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Sample records for dioxide laser radiation

  1. Syneresis of vitreous by carbon dioxide laser radiation.

    PubMed

    Bridges, T J; Patel, C K; Strnad, A R; Wood, O R; Brewer, E S; Karlin, D B

    1983-03-11

    In carbon dioxide laser surgery of the vitreous a process of vaporization has been advocated. In this report syneresis, a thermal liquefaction of gel, is shown to be over ten times more efficient on an energy basis than vaporization. Syneresis of vitreous is experimentally shown to be a first-order kinetic process with an activation energy of 41 +/- 0.5 kilocalories per mole. A theory of laser surgery in which this figure is used agrees closely with results from laser experiments on human eye-bank vitreous. The syneresis of vitreous by carbon dioxide laser radiation could lead to a more delicate form of ocular microsurgery, and application to other biological systems may be possible.

  2. Syneresis of Vitreous by Carbon Dioxide Laser Radiation

    NASA Astrophysics Data System (ADS)

    Bridges, T. J.; Patel, C. K. N.; Strnad, A. R.; Wood, O. R.; Brewer, E. S.; Karlin, D. B.

    1983-03-01

    In carbon dioxide laser surgery of the vitreous a process of vaporization has been advocated. In this report syneresis, a thermal liquefaction of gel, is shown to be over ten times more efficient on an energy basis than vaporization. Syneresis of vitreous is experimentally shown to be a first-order kinetic process with an activation energy of 41 ± 0.5 kilocalories per mole. A theory of laser surgery in which this figure is used agrees closely with results from laser experiments on human eye-bank vitreous. The syneresis of vitreous by carbon dioxide laser radiation could lead to a more delicate form of ocular microsurgery, and application to other biological systems may be possible.

  3. Interaction of carbon dioxide laser radiation with a nanotube array in the presence of a constant electric field

    SciTech Connect

    Sadykov, N. R.; Scorkin, N. A.

    2012-06-15

    The dependence of the current density on the leading edge width of the alternating (high-frequency) field amplitude is studied at various constant (or unsteady) fields. The dependence of amplified microwaves in the two-millimeter range on a longitudinal coordinate is determined. The problem of submillimeter radiation generation in a system of parallel carbon nanotubes exposed to two-frequency carbon dioxide (CO{sub 2} laser) laser radiation in the presence of a constant (or unsteady) field is studied. The possibility of using freely oriented carbon nanotubes parallel to each other is shown.

  4. Laser surgery: using the carbon dioxide laser.

    PubMed Central

    Wright, V. C.

    1982-01-01

    In 1917 Einstein theorized tha through an atomic process a unique kind of electromagnetic radiation could be produced by stimulated emission. When such radiation is in the optical or infrared spectrum it is termed laser (light amplification by stimulated emission of radiation) light. A laser, a high-intensity light source, emits a nearly parallel electromagnetic beam of energy at a given wavelength that can be captured by a lens and concentrated in the focal spot. The wavelength determines how the laser will be used. The carbon dioxide laser is now successfully employed for some surgical procedures in gynecology, otorhinolaryngology, neurosurgery, and plastic and general surgery. The CO2 laser beam is directed through the viewing system of an operating microscope or through a hand-held laser component. Its basic action in tissue is thermal vaporization; it causes minimal damage to adjacent tissues. Surgeons require special training in the basic methods and techniques of laser surgery, as well as in the safety standards that must be observed. Images FIG. 5 PMID:7074503

  5. 21 CFR 179.43 - Carbon dioxide laser for etching food.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Carbon dioxide laser for etching food. 179.43... FOOD Radiation and Radiation Sources § 179.43 Carbon dioxide laser for etching food. Carbon dioxide... conditions: (a) The radiation source consists of a carbon dioxide laser designed to emit pulsed...

  6. 21 CFR 179.43 - Carbon dioxide laser for etching food.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Carbon dioxide laser for etching food. 179.43... § 179.43 Carbon dioxide laser for etching food. Carbon dioxide laser light may be safely used for... consists of a carbon dioxide laser designed to emit pulsed infrared radiation with a wavelength of...

  7. Tunable pulsed carbon dioxide laser

    NASA Technical Reports Server (NTRS)

    Megie, G. J.; Menzies, R. T.

    1981-01-01

    Transverse electrically-excited-atmosphere (TEA) laser is continuously tunable over several hundred megahertz about centers of spectral lines of carbon dioxide. It is operated in single longitudinal mode (SLM) by injection of beam from continuous-wave, tunable-waveguide carbon dioxide laser, which serves as master frequency-control oscillator. Device measures absorption line of ozone; with adjustments, it is applicable to monitoring of atmospheric trace species.

  8. Comparative bactericidal exposures for selected oral bacteria using carbon dioxide laser radiation

    SciTech Connect

    Dederich, D.N.; Pickard, M.A.; Vaughn, A.S.; Tulip, J.; Zakariasen, K.L. )

    1990-01-01

    Although relatively high CO{sub 2} laser energies have been shown to sterilize root canals, the response of several bacterial strains to decreasing exposures of CO{sub 2} laser energy remains unknown. Freshly grown bacterial cells were irradiated on glass microscope coverslips. A comparison of equivalent energy exposures with differing parameters was made on the bacterial viability. No statistically significant difference was found in the energy required to kill closely related bacterial species. However, the energy density required to kill greater than 99.5% of the bacteria is less than 200 J/cm{sup 2}, much less than that shown to sterilize in a previous study.

  9. Carbon dioxide slab laser

    SciTech Connect

    Tulip, J.

    1988-01-12

    A gas slab laser is described comprising: first and second elongated electrodes each including a planar light reflecting surface disposed so as to form a light guide only in a plane perpendicular to the planar surface and to define a gas discharge gap therebetween; a laser gas disposed in the gap; and means for applying a radio frequency current between the first and second electrodes to establish a laser-exciting discharge in the laser gas.

  10. Gamma radiation characteristics of plutonium dioxide fuel

    NASA Technical Reports Server (NTRS)

    Gingo, P. J.

    1969-01-01

    Investigation of plutonium dioxide as an isotopic fuel for Radioisotope Thermoelectric Generators yielded the isotopic composition of production-grade plutonium dioxide fuel, sources of gamma radiation produced by plutonium isotopes, and the gamma flux at the surface.

  11. Treatment of developmental defect of upper lip with carbon dioxide laser radiation (CO2): first surgical time.

    PubMed

    Niccoli-Filho, Walter; Murilo-Santos, Lucio; Schubert, Mark; Morosolli, Aline Cantarelli

    2005-06-01

    With the exception of the cleft lip, developmental defects (DD) of the lip are rare. The upper lip originates from the ectomesenchyme and is formed by the merging of the nasal medial and lateral processes with the maxillary process. Disturbances during this formation period can cause DD with functional and/or esthetic repercussions. We present a case of DD of the upper lip in a patient with a history of progressive growth of the left lateral portion of the upper lip that occurred from the time of birth until the age of 22 years. Clinical examination revealed hypertrophy of the area from the left philtral columns to the left commissure of the lip, extending the portion of the surface mucosa creating a flaccid and asymptomatic tissue mass. All other buccal structures appeared to be within normal limits and without any evidence of defects or deformities. In the surgical planning we decided to carry out corrective surgery in two phases. The first phase accomplished a conservative excision of the total abnormal labial tissue mass with a CO2 laser radiation (5 W in continuous mode, bunch diameter Phi = 0.6 mm with a power density of 768 W/cm2 and fluency of 0.231 J/cm2) being careful to preserve the vermilion portion of the lip. Postsurgical clinical evaluations were done every three days until the skin sutures were removed and then every seven days until two months post surgery. While the entire mass of excessive tissue could not be completely removed, the removal of the excessive mucosal tissue produced a very good outcome relative to lip function, with a good esthetic result without scarring, and good tissue mobility. The results showed that the CO2 laser is an extremely useful instrument that can provide excellent control of the surgical field and allow for healing that produces excellent functional and esthetic results.

  12. Formation of micron and submicron structures on a zirconium oxide surface exposed to nanosecond laser radiation

    SciTech Connect

    Ganin, D V; Mikolutskiy, S I; Khomich, V Yu; Yamshchikov, V A; Tokarev, V N; Shmakov, V A

    2014-04-28

    Possibility of forming quasi-periodic structures of micron and submicron dimensions on a surface of zirconium dioxide under the action of eximer ArF laser radiation is shown experimentally and theoretically. (interaction of laser radiation with matter)

  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. Carbon Dioxide Laser Fiber Optics In Endoscopy

    NASA Astrophysics Data System (ADS)

    Fuller, Terry A.

    1982-12-01

    Carbon dioxide laser surgery has been limited to a great extent to surgical application on the integument and accessible cavities such as the cervix, vagina, oral cavities, etc. This limitation has been due to the rigid delivery systems available to all carbon dioxide lasers. Articulating arms (series of hollow tubes connected by articulating mirrors) have provided an effective means of delivery of laser energy to the patient as long as the lesion was within the direct line of sight. Even direct line-of-sight applications were restricted to physical dimension of the articulating arm or associated hand probes, manipulators and hollow tubes. The many attempts at providing straight endoscopic systems to the laser only stressed the need for a fiber optic capable of carrying the carbon dioxide laser wavelength. Rectangular and circular hollow metal waveguides, hollow dielectric waveguides have proven ineffective to the stringent requirements of a flexible surgical delivery system. One large diameter (1 cm) fiber optic delivery system, incorporates a toxic thalliumAbased fiber optic material. The device is an effective alternative to an articulating arm for external or conventional laser surgery, but is too large and stiff to use as a flexible endoscopic tool. The author describes the first highly flexible inexpensive series of fiber optic systems suitable for either conventional or endoscopic carbon dioxide laser surgery. One system (IRFLEX 3) has been manufactured by Medlase, Inc. for surgical uses capable of delivering 2000w, 100 mJ pulsed energy and 15w continuous wave. The system diameter is 0.035 inches in diameter. Surgically suitable fibers as small as 120 um have been manufactured. Other fibers (IRFLEX 142,447) have a variety of transmission characteristics, bend radii, etc.

  15. Pulsed-discharge carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Willetts, David V.

    1990-01-01

    The purpose is to attempt a general introduction to pulsed carbon dioxide lasers of the kind used or proposed for laser radar applications. Laser physics is an excellent example of a cross-disciplinary topic, and the molecular spectroscopy, energy transfer, and plasma kinetics of the devices are explored. The concept of stimulated emission and population inversions is introduced, leading on to the molecular spectroscopy of the CO2 molecule. This is followed by a consideration of electron-impact pumping, and the pertinent energy transfer and relaxation processes which go on. Since the devices are plasma pumped, it is necessary to introduce a complex subject, but this is restricted to appropriate physics of glow discharges. Examples of representative devices are shown. The implications of the foregoing to plasma chemistry and gas life are discussed.

  16. Stimulated radiative laser cooling

    NASA Astrophysics Data System (ADS)

    Muys, P.

    2008-04-01

    Building a refrigerator based on the conversion of heat into optical energy is an ongoing engineering challenge. Under well-defined conditions, spontaneous anti-Stokes fluorescence of a dopant material in a host matrix is capable of lowering the host temperature. The fluorescence is conveying away a part of the thermal energy stored in the vibrational oscillations of the host lattice. In particular, applying this principle to the cooling of (solid-state) lasers opens up many potential device applications, especially in the domain of high-power lasers. In this paper, an alternative optical cooling scheme is outlined, leading to the radiative cooling of solid-state lasers. It is based on converting the thermal energy stored in the host into optical energy by means of a stimulated nonlinear process, rather than a spontaneous process. This should lead to better cooling efficiencies and a higher potential of applying the principle for device applications.

  17. Endoscopic Carbon Dioxide Laser Photocoagulation Of Bleeding Canine Gastric Ulcers

    NASA Astrophysics Data System (ADS)

    Gal, Dov; Ron, Nimrod; Orgad, Uri; Katzir, Abraham

    1987-04-01

    This is the first report which describes carbon dioxide laser photocoagulation of upper gastrointestinal bleeding via a flexible endoscope, using an infrared transmitting siver nalide fiber. Various laser parameters were checked to determine the optimal conditions for hemostasis. Both the acute effects of laser irradiation on tissue and the chronic effects on healing process were examined. Preliminary results indicate that carbon dioxide laser beam can successfully photocoagulate moderately bleeding ulcers.

  18. New Trends In Carbon Dioxide Laser Microsurgery

    NASA Astrophysics Data System (ADS)

    Smith, M. R.; Miller, James B.

    1981-05-01

    The carbon dioxide laser has been used for cutting and cauterizing tissue in a variety of surgical procedures by means of a dry-field air/tissue interface approach. Recently, a new wet-field CO2 laser technique has been developed and is being used successfully in humans to seal intraocular fibrovascular fronds and retinal tears at the time of vitrectomy, to close rubeotic vessels in the iris, and to excise fibrovascular fronds and epiretinal membranes in cases of severe diabetic retinopathy. Specialized wet-field CO2 photosurgical probes for use in gynecologic microsurgery have been developed and are being studied experimentally. Other potential applications include otolaryngologic micro-surgery, neurosurgery, and gastrointestinal and urologic wet-field surgery.

  19. Solar pumped continuous wave carbon dioxide laser

    NASA Technical Reports Server (NTRS)

    Yesil, O.; Christiansen, W. H.

    1978-01-01

    In an effort to demonstrate the feasibility of a solar pumped laser concept, gain has been measured in a CO2-He laser medium optically pumped by blackbody radiation. Various gas mixtures of CO2 and He have been pumped by blackbody radiation emitted from an electrically heated oven. Using a CO2 laser as a probe, an optical gain coefficient of 1.8 x 10 to the -3rd/cm has been measured at 10.6 microns for a 9:1 CO2-He mixture at an oven temperature of about 1500 K, a gas temperature of about 400 K and a pressure of about 1 torr. This corresponds to a small signal gain coefficient when allowance is made for saturation effects due to the probe beam, in reasonable agreement with a theoretical value.

  20. a Blackbody-Pumped Carbon Dioxide Laser

    NASA Astrophysics Data System (ADS)

    Insuik, Robin Joy

    A proof of concept experiment has been carried out to demonstrate the feasibility of using blackbody radiation to pump a gas laser. Building on earlier experiments in which optical gain was measured in a CO(,2) laser mixture exposed to blackbody radiation at a temperature of 1500(DEGREES)K, continuous wave oscillation of CO(,2) has been achieved, for the first time, using radiation from a blackbody cavity as the pump source. This was made possible by actively cooling the laser mixture as it was exposed to the radiation field of an electrically heated oven. Output power measurements are presented from a series of experiments using mixtures of CO(,2), He, and Ar. Maximum output power was obtained with a 20%CO(,2) - 15%He- 65%Ar mixture at pressures around 6-10 Torr. The output power was found to vary greatly with the gas temperature and the blackbody temperature. By varying these parameters output powers up to 8 mW have been achieved. The effects of the buffer gas are also shown to be important. Based on the experimental results, it is believed that the buffer gas is needed to inhibit diffusion of the excited species out of the laser mode volume. This diffusion leads to deactivation at the walls. Adding more CO(,2) results in a decrease in output power, indicating that the gas has a finite optical depth and the mode volume is not pumped if too much CO(,2) is present. A model which incorporates these effects is presented. The predicted small signal gains and powers based on this model adequately match the trends observed experimentally.

  1. Fractional carbon dioxide laser in recalcitrant vulval lichen sclerosus.

    PubMed

    Lee, Andrew; Lim, Adrian; Fischer, Gayle

    2016-02-01

    Vulval lichen sclerosus is an uncommon skin condition that can usually be managed with topical corticosteroids to maintain remission. However, there is a subset of patients in whom it remains recalcitrant despite treatment with super-potent topical corticosteroids. We report a case series of four patients undergoing fractional carbon dioxide laser resurfacing and one with ablative carbon dioxide laser for severe, hyperkeratotic vulval lichen sclerosus not responding to super-potent topical corticosteroids. In these patients, carbon dioxide laser was successful in achieving remission. Their vulval lichen sclerosus was subsequently able to be maintained with topical corticosteroid treatment.

  2. TIR-1 carbon dioxide laser system for fusion

    NASA Astrophysics Data System (ADS)

    Adamovich, V. A.; Anisimov, V. N.; Afonin, E. A.; Baranov, V. Iu.; Borzenko, V. L.; Kozochkin, S. M.; Maliuta, D. D.; Satov, Iu. A.; Sebrant, A. Iu.; Smakovski, Iu. B.

    1980-03-01

    The paper examines the TIR-1 carbon dioxide laser system for fusion. The current efforts are concentrated on (1) the microsecond laser pulse plasma heating in solenoids and theta pinches, and (2) nanosecond CO2 laser utilization for inertial confinement fusion. The TIR-1 system was designed to develop nanosecond CO2 laser technology and to study laser-target interaction at 10 microns. This system consists of an oscillator-preamplifier that produces about 1-nsec laser pulse with an energy contrast ratio of 1 million, a large triple-pass amplifier, and a target chamber with diagnostic equipment.

  3. Ultraviolet radiation induced discharge laser

    DOEpatents

    Gilson, Verle A.; Schriever, Richard L.; Shearer, James W.

    1978-01-01

    An ultraviolet radiation source associated with a suitable cathode-anode electrode structure, disposed in a gas-filled cavity of a high pressure pulsed laser, such as a transverse electric atmosphere (TEA) laser, to achieve free electron production in the gas by photoelectric interaction between ultraviolet radiation and the cathode prior to the gas-exciting cathode-to-anode electrical discharge, thereby providing volume ionization of the gas. The ultraviolet radiation is produced by a light source or by a spark discharge.

  4. Aesthetic Depigmentation of Gingival Smoker's Melanosis Using Carbon Dioxide Lasers

    PubMed Central

    Monteiro, Luis Silva; Costa, José Adriano; da Câmara, Marco Infante; Albuquerque, Rui; Martins, Marco; Pacheco, José Júlio; Salazar, Filomena; Figueira, Fernando

    2015-01-01

    Melanic pigmentation results from melanin produced by the melanocytes present in the basal layer of the oral epithelium. One of the most common causes of oral pigmentation is smoker melanosis, a condition associated with the melanocyte stimulation caused by cigarette smoke. This paper aims to illustrate the use of a carbon dioxide laser in the removal of the gingival melanic pigmentation for aesthetic reasons in a 27-year-old female patient with history of a smoking habit. The carbon dioxide laser vaporisation was performed on the gingival mucosa with effective and quick results and without any complications or significant symptoms after the treatment. We conclude that a carbon dioxide laser could be a useful, effective, and safe instrument to treat the aesthetic complications caused by oral smoker melanosis. PMID:25954535

  5. Characteristic measurements of silicon dioxide aerogel plasmas generated in a Planckian radiation environment

    SciTech Connect

    Dong Quanli; Wang Shoujun; Li Yutong; Zhang Yi; Zhao Jing; Wei Huigang; Shi Jianrong; Zhao Gang; Zhang Jiyan; Gu Yuqiu; Ding Yongkun; Wen Tianshu; Zhang Wenhai; Hu Xin; Liu Shenye; Zhang Lin; Tang Yongjian; Zhang Baohan; Zheng Zhijian; Nishimura, Hiroaki

    2010-01-15

    The temporally and spatially resolved characteristics of silicon dioxide aerogel plasmas were studied using x-ray spectroscopy. The plasma was generated in the near-Planckian radiation environment within gold hohlraum targets irradiated by laser pulses with a total energy of 2.4 kJ in 1 ns. The contributions of silicon ions at different charge states to the specific components of the measured absorption spectra were also investigated. It was found that each main feature in the absorption spectra of the measured silicon dioxide aerogel plasmas was contributed by two neighboring silicon ionic species.

  6. A high-pressure carbon dioxide gasdynamic laser

    NASA Technical Reports Server (NTRS)

    Kuehn, D. M.

    1973-01-01

    A carbon dioxide gasdynamic laser was operated over a range of reservoir pressure and temperature, test-gas mixture, and nozzle geometry. A significant result is the dominant influence of nozzle geometry on laser power at high pressure. High reservoir pressure can be effectively utilized to increase laser power if nozzle geometry is chosen to efficiently freeze the test gas. Maximum power density increased from 3.3 W/cu cm of optical cavity volume for an inefficient nozzle to 83.4 W/cu cm at 115 atm for a more efficient nozzle. Variation in the composition of the test gas also caused large changes in laser power output. Most notable is the influence of the catalyst (helium or water vapor) that was used to depopulate the lower vibrational state of the carbon dioxide. Water caused an extreme deterioration of laser power at high pressure (100 atm), whereas, at low pressure the laser for the two catalysts approached similar values. It appears that at high pressure the depopulation of the upper laser level of the carbon dioxide by the water predominates over the lower state depopulation, thus destroying the inversion.

  7. Superpulsed carbon dioxide laser: an update on cutaneous surgical applications

    NASA Astrophysics Data System (ADS)

    Wheeland, Ronald G.

    1990-06-01

    Superpulsing the carbon dioxide laser allows delivery of high energy pulses separated by short pauses during which tissue cooling can occur.1 This new technology can provide several important advantages in cutaneous surgery over similar procedures performed with conventional continuous discharge carbon dioxide laser systems. In the excisional mode, there is a two-thirds reduction in thermal necrosis of the wound edge.2 This should translate into more rapid healing3 and increased rate of gain in tensile strength. In the vaporizational mode, precise, superficial and bloodless ablation of multiple benign appendigeal tumors is possible with less thermal damage yielding excellent cosmetic results. The establishment through additional research of accurate laser parameters, pulse duration, peak energy levels, and frequency of pulses, will help improve the specificity of the laser-tissue interaction to provide even better surgical results.

  8. Treatment of digital myxoid cysts with carbon dioxide laser vaporization.

    PubMed

    Huerter, C J; Wheeland, R G; Bailin, P L; Ratz, J L

    1987-07-01

    Digital myxoid cysts represent a relatively uncommon cutaneous disorder which have often proven refractory to conservative management. We report a series of ten patients with this condition who were effectively treated with carbon dioxide (CO2) laser vaporization. There has been no recurrence of cysts during a follow-up period ranging from 14 to 44 months.

  9. Optical radiation hazards of laser welding processes. Part II: CO2 laser.

    PubMed

    Rockwell, R J; Moss, C E

    1989-08-01

    There has been an extensive growth within the last five years in the use of high-powered lasers in various metalworking processes. The two types of lasers used most frequently for laser welding/cutting processes are the Neodymium-yttrium-aluminum-garnet (Nd:YAG) and the carbon dioxide (CO2) systems. When such lasers are operated in an open beam configuration, they are designated as a Class IV laser system. Class IV lasers are high-powered lasers that may present an eye and skin hazard under most common exposure conditions, either directly or when the beam has been diffusely scattered. Significant control measures are required for unenclosed (open beam), Class IV laser systems since workers may be exposed to scattered or reflected beams during the operation, maintenance, and service of these lasers. In addition to ocular and/or skin exposure hazards, such lasers also may present a multitude of nonlaser beam occupational concerns. Radiant energy measurements are reported for both the scattered laser radiation and the plasma-related plume radiations released during typical high-powered CO2 laser-target interactions. In addition, the application of the nominal hazard zone (NHZ) and other control measures also are discussed with special emphasis on Class IV industrial CO2 laser systems. PMID:2508455

  10. Radiative heat transfer in porous uranium dioxide

    SciTech Connect

    Hayes, S.L.

    1992-12-01

    Due to low thermal conductivity and high emissivity of UO{sub 2}, it has been suggested that radiative heat transfer may play a significant role in heat transfer through pores of UO{sub 2} fuel. This possibility was computationally investigated and contribution of radiative heat transfer within pores to overall heat transport in porous UO{sub 2} quantified. A repeating unit cell was developed to model approximately a porous UO{sub 2} fuel system, and the heat transfer through unit cells representing a wide variety of fuel conditions was calculated using a finite element computer program. Conduction through solid fuel matrix as wekk as pore gas, and radiative exchange at pore surface was incorporated. A variety of pore compositions were investigated: porosity, pore size, shape and orientation, temperature, and temperature gradient. Calculations were made in which pore surface radiation was both modeled and neglected. The difference between yielding the integral contribution of radiative heat transfer mechanism to overall heat transport. Results indicate that radiative component of heat transfer within pores is small for conditions representative of light water reactor fuel, typically less than 1% of total heat transport. It is much larger, however, for conditions present in liquid metal fast breeder reactor fuel; during restructuring of this fuel type early in life, the radiative heat transfer mode was shown to contribute as much as 10-20% of total heat transport in hottest regions of fuel.

  11. 21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Ear, nose, and throat microsurgical carbon dioxide..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear,...

  12. 21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Ear, nose, and throat microsurgical carbon dioxide..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear,...

  13. 21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Ear, nose, and throat microsurgical carbon dioxide..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear,...

  14. Effects of radiation on laser diodes.

    SciTech Connect

    Phifer, Carol Celeste

    2004-09-01

    The effects of ionizing and neutron radiation on the characteristics and performance of laser diodes are reviewed, and the formation mechanisms for nonradiative recombination centers, the primary type of radiation damage in laser diodes, are discussed. Additional topics include the detrimental effects of aluminum in the active (lasing) volume, the transient effects of high-dose-rate pulses of ionizing radiation, and a summary of ways to improve the radiation hardness of laser diodes. Radiation effects on laser diodes emitting in the wavelength region around 808 nm are emphasized.

  15. Carbon dioxide laser resurfacing with fast recovery.

    PubMed

    Chajchir, Abel; Benzaquen, Iliana

    2005-01-01

    ABTRACT: Long sun exposure, in addition to ozone layer damage, produces structural damase to the normal skin. Injury to the dermal collagen and elastic fiber results in facial wrinkles. Photodamage to the skin is one of the most common sources of concern for patients visiting the plastic surgeon or dermatologist. Over the years, many alternative solutions have been developed. CO2 laser treatment is one of the alternatives bringing unique benefits and satisfactory results for both patient and surgeons. However, the initial problems of emotional discomfort, prolonged postoperative recovery and delayed return to normal activities have made patients reluctant to accept this method. This article discusses single-pass CO2 laser resurfacing with lower energy. Also, it proposes a technique that does not use wet gauze to remove the surface of the skin. This technique is applied in combination with an intensive skin care treatment. Different authors propose a single pass of CO2 laser with excellent results. With the reported method, identical long-lasting benefits are achieved, but the post-operative time is shorter.

  16. Carbon dioxide laser oral safety parameters for teeth

    SciTech Connect

    Powell, G.L.; Whisenant, B.K.; Morton, T.H. )

    1990-01-01

    The carbon dioxide laser is used in the oral cavity for a variety of procedures. Although the procedures may not involve the teeth directly, precaution should be exercised to preserve their integrity. The results of this study indicate that the most limiting parameter for oral use of the CO{sub 2} laser is damage to the enamel surface, which could be inflicted with as little as 5 W for 0.2 second and a 1 mm beam. Care should be exercised to prevent inadvertent damage to the surface enamel of teeth even at very low energy levels.

  17. Neutron radiation characteristics of plutonium dioxide fuel

    NASA Technical Reports Server (NTRS)

    Taherzadeh, M.

    1972-01-01

    The major sources of neutrons from plutonium dioxide nuclear fuel are considered in detail. These sources include spontaneous fission of several of the Pu isotopes, (alpha, n) reactions with low Z impurities in the fuel, and (alpha, n) reactions with O-18. For spontaneous fission neutrons a value of (1.95 + or - 0.07) X 1,000 n/s/g PuO2 is obtained. The neutron yield from (alpha, n) reactions with oxygen is calculated by integrating the reaction rate equation over all alpha-particle energies and all center-of-mass angles. The results indicate a neutron emission rate of (1.14 + or - 0.26) X 10,000 n/s/g PuO2. The neutron yield from (alpha, n) reactions with low Z impurities in the fuel is presented in tabular form for one part part per million of each impurity. The total neutron yield due to the combined effects of all the impurities depends upon the fractional weight concentration of each impurity. The total neutron flux emitted from a particular fuel geometry is estimated by adding the neutron yield due to the induced fission to the other neutron sources.

  18. Efficiency of Carbon Dioxide Fractional Laser in Skin Resurfacing

    PubMed Central

    Petrov, Andrej

    2016-01-01

    AIM: The aim of the study was to confirm the efficiency and safety of the fractional CO2 laser in skin renewal and to check the possibility of having a synergistic effect in patients who besides carbon dioxide laser are treated with PRP (platelet-rich plasma) too. MATERIAL AND METHODS: The first group (Examined Group 1 or EG1) included 107 patients treated with fractional CO2 laser (Lutronic eCO2) as mono-therapy. The second group (Control Group or CG) covered 100 patients treated with neither laser nor plasma in the same period but subjected to local therapy with drugs or other physio-procedures under the existing protocols for treatment of certain diseases. The third group (Examined Group 2 or EG2) treated 25 patients with combined therapy of CO2 laser and PRP in the treatment of facial rejuvenation or treatment of acne scars. RESULTS: Patient’s satisfaction, in general, is significantly greater in both examined groups (EG1 and EG2) (p < 0.001). It was found the significant difference between control and examined group from the treatment in acne scar (Fisher exact two tailed p < 0.001). Patients satisfaction with the treatment effect in rejuvenation of the skin is significant (χ2 = 39.41; df = 4; p < 0.001). But, patients satisfaction from the treatment with HPV on the skin was significantly lower in examined group (treated with laser), p = 0.0002. CONCLUSION: Multifunctional fractional carbon dioxide laser used in treatment of patients with acne and pigmentation from acne, as well as in the treatment of scars from different backgrounds, is an effective and safe method that causes statistically significant better effect of the treatment, greater patients’ satisfaction, minimal side effects and statistically better response to the therapy, according to assessments by the patient and the therapist. PMID:27335599

  19. 21 CFR 874.4500 - Ear, nose, and throat microsurgical carbon dioxide laser.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... laser. 874.4500 Section 874.4500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND..., nose, and throat microsurgical carbon dioxide laser. (a) Identification. An ear, nose, and throat microsurgical carbon dioxide laser is a device intended for the surgical excision of tissue from the ear,...

  20. Theoretical and Experimental studies on CH3OH THz Laser Pumped by Pulse Carbon Dioxide Laser

    NASA Astrophysics Data System (ADS)

    Fei, Fei; Jing, Wang; Zhaoshuo, Tian; Yanchao, Zhang; Shiyou, Fu; Qi, Wang

    2011-02-01

    In this paper, according to the molecular structure and vibration mode of micro-asymmetric gyroscope CH3OH molecule, dynamic process of optically pumped Terahertz laser is analyzed theoretically. The rate equation models based on three level systems are given according to the theory of typical laser rate equation. The output THz pulsed laser waveform is obtained by solving the rate equation model. An all-metal Terahertz laser pumped by RF waveguide carbon dioxide laser is designed with CH3OH as its working gas. The pulsed Terahertz laser output is obtained. The waveform and repetition frequency of the optically pumped laser are measured in the experiments. The Terahertz laser designed does not need water cooling system. It also has the advantages of simple structure and small size.

  1. Enamel fusion using a carbon dioxide laser: A technique for sealing pits and fissures

    SciTech Connect

    Walsh, L.J.; Perham, S.J. )

    1991-05-01

    The well-established enhanced resistance of lased enamel to demineralization is the basis for clinical application of the carbon dioxide laser to caries prevention. This in vitro study examined the effect of focused infrared laser radiation on sound enamel and early pit and fissure caries. Low power levels (2-5 W) induced localized melting and resolidification of enamel with little surface destruction. For sound fissures, fusion of enamel from the lateral walls of the fissure eliminated the fissure space, providing a sealant effect; while in carious fissures, carious enamel was vaporized and adjacent sound enamel fused to partially eliminate the defect. The technique for enamel fusion using CO2 lasers has potential application for sealing pits and fissures and producing physicochemical alterations in enamel which may have preventive benefits.

  2. Interactions of intense laser radiation with plasma

    NASA Astrophysics Data System (ADS)

    Key, M. H.

    1981-04-01

    The dominant physical processes involved in the interaction of intense laser radiation with plasma are discussed with emphasis on their dependence on the wavelength of the laser radiation. Hydrodynamic pressure resulting from these interactions, acceleration of spherical shell targets, and fluid instability associated with the acceleration are discussed with reference to compression of plasma in laser driven implosions. Experimental data are presented to illustrate the various phenomena.

  3. Removal of oral cavity leiomyoma with carbon dioxide laser.

    PubMed

    Janas, Anna; Grzesiak-Janas, Grazyna; Sporny, Stanislaw

    2008-01-01

    Myoma is a nonmalignant neoplasm rarely found in the oral cavity and even more rarely mentioned in the world's dental or surgical literature. Not one case of oral cavity leiomyoma has been reported in Poland. This article describes a case of leiomyoma of the oral cavity in a 51-year-old patient. To remove the tumor, a carbon dioxide laser was used. Because of the method used, perioperative bleeding was avoided, which enabled better visibility of the surgical area and minimized duration of the operation. The postoperative wound did not require sutures, and healing occurred without complications. PMID:18551205

  4. Improvement of Microstomia in Scleroderma after Carbon Dioxide Laser Treatment.

    PubMed

    Bennani, Imane; Lopez, Raphael; Bonnet, Delphine; Prevot, Gregoire; Constantin, Arnaud; Chauveau, Dominique; Paul, Carle; Bulai Livideanu, Cristina

    2016-01-01

    Limited mouth opening (LMO) is a frequent complication of systemic sclerosis (SS). Its management is complex and there are limited treatment options. We report four patients with SS and severe LMO [interincisal distance (IID) <30 mm] treated with pulsed carbon dioxide (CO2) laser. Pulsed CO2 laser treatment of the white lips was performed after all patients had signed a written informed consent in the absence of alternative treatment. Treatment was carried out under locoregional anaesthesia using a Sharplan 30C CO2 laser in the Silk Touch® resurfacing mode. One to three laser sessions were performed at intervals of 8-12 months between sessions. Assessments were performed at 3 and 12 months with measurement of the IID using a ruler, calculation of the Mouth Handicap in Systemic Sclerosis (MHISS) scale and global evaluation by the patients. Adverse events were also reported. In all four patients, an improvement in IID occurred 3 months after the first session with a mean gain of +5 mm (range: 2-7). At 12 months, a mean gain of +8.5 mm (range: 7-10) in IID was observed. The MHISS score decreased by a mean of •14 (range: 11-17). All patients showed improvement of lip flexibility or mouth opening, allowing better phonation and mastication and easier dental care. Adverse effects were transient erythema and/or dyschromia. CO2 laser appears to be effective and well tolerated in the improvement of LMO in SS. PMID:27403126

  5. The NASA high power carbon dioxide laser: A versatile tool for laser applications

    NASA Technical Reports Server (NTRS)

    Lancashire, R. B.; Alger, D. L.; Manista, E. J.; Slaby, J. G.; Dunning, J. W.; Stubbs, R. M.

    1976-01-01

    A closed-cycle, continuous wave, carbon dioxide high power laser has been designed and fabricated to support research for the identification and evaluation of possible high power laser applications. The device is designed to generate up to 70 kW of laser power in annular shape beams from 1 to 9 cm in diameter. Electric discharge, either self sustained or electron beam sustained, is used for excitation. This laser facility provides a versatile tool on which research can be performed to advance the state-of-the-art technology of high power CO2 lasers in such areas as electric excitation, laser chemistry, and quality of output beams. The facility provides a well defined, continuous wave beam for various application experiments, such as propulsion, power conversion, and materials processing.

  6. Fractional Carbon Dioxide Laser in Treatment of Acne Scars

    PubMed Central

    Petrov, Andrej; Pljakovska, Vesna

    2016-01-01

    BACKGROUND: Scars appear as a result of skin damage during the process of the skin healing. There are two types of acne scars, depending on whether there is a loss or accumulation of collagen: atrophic and hypertrophic. In 80-90% it comes to scars with loss of collagen compared to smaller number of hypertrophic scars and keloids. AIM: The aim of the study was to determine efficiency and safety of fractional carbon dioxide laser in the treatment of acne scars. MATERIAL AND METHODS: The study was carried out in Acibadem Sistina Clinical Hospital, Skopje at the Department of Dermatovenerology, with a total of 40 patients treated with fractional carbon dioxide laser (Lutronic eCO2). The study included patients with residual acne scars of a different type. RESULTS: Comedogenic and papular acne in our material were proportionately presented in 50% of cases, while the other half were the more severe clinical forms of acne - pustular inflammatory acne and nodulocystic acne that leave residual lesions in the form of second, third and fourth grade of scars. CONCLUSION: The experiences of our work confirm the world experiences that the best result with this method is achieved in dotted ice pick or V-shaped acne scars. PMID:27275326

  7. Laser-induced nucleation of carbon dioxide bubbles.

    PubMed

    Ward, Martin R; Jamieson, William J; Leckey, Claire A; Alexander, Andrew J

    2015-04-14

    A detailed experimental study of laser-induced nucleation (LIN) of carbon dioxide (CO2) gas bubbles is presented. Water and aqueous sucrose solutions supersaturated with CO2 were exposed to single nanosecond pulses (5 ns, 532 nm, 2.4-14.5 MW cm(-2)) and femtosecond pulses (110 fs, 800 nm, 0.028-11 GW cm(-2)) of laser light. No bubbles were observed with the femtosecond pulses, even at high peak power densities (11 GW cm(-2)). For the nanosecond pulses, the number of bubbles produced per pulse showed a quadratic dependence on laser power, with a distinct power threshold below which no bubbles were observed. The number of bubbles observed increases linearly with sucrose concentration. It was found that filtering of solutions reduces the number of bubbles significantly. Although the femtosecond pulses have higher peak power densities than the nanosecond pulses, they have lower energy densities per pulse. A simple model for LIN of CO2 is presented, based on heating of nanoparticles to produce vapor bubbles that must expand to reach a critical bubble radius to continue growth. The results suggest that non-photochemical laser-induced nucleation of crystals could also be caused by heating of nanoparticles.

  8. INDUSTRIAL EFFLUENT TREATMENT USING IONIZING RADIATION COMBINED TO TITANIUM DIOXIDE

    SciTech Connect

    Duarte, C.L.; Oikawa, H.; Mori, M.N.; Sampa, M.H.O.

    2004-10-04

    The Advanced Oxidation Process (AOP) with OH radicals are the most efficient to mineralize organic compounds, and there are various methods to generate OH radicals as the use of ozone, hydrogen peroxide and ultra-violet radiation and ionizing radiation. The irradiation of aqueous solutions with high-energy electrons results in the excitation and ionizing of the molecules and rapid (10{sup -14} - 10{sup -9} s) formation of reactive intermediates. These reactive species will react with organic compounds present in industrial effluent inducing their decomposition. Titanium dioxide (TiO{sub 2}) catalyzed photoreaction is used to remove a wide range of pollutants in air and water media, combined to UV/VIS light, FeO{sub 2}, and H{sub 2}O{sub 2}, but as far as known there is no report on the combination with ionizing radiation. In some recent studies, the removal of organic pollutants in industrial effluent, such as Benzene, Toluene, and Xylene from petroleum production using ionizing radiation was investigated. It has been ob served that none of the methods can be used individually in wastewater treatment applications with good economics and high degree of energy efficiency. In the present work, the efficiency of ionizing radiation in presence of TiO{sub 2} to treat industrial effluent was evaluated. The main aim to combine these technologies is to improve the efficiency for very hard effluents and to reduce the processing cost for future implementation to large-scale design.

  9. Advanced optic fabrication using ultrafast laser radiation

    NASA Astrophysics Data System (ADS)

    Taylor, Lauren L.; Qiao, Jun; Qiao, Jie

    2016-03-01

    Advanced fabrication and finishing techniques are desired for freeform optics and integrated photonics. Methods including grinding, polishing and magnetorheological finishing used for final figuring and polishing of such optics are time consuming, expensive, and may be unsuitable for complex surface features while common photonics fabrication techniques often limit devices to planar geometries. Laser processing has been investigated as an alternative method for optic forming, surface polishing, structure writing, and welding, as direct tuning of laser parameters and flexible beam delivery are advantageous for complex freeform or photonics elements and material-specific processing. Continuous wave and pulsed laser radiation down to the nanosecond regime have been implemented to achieve nanoscale surface finishes through localized material melting, but the temporal extent of the laser-material interaction often results in the formation of a sub-surface heat affected zone. The temporal brevity of ultrafast laser radiation can allow for the direct vaporization of rough surface asperities with minimal melting, offering the potential for smooth, final surface quality with negligible heat affected material. High intensities achieved in focused ultrafast laser radiation can easily induce phase changes in the bulk of materials for processing applications. We have experimentally tested the effectiveness of ultrafast laser radiation as an alternative laser source for surface processing of monocrystalline silicon. Simulation of material heating associated with ultrafast laser-material interaction has been performed and used to investigate optimized processing parameters including repetition rate. The parameter optimization process and results of experimental processing will be presented.

  10. Terahertz radiation from a laser plasma filament

    SciTech Connect

    Wu, H.-C.; Meyer-ter-Vehn, J.; Ruhl, H.; Sheng, Z.-M.

    2011-03-15

    By the use of two-dimensional particle-in-cell simulations, we clarify the terahertz (THz) radiation mechanism from a plasma filament formed by an intense femtosecond laser pulse. The nonuniform plasma density of the filament leads to a net radiating current for THz radiation. This current is mainly located within the pulse and the first cycle of the wakefield. As the laser pulse propagates, a single-cycle and radially polarized THz pulse is constructively built up forward. The single-cycle shape is mainly due to radiation damping effect.

  11. Pulsed laser radiation therapy of skin tumors

    SciTech Connect

    Kozlov, A.P.; Moskalik, K.G.

    1980-11-15

    Radiation from a neodymium laser was used to treat 846 patients with 687 precancerous lesions or benign tumors of the skin, 516 cutaneous carcinomas, 33 recurrences of cancer, 51 melanomas, and 508 metastatic melanomas in the skin. The patients have been followed for three months to 6.5 years. No relapses have been observed during this period. Metastases to regional lymph nodes were found in five patients with skin melanoma. Pulsed laser radiation may be successfully used in the treatment of precancerous lesions and benign tumors as well as for skin carcinoma and its recurrences, and for skin melanoma. Laser radiation is more effective in the treatment of tumors inaccessible to radiation therapy and better in those cases in which surgery may have a bad cosmetic or even mutilating effect. Laser beams can be employed in conjunction with chemo- or immunotherapy.

  12. Observations on pulpal response to carbon dioxide laser drilling of dentine in healthy human third molars.

    PubMed

    Nair, P N R; Baltensperger, M; Luder, H U; Eyrich, G K H

    2005-01-01

    Preservation of pulpal health is the primary prerequisite for successful application of laser systems in the hard tissue management of vital teeth. The purpose of this study was to investigate the short and long-term pulpal effects to cavity preparations in healthy human teeth using carbon dioxide (CO2) laser. A total of seven, healthy, third molars that were scheduled to be removed due to space problems were used. After the laser drilling, the occlusal cavities were closed temporarily, and the teeth were extracted 7 days (n=5) and 3 months (n=2) after the operation. The specimens were fixed, decalcified, subdivided and processed for light and transmission electron microscopy. Seven days postoperatively all the five teeth that had been irradiated with the CO2 laser did not reveal any pathological changes in the pulpo-dentine complex. Three months postoperatively the two teeth that were prepared with the laser showed subtle but distinct apposition of tertiary dentine that was lined with intact odontoblasts. One of the specimens at 3 months revealed the presence of a mild, but very circumscribed, pulpal infiltration of chronic inflammatory cells subjacent to the cavity preparation. The latter is unlikely to be due to a direct effect of the laser irradiation but a possible consequence of microleakage of oral antigens and/or other tissue-irritating molecules through the temporary restoration and the remaining dentine thickness (RDT). Although these preliminary histological results suggest that the CO2 laser under investigation induced only minimal response of the dentine-pulp complex when used as a hard-tissue drilling tool, with specific energy settings, pulse duration within thermal relaxation time and emitting radiations at 9.6 microm of wavelength, larger clinical trials involving various types of teeth are necessary to reach definite conclusions for large-scale clinical application of the laser device. PMID:15647971

  13. EFFECTS OF LASER RADIATION ON MATTER: Spectrum of the barium atom in a laser radiation field

    NASA Astrophysics Data System (ADS)

    Bondar', I. I.; Suran, V. V.

    1990-08-01

    An experimental investigation was made of the influence of a laser radiation field on the spectrum of barium atoms. The investigation was carried out by the method of three-photon ionization spectroscopy using dye laser radiation (ω = 14 800-18 700 cm - 1). The electric field intensity of the laser radiation was 103-106 V/cm. This laser radiation field had a strong influence on a number of bound and autoionizing states. The nature of this influence depended on the ratio of the excitation frequencies of bound and autoionizing states.

  14. Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2015-07-01

    We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.

  15. Uncertainties in carbon dioxide radiative forcing in atmospheric general circulation models.

    PubMed

    Cess, R D; Zhang, M H; Potter, G L; Barker, H W; Colman, R A; Dazlich, D A; Del Genio, A D; Esch, M; Fraser, J R; Galin, V; Gates, W L; Hack, J J; Ingram, W J; Kiehl, J T; Lacis, A A; Le Treut, H; Li, Z X; Liang, X Z; Mahfouf, J F; McAvaney, B J; Meleshko, V P; Morcrette, J J; Randall, D A; Roeckner, E; Royer, J F; Sokolov, A P; Sporyshev, P V; Taylor, K E; Wang, W C; Wetherald, R T

    1993-11-19

    Global warming caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

  16. Uncertainties in Carbon Dioxide Radiative Forcing in Atmospheric General Circulation Models

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Zhang, M.-H.; Potter, G. L.; Gates, W. L.; Taylor, K. E.; Barker, H. W.; Colman, R. A.; Fraser, J. R.; McAvaney, B. J.; Dazlich, D. A.; Randall, D. A.; DelGenio, A. D.; Lacis, A. A.; Esch, M.; Roeckner, E.; Galin, V.; Hack, J. J.; Kiehl, J. T.; Ingram, W. J.; LeTreut, H.

    1993-01-01

    Global warming, caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.

  17. Uncooled receivers for CO2 laser radiation

    NASA Astrophysics Data System (ADS)

    Granovskii, A. B.; Iakovlev, V. A.

    1986-01-01

    Published data on low-inertia, uncooled, single-element and matrix-type radiation receivers that have a high degree of reliability and are immune from interference from various external sources are systematically summarized. Three basic types of receivers are examined: photonic receivers, thermal receivers, and receivers based on wave interaction. Principal attention is given to the CO2 laser radiation receiver.

  18. The use of the carbon dioxide laser in head and neck lymphangioma.

    PubMed

    White, B; Adkins, W Y

    1986-01-01

    The carbon dioxide laser has been used to treat various lesions of the head and neck, ranging from carcinomas to hemangiomas, and even including tatoos. A search of the literature does not reveal any reports of the carbon dioxide laser being used to treat lymphangioma. This report discusses the efficacy of treating lymphangioma of the air and food passages with the carbon dioxide laser, and presents three patients who have been treated in this fashion-two for palliation and one for cure. PMID:2426548

  19. Testing Unruh Radiation with Ultraintense Lasers

    NASA Astrophysics Data System (ADS)

    Chen, Pisin; Tajima, Toshi

    1999-07-01

    We point out that using the state-of-the-art (or soon-to-be) intense electromagnetic pulses, violent accelerations that may be suitable for testing quantum field theory in curved spacetime can be realized through the interaction of a high-intensity laser with an electron. In particular, we demonstrate that the Unruh radiation is detectable, in principle, beyond the conventional radiation (most notably the Larmor radiation) background noise, by taking advantage of its specific dependence on the laser power and distinct character in spectral-angular distributions.

