, including bleeding conditions (blood flow and pressure), are simulated. Results have been obtained both with and without using a hemostat (e.g., forceps) to temporarily stop the bleeding prior to the cautery. With the hemostat and a fiber-coupled 810-nm laser, blood vessels of up to 5 mm diameter were cauterized with an 8 W output from the fiber. Great cautions must be used in extrapolating from these in vitro results, since the exact conditions of bleeding in a living being are impossible to exactly reproduce in a laboratory in-vitro experiment. In a living being, when blood flow stops the cessation of nourishment to the vessels results in irreversible physiological changes. Also, the blood itself is different from blood in a living being because an anti-clotting agent (heparin) was added in order to inhibit the blood's natural tendency to coagulate.
Automated placement of retinal laser lesions in vivo
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Researchers at the University of Texas at Austin's Biomedical Engineering Laser Laboratory investigating the medical applications of lasers have worked toward the development of a retinal robotic laser system. The overall goal of the ongoing project is to precisely place and control the depth of laser lesions for the treatment of various retinal diseases such as diabetic retinopathy and retinal tears. Researchers at the USAF Academy's Department of Electrical Engineering and the Optical Radiation Division of Armstrong Laboratory have also become involved with this research due to similar related interests. Separate low speed prototype subsystems have been developed to control lesion depth using lesion reflectance feedback parameters and lesion placement using retinal vessels as tracking landmarks. Both subsystems have been successfully demonstrated in vivo on pigmented rabbits using an argon continuous wave laser. Work is ongoing to build a prototype system to simultaneously control lesion depth and placement. Following the dual-use concept, this system is being adapted for clinical use as a retinal treatment system as well as a research tool for military laser-tissue interaction studies. Specifically, the system is being adapted for use with an ultra-short pulse laser system at Armstrong Laboratory and Frank J. Seiler Research Laboratory to study the effects of ultra-short laser pulses on the human retina. The instrumentation aspects of the prototype subsystems were presented at SPIE Conference 1877 in January 1993. Since then our efforts have concentrated on combining the lesion depth control subsystem and the lesion placement subsystem into a single prototype capable of simultaneously controlling both parameters. We have designated this combined system CALOSOS for Computer Aided Laser Optics System for Ophthalmic Surgery. We have also investigated methods to improve system response time. Use of high speed nonstandard frame rate CCD cameras and high speed frame grabbers hosted on personal computers featuring the 32 bit, 33 MHz PCI bus have been investigated. Design details of an initial CALOSOS prototype design is provided in SPIE Conference proceedings 2396B-32 (Biomedical Optics Conference, Clinical Laser Delivery and Robotics Session). This paper will review in vivo testing to date and detail planned system upgrades.