  20. [Laser radiations in medical therapy].

    PubMed

    Richand, P; Boulnois, J L

    1983-06-30

    The therapeutic effects of various types of laser beams and the various techniques employed are studied. Clinical and experimental research has shown that Helio-Neon laser beams are most effective as biological stimulants and in reducing inflammation. For this reasons they are best used in dermatological surgery cases (varicose ulcers, decubital and surgical wounds, keloid scars, etc.). Infrared diode laser beams have been shown to be highly effective painkillers especially in painful pathologies like postherpetic neuritis. The various applications of laser therapy in acupuncture, the treatment of reflex dermatologia and optic fibre endocavital therapy are presented. The neurophysiological bases of this therapy are also briefly described.

  1. Emitted radiation characteristics of plutonium dioxide radioisotope thermoelectric generators

    NASA Technical Reports Server (NTRS)

    Gingo, P. J.; Steyn, J. J.

    1971-01-01

    The nuclear and emitted radiation characteristics of the radioisotope elements and impurities in commercial grade plutonium dioxide are presented in detail. The development of the methods of analysis are presented. Radioisotope thermoelectric generators (RTG) of 1575, 3468 and 5679 thermal watts are characterized with respect to neutron and gamma photon source strength as well as spatial and number flux distribution. The results are presented as a function of detector position and light element contamination concentration for fuel age ranging from 'fresh' to 18 years. The data may be used to obtain results for given O-18 and Pu-236 concentrations. The neutron and gamma photon flux and dose calculations compare favorably with reported experimental values for SNAP-27.

  2. Experimental investigation of radiative thermal rectifier using vanadium dioxide

    SciTech Connect

    Ito, Kota; Nishikawa, Kazutaka; Iizuka, Hideo; Toshiyoshi, Hiroshi

    2014-12-22

    Vanadium dioxide (VO{sub 2}) exhibits a phase-change behavior from the insulating state to the metallic state around 340 K. By using this effect, we experimentally demonstrate a radiative thermal rectifier in the far-field regime with a thin film VO{sub 2} deposited on the silicon wafer. A rectification contrast ratio as large as two is accurately obtained by utilizing a one-dimensional steady-state heat flux measurement system. We develop a theoretical model of the thermal rectifier with optical responses of the materials retrieved from the measured mid-infrared reflection spectra, which is cross-checked with experimentally measured heat flux. Furthermore, we tune the operating temperatures by doping the VO{sub 2} film with tungsten (W). These results open up prospects in the fields of thermal management and thermal information processing.

  3. The NASA high-power carbon dioxide laser - A versatile tool for laser applications

    NASA Technical Reports Server (NTRS)

    Lancashire, R. B.; Alger, D. L.; Manista, E. J.; Slaby, J. G.; Dunning, J. W.; Stubbs, R. M.

    1977-01-01

    The NASA Lewis Research Center has designed and fabricated a closed-cycle, continuous wave (CW), carbon dioxide (CO2) high-power laser to support research for the identification and evaluation of possible high-power laser applications. The device is designed to generate up to 70 kW of laser power in annular-shape beams from 1 to 9 cm in diameter. Electric discharge, either self-sustained or electron-beam-sustained, is used for excitation. This laser facility can be used in two ways. First, it provides a versatile tool on which research can be performed to advance the state-of-the-art technology of high-power CO2 lasers in such areas as electric excitation, laser chemistry, and quality of output beams, all of which are important whether the laser application is government or industry oriented. Second, the facility provides a well-defined, continuous wave beam for various application experiments, such as propulsion, power conversion, and materials processing.

  4. Low-fluence carbon dioxide laser irradiation of lentigines

    SciTech Connect

    Dover, J.S.; Smoller, B.R.; Stern, R.S.; Rosen, S.; Arndt, K.A.

    1988-08-01

    Low-fluence carbon dioxide (CO2) laser irradiation of skin has previously been shown to induce damage limited primarily to the epidermis. To evaluate whether this technique was therapeutically effective for pigmented epidermal lesions, ten lentigines caused by methoxsalen and ultraviolet light therapy were treated in one patient using the CO2 laser at fluences ranging from 3.0 to 7.7 J/cm2 for 0.1-s exposures with 4.5-mm spot size. Based on substantial clearing in seven of ten lesions treated, 146 solar lentigines were treated in five patients at fluences of 3.0, 3.7, or 4.4 J/cm2. Biopsies were performed on a total of 30 lesions immediately and 24 hours, seven days, and six weeks after irradiation. Of 125 lesions followed up clinically for six weeks, 12 cleared completely, 81 lightened substantially, and 28 remained unchanged. Only two demonstrated atrophic change. Hyperpigmentation or hypopigmentation did not occur. All lesions that improved had been treated at 3.7 or 4.4 J/cm2. Immediate histologic injury consisted of vacuolar and spindly change and subsequent vesiculation limited to the basilar epidermis. Twenty-four hours later there was epidermal necrosis with regeneration, 0.1 mm of dermal basophilia and stromal condensation, and a mild inflammatory infiltrate. These alterations were dose-dependent, with near complete epidermal necrosis and superficial dermal involvement at the highest fluence, and only focal epidermal necrosis at the lowest. At seven days, epidermal regeneration was complete with traces of melanin remaining in keratinocytes. Melanophages first appeared at seven days and persisted at six weeks, by which time the inflammatory infiltrate had cleared. No lentiginous proliferation was evident and epidermal pigmentation had become normal. Low-fluence CO2 laser irradiation is an effective means of damaging the epidermis with only minimal dermal change.

  5. Laser synchrotron radiation and beam cooling

    SciTech Connect

    Esarey, E.; Sprangle, P.; Ting, A.

    1995-12-31

    The interaction of intense {approx_gt} 10{sup 18} W/cm{sup 2}, short pulse ({approx_lt} 1 ps) lasers with electron beams and plasmas can lead to the generation of harmonic radiation by several mechanisms. Laser synchrotron radiation may provide a practical method for generating tunable, near monochromatic, well collimated, short pulse x-rays in compact, relatively inexpensive source. The mechanism for the generation of laser synchrotron radiation is nonlinear Thomson scattering. Short wavelengths can be generated via Thomson scattering by two methods, (i) backscattering from relativistic electron beams, in which the radiation frequency is upshifted by the relativistic factor 4{gamma}{sup 2}, and (ii) harmonic scattering, in which a multitude of harmonics are generated with harmonic numbers extending out to the critical harmonic number nc{approx_equal}a{sub 0}{sup 3} {much_gt} 1, where a{sub 0} {approx_equal}10{sup -9}{lambda}I{sup 1/2}, {lambda} is the laser wavelength in {mu}m and I is the laser intensity in W/cm{sup 2}. Laser synchrotron sources are capable of generating short ({approx_lt} ps) x-ray pulses with high peak flux ({approx_gt} 10{sup 21} photons/s) and brightness ({approx_gt}{sup 19} photons/s-mm{sup 2}-mrad{sup 2} 0.1%BW. As the electron beam radiates via Thomson scattering, it can subsequently be cooled, i.e., the beam emittance and energy spread can be reduced. This cooling can occur on rapid ({approximately} ps) time scales. In addition, electron distributions with sufficiently small axial energy spreads can be used to generate coherent XUV radiation via a laser-pumped FEL mechanism.

  6. Clinical study on 71 anorectal cases treated by carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Li, Gui-hua

    1993-03-01

    This paper describes the effective result of carbon dioxide laser on type I and II internal hemorrhoids, mixed hemorrhoids, anal fissure or fistula, etc. At present, simple hemorrhoidectomy is less acceptable to patients for its excessive bleeding and severe pain during and after the operation. Therefore, the results of 71 anorectal cases of hemorrhoidectomy using carbon dioxide laser have been observed in our hospital. The rates of effective treatment and cure were 100% and 94.3%, respectively.

  7. Low-power laser induced metal-insulator transition in gold::vanadium dioxide nanoarrays

    NASA Astrophysics Data System (ADS)

    Ferrara, Davon W.; Macquarrie, Evan R.; Nag, Joyeeta; Haglund, Richard F.

    2010-10-01

    Vanadium dioxide (VO2) is a strongly-correlated electron material with a well-known semiconductor-to-metal transition (SMT) that can be induced thermally, optically, or electrically. By coating lithographically prepared arrays of gold nanoparticles (NPs) of diameter 140 nm with a 60 nm thick film of VO2 by pulsed laser deposition, hybrid Au::VO2 structures were created. Due to the sensitivity of the Au particle-plasmon resonance (PPR), a temperature dependent shift in the PPR can be generated by switching the VO2 from one phase to another, creating a tunable plasmonic metamaterial. To study the low-power switching characteristics of these structures, transient absorption measurements were made using a mechanically shuttered 785 nm pump laser, corresponding to the PPR resonance of the Au NPs, and 1550 nm CW probe. Results show that the presence of Au NPs significantly lowers the threshold laser power required to induce the SMT. Measurements on arrays of different grating constants (350 nm and 500 nm) support the hypothesis that the particles are acting as ``nano-radiators'' that absorb and redeposit thermal energy by scattering light back into the film. Finite element modeling was performed to better understand the complex thermodynamics of the structure.

  8. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Microwave generation in an optical breakdown plasma created by modulated laser radiation

    NASA Astrophysics Data System (ADS)

    Antipov, A. A.; Grasyuk, Arkadii Z.; Losev, Leonid L.; Soskov, V. I.

    1990-06-01

    It was established that when laser radiation, intensity modulated at a frequency of 2.2 GHz, interacted with an optical breakdown plasma which it had created, a microwave component appeared in the thermal emf of the plasma. The amplitude of the microwave thermal emf reached 0.7 V for a laser radiation intensity of 6 GW/cm2. Laser radiation with λL = 1.06 μm was converted to the microwave range with λmω = 13 cm in the optical breakdown plasma. A microwave signal power of ~ 0.5 W was obtained from a laser power of ~ 5 MW.

  9. Low Level Laser Therapy: laser radiation absorption in biological tissues

    NASA Astrophysics Data System (ADS)

    Di Giacomo, Paola; Orlando, Stefano; Dell'Ariccia, Marco; Brandimarte, Bruno

    2013-07-01

    In this paper we report the results of an experimental study in which we have measured the transmitted laser radiation through dead biological tissues of various animals (chicken, adult and young bovine, pig) in order to evaluate the maximum thickness through which the power density could still produce a reparative cellular effect. In our experiments we have utilized a pulsed laser IRL1 ISO model (based on an infrared diode GaAs, λ=904 nm) produced by BIOMEDICA s.r.l. commonly used in Low Level Laser Therapy. Some of the laser characteristics have been accurately studied and reported in this paper. The transmission results suggest that even with tissue thicknesses of several centimeters the power density is still sufficient to produce a cell reparative effect.

  10. Carbon dioxide (CO2) laser treatment of cutaneous papillomas in a common snapping turtle, Chelydra serpentina.

    PubMed

    Raiti, Paul

    2008-06-01

    Carbon dioxide (CO2) laser was used to treat multiple cutaneous papillomas on an adult female common snapping turtle, Chelydra serpentina serpentina. A combination of excisional and ablative techniques provided excellent intraoperative visibility and postoperative results due to the laser's unique ability to incise and vaporize soft tissue. PMID:18634218

  11. Mechanism of skin resurfacing using the ultrapulse carbon dioxide laser: animal study

    NASA Astrophysics Data System (ADS)

    Yuan, Wei-Wei; Liu, Chun-Li; Lai, Huang-Wen; Yung, Chuan-Hong

    1998-11-01

    Ultrapulse carbon dioxide laser ablations of rabbit skin were investigated. Macroscopic, microscopic and electron microscopic appearances of the ablation sites were evaluated. Results showed that the effect of laser treatment was on the epidermis and the papillary dermis. All or some of the cell layers of epidermis were ablated degeneration took place in the papillary dermis. Wrinkles of the new epidermis were shallow and seldom. The new collagenous fibers were more elastic which made the skin tighter and few wrinkles. Results also demonstrated that ultrapulse carbon dioxide laser stimulated hairs to grow fast.

  12. Conversion of blackbody radiation into laser energy

    NASA Technical Reports Server (NTRS)

    Mcinville, R. M.; Hassan, H. A.

    1982-01-01

    By employing detailed kinetic models, three concepts which utilize a blackbody cavity for the conversion of solar energy into laser energy using a CO2 lasant are analyzed and compared. In the first, the blackbody radiation is used to excite flowing CO2 directly. The second and third employ a mixing laser concept with CO and N2 being the donor gases. The CO is optically pumped while thermal heating excites the N2. Blackbody temperatures ranging from 1500 deg K - 2500 deg K are considered. Based on calculated laser power output per unit flow rate of CO2, it appears that the N2-CO2 mixing laser is the most attractive system.

  13. LASCAT - DESIGN OF CATALYTIC MONOLITHS FOR CLOSED-CYCLE CARBON DIOXIDE LASERS

    NASA Technical Reports Server (NTRS)

    Guinn, K.

    1994-01-01

    Pulsed carbon dioxide lasers are useful in many areas, including aeronautics, space research, and weather monitoring. Most applications require a closed-cycle carbon dioxide laser, which is more portable and self-sustaining than an open-cycle system. Without a fresh carbon dioxide supply and provisions for byproduct disposal, the closed-cycle laser must recycle the carbon monoxide and oxygen gas produced by the lasing of carbon dioxide. The recombination of the carbon monoxide and oxygen gas byproducts to form a constant supply of carbon dioxide requires an active catalyst, which must be carefully designed to optimize laser performance in accordance with design requirements specific to the laser's application. LASCAT (Design of Catalytic Monoliths for Closed-Cycle Carbon Dioxide Lasers) aids in the design of the monolith catalyst by simulating the results of design decisions on the performance of the laser. In portable laser systems, considerations of size, weight, and cost are critical. LASCAT provides the opportunity for the designer to explore trade-offs between the catalyst activity, catalyst dimensions, monolith dimensions, pressure drop (a result of gas flow through the monolith), Oxygen gas conversion, and other variables. The program uses a flexible, simplified model of the monolith catalyst designed to determine the bulk-avarage gas temperature, composition, and pressure along its length. The user specifies values for the several parameters which define the catalyst's operating conditions, including monolith dimensions, gas inlet properties, thermal operation properties, and catalyst properties. LASCAT provides results which indicate whether the experimental design meets user-defined constraints such as limits on conversion rate, maximum gas temperature, and monolith weight. LASCAT is written in FORTRAN 77 and is designed for use with any text or character-based terminal or computer display. The program requires roughly 40 KB memory. LASCAT was developed

  14. Suggested state regulations for control fo radiation. Volume 2: Nonionizing radiation, lasers

    NASA Astrophysics Data System (ADS)

    Information is presented on classifying lasers into four classes is presented; defines what a laser product is; states requirements for medical surveillance for persons exposed to laser radiation; specifies requirements for registration of laser facilities, mobile lasers, and persons servicing lasers/systems.

  15. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron-positron pairs can be optimized by a suitable choice of the intensity ratio.

  16. Radiative trapping in intense laser beams

    NASA Astrophysics Data System (ADS)

    Kirk, J. G.

    2016-08-01

    The dynamics of electrons in counter-propagating, circularly polarized laser beams are shown to exhibit attractors whose ability to trap particles depends on the ratio of the beam intensities and a single parameter describing radiation reaction. Analytical expressions are found for the underlying limit cycles and the parameter range in which they are stable. In high-intensity optical pulses, where radiation reaction strongly modifies the trajectories, the production of collimated gamma-rays and the initiation of non-linear cascades of electron–positron pairs can be optimized by a suitable choice of the intensity ratio.

  17. Wound healing in porcine skin following low-output carbon dioxide laser irradiation of the incision

    SciTech Connect

    Robinson, J.K.; Garden, J.M.; Taute, P.M.; Leibovich, S.J.; Lautenschlager, E.P.; Hartz, R.S.

    1987-06-01

    Wound healing of scalpel incisions to the depth of adipose tissue closed with conventional methods was compared with closure by low-output carbon dioxide laser irradiation. In 3 Pitman-Moore minipigs wound healing was evaluated at intervals from 1 to 90 days by the following methods: clinical variables of wound healing; formation of the basement membrane components bullous pemphigoid antigen, laminin, and fibronectin; and histological evaluation of the regeneration of the epidermis, neovascularization, and elastin and collagen formation. There was no significant difference in healing between wounds closed by the various conventional methods and by the low-output carbon dioxide laser.

  18. Optimal two-mirror system for laser radiation focusing

    SciTech Connect

    Gitin, Andrey V

    2009-10-31

    An optical system for laser radiation focusing, which consists of parabolic and elliptic mirrors, is considered. It is shown by the method of elementary reflections that the maximum concentration of laser radiation on the target can be achieved at a certain position of these mirrors. (laser applications and other topics in quantum electronics)

  19. Comparison of pulsed and continuous-wave carbon dioxide laser interactions with cutaneous tissue

    NASA Astrophysics Data System (ADS)

    Reinisch, Lou; Rivas, Mike; Ossoff, Jacob; Deriso, Walter; Sternemann, Jeff; Ossoff, Robert H.

    1997-05-01

    We measured the acute tissue shrinkage using a continuous wave and a pulsed carbon dioxide laser for skin resurfacing. The tissue shrinkage was measured on in vitro, non-facial human skin samples. We also examined the amount of thermal damage in the skin acutely and three days after laser resurfacing using a piglet model. The pulsed laser used a 100 microsecond pulse and delivered 500 mJ in a 3 by 3 mm square spot. The continuous wave laser was delivered with a hand piece that moved the beam in a 3.4 mm spiral during the 0.2 s irradiation. The continuous wave laser was set to 8 W. As expected, the pulsed laser showed less thermal damage acutely and after three days when compared to the continuous wave laser. However, the pulsed laser also showed more tissue shrinkage than was observed with the continuous wave laser. These results imply that the tissue shrinkage from carbon dioxide laser resurfacing may be related to the tissue removal more than collagen denaturation.

  20. Cascaded frequency doublers for broadband laser radiation

    SciTech Connect

    Andreev, N F; Vlasova, K V; Davydov, V S; Kulikov, S M; Makarov, A I; Sukharev, Stanislav A; Freidman, Gennadii I; Shubin, S V

    2012-10-31

    A new scheme of a cascaded converter of the first harmonic of broadband cw laser radiation into the second harmonic (SH) with compensation for the group walk-off in cascades is proposed and investigated. The conditions under which high conversion coefficients of broadband ({approx}33 cm{sup -1}) single-mode fibre laser radiation with low peak power ({approx}300 W) into the SH are determined for frequency doublers based on the most promising LBO crystal. Conversion of cw radiation with an average power of 300 W and efficiency {eta} = 4.5 % into the SH is obtained in a single LBO crystal. Effect of coherent addition of SH radiation excited in different cascades is demonstrated for two- and three-stage schemes. The expected conversion efficiencies, calculated disregarding loss but taking into account real aberrations of elements, are 18 % and 38 %, respectively. The effect of pumping depletion begins to manifest itself in the third cascade of a three-stage converter; it may reduce the latter value to {approx}30 %. (nonlinear optical phenomena)

  1. Argon laser treatment of radiation proctitis

    SciTech Connect

    O'Connor, J.J.

    1989-06-01

    Radiation therapy for malignant gynecologic disease and prostatic cancer has resulted in increased survival and cure rates. This modality has unfortunately produced debilitating radiation proctitis. Recently, five patients were seen with continuous rectal bleeding secondary to radiation disease of the rectum. Four of these patients were women who were being treated for cervical carcinoma and one was a man with prostatic cancer. These patients were refractory to steroid retention enemas, iron therapy, and benproperine enema therapy. Treatment was accomplished using the argon laser with a 300-micron fiber passed via flexible fiberoptic sigmoidoscope. The most proximal areas were treated first. One and a half watts at 0.5 pulses was used. Up to 50 pulses were delivered per therapy session. The fiber was placed in contact with the lesion and circumferentially for 0.5 cm surrounding each suspected area. Bleeding stopped in the four women after two sessions and in the man after four sessions.

  2. Electromagnetic system for the management of the output power of the carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Martsinukov, S. A.; Kostrin, D. K.; Chernigovskiy, V. V.; Lisenkov, A. A.

    2016-07-01

    The methods to control the output power of the gas-discharge lasers are shown. An electromagnetic system for the management of the output power of the carbon dioxide laser is described. The results of calculation and modeling of the magnetic field in the working gap of the electromagnetic system are presented. Experimental studies on the distribution of magnetic induction in the electromagnetic system are carried out.

  3. Coherent microwave radiation from a laser induced plasma

    SciTech Connect

    Shneider, M. N.; Miles, R. B.

    2012-12-24

    We propose a method for generation of coherent monochromatic microwave/terahertz radiation from a laser-induced plasma. It is shown that small-scale plasma, located in the interaction region of two co-propagating plane-polarized laser beams, can be a source of the dipole radiation at a frequency equal to the difference between the frequencies of the lasers. This radiation is coherent and appears as a result of the so-called optical mixing in plasma.

  4. Evaporated Hafnia/Silicon Dioxide Optical Coatings and Modifications for High-Power Laser Applications

    NASA Astrophysics Data System (ADS)

    Oliver, James B.

    Evaporated optical coatings fabricated from hafnium dioxide and silicon dioxide are the standard approach for high-peak-power laser components due to the high laser damage resistance of such coatings and the ability to deposit on large-aperture substrates. The tensile film stresses of such coatings may lead to failure, however, particularly in low-relative-humidity purged or vacuum use environments. Careful control of thin-film stresses is essential to maintain high-quality surface flatness of the coated components and preserve the optical performance of the laser system. This work explores changes in the deposition process for hafnia/silica multilayer coatings in order to preserve or ideally improve the laser damage thresholds while limiting the mechanical stress in the film. Changes in the evaporation process, including deposition rate, chamber pressure, temperature, and optical coating design, were studied to evaluate their influence on the performance of the coating. Process changes were expanded to include the use of energetic plasma-assisted deposition as well as the incorporation of aluminum oxide to further alter the thin-film stress. The state of the thin-film stress, laser damage thresholds, and photometric performance of the optical coating were evaluated throughout this effort. Modifications to the evaporated electron-beam deposition process parameters of hafnium dioxide and silicon dioxide were insufficient to provide a near-neutral film stress. However, the use of plasma-assisted deposition and the inclusion of aluminum oxide layers both provided the means to deposit optical coatings with near-neutral or slightly-compressive film stresses and high-laser-damage thresholds. Plasma-assisted coatings were demonstrated with laser damage thresholds of greater than 20 J/cm2 at 1053 nm, using a 1 ns pulse, while maintaining compressive film stresses of 10-50 MPa. Coatings incorporating alumina layers altered the film stress by limiting the diffusion of water

  5. Fast microstructuring of silica glasses surface by NIR laser radiation

    NASA Astrophysics Data System (ADS)

    Kostyuk, G. K.; Sergeev, M. M.; Zakoldaev, R. A.; Yakovlev, E. B.

    2015-05-01

    The glass surface microstructuring technology using laser radiation with NIR wavelength (λ=1.064 μm) was revealed in this work. Glass plates were placed on the cellular graphite surface. Focused laser radiation passed through the glass plate and interacted with cellular graphite. The radiation heated the graphite surface and thus the high temperature influenced the back side of the glass plate. After consecutive laser scans, having certain periods and interruptions of laser radiation, the microstructures with depth ~0.5 μm were formed. Besides, in this work we suggested the method to calculate optical characteristics of formed elements. It was experimentally shown that these microstructures could be used to form phase diffraction gratings (PDGs) and random phase plates (RPPs). We experimentally demonstrated the possibility of these elements being used as RPPs which are suitable for multimode laser radiation homogenization and as PDGs which are suitable for laser simultaneous processing of metal films.

  6. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spatial distribution of laser radiation scattered in a plasma formed by optical breakdown of a gas

    NASA Astrophysics Data System (ADS)

    Bufetov, Igor'A.; Bufetova, G. A.; Fyodorov, V. B.

    1994-12-01

    Spatial distributions of laser radiation scattered by a laser spark were determined at different laser radiation wavelengths (λ = 1060, 530, 353, and 265 nm) and gas pressures (air at 10-760 Torr). An interference structure of the cone of the scattered radiation behind the spark was detected for the first time. The structure was attributed to interference of the radiation scattered in two or more self-focusing centres in the laser-spark plasma in air. The dependences of the maximum scattering angle on the gas pressure and on the laser radiation wavelength were determined experimentally.

  7. Laser plasma influence on the space-time structure of powerful laser radiation

    NASA Astrophysics Data System (ADS)

    Ananyin, O. B.; Bogdanov, G. S.; Vovchenko, E. D.; Gerasimov, I. A.; Kuznetsov, A. P.; Melekhov, A. P.

    2016-01-01

    This paper deals with the influence of laser plasma on the structure of the radiation field of a powerful Nd-glass laser with pulse energy up to 30 J and with the diameter of the output beam 45 mm. Laser plasma is generated by focusing the laser radiation on a low-density target such as nylon mesh and teflon or mylar films. Temporal profile of the laser pulse with a total duration of 25 ns consists of a several short pulse train. Duration of each pulse is about 2 ns. Notable smoothing of spatially non-uniform radiation structure was observed in the middle of the laser pulse.

  8. Effect of a new carbon dioxide laser treatment on dissolution profiles of dental enamel

    NASA Astrophysics Data System (ADS)

    Featherstone, John D. B.; Le, Charles Q.; Fried, Daniel

    2003-06-01

    Previous studies have shown that pretreatment of dental enamel by specific carbon dioxide laser conditions inhibited subsequent acid dissolution of the enamel surface. The aim of the present study was to examine the dissolution profiles following irradiation by a new short pulse carbon dioxide laser treatment. Bovine enamel blocks were irradiated at 9.6 μm with a 5-8 μs or a 20-30 μs pulse duration laser using overlapping spots, and a range of fluences. Dissolution profiles were measured in an acetate buffer. Higher fluences produced rapid initial dissolution followed by a plateau with a low dissolution rate. For caries inhibition purposes the high solubility decomposition phases need to be avoided or removed.

  9. Phase-selective vanadium dioxide (VO{sub 2}) nanostructured thin films by pulsed laser deposition

    SciTech Connect

    Masina, B. N. E-mail: slafane@cdta.dz; Lafane, S. E-mail: slafane@cdta.dz; Abdelli-Messaci, S.; Kerdja, T.; Wu, L.; Akande, A. A.; Mwakikunga, B.

    2015-10-28

    Thin films of monoclinic nanostructured vanadium dioxide are notoriously difficult to produce in a selective manner. To date, post-annealing, after pulsed laser deposition (PLD), has been used to revert the crystal phase or to remove impurities, and non-glass substrates have been employed, thus reducing the efficacy of the transparency switching. Here, we overcome these limitations in PLD by optimizing a laser-ablation and deposition process through optical imaging of the laser-induced plasma. We report high quality monoclinic rutile-type vanadium dioxide (VO{sub 2}) (M1) nanoparticles without post-annealing, and on a glass substrate. Our samples demonstrate a reversible metal-to-insulator transition at ∼43 °C, without any doping, paving the way to switchable transparency in optical materials at room temperature.

  10. Surgical Coagulator With Carbon Dioxide Laser For Gynecology

    NASA Astrophysics Data System (ADS)

    Wolinski, Wieslaw; Kazmirowski, Antoni; Korobowicz, Witold; Olborski, Zbigniew

    1987-10-01

    The technical data and parameters of the CO2 surgical laser for gynecology are given. Coagulator was designed and constructed in Institute of Microelectronics and Optoelectronics Warsaw Technical University.

  11. Carbon dioxide lasers. Citations from the NTIS data base

    NASA Astrophysics Data System (ADS)

    Cavagnaro, D. M.

    1980-10-01

    Citations on theory, design, operation, output and diagnostics of CO2 lasers are presented. Studies relating to excitation, frequency conversion, modulation, laser pumping, reaction kinetics, gas dynamics, and plasmas are included. The development and efficiency of optical components such as mirrors, resonators, tuning devices, infrared optical materials, amplifiers, and gratings are also discussed. This updated bibliography contains 214 citations, 70 of which are new entries to the previous edition.

  12. Thermal radiative near field transport between vanadium dioxide and silicon oxide across the metal insulator transition

    NASA Astrophysics Data System (ADS)

    Menges, F.; Dittberner, M.; Novotny, L.; Passarello, D.; Parkin, S. S. P.; Spieser, M.; Riel, H.; Gotsmann, B.

    2016-04-01

    The thermal radiative near field transport between vanadium dioxide and silicon oxide at submicron distances is expected to exhibit a strong dependence on the state of vanadium dioxide which undergoes a metal-insulator transition near room temperature. We report the measurement of near field thermal transport between a heated silicon oxide micro-sphere and a vanadium dioxide thin film on a titanium oxide (rutile) substrate. The temperatures of the 15 nm vanadium dioxide thin film varied to be below and above the metal-insulator-transition, and the sphere temperatures were varied in a range between 100 and 200 °C. The measurements were performed using a vacuum-based scanning thermal microscope with a cantilevered resistive thermal sensor. We observe a thermal conductivity per unit area between the sphere and the film with a distance dependence following a power law trend and a conductance contrast larger than 2 for the two different phase states of the film.

  13. Thermal Conductivity Measurement of Xe-Implanted Uranium Dioxide Thick Films using Multilayer Laser Flash Analysis

    SciTech Connect

    Nelson, Andrew T.

    2012-08-30

    The Fuel Cycle Research and Development program's Advanced Fuels campaign is currently pursuing use of ion beam assisted deposition to produce uranium dioxide thick films containing xenon in various morphologies. To date, this technique has provided materials of interest for validation of predictive fuel performance codes and to provide insight into the behavior of xenon and other fission gasses under extreme conditions. In addition to the structural data provided by such thick films, it may be possible to couple these materials with multilayer laser flash analysis in order to measure the impact of xenon on thermal transport in uranium dioxide. A number of substrate materials (single crystal silicon carbide, molybdenum, and quartz) containing uranium dioxide films ranging from one to eight microns in thickness were evaluated using multilayer laser flash analysis in order to provide recommendations on the most promising substrates and geometries for further investigation. In general, the uranium dioxide films grown to date using ion beam assisted deposition were all found too thin for accurate measurement. Of the substrates tested, molybdenum performed the best and looks to be the best candidate for further development. Results obtained within this study suggest that the technique does possess the necessary resolution for measurement of uranium dioxide thick films, provided the films are grown in excess of fifty microns. This requirement is congruent with the material needs when viewed from a fundamental standpoint, as this length scale of material is required to adequately sample grain boundaries and possible second phases present in ceramic nuclear fuel.

  14. Radiating electron source generation in ultraintense laser-foil interactions

    NASA Astrophysics Data System (ADS)

    Capdessus, R.; King, M.; McKenna, P.

    2016-08-01

    A radiating electron source is shown to be created by a laser pulse (with intensity of 1023 W/cm2 and duration equal to 30 fs) interacting with a near-critical density plasma. It is shown that the back radiation reaction resulting from high energy synchrotron radiation tends to counteract the action of the ponderomotive force. This enhances the collective dynamics of the radiating electrons in the highest field areas, resulting in the production of a compact radiation source (containing 80% of the synchrotron radiation emission), with an energy on the order of tens of MeV over the laser pulse duration. These phenomena are investigated using a QED-particle-in-cell code, and compared with a kinetic model accounting for the radiation reaction force in the electron distribution function. The results shed new light on electron-photon sources at ultra-high laser intensities and could be tested on future laser facilities.

  15. Endotracheal tube fires during carbon dioxide laser surgery on the larynx--a case report.

    PubMed

    Kuo, C H; Tan, P H; Chen, J J; Peng, C H; Lee, C C; Chung, H C; Tseng, C K

    2001-03-01

    Endotracheal tube (ETT) fire is a catastrophic disaster that may occur during laser surgery of the upper airway. Several means are available for protection of polyvinyl chloride (PVC) tube from fire, but they are not perfect in prevention of fires caused by laser beam. The PVC tube is hazardous for carbon dioxide (CO2) laser surgery if it is not well wrapped with metallized foil tape. We report a case that a PVC ETT wrapped with aluminum foil ignited during CO2 laser surgery of the larynx. In this report, we emphasize the shaft of the PVC tube must be completely wrapped with aluminum foil to prevent exposure of any surface if it is used in CO2 laser surgery of the upper aero digestive tract. PMID:11407297

  16. Photocatalytic ROS production and phototoxicity of titanium dioxide nanoparticles is dependent on solar UV radiation spectrum

    EPA Science Inventory

    Generation of reactive oxygen species (ROS) by titanium dioxide nanoparticles (nano-TiO2) and its consequent phototoxicity to Daphnia magna were measured under different solar UV radiation spectrum by applying a series of optical filters in a solar simulator. Removing UVB (280-32...

  17. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spectral and temporal characteristics of a laser plasma

    NASA Astrophysics Data System (ADS)

    Lipchak, A. I.; Solomonov, V. I.; Tel'nov, V. A.; Osipov, V. V.

    1995-04-01

    An experimental investigation was made of the spectral and temporal characteristics of a laser plasma formed by the interaction of a CO2 laser pulse with a target in atmospheric air. The results obtained indicate that the main role in the process of filling the excited states in a laser plasma is played by a recombination cascade and that both atoms and molecules of the atmospheric gases are excited. The result also show that a laser plasma can be used in spectroscopic analysis of multicomponent samples. The solution of the thermophysical problem of heating of a target by laser radiation supports the existing ideas on the process of formation of a plasma near the target surface in air.

  18. Selective removal of dental composite using a rapidly scanned carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Chan, Kenneth H.; Fried, Daniel

    2011-03-01

    Dental restorative materials are color matched to the tooth and are difficult to remove by mechanical means without excessive removal or damage to peripheral enamel and dentin. Lasers are ideally suited for selective ablation to minimize healthy tissue loss when replacing existing restorations, sealants or removing composite adhesives such as residual composite left after debonding orthodontic brackets. In this study a carbon dioxide laser operating at high laser pulse repetition rates integrated with a galvanometer based scanner was used to selectively remove composite from tooth surfaces. A diode array spectrometer was used to measure the plume emission after each laser pulse and determine if the ablated material was tooth mineral or composite. The composite was placed on tooth buccal and occlusal surfaces and the carbon dioxide laser was scanned across the surface to selectively remove the composite without excessive damage to the underlying sound enamel. The residual composite and the damage to the underlying enamel was evaluated using optical microscopy. The laser was able to rapidly remove the composites rapidly from both surfaces with minimal damage to the underlying sound enamel.

  19. Selective Removal of Dental Composite using a Rapidly Scanned Carbon Dioxide Laser.

    PubMed

    Chan, Kenneth H; Fried, Daniel

    2011-01-01

    Dental restorative materials are color matched to the tooth and are difficult to remove by mechanical means without excessive removal or damage to peripheral enamel and dentin. Lasers are ideally suited for selective ablation to minimize healthy tissue loss when replacing existing restorations, sealants or removing composite adhesives such as residual composite left after debonding orthodontic brackets. In this study a carbon dioxide laser operating at high laser pulse repetition rates integrated with a galvanometer based scanner was used to selectively remove composite from tooth surfaces. A diode array spectrometer was used to measure the plume emission after each laser pulse and determine if the ablated material was tooth mineral or composite. The composite was placed on tooth buccal and occlusal surfaces and the carbon dioxide laser was scanned across the surface to selectively remove the composite without excessive damage to the underlying sound enamel. The residual composite and the damage to the underlying enamel was evaluated using optical microscopy. The laser was able to rapidly remove the composites rapidly from both surfaces with minimal damage to the underlying sound enamel. PMID:21927546

  20. Selective Removal of Dental Composite using a Rapidly Scanned Carbon Dioxide Laser.

    PubMed

    Chan, Kenneth H; Fried, Daniel

    2011-01-01

    Dental restorative materials are color matched to the tooth and are difficult to remove by mechanical means without excessive removal or damage to peripheral enamel and dentin. Lasers are ideally suited for selective ablation to minimize healthy tissue loss when replacing existing restorations, sealants or removing composite adhesives such as residual composite left after debonding orthodontic brackets. In this study a carbon dioxide laser operating at high laser pulse repetition rates integrated with a galvanometer based scanner was used to selectively remove composite from tooth surfaces. A diode array spectrometer was used to measure the plume emission after each laser pulse and determine if the ablated material was tooth mineral or composite. The composite was placed on tooth buccal and occlusal surfaces and the carbon dioxide laser was scanned across the surface to selectively remove the composite without excessive damage to the underlying sound enamel. The residual composite and the damage to the underlying enamel was evaluated using optical microscopy. The laser was able to rapidly remove the composites rapidly from both surfaces with minimal damage to the underlying sound enamel.

  1. Laser therapy for the treatment of Hailey-Hailey disease: a systematic review with focus on carbon dioxide laser resurfacing.

    PubMed

    Falto-Aizpurua, L A; Griffith, R D; Yazdani Abyaneh, M A; Nouri, K

    2015-06-01

    Benign familial chronic pemphigus, or Hailey-Hailey disease (HHD), is a recurrent bullous dermatitis that tends to have a chronic course with frequent relapses. Long-term treatment options include surgery with skin grafting or dermabrasion. Both are highly invasive and carry significant risks and complications. More recently, 'laser-abrasion' has been described as a less invasive option with a better side-effect profile. In this article, we systematically review the safety and efficacy of carbon dioxide laser therapy as a long-term treatment option for HHD, as well as provide a review of other lasers that have been reported with this goal. A total of 23 patients who had been treated with a carbon dioxide laser were identified. After treatment, 10 patients (43%) had had no recurrence, 10 (43%) had greater than 50% improvement, 2 (8%) had less than 50% improvement and 1 (4%) patient had no improvement at all (follow-up period ranged from 4 to 144 months). Laser parameter variability was wide and adverse effects were minimal, including dyspigmentation and scarring. Reviewed evidence indicates this therapy offers a safe, effective treatment alternative for HHD with minimal risk of side-effects. Larger, well-designed studies are necessary to determine the optimal treatment parameters.

  2. Measurement of divergence of co/sub 2/-laser radiation

    SciTech Connect

    Shepelenko, A.A.; Shulyat'ev, V.B.

    1986-04-01

    This paper presents a modification of the Foucault method for measuring the radiation divergence of high-power CW lasers in which the limiting diaphram is produced by an aperture burned through by the laser radiation itself. The method is suitable for beams with any cross-sectional intensitiy distribution. Results of divergence measurements of a CO/sub 2/ production laser with power to 2 kW are presented.

  3. Laser radiation attenuation by sparks of optical breakdown

    NASA Astrophysics Data System (ADS)

    Budnik, A. P.; Semenov, L. P.; Skripkin, A. M.; Volkovitskii, O. A.

    1989-06-01

    A breakdown generated by laser radiation in a gas contaminated by aerosol particles is known to occur at much lower radiation intensities than in case of pure gases. Laser radiation is heavily attenuated by sparks of plasma formed at breakdowns. Energy loss estimation is important at radiation propagation in the atmosphere and in laser resonators. The breakdown phenomenon may be used in diagnostics of the atmospheric aerosol contamination events. The report presents experimental data on the influence of aerosol size distribution and concentration on optical breakdown generation and other results.

  4. Laser Radiation Attenuation By Sparks Of Optical Breakdown

    NASA Astrophysics Data System (ADS)

    Budnik, A. P.; Semenov, L. P.; Skripkin, A. M.; Volkovitsky, O. A.

    1990-01-01

    A breakdown generated by laser radiation in a gas contaminated by aerosol particles is known to occur at much lower radiation intensities than in case of pure gases, Laser radiation is heavily attenuated by sparks of plasma formed at breakdowns. Energy loss estimation is important at radiation propagation in the atmosphere and in laser resonators. The breakdown phenomenon may be used in diagnostics of the atmospheric aerosol contamination events. The report presents experimental data on the influence of aerosol size distribution and concentration on optical breakdown generation and other results.

  5. Selective removal of demineralization using near infrared cross polarization reflectance and a carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Chan, Kenneth H.; Fried, Daniel

    2012-01-01

    Lasers can ablate/remove tissue in a non-contact mode of operation and a pulsed laser beam does not interfere with the ability to image the tooth surface, therefore lasers are ideally suited for integration with imaging devices for image-guided ablation. Laser energy can be rapidly and efficiently delivered to tooth surfaces using a digitally controlled laser beam scanning system for precise and selective laser ablation with minimal loss of healthy tissues. Under the appropriate irradiation conditions such laser energy can induce beneficial chemical and morphological changes in the walls of the drilled cavity that can increase resistance to further dental decay and produce surfaces with enhanced adhesive properties to restorative materials. Previous studies have shown that images acquired using near-IR transillumination, optical coherence tomography and fluorescence can be used to guide the laser for selective removal of demineralized enamel. Recent studies have shown that NIR reflectance measurements at 1470-nm can be used to obtain images of enamel demineralization with very high contrast. The purpose of this study was to demonstrate that image guided ablation of occlusal lesions can be successfully carried out using a NIR reflectance imaging system coupled with a carbon dioxide laser operating at 9.3-μm with high pulse repetition rates.

  6. Measurement of formaldehyde, nitrogen dioxide, and sulfur dioxide at Whiteface Mountain using a dual tunable diode laser system

    NASA Astrophysics Data System (ADS)

    Li, Y. Q.; Demerjian, K. L.; Zahniser, M. S.; Nelson, D. D.; McManus, J. B.; Herndon, S. C.

    2004-08-01

    An application of a dual tunable diode laser absorption spectrometer (TDLAS) to ambient measurements of formaldehyde (HCHO), nitrogen dioxide (NO2) and sulfur dioxide (SO2) is described. During the PM2.5 Technology Assessment and Characterization Study-New York (PMTACS-NY) 2002 intensive field campaign at Whiteface Mountain, New York, a dual TDLAS was deployed during a field instrument comparison study along with five other state-of-the-art trace gas measurement techniques. Prior to the field study, a thorough laboratory characterization of the instrument was undertaken to establish the optimum operational conditions including the selection of absorption features and the implementation of continuous laser frequency locking and rapid background subtraction. The Allan variance method was used to determine the optimal background subtraction cycle and to evaluate instrument performance. During the field campaign, measurements of HCHO, NO2 and SO2 were made by the TDLAS with the measurement precisions (1-min time interval, 1σ) of 80 ppt, 30 ppt and 40 ppt, respectively. The HCHO time series indicated a high variability of HCHO concentrations ranging from below the detection limit to 5 ppbv. The diurnal cycle of HCHO measurements showed higher concentrations during the late afternoon and early morning hours. The measured NO2 concentrations varied from less than the detection limit to the maximum of 25 ppbv. Broad NO2 plumes from long-distance transport of air masses and as well as high spikes from local pollution sources were observed during the campaign. The measured SO2 results also show high variability with the average concentration of 0.75 ± 0.95 ppbv (1σ).

  7. Coloured marking inside glass by laser radiation

    NASA Astrophysics Data System (ADS)

    Ligbado, Grace; Horn, Alexander; Kreutz, Ernst W.; Krauss, Manfred M.; Siedow, Norbert; Hensel, Hartmut

    2005-11-01

    Laser labelling inside glass induces micro-cracks by high energy densities in the focus. The micro-cracks reduce the mechanical stability of glass. Light scattering allows the observer to perceive the cracks as white pixels. Coloured marking of glass in this manner is not possible. Coloured marking inside glass by changing the oxidation state of the metal ions locally in the focus does not weaken the mechanical properties of the glass. Two kind of glass systems, lime-natron-silicate and borosilicate with 0.5 % mass-content of doping are investigated. The simultaneous presence of donators and acceptors allows a transition of electrons between polyvalent ions, and can lead to permanent colour-centres inside the glass, due to the fact that the absorption of the polyvalent ions is changed by the laser-induced conversion process. For this purpose a 3 ω Nd:YAG (wavelength λL = 355 nm, pulse duration t = 10 to 80 ns) and a Ti:Sapphire solid-state laser (wavelength λL = 810 nm, pulse duration t = 200 fs) are used. The radiation parameters and the chemical composition of the glass (mainly doping) are the dominant factors to generate coloured marking. The transmittance as a function of the fluence and the change of the absorption coefficient is measured and gives a statement of the colourshade. Further the difference between lime-natron-silicate and borosilicate glass (same doping variety) is examined. Actually mauve, yellow, red-brown an grey colouring can be produced. Cracks in the microstructure of glass can also be the cause for brown colour-centres generating.

  8. Effects of femtosecond laser radiation on the skin

    NASA Astrophysics Data System (ADS)

    Rogov, P. Yu; Bespalov, V. G.

    2016-08-01

    A mathematical model of linear and nonlinear processes is presented occurring under the influence of femtosecond laser radiation on the skin. There was held an analysis and the numerical solution of an equation system describing the dynamics of the electron and phonon subsystems were received. The results can be used to determine the maximum permissible levels of energy generated by femtosecond laser systems and the establishment of Russian laser safety standards for femtosecond laser systems.

  9. Direct determination of carbon dioxide in aqueous solution using mid-infrared quantum cascade lasers.

    PubMed

    Schaden, S; Haberkorn, M; Frank, J; Baena, J R; Lendl, B

    2004-06-01

    A method for the direct determination of carbon dioxide in aqueous solutions using a room-temperature mid-infrared (MIR) quantum cascade laser at 2330 cm(-1) is reported. The absorption values of different carbon dioxide concentrations were measured in a 119 microm CaF2 flow-through cell. An optical system made of parabolic mirrors was used to probe the flow cell and to focus the laser beam on the mercury cadmium telluride (MCT) detector. Aqueous carbon dioxide standards were prepared by feeding different mixtures of gaseous N2 and CO2 through wash bottles at controlled temperature. The concentration of the dissolved CO2 was calculated according to Henry's law, taking into account the temperature and the partial pressure of CO2. The carbon dioxide standards were connected via a selection valve to a peristaltic pump for subsequent, automated measurement in the flow-through cell. A calibration curve was obtained in the range of 0.338 to 1.350 g/L CO2 with a standard deviation of the method sxo equal to 19.4 mg/L CO2. The limit of detection was calculated as three times the baseline noise over time and was determined to be 39 mg/L.

  10. Dissociation phenomena in electron-beam sustained carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Harris, Michael R.; Willetts, David V.

    1990-01-01

    A number of applications are emerging requiring efficient, long pulse, long-life sealed CO2 lasers. Examples include the proposed NASA and ESA wind lidars. Electron-beam sustained discharge devices are strong contenders. Unlike self-sustained discharges, e-beam sustenance readily provides efficient performance from large volume discharges and offers pulse lengths well in excess of the microsecond or so generally associated with self-sustained devices. In the case of the e-beam sustained laser, since the plasma is externally maintained and operated at electric field strengths less than that associated with the glow to arc transition, the discharges can be run even in the presence of strongly attacking species such as O2. Build up of large levels of attacking contaminants is nevertheless undesirable as their presence reduces the current drawn by the plasma and thus the pumping rate to the upper laser level. The impedance rise leads to a mismatch of the pulse forming network with a consequent loss of control over energy deposition, operating E/N, and gain. Clearly CO2 dissociation rates, the influence of dissociation products on the discharge and gain, and tolerance of the discharge to these products need to be determined. This information can then be used to assess co-oxidation catalyst requirements for sealed operation.

  11. Carbon dioxide (CO2) laser treatment of bovine penile persistent frenulum and fibropapillomas

    NASA Astrophysics Data System (ADS)

    Tate, Lloyd P.

    1995-05-01

    Persistent Frenulum and Fibropapillomas are commonly encountered diseases of young bulls. Both are amenable to simple resection with ligation of bleeders followed by mucosa suturing. Sexual rest for several weeks is generally required. Carbon dioxide laser was applied in resection of both these two maladies in six bulls (2 Persistent Frenulum, 4 with fibropapillomas) without the need for ligation of bleeders or mucosal suturing. No immediate postsurgery complications occurred related to the laser being used and potential recurrence of fibropapilloma neoplasia did not occur. The CO2 laser, compared to the steel scalpel, provided better visibility and improved hemostatic capabilities for performing the resection. The CO2 laser incisions healed completely by two weeks postirradiation, and the bulls required only one week sexual rest to allow healing to progress prior to entering an active breeding program.

  12. Carbon Dioxide Laser Microsurgical Median Glossotomy for Resection of Lingual Dermoid Cysts

    PubMed Central

    Corvers, Kristien; Hens, Greet; Meulemans, Jeroen; Delaere, Pierre; Hermans, Robert; Vander Poorten, Vincent

    2016-01-01

    Dermoid cysts are epithelial-lined cavities with skin adnexae in the capsule. Only 7% is present in the head and neck. Between 2004 and 2013, four patients with a lingual dermoid cyst underwent a microsurgical carbon dioxide laser resection via a median sagittal glossotomy approach. This approach is an elegant technique combining superior visualization, hemostasis, and little postoperative edema with good wound healing, allowing for perfect function preservation of the tongue. PMID:27504448

  13. JPL Carbon Dioxide Laser Absorption Spectrometer Data Processing Results for the 2010 Flight Campaign

    NASA Technical Reports Server (NTRS)

    Jacob, Joseph C.; Spiers, Gary D.; Menzie, Robert T.; Christensen, Lance E.

    2011-01-01

    As a precursor to and validation of the core technology necessary for NASA's Active Sensing of CO2 Emissions over Nights, Days,and Seasons (ASCENDS) mission, we flew JPL's Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) in a campaign of five flights onboard NASA's DC-8 Airborne Laboratory in July 2010. This is the latest in a series of annual flight campaigns that began in 2006, and our first on the DC-8 aircraft.

  14. Design of catalytic monoliths for closed-cycle carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Herz, Richard K.

    1988-01-01

    A computer program was written that allows the design of catalytic monoliths for closed-cycle carbon dioxide lasers. Using design parameters obtained from workers at NASA Langley Research Center and from the literature, several specific monoliths were designed and the results were communicated to the research group working on this project at Langley. Two oral presentations were made at NASA-sponsored workshops - at Langley in January 1988 and in Gainesville, Florida in May 1988.

  15. Simultaneously Photoacoustic Measurement of Carbon Dioxide and Nitrous Oxide Using a Quantum Cascade Laser

    NASA Astrophysics Data System (ADS)

    Liu, Q.; Cao, Zh.; Shao, Sh.; Zhu, W.; Huang, H.; Gao, X.; Li, X.

    2016-09-01

    In this paper a photoacoustic senor for carbon dioxide and nitrous oxide detection is described which uses a quantum cascade laser. The sensor relies on a 4.43 μm continuous-wave room temperature quantum-cascade laser source and a homemade photoacoustic cell based on a cylindrical acoustic resonator. Primary laboratory tests have been performed for estimation of the achievable detection limits and possible applications for in situ and real time atmosphere measurements. It is demonstrated that the minimum detectable concentration of 13CO2 and N2O under laboratory conditions is 8 ppbv and 0.45 ppbv, respectively.

  16. Carbon dioxide laser-induced combustion of extravasated intraocular silicone oil in the eyelid mimicking xanthelasma.

    PubMed

    Santaella, Ricardo M; Ng, John D; Wilson, David J

    2011-01-01

    A 48-year-old woman with a history of retinal detachment repair with vitrectomy, scleral buckling, and silicone oil with subsequent oil removal was referred for unilateral upper eyelid ptosis with edema and overlying skin changes simulating xanthelasma. During surgical excision, a white flare-like plume was noted when the carbon dioxide (CO2) laser was used to make the incisions. The pathology report confirmed silicone oil intrusion in the conjunctiva and upper eyelid. A postoperative in vitro experiment showed that silicone oil was readily ignited by the CO2 laser.

  17. Monolith catalysts for closed-cycle carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Herz, Richard K.

    1994-01-01

    The general subject area of the project involved the development of solid catalysts that have high activity at low temperature for the oxidation of gases such as CO. The original application considered was CO oxidation in closed-cycle CO2 lasers. The scope of the project was subsequently extended to include oxidation of gases in addition to CO and applications such as air purification and exhaust gas emission control. The primary objective of the final phase grant was to develop design criteria for the formulation of new low-temperature oxidation catalysts utilizing Monte Carlo simulations of reaction over NASA-developed catalysts.

  18. Immunomodulation action of ultraviolet N2-laser radiation

    NASA Astrophysics Data System (ADS)

    Pukhova, Yana; Provorov, Alexander S.; Salmin, Vladimir V.

    1995-01-01

    The report deals with the investigation of the influence of N2-laser radiation on the kinetics of the initial specimens of the respiratory chain -- reactive oxygen forms (ROFs) -- depending on its parameters. It was shown, that the energy of N2-laser radiation promotes to the correction of the ROF generation and leads to an immunomodulation effect. We suppose that the immunomodulation effect is connected with a key molecule of the respiratory chain -NADP(H) and with the regulation role of ROF. We emphasize the necessity of correction of the pathological processes with hypo- and hyperfunction of granulocyte- macrophage cells by N2-laser radiation under the ROF generation kinetics control.

  19. Terahertz plasmonic laser radiating in an ultra-narrow beam

    DOE PAGES

    Wu, Chongzhao; Khanal, Sudeep; Reno, John L.; Kumar, Sushil

    2016-07-07

    Plasmonic lasers (spasers) generate coherent surface plasmon polaritons (SPPs) and could be realized at subwavelength dimensions in metallic cavities for applications in nanoscale optics. Plasmonic cavities are also utilized for terahertz quantum-cascade lasers (QCLs), which are the brightest available solid-state sources of terahertz radiation. A long standing challenge for spasers that are utilized as nanoscale sources of radiation, is their poor coupling to the far-field radiation. Unlike conventional lasers that could produce directional beams, spasers have highly divergent radiation patterns due to their subwavelength apertures. Here, we theoretically and experimentally demonstrate a new technique for implementing distributed feedback (DFB) thatmore » is distinct from any other previously utilized DFB schemes for semiconductor lasers. The so-termed antenna-feedback scheme leads to single-mode operation in plasmonic lasers, couples the resonant SPP mode to a highly directional far-field radiation pattern, and integrates hybrid SPPs in surrounding medium into the operation of the DFB lasers. Experimentally, the antenna-feedback method, which does not require the phase matching to a well-defined effective index, is implemented for terahertz QCLs, and single-mode terahertz QCLs with a beam divergence as small as 4°×4° are demonstrated, which is the narrowest beam reported for any terahertz QCL to date. Moreover, in contrast to a negligible radiative field in conventional photonic band-edge lasers, in which the periodicity follows the integer multiple of half-wavelengths inside the active medium, antenna-feedback breaks this integer limit for the first time and enhances the radiative field of the lasing mode. Terahertz lasers with narrow-beam emission will find applications for integrated as well as standoff terahertz spectroscopy and sensing. Furthermore, the antenna-feedback scheme is generally applicable to any plasmonic laser with a Fabry–Perot cavity

  20. 20 mA bidirectional laser triggering in planar devices based on vanadium dioxide thin films using CO(2) laser.

    PubMed

    Kim, Jihoon; Jo, Songhyun; Park, Kyongsoo; Song, Ha-Joo; Kim, Hyun-Tak; Kim, Bong-Jun; Lee, Yong Wook

    2015-06-01

    By utilizing a CO2 laser centered at ~10.6 μm as an optical stimulus, we demonstrated bidirectional laser triggering in a two-terminal planar device based on a highly resistive vanadium dioxide (VO2) thin film. The break-over voltage of the VO2-based device was measured as large as ~294.8 V, which resulted from the high resistivity of insulating VO2 grains comprising the thin film and the large electrode separation of the device. The bidirectional current switching of up to 20 mA was achieved by harnessing the dramatic resistance variation of the device photo-thermally induced by the laser illumination. The transient responses of laser-triggered currents were also analyzed when laser pulses excited the device at a variety of pulse widths and repetition rates. In the transient responses, a maximum switching contrast between off- and on-state currents was measured as ~7067 with an off-state current of ~2.83 μA, and rising and falling times were measured as ~30 and ~16 ms, respectively, for 100 ms laser pulses.

  1. Design of catalytic monoliths for closed-cycle carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Herz, R. K.; Guinn, K.; Goldblum, S.; Noskowski, E.

    1989-01-01

    Pulsed carbon dioxide (CO2) lasers have many applications in aeronautics, space research, weather monitoring and other areas. Full exploitation of the potential of these lasers in hampered by the dissociation of CO2 that occurs during laser operation. The development of closed-cycle CO2 lasers requires active CO-O2 recombination (CO oxidation) catalyst and design methods for implementation of catalysts in CO2 laser systems. A monolith catalyst section model and associated design computer program, LASCAT, are presented to assist in the design of a monolith catalyst section of a closed cycle CO2 laser system. Using LASCAT,the designer is able to specify a number of system parameters and determine the monolith section performance. Trade-offs between the catalyst activity, catalyst dimensions, monolith dimensions, pressure drop, O2 conversion, and other variables can be explored and adjusted to meet system design specifications. An introduction describes a typical closed-cycle CO2 system, and indicates some advantages of a closed cycle laser system over an open cycle system and some advantages of monolith support over other types of supports. The development and use of a monolith catalyst model is presented. The results of a design study and a discussion of general design rules are given.

  2. Interaction of CO 2 laser radiation with glasses

    NASA Astrophysics Data System (ADS)

    Kozhukharov, V.; Dimitrov, D.; Tonchev, D.

    1989-05-01

    An illustration of an interaction of pulsed multimode TEA CO 2 laser radiation, through or without a mask, as well as of a laser scanning process of a frequency Q-modulated cw CO 2 laser beam on glass surfaces has been shown. As an object of investigation glass articles with composition as a standard industrial potassium-boron silicate glass, we have used. A complex of investigations shows that the laser treatment leads to qualitative constant changes (well defined peeling structure) depending on the time surface treatment, defocusing and the pulse length of the laser output.

  3. Er:YAG laser radiation etching of enamel

    NASA Astrophysics Data System (ADS)

    Dostalova, Tatjana; Jelinkova, Helena; Krejsa, Otakar; Hamal, Karel; Kubelka, Jiri; Prochazka, Stanislav

    1996-12-01

    This study compares the effects of acid treatment and Er:YAG laser radiation on the enamel. The permanent human molars were used. Oval cavities in the buccal surface were prepared and the edges of cavities were irradiated by Er:YAG radiation. The energy of laser was 105 mJ and repetition rate 1 Hz. The radiation was focused by CaF2 lens and the sample was placed in the focus. Ten samples were etched by 35 percent phosphoric acid during 60 s. Than cavities were filled with composite resin following manufacturers directions. By laser etching the structure enamel in section was rougher. The optimal connection between the enamel and composite resin was achieved in 75 percent by acid etching and in 79.2 percent by Er:YAG laser etching. Er:YAG laser etching could be alternative method for etching of enamel.

  4. Radiation Damage on Multiple Length Scales in Uranium Dioxide

    NASA Astrophysics Data System (ADS)

    Gupta, Mahima

    Radiation damage in UO2 has been well studied but there exists little correlation between point defect accumulation, lattice structure changes and microstructure. This is partly because irradiated nuclear fuel is highly radioactive and its defect chemistry is extremely complicated resulting from fission of the material and consequent fission products being embedded in the fuel matrix [Olander1976]. To adequately study the evolution of defects from point defects through to microstructure features, the resulting defects have to be intentionally simplified for characterization. Ion accelerators have the unique capability of creating simple microstructure features using specific ions, without the added complication of fission and neutron activation from nuclear reactors. As an example, H+ ions have been used to create (only) a distribution of dislocations that were studied using various techniques. The ability to tune the energy or type of the ion to achieve desirable implantation depth and ideally simple microstructure renders it a lucrative instrument for this type of analysis. X-ray diffraction (XRD) studies and transmission electron microscopy (TEM) have been utilized to study extended structure changes and microstructure evolution. Ion beam irradiations create displacements and displacement networks, voids, surface fracturing, gas bubbles and several other microstructure changes to model nuclear reactor damage [Noris1972]. Using an ion accelerator, it has been possible to isolate these radiation induced defects and study their subsequent evolution with increasing dose. Insofar, since all of the phenomena caused by radiation damage originate from point defects, the elucidation of radiation effects on the atomic scale is crucial. This is rendered complicated due to aperiodic irradiation defects. This lack of periodicity renders standard approaches, such as TEM and XRD ineffective, as these methods probe average structure over tens of Angstroms. Therefore, techniques

  5. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Feasibility of investigation of optical breakdown statistics using multifrequency lasers

    NASA Astrophysics Data System (ADS)

    Ulanov, S. F.

    1990-06-01

    A method proposed for investigating the statistics of bulk optical breakdown relies on multifrequency lasers, which eliminates the influence of the laser radiation intensity statistics. The method is based on preliminary recording of the peak intensity statistics of multifrequency laser radiation pulses at the caustic using the optical breakdown threshold of K8 glass. The probability density distribution function was obtained at the focus for the peak intensities of the radiation pulses of a multifrequency laser. This method may be used to study the self-interaction under conditions of bulk optical breakdown of transparent dielectrics.

  6. Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) Aircraft Measurements of CO2

    NASA Technical Reports Server (NTRS)

    Christensen, Lance E.; Spiers, Gary D.; Menzies, Robert T.; Jacob, Joseph C.; Hyon, Jason

    2011-01-01

    The Jet Propulsion Laboratory Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) utilizes Integrated Path Differential Absorption (IPDA) at 2.05 microns to obtain CO2 column mixing ratios weighted heavily in the boundary layer. CO2LAS employs a coherent detection receiver and continuous-wave Th:Ho:YLF laser transmitters with output powers around 100 milliwatts. An offset frequency-locking scheme coupled to an absolute frequency reference enables the frequencies of the online and offline lasers to be held to within 200 kHz of desired values. We describe results from 2009 field campaigns when CO2LAS flew on the Twin Otter. We also describe spectroscopic studies aimed at uncovering potential biases in lidar CO2 retrievals at 2.05 microns.

  7. Study on ceramic coating on the enamel surface using a carbon dioxide laser.

    PubMed

    Nihei, Tomotaro; Kurata, Shigeaki; Ohashi, Katsura; Umemoto, Kozo; Teranaka, Toshio

    2011-01-01

    The aims of this study were to evaluate a new restorative method using a carbon dioxide laser (CO(2)-laser) and to evaluate the acid resistance of teeth. Experimental calcium phosphate glass (CPG) powder and two low melting point ceramics (Finesse and zirconium silicate) were fused to enamel surfaces using a CO(2)-laser at an irradiation intensity of 1.0 watt for 30 seconds with a beam size of 0.49 mm at the focal point. The treated teeth were observed with a scanning electron microscope, and the acid resistance of the treated enamel surfaces was evaluated. The CPG fused successfully to the enamel surface, and the treated enamel surface showed high acid resistance compared with the low melting point ceramics and the non-irradiated surfaces. This system may lead to the development of new restorative methods that do not require the use of bonding agents. PMID:21422667

  8. 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.

  9. The 2014 ASCENDS Field Campaign - a Carbon Dioxide Laser Absorption Spectrometer Perspective

    NASA Astrophysics Data System (ADS)

    Spiers, G. D.; Menzies, R. T.; Jacob, J. C.; Geier, S.; Fregoso, S. F.

    2014-12-01

    NASA's ASCENDS mission has been flying several candidate lidar instruments on board the NASA DC-8 aircraft to obtain column integrated measurements of Carbon Dioxide. Each instrument uses a different approach to making the measurement and combined they have allowed for the informed development of the ASCENDS mission measurement requirements(1). The JPL developed Carbon Dioxide Laser Absorption Spectrometer, CO2LAS is one of these instruments. The CO2LAS measures the weighted, column averaged carbon dioxide between the aircraft and the ground using a continuous-wave heterodyne technique. The instrument operates at a 2.05 micron wavelength optimized for enhancing sensitivity to boundary layer carbon dioxide. Since the 2013 field campaign the instrument has undergone significant upgrades that improve the data collection efficiency and instrument stability and has recently been re-integrated onto the NASA DC-8 for the August 2014 ASCENDS field campaign. This presentation will summarize the instrument and algorithm improvements and review the 2014 field campaign flights and preliminary results. (1) Abshire, J.B. et al., "An overview of NASA's ASCENDS Mission lidar measurement requirements", submitted to 2014 Fall AGU Conference.

  10. Multilevel radiative thermal memory realized by the hysteretic metal-insulator transition of vanadium dioxide

    NASA Astrophysics Data System (ADS)

    Ito, Kota; Nishikawa, Kazutaka; Iizuka, Hideo

    2016-02-01

    Thermal information processing is attracting much interest as an analog of electronic computing. We experimentally demonstrated a radiative thermal memory utilizing a phase change material. The hysteretic metal-insulator transition of vanadium dioxide (VO2) allows us to obtain a multilevel memory. We developed a Preisach model to explain the hysteretic radiative heat transfer between a VO2 film and a fused quartz substrate. The transient response of our memory predicted by the Preisach model agrees well with the measured response. Our multilevel thermal memory paves the way for thermal information processing as well as contactless thermal management.

  11. Studies of new media radiation induced laser

    NASA Technical Reports Server (NTRS)

    Han, K. S.; Shiu, Y. J.; Raju, S. R.; Hwang, I. H.; Tabibi, B.

    1984-01-01

    Various lasants were investigated especially, 2-iodohepafluoropropane (i-C3F7I) for the direct solar pumped lasers. Optical pumping of iodine laser was achieved using a small flashlamp. Using i-C3F7I as a laser gain medium, threshold inversion density, small signal gain, and laser performance at the elevated temperature were measured. The experimental results and analysis are presented. The iodine laser kinetics of the C3F7I and IBr system were numerically simulated. The concept of a direct solar-pumped laser amplifier using (i-C3F7I) as the laser material was evaluated and several kinetic coefficients for i-C3F7I laser system were reexamined. The results are discussed.

  12. Laser radiation and motility patterns of human sperm

    SciTech Connect

    Lenzi, A.; Claroni, F.; Gandini, L.; Lombardo, F.; Barbieri, C.; Lino, A.; Dondero, F. )

    1989-01-01

    Human sperm were exposed in vitro to laser radiation. An increase in progressive sperm motility was associated with a faster rate of sperm ATP consumption. Computer-assisted analysis of sperm motility confirmed the positive effect of laser irradiation on velocity and linearity of sperm.

  13. A blackbody radiation-pumped CO2 laser experiment

    NASA Astrophysics Data System (ADS)

    Christiansen, W. H.; Insuik, R. J.; Deyoung, R. J.

    1982-09-01

    Thermal radiation from a high temperature oven was used as an optical pump to achieve lasing from CO2 mixtures. Laser output as a function of blackbody temperature and gas conditions is described. This achievement represents the first blackbody cavity pumped laser and has potential for solar pumping.

  14. Novel radiator for carbon dioxide absorbents in low-flow anesthesia.

    PubMed

    Hirabayashi, Go; Mitsui, Takanori; Kakinuma, Takayasu; Ogihara, Yukihiko; Matsumoto, Shohei; Isshiki, Atsushi; Yasuo, Watanabe

    2003-01-01

    During long-term low-flow sevoflurane anesthesia, dew formation and the generation of compound A are increased in the anesthesia circuit because of elevated soda lime temperature. The object of this study was to develop a novel radiator for carbon dioxide absorbents used for long durations of low-flow sevoflurane anesthesia. Eleven female swine were divided into two groups comprising a "radiator" group (n = 5) that used a novel radiator for carbon dioxide absorbents and a "control" group (n = 6) that used a conventional canister. Anesthesia was maintained with N2O, O2, and sevoflurane, and low-flow anesthesia was performed with fresh gas flow at 0.6 L/min for 12 hr. In the "control" group, the soda lime temperature reached more than 40 degrees C and soda lime dried up with severe dew formation in the inspiratory valve. In the "radiator" group, the temperature of soda lime stayed at 30 degrees C, and the water content of soda lime was retained with no dew formation in the inspiratory valve. In addition, compound A concentration was reduced. In conclusion, radiation of soda lime reduced the amounts of condensation formed and the concentration of compound A in the anesthetic circuit, and allowed long term low-flow anesthesia without equipment malfunction.

  15. Monolith catalysts for closed-cycle carbon dioxide lasers

    NASA Technical Reports Server (NTRS)

    Herz, Richard K.; Badlani, Ajay

    1991-01-01

    The objective was to explore ways of making a monolithic form of catalyst for CO2 lasers. The approach chosen was to pelletize the catalyst material, Au/MnO2 powder, and epoxy the pellets to stainless steel sheets as structural supports. The CO oxidation reaction over Au/MnO2 powder was found to be first overall, and the reaction rate constant at room temperature was 4.4 +/- 0.3 cc/(g x sec). The activation energy was 5.7 kcal/mol. The BET surface area of the pellets was found to vary from 125 to 140 sq m/g between different batches of catalyst. Pellets epoxied to stainless steel strips showed no sign of fracture or dusting when subjected to thermal tests. Pellets can be dropped onto hard surfaces with chipping of edges but no breakage of the pellets. Mechanical strength tests performed on the pellets showed that the crush strength is roughly one-fourth of the pelletizing force. The apparent activity and activation energy over the pellets were found to be less than over the powdered form of the catalyst. The lower apparent activity and activation energy of the pellets are due to the fact that the internal surface area of a pellet is not exposed to the reactant concentration present in the flowing gas as a result of intrapellet diffusion resistance. Effectiveness factors varied from 0.44, for pellets having thickness of 2 mm and attached with epoxy to a stainless steel strip. The epoxy and the stainless steel strip were found to simply block off one of the circular faces of the pellets. The epoxy did not penetrate the pellets and block the active sites. The values of the effective diffusivities were estimated to be between 2.3 x 10(exp -3) and 4.9 x 10(exp -3) sq cm/s. With measurements performed on one powder sample and one pellet configuration, reasonable accurate predictions can be made of conversions that would be obtained with other pellet thickness and configurations.

  16. Electrical and optical properties of vanadium dioxide containing gold nanoparticles deposited by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Orlianges, J.-C.; Leroy, J.; Crunteanu, A.; Mayet, R.; Carles, P.; Champeaux, C.

    2012-09-01

    Nanostructured vanadium dioxide is one of the most interesting and studied member of the vanadates family performing a reversible transition from an insulating state to a metallic state associated with a structural transition when heated above a temperature of 68 °C. On the other hand, noble metal nanoparticles (NPs) support localized surface plasmon resonance which causes selective absorption bands in the visible and near-IR regions. The purpose of this letter is to study structural, optical, and electrical properties of vanadium dioxide thin films containing gold nanoparticles synthetized using pulsed laser deposition process. Thus, we have performed x-ray diffraction, optical transmission, and four point probe electrical measurements to investigate the nanocomposite properties versus its temperature. Interestingly, we have observed switching behavior for VO2 film containing gold NPs with a resistivity contrast of four orders of magnitude and a decrease of its transition temperature.

  17. Observation of laser driven supercritical radiative shock precursors.

    PubMed

    Bouquet, S; Stéhlé, C; Koenig, M; Chièze, J-P; Benuzzi-Mounaix, A; Batani, D; Leygnac, S; Fleury, X; Merdji, H; Michaut, C; Thais, F; Grandjouan, N; Hall, T; Henry, E; Malka, V; Lafon, J-P J

    2004-06-01

    We present a supercritical radiative shock experiment performed with the LULI nanosecond laser facility. Using targets filled with xenon gas at low pressure, the propagation of a strong shock with a radiative precursor is evidenced. The main measured shock quantities (electronic density and propagation velocity) are shown to be in good agreement with theory and numerical simulations. PMID:15245230

  18. Biological Studies On The Effect of Laser Radiation on Khapra Beetle Trogoderma granarium (Coleoptera : Dermestidae)

    NASA Astrophysics Data System (ADS)

    El-Nozahy, Adel M.; Ahmed, Salwa M. M. S.; Abdel-Kader, Mahomoud H.; Khalifa, Ibtesam A.

    2007-02-01

    The aim of the present work was to study the effect of Argon-ion laser and carbon dioxide laser radiation on Khapra beetle Trogoderma granarium and induced sterility. Radiobiological effects of irradiation were determined on adult stage of resulted 2-3 days-old pupae at LD30. The radiobiological studies induced determination of mortality, of, LD30, LD50 emergence, preovipositio period, fecundity, sterility, incubation period, larval duration, pupal duration and emergence of 1st generation. Experiments were carried out to determine the latent effect of irradiation on the wheat grains germination as well as the effects on the chemical constituents. In this respect irradiation of grains had no effect on the above ntioned parameters.

  19. Radiative shocks on large scale lasers. Preliminary results

    NASA Astrophysics Data System (ADS)

    Leygnac, S.; Bouquet, S.; Stehle, C.; Barroso, P.; Batani, D.; Benuzzi, A.; Cathala, B.; Chièze, J.-P.; Fleury, X.; Grandjouan, N.; Grenier, J.; Hall, T.; Henry, E.; Koenig, M.; Lafon, J. P. J.; Malka, V.; Marchet, B.; Merdji, H.; Michaut, C.; Poles, L.; Thais, F.

    2001-05-01

    Radiative shocks, those structure is strongly influenced by the radiation field, are present in various astrophysical objects (circumstellar envelopes of variable stars, supernovae ...). Their modeling is very difficult and thus will take benefit from experimental informations. This approach is now possible using large scale lasers. Preliminary experiments have been performed with the nanosecond LULI laser at Ecole Polytechnique (France) in 2000. A radiative shock has been obtained in a low pressure xenon cell. The preparation of such experiments and their interpretation is performed using analytical calculations and numerical simulations.

  20. Testing Unruh Radiation with Ultra-Intense Lasers

    NASA Astrophysics Data System (ADS)

    Chen, Pisin; Tajima, Toshiki

    1997-04-01

    We point of that using the state-of-the-art (or soon to be) intense ultrafast laser technology, violent acceleration of electrons that may be suitable for testing general relativistic effects can be realized in the laboratory settings. In particular we demonstrate that the Unruh radiation is detectable, in principle, beyond the conventional radiation (most notably the Larmor radiation) background noise, by taking the advantages of their specific dependences on the laser power, their different characters in spectral-angular distributions, and the time structure of the signals.

  1. Photodynamic Therapy with Ablative Carbon Dioxide Fractional Laser in Treatment of Actinic Keratosis

    PubMed Central

    Jang, Yong Hyun; Lee, Dong Jun; Shin, Jaeyoung; Kang, Hee Young; Lee, Eun-So

    2013-01-01

    Background Recently, photodynamic therapy (PDT) has been shown to be an effective first-line treatment for actinic keratosis (AK). However, a major limitation of PDT is the long incubation time required to allow penetration of the photosensitizer. Objective The aim of this study was to assess if pretreatment with an ablative carbon dioxide (CO2) fractional laser can reduce the incubation time of the photosensitizer. Methods Initially, 29 patients with a total of 34 AK lesions were treated with an ablative CO2 fractional laser at Ajou University Hospital between January and December 2010. Immediately after the laser treatment, topical 20% 5-aminolevulinic acid or methyl-aminolevulinate was applied to the AK lesions and incubated for 70 to 90 minutes. Then, the treated areas were illuminated with a red light source. Improvement was clinically or histologically assessed eight weeks after the treatment. Results In spite of the short incubation time, 24 lesions (70.6%) showed a complete response (CR) within three sessions of PDT (10 lesions a clinical CR and 14 lesions a clinical/histological CR). There were no significant side effects associated with the combination of ablative CO2 fractional laser and PDT. Conclusion Ablative CO2 fractional laser may be considered an additional treatment option for reducing the incubation time of the photosensitizer in PDT. PMID:24371387

  2. Visual sensing and range measurement by scanning of carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Kawata, Koichi; Takahashi, Hidemi; Yamada, Osamu; Kimura, Minoru; Naito, Hiroshi

    1992-11-01

    A laser vision sensor has been developed to enable range measurement and identification of targets through flames, smoke, and fog which are invisible to the human eye. This vision sensor employs a 10.6 micrometers -wavelength carbon dioxide laser for its long wavelength. The target is scanned two-dimensionally by the laser beam, directed by a pair of galvanometer mirrors, to produce the target image and measure the range of the target. The laser beam, amplitude-modulated to 5 MHz with an electro-optic modulator, is projected onto a target, and the reflected beam is detected by a cadmium mercury telluride detector. The phase difference between the projected and reflected light signals is used to provide range data up to 30 m. The indoor test is carried out with a 1 cubic meter box in which flames, smoke, and fog can be generated. The laser beam is projected through this box, and the targets behind this box are detected. The reproduced image is sufficient for identification through flames, smoke, and fog.

  3. Fractional Carbon Dioxide Laser for Keratosis Pilaris: A Single-Blind, Randomized, Comparative Study

    PubMed Central

    Vachiramon, Vasanop; Anusaksathien, Pattarin; Kanokrungsee, Silada; Chanprapaph, Kumutnart

    2016-01-01

    Objective. Keratosis pilaris (KP) is a common condition which can frequently be cosmetically disturbing. Topical treatments can be used with limited efficacy. The objective of this study is to evaluate the effectiveness and safety of fractional carbon dioxide (CO2) laser for the treatment of KP. Patients and Methods. A prospective, randomized, single-blinded, intraindividual comparative study was conducted on adult patients with KP. A single session of fractional CO2 laser was performed to one side of arm whereas the contralateral side served as control. Patients were scheduled for follow-up at 4 and 12 weeks after treatment. Clinical improvement was graded subjectively by blinded dermatologists. Patients rated treatment satisfaction at the end of the study. Results. Twenty patients completed the study. All patients stated that the laser treatment improved KP lesions. At 12-week follow-up, 30% of lesions on the laser-treated side had moderate to good improvement according to physicians' global assessment (p = 0.02). Keratotic papules and hyperpigmentation appeared to respond better than the erythematous component. Four patients with Fitzpatrick skin type V developed transient pigmentary alteration. Conclusions. Fractional CO2 laser treatment may be offered to patients with KP. Dark-skinned patients should be treated with special caution. PMID:27247936

  4. Proximal gastric vagotomy with carbon dioxide laser: Experimental studies in animals

    SciTech Connect

    Kadota, T.; Mimura, K.; Kanabe, S.; Ohsaki, Y.; Tamakuma, S. )

    1990-06-01

    Proximal gastric vagotomy has been widely used as a surgical treatment for peptic ulcer disease. However, it is technically complex and time-consuming. Moreover, it may cause circulatory problems in the gastric mucosa. We have reported a new method of blood flow-preserving vagotomy with a carbon dioxide laser (CO2 laser vagotomy) developed in our laboratory. To assess its efficacy, we used cysteamine-induced ulcer and measured gastric mucosal blood flow in rats. The incidence of cysteamine-induced ulcer formation was reduced significantly in the group that underwent CO{sub 2} laser vagotomy compared with a group treated with proximal gastric vagotomy. Gastric mucosal blood flow was significantly better in the CO{sub 2} laser vagotomy group. Long-term follow-up of acid reduction was evaluated in dogs by the pentagastrin-stimulation test. Acid reduction in dogs was satisfactory during the 12 months of this study. CO{sub 2} laser vagotomy is a new, easy, time-saving, and circulatory-preserving technique for peptic ulcer disease.

  5. [Influence of microwave and laser radiation on survivability of organisms].

    PubMed

    Ismailov, E Sh; Zakharov, S D; Aminova, E M; Ismailova, G E; Khachirov, D G

    2001-01-01

    Depending on energy, spatial-temporal, modulation and other characteristics of an electromagnetic field, properties of a subject, exposure settings and possible interaction of other attendant factors microwaves may have either stabilizing, wholesome and even therapeutic or negative (damaging) effects on biological and ecological objects and systems. Therefore, there are two interrelated problems to be addressed. One is electromagnetic safety of and health provisions for humans exposed to EMF and EMR and the other, effective utilization of microwave EMF and EMR for biomedical and other purposes associated with enhancement of viability of organisms. The light-oxygen effect of laser radiation is gaining footing in therapy where it is used to activate or destroy biological systems by optical radiation at a specified light dose. Thus, low-intensity laser radiation can be used to improve viability and high-intensity laser radiation, to treat cancers. PMID:11668960

  6. Characteristics of radiation safety for synchrotron radiation and X-ray free electron laser facilities.

    PubMed

    Asano, Yoshihiro

    2011-07-01

    Radiation safety problems are discussed for typical electron accelerators, synchrotron radiation (SR) facilities and X-ray free electron laser (XFEL) facilities. The radiation sources at the beamline of the facilities are SR, including XFEL, gas bremsstrahlung and high-energy gamma ray and photo-neutrons due to electron beam loss. The radiation safety problems for each source are compared by using 8 GeV class SR and XFEL facilities as an example.

  7. Airborne Carbon Dioxide Laser Absorption Spectrometer for IPDA Measurements of Tropospheric CO2: Recent Results

    NASA Technical Reports Server (NTRS)

    Spiers, Gary D.; Menzies, Robert T.

    2008-01-01

    The National Research Council's decadal survey on Earth Science and Applications from Space[1] recommended the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission for launch in 2013-2016 as a logical follow-on to the Orbiting Carbon Observatory (OCO) which is scheduled for launch in late 2008 [2]. The use of a laser absorption measurement technique provides the required ability to make day and night measurements of CO2 over all latitudes and seasons. As a demonstrator for an approach to meeting the instrument needs for the ASCENDS mission we have developed the airborne Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) which uses the Integrated Path Differential Absorption (IPDA) Spectrometer [3] technique operating in the 2 micron wavelength region.. During 2006 a short engineering checkout flight of the CO2LAS was conducted and the results presented previously [4]. Several short flight campaigns were conducted during 2007 and we report results from these campaigns.

  8. Comparison of the erbium-yttrium aluminum garnet and carbon dioxide lasers for in vitro bone and cartilage ablation

    SciTech Connect

    Gonzalez, C.; van de Merwe, W.P.; Smith, M.; Reinisch, L. )

    1990-01-01

    The in vitro bone- and cartilage-ablation characteristics of the solid-state erbium:yttrium aluminum garnet laser were compared to those of the carbon dioxide laser. Ablations of fresh, frozen cadaver septal cartilage and maxillary sinus bone were performed using total energies between 1 and 6 J. Specimens were studied using hematoxylin and eosin stain and digitized, computer-assisted measurements of 35-mm photographs. Erbium-yttrium aluminum garnet-ablated bone averaged 5 microns of adjacent tissue thermal injury, compared with 67 microns with carbon dioxide-ablated bone. Erbium-yttrium aluminum garnet-ablated cartilage averaged 2 microns of adjacent tissue thermal injury, compared with 21 microns with the carbon dioxide-ablated cartilage. The tissue-ablation characteristics of the erbium-yttrium aluminum garnet laser are promising for future otolaryngologic applications.

  9. Use of the carbon dioxide laser in guided tissue regeneration wound healing in the beagle dog

    NASA Astrophysics Data System (ADS)

    Rossmann, Jeffrey A.; Parlar, Ates; Abdel-Ghaffar, Khaled A.; El-Khouli, Amr M.; Israel, Michael

    1996-04-01

    The concept of guided tissue regeneration (GTR) allowing cells from the periodontal ligament and alveolar bone to repopulate the treated root surface has shown the ability to obtain periodontal new attachment. Healing studies have also shown that conventional GTR therapy still does not exclude all the epithelium. This epithelial proliferation apically interferes with the establishment of the new connective tissue attachment to the root surface. The objective of this research study was to examine whether controlled de-epithelialization with the carbon dioxide laser during the healing phase after periodontal surgery, would retard the apical migration of the epithelium and thereby enhance the results obtained through guided tissue regeneration. Eight beagle dogs were used, the experimental side received de-epithelialization with the CO2 laser in conjunction with flap reflection and surgically created buccal osseous defects. Selected defects on each side were treated with ePTFE periodontal membranes. The laser de-epithelialization was repeated every 10 days until removal of the membranes. The control side received the same surgical treatment without laser application. This experimental design allowed histologic study of the new attachment obtained in defects treated with flap debridement with or without laser de-epithelialization and with or without ePTFE membranes. A statistical analysis was performed on the histometric data from 48 teeth in the 8 dogs after 4 months of healing. The results showed significant amounts of new attachment obtained from all four treatment modalities with no statistically significant differences for any one treatment. However, the trend towards enhanced regeneration with the combined treatment of laser and membrane vs. membrane alone or debridement alone was evident. The histologic analysis revealed a significant amount of newly formed `fat cementum' seen only on the laser treated teeth. This feature was the most remarkable finding of the

  10. [Study on Reduction of Radiation Exposure by Using Carbon Dioxide Angiography Catheter in Vascular Access Intervention Therapy(VAIVT)].

    PubMed

    Tsukada, Yasunori; Kakuchi, Yasushi

    2015-09-01

    In vascular access intervention therapy (VAIVT), carbon dioxide is used as negative contrast medium for patients with iodine allergy or for those who have vascular access but not started with dialysis yet and have not endangered their remaining kidney function. To capture the movement of jet-injected carbon dioxide during the carbon dioxide angiography, we performed imaging at a rate of 15 frames per second. This method has a higher level of radiation exposure than angiography using an iodine contrast medium. Therefore we developed a catheter with 20 helical side holes in the tip (carbon dioxide angiography catheter), which allows large numbers of tiny bubbles to be generated simultaneously. In our study, we evaluate whether the use of this catheter can reduce the number of frames taken per second thus reducing the radiation exposure. A comparative experiment with existing angiography catheters with no side holes suggested that the use of this carbon dioxide angiography catheter to be useful for reducing the radiation exposure to patients and operators. Moreover, angiography using this catheter is highly useful from viewpoint of improving the stenotic vesselvisibility and reducing the side effects of using carbon dioxide, and we expect that the carbon dioxide angiography method is effective for patients and operators.

  11. Laser radiography forming bremsstrahlung radiation to image an object

    DOEpatents

    Perry, Michael D.; Sefcik, Joseph A.

    2004-01-13

    A method of imaging an object by generating laser pulses with a short-pulse, high-power laser. When the laser pulse strikes a conductive target, bremsstrahlung radiation is generated such that hard ballistic high-energy electrons are formed to penetrate an object. A detector on the opposite side of the object detects these electrons. Since laser pulses are used to form the hard x-rays, multiple pulses can be used to image an object in motion, such as an exploding or compressing object, by using time gated detectors. Furthermore, the laser pulses can be directed down different tubes using mirrors and filters so that each laser pulse will image a different portion of the object.

  12. Ultraviolet laser beam monitor using radiation responsive crystals

    DOEpatents

    McCann, Michael P.; Chen, Chung H.

    1988-01-01

    An apparatus and method for monitoring an ultraviolet laser beam includes disposing in the path of an ultraviolet laser beam a substantially transparent crystal that will produce a color pattern in response to ultraviolet radiation. The crystal is exposed to the ultraviolet laser beam and a color pattern is produced within the crystal corresponding to the laser beam intensity distribution therein. The crystal is then exposed to visible light, and the color pattern is observed by means of the visible light to determine the characteristics of the laser beam that passed through crystal. In this manner, a perpendicular cross sectional intensity profile and a longitudinal intensity profile of the ultraviolet laser beam may be determined. The observation of the color pattern may be made with forward or back scattered light and may be made with the naked eye or with optical systems such as microscopes and television cameras.

  13. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Conversion of the energy of fast electrons to thermal plasma radiation

    NASA Astrophysics Data System (ADS)

    Vergunova, G. A.; Rozanov, Vladislav B.

    1992-01-01

    An analysis is made of the conversion of the energy of highly energetic fast electrons, generated by the action of CO2 laser radiation on a target, into characteristic radiation emitted by a plasma formed from shell targets which, for instance, may be present inside targets irradiated by the CO2 laser. Analytical formulas are obtained for the temperature of the converted radiation. The results show that it is possible to control this radiation by choosing the parameters of the target and of the fast electron flux. The efficiency of conversion into characteristic thermal radiation is found numerically to be 95%. This method of conversion is more favorable than direct interaction of CO2 laser radiation with a target since the emitting region is localized in the target mass. When a laser interacts with a target the mass of this region increases with time and so the temperature of the emitted radiation is lower than in the case when fast electrons act on the target.

  14. Preparation of platinum modified titanium dioxide nanoparticles with the use of laser ablation in water.

    PubMed

    Siuzdak, K; Sawczak, M; Klein, M; Nowaczyk, G; Jurga, S; Cenian, A

    2014-08-01

    We report on the preparation method of nanocrystalline titanium dioxide modified with platinum by using nanosecond laser ablation in liquid (LAL). Titania in the form of anatase crystals has been prepared in a two-stage process. Initially, irradiation by laser beam of a titanium metal plate fixed in a glass container filled with deionized water was conducted. After that, the ablation process was continued, with the use of a platinum target placed in a freshly obtained titania colloid. In this work, characterization of the obtained nanoparticles, based on spectroscopic techniques--Raman, X-ray photoelectron and UV-vis reflectance spectroscopy--is given. High resolution transmission electron microscopy was used to describe particle morphology. On the basis of photocatalytic studies we observed the rate of degradation process of methylene blue (MB) (a model organic pollution) in the presence of Pt modified titania in comparison to pure TiO2--as a reference case. Physical and chemical mechanisms of the formation of platinum modified titania are also discussed here. Stable colloidal suspensions containing Pt modified titanium dioxide crystalline anatase particles show an almost perfect spherical shape with diameters ranging from 5 to 30 nm. The TiO2 nanoparticles decorated with platinum exhibit much higher (up to 30%) photocatalytic activity towards the degradation of MB under UV illumination than pure titania.

  15. Excimer laser with highly coherent radiation

    SciTech Connect

    Atezhev, Vladimir V; Vartapetov, Sergei K; Zhukov, A N; Kurzanov, M A; Obidin, Aleksei Z

    2003-08-31

    Experimental studies aimed at the optimisation of an unstable resonator of an ArF electric-discharge laser are performed. Several optical schemes of an unstable resonator of a single-module laser are proposed and investigated. It is shown that the laser developed on the basis of these schemes is characterised by a high coherence (the spatial coherence length is 1 - 10 mm and the temporal coherence length is 0.5 - 30 mm at a pulse energy of 40 - 290 mJ). (special issue devoted to the memory of academician a m prokhorov)

  16. LASERS IN MEDICINE: Structure of matrices for the transformation of laser radiation by biofractals

    NASA Astrophysics Data System (ADS)

    Angel'skii, O. V.; Ushenko, A. G.; Arkhelyuk, A. D.; Ermolenko, S. B.; Burkovets, D. N.

    1999-12-01

    The changes in the state of polarisation of laser radiation transformed by biofractal objects are examined. The orientational angular structure of the matrix elements of the operator representing the optical properties of biofractals with different morphological structures (mineralised collagen fibres and myosin bundles) is investigated. An optical model for the description of fractal laser fields under the conditions of single light scattering is proposed.

  17. Effect of carbon dioxide laser treatment on lesion progression in an intraoral model

    NASA Astrophysics Data System (ADS)

    Featherstone, John D. B.; Fried, Daniel; Gansky, Stuart A.; Stookey, George K.; Dunipace, Ann J.

    2001-04-01

    Previous studies have shown that pretreatment of dental enamel by specific carbon dioxide laser conditions inhibited subsequent progression of caries-like lesions in vitro. The aim of the present study was to use an intra-oral model to determine whether similar inhibition is observed in the human mouth. A cross over study with 23 subjects and three regimens was used. Pre-formed varies-like lesions were made in extracted human enamel and exposed intra-orally in partial dentures in each subject to A) placebo dentifrice and no laser treatment, B) placebo dentifrice following laser pretreatment, or C) sodium fluoride dentifrice and no laser treatment during each of three study periods. Samples were assessed by micro radiography to compare the mineral loss before and after each treatment and drive a net change in mineral value. Overall P was not significantly different form L but both P and L were different from F. For those subjects who demineralized in P, L and F were significantly better than P, with L showing an 84 percent inhibition of further demineralization, but no enhancement of demineralization.

  18. Effect of a new carbon dioxide laser and fluoride on sound and demineralized enamel

    NASA Astrophysics Data System (ADS)

    dos Santos, Marines N.; Featherstone, John D. B.; Fried, Daniel

    2001-04-01

    The present study aimed to test the hypothesis that irradiation of dental enamel by a TEA carbon dioxide laser together with fluoride, can effectively inhibit caries-like progression in sound and demineralized enamel. Blocks of human sound and demineralized dental enamel were divided into 11 treatment groups. Eighty enamel blocks were partially demineralized in a 50 percent HAP/0.1 M lactic acid/carbopol solution. Samples were treated with/without laser and/or F according to the above groups. The blocks were then submitted to 5 days of pH cycling. Microradiography was performed on 100 micrometers thin sections to determine the relative mineral loss as (Delta) Z and the percentage of caries inhibition for the laser and F treated groups. Mean (Delta) Z values for groups I-X were, respectively: 1043; 683; 614; 2294; 1803; 1708; 1547; 1791; 1656;; and 1385. The percent caries inhibition for groups II, III, V-X was respectively: 35, 41; 49; 62; 42; 53 and 76 percent. The combination of this new TEA CO2 laser and F treatment produced a significant protective effect against lesion progression.

  19. Effect of a new carbon dioxide laser and fluoride on occlusal caries progression in dental enamel

    NASA Astrophysics Data System (ADS)

    Nobre dos Santos, Marines; Fried, Daniel; Rapozo-Hilo, Marcia L.; Featherstone, John D. B.

    2002-06-01

    The purpose of this study was to investigate the effect of a new TEA carbon dioxide (CO2) laser (.9.6 micrometers , 5-8 microsecond(s) pulse duration) combined with fluoride (F), on the inhibition of caries-like progression in occlusal surfaces in sound and demineralized enamel. Of 120 occlusal tooth surfaces (10 per group), 90 were partially demineralized in a 50% HAP/0.1 M Lactic acid/carbopol solution (pH 5.0). Samples were treated with/without the laser (2.0 j/cm2 or 3.0 J/cm2) and/or F (as APF). Caries-like progression was tested by 5 days of pH cycling. Results were assessed by cross-sectional quantitative microradiography. The percent inhibition of caries progression with laser and/or F ranged from 87-170%. This new TEA CO2 laser produced significant protective effect against lesion progression, and in combination with fluoride treatment lesion reversal occurred.

  20. Warming early Mars with carbon dioxide clouds that scatter infrared radiation.

    PubMed

    Forget, F; Pierrehumbert, R T

    1997-11-14

    Geomorphic evidence that Mars was warm enough to support flowing water about 3.8 billion years ago presents a continuing enigma that cannot be explained by conventional greenhouse warming mechanisms. Model calculations show that the surface of early Mars could have been warmed through a scattering variant of the greenhouse effect, resulting from the ability of the carbon dioxide ice clouds to reflect the outgoing thermal radiation back to the surface. This process could also explain how Earth avoided an early irreversible glaciation and could extend the size of the habitable zone on extrasolar planets around stars.

  1. Optical properties and radiation stability of submicro- and nanopowders titanium dioxide measured in situ

    NASA Astrophysics Data System (ADS)

    Mikhailov, M. M.; Neshchimenko, V. V.; Yuryev, S. A.

    2016-04-01

    This study carried out an in situ and external investigation on the reflective spectra of micro- and nanopowders titanium dioxide before and after irradiation by 30 keV electrons. The particle sizes range from 60-240 nm. It was established that the decrease in the particle size leads to an increase in intrinsic defects. The particles with intrinsic defects are then transformed into absorption centers during irradiation as a result of optical degradation of TiO2 powders. High radiation stability has particle sizes range from 80-160 nm.

  2. Warming early Mars with carbon dioxide clouds that scatter infrared radiation.

    PubMed

    Forget, F; Pierrehumbert, R T

    1997-11-14

    Geomorphic evidence that Mars was warm enough to support flowing water about 3.8 billion years ago presents a continuing enigma that cannot be explained by conventional greenhouse warming mechanisms. Model calculations show that the surface of early Mars could have been warmed through a scattering variant of the greenhouse effect, resulting from the ability of the carbon dioxide ice clouds to reflect the outgoing thermal radiation back to the surface. This process could also explain how Earth avoided an early irreversible glaciation and could extend the size of the habitable zone on extrasolar planets around stars. PMID:9360920

  3. Femtosecond laser induced periodic nanostructures on titanium dioxide film for improving biocompatibility

    NASA Astrophysics Data System (ADS)

    Shinonaga, T.; Horiguchi, N.; Tsukamoto, M.; Nagai, A.; Yamashita, K.; Hanawa, T.; Matsushita, N.; Guoqiang, X.; Abe, N.

    2013-03-01

    Periodic nanostructures formation on Titanium dioxide (TiO2) film by scanning of femtosecond laser beam spot at fundamental and second harmonic wave is reported. Titanium (Ti) is one of the most widely used for biomaterials, because of its excellent anti-corrosion and high mechanical properties. However, Ti implant is typically artificial materials and has no biofunction. Hence, it is necessary for improving the bioactivity of Ti. Recently, coating of TiO2 film on Ti plate surface is useful methods to improve biocompatibility of Ti plate. Then, if periodic nanostructures were formed on the film surface, cell spreading might be controlled at one direction. We propose periodic nanostructures formation on TiO2 film by femtosecond laser irradiation. Cell spread could be controlled along the grooves of periodic nanostructures. In the experiments, the film was formed on Ti plate with an aerosol beam. A commercial femtosecond Ti : sapphire laser system was employed in our experiments. Periodic nanostructures, lying perpendicular to the laser electric field polarization vector, were formed on the film at fundamental and second harmonic wave. Periodic nanostructures were also produced on Ti plate with femtosecond laser. The period of periodic nanostructures on the film was much shorter than that on Ti plate. By cell test, there was a region of cell spreading along the grooves of periodic nanostructures on the film formed with femtosecond laser at fundamental wave. On bare film surface, cell spreading was observed at all direction. These results suggest that direction of cell spread could be controlled by periodic nanostructures formation on the film.

  4. Impact of Laser Radiation on Microhardness of a Semiconductor

    SciTech Connect

    Medvid', A.; Onufrijevs, P.; Chiradze, G.; Muktupavela, F.

    2011-12-23

    It was found that strongly absorbed Nd:YAG laser radiation leads to a non-monotonous dependence of microhardness of p- and n-type Si crystals on laser radiation. This dependence is characterized by two maxima for p-Si and one maximum for n-Si crystals. In both cases the increase of microhardness at higher laser intensity is explained by formation of mechanically compressed layer at the irradiated surface due to concentration of the interstitial atoms of Si at the surface in temperature gradient field. The decrease of the microhardness is explained by formation of nano-cones as a result of plastic deformation of the mechanically stressed layer. The additional maximum at lower laser intensity for p-Si crystal is explained by p-n type inversion of Si conductivity.

  5. Simulation of free-electron lasers seeded with broadband radiation

    SciTech Connect

    Bajlekov, Svetoslav; Fawley, William; Schroeder, Carl; Bartolini, Riccardo; Hooker, Simon

    2011-03-10

    The longitudinal coherence of free-electron laser (FEL) radiation can be enhanced by seeding the FEL with high harmonics of an optical laser pulse. The radiation produced by high-harmonic generation (HHG), however, has a fast-varying temporal profile that can violate the slowly varying envelope approximation and limited frequency window that is employed in conventional free-electron laser simulation codes. Here we investigate the implications of violating this approximation on the accuracy of simulations. On the basis of both analytical considerations and 1D numerical studies, it is concluded that, for most realistic scenarios, conventional FEL codes are capable of accurately simulating the FEL process even when the seed radiation violates the slowly varying envelope approximation. We additionally discuss the significance of filtering the harmonic content of broadband HHG seeds.

  6. ARTICLES: High-power laser radiation damage to transparent insulators

    NASA Astrophysics Data System (ADS)

    Gavrilov, B. G.; Kulikov, V. I.; Pedanov, V. V.

    1982-11-01

    An experimental investigation was made of the kinetics of the post-breakdown phenomena accompanying the focusing of high-power laser radiation inside transparent insulators (using the example of single-crystal potassium alum). Measurements were made of the rate of growth of the damage region and of the propagation velocity of the elastic wave, its amplitude and wavelength. The dimensions of the breakdown region were compared with those of the damage zone in the insulator. An analysis was made of the laser radiation energy distribution in the observed phenomenon.

  7. Effects of radiation on direct-drive laser target interaction

    NASA Astrophysics Data System (ADS)

    Colombant, D. G.

    1999-11-01

    Radiation may be useful for reducing laser imprint and Rayleigh-Taylor (RT) growth in direct-drive target pellets. We will discuss the important role of radiation in a proposed direct-drive X-ray preheated target concept(S.Bodner et al., Phys. Plasmas 5,1901(1998)). In this design, a high-Z coating surrounds a thin plastic coat, over a DT-wicked foam and on top of the DT fuel. Radiation effects will be examined and discussed in the context of this design. The soft X-ray radiation emitted during the foot of the laser pulse - at a few 10^12W/cm^2- preheats the foam ablator which contributes to the reduction of the RT instability. The ablator also stops the radiation, allowing the fuel to stay on a low adiabat. Radiation in the blow-off corona of the target establishes a long scalelength plasma. This separates the ablation region from the laser absorption region where the remaining defects in laser uniformity/pellet surface finish constitute the seed for hydrodynamic instabilities. However, when the pulse intensity rises, the pressure generated by the laser in combination with the changing opacity of the plasma causes the plasma to be pushed back toward the ablator. This is called a Radiative Plasma Structure (RPS)(J.Dahlburg et al., J.Q.S.R.T. 54,113(1995)). These RPS's are a potential problem because they may carry with them the imprint which was present in the low-density corona. We will show and discuss these various effects, as well as some of the experimental work(C.Pawley et al., this conference) under way in connection with this program. These experiments are essential in order to validate both the design concepts and the numerical models, which include on-line state-of-the-art atomic physics modeling(M.Klapisch et al.,Phys. Plasmas 5,1919(1998)).

  8. EFFECTS OF LASER RADIATION ON MATTER: Growth of periodic structures on the surface of germanium subjected to pulsed laser radiation

    NASA Astrophysics Data System (ADS)

    Barsukov, D. O.; Gusakov, G. M.; Frolov, A. I.

    1991-12-01

    An experimental investigation was made of the dynamics of growth of periodic surface structures due to the interaction with pulsed laser radiation. Samples of Ge were subjected to laser pulses (λ = 1.06 μm, τ = 70 ns) with energy densities in the range 0.5-5.5 J/cm2. An investigation was made of the dynamics of the first-order diffraction of probe (λ = 0.53 μm) laser pulses with a time resolution 4 ns when p- and s-polarized laser radiation was incident at angles close to normal. A strong nonlinearity of the growth of such periodic surface structures was observed. The energy density from which such growth began depended on the quality of the polished Ge surface. The parameters of the dynamics of the growth of these structures were estimated.

  9. Plasmonic effects on the laser-induced metal-insulator transition of vanadium dioxide

    NASA Astrophysics Data System (ADS)

    Ferrara, Davon W.; MacQuarrie, Evan R.; Nag, Joyeeta; Haglund, Richard F., Jr.

    2010-03-01

    Vanadium dioxide (VO2) is a strongly-correlated electron material with a well-known semiconducting to metallic phase transition that can be induced thermally, optically, or electrically. When switched to the high-temperature (T > 68°C) metallic phase, the greatest contrast in the optical properties occurs at wavelengths in the near-to-mid-infrared and beyond. In the visible to near-infrared, however, upon switching for wavelengths between ~500-1000 nm, VO2 transmits more light in the metallic phase. In this paper, we report studies of the effect of near-IR irradiation (785 nm) on lithographically prepared arrays of gold nanoparticles (NPs) covered with a thin film of VO2 and find that the presence of the NPs substantially lowers the laser threshold for low-power induction of the phase transition. Hybrid Au::VO2 structures were created by coating lithographically prepared arrays of gold nanoparticles (NPs) (diameters 140 and 200 nm, array spacing 450 nm) with 60 nm thick films of VO2 by pulsed laser deposition. Due to resonant absorption of the Au particle-plasmon resonance (PPR) at 785 nm, a temperature-dependent shift in the PPR can be generated by switching the VO2 from one phase to another. We have measured the switching behavior of VO2 and Au::VO2 structures using shuttered CW laser irradiation in order to study both optical and thermal mechanisms of the phase transition. Transient absorption measurements using a shuttered 785 nm pump laser corresponding to the PPR resonance of the Au NPs and 1550 nm CW probe show that the presence of the Au NPs lowers the threshold laser power required to induce the phase transition.

  10. Evaluation of Carbon Dioxide Laser in the Treatment of Epidermal Nevi

    PubMed Central

    Bhat, Yasmeen Jabeen; Hassan, Iffat; Sajad, Peerzada; Yaseen, Atiya; Mubashir, Syed; Akhter, Saniya; Wani, Roohi

    2016-01-01

    Background: Epidermal naevi are benign hamartomatous growths of the skin which are generally asymptomatic with a benign course but are cosmetically disagreeable. Topical treatments such as steroids, calcipotriol, 5 fluorouracil, podophyllin, retinoids and cryotherapy are ineffective and surgical excision results in scar formation. Therapy is often challenging. Aim of the Study: To study the response of carbon dioxide (CO2) laser in the management of epidermal naevi. Subjects and Methods: We conducted a study of CO2 laser treatment on 15 patients of epidermal naevi, eight with verrucous epidermal naevi and seven with sebaceous naevi. A thorough history and examination was done to rule out any epidermal naevus syndrome. The diagnosis was confirmed by histopathology. The number of treatment sessions varied from 1 to 8. Results: Response was excellent (>90% reduction in lesion size) in three patients, very good (>75% reduction) in five, good (>50% reduction in lesion size) in five and poor (<50% reduction in lesion size) in two patients. The side effects were hyperpigmentation and scarring. Long-term follow-up over a period of 10 months showed a recurrence rate of 20%. Conclusion: We conclude that CO2 laser treatment might be an effective option with long-term safety, minimal discomfort and rapid recovery. PMID:27761089

  11. Method to produce a short pulse on rf discharge excitation slab-type carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Mori, Akira; Suzuki, Kaoru; Nakata, Junji

    1998-10-01

    We propose a novel system to produce the short pulse using a halved confocal of the unstable concave-convex resonator on radio frequency discharge excitation slab type carbon dioxide laser. This method is provided a full reflection concave mirror to have a function of variable curvature which can control using a piezo electric device (PZT). Generally, the slab type laser is directly modulated by applying pulse voltage for pulsation of laser. There is a large capacity and fluctuation of plasma at the transition of pulsation. Consequently, the pulse width is longer than 1.0 micro second and repetitive frequency is less than 10 kilo Hertz. On the other hand, the pulse oscillation by our proposed method has the short pulse width which is 300 nano second and maximum repetitive frequency is about 100 kilo Hertz. We can choose the pulse oscillation or the continuous wave (CW) oscillation at the each condition on same resonator. The peak power at the pulse oscillation is about 12 times as high as that at the CW oscillation.

  12. Extended emission wavelength of random dye lasers by exploiting radiative and non-radiative energy transfer

    NASA Astrophysics Data System (ADS)

    Wan Ismail, Wan Zakiah; Goldys, Ewa M.; Dawes, Judith M.

    2016-02-01

    We demonstrate long-wavelength operation (>700 nm) of random dye lasers (using a methylene blue dye) with the addition of rhodamine 6G and titania, enabled by radiative and non-radiative energy transfer. The pump energy is efficiently absorbed and transferred to the acceptors, to support lasing in random dye lasers in the near infrared. The optimum random laser performance with the highest emission intensity and the lowest lasing threshold was achieved for a concentration of methylene blue as the acceptor equal to 6× the concentration of rhodamine 6G (donor). Excessive levels of methylene blue increased the lasing threshold and broadened the methylene blue emission linewidth due to dye quenching from re-absorption. This is due to competition between the donor emission and energy transfer and between absorption loss and fluorescence quenching. The radiative and non-radiative energy transfer is analyzed as a function of the acceptor concentration and pump energy density, with consideration of the spectral overlap. The dependence of the radiative and non-radiative transfer efficiency on the acceptor concentration is obtained, and the energy transfer parameters, including the radiative and non-radiative energy transfer rate constants ( K R and K NR), are investigated using Stern-Volmer analysis. The analysis indicates that radiative energy transfer is the dominant energy transfer mechanism in this system.

  13. Pulsed 2-micron Laser Transmitter For Carbon Dioxide Sensing From Space

    NASA Astrophysics Data System (ADS)

    Singh, U. N.; Yu, J.; Bai, Y.; Petros, M.

    2011-12-01

    Carbon dioxide (CO2) has been recognized as one of the most important greenhouse gases. It is essential for the study of global warming to accurately measure the CO2 concentration in the atmosphere and continuously record its variation. Studies of the carbon cycle are limited by the tools available to precisely measure CO2 concentrations by remote sensing. Active sensing, using the Integrated Path Differential Absorption (IPDA) approach, permits measurements day and night, at all latitudes and seasons. The development of a high pulse energy 2-μm laser transmitter for high-precision CO2 measurements from space leverages years of NASA investment in solid-state laser technology. Under NASA Laser Risk Reduction Program, funded by Earth Science Technology Office, researchers at NASA Langley Research Center developed an injection seeded, high repetition rate, Q-switched Ho:YLF laser transmitter for CO2 Differential Absorption Lidar/IPDA (profile/column) measurements from ground and airborne platforms. This master-slave laser system has high optical-to-optical efficiency and seeding success rate. NASA LaRC's 2-micron pulsed laser transmitter possesses advantages over current passive and CW active sensors. First, the pulsed format provides a built-in means for determining range to the scattering target and effectively filtering out the scattering from thin clouds and aerosols, thus eliminating a source of measurement bias. Second, by concentrating the laser energy into a pulse, sufficient backscatter signal strength can be obtained from aerosol scattering rather than relying on a hard target at a known distance. Third, the absorption line at the 2.05 μm band is ideally suited for the CO2 concentration measurement. In particular, the weighting function of 2 μm is optimum for measurement in the lower troposphere where the sources and sinks of CO2 are located. The planned laser transmitter development will lead to a Tm:Fiber pumped Ho:YLF laser transmitter capable of

  14. Undulator radiation driven by laser-wakefield accelerator electron beams

    NASA Astrophysics Data System (ADS)

    Wiggins, S. M.; Anania, M. P.; Welsh, G. H.; Brunetti, E.; Cipiccia, S.; Grant, P. A.; Reboredo, D.; Manahan, G.; Grant, D. W.; Jaroszynski, D. A.

    2015-05-01

    The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) programme is developing laserplasma accelerators for the production of ultra-short electron bunches with subsequent generation of coherent, bright, short-wavelength radiation pulses. The new Scottish Centre for the Application of Plasma-based Accelerators (SCAPA) will develop a wide range of applications utilising such light sources. Electron bunches can be propagated through a magnetic undulator with the aim of generating fully coherent free-electron laser (FEL) radiation in the ultra-violet and Xrays spectral ranges. Demonstration experiments producing spontaneous undulator radiation have been conducted at visible and extreme ultra-violet wavelengths but it is an on-going challenge to generate and maintain electron bunches of sufficient quality in order to stimulate FEL behaviour. In the ALPHA-X beam line experiments, a Ti:sapphire femtosecond laser system with peak power 20 TW has been used to generate electron bunches of energy 80-150 MeV in a 2 mm gas jet laser-plasma wakefield accelerator and these bunches have been transported through a 100 period planar undulator. High peak brilliance, narrow band spontaneous radiation pulses in the vacuum ultra-violet wavelength range have been generated. Analysis is provided with respect to the magnetic quadrupole beam transport system and subsequent effect on beam emittance and duration. Requirements for coherent spontaneous emission and FEL operation are presented.

  15. Computation of reacting flowfield with radiation interaction in chemical lasers

    SciTech Connect

    Quan, V.; Persselin, S.F.; Yang, T.T.

    1982-01-01

    A numerical procedure has been developed to provide a rapid and stable solution of the reacting and radiating flowfield in chemical laser cavities. A marching technique, implicit in both fluid mechanics and chemistry, is employed in solving the two-dimensional mixing layer equations. The aerokinetics and radiation interaction is calculated iteratively by solving the aerokinetic equations for the gain distribution and the propagation equations for the radiation field. In the iterative solution, a linearization method which leads to enhanced numerical efficiency is employed.

  16. Analysis of metal surfaces coated with europium-doped titanium dioxide by laser induced breakdown spectroscopy.

    PubMed

    Głogocka, Daria; Noculak, Agnieszka; Pucińska, Joanna; Jopek, Wojciech; Podbielska, Halina; Langner, Marek; Przybyło, Magdalena

    2015-01-01

    The surface passivation with titanium sol-gel coatings is a frequently used technique to control the adsorption of selected biological macromolecules and to reduce the exposure of the bulk material to biological matter. Due to the increasing number of new coating-preparation methods and new gel compositions with various types of additives, the quality and homogeneity determination of the surface covering is a critical factor affecting performance of any implanted material. While coating thickness is easy to determine, the homogeneity of the surface distribution of coating materials requires more elaborate methodologies. In the paper, the laser induced breakdown spectroscopy (LIBS) based method, capable to quantitate the homogeneity and uniformity of the europium in titanium dioxide sol-gel coatings on stainless steel surfaces prepared with two different procedures: spin-coating and dip-coating, is presented. The emission intensity of titanium has been used to determine the coating thickness whereas the relative values of europium and titanium emission intensities provide data on the coating homogeneity. The obtained results show that the spin-coating technique provides better surface coverage with titanium dioxide. However, when the surface coating compositions were compared the dip-coating technique was more reliable.

  17. Radiocarbon dioxide detection based on cavity ring-down spectroscopy and a quantum cascade laser.

    PubMed

    Genoud, G; Vainio, M; Phillips, H; Dean, J; Merimaa, M

    2015-04-01

    Monitoring of radiocarbon (C14) in carbon dioxide is demonstrated using mid-infrared spectroscopy and a quantum cascade laser. The measurement is based on cavity ring-down spectroscopy, and a high sensitivity is achieved with a simple setup. The instrument was tested using a standardized sample containing elevated levels of radiocarbon. Radiocarbon dioxide could be detected from samples with an isotopic ratio C14/C as low as 50 parts-per-trillion, corresponding to an activity of 5  kBq/m(3) in pure CO(2), or 2  Bq/m(3) in air after extraction of the CO(2) from an air sample. The instrument is simple, compact, and robust, making it the ideal tool for on-site measurements. It is aimed for monitoring radioactive gaseous emissions in a nuclear power environment, during the operation and decommissioning of nuclear power plants. Its high sensitivity also makes it the ideal tool for the detection of leaks in radioactive waste repositories. PMID:25831328

  18. Analysis of metal surfaces coated with europium-doped titanium dioxide by laser induced breakdown spectroscopy.

    PubMed

    Głogocka, Daria; Noculak, Agnieszka; Pucińska, Joanna; Jopek, Wojciech; Podbielska, Halina; Langner, Marek; Przybyło, Magdalena

    2015-01-01

    The surface passivation with titanium sol-gel coatings is a frequently used technique to control the adsorption of selected biological macromolecules and to reduce the exposure of the bulk material to biological matter. Due to the increasing number of new coating-preparation methods and new gel compositions with various types of additives, the quality and homogeneity determination of the surface covering is a critical factor affecting performance of any implanted material. While coating thickness is easy to determine, the homogeneity of the surface distribution of coating materials requires more elaborate methodologies. In the paper, the laser induced breakdown spectroscopy (LIBS) based method, capable to quantitate the homogeneity and uniformity of the europium in titanium dioxide sol-gel coatings on stainless steel surfaces prepared with two different procedures: spin-coating and dip-coating, is presented. The emission intensity of titanium has been used to determine the coating thickness whereas the relative values of europium and titanium emission intensities provide data on the coating homogeneity. The obtained results show that the spin-coating technique provides better surface coverage with titanium dioxide. However, when the surface coating compositions were compared the dip-coating technique was more reliable. PMID:26687457

  19. Inverse-Transition Radiation Laser Acceleration Experiments at SLAC

    SciTech Connect

    Colby, Eric R.; Ischebeck, R.; Mcguinness, C.; Noble, R.J.; Sears, CMS; Siemann, Robert H.; Spencer, James E.; Walz, D.R.; Byer, R.L.; Plettner, T.; /Stanford U., Phys. Dept.

    2008-01-16

    We present a series of laser-driven particle acceleration experiments that are aimed at studying laser-particle acceleration as an inverse-radiation process. To this end we employ a semi-open vacuum setup with a thin planar boundary that interacts with the laser and the electromagnetic field of the electron beam. Particle acceleration from different types of boundaries will be studied and compared to the theoretical expectations from the Inverse-radiation picture and the field path integral method. We plan to measure the particle acceleration effect from transparent, reflective, black, and rough surface boundaries. While the agreement between the two acceleration pictures is straightforward to prove analytically for the transparent and reflective boundaries the equivalence is not clear-cut for the absorbing and rough-surface boundaries. Experimental observation may provide the evidence to distinguish between the models.

  20. Laser sources in dentistry and radiation safety regulations

    NASA Astrophysics Data System (ADS)

    De Luca, D.; Gaeta, G. M.; Lepore, M.

    2007-02-01

    Nowadays laser sources are largely adopted in dentistry due to their unique properties making them good candidates to substitute traditional scalpel and conventional diamond bur in the surgery of the soft and hard oral tissue, respectively. The large use of laser sources outside the research laboratories without the need of highly specialized personnel can ask for a widespread knowledge of safety issues related to this kind of equipment. The main hazard of accidental exposures regards eyes injury but increasing the power of the laser beam also skin can be involved. Safety legislations in Europe and U.S.A. take into account non ionizing radiations and laser radiation for the hazards for the health deriving from physical agents. Laser safety standards introduce 3 useful parameters for hazard characterization: "Accessible Emission Limit" (AEL), "Maximum Permissible Exposure" (MPE) and "Nominal Ocular Hazard Distance" (NOHD). We measured the MPE and NOHD for Er:YAG and other laser sources currently adopted in dentistry and we compared our results with data elaborated from standards in order to single out safe and comfortable working conditions. In fact an experimental assessment of the hazard parameters and the comparison with those of reference from safety standards turns out to be useful in order to estimate the residual hazard that can be still present after applying all the engineering protection and administrative rules.

  1. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Temporal and thermodynamic characteristics of plasma formation

    NASA Astrophysics Data System (ADS)

    Ignatavichyus, M. V.; Kazakyavichyus, É.; Orshevski, G.; Danyunas, V.

    1991-11-01

    An investigation was made of plasma formation accompanying the interaction with aluminum, iron, and VK-6 alloy targets of nanosecond radiation from a YAG:Nd3+ laser (Emax = 50 mJ, τ = 3-8 ns). The duration of the plasma formation process depended weakly on the laser radiation parameters [the power density was varied in the range 1-3 GW/cm2, the pulse rise time in the range 2-8 ns, or the rate of rise of the power density in the range (1-8) × 108 W · cm - 2 · ns -1]. A study was made of the establishment of a local thermodynamic equilibrium in a plasma jet excited by radiation from nanosecond and picosecond (E = 30 mJ, τ = 40 ps) lasers. The maximum of the luminescence from an aluminum plasma excited by picosecond laser radiation was found to correspond to a local thermodynamic equilibrium. A local thermodynamic equilibrium could be absent in the case of excitation by nanosecond laser radiation.

  2. Facet joint laser radiation: tissue effects of a new clinical laser application

    NASA Astrophysics Data System (ADS)

    Werkmann, Klaus; Thal, Dietmar R.

    1996-01-01

    Chronic unilateral and bilateral back pain with pseudoradicular symptoms, is a common clinical syndrome, which in many cases can be related to the facet joint syndrome. The pain is caused by mechanical affection of synovial and capsular nerve terminals. Therefore, current therapeutical attempts including physical therapy, intra-articular injection of local anesthetics and steroids and thermocoagulation of the facet joint with a thermocoagulator, are performed. We confirmed laser coagulation of the facet joint. Porcine cadaveric spines were treated immediately after death by intra-articular facet joint laser radiation. With the pulsed Nd:YAG laser (1064 nm) altogether 600 J were applied in three different places 4 mm apart at the top of the facet joint. The results showed that facet joint laser radiation leads to a small (about 1 - 2 mm diameter) lesion restricted to the facet joint cavity and its synovia. Histologically, we found a central carbonization zone and necrosis, including almost the whole cartilage and approximately 0.2 mm of the adjacent bone. These changes are similar to Nd:Yag-laser applications in other skeletal regions. It is suggested that these changes may lead to facet joint denervation by coagulation of the synovial nerve terminals. Cicatration of the laser lesion might cause ankylosis of this joint. In sum, facet joint laser radiation could be an alternative therapeutical tool for lower back pain of the facet joint syndrome type. Therefore, future clinical application of this technique seems to be very promising.

  3. Simulating radiative shocks with the CRASH laser package

    NASA Astrophysics Data System (ADS)

    van der Holst, B.; Tóth, G.; Sokolov, I. V.; Torralva, B. R.; Powell, K. G.; Drake, R. P.; Klapisch, M.; Busquet, M.; Fryxell, B.; Myra, E. S.

    2013-03-01

    We present the latest improvements in the Center for Radiative Shock Hydrodynamics (CRASH) code, a parallel block-adaptive-mesh Eulerian code for simulating high-energy-density plasmas. The implementation can solve for radiation models with either a gray or a multigroup method in the flux-limited-diffusion approximation. The electrons and ions are allowed to be out of temperature equilibrium and flux-limited electron thermal heat conduction is included. We have recently implemented a CRASH laser package with 3-D ray tracing, resulting in improved energy deposition evaluation. New, more accurate opacity models are available which significantly improve radiation transport in materials like xenon. In addition, the HYPRE preconditioner has been added to improve the radiation implicit solver. With this updated version of the CRASH code we study radiative shock tube problems. In our set-up, a 1 ns, 3.8 kJ laser pulse irradiates a 20 micron beryllium disk, driving a shock into a xenon-filled plastic tube. The electrons emit radiation in the shocked xenon. This radiation preheats the unshocked xenon. Photons traveling ahead of the shock will also interact with the plastic tube, heat it, and in turn this can drive another shock off the wall into the xenon.

  4. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Low-threshold generation of harmonics and hard x radiation in a laser plasma. 1. Single-peak generation

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.; Derzhavin, S. I.; Kazakov, K. Kh

    1993-02-01

    A source of hard x radiation based on a laser plasma has been studied under conditions such that parametric instabilities are driven in the plasma at low intensities of the pump radiation (below 10 GW/cm2). A qualitative interpretation of the observed effects is offered.

  5. Optimization of THz Radiation Generation from a Laser Wakefield Accelerator

    SciTech Connect

    Plateau, G. R.; Matlis, N. H.; Toth, C.; Geddes, C. G. R.; Schroeder, C. B.; Tilborg, J. van; Albert, O.; Esarey, E.; Leemans, W. P.

    2009-01-22

    Ultrashort terahertz pulses with energies in the {mu}J range can be generated with laser wakefield accelerators (LWFA), which are novel, compact accelerators that produce ultrashort electron bunches with energies up to 1 GeV and energy spreads of a few-percent. Laser pulses interacting with a plasma create accelerated electrons which upon exiting the plasma emit terahertz pulses via transition radiation. Because these electron bunches are ultrashort (<50 fs), they can radiate coherently (coherent transition radiation--CTR) in a wide bandwidth ({approx}1-10 THz) yielding high intensity terahertz pulses. In addition to providing a non-invasive bunch-length diagnostic and thus feedback for the LWFA, these high peak power THz pulses are suitable for high field (MV/cm) pump-probe experiments. Here we present energy-based measurements using a Golay cell and an electro-optic technique which were used to characterize these THz pulses.

  6. Characteristics of betatron radiation from direct-laser-accelerated electrons.

    PubMed

    Huang, T W; Robinson, A P L; Zhou, C T; Qiao, B; Liu, B; Ruan, S C; He, X T; Norreys, P A

    2016-06-01

    Betatron radiation from direct-laser-accelerated electrons is characterized analytically and numerically. It is shown here that the electron dynamics is strongly dependent on a self-similar parameter S(≡n_{e}/n_{c}a_{0}). Both the electron transverse momentum and energy are proportional to the normalized amplitude of laser field (a_{0}) for a fixed value of S. As a result, the total number of radiated photons scales as a_{0}^{2}/sqrt[S] and the energy conversion efficiency of photons from the accelerated electrons scales as a_{0}^{3}/S. The particle-in-cell simulations agree well with the analytical scalings. It is suggested that a tunable high-energy and high-flux radiation source can be achieved by exploiting this regime. PMID:27415373

  7. Generation of picosecond pulses in a dye laser excited by radiation from an argon laser with passively locked modes

    SciTech Connect

    Vinogradova, A.A.; Krindach, D.P.; Nazarov, B.I.; Tsapenko, A.M.

    1980-01-01

    Passive locking of argon laser modes was used in generation of tunable picosecond pulses in a synchronously excited dye laser. An experimental study was made of the characteristics of the dye laser radiation as a function of the argon laser characteristics.

  8. Ablation of biological tissues by radiation of strontium vapor laser

    SciTech Connect

    Soldatov, A. N. Vasilieva, A. V.

    2015-11-17

    A two-stage laser system consisting of a master oscillator and a power amplifier based on sources of self- contained transitions in pairs SrI and SrII has been developed. The radiation spectrum contains 8 laser lines generating in the range of 1 – 6.45 μm, with a generation pulse length of 50 – 150 ns, and pulse energy of ∼ 2.5 mJ. The divergence of the output beam was close to the diffraction and did not exceed 0.5 mrad. The control range of the laser pulse repetition rate varied from 10 to 15 000 Hz. The given laser system has allowed to perform ablation of bone tissue samples without visible thermal damage.

  9. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Low-threshold generation of harmonics and hard x radiation in a laser plasma. 2. Multipeak generation

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.; Derzhavin, S. I.; Kazakov, K. Kh

    1993-02-01

    The conditions for the generation of hard x radiation with a multipeak structure in a plasma pumped by a long pulse from a free-running CO2 laser at a low intensity (q≲10 GW/cm2) have been studied. This x-ray generation had been observed in a previous study by the present authors. It is shown that this generation of hard x radiation with a multipeak structure leads to a more than tenfold increase in the yield of hard x radiation per laser pulse, under optimum conditions. This increase results from the additional peaks in the x-ray signal. An explanation of this effect is proposed.

  10. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Formation of amplified spontaneous radiation in an expanding laser plasma allowing for refraction

    NASA Astrophysics Data System (ADS)

    Gulov, A. V.; Derzhiev, V. I.; Zhidkov, A. G.; Terskikh, A. O.; Yakovlenko, Sergei I.

    1990-06-01

    Calculations are made of the divergence of amplified spontaneous radiation in a laser plasma allowing for refraction by free electrons. An analysis is made of the divergence of the radiation generated due to a 3p→3s' transition in neon-like ions. Calculations are made of the divergence of the radiation due to the 4→3 transition in the O VIII ion allowing for refraction during expansion of a Formvar plasma.

  11. An Open-Path Tunable Diode Laser Sensor for Simultaneous Measurement of Methane And Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Bailey, D. M.; Adkins, E. M.; Wilson, E. L.; Miller, J. H. H.

    2014-12-01

    In a collaboration between NASA Goddard Space Flight Center, University of Alaska-Fairbanks, and George Washington University a study of the feedbacks to climate change caused by thawing permafrost has been initiated. An array of ground experiments at three unique permafrost sites will record permafrost depth, structure, meteorological data, and emissions of key greenhouse gases during a springtime permafrost thaw. Ground data will be linked to climate models and landscape structure from satellite imagery to gauge the magnitude of the feedbacks. GWU will deploy an open path instrument for independent measurement of ground-level carbon dioxide and methane. For several decades, our laboratory has developed diode laser absorption techniques using mid-infrared diode lasers as well as cavity- enhanced absorption measurements using near-infrared source. In the current project, we will continue to develop a system for open path measurements that builds on our past experience with deployment of multi-laser, multi species sensors. Spectral simulations suggest that at ambient levels of CO2 and CH4 (390 and 2 ppmV, respectively) we will observe extinction coefficients of ≈ 10-4 m-1 or ≈ 1% absorption over a 200 m path. Prior work in our laboratory suggests that a SNR in excess of 100 will be achievable at these absorption levels using wavelength-modulation techniques. Wavelength modulation spectroscopy entails applying a small amplitude modulation (on the order of the width of a spectral feature) to a laser's emitted frequency as it tunes through a spectrum. This is readily accomplished with near infrared telecom lasers whose frequency can be swept by varying the injection current going into the laser at fixed temperature. By sampling the detector's signal at a multiple of the modulation frequency, the resulting signal takes on the appearance of the spectrum's derivative. Typically, this is accomplished using a lock-in amplifier. To avoid the power burden of this

  12. Determination of laser-evaporated uranium dioxide by neutron activation analysis

    SciTech Connect

    Allred, R.

    1987-05-01

    Safety analyses of nuclear reactors require information about the loss of fuel which may occur at high temperatures. In this study, the surface of a uranium dioxide target was heated rapidly by a laser. The uranium surface was vaporized into a vacuum. The uranium bearing species condensed on a graphite disk placed in the pathway of the expanding uranium vapor. Scanning electron microscopy and X-ray analysis showed very little droplet ejection directly from the laser target surface. Neutron activation analysis was used to measure the amount of uranium deposited. The surface temperature was measured by a fast-response automatic optical pyrometer. The maximum surface temperature ranged from 2400 to 3700/sup 0/K. The Hertz-Langmuir formula, in conjunction with the measured surface temperature transient, was used to calculate the theoretical amount of uranium deposited. There was good agreement between theory and experiment above the melting point of 3120/sup 0/K. Below the melting point much more uranium was collected than was expected theoretically. This was attributed to oxidation of the surface. 29 refs., 16 figs., 7 tabs.

  13. Indoor carbon dioxide monitoring with diode laser absorption at 2 μm

    NASA Astrophysics Data System (ADS)

    Li, Jinyi; Du, Zhenhui; Ma, Yiwen; Liu, Jingwang

    2015-05-01

    In order to investigate the variation of indoor carbon dioxide concentration and how it changes with human activities, a tunable diode laser absorption spectroscopy (TDLAS) system was used to monitor the indoor CO2 concentration. Based on Wavelength Modulation Spectroscopy double frequency detection (WMS-2f), the 2v1+v3 characteristic line (4991.26 cm-1) of CO2 was measured by a DFB laser. The measured concentration values were calibrated by means of a cell filled with reference gas. The results show that the daily average indoor CO2 concentrations is about 419ppm which is slightly higher than that of the outdoor and the changing range is between 380ppm and 510ppm in a day. The indoor CO2 concentration was influenced by the change of ventilation and indoor staff. The respiration of the indoor staff makes a greater impact on a relatively confined indoor CO2 concentration. The CO2 increasing rate is measured to be 80ppm/hour in the case of occupant density of 0.06 people/m3. Therefore, the staff crowded indoor should ventilate timely to prevent excessive CO2 causing people discomfort.

  14. Influence of instrument conditions on the evaporation behavior of uranium dioxide with UV laser-assisted atom probe tomography

    SciTech Connect

    Valderrama, B.; Henderson, H.B.; Gan, J.; Manuel, M.V.

    2015-04-01

    Atom probe tomography (APT) provides the ability to detect subnanometer chemical variations spatially, with high accuracy. However, it is known that compositional accuracy can be affected by experimental conditions. A study of the effect of laser energy, specimen base temperature, and detection rate is performed on the evaporation behavior of uranium dioxide (UO2). In laser-assisted mode, tip geometry and standing voltage also contribute to the evaporation behavior. In this investigation, it was determined that modifying the detection rate and temperature did not affect the evaporation behavior as significantly as laser energy. It was also determined that three laser evaporation regimes are present in UO2. Very low laser energy produces a behavior similar to DC-field evaporation, moderate laser energy produces the desired laser-assisted field evaporation characteristic and high laser energy induces thermal effects, negatively altering the evaporation behavior. The need for UO2 to be analyzed under moderate laser energies to produce accurate stoichiometry distinguishes it from other oxides. The following experimental conditions providing the best combination of mass resolving power, accurate stoichiometry, and uniform evaporation behavior: 50 K, 10 pJ laser energy, a detection rate of 0.003 atoms per pulse, and a 100 kHz repetition rate.

  15. The spectroscopic foundation of radiative forcing of climate by carbon dioxide

    NASA Astrophysics Data System (ADS)

    Mlynczak, Martin G.; Daniels, Taumi S.; Kratz, David P.; Feldman, Daniel R.; Collins, William D.; Mlawer, Eli J.; Alvarado, Matthew J.; Lawler, James E.; Anderson, L. W.; Fahey, David W.; Hunt, Linda A.; Mast, Jeffrey C.

    2016-05-01

    The radiative forcing (RF) of carbon dioxide (CO2) is the leading contribution to climate change from anthropogenic activities. Calculating CO2 RF requires detailed knowledge of spectral line parameters for thousands of infrared absorption lines. A reliable spectroscopic characterization of CO2 forcing is critical to scientific and policy assessments of present climate and climate change. Our results show that CO2 RF in a variety of atmospheres is remarkably insensitive to known uncertainties in the three main CO2 spectroscopic parameters: the line shapes, line strengths, and half widths. We specifically examine uncertainty in RF due to line mixing as this process is critical in determining line shapes in the far wings of CO2 absorption lines. RF computed with a Voigt line shape is also examined. Overall, the spectroscopic uncertainty in present-day CO2 RF is less than 1%, indicating a robust foundation in our understanding of how rising CO2 warms the climate system.

  16. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Doppler backscattered-signal diagnostics of laser-induced surface hydrodynamic processes

    NASA Astrophysics Data System (ADS)

    Gordienko, Vyacheslav M.; Kurochkin, Nikolay N.; Markov, V. N.; Panchenko, Vladislav Ya; Pogosov, G. A.; Chastukhin, E. M.

    1995-02-01

    A method is proposed for on-line monitoring of laser industrial processing. The method is based on optical heterodyne measurements of the Doppler backscattering signal generated in the interaction zone. Qualitative and quantitative information on hydrodynamic flows in the interaction zone can be obtained. A report is given of measurements, carried out at cw CO2 laser radiation intensities up to 1 kW cm-2, on the surfaces of a number of condensed materials irradiated in the monostatic interaction configuration.

  17. Bleaching effect of a 405-nm diode laser irradiation used with titanium dioxide and 3.5% hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Sakai, K.; Kato, J.; Nakazawa, T.; Hirai, Y.

    2007-09-01

    A 405-nm diode laser has recently been developed for soft tissue problems in dentistry. A new in-office bleaching agent consisting of a titanium dioxide photocatalyst and 3.5% hydrogen peroxide has proven to react well with light irradiated at a wavelength of around 400 nm. In this study, we evaluated the bleaching efficacy of a newly developed 405-nm diode laser on bovine teeth treated with a bleaching agent composed of titanium dioxide and 3.5% hydrogen peroxide. Sixteen bovine incisors were randomly divided into two groups: Group A, irradiated by the 405-nm diode laser at 200 mW; Group B, irradiated by the 405-nm diode laser at 400 mW. The bleaching agent with titanium dioxide and 3.5% hydrogen peroxide was applied to bovine enamel and irradiated for 1 min. The specimens were then washed and dried, and the same procedure was repeated nine more times. After irradiation, we assessed the effects of bleaching on the enamel by measuring the color of the specimens with a spectrophotometer and examining the enamel surfaces with a scanning electron microscope. L* rose to a high score, reaching a significantly higher post-treatment level in comparison to pretreatment. In a comparison of the color difference (Δ E) between Group A and Group B, the specimens in Group B showed significantly higher values after 10 min of irradiation for the post-treatment. No remarkable differences in the enamel surface morphology were found between the unbleached and bleached enamel. The use of a 405-nm diode laser in combination with a bleaching agent of titanium dioxide and 3.5% hydrogen peroxide may be an effective method for bleaching teeth without the risk of tooth damage.

  18. Progress on High-Energy 2-micron Solid State Laser for NASA Space-Based Wind and Carbon Dioxide Measurements

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.

    2011-01-01

    Sustained research efforts at NASA Langley Research Center during last fifteen years have resulted in significant advancement of a 2-micron diode-pumped, solid-state laser transmitter for wind and carbon dioxide measurements from ground, air and space-borne platforms. Solid-state 2-micron laser is a key subsystem for a coherent Doppler lidar that measures the horizontal and vertical wind velocities with high precision and resolution. The same laser, after a few modifications, can also be used in a Differential Absorption Lidar system for measuring atmospheric CO2 concentration profiles. Researchers at NASA Langley Research Center have developed a compact, flight capable, high energy, injection seeded, 2-micron laser transmitter for ground and airborne wind and carbon dioxide measurements. It is capable of producing 250 mJ at 10 Hz by an oscillator and one amplifier. This compact laser transmitter was integrated into a mobile trailer based coherent Doppler wind and CO2 DIAL system and was deployed during field measurement campaigns. This paper will give an overview of 2-micron solid-state laser technology development and discuss results from recent ground-based field measurements.

  19. Infectious papillomavirus in the vapor of warts treated with carbon dioxide laser or electrocoagulation: Detection and protection

    SciTech Connect

    Sawchuk, W.S.; Weber, P.J.; Lowy, D.R.; Dzubow, L.M.

    1989-07-01

    Papillomavirus DNA has been reported recently in the vapor (smoke plume) derived from warts treated with carbon dioxide laser; this raises concerns for operator safety. We therefore have studied a group of human and bovine warts to define further the potential risk of wart therapy and to test whether a surgical mask could reduce exposure. Half of each wart was treated with carbon dioxide laser and the other half with electrocoagulation. The vapor produced by each form of therapy was collected with a dry filter vacuum apparatus and analyzed for the presence of papillomavirus. Vapor from human plantar warts was analyzed for the presence of human papillomavirus DNA, because there is no infectivity assay for human papillomavirus. Of plantar warts treated, five of eight laser-derived vapors and four of seven electrocoagulation-derived vapors were positive for human papillomavirus DNA. Greater amounts of papillomavirus DNA were usually recovered in the laser vapor than in the electrocoagulation vapor from the same wart. Bioassay readily detected infectious bovine papillomavirus in the vapor from bovine warts treated with either modality; more virus was present in laser-derived material. A surgical mask was found capable of removing virtually all laser- or electrocoagulation-derived virus, strongly suggesting that such masks can protect operators from potential inhalation exposure to papillomavirus.

  20. Investigation of ultrafast laser-driven radiative blast waves.

    PubMed

    Edwards, M J; MacKinnon, A J; Zweiback, J; Shigemori, K; Ryutov, D; Rubenchik, A M; Keilty, K A; Liang, E; Remington, B A; Ditmire, T

    2001-08-20

    We have examined the evolution of cylindrically symmetric blast waves produced by the deposition of femtosecond laser pulses in gas jets. In high- Z gases radiative effects become important. We observe the production of an ionization precursor ahead of the shock front and deceleration parameters below the adiabatic value of 1/2 (for a cylinder), an effect expected when the blast wave loses energy by radiative cooling. Despite significant radiative cooling, the blast waves do not appear to develop thin shell instabilities expected for strongly radiative waves. This is believed to be due to the stabilizing effect of a relatively thick blast wave shell resulting in part from electron thermal conduction effects. PMID:11497951

  1. EFFECTS OF LASER RADIATION ON MATTER: Influence of the ambient air pressure on short-wavelength radiation from a laser plasma

    NASA Astrophysics Data System (ADS)

    Golovin, A. F.; Zemtsov, S. S.; Fedyushin, B. T.

    1991-12-01

    A detailed experimental investigation was made of the radiation from a plasma created on an aluminum target by a pulsed CO2 laser at different ambient gas pressures. Measurements were made of the energy and angular distribution of the radiation and of the efficiency of conversion of laser energy into reemitted plasma radiation. The intensity of this radiation was found to exhibit pressure-dependent pulsations. The maximum reflection of the laser radiation from the plasma was recorded at a pressure of ~ 40 Torr. An interpretation is given of the experimental data.

  2. Atmospheric transmission of CO2 laser radiation with application to laser Doppler systems

    NASA Technical Reports Server (NTRS)

    Murty, S. S. R.

    1975-01-01

    The molecular absorption coefficients of carbon dioxide, water vapor, and nitrous oxide are calculated at the P16, P18, P20, P22, and P24 lines of the CO2 laser for temperatures from 200 to 300 K and for pressures from 100 to 1100 mb. The temperature variation of the continuum absorption coefficient of water vapor is taken into account semi-empirically from Burch's data. The total absorption coefficient from the present calculations falls within + or - 20 percent of the results of McClatchey and Selby. The transmission loss which the CO2 pulsed laser Doppler system experiences was calculated for flight test conditions for the five P-lines. The total transmission loss is approximately 7 percent higher at the P16 line and 10 percent lower at the P24 line compared to the P20 line. Comparison of the CO2 laser with HF and DF laser transmission reveals the P2(8) line at 3.8 micrometers of the DF laser is much better from the transmission point of view for altitudes below 10 km.

  3. Robust signatures of quantum radiation reaction in focused ultrashort laser pulses.

    PubMed

    Li, Jian-Xing; Hatsagortsyan, Karen Z; Keitel, Christoph H

    2014-07-25

    Radiation-reaction effects in the interaction of an electron bunch with a superstrong focused ultrashort laser pulse are investigated in the quantum radiation-dominated regime. The angle-resolved Compton scattering spectra are calculated in laser pulses of variable duration using a semiclassical description for the radiation-dominated dynamics and a full quantum treatment for the emitted radiation. In dependence of the laser-pulse duration we find signatures of quantum radiation reaction in the radiation spectra, which are characteristic for the focused laser beam and visible in the qualitative behavior of both the angular spread and the spectral bandwidth of the radiation spectra. The signatures are robust with respect to the variation of the electron and laser-beam parameters in a large range. Qualitatively, they differ fully from those in the classical radiation-reaction regime and are measurable with presently available laser technology.

  4. Experimental carbon dioxide laser brain lesions and intracranial dynamics. Part 2. Effect on brain water content and its response to acute therapy

    SciTech Connect

    Tiznado, E.G.; James, H.E.; Moore, S.

    1985-04-01

    Experimental brain lesions were created over the left parietooccipital cortex of the albino rabbit through the intact dura mater with high radiating carbon dioxide laser energy. The brain water content was studied 2, 6, and 24 hours after the insult. Another two groups of animals received acute therapy with either dexamethasone (1 mg/kg) or furosemide (1 mg/kg). In all groups, Evans blue extravasation uniformly extended from the impact crater into the surrounding white matter. The brain water content in the gray matter was elevated from the control value by 2 hours after impact and remained elevated at 6 and 24 hours. The white matter brain water content did not increase until 6 hours after impact and remained elevated in the 24-hour group. After dexamethasone treatment, there was a significant decrease of water in the gray matter, but not in the white matter. With furosemide therapy, there was no reduction of gray or white matter brain water.

  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. 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. PMID:27304296

  7. Heating of optical materials by pulsed CO2 laser radiation

    NASA Astrophysics Data System (ADS)

    Dmitriev, E. I.; Sakyan, A. S.; Starchenko, Aleksey N.; Goryachkin, Dmitri A.

    1998-12-01

    The results are presented on experimental investigations of action onto an optical glass BK-7 and some other materials of a CO2 laser radiation with the pulse duration of 20 - 70 microsecond(s) and the energy density of 0.1 - 3 J/cm2. The dynamics of a thermal response, temperature of heating and emissivity of irradiated glass samples are under consideration. The results obtained can be used in imaging techniques for objects selection.

  8. Radiation transfer in metallic-powder beds during laser forming

    SciTech Connect

    Gusarov, A V

    2010-08-03

    This paper presents numerical simulations of two-dimensional radiation transfer in a powder layer that resides on a substrate of the same material and is exposed to a normally incident laser beam with an axisymmetric bell-shaped or top-hat intensity profile. The powder layer is treated as an equivalent homogeneous absorbing/scattering medium with radiative properties defined by the reflectance of the solid phase, the porosity of the powder and its surface area. The model used is applicable when the laser beam diameter far exceeds the particle size of the powder. It is shown that the absorptance of an optically thick layer of opaque powder particles is a universal function of the absorptance of the solid phase and is independent of surface area and porosity, in agreement with experimental data in the literature. The fraction of laser energy absorbed in the powder-substrate system and that absorbed in the substrate decrease with an increase in the reflectance of the material, but the powder bed is then more uniformly heated. (laser technologies)

  9. Laser system for testing radiation imaging detector circuits

    NASA Astrophysics Data System (ADS)

    Zubrzycka, Weronika; Kasinski, Krzysztof

    2015-09-01

    Performance and functionality of radiation imaging detector circuits in charge and position measurement systems need to meet tight requirements. It is therefore necessary to thoroughly test sensors as well as read-out electronics. The major disadvantages of using radioactive sources or particle beams for testing are high financial expenses and limited accessibility. As an alternative short pulses of well-focused laser beam are often used for preliminary tests. There are number of laser-based devices available on the market, but very often their applicability in this field is limited. This paper describes concept, design and validation of laser system for testing silicon sensor based radiation imaging detector circuits. The emphasis is put on keeping overall costs low while achieving all required goals: mobility, flexible parameters, remote control and possibility of carrying out automated tests. The main part of the developed device is an optical pick-up unit (OPU) used in optical disc drives. The hardware includes FPGA-controlled circuits for laser positioning in 2 dimensions (horizontal and vertical), precision timing (frequency and number) and amplitude (diode current) of short ns-scale (3.2 ns) light pulses. The system is controlled via USB interface by a dedicated LabVIEW-based application enabling full manual or semi-automated test procedures.

  10. Molecular dynamics study of the bulk temperature effect on primary radiation damage in uranium dioxide

    NASA Astrophysics Data System (ADS)

    Martin, G.; Sabathier, C.; Wiktor, J.; Maillard, S.

    2015-06-01

    The effect of bulk temperature on the primary damage induced by a displacement cascade was investigated in uranium dioxide using classical molecular dynamics simulations. In this study, the Morelon potentials were used to model the middle-range interactions between the atoms that constitute the host matrix during the radiation events. Cascades were initiated by accelerating a uranium primary knock-on atom at 10keV inside a perfect UO2 lattice at a temperature between 700K and 1800K , a range which comprises in-pile temperatures of oxide fuels in light water reactors in standard operating conditions. Cascade overlap sequences were also simulated at 700K and 1400K in order to study the radiation damage accumulation in the oxide fuel. This study reveals the maximum damage level which the material can accommodate for decreases with the temperature. Furthermore the direct formation of vacancy clusters under irradiation is considerably slowed down above 1000K , notably during cascade overlap sequences.

  11. Nozzle flow of laser-heated radiating hydrogen with application to a laser-heated rocket

    NASA Technical Reports Server (NTRS)

    Kemp, N. H.; Root, R. G.

    1977-01-01

    This paper presents a model for the steady heating of flowing hydrogen by a CW 10.6 micron laser, to consider the feasibility of a laser-heated rocket. The hydrogen flow and the laser beam are parallel, and move into a converging-diverging nozzle. The absorption of laser energy is initiated by a laser-supported combustion wave. The hydrogen is in chemical equilibrium, absorbs laser energy by inverse Bremsstrahlung, and loses energy by radiation. The hydrogen flow was calculated from the rear of the LSC wave to the throat. Estimates of convective heat losses were made using a hydrogen boundary layer analysis. Specific impulse, obtained by expanding isentropically from the throat to 1 atm or a vacuum, varies from 1400 to 3000 s. Radiation losses are 5 to 20%, though the energy fluxes to the walls are quite high. Convective loss estimates are high enough to indicate that coupling to the hot gas flow is required for a 10 kW engine, but not for a 5 MW engine.

  12. Periodic nanostructures on titanium dioxide film produced using femtosecond laser with wavelengths of 388 nm and 775 nm.

    PubMed

    Shinonaga, Togo; Tsukamoto, Masahiro; Miyaji, Godai

    2014-06-16

    Titanium dioxide (TiO2) film is an important biomaterial used to improve the biocompatibility of titanium (Ti). We have used a film coating method with an aerosol beam and femtosecond laser irradiation to form periodic structures on biomaterials for control of the cell spreading. The control of cell spreading on biomaterials is important for the development of advanced biomaterials. In this study, nanostructures with periods of 130 and 230 nm were formed on a film using a femtosecond laser with wavelengths of 388 and 775 nm, respectively. The nanostructure period on the film was 30% of the laser wavelengths. Periods produced with wavelengths of 388 and 775 nm were calculated using a surface plasmon polariton (SPP) model and the experimental results for both wavelengths were in the range of the calculated periods, which suggests that the mechanism for the formation of the periodic nanostructures on the film with a femtosecond laser was due to the excitation of SPPs.

  13. The Effect of Intense Laser Radiation on Atomic Collisions

    NASA Astrophysics Data System (ADS)

    Young, Stephen Michael Radley

    1991-02-01

    Available from UMI in association with The British Library. Requires signed TDF. We have carried out theoretical and experimental studies into the effect of intense laser radiation on atomic collisions. The first experiment used neon. Excitation by electron impact in a gas discharge demanded a pressure of at least 0.075 Torr. Measurement of the intensity of 3^1S_0to 3^1P_1 fluorescence has been made for the case where high intensity ASE wings in the laser profile and background laser scatter are unimportant, with the laser tuned to resonance. The field intensity required to produce strong field fluorescence (exemplified by the Mollow triplet) was found to give rise to complications capable of screening the effects sought. Our theoretical model has suggested that at finite detunings, line-centre fluorescence will dominate Rayleigh scatter and omega_3 fluorescence. Our measurements provide information on the saturation of neon fluorescence but not of the variation of the intense field collision rate. Absorption of weak field 253.7 nm laser photons by ground state mercury atoms yielded a high 6 ^3P_1 population at a lower pressure of 0.02 Torr. The Mollow triplet has been observed in the self-broadened mercury system. Dressing of the upper transition (6^3P_1rightarrow 7^3S_1) by an intense laser close to 435.8 nm yielded the strong field signal. Polarisation studies were made possible by the 3-level mercury system (radiation trapping in a 2-level system would depolarise fluorescence) perturbed by argon. The studies yielded results that were explainable in terms of the selective population of Stark shifted dressed states by a detuned, weak probe field. Use has been made of the electric-dipole radiation selection rule m_{J}=0 rightarrow m_{J^' } = 0 unless J=J^' to devise a 'Stark shift collision switch'. The competition between collision and radiation induced transitions within the mercury atom has then been studied. The resonant, strong lambda 435.8 nm field was used

  14. Guiding of Laser Beams in Plasmas by Radiation Cascade Compression

    NASA Astrophysics Data System (ADS)

    Kalmykov, Serguei; Shvets, Gennady

    2006-11-01

    The near-resonant heatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few-fs electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the beat frequency. Consequently, the cascade of sidebands red- and blue-shifted from the fundamental by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion [S. Kalmykov and G. Shvets, Phys. Rev. E 73, 046403 (2006)]. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser frequency, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the multi-frequency laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. A train of high-intensity radiation spikes with continually evolving longitudinal profile can be self-guided over several Rayleigh lengths in homogeneous plasmas. High amplitude of the EPW is maintained over the entire propagation length. Numerical experiments on the electron acceleration in the cascade-driven (cascade-guided) EPW [using the code WAKE by P. Mora and T. M. Antonsen Jr., Phys. Plasmas 4, 217 (1997)] show that achieving GeV electron energy is possible under realistic experimental parameters.

  15. Guiding of Laser Beams in Plasmas by Radiation Cascade Compression

    SciTech Connect

    Kalmykov, Serguei; Shvets, Gennady

    2006-11-27

    The near-resonant heatwave excitation of an electron plasma wave (EPW) can be employed for generating trains of few-fs electromagnetic pulses in rarefied plasmas. The EPW produces a co-moving index grating that induces a laser phase modulation at the beat frequency. Consequently, the cascade of sidebands red- and blue-shifted from the fundamental by integer multiples of the beat frequency is generated in the laser spectrum. When the beat frequency is lower than the electron plasma frequency, the phase chirp enables laser beatnote compression by the group velocity dispersion [S. Kalmykov and G. Shvets, Phys. Rev. E 73, 046403 (2006)]. In the 3D cylindrical geometry, the frequency-downshifted EPW not only modulates the laser frequency, but also causes the pulse to self-focus [P. Gibbon, Phys. Fluids B 2, 2196 (1990)]. After self-focusing, the multi-frequency laser beam inevitably diverges. Remarkably, the longitudinal beatnote compression can compensate the intensity drop due to diffraction. A train of high-intensity radiation spikes with continually evolving longitudinal profile can be self-guided over several Rayleigh lengths in homogeneous plasmas. High amplitude of the EPW is maintained over the entire propagation length. Numerical experiments on the electron acceleration in the cascade-driven (cascade-guided) EPW [using the code WAKE by P. Mora and T. M. Antonsen Jr., Phys. Plasmas 4, 217 (1997)] show that achieving GeV electron energy is possible under realistic experimental parameters.

  16. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Selective metallisation of diamonds with the aid of laser radiation

    NASA Astrophysics Data System (ADS)

    Shafeev, Georgii A.; Pimenov, S. M.; Lubnin, Evgenii N.; Smolin, A. A.; Konov, Vitalii I.; Laptev, V. A.

    1995-02-01

    An experimental investigation was made of laser activation of diamond surfaces (single crystals and polycrystalline diamond films) prior to electroless before catalytic deposition of metals from solutions. The activation was carried out by a copper vapour laser or a KrF excimer laser in two ways: decomposition of a thin film of palladium acetylacetonate and local laser stimulated modification of the diamond surface by laser evaporation. An ohmic contact (Cu or Ni) with an adhesive strength of 3 N mm-2 was formed and the spatial resolution achieved was 10 μm.

  17. Excellent Aesthetic and Functional Outcome After Fractionated Carbon Dioxide Laser Skin Graft Revision Surgery: Case Report and Review of Laser Skin Graft Revision Techniques.

    PubMed

    Ho, Derek; Jagdeo, Jared

    2015-11-01

    Skin grafts are utilized in dermatology to reconstruct a defect secondary to surgery or trauma of the skin. Common indications for skin grafts include surgical removal of cutaneous malignancies, replacement of tissue after burns or lacerations, and hair transplantation in alopecia. Skin grafts may be cosmetically displeasing, functionally limiting, and significantly impact patient's quality-of-life. There is limited published data regarding skin graft revision to enhance aesthetics and function. Here, we present a case demonstrating excellent aesthetic and functional outcome after fractionated carbon dioxide (CO2) laser skin graft revision surgery and review of the medical literature on laser skin graft revision techniques. PMID:26580878

  18. Interaction of pulsed carbon dioxide laser beams with teeth in vitro.

    PubMed

    Brune, D

    1980-08-01

    Beams of pulsed carbon dioxide lasers with energy densities of about 10, 100 or 200 J/mm2 have been applied perpendicularly to third molars in vitro for the purpose of preparing cavities or pin holes for retention. A pulsed beam with an energy density of about 10 J/mm2 produced a hole approximately 2 mm deep with a diameter of about 0.2 mm. With a beam of 100 J/mm2 the hole produced penetrated the tooth to a depth of 4 mm. Minor cracks around the hole in both enamel and dentin could be observed. Around the position where the beam entered the enamel matrix a white mineralized layer was observed, while a brown discoloration was formed around the hole in the dentin at the beam exit. With an energy density of 200 J/mm2 the formation of cracks and discoloration was very pronounced. X-ray diffraction of lased tissue revealed an apatite structure. The wall in the lased hole exhibited a Vicker hardness number similar to that of enamel.

  19. Sub-ppb detection of nitrogen dioxide with an external cavity quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Lewicki, Rafal; Liu, Kun; Day, Timothy; Tittel, Frank K.

    2012-01-01

    Ultra-sensitive detection of nitrogen dioxide (NO2) in the ν3 fundamental band of NO2 using Faraday Rotation Spectroscopy (FRS) based optical sensor platform is reported. The FRS technique is well suited for selective trace gas measurements of paramagnetic species including the prominent air pollutants such as NO or NO2. In this paper a widely tunable external cavity quantum cascade laser (EC-QCL) is employed as an excitation source. The available EC-QCL mode-hop free tuning range between 1600 cm-1 and 1650 cm-1 allows to access the optimum for FRS technique 441<-440 Q-branch NO2 transition at 1613.2 cm-1 with an optical power of ~135 mW. In order to improve detection sensitivity and reduce size of the sensor platform, a custom made 22.47 cm long Herriott multipass gas cell (MPC) with a total effective optical path of 10.1 m was implemented. For a MPC configured NO2 FRS sensor operating in line-scanning mode a minimum detection limit of 1.6 ppbv (1σ) and 0.15 ppb (1σ) is achieved for a 1 sec and 100 sec averaging time, respectively. Preliminary results for long term measurements of atmospheric NO2 for the FRS sensor operating at an optimal pressure of 30 Torr and magnetic field of 200 Gaussrms were demonstrated.

  20. Er:YAG laser radiation applications in different medical branches

    NASA Astrophysics Data System (ADS)

    Jelínkova, Helena; Němec, Michal; Koranda, Petr; Šulc, Jan; Čech, Miroslav; Miyagi, Mitsunobu; Shi, Yi-Wei; Matsuura, Yuji

    2006-03-01

    For the purpose of biophotonics, free running and Q-switched Er:YAG lasers were constructed. As Q-switches the rotating mirror and Pockels cell were used. In the case of rotating mirror placed inside the resonator the maximum of generated laser energy was 210 mJ in a free-running mode regime when pulses up to 110 μs long (FWHM) were generated. The resulted parameters of the giant pulses were 30 mJ energy, and 250 ns pulse length. For the Pockels cell Q-switching, the laser was generating 325 mJ of energy in a 250 μs pulse, and 60 mJ of energy in a 60 ns pulse in the case of free running and Q-switched regime, respectively. This output properties together with the generating wavelength (2.94 μm), coinciding exactly with the absorption peak of water, giving us the possibility of using this radiation to the efficient interaction with biological tissue. The transport of the radiation to the interaction place was solved by the special cyclic olefin polymer coated silver hollow glass waveguides with the inner diameter of 700 μm and the length of 10 - 50 cm. For the contact treatment the sealed caps were used for preventing delivery system damage. The aim of this work was except of special laser systems development, the investigation ofthe effect differences between long (free running) and short (nanosecond) laser pulses on ophthalmic (cornea, sclera), urologic (ureter wall), or dental (enamel, dentine) tissue.

  1. Imprinting on empty hard gelatin capsule shells containing titanium dioxide by application of the UV laser printing technique.

    PubMed

    Hosokawa, Akihiro; Kato, Yoshiteru; Terada, Katsuhide

    2014-08-01

    The purpose of this study was to examine the application of ultraviolet (UV) laser irradiation to printing hard gelatin capsule shells containing titanium dioxide (TiO2) and to clarify how the color strength of the printing by the laser could be controlled by the power of the irradiated laser. Hard gelatin capsule shells containing 3.5% TiO2 were used in this study. The capsules were irradiated with pulsed UV laser at a wavelength of 355 nm. The color strength of the printed capsule was determined by a spectrophotometer as total color difference (dE). The capsules could be printed gray by the UV laser. The formation of many black particles which were agglomerates of oxygen-defected TiO2 was associated with the printing. In the relationship between laser peak power of a pulse and dE, there were two inflection points. The lower point was the minimal laser peak power to form the black particles and was constant regardless of the dosage forms, for example film-coated tablets, soft gelatin capsules and hard gelatin capsules. The upper point was the minimal laser peak power to form micro-bubbles in the shells and was variable with the formulation. From the lower point to the upper point, the capsules were printed gray and the dE of the printing increased linearly with the laser peak power. Hard gelatin capsule shells containing TiO2 could be printed gray using the UV laser printing technique. The color strength of the printing could be controlled by regulating the laser energy between the two inflection points.

  2. Generation and use of high power 213 nm and 266 nm laser radiation and tunable 210-400 nm laser radiation with BBO crystal matrix array

    DOEpatents

    Gruen, Dieter M.

    2000-01-01

    A 213 nm laser beam is capable of single photon ablative photodecomposition for the removal of a polymer or biological material substrate. Breaking the molecular bonds and displacing the molecules away from the substrate in a very short time period results in most of the laser photon energy being carried away by the displaced molecules, thus minimizing thermal damage to the substrate. The incident laser beam may be unfocussed and is preferably produced by quintupling the 1064 nm radiation from a Nd:YAG solid state laser, i.e., at 213 nm. In one application, the 213 nm laser beam is expanded in cross section and directed through a plurality of small beta barium borate (BBO) crystals for increasing the energy per photon of the laser radiation directed onto the substrate. The BBO crystals are arranged in a crystal matrix array to provide a large laser beam transmission area capable of accommodating high energy laser radiation without damaging the BBO crystals. The BBO crystal matrix array may also be used with 266 nm laser radiation for carrying out single or multi photon ablative photodecomposition. The BBO crystal matrix array may also be used in an optical parametric oscillator mode to generate high power tunable laser radiation in the range of 210-400 nm.

  3. Femtosecond electron beam generation and measurement for laser synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Uesaka, Mitsuru; Kinoshita, Kenichi; Watanabe, Takahiro; Ueda, Toru; Yoshii, Koji; Harano, Hideki; Nakajima, Kazuhisa; Ogata, Atsushi; Sakai, Fumio; Kotaki, Hideyuki; Kando, Masaki; Dewa, Hideki; Kondo, Shuji; Shibata, Yukio; Ishi, Kimihiro; Ikezawa, Mikio

    1998-02-01

    One of the S-band twin linacs (18L linac) of Nuclear Engineering Research Laboratory of University of Tokyo is modified in order to produce femtosecond electron single bunch for femtosecond X-ray generation via Thomson backward scattering, namely laser synchrotron radiation. Laser photocathode RF gun and chicane-type magnetic pulse compressor are installed at the S-band linac. 10 ps (FWHM) laser pulse generates 5 MeV, 10 ps (FWHM), 1 nC electron single bunch, which is accelerated up to 20 MeV in the S-band accelerating tube and compressed to 200 fs (FWHM) by the chicane. Design study has been performed by using the code of PARMELA and the installation has been finished. For precise and reliable measurement of the compressed pulse length, the comparison of measurement between the femtosecond streak camera and coherent transition radiation interferometry was carried out. Good agreement between them for 1-10 ps (FWHM) pulses was achieved. A new Michelson interferometer for the 200 fs pulse is now under construction.

  4. Radiation sources based on laser-plasma interactions.

    PubMed

    Jaroszynski, D A; Bingham, R; Brunetti, E; Ersfeld, B; Gallacher, J; van der Geer, B; Issac, R; Jamison, S P; Jones, D; de Loos, M; Lyachev, A; Pavlov, V; Reitsma, A; Saveliev, Y; Vieux, G; Wiggins, S M

    2006-03-15

    Plasma waves excited by intense laser beams can be harnessed to produce femtosecond duration bunches of electrons with relativistic energies. The very large electrostatic forces of plasma density wakes trailing behind an intense laser pulse provide field potentials capable of accelerating charged particles to high energies over very short distances, as high as 1GeV in a few millimetres. The short length scale of plasma waves provides a means of developing very compact high-energy accelerators, which could form the basis of compact next-generation light sources with unique properties. Tuneable X-ray radiation and particle pulses with durations of the order of or less than 5fs should be possible and would be useful for probing matter on unprecedented time and spatial scales. If developed to fruition this revolutionary technology could reduce the size and cost of light sources by three orders of magnitude and, therefore, provide powerful new tools to a large scientific community. We will discuss how a laser-driven plasma wakefield accelerator can be used to produce radiation with unique characteristics over a very large spectral range.

  5. Correction method of bending loss in the hollow optical fiber for endoscopic submucosal dissection using carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Kusakari, Daisuke; Hazama, Hisanao; Awazu, Kunio

    2015-03-01

    Endoscopic submucosal dissection using carbon dioxide laser is a promising treatment of early digestive cancer because it can avoid the risk of perforation. Although a hollow optical fiber transmitting mid-infrared light has been used, it was observed that the irradiation effect was influenced by bending a gastrointestinal gastrointestinal endoscope due to the change in transmittance by the bending loss. Therefore, we quantitatively evaluated the change in the irradiation effect by bending the hollow optical fiber in the gastrointestinal endoscope and proposed a correction method to stabilize the irradiation effect. First, the relationship between the irradiated laser energy density and the incision depth for porcine stomach was measured by bending the head of the gastrointestinal endoscope. Next, the relationship between the bending angle of the head of the gastrointestinal endoscope and the temperature rise of the hollow optical fiber in the head of the gastrointestinal endoscope was measured during the laser irradiation. As a result, the laser energy density and the incision depth decreased as the bending angle increased, and linear correlation between the laser energy density and the incision depth was observed. It was found that the bending angle can be estimated by the ratio of the setting laser power to time derivative of the temporal profile of the temperature of the hollow optical fiber. In conclusion, it is suggested that the correction of the laser energy density and stabilization of the incision capability is possible by measuring the temporal profile of the temperature of the hollow optical fiber.

  6. Thermomechanical effect of pulse-periodic laser radiation on cartilaginous and eye tissues

    NASA Astrophysics Data System (ADS)

    Baum, O. I.; Zheltov, G. I.; Omelchenko, A. I.; Romanov, G. S.; Romanov, O. G.; Sobol, E. N.

    2013-08-01

    This paper is devoted to theoretical and experimental studies into the thermomechanical action of laser radiation on biological tissues. The thermal stresses and strains developing in biological tissues under the effect of pulse-periodic laser radiation are theoretically modeled for a wide range of laser pulse durations. The models constructed allow one to calculate the magnitude of pressures developing in cartilaginous and eye tissues exposed to laser radiation and predict the evolution of cavitation phenomena occurring therein. The calculation results agree well with experimental data on the growth of pressure and deformations, as well as the dynamics of formation of gas bubbles, in the laser-affected tissues. Experiments on the effect of laser radiation on the trabecular region of the eye in minipigs demonstrated that there existed optimal laser irradiation regimens causing a substantial increase in the hydraulic permeability of the radiation-exposed tissue, which can be used to develop a novel glaucoma treatment method.

  7. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Spatial-temporal distribution of a mechanical load resulting from interaction of laser radiation with a barrier (analytic model)

    NASA Astrophysics Data System (ADS)

    Fedyushin, B. T.

    1992-01-01

    The concepts developed earlier are used to propose a simple analytic model describing the spatial-temporal distribution of a mechanical load (pressure, impulse) resulting from interaction of laser radiation with a planar barrier surrounded by air. The correctness of the model is supported by a comparison with experimental results.

  8. Comparison of the effect of the carbon dioxide laser and the bipolar coagulator on the cat brain

    SciTech Connect

    Cozzens, J.W.; Cerullo, L.J.

    1985-04-01

    The carbon dioxide laser has recently received clinical acceptance in neurosurgical practice. There are, however, few studies reported in the neurosurgical literature, either clinical or experimental, concerning its safety or efficacy on a physiological level by comparison to a more conventional tool. This study is not a description of a surgical technique, but is rather a basic physiological comparison of two surgical instruments. In this study, 11 cats were pretreated with the protein-bound dye, Evans blue. A corticotomy was performed in one hemisphere with the carbon dioxide laser and in the other with a microbipolar coagulator and a sharp blade. The subsequent extravasation of dye was presumed to be proportional to the amount of blood-brain barrier disruption associated with each lesion. When effective power settings for the two devices were compared, the laser lesions had significantly less extravasation of blue dye. This indicated that there was less damage to the blood-brain barrier surrounding laser corticotomy than surrounding conventional bipolar coagulation and sharp dissection at comparable power settings for each modality.

  9. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Emission of charged particles from the surface of a moving target acted on by cw CO2 laser radiation

    NASA Astrophysics Data System (ADS)

    Kuznetsov, S. I.; Petrov, A. L.; Shadrin, A. N.

    1990-06-01

    An experimental investigation was made of the emission of charged particles due to the irradiation of moving steel and graphite targets with cw CO2 laser radiation. The characteristics of the emission current signals were determined for different laser irradiation regimes. The maximum emission current density from the surface of a melt pool ( ~ 1.1 × 10 - 2 A/cm2) and the average temperature of the liquid metal (~ 2040 K) were measured for an incident radiation power density of 550 W and for horizontal and vertical target velocities of respectively ~ 1.5 mm/s and ~ 0.17 mm/s. The authors propose to utilize this phenomenon for monitoring the laser processing of materials.

  10. Xenon plasma sustained by pulse-periodic laser radiation

    SciTech Connect

    Rudoy, I. G.; Solovyov, N. G.; Soroka, A. M.; Shilov, A. O.; Yakimov, M. Yu.

    2015-10-15

    The possibility of sustaining a quasi-stationary pulse-periodic optical discharge (POD) in xenon at a pressure of p = 10–20 bar in a focused 1.07-μm Yb{sup 3+} laser beam with a pulse repetition rate of f{sub rep} ⩾ 2 kHz, pulse duration of τ ⩾ 200 μs, and power of P = 200–300 W has been demonstrated. In the plasma development phase, the POD pulse brightness is generally several times higher than the stationary brightness of a continuous optical discharge at the same laser power, which indicates a higher plasma temperature in the POD regime. Upon termination of the laser pulse, plasma recombines and is then reinitiated in the next pulse. The initial absorption of laser radiation in successive POD pulses is provided by 5p{sup 5}6s excited states of xenon atoms. This kind of discharge can be applied in plasma-based high-brightness broadband light sources.

  11. Mapping of laser diode radiation intensity by atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Alekseev, P. A.; Dunaevskii, M. S.; Slipchenko, S. O.; Podoskin, A. A.; Tarasov, I. S.

    2015-09-01

    The distribution of the intensity of laser diode radiation has been studied using an original method based on atomic-force microscopy (AFM). It is shown that the laser radiation intensity in both the near field and transition zone of a high-power semiconductor laser under room-temperature conditions can be mapped by AFM at a subwavelength resolution. The obtained patterns of radiation intensity distribution agree with the data of modeling and the results of near-field optical microscopy measurements.

  12. High repetition rate laser systems: targets, diagnostics and radiation protection

    SciTech Connect

    Gizzi, Leonida A.; Clark, Eugene; Neely, David; Tolley, Martin; Roso, Luis

    2010-02-02

    Accessing the high repetition regime of ultra intense laser-target interactions at small or moderate laser energies is now possible at a large number of facilities worldwide. New projects such as HiPER and ELI promise to extend this regime to the high energy realm at the multi-kJ level. This opportunity raises several issues on how best to approach this new regime of operation in a safe and efficient way. At the same time, a new class of experiments or a new generation of secondary sources of particles and radiation may become accessible, provided that target fabrication and diagnostics are capable of handling this rep-rated regime. In this paper, we explore this scenario and analyse existing and perspective techniques that promise to address some of the above issues.

  13. Self-heterodyne detection of backscattered radiation in single-mode CO{sub 2} lasers

    SciTech Connect

    Gordienko, Vyacheslav M; Konovalov, Aleksei N; Ul'yanov, V A

    2011-05-31

    Self-heterodyning in dc-discharge-pumped single-mode CO{sub 2} lasers is analysed theoretically and studied experimentally under strong and weak feedback conditions. Relations for the autodyne gain and modulation depth due to the effect of backscattered radiation with a Doppler-shifted frequency are obtained. Nonlinear distortions of the autodyne signal caused by a strong laser - target feedback are studied. It is shown that the autodyne detection of backscattered radiation in CO{sub 2} lasers can be considered linear even in the case of strong laser beam distortions (nonlinear distortions below 5%). (control of laser radiation parameters)

  14. Investigation of temperature feedback signal parameters during neoplasms treatment by diode laser radiation

    NASA Astrophysics Data System (ADS)

    Belikov, Andrey V.; Gelfond, Mark L.; Shatilova, Ksenia V.; Semyashkina, Yulia V.

    2016-04-01

    Dynamics of temperature signal in operation area and laser power at nevus, papilloma, and keratoma in vivo removal by a 980+/-10 nm diode laser with "blackened" tip operating in continuous (CW) mode and with temperature feedback (APC) mode are presented. Feedback allows maintaining temperature in the area of laser treatment at a preset level by regulating power of diode laser radiation (automatic power control). Temperature in the area of laser treatment was controlled by measuring the amplitude of thermal radiation, which occurs when tissue is heated by laser radiation. Removal of neoplasm was carried out in CW mode with laser radiation average power of 12.5+/-0.5 W; mean temperature in the area of laser treatment was 900+/-10°C for nevus, 800+/-15°C for papilloma, and 850+/-20°C for keratoma. The same laser radiation maximal power (12.5 W) and targeted temperature (900°C) were set for nevus removal in APC mode. The results of investigation are real time oscillograms of the laser power and temperature in the area of laser treatment at neoplasms removal in two described above modes. Simultaneously with the measurement of laser power and the temperature in the area of laser treatment video recording of surgeon manipulations was carried out. We discuss the correlation between the power of the laser radiation, the temperature in the area of laser treatment and consistency of surgeon manipulation. It is shown that the method of removal (excision with or without traction, scanning) influences the temperature in the area of laser treatment. It was found, that at removal of nevus with temperature feedback (APC) mode to achieve comparable with CW mode temperature in the area of laser treatment (900+/-10°C) 20-50% less laser power is required. Consequently, removing these neoplasms in temperature feedback mode can be less traumatic than the removal in CW mode.

  15. Laser readable thermoluminescent radiation dosimeters and methods for producing thereof

    DOEpatents

    Braunlich, Peter F.; Tetzlaff, Wolfgang

    1989-01-01

    Thin layer thermoluminescent radiation dosimeters for use in laser readable dosimetry systems, and methods of fabricating such thin layer dosimeters. The thin layer thermoluminescent radiation dosimeters include a thin substrate made from glass or other inorganic materials capable of withstanding high temperatures and high heating rates. A thin layer of a thermoluminescent phoshphor material is heat bonded to the substrate using an inorganic binder such as glass. The dosimeters can be mounted in frames and cases for ease in handling. Methods of the invention include mixing a suitable phosphor composition and binder, both being in particulate or granular form. The mixture is then deposited onto a substrate such as by using mask printing techniques. The dosimeters are thereafter heated to fuse and bond the binder and phosphor to the substrate.

  16. Laser readable thermoluminescent radiation dosimeters and methods for producing thereof

    DOEpatents

    Braunlich, P.F.; Tetzlaff, W.

    1989-04-25

    Thin layer thermoluminescent radiation dosimeters for use in laser readable dosimetry systems, and methods of fabricating such thin layer dosimeters are disclosed. The thin layer thermoluminescent radiation dosimeters include a thin substrate made from glass or other inorganic materials capable of withstanding high temperatures and high heating rates. A thin layer of a thermoluminescent phosphor material is heat bonded to the substrate using an inorganic binder such as glass. The dosimeters can be mounted in frames and cases for ease in handling. Methods of the invention include mixing a suitable phosphor composition and binder, both being in particulate or granular form. The mixture is then deposited onto a substrate such as by using mask printing techniques. The dosimeters are thereafter heated to fuse and bond the binder and phosphor to the substrate. 34 figs.

  17. Growing cartilage after IR laser radiation-ultrastructural study

    NASA Astrophysics Data System (ADS)

    Pelaez, A.; Vidal, Lourdes; Mendez, Luis I.; Parrado, C.; Perez de Vargas, I.

    1994-02-01

    The ultrastructural alterations of the chondrocytes in the growing cartilage after radiation by IR laser at a dose of 2 J/cm2 are described. Twenty albino Wistar rats have been used. The radiation was carried out on the left knee of the animals. Consequently, the animals were killed, and as soon as the pieces had been obtained they were subjected to the conventional techniques of fixation and inclusion for electron microscopy. Their ER is scarcely developed with disrupted and dilated cisternae noting few secretory vesicles in relation to the control animals. Likewise, degenerative phenomena in the mitochondria membranes and the endomembrane system were observed, in the shape of myelin. In the chondrocytes of the contralateral knee, few alterations were noted in relation to the controls.

  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. Dichromatic laser radiation effects on DNA of Escherichia coli and plasmids

    NASA Astrophysics Data System (ADS)

    Martins, W. A.; Polignano, G. A. C.; Guimarães, O. R.; Geller, M.; Paoli, F.; Fonseca, A. S.

    2015-04-01

    Dichromatic and consecutive laser radiations have attracted increased attention for clinical applications as offering new tools for the treatment of dysfunctional tissues in situations where monochromatic radiation is not effective. This work evaluated the survival, filamentation and morphology of Escherichia coli cells, and the induction of DNA lesions, in plasmid DNA exposed to low-intensity consecutive dichromatic laser radiation. Exponential and stationary wild type and formamidopyrimidine DNA glycosylase/MutM protein deficient E. coli cultures were exposed to consecutive low-intensity dichromatic laser radiation (infrared laser immediately after red laser) to study the survival, filamentation and morphology of bacterial cells. Plasmid DNA samples were exposed to dichromatic radiation to study DNA lesions by electrophoretic profile. Dichromatic laser radiation affects the survival, filamentation and morphology of E. coli cultures depending on the growth phase and the functional repair mechanism of oxidizing lesions in DNA, but does not induce single/double strands breaks or alkali-labile DNA lesions. Results show that low-intensity consecutive dichromatic laser radiation induces biological effects that differ from those induced by monochromatic laser radiation, suggesting that other therapeutic effects could be obtained using dichromatic radiation.

  20. Carbon dioxide laser as a surgical instrument for sarcoid therapy--a retrospective study on 60 cases.

    PubMed Central

    Carstanjen, B; Jordan, P; Lepage, O M

    1997-01-01

    The objective of this retrospective clinical study was to evaluate the carbon dioxide laser in the treatment of single and multiple sarcoids in 60 animals (44 horses, 13 donkeys, 2 mules, and 1 pony). Only animals that had been operated on 6 mo or more ago were included. Recurrence, new manifestation rate, and cosmetic outcome were determined. Recurrence was observed in 23 (38%) individuals. Animals with new sarcoid manifestation with or without recurrence of a sarcoid were observed in 35 cases (58%). Cases of scar tissue formation and, rarely, leukotrichia were observed. Animals presented with multiple sarcoids were more predisposed to recurrence. Donkeys showed a significantly lower recurrence rate than horses. PMID:9426943

  1. Inflammatory papillary hyperplasia of the palate: treatment with carbon dioxide laser, followed by restoration with an implant-supported prosthesis.

    PubMed

    Infante-Cossio, P; Martinez-de-Fuentes, R; Torres-Carranza, E; Gutierrez-Perez, J L

    2007-12-01

    Inflammatory papillary hyperplasia of the palate is a persistant non-neoplastic lesion that is normally caused by poorly fitting dentures and Candida infection. We describe a case that was managed primarily with topical miconazole, and complete removal of the old acrylic denture. A multidisciplinary approach between surgeon and prosthodontist was used that combined carbon dioxide laser followed by substitution of the old removable denture for a new implant-supported screw retained prosthesis. This avoided direct support of the prosthesis by the palatal mucosa and made oral hygiene easier. The treatment has resulted in complete remission and there has been no recurrence occurred during 3 years of follow-up.

  2. Synergistic effects of sequential carbon dioxide and neodymium:yttrium aluminum garnet laser injuries. Experimental observations and measurements

    SciTech Connect

    Primrose, W.J.; McDonald, G.A.; O'Brien, M.J.; Vaughan, C.W.; Strong, M.S.

    1987-01-01

    The carbon dioxide and neodymium:yttrium aluminum garnet lasers have well documented but characteristically different biological effects, yet little is known about their cumulative, synergistic, or paradoxical effects when used sequentially on living tissue. Using a Merrimack ML 880 laser, a series of superimposed CO/sub 2/ and Nd:YAG lesions in various combinations were produced on the undersurface of dog tongues. Therapeutic time and power settings were chosen and the number of applications varied, with suitable controls. Observations and measurements were made on acute, healing, and healed lesions. All lesions were excised and submitted for routine hematoxylin and eosin histology. Acute lesions were also assessed for cell viability using rhodamine 123 as a supravital marker. The results show that, even though all the lesions eventually heal, the actual cell damage produced by the Nd:YAG laser is much more than is suggested by the size of the acute lesion. This cell damage can be reduced by the surface carbonization produced by initial application of the CO/sub 2/ laser. Higher surface temperatures are reached in this combination with less fibrosis and scarring than equal energy counterparts where the Nd:YAG laser was applied first. The knowledge of these synergistic effects can be used to advantage in the clinical setting. The rhodamine 123 technique also appears to be a valid measure of acute thermal tissue injury.

  3. [The influence of ultrahigh-frequency electromagnetic radiation and low-intensity laser radiation on the body core temperature and basal metabolism in rats with systemic inflammation].

    PubMed

    Zhavoronok, I P; Molchanova, A Iu; Ulashik, V S

    2012-01-01

    The effects of ultrahigh-frequency electromagnetic radiation (UHF EMR) and low-intensity laser irradiation (LILI) on the body and skin temperature, oxygen consumption, production of carbon dioxide and heat release were investigated in the experiments on intact rats and during LPS-induced polyphasic fever. It was found that UHF EMR with the wavelength of 4,9 mm, 5,6 mm or 7,1 mm and LILI with the wavelength of 0.47 microm, 0.67 microm and 0.87 microm caused modulation of basal metabolism and thermal response to systemically administered lipopolysaccharide (LPS). These findings suggest that the most pronounced antipyretic and hypometabolic effects were observed after the treatment with UHF EMR at 7,1 mm and LILI at 470 microm.

  4. Terahertz radiation generation by nonlinear mixing of two laser beams over a thin foil

    SciTech Connect

    Chauhan, Santosh; Parashar, J.

    2015-07-31

    Terahertz radiation generation via nonlinear mixing of two laser beams incident over a thin metal foil is explored. The lasers exert a ponderomotive force on the electrons of metal foil at beat frequency which lies in the terahertz range. The metal foil acts as antenna, producing terahertz radiations, highly directional in nature.

  5. Mode structure in the far field radiation of a leaky-wave multiple quantum well laser

    SciTech Connect

    Nekorkin, S M; Zvonkov, B N; Karzanova, Maria V; Dikareva, Natalia V; Aleshkin, V Ya; Dubinov, A A

    2012-10-31

    The radiation patterns of a leaky-wave InGaAs/GaAs/InGaP laser are studied. In the subthreshold regime, several peaks are found, corresponding to the emission of fundamental and excited modes. The dependences of the amplitude, position and width of the peaks on the pump current are investigated and explained. (measurement of laser radiation parameters)

  6. Effects of Nd:YAG laser radiation in cultured porcine vertebral disc tissue

    NASA Astrophysics Data System (ADS)

    Thal, Dietmar R.; Werkmann, Klaus; Leheta, Fouad; Schober, Ralf; Ulrich, Peter

    1996-01-01

    Nd:Yag laser radiation is used for the treatment of protrusion of intervertebral discs. It is known that laser radiation leads to coagulation, vaporization and carbonization of the disk. Little is known about the early changes in vertebral discs after laser radiation. Therefore, we exposed cadaveric porcine vertebral discs by Nd:YAG laser radiation immediately after death. The discs were quartered and either formalin fixed after laser radiation or kept in culture for 1, 4 and 7 days and then formalin fixed. Immunohistochemistry was performed with antibodies directed against vimentin and amyloid precursor protein (APP). Results showed a jerky leak of notochordial remnant cells and mucopolysaccharides at the distal end of the application needle during laser radiation, which was interpreted as a bursting extrusion of damaged but not vaporized tissue. Histology and immunohistochemistry revealed an incomplete loss of nucleus pulposus and a large, almost complete necrosis of the notochordial remnant cells. In surviving notochordial remnant cells after laser radiation a slight increase of vimentin and APP could be seen without any other cellular reactions. The annulus fibrosus showed no significant changes except a defect with a small necrosis zone at the site of the application needle. Therefore, it can be concluded that Nd:YAG laser radiation leads to an increased volume reduction by the leak of nucleus pulposus and to a slight cellular reaction of surviving notochordal remnant cells detectable by vimentin and APP increase.

  7. Influence of terahertz laser radiation on the spectral characteristics and functional properties of albumin

    NASA Astrophysics Data System (ADS)

    Cherkasova, O. P.; Fedorov, V. I.; Nemova, E. F.; Pogodin, A. S.

    2009-10-01

    The exposure of albumin (transport protein of blood serum) to laser radiation with a frequency of 3.6 THz resulted in a change in the intensity of characteristic bands in UV absorption spectra and in circular dichroism spectra. These changes depend on the exposure duration and the laser radiation power and indicate conformational changes in protein molecules.

  8. Measurement of radiation produced by ultra short laser pulses interacting with solid targets

    SciTech Connect

    Fonseca, C.; Fernandez, F.; Mendez, C.; Ruiz, C.; Roso, L.

    2010-04-26

    Ionizing radiation was produced when ultra-short laser pulses collided obliquely on solid aluminium targets. As a result of the interaction, electrons and photons of some tens of keV were measured. We also analyzed the effect of laser polarization on the emitted radiation.

  9. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Effect of compression of a laser plasma on the generation of harmonics and hard x radiation

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.; Derzhavin, S. I.; Kazakov, K. Kh

    1993-02-01

    A compression of a plasma produced at a conical target by a low-intensity beam (q≲10 GW/cm2) from a CO2 laser has been studied. The effect of this compression on the onset of the parametric instability responsible for the generation of harmonics and of hard x radiation has also been studied. A qualitative interpretation of the results is offered.

  10. 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.

  11. Bursts of Terahertz Radiation from Large-Scale Plasmas Irradiated by Relativistic Picosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Liao, G. Q.; Li, Y. T.; Li, C.; Su, L. N.; Zheng, Y.; Liu, M.; Wang, W. M.; Hu, Z. D.; Yan, W. C.; Dunn, J.; Nilsen, J.; Hunter, J.; Liu, Y.; Wang, X.; Chen, L. M.; Ma, J. L.; Lu, X.; Jin, Z.; Kodama, R.; Sheng, Z. M.; Zhang, J.

    2015-06-01

    Powerful terahertz (THz) radiation is observed from large-scale underdense preplasmas in front of a solid target irradiated obliquely with picosecond relativistic intense laser pulses. The radiation covers an extremely broad spectrum with about 70% of its energy located in the high frequency regime over 10 THz. The pulse energy of the radiation is found to be above 1 0 0 μ J per steradian in the laser specular direction at an optimal preplasma scale length around 40 - 50 μ m . Particle-in-cell simulations indicate that the radiation is mainly produced by linear mode conversion from electron plasma waves, which are excited successively via stimulated Raman scattering instability and self-modulated laser wakefields during the laser propagation in the preplasma. This radiation can be used not only as a powerful source for applications, but also as a unique diagnostic of parametric instabilities of laser propagation in plasmas.

  12. Radiation damping effects on the interaction of ultraintense laser pulses with an overdense plasma.

    PubMed

    Zhidkov, A; Koga, J; Sasaki, A; Uesaka, M

    2002-05-01

    A strong effect of radiation damping on the interaction of an ultraintense laser pulse with an overdense plasma slab is found and studied via a relativistic particle-in-cell simulation including ionization. Hot electrons generated by the irradiation of a laser pulse with a radiance of I lambda(2)>10(22) W microm(2)/cm(2) and duration of 20 fs can convert more than 35% of the laser energy to radiation. This incoherent x-ray emission lasts for only the pulse duration and can be intense. The radiation efficiency is shown to increase nonlinearly with laser intensity. Similar to cyclotron radiation, the radiation damping may restrain the maximal energy of relativistic electrons in ultraintense-laser-produced plasmas.

  13. Theoretical foundations of detection of terahertz radiation in laser-plasma interactions

    SciTech Connect

    Frolov, A. A.

    2013-02-15

    A theory is developed enabling one to calculate the temporal profile and spectrum of a terahertz wave packet from the energy of the second harmonic of optical radiation generated during the nonlinear interaction between terahertz and circularly polarized laser pulses in the skin layer of an overdense plasma. It is shown that the spectral and temporal characteristics of the envelope of the second harmonic of optical radiation coincide with those of the terahertz pulse only at small durations of the detecting laser radiation. For long laser pulses, the temporal profile and spectrum of the second harmonic are mainly determined by the characteristics of optical radiation at the carrier frequency.

  14. Laser radiation of blood in treating patients with postinfarction heart

    NASA Astrophysics Data System (ADS)

    Tashchuk, V.; Polyanskaya, O.; Chaplinsky, R.; Ilashchuk, I.; Kulyk, T.

    1999-11-01

    168 patients on the postclinical stage of treatment of acute myocardial infarction were examined by means of the use of basic antiischemic therapy and intravenous laser radiation of blood (LRB). All patients were studied with the help of transesophageal electrocardiostimulation, bicycle ergometry, echocardiography and Holter ECG monitoring in the dynamics of prolonged observation and treatment. The analysis of efficiency of the LRB has shown that the most minimal degree of myocardial ischemization was marked in patients after intravenous LRB. The patients before LRB had the greater reduction of coronary reserve. The use of LRB has given the possibility to the optimization of therapy in patients on the stage of the forming of `the postinfarction heart'.

  15. Mobility of Electron in DNA Crystals by Laser Radiation

    NASA Technical Reports Server (NTRS)

    Zhang, Kaixi; Zhao, Qingxun; Cui, Zhiyun; Zhang, Ping; Dong, Lifang

    1996-01-01

    The mobility of electrons in laser radiated DNA is closed to the energy transfer and energy migration of a biological molecule. Arrhenius has studied the conductivity of the electrons in a biological molecule. But his result is far from the experimental result and meanwhile the relation between some parameters in his theory and the micro-quantities in DNA is not very clear. In this paper, we propose a new phonon model of electron mobility in DNA and use Lippman-Schwinger equation and S-matrix theory to study the mobility of electrons in DNA crystal. The result is relatively close to the experiment result and some parameters in Arrhenius theory are explained in our work.

  16. Recent progress in development of a laser based, ultra-high precision isotope monitor for carbon dioxide

    NASA Astrophysics Data System (ADS)

    Nelson, David; McManus, Barry; Herndon, Scott; Zahniser, Mark

    2015-04-01

    Greenhouse gas (GHG) emissions are the primary drivers of global climate change and hence there is a crucial need to quantify their sources and sinks. A general technique to help constrain source and sink strengths in GHG exchange processes is the analysis of the relative proportions of isotopic variants of GHG's. Very high precision measurements of isotopologue ratios are necessary in order to identify sources and sinks because the characteristic changes are small. The standard method of isotopologue measurement has been mass spectrometry, but this technique typically requires significant sample preparation and relatively high instrument maintenance. Laser spectroscopy has the potential to ease these burdens and also to allow easy separation of interfering isobars such as 13C-CO2 and 17O-CO2. We present recent results demonstrating ultra-high precision measurements of carbon dioxide isotope ratios which have the potential to rival the accuracy of mass spectrometric measurements. These measurements were performed using Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS). We have obtained isotopic measurement precisions of ~10 per meg for both 13C-CO2 and 18O-CO2 while measuring ambient air samples with continuous flow. We have also developed a method for analyzing air samples from canisters by alternately and rapidly trapping sample gas and reference gas in the optical cell. The ultimate goal is to create an automated, ultra-high accuracy carbon dioxide isotope monitor able to quantify small (~100 standard ml), discreet air samples. We will also discuss current instrument performance results and prospects for the measurement of the clumped isotopes of carbon dioxide in ambient air samples.

  17. Modelling of radiation losses for ion acceleration at ultra-high laser intensities

    NASA Astrophysics Data System (ADS)

    Capdessus, Remi; d'Humières, Emmanuel; Tikhonchuk, Vladimir

    2013-11-01

    Radiation losses of charged particles can become important in ultra high intensity laser plasma interaction. This process is described by the radiation back reaction term in the electron equation of motion. This term is implemented in the relativistic particle-in-cell code by using a renormalized Lorentz-Abraham-Dirac model. In the hole boring regime case of laser ion acceleration it is shown that radiation losses results in a decrease of the piston velocity.

  18. Laser ablation and ionisation by laser plasma radiation in the atmospheric-pressure mass spectrometry of organic compounds

    SciTech Connect

    Pento, A V; Nikiforov, S M; Simanovsky, Ya O; Grechnikov, A A; Alimpiev, S S

    2013-01-31

    A new method was developed for the mass spectrometric analysis of organic and bioorganic compounds, which involves laser ablation with the ionisation of its products by laser-plasma radiation and enables analysing gaseous, liquid, and solid substances at atmospheric pressure without sample preparation. The capabilities of this method were demonstrated by the examples of fast pharmaceutical composition screening, real-time atmosphere composition analysis, and construction of the mass spectrometric images of organic compound distributions in biological materials. (interaction of laser radiation with matter)

  19. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Laser—ultrasonic formation of melts of high-speed tool steels

    NASA Astrophysics Data System (ADS)

    Gureev, D. M.

    1994-09-01

    A study was made of the influence of ultrasonic vibrations on the processes of heat and mass transfer, and of structure formation during ultrafast crystallisation of laser melts of T1 high-speed tool steel. Acoustic flows which appeared in laser melts effectively smoothed out the temperature inhomogeneities and flattened the relief of the molten surface even when the laser radiation acted for just ~1 ms. The transformation of the mechanical energy of ultrasonic vibrations into heat increased the depth of the laser melt baths and suppressed crack formation. The observed changes in the structural and phase composition appeared as a change in the microhardness of the solidified laser melts. The geometry of coupling of ultrasound into a laser melt influenced the changes in the microhardness, suggesting a need for a more detailed analysis of the structure formation processes in the course of ultrafast crystallisation of laser melts in an ultrasonic field.

  20. Selection of linear-cavity fibre laser radiation using a reflection interferometer

    SciTech Connect

    Terentyev, V S; Simonov, V A

    2013-08-31

    We consider the use of a two-mirror multibeam reflection interferometer as a selector of linear-cavity single-mode fibre laser radiation and present experimental data on continuous wavelength tuning of an erbium-doped fibre laser. Conditions are found for single-longitudinal-mode operation of the fibre laser cavity using a reflection interferometer, with the possibility of broadband wavelength tuning. (control of laser pulse parameters)

  1. CFRP bonding pre-treatment with laser radiation of 3 μm wavelength: laser/material interaction

    NASA Astrophysics Data System (ADS)

    Blass, David; Kreling, Stefan; Nyga, Sebastian; Westphalen, Thomas; Jungbluth, Bernd; Hoffman, Hans-Dieter; Dilger, Klaus

    2016-03-01

    Laser radiation of 3 μm wavelength was generated by frequency conversion of an industrial IR laser and applied in the context of CFRP bonding pre-treatment. Reinforced and non-reinforced epoxy resins were treated with this radiation varying the relevant parameters such as laser power or treatment time. The interaction between laser radiation of 3012 nm and 1064 nm wavelength and matrix resin was analyzed mechanically (e.g. ablation depth), optically (such as fiber exposure) and chemically (e.g. contamination removal). The results gathered show that, even with the small achievable pulse fluences, a sufficient treatment of the specimens and a sensitive removing of the contaminated layers are possible.

  2. Low-output carbon dioxide laser for cutaneous wound closure of scalpel incisions: comparative tensile strength studies of the laser to the suture and staple for wound closure

    SciTech Connect

    Garden, J.M.; Robinson, J.K.; Taute, P.M.; Lautenschlager, E.P.; Leibovich, S.J.; Hartz, R.S.

    1986-01-01

    The low-output carbon dioxide (CO/sub 2/) laser was used for cutaneous wound closure of scalpel incisions. Cutaneous scalpel incisions were placed over the dorsum of three minipigs and were then closed by either the laser, sutures, or staples. At multiple time points after wound closure, up to day 90, the tensile strengths of these wounds were comparatively evaluated. All wounds, including those closed with the laser, clinically appeared to heal similarly with no evidence of wound dehiscence or infection. Tensile strength studies revealed similar sigmoid curves for all wound closure modalities with low initial tensile strengths up to days 14 to 21, which afterwards increased rapidly, with a plateau toward day 90. From our study, it appears that the CO/sub 2/ laser, in the low-output mode, can be used for cutaneous wound closure and that similar clinical healing and tensile strength measurements are obtained relative to the conventional cutaneous wound closure modalities of the suture or staple.

  3. Optical Protection Filters for Harmful Laser Beams and UV Radiation

    NASA Astrophysics Data System (ADS)

    Azim M., Osama A.

    2007-02-01

    Due to the rapid growth of radiation protection applications in various devices and instruments, it is essential to use suitable filters for eye protection of the personal working in the radiation field. Different protection filters were produced to protect from four laser beam wavelengths (at 532nm, 632.8nm, 694nm and 1064nm) and block three UV bands (UVA, UVB, and UVC). The design structure of the required dielectric multilayer filters used optical thin film technology. The computer analyses of the multilayer filter formulas were prepared using Macleod Software for the production filter processes. The deposition technique was achieved on optical substrates (Glass BK-7 and Infrasil 301) by dielectric material combinations including Dralo (mixture of oxides TiO2/Al2O3), and Lima (mixture of oxides SiO2/Al2O3); deposition by an electron beam gun. The output transmittance curves for both theoretical and experimental values of all filters are presented. To validate the suitability for use in a `real world', rather than laboratory test application, full environmental assessment was also carried out. These filters exhibited high endurance after exposing them to the durability tests (adhesion, abrasion resistance and humidity) according to military standards MIL-C-675C and MIL-C-48497A.

  4. EFFECTS OF LASER RADIATION ON MATTER: Melting and thermocapillary convection under the action of pulsed laser radiation with an inhomogeneous spatial distribution

    NASA Astrophysics Data System (ADS)

    Uglov, A. A.; Smurov, I. Yu; Gus'kov, A. G.; Aksenov, L. V.

    1990-08-01

    A theoretical study is reported of melting and thermocapillary convection under the action of laser radiation with a nonmonotonic spatial distribution of the power density. An analysis is made of changes in the geometry of the molten bath with time. The transition from a nonmonotonic boundary of a melt, corresponding to the spatial distribution of the radiation, to a monotonic one occurs in a time of the order of 1 ms when the power density of laser radiation is 105 W/cm2. The vortex structure of the flow in the molten bath is governed by the spatial distribution of the laser radiation in such a way that each local power density maximum corresponds to two vortices with oppositely directed velocity components.

  5. Mitigation of Laser Damage Growth in Fused Silica NIF Optics with a Galvanometer Scanned Carbon Dioxide Laser

    SciTech Connect

    Bass, I L; Draggoo, V; Guss, G M; Hackel, R P; Norton, M A

    2006-04-06

    Economic operation of the National Ignition Facility at the Lawrence Livermore National Laboratory depends on controlling growth of laser damage in the large, high cost optics exposed to UV light at 351 nm. Mitigation of the growth of damage sites on fused silica surfaces greater than several hundred microns in diameter has been previously reported by us using galvanometer scanning of a tightly focused 10.6 {micro}m CO{sub 2} laser spot over an area encompassing the laser damage. Further investigation revealed that fused silica vapor re-deposited on the surface as ''debris'' led to laser damage at unexpectedly low fluences when exposed to multiple laser shots at 351 nm. Additionally, laser power and spatial mode fluctuations in the mitigation laser led to poor repeatability of the process. We also found that the shape of the mitigation pit could produce downstream intensification that could damage other NIF optics. Modifications were made to both the laser system and the mitigation process in order to address these issues. Debris was completely eliminated by these changes, but repeatability and downstream intensification issues still persist.

  6. Modelling of micromachining of human tooth enamel by erbium laser radiation

    SciTech Connect

    Belikov, A V; Skrypnik, A V; Shatilova, K V

    2014-08-31

    We consider a 3D cellular model of human tooth enamel and a photomechanical cellular model of enamel ablation by erbium laser radiation, taking into account the structural peculiarities of enamel, energy distribution in the laser beam cross section and attenuation of laser energy in biological tissue. The surface area of the texture in enamel is calculated after its micromachining by erbium laser radiation. The influence of the surface area on the bond strength of enamel with dental filling materials is discussed. A good correlation between the computer simulation of the total work of adhesion and experimentally measured bond strength between the dental filling material and the tooth enamel after its micromachining by means of YAG : Er laser radiation is attained. (laser biophotonics)

  7. Plasma formation on a metal surface under combined action of laser and microwave radiation

    SciTech Connect

    Gavrilyuk, A P; Shaparev, N Ya

    2013-10-31

    By means of numerical modelling of the combined effect of laser (1.06 mm) and microwave (10{sup 10} – 10{sup 13} s{sup -1}) radiation on the aluminium surface in vacuum it is shown that the additional action of microwave radiation with the frequency 10{sup 12} s{sup -1} provides complete ionisation of the metal vapour (for the values of laser radiation duration and intensity used in the calculations), while in the absence of microwave radiation the vapour remains weakly ionised. The mathematical model used accounts for the processes, occurring in the condensed phase (heat conduction, melting), the evaporation and the kinetic processes in the resulting vapour. (interaction of laser radiation with matter. laser plasma)

  8. Nd:YAG laser systems with radiation delivery by thin hollow waveguides

    NASA Astrophysics Data System (ADS)

    Nemec, Michal; Jelínková, Helena; Šulc, Jan; Miyagi, Mitsunobu; Iwai, Katsumasa; Shi, Yi-Wei; Matsuura, Yuji

    2008-04-01

    The goal of the work was the investigation of hollow waveguide utilization for near infrared laser radiation delivery. As basic delivery unit, a new thin cyclic olefin polymer coated silver hollow glass waveguide with diameters 100/190 μm or 250/360 μm and length up to 20 cm was used. Four near infrared laser sources were based on the Nd:YAG crystals. The first one - Nd:YAG laser passively Q-switched by LiF:F 2- saturable absorber - was coherently pumped by Alexandrite radiation. The system generated 1.06 μm wavelength radiation with 6 ns length of pulse and 0.7 mJ maximum output energy. The second and third laser systems were compact longitudinally diode pumped Nd:YAG lasers generating radiation at wavelength 1.06 μm and 1.44 μm. These lasers were operating in a free-running regime under pulsed pumping (pulse repetition rate 50 Hz). Mean output power 160 mW (90 mW) with pulse length 0.5 ms (1 ms) was generated at wavelength 1.06 μm (1.44 μm). The last radiation source was the Nd:YAG/V:YAG microchip laser pumped by laser diode and generating the radiation at 1.34 μm wavelength. The output power, pulse length, and repetition rate were 25 mW, 6 ns, and 250 Hz, respectively. All lasers were generating beam with gaussian TEM 00 profile. These radiations were focused into thin a waveguide and delivery radiation characteristics were investigated. It was recognized that the output spatial structure is significantly modified in all cases. However a compact delivery system can be useful for near infrared powerful radiation delivery in some special technological and medical applications.

  9. Influence of asymmetric injection of laser radiation into capillary waveguides on wake acceleration of electrons possessing various injection energies

    NASA Astrophysics Data System (ADS)

    Veisman, M. E.; Kuznetsov, S. V.; Andreev, N. E.

    2016-04-01

    Laser wakefield acceleration of electron bunches possessing various initial injection energies in capillary waveguides is studied in the conditions of an asymmetric input of laser radiation into a waveguide (the propagation direction of laser radiation deviates from the capillary axis or the laser spot is not symmetric). The factors determining the critical angle of the laser radiation input into the capillary, within which the wake acceleration of electrons is close to optimal, have been found. It is shown that in acceleration stages where electron energies are high, the requirements to angular concentricity of the capillary axis and laser radiation focusing are substantially weaker due to the relativistic 'weighting' of the electron mass.

  10. Efficient sintering of nanocrystalline titanium dioxide films for dye solar cells via raster scanning laser

    NASA Astrophysics Data System (ADS)

    Mincuzzi, Girolamo; Vesce, Luigi; Reale, Andrea; Di Carlo, Aldo; Brown, Thomas M.

    2009-09-01

    By identifying the right combination of laser parameters, in particular the integrated laser fluence Φ, we fabricated dye solar cells (DSCs) with UV laser-sintered TiO2 films exhibiting a power conversion efficiency η =5.2%, the highest reported for laser-sintered devices. η is dramatically affected by Φ and a clear trend is reported. Significantly, DSCs fabricated by raster scanning the laser beam to sinter the TiO2 films are made as efficient as those with oven-sintered ones. These results, confirmed on three batches of cells, demonstrate the remarkable potential (noncontact, local, low cost, rapid, selective, and scalable) of scanning laser processing applied to DSC technology.

  11. Cross modulation method of transformation of the spatial coherence of pulsed laser radiation in a nonlinear medium

    SciTech Connect

    Kitsak, M A; Kitsak, A I

    2008-04-30

    The cross modulation method of transformation of the spatial coherence of low-power pulsed laser radiation in a nonlinear medium is proposed. The method is realised experimentally in a multimode optical fibre. The estimates of the degree of spatial coherence of radiation subjected to the phase cross modulation demonstrated the high efficiency of this radiation decorrelation mechanism. (control of laser radiation parameters)

  12. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Physics of the plasma corona in the problem of laser controlled thermonuclear fusion

    NASA Astrophysics Data System (ADS)

    Andreev, N. E.; Gorbunov, Leonid M.; Tikhonchuk, Vladimir T.

    1994-09-01

    A brief analysis is made of the most important nonlinear processes which result from the interaction of laser radiation with thermonuclear targets. lt is shown that problems in the physics of the plasma corona should be an essential part of any programme of research on laser controlled thermonuclear fusion. A list is given of the problems that have to be solved first before going to the next level of laser energies.

  13. Generation of terahertz radiation in the reflection of a laser pulse from a dense plasma

    SciTech Connect

    Frolov, A. A.

    2007-12-15

    The generation of low-frequency (terahertz) electromagnetic radiation in the reflection of a laser pulse from the boundary of a dense plasma is considered. Low-frequency wave electromagnetic fields in vacuum are excited by a vortex electric current that is induced at the plasma boundary by the ponderomotive force of the laser pulse. The spectral, angular, and energy parameters of the low-frequency radiation, as well as the spatiotemporal structure of the emitted waves, are investigated. It is shown that for typical parameters of present-day laser plasma experiments, the power of terahertz radiation can amount to tens of megawatts.

  14. Evaluation of carbon dioxide laser irradiation associated with calcium hydroxide in the treatment of dentinal hypersensitivity. A preliminary study.

    PubMed

    Romano, Ana Cristina Cury Camargo; Aranha, Ana Cecilia Corrêa; da Silveira, Bruno Lopes; Baldochi, Sônia Lícia; Eduardo, Carlos de Paula

    2011-01-01

    Attempts have been made to treat dentinal hypersensitivity by sealing exposed dentinal tubules, and the carbon dioxide (CO(2)) laser has been shown to have a sealing effect on dentinal surfaces. The purpose of this study was to analyze the morphological ultra-structure and temperature change after CO(2) laser irradiation of dentin. Fourteen human third molars were selected and cleaned. An area was delimited, and the samples were randomly divided into seven groups: Group 1 (G1): control; G2, calcium hydroxide paste (CA) + CO(2) laser (L) (0.5 W/63,69 W/cm(2)); G3, CA + L (1 W/125,38 W/cm(2)); G4, CA + L (1.5 W/191,08 W/cm(2)); G5, L (0.5 W); G6, L (1 W); G7, L (1.5 W). All irradiation was performed in unfocused mode. The electron micrographs were analyzed by three observers. For temperature analysis, a thermocouple was used. Data were subjected to statistical analysis. The Kruskal-Wallis non-parametric test showed statistical differences between the groups (P < 0.05). For the two by two comparisons, all groups treated with calcium hydroxide paste presented significantly higher mean scores. In the groups treated by CO(2) laser only, fusion, re-crystallization, cracks and carbonization were observed. A change of 1 ± 5°C was noted in the temperature. Under the limitation of an in vitro study, and with the protocols used, we concluded that CO(2) laser is safe to use for the establishment of partial fusion and re-solidification of the dentinal surface. PMID:20127133

  15. Spectral characteristics of VUV radiation emitted by a laser plume

    SciTech Connect

    Khater, Mohamed A.

    2013-12-16

    We study some experimental parameters and conditions of laser-generated plasma plumes using time-integrated, spatially resolved emission spectroscopy in the VUV range. The influences of the laser focusing lens type, laser wavelength, as well as laser pulse energy on the emission characteristics of the laser plasmas are investigated. The aim of the work is to improve the detection capability of the laser-induced plasma spectroscopy (LIPS) technique. The results obtained demonstrate a set of optimum conditions for maximum spectral line intensities and signal-to-background ratios of laser-produced plasmas in the VUV regime.

  16. Use of Zernike polynomials and interferometry in the optical design and assembly of large carbon-dioxide laser systems

    SciTech Connect

    Viswanathan, V.K.

    1981-01-01

    This paper describes the need for non-raytracing schemes in the optical design and analysis of large carbon-dioxide lasers like the Gigawatt, Gemini, and Helios lasers currently operational at Los Alamos, and the Antares laser fusion system under construction. The scheme currently used at Los Alamos involves characterizing the various optical components with a Zernike polynomial set obtained by the digitization of experimentally produced interferograms of the components. A Fast Fourier Transform code then propagates the complex amplitude and phase of the beam through the whole system and computes the optical parameters of interest. The analysis scheme is illustrated through examples of the Gigawatt, Gemini, and Helios systems. A possible way of using the Zernike polynomials in optical design problems of this type is discussed. Comparisons between the computed values and experimentally obtained results are made and it is concluded that this appears to be a valid approach. As this is a review article, some previously published results are also used where relevant.

  17. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA Annealing of induced absorption in quartz glasses by ArF laser radiation

    NASA Astrophysics Data System (ADS)

    Sergeev, P. B.; Sergeev, A. P.

    2010-11-01

    Annealing of individual bands of electron-beam-induced absorption (IA) in the region of 150 — 400 nm in KS-4V, KU-1, and Corning 7980 (ArF Grade) quartz glasses by ArF laser radiation is studied. It is shown that the phototransformation of the IA spectra occurs mainly due to a significant decrease in the amplitudes of bands at λ = 183.5, 213, and 260 nm. The role played by interstitial oxygen, hydrogen, and chlorine in the formation and relaxation of glass defects is considered.

  18. Transendoscopic and freehand use of flexible hollow fibers for carbon dioxide laser surgery in the upper airway of the horse: a preliminary report

    NASA Astrophysics Data System (ADS)

    Palmer, Scott E.

    1991-05-01

    Hollow plastic fibers lined with metal and dielectric films that transmit carbon dioxide laser energy were evaluated for clinical use in upper airway surgery of the horse. These flexible waveguides were used both freehand and through the biopsy channel of an endoscope to incise, coagulate and vaporize tissues in the pharynx and larynx of 4 horses.

  19. Radiation from laser accelerated electron bunches: Coherent terahertz and femtosecond X-rays

    SciTech Connect

    Leemans, W.P.; Esarey, E.; van Tilborg, J.; Michel, P.A.; Schroeder, C.B.; Toth, Cs.; Geddes, C.G.R.; Shadwick, B.A.

    2004-10-01

    Electron beam based radiation sources provide electromagnetic radiation for countless applications. The properties of the radiation are primarily determined by the properties of the electron beam. Compact laser driven accelerators are being developed that can provide ultra-short electron bunches (femtosecond duration) with relativistic energies reaching towards a GeV. The electron bunches are produced when an intense laser interacts with a dense plasma and excites a large amplitude plasma density modulation (wakefield) that can trap background electrons and accelerate them to high energies. The short pulse nature of the accelerated bunches and high particle energy offer the possibility of generating radiation from one compact source that ranges from coherent terahertz to gamma rays. The intrinsic synchronization to a laser pulse and unique character of the radiation offers a wide range of possibilities for scientific applications. Two particular radiation source regimes are discussed: Coherent terahertz emission and x-ray emission based on betatron oscillations and Thomson scattering.

  20. Fires of endotracheal tubes of three different materials during carbon dioxide laser surgery.

    PubMed

    Lai, Hui-Chin; Juang, Sin-Ei; Liu, Tsun-Jui; Ho, Wai-Ming

    2002-03-01

    The hazards of fire during CO2 laser surgery of the airway necessitate the use of special endotracheal tubes. We reviewed 227 cases receiving CO2 laser laryngeal surgery over the past 7 years, of whom 3 suffered the complications as a result of endotracheal fire. Tracheal tubes made of different materials were used among them, including silicone T-tube (Montgomery Safe-T-tube), jet ventilation tube and Xomed laser shield endotracheal tube. In addition, we tested in vitro the combustibility of endotracheal tubes of six different materials which included silicone T-tube, jet ventilation tube, Xomed laser shield endotracheal tube, stainless Laser-Flex tracheal tube, polyvinyl chloride (PVC) endotracheal tube and aluminum foil wrapped PVC endotracheal tube by exposing them to continuous operating CO2 laser in room air. The time to initiation of fire and burn through the lumen was 0.3 second for T-tube, 0.5 s for jet ventilation tube, 5 s for Xomed laser shield endotracheal tube, and 0.8 s for PVC endotracheal tube, respectively. The Laser-Flex tracheal tube (stainless) and aluminum foil wrapped PVC endotracheal tube did not catch fire after 30 s of CO2 laser irradiation. The silicone T-tube seemed to be the most dangerous. Jet ventilation tube and Xomed laser shield endotracheal tube have the risk of fire. Aluminum foil wrapped PVC endotracheal tube was reported to catch fire before. Therefore we are of the opinion that the stainless endotracheal tube is the safest tube during CO2 laser surgery. PMID:11989049

  1. Process of defect formation and diffusion in metals induced by laser radiation

    NASA Astrophysics Data System (ADS)

    Zvonkov, Alexander D.; Boranbaeva, H. M.

    1990-10-01

    There have been conducted researches for the presence of defects in specimens of repined carbonyl iron after the treatment by continuous radiation of C02-laser under subcritical conditions. High degree of presence of the defects is characterized by appearance of cellular dislocation structure and by considerable oversaturation of vacancies. There have been also investigated the conditions of realization of an accelerated diffusion of boron in iron and steels in treating by continuous radiation of CD2-- laser. It was revealed that the boron redistribution from the previously created layer of borides on the metal surface is accomplished in steels to the depthes of up to 3 mm. The accelerated oxygen diffusion stimulated by the laser radiation has been investigated on the basis of the obtained results of the process of internal oxidation of alloy Cu-Sn (0. 55 at 7. ). There has been proposed the model of process of accelerated transport. 2. FORMATION OF DEFECTS IN CARBONYL IRON UNDER CONTINUOUS LASER RADIATION The investigation of the defect formation under the continuous laser radiation 10. 6 sam) was conducted with the specimens (4x0. 8x80) mm of carbonyl iron 0. 008 C 0. 047 Mn Al + Si + S) refined in hydrogen atmosphere. The laser treatment was accomplished without flashing the metal surface. Treatment characteristics: radiation power P (0. 25-1. 1 kV. Specimen displacement speed under the laser beam V (10-2. 5) mm/s

  2. SU-E-T-484: A New Method of Aligning Patient Setup Lasers in Radiation Therapy

    SciTech Connect

    Hwang, U; Lim, Y; Cho, K; Jeong, C; Kim, M; Jeong, J; Park, J; Shin, D; Lee, S; Kim, J; Choi, S; Kwak, J; Yoon, K; Park, S; Kim, S

    2014-06-01

    Purpose: To develop a new method to align the patient setup lasers in radiation therapy and examine its validity and effectiveness. Methods: The new laser alignment method was realized by a device composed of both a metallic base plate and few acrylic transparent plates with a cross hair line on each of them. The holders of radiochromic films were prepared in the device to find a radiation isocenter. The right laser positions could be found optically by matching the shadows of all the cross hairs in the gantry head and the device. The repeatability and reproducibility (R and R) of laser alignments and the dependency of the alignment on the position error of the light source were evaluated by comparing the standard deviations and the means of the measured laser positions. After aligning the lasers optically, a radiation isocenter was found by a collimator spoke shot and the gantry spoke shot, and then the lasers were parallely translated to the isocenter. Results: In the R and R test, the standard deviation was 1.14 mm for the new method whereas it was 1.49 mm or 2.76 mm for the conventional method with either high- or low-precision levels. In the test of the dependency on the position error of the light source, the mean laser position was shifted by 5.3 mm corresponding to the shift of the light source, 4.8 mm for the new method, but for the conventional method the laser position was shifted more than 7 times than that. The positional shift could be corrected by a parallel translation to the isocenter in the new method. Conclusion: A new laser alignment method was devised for radiation therapy and tested successfully. The method enabled us to align the lasers easily and accurately without repetition, and all lasers could be finally aligned to the radiation isocenter.

  3. Carbon dioxide laser vaporization of facial siliconomas: flash in the pan or way of the future?

    PubMed

    Chui, Christopher Hoe Kong; Fong, Poh Him

    2008-03-01

    In 1988, Becker first described the "laser silicone flash" encountered while using the CO2 laser to remove breast siliconosis, but no subsequent use of the CO2 laser to remove siliconomas has been reported since. To our knowledge, lasers have not been described to treat facial silicone granulomas. Three cases of facial silicone granuloma (cheek, upper eyelids, and chin) were treated using the technique of CO2 laser vaporization.We describe a novel and effective method to remove facial siliconomas. This technique could avoid the need for radical resection of functional facial tissues such as nerves. Tiny globules of injected silicone in the face were vaporized without any untoward effects. Whether larger siliconomas can be treated in the same way remains to be seen and is an area of potential study.

  4. EFFECTS OF LASER RADIATION ON MATTER: Efficient surface-erosion plasma formation in air due to the action of pulse-periodic laser radiation

    NASA Astrophysics Data System (ADS)

    Min'ko, L. Ya; Chumakou, A. N.; Bosak, N. A.

    1990-11-01

    A study was made of the interaction of a series of periodic laser (λ = 1.06 μm) pulses with a number of materials (aluminum, copper, graphite, ebonite) in air at laser radiation power densities q = 107-109 W/cm2 and repetition frequencies f<=50 kHz. The radiation was concentrated in spots of ~ 10 - 2 cm2 area. Efficient formation of plasma as a result of laser erosion (q > 2 × 108 W/cm2, f>=5 kHz) was observed. A screening layer of an air plasma created by the first pulse of the series was expelled from the interaction zone and this was followed by erosion plasma formation under conditions of slight screening of the target during the action of the subsequent laser pulses.

  5. Photoblepharokeratoconjunctivitis caused by invisible infrared radiation emitted from a green laser pointer.

    PubMed

    Khedr, Yahya A H; Khedr, Abdulla H

    2014-01-01

    There are a wide variety of laser pointers sold to the general public. Among those are the high-powered diode-pumped solid-state lasers (>5 mW), which do not follow the laser safety regulations for packing, and are sold as regular lasers without the infrared (IR) filters. In this case report, we encountered a patient with photoblepharokeratoconjunctivitis caused by the invisible IR radiations emitted from a green laser pointer. Owing to the thermal effect of the invisible IR rays led to the disease. PMID:24618868

  6. The detection of carbon dioxide leaks using quasi-tomographic laser absorption spectroscopy measurements in variable wind

    DOE PAGES

    Levine, Zachary H.; Pintar, Adam L.; Dobler, Jeremy T.; Blume, Nathan; Braun, Michael; Zaccheo, T. Scott; Pernini, Timothy G.

    2016-04-13

    Laser absorption spectroscopy (LAS) has been used over the last several decades for the measurement of trace gasses in the atmosphere. For over a decade, LAS measurements from multiple sources and tens of retroreflectors have been combined with sparse-sample tomography methods to estimate the 2-D distribution of trace gas concentrations and underlying fluxes from point-like sources. In this work, we consider the ability of such a system to detect and estimate the position and rate of a single point leak which may arise as a failure mode for carbon dioxide storage. The leak is assumed to be at a constant ratemore » giving rise to a plume with a concentration and distribution that depend on the wind velocity. We demonstrate the ability of our approach to detect a leak using numerical simulation and also present a preliminary measurement.« less

  7. The detection of carbon dioxide leaks using quasi-tomographic laser absorption spectroscopy measurements in variable wind

    PubMed Central

    Levine, Zachary H.; Pintar, Adam L.; Dobler, Jeremy T.; Blume, Nathan; Braun, Michael; Scott Zaccheo, T.; Pernini, Timothy G.

    2016-01-01

    Laser absorption spectroscopy (LAS) has been used over the last several decades for the measurement of trace gasses in the atmosphere. For over a decade, LAS measurements from multiple sources and tens of retroreflectors have been combined with sparse-sample tomography methods to estimate the 2-D distribution of trace gas concentrations and underlying fluxes from point-like sources. In this work, we consider the ability of such a system to detect and estimate the position and rate of a single point leak which may arise as a failure mode for carbon dioxide storage. The leak is assumed to be at a constant rate giving rise to a plume with a concentration and distribution that depend on the wind velocity. We demonstrate the ability of our approach to detect a leak using numerical simulation and also present a preliminary measurement. PMID:27453761

  8. The detection of carbon dioxide leaks using quasi-tomographic laser absorption spectroscopy measurements in variable wind

    NASA Astrophysics Data System (ADS)

    Levine, Z. H.; Pintar, A. L.; Dobler, J.; Blume, N.; Braun, M.; Zaccheo, T. S.; Pernini, T. G.

    2015-11-01

    Laser Absorption Spectroscopy (LAS) has been used over the last several decades for the measurement of trace gasses in the atmosphere. For over a decade, LAS measurements from multiple sources and tens of retroreflectors have been combined with sparse-sample tomography methods to estimate the 2-D distribution of trace gas concentrations and underlying fluxes from pointlike sources. In this work, we consider the ability of such a system to detect and estimate the position and rate of a single point leak which may arise as a failure mode for carbon dioxide storage. The leak is assumed to be at a constant rate giving rise to a plume with a concentration and distribution that depend on the wind velocity. We demonstrate the ability of our approach to detect a leak using numerical simulation and a preliminary measurement.

  9. The detection of carbon dioxide leaks using quasi-tomographic laser absorption spectroscopy measurements in variable wind

    NASA Astrophysics Data System (ADS)

    Levine, Zachary H.; Pintar, Adam L.; Dobler, Jeremy T.; Blume, Nathan; Braun, Michael; Zaccheo, T. Scott; Pernini, Timothy G.

    2016-04-01

    Laser absorption spectroscopy (LAS) has been used over the last several decades for the measurement of trace gasses in the atmosphere. For over a decade, LAS measurements from multiple sources and tens of retroreflectors have been combined with sparse-sample tomography methods to estimate the 2-D distribution of trace gas concentrations and underlying fluxes from point-like sources. In this work, we consider the ability of such a system to detect and estimate the position and rate of a single point leak which may arise as a failure mode for carbon dioxide storage. The leak is assumed to be at a constant rate giving rise to a plume with a concentration and distribution that depend on the wind velocity. We demonstrate the ability of our approach to detect a leak using numerical simulation and also present a preliminary measurement.

  10. Modification of biological objects in water media by CO{sub 2}-laser radiation

    SciTech Connect

    Baranov, G A; Belyaev, A A; Onikienko, S B; Smirnov, S A; Khukharev, V V

    2005-09-30

    The modification of biological objects (polysaccharides and cells) by CO{sub 2}-laser radiation in water added drop by drop into the interaction region is studied theoretically and experimentally. Calculations are performed by using the models describing gas-dynamic and heterogeneous processes caused by absorption of laser radiation by water drops. It is found experimentally that the laser modification of polysaccharides leads to the formation of low-molecular derivatives with immunostimulating properties. A dose of the product of laser activation of the yeast culture Saccharamyces cerevisiae prevented the development of a toxic emphysema in mice and protected them against lethal grippe and also prevented a decrease of survival rate, increased the average life, and prevented the development of metabolic and immune disorders in mice exposed to sublethal gamma-radiation doses. (laser applications and other topics in quantum electronics)

  11. Calculating the radiation characteristics of accelerated electrons in laser-plasma interactions

    NASA Astrophysics Data System (ADS)

    Li, X. F.; Yu, Q.; Gu, Y. J.; Qu, J. F.; Ma, Y. Y.; Kong, Q.; Kawata, S.

    2016-03-01

    In this paper, we studied the characteristics of radiation emitted by electrons accelerated in a laser-plasma interaction by using the Lienard-Wiechert field. In the interaction of a laser pulse with a underdense plasma, electrons are accelerated by two mechanisms: direct laser acceleration (DLA) and laser wakefield acceleration (LWFA). At the beginning of the process, the DLA electrons emit most of the radiation, and the DLA electrons emit a much higher peak photon energy than the LWFA electrons. As the laser-plasma interaction progresses, the LWFA electrons become the major radiation emitter; however, even at this stage, the contribution from DLA electrons is significant, especially to the peak photon energy.

  12. Radiation pressure acceleration of protons to 93 MeV with circularly polarized petawatt laser pulses

    NASA Astrophysics Data System (ADS)

    Kim, I. Jong; Pae, Ki Hong; Choi, Il Woo; Lee, Chang-Lyoul; Kim, Hyung Taek; Singhal, Himanshu; Sung, Jae Hee; Lee, Seong Ku; Lee, Hwang Woon; Nickles, Peter V.; Jeong, Tae Moon; Kim, Chul Min; Nam, Chang Hee

    2016-07-01

    The radiation pressure acceleration (RPA) of charged particles has been a challenging task in laser-driven proton/ion acceleration due to its stringent requirements in laser and target conditions. The realization of radiation-pressure-driven proton acceleration requires irradiating ultrathin targets with an ultrahigh contrast and ultraintense laser pulses. We report the generation of 93-MeV proton beams achieved by applying 800-nm 30-fs circularly polarized laser pulses with an intensity of 6.1 × 10 20 W / cm 2 to 15-nm-thick polymer targets. The radiation pressure acceleration was confirmed from the obtained optimal target thickness, quadratic energy scaling, polarization dependence, and three-dimensional particle-in-cell simulations. We expect this clear demonstration of RPA to facilitate the realization of laser-driven proton/ion sources delivering energetic and short-pulse particle beams for novel applications.

  13. Second-harmonic generation efficiency for multifrequency ytterbium-doped fibre laser radiation

    SciTech Connect

    Politko, M O; Kablukov, S I; Nemov, I N; Babin, Sergei A

    2013-02-28

    The second-harmonic generation (SHG) efficiency for cw Yb-doped fibre laser radiation, which is characterised by many longitudinal modes with random phases, is compared with the SHG efficiency for amplified single-frequency Nd : YAG laser radiation in ppLN and KTP crystals, characterised by the type-I and type-IIphase matching, respectively. It is shown that the conversion efficiency into the second harmonic in the multifrequency regime for both crystals is higher by a factor of about 1.6, a value close to the calculated enhancement (2 for the Gaussian mode statistics). This difference is explained by possible deviation of the statistics of the Yb-doped fibre laser radiation from Gaussian, which is confirmed by measurements of the laser temporal dynamics. (laser optics 2012)

  14. The effects of pulse duration on ablation pressure driven by laser radiation

    SciTech Connect

    Zhou, Lei; Li, Xiao-Ya Zhu, Wen-Jun; Wang, Jia-Xiang; Tang, Chang-Jian

    2015-03-28

    The effects of laser pulse duration on the ablation pressure induced by laser radiation are investigated using Al target. Numerical simulation results using one dimensional radiation hydro code for laser intensities from 5×10{sup 12}W/cm{sup 2} to 5×10{sup 13}W/cm{sup 2} and pulse durations from 0.5 ns to 20 ns are presented. These results suggest that the laser intensity scaling law of ablation pressure differs for different pulse durations. And the theoretical analysis shows that the effects of laser pulse duration on ablation pressure are mainly caused by two regimes: the unsteady-state flow and the radiative energy loss to vacuum.

  15. Selected problems of interaction of laser radiation with tissues

    NASA Astrophysics Data System (ADS)

    Zajac, Andrzej

    2000-11-01

    In these paper the selected physical processes of interaction of laser beams with biological tissues are presented. From the wide area of medical applications of laser systems three very interesting problems are presented: medical application of pulsed lasers sources (from some hundred of microseconds to femtoseconds of laser pulse duration), the physical processes accompanied with an interaction of laser beams in spectral range 2000-3000nm, and the selected methods of optical diagnostics of a human tissues parameters. The fundamental scientific, technical, and construction problems of novel laser systems for medical applications are presented. These problems are illustrated by the results of the clinical and laboratory experiments.

  16. Carbon dioxide laser turbinectomy versus submucosal diathermy of hypertrophied turbinates. Histopathological prospective study

    NASA Astrophysics Data System (ADS)

    Mohamed Bofares, Khalid

    2010-05-01

    Aim: To assess suspected turbinate mucosal distractive changes of CO2 laser partial turbinectomy as compared to submucosal diathermy technique of hypertrophied inferior turbinates and thus risk of appearance of mucosal atrophic changes. Introduction: CO2 laser turbinotomy or turbinectomy has become an established well documented line of treatment of hypertrophied inferior turbinates not responding to medical treatment. Although there have been several reports discussing the clinical aspects of laser turbinectomy, but exact pathological changes that take place following laser application to the turbinate have not been described completely and clearly. For this reason this study was conducted to confirm these possible histopathological changes and compared with those following submucosal diathermy technique. Patients and methods: Twenty patients with chronic hypertrophied inferior turbinates and presenting mainly with nasal obstruction, ten out of them were subjected to CO2 laser turbinectomy while other half underwent to submucosal diathermy technique. Tiny biopsies were taken immediately after surgery (within one week after surgery ), as well as 4-6 weeks later and processed for further histopathological evaluation. Results: By 100%, the all patients of two groups showed areas of epithelial loss were observed immediately after both techniques. 4-6 weeks after laser application 60% of patients showed normal epithelial areas as compared to second group where 20% of patients who showed normal epithelial picture. Conclusion: CO2 laser turbinectomy can be considered as more preservative technique for nasal mucosa as well as the function of the nose as compared to submucosal diathermy technique.

  17. Measurement of nitrogen dioxide in cigarette smoke using quantum cascade tunable infrared laser differential absorption spectroscopy (TILDAS)

    NASA Astrophysics Data System (ADS)

    Shorter, Joanne H.; Nelson, David D.; Zahniser, Mark S.; Parrish, Milton E.; Crawford, Danielle R.; Gee, Diane L.

    2006-04-01

    Although nitrogen dioxide (NO 2) has been previously reported to be present in cigarette smoke, the concentration estimates were derived from kinetic calculations or from measurements of aged smoke, where NO 2 was formed some time after the puff was taken. The objective of this work was to use tunable infrared laser differential absorption spectroscopy (TILDAS) equipped with a quantum cascade (QC) laser to determine if NO 2 could be detected and quantified in a fresh puff of cigarette smoke. A temporal resolution of ˜0.16 s allowed measurements to be taken directly as the NO 2 was formed during the puff. Sidestream cigarette smoke was sampled to determine if NO 2 could be detected using TILDAS. Experiments were conducted using 2R4F Kentucky Reference cigarettes with and without a Cambridge filter pad. NO 2 was detected only in the lighting puff of whole mainstream smoke (without a Cambridge filter pad), with no NO 2 detected in the subsequent puffs. The measurement precision was ˜1.0 ppbV Hz -1/2, which allows a detection limit of ˜0.2 ng in a 35 ml puff volume. More NO 2 was generated in the lighting puff using a match or blue flame lighter (29 ± 21 ng) than when using an electric lighter (9 ± 3 ng). In the presence of a Cambridge filter pad, NO 2 was observed in the gas phase mainstream smoke for every puff (total of 200 ± 30 ng/cigarette) and is most likely due to smoke chemistry taking place on the Cambridge filter pad during the smoke collection process. Nitrogen dioxide was observed continuously in the sidestream smoke starting with the lighting puff.

  18. Measurement of nitrogen dioxide in cigarette smoke using quantum cascade tunable infrared laser differential absorption spectroscopy (TILDAS).

    PubMed

    Shorter, Joanne H; Nelson, David D; Zahniser, Mark S; Parrish, Milton E; Crawford, Danielle R; Gee, Diane L

    2006-04-01

    Although nitrogen dioxide (NO(2)) has been previously reported to be present in cigarette smoke, the concentration estimates were derived from kinetic calculations or from measurements of aged smoke, where NO(2) was formed some time after the puff was taken. The objective of this work was to use tunable infrared laser differential absorption spectroscopy (TILDAS) equipped with a quantum cascade (QC) laser to determine if NO(2) could be detected and quantified in a fresh puff of cigarette smoke. A temporal resolution of approximately 0.16s allowed measurements to be taken directly as the NO(2) was formed during the puff. Sidestream cigarette smoke was sampled to determine if NO(2) could be detected using TILDAS. Experiments were conducted using 2R4F Kentucky Reference cigarettes with and without a Cambridge filter pad. NO(2) was detected only in the lighting puff of whole mainstream smoke (without a Cambridge filter pad), with no NO(2) detected in the subsequent puffs. The measurement precision was approximately 1.0 ppbVHz(-1/2), which allows a detection limit of approximately 0.2 ng in a 35 ml puff volume. More NO(2) was generated in the lighting puff using a match or blue flame lighter (29+/-21 ng) than when using an electric lighter (9+/-3 ng). In the presence of a Cambridge filter pad, NO(2) was observed in the gas phase mainstream smoke for every puff (total of 200+/-30 ng/cigarette) and is most likely due to smoke chemistry taking place on the Cambridge filter pad during the smoke collection process. Nitrogen dioxide was observed continuously in the sidestream smoke starting with the lighting puff.

  19. A novel method of carbon dioxide clumped isotope analysis with tunable infra-red laser direct absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Prokhorov, Ivan; Kluge, Tobias; Janssen, Christof

    2016-04-01

    Precise clumped isotopes analysis of carbon dioxide opens up new horizons of atmospheric and biogeochemical research. Recent advances in laser and spectroscopic techniques provides us necessary instrumentation to access extremely low sub-permill variations of multiply-substituted isotopologues. We present an advanced analysis method of carbon dioxide clumped isotopes using direct absorption spectroscopy. Our assessments predict the ultimate precision of the new method on the sub-permill level comparable to state of the art mass spectrometry. Among the most auspicious intrinsic properties of this method we highlight genuine Δ16O13C18O and Δ16O13C18O measurements without isobaric interference, measurement cycle duration of several minutes versus hours for mass spectrometric analysis, reduced sample size of ˜ 10 μmol and high flexibility, allowing us to perform in-situ measurements. The pilot version of the instrument is being developed in an international collaboration framework between Heidelberg University, Germany and Pierre and Marie Curie University, Paris, France. It employs two continuous interband quantum cascade lasers tuned at 4.439 μm and 4.329 μm to measure doubly ( 16O13C18O, 16O13C17O) and singly ( 16O12C16O, 16O13C16O, 16O12C17O, 16O12C18O) substituted isotopologues, respectively. Two identical Herriot cells are filled with dry pure CO2 sample and reference gas at working pressure of 1 ‑ 10 mbar. Cells provide optical path lengths of ˜ 17 m for the laser tuned at doubly substituted isotopologues lines and use a single pass for the laser tuned at the stronger lines of singly substituted isotopologues. Light outside of the gas cells is coupled into optical fiber to avoid absorption by ambient air CO2. Simulations predict sub-permill precision at working pressure of 1 mbar and room temperature stabilised at the ±10 mK level. Our prime target is to apply the proposed method for continuous in-situ analysis of CO2. We are foreseeing potential

  20. A novel method of carbon dioxide clumped isotope analysis with tunable infra-red laser direct absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Prokhorov, Ivan; Kluge, Tobias; Janssen, Christof

    2016-04-01

    Precise clumped isotopes analysis of carbon dioxide opens up new horizons of atmospheric and biogeochemical research. Recent advances in laser and spectroscopic techniques provides us necessary instrumentation to access extremely low sub-permill variations of multiply-substituted isotopologues. We present an advanced analysis method of carbon dioxide clumped isotopes using direct absorption spectroscopy. Our assessments predict the ultimate precision of the new method on the sub-permill level comparable to state of the art mass spectrometry. Among the most auspicious intrinsic properties of this method we highlight genuine Δ16O13C18O and Δ16O13C18O measurements without isobaric interference, measurement cycle duration of several minutes versus hours for mass spectrometric analysis, reduced sample size of ˜ 10 μmol and high flexibility, allowing us to perform in-situ measurements. The pilot version of the instrument is being developed in an international collaboration framework between Heidelberg University, Germany and Pierre and Marie Curie University, Paris, France. It employs two continuous interband quantum cascade lasers tuned at 4.439 μm and 4.329 μm to measure doubly ( 16O13C18O, 16O13C17O) and singly ( 16O12C16O, 16O13C16O, 16O12C17O, 16O12C18O) substituted isotopologues, respectively. Two identical Herriot cells are filled with dry pure CO2 sample and reference gas at working pressure of 1 - 10 mbar. Cells provide optical path lengths of ˜ 17 m for the laser tuned at doubly substituted isotopologues lines and use a single pass for the laser tuned at the stronger lines of singly substituted isotopologues. Light outside of the gas cells is coupled into optical fiber to avoid absorption by ambient air CO2. Simulations predict sub-permill precision at working pressure of 1 mbar and room temperature stabilised at the ±10 mK level. Our prime target is to apply the proposed method for continuous in-situ analysis of CO2. We are foreseeing potential

  1. Carbon dioxide laser ablation with immediate autografting in a full-thickness porcine burn model.

    PubMed Central

    Glatter, R D; Goldberg, J S; Schomacker, K T; Compton, C C; Flotte, T J; Bua, D P; Greaves, K W; Nishioka, N S; Sheridan, R L

    1998-01-01

    OBJECTIVE: To compare the long-term clinical and histologic outcome of immediate autografting of full-thickness burn wounds ablated with a high-power continuous-wave CO2 laser to sharply débrided wounds in a porcine model. SUMMARY BACKGROUND DATA: Continuous-wave CO2 lasers have performed poorly as tools for burn excision because the large amount of thermal damage to viable subeschar tissues precluded successful autografting. However, a new technique, in which a high-power laser is rapidly scanned over the eschar, results in eschar vaporization without significant damage to underlying viable tissues, allowing successful immediate autografting. METHODS: Full-thickness paravertebral burn wounds measuring 36 cm2 were created on 11 farm swine. Wounds were ablated to adipose tissue 48 hours later using either a surgical blade or a 150-Watt continuous-wave CO2 laser deflected by an x-y galvanometric scanner that translated the beam over the tissue surface, removing 200 microm of tissue per scan. Both sites were immediately autografted and serially evaluated clinically and histologically for 180 days. RESULTS: The laser-treated sites were nearly bloodless. The mean residual thermal damage was 0.18+/-0.05 mm. The mean graft take was 96+/-11% in manual sites and 93+/-8% in laser sites. On postoperative day 7, the thickness of granulation tissue at the graft-wound bed interface was greater in laser-debrided sites. By postoperative day 180, the manual and laser sites were histologically identical. Vancouver scar assessment revealed no differences in scarring at postoperative day 180. CONCLUSIONS: Long-term scarring, based on Vancouver scar assessments and histologic evaluation, was equivalent at 6 months in laser-ablated and sharply excised sites. Should this technology become practical, the potential clinical implications include a reduction in surgical blood loss without sacrifice of immediate engraftment rates or long-term outcome. Images Figure 1. Figure 2. Figure 3

  2. Bicircular-laser-field-assisted electron-ion radiative recombination

    NASA Astrophysics Data System (ADS)

    Odžak, S.; Milošević, D. B.

    2015-11-01

    Electron-ion radiative recombination assisted by a bicircular laser field that consists of two circularly polarized fields counterrotating in the x y plane and having the frequencies r ω and s ω , which are integer multiples of the fundamental frequency ω , is considered using the S -matrix theory. The energy and polarization of soft x rays generated in this process are analyzed as functions of the incident electron energy and incident electron angle with respect to the x axis. Numerical results for the process of direct recombination of electrons with He+ ionic targets are presented. Abrupt cutoffs of the plateau structures in the emitted x-ray energy spectra are explained by classical analysis. Simpler or more complex oscillatory structures in the spectrum may appear as a result of the interference of a different number of classical orbits. Symmetry analysis and the numerical results show that the x-ray power spectrum and ellipticity are invariant with respect to a rotation of the incident electron momentum by the angle 2 π /(r +s ) . We have visualized this by presenting the logarithm of the differential power spectrum and polarization of the emitted x rays in false colors as functions of the incident electron angle and the x-ray energy. We have also shown that the change of the relative phase of the bicircular field is equivalent to the change of the incident electron angle. By controlling this relative phase it is possible to control the polarization of the emitted soft x rays.

  3. Radiative polarization of electrons in a strong laser wave

    NASA Astrophysics Data System (ADS)

    Karlovets, Dmitry V.

    2011-12-01

    We reanalyze the problem of radiative polarization of electrons brought into collision with a circularly polarized strong plane wave. We present an independent analytical verification of formulas for the cross section given by Ivanov [Eur. Phys. J. CEPCFFB1434-604410.1140/epjc/s2004-01861-x 36, 127 (2004)]. By choosing the exact electron's helicity as the spin quantum number we show that the self-polarization effect exists only for the moderately relativistic electrons with energy γ=E/mc2≲10 and only for a non-head-on collision geometry. In these conditions polarization degree may achieve values up to 65%, but the effective polarization time is found to be larger than 1 s even for a high-power optical or infrared laser with intensity parameter ξ=|E|mc2/Ecℏω˜0.1 (Ec=m2c3/eℏ). This makes such a polarization practically unrealizable. We also compare these results with the ones of some papers where the high degree of polarization was predicted for ultrarelativistic case. We argue that this apparent contradiction arises due to the different choice of the spin quantum numbers. In particular, the quantum numbers that provide the high degree of polarization represent neither helicity nor transverse polarization, which makes the use of them inconvenient in practice.

  4. Radiative polarization of electrons in a strong laser wave

    SciTech Connect

    Karlovets, Dmitry V.

    2011-12-15

    We reanalyze the problem of radiative polarization of electrons brought into collision with a circularly polarized strong plane wave. We present an independent analytical verification of formulas for the cross section given by Ivanov et al.[Eur. Phys. J. C 36, 127 (2004)]. By choosing the exact electron's helicity as the spin quantum number we show that the self-polarization effect exists only for the moderately relativistic electrons with energy {gamma}=E/mc{sup 2} < or approx. 10 and only for a non-head-on collision geometry. In these conditions polarization degree may achieve values up to 65%, but the effective polarization time is found to be larger than 1 s even for a high-power optical or infrared laser with intensity parameter {xi}=|E|mc{sup 2}/E{sub c}({Dirac_h}/2{pi}){omega}{approx}0.1 (E{sub c}=m{sup 2}c{sup 3}/e({Dirac_h}/2{pi})). This makes such a polarization practically unrealizable. We also compare these results with the ones of some papers where the high degree of polarization was predicted for ultrarelativistic case. We argue that this apparent contradiction arises due to the different choice of the spin quantum numbers. In particular, the quantum numbers that provide the high degree of polarization represent neither helicity nor transverse polarization, which makes the use of them inconvenient in practice.

  5. A new endotracheal tube for carbon dioxide and KTP laser surgery of the aerodigestive tract.

    PubMed

    Ossoff, R H; Aly, A; Gonzales, D; Koriwchak, M J; Houchin, N

    1993-01-01

    We have tested the fire-resistance of a new endotracheal tube designed for use in laser surgery of the upper aerodigestive tract. This Teflon/metallic-wrapped silicone tube seems capable of withstanding occasional, accidental pulsed laser impact at power settings used clinically (1 to 10 watts) without fire. On rare occasions when continuous mode is used, the tube seems capable of withstanding at least several seconds of continuous irradiation at clinical power settings without igniting. When used with other recommended safety procedures, this tube should minimize the risk of endotracheal tube fire from accidental laser impact. PMID:8437882

  6. [Effects of laser radiation on the periodontium. An animal model approach. Effects of usual radiation dosage].

    PubMed

    Noguerol Rodriguez, B; Alandez Chamorro, J; Cañizares Garcia, J; Campos Muñoz, A; Sicilia Felechosa, A

    1989-05-01

    Twenty four albino mice of forty days old were selected. Twelve forty days old albino mice were irradiated with a Helium-Neon laser source, dose of 10.50566 Jul/cm2. They were divided in two groups according to time of animal sacrifice (immediately after irradiation and ten days after). As control were used twelve mice using the same time as the experimental groups, but without radiation. T.E.M. ultrathin sections showed alteration only in the conjunctiva and in the bone tissues, but not in the epithelial tissue. The bone showed two osteocyte population according to their response to irradiation. The first population showed characteristic comparable with the controls, and the second showed alterations suggestive of a degenerative process. The connective tissue also showed two fibroblasts populations, the first showed signs of a big synthesizing activity, and the second, degenerative signs. The first fibroblast population appeared in the animals sacrificed immediately after irradiation. PMID:2637054

  7. [Effects of laser radiation on the periodontium. An animal model approach. Effects of usual radiation dosage].

    PubMed

    Noguerol Rodriguez, B; Alandez Chamorro, J; Cañizares Garcia, J; Campos Muñoz, A; Sicilia Felechosa, A

    1989-05-01

    Twenty four albino mice of forty days old were selected. Twelve forty days old albino mice were irradiated with a Helium-Neon laser source, dose of 10.50566 Jul/cm2. They were divided in two groups according to time of animal sacrifice (immediately after irradiation and ten days after). As control were used twelve mice using the same time as the experimental groups, but without radiation. T.E.M. ultrathin sections showed alteration only in the conjunctiva and in the bone tissues, but not in the epithelial tissue. The bone showed two osteocyte population according to their response to irradiation. The first population showed characteristic comparable with the controls, and the second showed alterations suggestive of a degenerative process. The connective tissue also showed two fibroblasts populations, the first showed signs of a big synthesizing activity, and the second, degenerative signs. The first fibroblast population appeared in the animals sacrificed immediately after irradiation.

  8. Ex vivo investigations of laser auricular cartilage reshaping with carbon dioxide spray cooling in a rabbit model

    PubMed Central

    Wu, Edward C.; Sun, Victor; Manuel, Cyrus T.; Protsenko, Dmitriy E.; Jia, Wangcun; Nelson, J. Stuart; Wong, Brian J. F.

    2014-01-01

    Laser cartilage reshaping (LCR) with cryogen spray cooling is a promising modality for producing cartilage shape change while reducing cutaneous thermal injury. However, LCR in thicker tissues, such as auricular cartilage, requires higher laser power, thus increasing cooling requirements. To eliminate the risks of freeze injury characteristic of high cryogen spray pulse rates, a carbon dioxide (CO2) spray, which evaporates rapidly from the skin, has been proposed as the cooling medium. This study aims to identify parameter sets which produce clinically significant reshaping while producing minimal skin thermal injury in LCR with CO2 spray cooling in ex vivo rabbit auricular cartilage. Excised whole rabbit ears were mechanically deformed around a cylindrical jig and irradiated with a 1.45-μm wavelength diode laser (fluence 12–14 J/cm2 per pulse, four to six pulse cycles per irradiation site, five to six irradiation sites per row for four rows on each sample) with concomitant application of CO2 spray (pulse duration 33–85 ms) to the skin surface. Bend angle measurements were performed before and after irradiation, and the change quantified. Surface temperature distributions were measured during irradiation/cooling. Maximum skin surface temperature ranged between 49.0 to 97.6 °C following four heating/cooling cycles. Significant reshaping was achieved with all laser dosimetry values with a 50–70 °C difference noted between controls (no cooling) and irradiated ears. Increasing cooling pulse duration yielded progressively improved gross skin protection during irradiation. CO2 spray cooling may potentially serve as an alternative to traditional cryogen spray cooling in LCR and may be the preferred cooling medium for thicker tissues. Future studies evaluating preclinical efficacy in an in vivo rabbit model are in progress. PMID:23307439

  9. Effect of smoke evacuation on limiting thermal damage when using the carbon dioxide laser for cutaneous surgery

    NASA Astrophysics Data System (ADS)

    Waters, Ruth A.; Thomas, J. M.; Clement, Marc; Davies, S.

    1990-06-01

    We have conducted a study of the use of the carbon dioxide (C02) laser for ablation of multiple cutaneous recurrences of melanoma. Lesions of primary malignant melanoma are usually widely excised to try and prevent local recurrence. Despite this, recurrent cutaneous lesions do occur. These lesions may be small and numerous making local excision impractical. Hyperthermic isolated limb perfusion has shown some success in controlling the local disease but this procedure has a significant morbidty, some patients show only a limited response and post-perfusion recurrences are common.1 Also, in some patients, thelesions will not be confined to a limb. No other method of local control has provided an ideal solution and amputation has sometimes been a last resort. We have therefore selected patients for laser ablation if they have had lesions too numerous for local excision, or have had recurrences following perfusion or were otherwise suitable for perfusion. The lesions were vaporized under local or general anaesthesia according to their size and number. The wounds were then left to heal by secondary intention. Simple dry dressings were applied and all patients were discharged home within 24 hours. In total we have treated over 1,500 lesions in 30 patients. The results of the initial study have been very encouraging. The procedure is quick and simple with absent or minimal post-operative pain. Although the incidence of recurrent tumour at a previously lasered site is less than 1%, new tumours may develop at other sites. These are amenable to further laser treatment.

  10. Light-induced scattering in laser radiation nonlinear optical limiting based on fullerene-containing media

    NASA Astrophysics Data System (ADS)

    Belousova, Inna M.; Grigor'ev, Vladimir A.; Danilov, Oleg B.; Kalintsev, Alexander G.; Kris'ko, A. V.; Mironova, N. G.; Yur'ev, Michail S.

    2001-03-01

    The contribution of light induced scattering to nonlinear optical limiting is theoretically and experimentally investigated. It is shown that light induced scattering is caused by fine-scale (1 divided by 10 micrometer) inhomogeneities formation, very low (comparable to spontaneous noise) laser beam inhomogeneities can evolve into light induced scattering. The numerical modeling of scattered radiation angular distribution and laser radiation attenuation in optical limiters was performed. The modeling results were compared with the experimental ones.

  11. Comparative study of coherent multi-color radiation generation in a seeded free-electron laser

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Xiang, Dao; Zhao, Zhentang

    2016-04-01

    We present the comparative study on three representative methods for producing the coherent multi-color radiation in a seeded free electron laser based on the high gain harmonic generation (HGHG). In these schemes, either the electron beam density or the seed laser intensity is modulated to produce a coherent radiation pulse train that yields multiple spectral lines in FEL output. Realistic beam parameters obtained in 3D start-to-end simulations are used to compare the performance of each scheme.

  12. Helium-tight Laser Beam Welding of Aluminum with Brillant Laser Beam Radiation

    NASA Astrophysics Data System (ADS)

    Heinen, Paul; Wu, Hao; Olowinsky, Alexander; Gillner, Arnold

    The substitution of steel as base metal for casings and packaging applications has increased during the last years. Especially aluminum with advantages in weight and machining effort has become a versatile solution for applications in fine mechanics (e.g. sensor housings) and automotive applications. Joining of aluminum components is more critical due to possible crack formation in the joining seam and uneven seam geometry. With the high intensity of brillant laser beam sources the specific challenges of aluminum welding can be overcome. Due to its hydrogen affinity and high degree of reflection for laser radiation at a wavelength of 1 μm (95%) aluminum needs to be welded with proper shielding gas support and high beam quality in order to avoid seam defects. Cracks and pores can lead to non-sufficient tightness for sensor applications and early failure. Housing components have been joined to form a functioning unit in order to seal electrical or measuring components, which are helium-tight for these applications.

  13. Development of Extreme Ultraviolet Radiation Source using Laser Triggered Vacuum Spark Discharge Plasma

    SciTech Connect

    Watanabe, Masato; Yamada, Junzaburo; Zhu Qiushi; Hotta, Eiki

    2009-01-21

    A laser triggerd discharge produced Sn plasma light source has been developed. Experimental parameters such as electrode separation and laser irradiation power are varied to optimize EUV emission power. It is clear that the maximum EUV radiation was occurred in the position where the pinch was observed.

  14. Compton backscattering of intracavity storage ring free-electron laser radiation

    SciTech Connect

    Dattoli, G.; Giannessi, L.; Torre, A.

    1995-12-31

    We discuss the{gamma}-ray production by Compton backscattering of intracavity storage ring Free-Electron Laser radiation. We use a semi-analytical model which provides the build up of the signal combined with the storage ring damping mechanism and derive simple relations yielding the connection between backscattered. Photons brightness and the intercavity laser equilibrium intensity.

  15. Recent Progress in Development of a Laser Based, Ultra-High Precision Isotope Monitor for Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Nelson, D. D.; McManus, J. B.; Herndon, S. C.; Zahniser, M. S.

    2015-12-01

    Greenhouse gas (GHG) emissions are the primary drivers of global climate change and hence there is a crucial need to quantify their sources and sinks. A general technique to help constrain source and sink strengths in GHG exchange processes is the analysis of the relative proportions of isotopic variants of GHG's. Very high precision measurements of isotopologue ratios are necessary in order to identify sources and sinks because the characteristic changes are small. The standard method of isotopologue measurement has been mass spectrometry, but this technique typically requires significant sample preparation and relatively high instrument maintenance. Laser spectroscopy has the potential to ease these burdens and also to allow easy separation and analysis of interfering isobars such as 13C-CO2 and 17O-CO2. We present recent results demonstrating ultra-high precision measurements of carbon dioxide isotope ratios which rival the accuracy of mass spectrometric measurements. These measurements were performed using Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS). We have developed a method for analyzing air samples from canisters by alternately and rapidly trapping sample gas and working reference gas in the optical cell. Using this technique, we have obtained isotopic measurement precisions of ~7 per meg for both 13C-CO2 and 18O-CO2 while measuring trapped ambient air samples with volumes as small as 200 ml with a 16 minute measurement duration. The figure shows a histogram of 2 minute measurements. Our current measurement precision for 17O-CO2 is 30 per meg, but we expect to reduce this to 10 per meg by working in a better spectral region. Our ultimate goal is to create an automated, ultra-high accuracy carbon dioxide isotope monitor able to quantify 13C-, 18O-, and 17O-CO2at the 10 per meg level using small (~100 standard ml), discreet air samples. We will also discuss recent progress in the measurement of the clumped isotopes of carbon dioxide in

  16. 1579 NM Fiber Laser Source for Spaceborne Monitoring of Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Cézard, Nicolas; Lombard, Laurent; Le Gouët, Julien; Goular, Didier; Bresson, Alexandre; Dolfi-Bouteyre, Agnès; Canat, Guillaume

    2016-06-01

    We report on the development of a 1579 nm pulsed fiber laser source with high peak-power, intended to be used as a lidar source for CO2 monitoring from space. We first discuss water-vapor sensitivity of spaceborne CO2 measurements by lidar and point the interest of the 1579 nm wavelength with that respect. Then we detail the current development status of the pulsed fiber laser source.

  17. Nanostructuring of single-crystal silicon carbide by picosecond UV laser radiation

    SciTech Connect

    Barmina, E V; Serkov, A A; Shafeev, G A

    2013-12-31

    Surface nanostructures are produced on single-crystal 4H-SiC by laser ablation in water using a Nd : YAG laser (355-nm wavelength, 10-ps pulse duration) as a radiation source. The morphology of the nanostructured surface and the nanostructure size distribution are examined in relation to the energy density of the incident laser beam. The potential of the described process for improving the luminosity of light-emitting diodes on silicon carbide substrates is discussed. (letters)

  18. On the Observation of Jitter Radiation in Solid-Density Laser-Plasma Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    Keenan, Brett; Medvedev, Mikhail

    2015-11-01

    Plasmas created by high-intensity lasers are often subject to the formation of kinetic-streaming instabilities, such as the Weibel instability, which lead to the spontaneous generation of high-amplitude, tangled magnetic fields. These fields typically exist on small spatial scales, i.e., ``sub-Larmor scales''. Radiation from charged particles moving through small-scale electromagnetic (EM) turbulence, known as jitter radiation, has spectral characteristics distinct from both synchrotron and cyclotron radiation, and it carries valuable information on the statistical properties of the EM field structure and evolution. Consequently, jitter radiation from laser-produced plasmas may offer insight into the underlying electromagnetic turbulence. Here we investigate the prospects for, and demonstrate the feasibility of, such direct radiative diagnostics for mildly relativistic, solid-density laser plasmas produced in lab experiments. Supported by grant DOE grant DE-FG02-07ER54940 and NSF grant AST-1209665.

  19. Cooling of relativistic electron beams in intense laser pulses: Chirps and radiation

    NASA Astrophysics Data System (ADS)

    Yoffe, S. R.; Noble, A.; Macleod, A. J.; Jaroszynski, D. A.

    2016-09-01

    Next-generation high-power laser facilities (such as the Extreme Light Infrastructure) will provide unprecedented field intensities, and will allow us to probe qualitatively new physical regimes for the first time. One of the important fundamental questions which will be addressed is particle dynamics when radiation reaction and quantum effects play a significant role. Classical theories of radiation reaction predict beam cooling in the interaction of a relativistic electron bunch and a high-intensity laser pulse, with final-state properties only dependent on the laser fluence. The observed quantum suppression of this cooling instead exhibits a dependence on the laser intensity directly. This offers the potential for final-state properties to be modified or even controlled by tailoring the intensity profile of the laser pulse. In addition to beam properties, quantum effects will be manifest in the emitted radiation spectra, which could be manipulated for use as radiation sources. We compare predictions made by classical, quasi-classical and stochastic theories of radiation reaction, and investigate the influence of chirped laser pulses on the observed radiation spectra.

  20. On a semiconductor laser with a p–n tunnel junction with radiation emission through the substrate

    SciTech Connect

    Kolpakov, D. A. Zvonkov, B. N.; Nekorkin, S. M.; Dikareva, N. V.; Aleshkin, V. Ya.; Dubinov, A. A.

    2015-11-15

    A multiwell interband cascade laser with a tunnel junction within a single waveguide and radiation emission through the substrate is implemented for the first time. It is shown that such a laser heterostructure design provides the more efficient population of quantum wells in comparison with a conventional multiwell laser with radiation emission through the substrate, due to which the lasing threshold is significantly lowered.

  1. EFFECTS OF LASER RADIATION ON MATTER: Simulation of photon acceleration upon irradiation of a mylar target by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Andreev, Stepan N.; Rukhadze, Anri A.; Tarakanov, V. P.; Yakutov, B. P.

    2010-01-01

    Acceleration of protons is simulated by the particle-in-cell (PIC) method upon irradiation of mylar targets of different thicknesses by femtosecond plane-polarised pulsed laser radiation and at different angles of radiation incidence on the target. The comparison of the results of calculations with the experimental data obtained in recent experiments shows their good agreement. The optimal angle of incidence (458) at which the proton energy achieves its absolute maximum is obtained.

  2. Electrical Switching of Terahertz Radiation on Vanadium Dioxide Thin Film Fabricated with Nano Antennas

    NASA Astrophysics Data System (ADS)

    Jeong, Y. G.; Bernien, H.; Kyoung, J. S.; Kim, H. S.; Park, H. R.; Kim, B. J.; Kim, T.; Kim, D. S.

    2011-12-01

    Electrical switching of terahertz radiation through nano antennas on VO2 thin film is demonstrated and is compared with bare VO2. Rectangular apertures act as slot antennas which attract terahertz radiation when VO2 is in semi-conducting state. These antennas are turned-off when VO2 becomes metallic by bias, giving an enhanced control of transmission.

  3. Poly(1,4-phenyleneazine N,N-dioxide): A recyclable material for a solventless laser-imageable resist process

    SciTech Connect

    Baum, T.H.; Larson, C.E.; Hacker, N.P.

    1994-11-01

    Upon heating under vacuum, poly(1,4-phenyleneazine-N,N-dioxide) depolymerizes to give 1,4-dinitrosobenzene which can be condensed onto a suitable substrate. The nature of the condensate is dependent on the substrate temperature. At temperatures below -110{degrees}C the condensate can be monomeric, at about -50{degrees}C it is a mixture of dimer and oligomers, and at -20{degrees}C it is polymeric. Thick and thin films of the polymer can be rapidly prepared by volatilization of 1,4-dinitrosobenzene from the bulk polymer onto a substrate and allowing the collected condensate to warm to room temperature. The resultant films appear to be stable indefinitely at room temperature and atmospheric pressure yet can be selectively removed from the substrate using a focused visible laser beam. After a suitable image-transfer process, the polymer is removed by heating to 100{degrees}C. The laser imaging, deposition, and final removal of polymer are all nondestructive, thermal processes. Thus if a suitable vacuum chamber equipped with a cooling trap is used for this process, the polymer is 100% recyclable. 14 refs., 6 figs.

  4. Promising Option for Treatment of Striae Alba: Fractionated Microneedle Radiofrequency in Combination with Fractional Carbon Dioxide Laser

    PubMed Central

    Fatemi Naeini, Farahnaz; Behfar, Shadi; Abtahi-Naeini, Bahareh; Keyvan, Shima; Pourazizi, Mohsen

    2016-01-01

    Background. A consistent treatment has not been proposed for treatment of Striae Alba (SA). The present study was designed to compare the fractionated microneedle radiofrequency (FMR) alone and in combination with fractional carbon dioxide laser (FMR + CO2) in the treatment of SA. Methods. Forty-eight pairs of SA from six patients were selected. Right or left SAs were randomly assigned to one of the treatment groups. The surface area of the SA before and after treatment and clinical improvement using a four-point scale were measured at the baseline, after one and three months. Results. The mean age of the patients was 30.17 ± 5.19 years. The mean difference of the surface area between pre- and posttreatment in the FMR + CO2 group was significantly higher than that in the FMR group (p = 0.003). Clinical improvement scales showed significantly higher improvement in the FMR + CO2 group than in the FMR group in the first and second follow-up (p = 0.002 and 0.004, resp.). There were no major persistence side-effects in both groups. Conclusions. The results showed that FMR + CO2 laser was more effective than FMR alone in the treatment of SA. PMID:27069471

  5. A laser-induced fluorescence instrument for aircraft measurements of sulfur dioxide in the upper troposphere and lower stratosphere

    NASA Astrophysics Data System (ADS)

    Rollins, Andrew W.; Thornberry, Troy D.; Ciciora, Steven J.; McLaughlin, Richard J.; Watts, Laurel A.; Hanisco, Thomas F.; Baumann, Esther; Giorgetta, Fabrizio R.; Bui, Thaopaul V.; Fahey, David W.; Gao, Ru-Shan

    2016-09-01

    This work describes the development and testing of a new instrument for in situ measurements of sulfur dioxide (SO2) on airborne platforms in the upper troposphere and lower stratosphere (UT-LS). The instrument is based on the laser-induced fluorescence technique and uses the fifth harmonic of a tunable fiber-amplified semiconductor diode laser system at 1084.5 nm to excite SO2 at 216.9 nm. Sensitivity and background checks are achieved in flight by additions of SO2 calibration gas and zero air, respectively. Aircraft demonstration was performed during the NASA Volcano-Plume Investigation Readiness and Gas-Phase and Aerosol Sulfur (VIRGAS) experiment, which was a series of flights using the NASA WB-57F during October 2015 based at Ellington Field and Harlingen, Texas. During these flights, the instrument successfully measured SO2 in the UT-LS at background (non-volcanic) conditions with a precision of 2 ppt at 10 s and an overall uncertainty determined primarily by instrument drifts of ±(16 % + 0.9 ppt).

  6. Dentin ablation-rate measurements in endodontics witj HF and CO2 laser radiation

    NASA Astrophysics Data System (ADS)

    Makropoulou, Mersini I.; Serafetinides, Alexander A.; Khabbaz, Marouan; Sykaras, Sotirios; Tsikrikas, G. N.

    1996-01-01

    Recent studies focused on the ability of the laser light to enlarge the root canal during the endodontic therapy. The aim of this research is the experimental and theoretical study of the ablation rate of two infrared laser wavelengths on dentin. Thirty freshly extracted human teeth were longitudinally sectioned at thicknesses ranged from 0.5 to 2 mm, and irradiated on the root canal dentin. The measured ablation rates in dentinal wall of the root canal showed that the HF laser at 2.9 micrometer can more effectively penetrate into the tissue, whereas the carbon dioxide laser at 10.6 micrometer leads to high thermal damage of the ablation crater surroundings.

  7. Laser-plasma-accelerators—A novel, versatile tool for space radiation studies

    NASA Astrophysics Data System (ADS)

    Hidding, Bernhard; Königstein, Thomas; Willi, Oswald; Rosenzweig, James B.; Nakajima, Kazuhisa; Pretzler, Georg

    2011-04-01

    The potential of laser-plasma-based accelerator technology for future advanced space radiation studies is investigated. Laser-plasma accelerators have been shown to be capable of robust generation of particle beams such as electrons, protons, neutrons and ions, as well as photons, having a wide range of accessible parameters. Further, instead of maximum accelerating fields of the order of MV/m as in state-of-the-art accelerators, laser-plasma acceleration operates with fields up to TV/m and can thus be used to reach as yet inaccessible parameter regimes, but which are very relevant to space radiation studies. Due to their versatility and compactness, the same laser-plasma-accelerator can be used in university-scale labs to generate different kinds of particle and photon beams, each yielding up to kGy doses per shot, and allowing combinations of different kinds of radiation production simultaneously. Laser-plasma-accelerators provide the advantage of cost-effective radiation generation, thus ameliorating the current shortage of beam time for testing of radiation resistivity of electronic components. Beyond this, laser-plasma-accelerators can be used to reproduce certain aspects of space radiation, e.g. broad, decreasing multi-MeV-scale spectra, with substantially improved level of fidelity, as compared to state-of-the-art technology. This can increase the significance of electronic components testing, and in turn yield increased reliability and safety of future manned or unmanned space missions, high-altitude flights, as well as the electronic components used in harsh radiation environments in general. Laser-plasma-accelerators may therefore become indispensable tools for next-generation space radiation studies.

  8. Study of the effect of properties of material on vacuum breakdown initiated by laser radiation

    SciTech Connect

    Seleznev, V. P.; Revazov, V. O.

    2015-12-15

    In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse.

  9. Strong field-induced frequency conversion of laser radiation in plasma plumes: recent achievements.

    PubMed

    Ganeev, R A

    2013-01-01

    New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications.

  10. Annealing of induced absorption in quartz glasses by ArF laser radiation

    SciTech Connect

    Sergeev, P B; Sergeev, A P

    2010-11-13

    Annealing of individual bands of electron-beam-induced absorption (IA) in the region of 150 - 400 nm in KS-4V, KU-1, and Corning 7980 (ArF Grade) quartz glasses by ArF laser radiation is studied. It is shown that the phototransformation of the IA spectra occurs mainly due to a significant decrease in the amplitudes of bands at {lambda} = 183.5, 213, and 260 nm. The role played by interstitial oxygen, hydrogen, and chlorine in the formation and relaxation of glass defects is considered. (effects of laser radiation on matter. laser plasma)

  11. Shapes of laser radiation pulses modified by nonlinear scattering in aqueous suspension of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Mikheeva, G. M.; Mogileva, T. N.; Okotrub, A. V.; Vanyukov, V. V.

    2010-03-01

    An improved scheme of z-scanning was used to study the parameters of nanosecond 1064-nm laser radiation pulses scattered at right angle under the conditions of optical limiting in an aqueous suspension of purified carbon nanotubes (CNTs). CNTs were synthesized by the electric-arc evaporation of graphite. It is established that the amplitude, shape, duration, and temporal position of the peak of scattered light pulses significantly depend on the laser radiation power density. The results agree with the mechanism of thermoinduced nonlinear scattering that is operative during the optical limiting of laser pulses in CNT suspensions.

  12. Biophysical aspects of effects of laser radiation on living systems: II. Effect on Pseudomonas aeruginosa bacteria

    NASA Astrophysics Data System (ADS)

    Ulianova, O. V.; Ulyanov, S. S.; Zhihong, Zhang; Sibo, Zhou; Luo, Qingming

    2009-12-01

    It is shown that, taking into account tendencies in the development of new laser technologies, the study of the effect of laser light on microorganisms is a topical and important ecological problem. The results of studies of the role played by the spatiotemporal coherence of laser radiation from the viewpoint of the action of the radiation on bacterial cells are presented. It is found that the coherence of light does not cause any changes in microorganisms under natural conditions (in the presence of photosensitizers in natural concentrations). Based on computer modeling and experimental studies, it is shown that the dynamics of speckles does not affect the stability of bacterial cells.

  13. Dependence of injection locking of a TEA CO2 laser on intensity of injected radiation

    NASA Technical Reports Server (NTRS)

    Oppenheim, U. P.; Menzies, R. T.; Kavaya, M. J.

    1982-01-01

    The results of an experimental study to determine the minimum required injected power to control the output frequency of a TEA CO2 laser are reported. A CW CO2 waveguide laser was used as the injection oscillator. Both the power and the frequency of the injected radiation were varied, while the TEA resonator cavity length was adjusted to match the frequency of the injected signal. Single-longitudinal mode (SLM) TEA laser radiation was produced for injected power levels which are several orders of magnitude below those previously reported. The ratio of SLM output power to injection power exceeded 10 to the 12th at the lowest levels of injected intensity.

  14. On the possibility of controlling laser ablation by tightly focused femtosecond radiation

    SciTech Connect

    Alferov, S V; Karpeev, S V; Khonina, S N; Tukmakov, K N; Moiseev, O Yu; Shulyapov, S A; Ivanov, K A; Savel'ev-Trofimov, A B

    2014-11-30

    We report the results of studies on the possibilities of controlling laser ablation by changing the polarisation state and the intensity distribution in the focal plane of the beams of high-power femtosecond radiation by means of beam diaphragming and controllable phase modulation using binary-phase plates. The latter provides the adjustment of correlation between the electric field components in the focus area. Based on the results of numerical modelling of the distribution of the electric field components in the focus area, an explanation of the mechanism of formation of the unusually shaped craters is given. (interaction of laser radiation with matter. laser plasma)

  15. Strong Field-Induced Frequency Conversion of Laser Radiation in Plasma Plumes: Recent Achievements

    PubMed Central

    Ganeev, R. A.

    2013-01-01

    New findings in plasma harmonics studies using strong laser fields are reviewed. We discuss recent achievements in the growth of the efficiency of coherent extreme ultraviolet (XUV) radiation sources based on frequency conversion of the ultrashort pulses in the laser-produced plasmas, which allowed for the spectral and structural studies of matter through the high-order harmonic generation (HHG) spectroscopy. These studies showed that plasma HHG can open new opportunities in many unexpected areas of laser-matter interaction. Besides being considered as an alternative method for generation of coherent XUV radiation, it can be used as a powerful tool for various spectroscopic and analytical applications. PMID:23864818

  16. Low-level red laser therapy alters effects of ultraviolet C radiation on Escherichia coli cells

    PubMed Central

    Canuto, K.S.; Sergio, L.P.S.; Guimarães, O.R.; Geller, M.; Paoli, F.; Fonseca, A.S.

    2015-01-01

    Low-level lasers are used at low power densities and doses according to clinical protocols supplied with laser devices or based on professional practice. Although use of these lasers is increasing in many countries, the molecular mechanisms involved in effects of low-level lasers, mainly on DNA, are controversial. In this study, we evaluated the effects of low-level red lasers on survival, filamentation, and morphology of Escherichia colicells that were exposed to ultraviolet C (UVC) radiation. Exponential and stationary wild-type and uvrA-deficientE. coli cells were exposed to a low-level red laser and in sequence to UVC radiation. Bacterial survival was evaluated to determine the laser protection factor (ratio between the number of viable cells after exposure to the red laser and UVC and the number of viable cells after exposure to UVC). Bacterial filaments were counted to obtain the percentage of filamentation. Area-perimeter ratios were calculated for evaluation of cellular morphology. Experiments were carried out in duplicate and the results are reported as the means of three independent assays. Pre-exposure to a red laser protected wild-type and uvrA-deficient E. coli cells against the lethal effect of UVC radiation, and increased the percentage of filamentation and the area-perimeter ratio, depending on UVC fluence and physiological conditions in the cells. Therapeutic, low-level red laser radiation can induce DNA lesions at a sub-lethal level. Consequences to cells and tissues should be considered when clinical protocols based on this laser are carried out. PMID:26445338

  17. Low-level red laser therapy alters effects of ultraviolet C radiation on Escherichia coli cells.

    PubMed

    Canuto, K S; Sergio, L P S; Guimarães, O R; Geller, M; Paoli, F; Fonseca, A S

    2015-10-01

    Low-level lasers are used at low power densities and doses according to clinical protocols supplied with laser devices or based on professional practice. Although use of these lasers is increasing in many countries, the molecular mechanisms involved in effects of low-level lasers, mainly on DNA, are controversial. In this study, we evaluated the effects of low-level red lasers on survival, filamentation, and morphology of Escherichia colicells that were exposed to ultraviolet C (UVC) radiation. Exponential and stationary wild-type and uvrA-deficientE. coli cells were exposed to a low-level red laser and in sequence to UVC radiation. Bacterial survival was evaluated to determine the laser protection factor (ratio between the number of viable cells after exposure to the red laser and UVC and the number of viable cells after exposure to UVC). Bacterial filaments were counted to obtain the percentage of filamentation. Area-perimeter ratios were calculated for evaluation of cellular morphology. Experiments were carried out in duplicate and the results are reported as the means of three independent assays. Pre-exposure to a red laser protected wild-type and uvrA-deficient E. coli cells against the lethal effect of UVC radiation, and increased the percentage of filamentation and the area-perimeter ratio, depending on UVC fluence and physiological conditions in the cells. Therapeutic, low-level red laser radiation can induce DNA lesions at a sub-lethal level. Consequences to cells and tissues should be considered when clinical protocols based on this laser are carried out.

  18. Contamination and Radiation Effects on Nonlinear Crystals for Space Laser Systems

    NASA Technical Reports Server (NTRS)

    Abdeldayem, Hossain A.; Dowdye, Edward; Jamison, Tracee; Canham, John; Jaeger, Todd

    2005-01-01

    Space Lasers are vital tools for NASA s space missions and military applications. Although, lasers are highly reliable on the ground, several past space laser missions proved to be short-lived and unreliable. In this communication, we are shedding more light on the contamination and radiation issues, which are the most common causes for optical damages and laser failures in space. At first, we will present results based on the study of liquids and subsequently correlate these results to the particulates of the laser system environment. We present a model explaining how the laser beam traps contaminants against the optical surfaces and cause optical damages and the role of gravity in the process. We also report the results of the second harmonic generation efficiency for nonlinear optical crystals irradiated with high-energy beams of protons. In addition, we are proposing to employ the technique of adsorption to minimize the presence of adsorbing molecules present in the laser compartment.

  19. Applications of Light Amplification by Stimulated Emission of Radiation (Lasers) for Restorative Dentistry.

    PubMed

    Najeeb, Shariq; Khurshid, Zohaib; Zafar, Muhammad Sohail; Ajlal, Syed

    2016-01-01

    Light amplification by stimulated emission of radiation (laser) has been used widely in a range of biomedical and dental applications in recent years. In the field of restorative dentistry, various kinds of lasers have been developed for diagnostic (e.g. caries detection) and operative applications (e.g. tooth ablation, cavity preparation, restorations, bleaching). The main benefits for laser applications are patient comfort, pain relief and better results for specific applications. Major concerns for using dental lasers frequently are high cost, need for specialized training and sensitivity of the technique, thereby compromising its usefulness particularly in developing countries. The main aim of this paper is to evaluate and summarize the applications of lasers in restorative dentistry, including a comparison of the applications of lasers for major restorative dental procedures and conventional clinical approaches. A remarkable increase in the use of lasers for dental application is expected in the near future. PMID:26642047

  20. Generation of terahertz radiation by focusing femtosecond bichromatic laser pulses in a gas or plasma

    SciTech Connect

    Chizhov, P A; Volkov, Roman V; Bukin, V V; Ushakov, A A; Garnov, Sergei V; Savel'ev-Trofimov, Andrei B

    2013-04-30

    The generation of terahertz radiation by focusing two-frequency femtosecond laser pulses is studied. Focusing is carried out both in an undisturbed gas and in a pre-formed plasma. The energy of the terahertz radiation pulses is shown to reduce significantly in the case of focusing in a plasma. (extreme light fields and their applications)

  1. Low-intensity infrared laser radiation influence on the tumor growth

    NASA Astrophysics Data System (ADS)

    Cheida, A. A.; Efimova, E. G.

    2005-08-01

    Infrared laser radiation of low intensity in exposition dose of 25-35 mJicm2 does not cause progress the tumor process. Moreover, disturbing the blood flow in the tumor due to changing synthesis of norepinephrine and histamine this radiation contributes to the damage of the tumor tissue accompanied by the beginning of adaptation reaction in the organism.

  2. Linear verrucous epidermal nevi-effects of carbon dioxide laser therapy.

    PubMed

    Borzecki, Adam; Strus-Rosińska, Beata; Raszewska-Famielec, Magdalena; Sajdak-Wojtaluk, Agnieszka; Pilat, Pawel

    2016-10-01

    Linear epidermal nevus is a congenital malformation characterized by linear, often one-sided arrangement. The lesions are localized along the Blaschko's lines, are present at birth, or appear in early childhood. They can be single or multiple, and have various colors-from skin color to dark brown. These lesions persist through the whole life making a significant cosmetic defect. Here, we present three clinical cases of epidermal nevus treated with CO2 laser. In a female patient, verrucous, dark brown skin eruptions were observed at the back of earlobe and down the neck. In the cases of the male patients, the lesions were located in the area of the neck and left blade. The removal of nevi was performed in stages, by cutting and evaporation using a CO2 laser. A very good therapeutic effect was obtained. CO2 laser treatment is the method of choice for the removal of extensive epidermal nevi. It is characterized by high efficacy and safety.

  3. A semiconductor injection-switched high-pressure sub-10-picosecond carbon dioxide laser amplifier

    NASA Astrophysics Data System (ADS)

    Hughes, Michael Kon Yew

    A multiatmospheric-pressure-broadened CO2 laser amplifier was constructed to amplify sub-10-picosecond pulses generated with semiconductor switching. High-intensity, mid-infrared, amplified pulses have many applications: especially in fields such as non-linear optics, laser-plasma interaction, and laser particle acceleration. The injected pulses are produced by exciting GaAs (or an engineered, fast-recombination time semiconductor) with an ultrafast visible laser pulse to induce transient free carriers with sufficient density to reflect a co-incident hybrid-CO2 laser pulse. The short pulse is injected directly into the regenerative amplifier cavity from an intra-cavity semiconductor switch. The CO2-gas-mix amplifier is operated at 1.24 MPa which is sufficient to collisionally broaden the individual rotational spectral lines so that they merge to produce a gain spectrum wide enough to support pulses less than 10 ps long. After sufficient amplification, the pulse is switched out with another semiconductor switch pumped with a synchronized visible-laser pulse. This system is demonstrated and analysed spectrally and temporally. The pulse-train spectral analysis is done for a GaAs-GaAs double-switch arrangement using a standard spectrometer and two HgCdTe detectors; one of which is used for a reference signal. An infrared autocorrelator was designed and constructed to temporally analyse the pulse trains emerging from the amplifier. Interpretation of the results was aided by the development of a computer model for short-pulse amplification which incorporated saturation effects, rotational- and vibrational-mode energy redistribution between pulse round trips, and the gain enhancement due to one sequence band. The results show that a sub-10-picosecond pulse is injected into the cavity and that it is amplified with some trailing pulses at 18 ps intervals generated by coherent effects. The energy level reached, estimated through modelling, was >100 mJ/cm2.

  4. Reconstructive microsurgery of the female reproductive tract utilizing the carbon dioxide laser.

    PubMed

    Bellina, J H

    1982-01-01

    The use of the CO2 laser as an adjunct to microsurgery for restoration of the female reproductive tract was studied in 82 patients from March 1980-March 1981. No accidents or operative complications were experienced. The details of the surgical procedures using the CO2 laser beam to incise, excise, and vaporize tissue are presented. 21 conceptions occurred in 20 patients after limited exposure to pregnancy. This represents 48% of 42 patients at risk of conception. Follow-up is continuing in the patient population. Based upon experience to date, more conceptions are expected as exposure to pregnancy lengthens and more patients become at risk. (author's modified)

  5. Infrared image construction with computer-generated reflection holograms. [using carbon dioxide laser

    NASA Technical Reports Server (NTRS)

    Angus, J. C.; Coffield, F. E.; Edwards, R. V.; Mann, J. A., Jr.; Rugh, R. W.; Gallagher, N. C.

    1977-01-01

    Computer-generated reflection holograms hold substantial promise as a means of carrying out complex machining, marking, scribing, welding, soldering, heat treating, and similar processing operations simultaneously and without moving the work piece or laser beam. In the study described, a photographically reduced transparency of a 64 x 64 element Lohmann hologram was used to make a mask which, in turn, was used (with conventional photoresist techniques) to produce a holographic reflector. Images from a commercial CO2 laser (150W TEM(00)) and the holographic reflector are illustrated and discussed.

  6. Instantaneous x-ray radiation energy from laser produced polystyrene plasmas for shock ignition conditions

    SciTech Connect

    Shang, Wanli; Wei, Huiyue; Li, Zhichao; Yi, Rongqing; Zhu, Tuo; Song, Tianmin; Huang, Chengwu; Yang, Jiamin

    2013-10-15

    Laser target energy coupling mechanism is crucial in the shock ignition (SI) scheme, and x-ray radiation energy is a non-negligible portion of the laser produced plasma energy. To evaluate the x-ray radiation energy amount at conditions relevant to SI scheme, instantaneous x-ray radiation energy is investigated experimentally with continuum phase plates smoothed lasers irradiating layer polystyrene targets. Comparative laser pulses without and with shock spike are employed. With the measured x-ray angular distribution, full space x-ray radiation energy and conversion efficiency are observed. Instantaneous scaling law of x-ray conversion efficiency is obtained as a function of laser intensity and time. It should be pointed out that the scaling law is available for any laser pulse shape and intensity, with which irradiates polystyrene planar target with intensity from 2 × 10{sup 14} to 1.8 × 10{sup 15} W/cm{sup 2}. Numerical analysis of the laser energy transformation is performed, and the simulation results agree with the experimental data.

  7. Design and experimental study of a secondary hohlraum radiation source with laser focal spots blocked

    NASA Astrophysics Data System (ADS)

    Song, Tianming; Zhu, Tuo; Yang, Jiamin; Huang, Chengwu; Wang, Feng; Peng, Xiaoshi; Xu, Tao; Li, Zhichao; Zhang, Huan

    2016-01-01

    A design of secondary hohlraum radiation source with laser focal spots blocked is introduced. The hard x-ray radiation such as the gold M-band emission and hot electrons from the coronal plasma were designed to be shielded using a cylindrical shield. Three-dimensional view factor analysis was carried out to optimize the shield structure to achieve higher radiation temperature. An experiment was performed at Shenguang III prototype laser facility to verify the design. Velocity Interferometer System for Any Reflector was used to measure the shock wave speed in a three-stepped Al sample driven by this radiation source and the peak radiation temperature of the radiation source was estimated to be about 90 eV.

  8. Radiation Dose Measurement for High-Intensity Laser Interactions with Solid Targets at SLAC

    SciTech Connect

    Liang, Taiee

    2015-09-25

    A systematic study of photon and neutron radiation doses generated in high-intensity laser-solid interactions is underway at SLAC National Accelerator Laboratory. We found that these laser-solid experiments are being performed using a 25 TW (up to 1 J in 40 fs) femtosecond pulsed Ti:sapphire laser at the Linac Coherent Light Source’s (LCLS) Matter in Extreme Conditions (MEC) facility. Additionally, radiation measurements were performed with passive and active detectors deployed at various locations inside and outside the target chamber. Results from radiation dose measurements for laser-solid experiments at SLAC MEC in 2014 with peak intensity between 1018 to 7.1x1019 W/cm2 are presented.

  9. Surface modification of dental tissues by KrF excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Sivakumar, M.; Oliveira, V.; Vilar, R.

    2007-02-01

    Laser treatment is a promising technique for dental applications such as caries removal, dental hypersensitivity reduction and improvement of the bond strength between dentin and restoration materials. In this study the topographic and morphological changes induced in enamel and dentin surfaces by treating with KrF excimer laser radiation were studied as a function of the number of laser pulses and radiation fluence by scanning electron microscopy and optical profilometry. For enamel, independently of the fluence used, material removal occurs preferentially at the prisms sheaths, leading to the formation of surface pits of a few micrometers. For dentin, a cone-like topography develops when the tubules are approximately parallel to the laser beam direction and the radiation fluence is within the range 0.5 to 1.5 J/cm2. For higher fluences, the treated surfaces are flat and covered with a layer of re-solidified materials.

  10. Features of gallstone and kidney stone fragmentation by IR-pulsed Nd:YAG laser radiation

    NASA Astrophysics Data System (ADS)

    Batishche, Sergei A.

    1995-05-01

    It is shown that infra-red ((lambda) equals 1064 nm) long pulse (approximately 100 microsecond(s) ) radiation of YAG:Nd laser, operating in free generation regime, effectively fragments gallstones, urinary calculus and kidney stones. The features of the mechanism of this process are investigated. Laser lithotripsy is nowadays a method widely used for fragmentation of gallstones, urinary calculus and kidney stones. Flashlamp pumped dye lasers of microsecond duration are most often used for such purposes. Nevertheless, there are some reports on lithotripsies with nanosecond duration laser pulses (for example, Q-switched YAG:Nd laser). The mechanism of the laser fragmentation of such stones was supposed to be the next. The laser powerful radiation, delivered through the optical fiber, is absorbed by the material of the stone. As a result of such highly localized energy absorption, dense plasma is formed, which expands. Such plasma and vapor, liquid confined, forms a cavitation bubble. This bubble grows, reaches its most dimension and then collapses on itself in some hundreds of micro seconds. Shock waves generated during the growth and the collapse of these bubbles are the origin of fragmentation of the stone. It is necessary to say that there are rather confined data on the hundreds microsecond laser pulse fragmentation especially what concerns the usage of infra-red (IR) YAG:Nd lasers with long laser pulses. Clearing this problem would result in better understanding of the fragmentation mechanism and it could favor development of simple and more reliable laser systems for lithotripsy. In this work we report about investigation of features of an effective fragmentation of gallstones, urinary calculus and kidney stones under exposure of IR ((lambda) equals 1064 nm) radiation of repetitive YAG:Nd laser working in free generation regime.

  11. Spectroscopic support of laser remote sensing of the sulfur dioxide gas in the jet of engine exhaust gases

    NASA Astrophysics Data System (ADS)

    Voitsekhovskaya, O. K.; Kashirskii, D. E.; Egorov, O. V.

    2013-09-01

    The feasibility of SO2 registration in the plume of a jet engine as one of the methods of monitoring of its operation quality is investigated. Spectral characteristics are calculated using the line by line method, information-computing complex TRAVA developed by the authors, and the compiled spectroscopic database on high-temperature SO2. Unlike the HITRAN database, the original spectroscopic data possess predictability up to T = 1500 K. It is established that in case of active SO2 detection using a CO laser, the laser line corresponding to the 32-31 Р5 transition is promising for temperatures T = 300-1100 K. In addition, the most suitable range of the spectrum for passive sensing of hot SO2 in the engine plume - 1330.0-1331.6 cm-1 - is established in which the useful signal level exceeds background radiation for a minimum SO2 concentration (5 ppm).

  12. Exposure to copper-vapor laser as prophylaxis of radiative aggravations in patients treated for head or neck tumours

    SciTech Connect

    Evtushenko, V.A.; Popovich, V.I.; Soldatov, A.N.; Kitsmanyuk, Z.D.

    1993-06-01

    Possibilities are studied of using radiation of a copper vapor laser for prophylaxis of radiative aggravations in patients suffering from head and/or neck tumours. 114 Such patients were treated. A Malakhit laser was used for this study. It was shown that treating patients with laser radiation significantly reduces radiation reactions of skin and mucous membranes, so that a full course of radiation therapy may be performed without any forced breaks and treatment of maladies of epidermis and epithelium caused by radiation may be shortened.

  13. Active-medium inhomogeneities and optical quality of radiation of supersonic chemical oxygen-iodine lasers

    SciTech Connect

    Boreysho, A S; Druzhinin, S L; Lobachev, V V; Savin, A V; Strakhov, S Yu; Trilis, A V

    2007-09-30

    Optical inhomogeneities of the active medium of a supersonic chemical oxygen-iodine laser (COIL) and their effect on the radiation parameters are studied in the case when an unstable resonator is used. Classification of optical inhomogeneities and the main factors affecting the quality of COIL radiation are considered. The results of numerical simulation of a three-dimensional gas-dynamic active medium and an unstable optical resonator in the diffraction approximation are presented. The constraints in the fabrication of large-scale COILs associated with a deterioration of the optical quality of radiation are determined. (lasers)

  14. Neutrophils of the patients with cervical cancer after femtosecond laser radiation in vitro

    NASA Astrophysics Data System (ADS)

    Abakumova, Tatyana; Sysoliatin, Alexey; Antoneeva, Inna; Svetukhin, Vyacheslav; Arslanova, Dinara; Gening, Snezhanna

    2012-03-01

    The cytochemical analysis of the aerobic and anaerobic bactericidal, phagocytic activity, phagocytosis completeness, as well as membrane topology and rigidity has been performed with the Scanning probe microscopy (Solver Pro, NT-MDT, Russia) in neutrophils of the patients with cervical carcinoma treated with the Erbium laser radiation at different intensity. The obtained data reveal a significant effect of the femtosecond laser radiation on neutrophil morphofunctional state in patients with cervical cancer. The efficiency of the femtosecond radiation depends on its intensity and clinical stage of the cervical cancer.

  15. Terahertz radiation from a wire target irradiated by an ultra-intense laser pulse

    SciTech Connect

    Li Zhichao; Zheng Jian

    2007-05-15

    When an ultra-intense laser pulse impacts the tip of a wire whose other end is grounded, a strong return current can be driven along the wire because some energetic electrons generated in ultra-intense laser matter interaction can escape from the target and an electric field builds up. The wire then behaves like a current-carrying antenna that can emit electromagnetic radiations. If the duration of the driving pulse is several tens of femtoseconds, the radiation spectrum reaches a maximum at terahertz region, and the radiation power per solid angle could be as high as 10{sup 9} W/rad.

  16. Two-Color Radiation Generated in a Seeded Free-Electron Laser with Two Electron Beams.

    PubMed

    Petralia, A; Anania, M P; Artioli, M; Bacci, A; Bellaveglia, M; Carpanese, M; Chiadroni, E; Cianchi, A; Ciocci, F; Dattoli, G; Di Giovenale, D; Di Palma, E; Di Pirro, G P; Ferrario, M; Giannessi, L; Innocenti, L; Mostacci, A; Petrillo, V; Pompili, R; Rau, J V; Ronsivalle, C; Rossi, A R; Sabia, E; Shpakov, V; Vaccarezza, C; Villa, F

    2015-07-01

    We present the experimental evidence of the generation of coherent and statistically stable two-color free-electron laser radiation obtained by seeding an electron beam double peaked in energy with a laser pulse single spiked in frequency. The radiation presents two neat spectral lines, with time delay, frequency separation, and relative intensity that can be accurately controlled. The analysis of the emitted radiation shows a temporal coherence and a shot-to-shot regularity in frequency significantly enhanced with respect to the self-amplified spontaneous emission.

  17. [Study of enhancement effect of laser-induced crater on plasma radiation].

    PubMed

    Chen, Jin-Zhong; Zhang, Xiao-Ping; Guo, Qing-Lin; Su, Hong-Xin; Li, Guang

    2009-02-01

    Single pulses exported from high-energy neodymium glass laser were used to act on the same position of soil sample surface repeatedly, and the plasma emission spectra generated from sequential laser pulse action were collected by spectral recording system. The experimental results show that the laser-induced soil plasma radiation was enhanced continuously under the confinement effect of the crater walls, and the line intensities and signal-to-background ratios both had different improvements along with increasing the number of acting pulses. The photographs of the plasma image and crater appearance were taken to study the plasma shape, laser-induced crater appearance, and the mass of the ablated sample. The internal mechanism behind that laser-induced crater enhanced plasma radiation was researched. Under the sequential laser pulse action, the forming plasma as a result enlarges gradually first, leading to distortion at the trail of plasma plume, and then, its volume diminishes slowly. And also, the color of the plasma changes from buff to white gradually, which implies that the temperature increases constantly. The laser-induced crater had a regular shape, that is, the diameter increased from its bottom to top gradually, thus forming a taper. The mass of the laser-ablated substance descends along with increasing the amount of action pulse. Atomization degree of vaporized substance was improved in virtue of the crater confinement effect, Fresnel absorption produced from the crater walls reflection, and the inverse bremsstrahlung, and the plasma radiation intensity was enhanced as a result.

  18. A cesium plasma TELEC device for conversion of laser radiation to electric power

    NASA Technical Reports Server (NTRS)

    Britt, E. J.; Rasor, N. S.; Lee, G.; Billman, K. W.

    1978-01-01

    Tests of the thermoelectronic laser energy converter (TELEC) concept are reported. This device has been devised as a means to convert high-average-power laser radiation into electrical energy, a crucial element in any space laser power transmission scheme using the available high-power/efficiency infrared lasers. Theoretical calculations, based upon inverse bremsstrahlung absorption in a cesium plasma, indicate internal conversion efficiency up to 50% with an overall system efficiency of 42%. The experiments reported were made with a test cell designed to confirm the theoretical model rather than demonstrate efficiency; 10.6-micron laser-beam absorption was limited to about 0.001 of the incident beam by the short absorption region. Nevertheless, confirmatory results were obtained, and the conversion of absorbed radiation to electric power is estimated to be near 10%.

  19. Tunable Radiation Source by Coupling Laser-Plasma-Generated Electrons to a Periodic Structure

    SciTech Connect

    Jin, Z.; Chen, Z. L.; Kon, A.; Nakatsutsumi, M.; Zhuo, H. B.; Wang, H. B.; Zhang, B. H.; Gu, Y. Q.; Wu, Y. C.; Zhu, B.; Wang, L.; Yu, M. Y.; Sheng, Z. M.; Kodama, R.

    2011-12-23

    Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV/m field strength can be achieved by using appropriate grating parameters.

  20. Second harmonic generation of diode laser radiation in KNbO3

    NASA Astrophysics Data System (ADS)

    van Hulst, Niko F.; Heesink, Gerard J.; de Leeuw, H.; Bolger, Bouwe

    1991-02-01

    Both CW and pulsed diode lasers covering the wavelength region 855-912 nm have been investigated for the frequency doubling in KNbO. The influence of the spectral distribution mode character and the optical geometry of the laser beam have been investigated for several AlGaAs diode lasers. Second harmonic radiation with maximum efficiency of typically 1 has been detected both by temperature tuning CT 10-130 C noncritical phase matching) and by angle tuning. Results clearly demonstrate the critical aspects of the laser mode spectrum and the beam geometry as to the phase matching criterion in frequency doubling.

  1. Pulsed mid-infrared radiation from spectral broadening in laser wakefield simulations

    SciTech Connect

    Zhu, W.; Palastro, J. P.; Antonsen, T. M.

    2013-07-15

    Spectral red-shifting of high power laser pulses propagating through underdense plasma can be a source of ultrashort mid-infrared (MIR) radiation. During propagation, a high power laser pulse drives large amplitude plasma waves, depleting the pulse energy. At the same time, the large amplitude plasma wave provides a dynamic dielectric response that leads to spectral shifting. The loss of laser pulse energy and the approximate conservation of laser pulse action imply that spectral red-shifts accompany the depletion. In this paper, we investigate, through simulation, the parametric dependence of MIR generation on pulse energy, initial pulse duration, and plasma density.

  2. Explosive vaporization of metallic sodium microparticles by CW resonant laser radiation.

    PubMed

    Atutov, S N; Baldini, W; Biancalana, V; Calabrese, R; Guidi, V; Mai, B; Mariotti, E; Mazzocca, G; Moi, L; Pod'yachev, S P; Tomassetti, L

    2001-11-19

    Explosive vaporization of metallic Na microparticles stimulated by resonant cw laser radiation has been observed in a glass cell. Vaporization occurs at low laser-power density. The effect consists in the generation of optically thick and sharply localized Na vapor clouds propagating in the cell against the laser beam. The effect is explained by laser excitation of Na atoms, which collide onto the surface of the microparticles and transfer their internal energy. This causes other atoms to be vaporized and to continue the avalanche process. PMID:11736344

  3. Explosive vaporization of metallic sodium microparticles by CW resonant laser radiation.

    PubMed

    Atutov, S N; Baldini, W; Biancalana, V; Calabrese, R; Guidi, V; Mai, B; Mariotti, E; Mazzocca, G; Moi, L; Pod'yachev, S P; Tomassetti, L

    2001-11-19

    Explosive vaporization of metallic Na microparticles stimulated by resonant cw laser radiation has been observed in a glass cell. Vaporization occurs at low laser-power density. The effect consists in the generation of optically thick and sharply localized Na vapor clouds propagating in the cell against the laser beam. The effect is explained by laser excitation of Na atoms, which collide onto the surface of the microparticles and transfer their internal energy. This causes other atoms to be vaporized and to continue the avalanche process.

  4. Influence of low-intensity laser radiation upon the microflora of carious cavities and root canal

    NASA Astrophysics Data System (ADS)

    Shumilovitch, Bogdan R.; Nekrylov, Valery; Mazo, Leonid

    1995-04-01

    Laser stomatology- a relatively young branch of stomatology -has been developing actively lately. Bactericidal action of laser radiation enables to use it widely for processing carious cavities and root canals in the treatment of caries and its complications. 113 patients were studied by us. The 40 patients had antiseptic procedure of the caries cavity and then the procedure of laser therapy, so micro-organisms were found out in 26% cases. The 63 patients had antiseptic procedure only, so micro-organisms were found out in 70% cases. Control group were consisted of patients, where laser therapy was carried out without antiseptic remedies.

  5. Theoretical Investigation of Laser-Radiation Effects on Satellite Solar Cells

    NASA Astrophysics Data System (ADS)

    Abdel-Hadi, Yasser; El-Hameed, Afaf; Hamdy, Ola

    This research concerns with the studying of laser-powered solar panels for space applications. A model describing the laser effects on satellite solar cell has been developed. These effects are studied theoretically in order to determine the performance limits of the solar cells when they are powered by laser radiation during the satellite eclipse. A comparison between some different common types of the solar cells used for these purpose is considered in this study. The obtained results are reported to optimize the use of laser-powered satellites.

  6. Theory of a laser-plasma method for detecting terahertz radiation

    SciTech Connect

    Frolov, A. A.; Borodin, A. V.; Esaulkov, M. N.; Kuritsyn, I. I.; Shkurinov, A. P.

    2012-06-15

    A theory is developed for calculating the spectrum and the shape of a terahertz wave packet from the temporal profile of the energy of the second harmonic of the laser field generated during nonlinear interaction of laser and terahertz pulses in an optical-breakdown plasma. The spectral and temporal characteristics of the second-harmonic envelope and a terahertz pulse are shown to coincide only for short laser pulses. For long laser pulses, the second-harmonic spectral line shifts to the red and its temporal profile is determined by the time integral of the electric field of terahertz radiation.

  7. Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation

    SciTech Connect

    Gan, Li Mousen, Cheng; Xiaokang, Li

    2014-03-15

    In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.

  8. Calculation of laser induced impulse based on the laser supported detonation wave model with dissociation, ionization and radiation

    NASA Astrophysics Data System (ADS)

    Li, Gan; Cheng, Mousen; Li, Xiaokang

    2014-03-01

    In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter.

  9. Expansion of radiative cooling of the laser induced plasma

    SciTech Connect

    Wen, Sy-Bor; Mao, Xianglei; Liu, Chunyi; Greif, Ralph; Russo,Richard

    2006-05-05

    To study the expansion and cooling process of the laser induced plasma generated by nanosecond pulsed laser ablation, experiments have been conducted which measure the position of the external shockwaves and the temperature of the vapor plumes. The positions of external shockwaves were determined by a femtosecond laser time-resolved imaging system. Vapor plume temperature was determined from spectroscopic measurements of the plasma emission lines. A model which considers the mass, momentum, and energy conservation of the region affected by the laser energy was developed. It shows good agreement to the experimental data.

  10. On the Initiation of High Explosives by Laser Radiation

    SciTech Connect

    Rubenchik, A M

    2006-03-28

    The problem of laser initiation of high explosives in munitions is considered. In this situation, the laser illuminates a small spot on the casing, and lateral thermal transport affects the initiation temperature. We use a variational method to calculate the critical temperature for explosive initiation as a function the laser spot size, for common high explosives. The effect of the dwelling time of the irradiation is then evaluated. We demonstrate that in typical situations the critical temperature is determined by the dwelling time rather than by the laser spot size.

  11. Treatment of T1b glottic SCC: laser vs. radiation- a Canadian multicenter study

    PubMed Central

    2013-01-01

    Objective To assess the oncological and functional outcomes of T1b squamous cell carcinoma (SCC) of the glottic larynx treated with laser in comparison with radiation. Design A Canadian multicenter cohort study. Setting Three tertiary referral centers for head and neck cancer- Dalhousie University in Halifax, Nova Scotia, Western University in London, Ontario and the University of Manitoba, Winnipeg. Methods Patients with T1b glottic SCC who underwent transoral laser resection or radiation as the primary modality of treatment. Outcome measures Oncological outcomes were evaluated using local control, laryngeal preservation, disease free survival and disease specific survival. Voice outcomes were assessed using the Voice Handicap Index-10 (VHI-10). Results 63 patients met study criteria. 21 were treated with laser and 42 with radiation. Oncologic outcomes at 2 years for laser and radiation demonstrated local control of 95% and 85.9%; laryngeal preservation of 100% and 85.9%; disease free survival of 88.7% and 85.9% and overall survival of 94.1% and 94.8% respectively. VHI-10 data was available for 23/63 patients. During the last follow up visit VHI-10 ranged from 0 to 11 (median 6) in the laser group and 0 to 34 (median 7) in the radiation group. Conclusion T1b SCC of the glottis can be effectively treated with transoral laser microsurgery with oncological outcomes that are at least equivalent to radiation. For patients with VHI scores, voice quality was similar between the two groups. To our knowledge this is the first study directly comparing the oncologic and voice outcomes with laser and radiation for the treatment of glottic cancer involving the anterior commissure. PMID:23672802

  12. Absorption and scattering of laser radiation by the diffusion flame of aviation kerosene

    SciTech Connect

    Gvozdev, S V; Glova, A F; Dubrovskii, V Yu; Durmanov, S T; Krasyukov, A G; Lysikov, A Yu; Smirnov, G V; Solomakhin, V B

    2012-04-30

    The absorption coefficient of the radiation of a repetitively pulsed Nd : YAG laser with an average output power up to 6 W and of a cw ytterbium optical fibre laser with an output power up to 3 kW was measured in the diffusion flame of aviation kerosene burning on a free surface in the atmospheric air. The absorption coefficient as a function of flame length, radiation power, and radiation intensity, which was varied in the {approx}10{sup 3} - 5 Multiplication-Sign 10{sup 4} W cm{sup -2} range, was obtained for two distances (1 and 2 cm) between the laser beam axis and the surface. The coefficient of radiation absorption by kerosene flame was compared with that in ethanol and kerosene - ethanol mixture flames. The radiation power scattered by a small segment of the kerosene flame irradiated by Nd : YAG laser radiation was measured as a function of longitudinal and azimuthal coordinates. An estimate was made of the total scattered radiation power.

  13. Atmospheric propagation of high power laser radiation at different weather conditions

    NASA Astrophysics Data System (ADS)

    Pargmann, Carsten; Hall, Thomas; Duschek, Frank; Handke, Jürgen

    2016-05-01

    Applications based on the propagation of high power laser radiation through the atmosphere are limited in range and effect, due to weather dependent beam wandering, beam deterioration, and scattering processes. Security and defense related application examples are countermeasures against hostile projectiles and the powering of satellites and aircrafts. For an examination of the correlations between weather condition and laser beam characteristics DLR operates at Lampoldshausen a 130 m long free transmission laser test range. Sensors around this test range continuously monitor turbulence strength, visibility, precipitation, temperature, and wind speed. High power laser radiation is obtained by a TruDisk 6001 disk laser (Trumpf company) yielding a maximum output power of 6 kW at a wavelength of 1030 nm. The laser beam is expanded to 180 mm and focused along the beam path. Power and intensity distribution are measured before and after propagation, providing information about the atmospheric transmission and alterations of diameter and position of the laser beam. Backscattered laser light is acquired by a photo receiver. As a result, measurements performed at different weather conditions show a couple of correlations to the characteristics of the laser beam. The experimental results are compared to a numerical analysis. The calculations are based on the Maxwell wave equation in Fresnel approximation. The turbulence is considered by the introduction of phase screens and the "von Karman" spectrum.

  14. A new method and device of aligning patient setup lasers in radiation therapy.

    PubMed

    Hwang, Ui-Jung; Jo, Kwanghyun; Lim, Young Kyung; Kwak, Jung Won; Choi, Sang Hyuon; Jeong, Chiyoung; Kim, Mi Young; Jeong, Jong Hwi; Shin, Dongho; Lee, Se Byeong; Park, Jeong-Hoon; Park, Sung Yong; Kim, Siyong

    2016-01-08

    The aim of this study is to develop a new method to align the patient setup lasers in a radiation therapy treatment room and examine its validity and efficiency. The new laser alignment method is realized by a device composed of both a metallic base plate and a few acrylic transparent plates. Except one, every plate has either a crosshair line (CHL) or a single vertical line that is used for alignment. Two holders for radiochromic film insertion are prepared in the device to find a radiation isocenter. The right laser positions can be found optically by matching the shadows of all the CHLs in the gantry head and the device. The reproducibility, accuracy, and efficiency of laser alignment and the dependency on the position error of the light source were evaluated by comparing the means and the standard deviations of the measured laser positions. After the optical alignment of the lasers, the radiation isocenter was found by the gantry and collimator star shots, and then the lasers were translated parallel to the isocenter. In the laser position reproducibility test, the mean and standard deviation on the wall of treatment room were 32.3 ± 0.93 mm for the new method whereas they were 33.4 ± 1.49 mm for the conventional method. The mean alignment accuracy was 1.4 mm for the new method, and 2.1 mm for the conventional method on the walls. In the test of the dependency on the light source position error, the mean laser position was shifted just by a similar amount of the shift of the light source in the new method, but it was greatly magnified in the conventional method. In this study, a new laser alignment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method.

  15. Regeneration of spine disc and joint cartilages under temporal and space modulated laser radiation

    NASA Astrophysics Data System (ADS)

    Sobol, E.; Shekhter, A.; Baskov, A.; Baskov, V.; Baum, O.; Borchshenko, I.; Golubev, V.; Guller, A.; Kolyshev, I.; Omeltchenko, A.; Sviridov, A.; Zakharkina, O.

    2009-02-01

    The effect of laser radiation on the generation of hyaline cartilage in spine disc and joints has been demonstrated. The paper considers physical processes and mechanisms of laser regeneration, presents results of investigations aimed to optimize laser settings and to develop feedback control system for laser reconstruction of spine discs. Possible mechanisms of laser-induced regeneration include: (1) Space and temporary modulated laser beam induces nonhomogeneous and pulse repetitive thermal expansion and stress in the irradiated zone of cartilage. Mechanical effect due to controllable thermal expansion of the tissue and micro and nano gas bubbles formation in the course of the moderate (up to 45-50 oC) heating of the NP activate biological cells (chondrocytes) and promote cartilage regeneration. (2) Nondestructive laser radiation leads to the formation of nano and micro-pores in cartilage matrix. That promotes water permeability and increases the feeding of biological cells. Results provide the scientific and engineering basis for the novel low-invasive laser procedures to be used in orthopedics for the treatment cartilages of spine and joints. The technology and equipment for laser reconstruction of spine discs have been tested first on animals, and then in a clinical trial. Since 2001 the laser reconstruction of intervertebral discs have been performed for 340 patients with chronic symptoms of low back or neck pain who failed to improve with non-operative care. Substantial relief of back pain was obtained in 90% of patients treated who returned to their daily activities. The experiments on reparation of the defects in articular cartilage of the porcine joints under temporal and spase modulated laser radiation have shown promising results.

  16. A new method and device of aligning patient setup lasers in radiation therapy.

    PubMed

    Hwang, Ui-Jung; Jo, Kwanghyun; Lim, Young Kyung; Kwak, Jung Won; Choi, Sang Hyuon; Jeong, Chiyoung; Kim, Mi Young; Jeong, Jong Hwi; Shin, Dongho; Lee, Se Byeong; Park, Jeong-Hoon; Park, Sung Yong; Kim, Siyong

    2016-01-01

    The aim of this study is to develop a new method to align the patient setup lasers in a radiation therapy treatment room and examine its validity and efficiency. The new laser alignment method is realized by a device composed of both a metallic base plate and a few acrylic transparent plates. Except one, every plate has either a crosshair line (CHL) or a single vertical line that is used for alignment. Two holders for radiochromic film insertion are prepared in the device to find a radiation isocenter. The right laser positions can be found optically by matching the shadows of all the CHLs in the gantry head and the device. The reproducibility, accuracy, and efficiency of laser alignment and the dependency on the position error of the light source were evaluated by comparing the means and the standard deviations of the measured laser positions. After the optical alignment of the lasers, the radiation isocenter was found by the gantry and collimator star shots, and then the lasers were translated parallel to the isocenter. In the laser position reproducibility test, the mean and standard deviation on the wall of treatment room were 32.3 ± 0.93 mm for the new method whereas they were 33.4 ± 1.49 mm for the conventional method. The mean alignment accuracy was 1.4 mm for the new method, and 2.1 mm for the conventional method on the walls. In the test of the dependency on the light source position error, the mean laser position was shifted just by a similar amount of the shift of the light source in the new method, but it was greatly magnified in the conventional method. In this study, a new laser alignment method was devised and evaluated successfully. The new method provided more accurate, more reproducible, and faster alignment of the lasers than the conventional method. PMID:26894331

  17. Effects of laser-plasma interactions on terahertz radiation from solid targets irradiated by ultrashort intense laser pulses

    SciTech Connect

    Li Chun; Zhou Mulin; Ding Wenjun; Du Fei; Liu Feng; Li Yutong; Wang Weimin; Ma Jinglong; Chen Liming; Lu Xin; Dong Quanli; Wang Zhaohua; Wei Zhiyi; Sheng Zhengming; Zhang Jie; Lou Zheng; Shi Shengcai

    2011-09-15

    Interactions of 100-fs laser pulses with solid targets at intensities of 10{sup 18} W/cm{sup 2} and resultant terahertz (THz) radiation are studied under different laser contrast ratio conditions. THz emission is measured in the specular reflection direction, which appears to decrease as the laser contrast ratio varies from 10{sup -8} to 10{sup -6}. Correspondingly, the frequency spectra of the reflected light are observed changing from second harmonic dominant, three-halves harmonic dominant, to vanishing of both harmonics. Two-dimensional particle-in-cell simulation also suggests that this observation is correlated with the plasma density scale length change. The results demonstrate that the THz emission is closely related to the laser-plasma interaction processes. The emission is strong when resonance absorption is a key feature of the interaction, and becomes much weaker when parametric instabilities dominate.

  18. Influencing adherence properties of polymers by excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Breuer, J.; Metev, Simeon; Sepold, Gerd; Krueger, G.; Hennemann, O. D.

    1991-09-01

    The paper describes investigations concerning the enhancement of adhesive bonding strength between polypropylen (PP) and adhesive on a resinous basis by UV-laser-induced photochemical reactions. Possible mechanisms of the laser-activated processes are discussed. A preliminary result of the experimental examinations is the bonding strength enhancement of more than 5 X under certain conditions.

  19. Direct modification of bioactive phenothiazines by exposure to laser radiation.

    PubMed

    Pascu, Mihail-Lucian; Nastasa, Viorel; Smarandache, Adriana; Militaru, Andra; Martins, Ana; Viveiros, Miguel; Boni, Mihai; Andrei, Ionut Relu; Pascu, Alexandru; Staicu, Angela; Molnar, Joseph; Fanning, Seamus; Amaral, Leonard

    2011-05-01

    Whereas exposure of combinations of a phenothiazine and bacterium to incoherent UV increases the activity of the phenothiazine, exposure of the phenothiazine alone does not yield an increase of its activity. Because the laser beam energy is greater than that produced by the incoherent UV sources, exposure of phenothiazines to specific lasers may yield molecules with altered activities over that of the unexposed parent. Chlorpromazine, thioridazine and promethazine active against bacteria were exposed to two distinct lasers for varying periods of time. Absorption and fluorescence spectra were conducted prior to and post-exposure and the products of laser exposure evaluated for activity against a Staphylococcus aureus ATCC strain via a disk susceptibility assay. Exposure to lasers alters the absorption/fluorescence spectra of the phenothiazines; reduces the activity of thioridazine against the test bacterium; produces a highly active chlorpromazine compound against the test organism. Exposure of phenothiazines to lasers alters their structure that results in altered activity against a bacterium. This is the first report that lasers can alter the physico-chemico characteristics to the extent that altered bioactivity results. Exposure to lasers is expected to yield compounds that are difficult to make via chemical manipulation methods. A survey of selected patents of interest, even co-lateral for the subject of this article is shortly made.

  20. Calculation of thermal fluxes of plasma torch reradiation under the action of laser radiation on a condensed target

    SciTech Connect

    Rudenko, V. V.

    2010-12-15

    The problem of laser deposition with allowance for thermal radiation transport inside and outside the laser torch is considered in a multigroup approximation. The energy fluxes of laser torch thermal radiation onto a target in the far and near zones are calculated as functions of time and the character of the exposure. It is shown that absorption of thermal fluxes in the substrate and target in the course of laser deposition results in their substantial heating. The possibility of diagnosing thermal radiation fluxes from the laser torch by using photodetectors is demonstrated.

  1. Photocatalytic reactive oxygen species production and phototoxicity of titanium dioxide nanoparticles are dependent on the solar ultraviolet radiation spectrum.

    PubMed

    Ma, Hongbo; Brennan, Amanda; Diamond, Stephen A

    2012-09-01

    Generation of reactive oxygen species (ROS) by titanium dioxide nanoparticles (nano-TiO(2)) and its consequent phototoxicity to Daphnia magna were measured under different solar ultraviolet (UV) spectra by applying a series of optical filters in a solar simulator. Removing UV-B (280-320 nm) from solar radiation had no significant impact on photocatalytic ROS production of nano-TiO(2), whereas removal of UV-A (320-400 nm) decreased ROS production remarkably. Removal of wavelengths below 400 nm resulted in negligible ROS production. A linear correlation between ROS production and D. magna immobilization suggests that photocatalytic ROS production may be a predictor of phototoxicity for nano-TiO(2). Intracellular ROS production within D. magna was consistent with the immobilization of the organism under different solar UV spectra, indicating that oxidative stress was involved in phototoxicity. The dependence of nano-TiO(2) phototoxicity on environmentally realistic variations in solar radiation suggests that risk assessment of these nanomaterials requires careful evaluation of exposure conditions in the environment.

  2. Kinetics of laser pulse vaporization of uranium dioxide by mass spectrometry

    SciTech Connect

    Tsai, C.

    1981-11-01

    Safety analyses of nuclear reactors require knowledge of the evaporation behavior of UO/sub 2/ at temperatures well above the melting point of 3140 K. In this study, rapid transient heating of a small spot on a UO/sub 2/ specimen was accomplished by a laser pulse, which generates a surface temperature excursion. This in turn vaporizes the target surface and the gas expands into vacuum. The surface temperature transient was monitored by a fast-response automatic optical pyrometer. The maximum surface temperatures investigated range from approx. 3700 K to approx. 4300 K. A computer program was developed to simulate the laser heating process and calculate the surface temperature evolution. The effect of the uncertainties of the high temperature material properties on the calculation was included in a sensitivity study for UO/sub 2/ vaporization. The measured surface temperatures were in satisfactory agreements.

  3. Dissociation and regeneration kinetics of carbon dioxide in the active medium of sealed-off transverse RF-excited CO{sub 2} lasers

    SciTech Connect

    Vesnov, I G

    2010-06-23

    An improved mathematical model describing the dissociation and regenerations kinetics of carbon dioxide in the active medium of sealed-off transverse RF-excited CO{sub 2} lasers is presented. It is shown that the calculation of the active medium composition of such lasers requires the equations of the gas-mixture kinetics to take into account the diffuse flow of oxygen atoms on metal electrodes and on the surface of heterogeneous catalysts used to reduce the degree of the carbon dioxide dissociation. The rate constants of the heterogeneous recombination reaction CO + O {yields} CO{sub 2} on the surface of alumina ceramics and Al{sub 2}O{sub 3} are determined. (active media)

  4. Ultra-broadband hybrid infrared laser system

    NASA Astrophysics Data System (ADS)

    Budilova, O. V.; Ionin, A. A.; Kinyaevskiy, I. O.; Klimachev, Yu. M.; Kotkov, A. A.; Kozlov, A. Yu.

    2016-03-01

    A hybrid IR laser system consisting of molecular gas lasers with frequency conversion of laser radiation in a solid-state converter (nonlinear crystal) was developed. One of these gas lasers is a carbon monoxide laser operating in multi-line or single-line mode. Another one is a carbon dioxide laser operating in multi-line mode. The two lasers operate under Q-switching with a joint rotating mirror. Due to sum- and difference-frequency generation in nonlinear crystals, the laser system emits within wavelength range from 2.5 to 16.6 μm. The laser system emitting radiation over such an extremely wide wavelength range (2.7 octaves) is of interest for remote sensing and other applications connected with laser beam propagation in the atmosphere.

  5. Three-body fragmentation dynamics of carbon-dioxide dimers induced by intense femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Fan, Yameng; Wu, Chengyin; Xie, Xiguo; Wang, Peng; Zhong, Xunqi; Shao, Yun; Sun, Xufei; Liu, Yunquan; Gong, Qihuang

    2016-06-01

    We experimentally studied three-body fragmentation dynamics of (CO2)23+ generated by intense femtosecond laser fields. Three-dimensional momentum vectors as well as kinetic energies were measured for correlated fragmental ions using the technology of coincidence measurement. The results demonstrate that sequential fragmentation channel dominates for three-body fragmentation of (CO2)23+, in which the weak van der Waals bond breaks first and then one strong covalent bond.

  6. The influence of laser clipped by the laser entrance hole on hohlraum radiation measurement on Shenguang-III prototype.

    PubMed

    Yang, Dong; Li, Zhichao; Guo, Liang; Li, Sanwei; Yi, Rongqing; Song, Tianming; Zhang, Huan; Wang, Zhebin; Jiang, Xiaohua; Jiang, Shaoen; Ding, Yongkun

    2014-03-01

    Measuring the x-ray flux exiting the target's laser entrance hole (LEH) is the most common diagnostic that quantifies the x-ray intensity inside the laser-driven hohlraum. However, this signal accounts for only a small portion of the incident laser power and thus is likely to be affected by unwanted x-ray background from non-target area, leading to an overestimation of the hohlraum drive. Unwanted emission might be produced when the laser light is clipped by the LEH (LEH clipping) because of a lack of clearance for laser spot, or with a laser spot comprising of discrete structure, or even with a poor pointing accuracy. Its influence on the hohlraum radiation diagnostic is investigated on Shenguang-III prototype laser facility with the typical 1 ns square pulse. The experiment employed three types of targets to excite the unwanted x-ray background from LEH clipping, unconverted light, and both effects, respectively. This work gives an absolute evaluation of x-ray produced by the LEH clipping, which is measured by flat-response x-ray detectors (FXRD) at multiple view angles. The result indicates that there is little variation in measured emission to various view angles, because the unwanted x-rays are mainly generated at the side face of the LEH lip when laser is obliquely incident. Therefore, the LEH clipping brings more overestimation in hohlraum radiation measurement at larger view angle since the hohlraum LEH as an emitting source viewed by FXRD is decreased as the view angle increases. In our condition, the LEH clipping contributes 2%-3.5% overestimation to the hohlraum flux measurement. PMID:24689582

  7. The influence of laser clipped by the laser entrance hole on hohlraum radiation measurement on Shenguang-III prototype

    NASA Astrophysics Data System (ADS)

    Yang, Dong; Li, Zhichao; Guo, Liang; Li, Sanwei; Yi, Rongqing; Song, Tianming; Zhang, Huan; Wang, Zhebin; Jiang, Xiaohua; Jiang, Shaoen; Ding, Yongkun

    2014-03-01

    Measuring the x-ray flux exiting the target's laser entrance hole (LEH) is the most common diagnostic that quantifies the x-ray intensity inside the laser-driven hohlraum. However, this signal accounts for only a small portion of the incident laser power and thus is likely to be affected by unwanted x-ray background from non-target area, leading to an overestimation of the hohlraum drive. Unwanted emission might be produced when the laser light is clipped by the LEH (LEH clipping) because of a lack of clearance for laser spot, or with a laser spot comprising of discrete structure, or even with a poor pointing accuracy. Its influence on the hohlraum radiation diagnostic is investigated on Shenguang-III prototype laser facility with the typical 1 ns square pulse. The experiment employed three types of targets to excite the unwanted x-ray background from LEH clipping, unconverted light, and both effects, respectively. This work gives an absolute evaluation of x-ray produced by the LEH clipping, which is measured by flat-response x-ray detectors (FXRD) at multiple view angles. The result indicates that there is little variation in measured emission to various view angles, because the unwanted x-rays are mainly generated at the side face of the LEH lip when laser is obliquely incident. Therefore, the LEH clipping brings more overestimation in hohlraum radiation measurement at larger view angle since the hohlraum LEH as an emitting source viewed by FXRD is decreased as the view angle increases. In our condition, the LEH clipping contributes 2%-3.5% overestimation to the hohlraum flux measurement.

  8. Photodynamic Therapy with Ablative Carbon Dioxide Fractional Laser for Treating Bowen Disease

    PubMed Central

    Kim, Sue Kyung; Park, Ji-Youn; Song, Hyo Sang; Kim, You-Sun

    2013-01-01

    Background Topical photodynamic therapy (PDT) has been increasingly used to treat malignant skin tumors including the Bowen disease. However, patients could be displeased with the long incubation time required for conventional PDT. Objective We evaluated the efficacy and safety of PDT with a short incubation time of ablative CO2 fractional laser pretreatment for treating Bowen disease. Methods Ten patients were included. Just before applying the topical photosensitizer, all lesions were treated with ablative CO2 fractional laser, following the application of methyl aminolevulinate and irradiation with red light (Aktilite CL 128). Histological confirmation, rebiopsy, and clinical assessments were performed. Adverse events were also recorded. Results Five of the ten (50%) lesions showed a complete response (CR) within three PDT sessions. After four treatment sessions, all lesions except one penile shaft lesion (90%) achieved clinical and histological CR or clinical CR only. The average number of treatments to CR was 3.70±1.70. The treatments showed favorable cosmetic outcomes and no serious adverse events. Conclusion The results suggest that pretreatment with an ablative fractional CO2 laser before PDT has similar treatment efficacy and requires a shorter photosensitizer incubation time compared with the conventional PDT method. PMID:24003277

  9. Faraday rotation spectroscopy of nitrogen dioxide based on a widely tunable external cavity quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Zaugg, Christian A.; Lewicki, Rafal; Day, Tim; Curl, Robert F.; Tittel, Frank K.

    2011-01-01

    Faraday Rotation Spectroscopy (FRS) is a technique for the sensitive and selective detection of paramagnetic molecules or radicals such as NO, NO2, O2 or OH-. Moreover FRS is suitable for atmospheric measurements due to the insensitivity to non-paramagnetic interfering molecules such as H2O and CO2. Experimental results of an FRS sensor for the NO2detection employing an external-cavity quantum cascade laser (EC-QCL) are reported. The CW EC-QCL exhibits modehop free (MHF) tuning between 1600 cm-1 and 1650 cm-1. This allows targeting the optimum 441<--440 Q-branch NO2transition at 1613.25 cm-1. A rotation of the polarization state of the initially linearly polarized laser light is observed when an AC magnetic field is applied to the NO2 cell, placed between two nearly crossed Rochon polarizers. This rotation of the polarization state is proportional to the NO2 concentration and can be determined by a photodetector located after the second polarizer. For long-term continuous measurements a second branch consisting of a detector and reference cell filled with 0.2 % NO2 in N2 is used to lock the laser to the selected NO2 transition. A minimum detection sensitivity (1σ) of 1 parts per billion (ppbv) was obtained for a 1 sec lock-in time constant (TC).

  10. Effect of bound-state dressing in laser-assisted radiative recombination

    NASA Astrophysics Data System (ADS)

    Müller, Robert A.; Seipt, Daniel; Fritzsche, Stephan; Surzhykov, Andrey

    2015-11-01

    We present a theoretical study on the recombination of a free electron into the ground state of a hydrogenlike ion in the presence of an external laser field. Emphasis is placed on the effects caused by the laser dressing of the residual ionic bound state. To investigate how this dressing affects the total and angle-differential cross section of laser-assisted radiative recombination (LARR) we apply first-order perturbation theory and the separable Coulomb-Volkov continuum ansatz. Using this approach, detailed calculations are performed for low-Z hydrogenlike ions and laser intensities in the range from IL=1012 to 1013W/cm2 . It is seen that the total cross section as a function of the laser intensity is remarkably affected by the bound-state dressing. Moreover, the laser dressing becomes manifest as asymmetries in the angular distribution and the (energy) spectrum of the emitted recombination photons.

  11. Development of Laser Plasma X-ray Microbeam Irradiation System and Radiation Biological Application

    NASA Astrophysics Data System (ADS)

    Sato, Katsutoshi; Nishikino, Masaharu; Numasaki, Hodaka; Kawachi, Tetsuya; Teshima, Teruki; Nishimura, Hiroaki

    Laser plasma x-ray source has the features such as ultra short pulse, high brilliance, monochromaticity, and focusing ability. These features are excellent compared with conventional x-ray source. In order to apply the laser plasma x-ray source to the biomedical study and to more closely research the radiobilogical responce of the cancer cell such as radiation induced bystander effect, we have developed x-ray microbeam system using laser plasma x-ray source. The absorbed dose of laser plasma x-ray was estimated with Gafchromic EBT film and DNA double strand breaks on the cells were detected by immunofluorescence staining. When the cells were irradiated with laser plasma x-ray, the circular regions existing γ-H2AX positive cells were clearly identified. The usefulness of the laser plasma x-ray on the radiobiological study was proved in this research.

  12. Ordered many-electron motions in atoms and x-ray lasers. [Subpicosecond ultraviolet laser radiation

    SciTech Connect

    Rhodes, C.K.

    1986-01-01

    Subpicosecond ultraviolet laser technology is enabling the exploration of nonlinear atomic interactions with electric field strengths considerably in excess of an atomic unit. As this regime is approached, experiments studying multiple ionization, photoelectron energy spectra, and harmonically produced radiation all exhibit strong nonlinear coupling. Peak total energy transfer rates on the order of approx.2 x 10/sup -4/ W/atom have been observed at an intensity of approx.10/sup 16/ W/cm/sup 2/, and it is expected that energy transfer rates approaching approx.0.1 to 1 W/atom will occur under more extreme conditions for which the ultraviolet electric field E is significantly greater than e/a/sub 0//sup 2/. In this high intensity regime, a wide range of new nonlinear phenomena will be open to study. These will include the possibility of ordered driven motions in atoms, molecules, and plasmas, mechanisms involving collisions, and relativistic processes such as electron-positron pair production. An understanding of these physical interactions may provide a basis for the generation of stimulated emission in the x-ray range. 100 refs., 8 figs.

  13. Analgesic effect of low-power infrared laser radiation in rats

    NASA Astrophysics Data System (ADS)

    Mrowiec, Janina; Sieron, Aleksander; Plech, Andrzej; Cieslar, Grzegorz; Biniszkiewicz, Tomasz; Brus, Ryszard

    1997-12-01

    The aim of the study was to confirm the analgesic effect of low-power laser radiation with a tail-immersion test and check if nitric oxide is involved in laser radiation-induced analgesia in rats. The experiment was performed on male Wistar rats. On the day of experiment the scull of rats was exposed to IR laser radiation for 10 min and antinociceptive effect was determined by means of tail immersion test. The experiments were also performed on 1-NAME and methylene blue pretreated rates, in which both chemicals were administered into right lateral brain ventricle. The results were compared to the ones obtained in the control group in which sham irradiation was made. It was observed that 10 min. exposure to low-power IR laser radiation induced only transient distinct antinociceptive effect in rats. This effect was prevented by ICV. injection of 1-NAME, an inhibitor of nitric oxide synthase and methylene blue, an inhibitor of soluble guanylate cyclase. It seems that nitric oxide is involved in mechanism of low-power laser radiation- induced analgesia.

  14. A study of the radiation of a Nd:YAG laser-MIG hybrid plasma

    NASA Astrophysics Data System (ADS)

    Li, Zhiyong; Wang, Wei; Wang, Xuyou; Li, Huan

    2010-02-01

    To study the coupling of a Nd:YAG laser beam and a MIG arc with the spectrum of the plasma, a new hollow probe method is used to collect radiation from specific points within the arc plasma. With the probe, the spatial distributions of the MIG arc radiation with and without the Nd:YAG laser hybrid plasma are collected and analyzed by a fiber spectrometer. Through analysis of the spectrum, radiation in the ultraviolet (Fe II dominated), visible (Fe I dominated) and infra (Ar I dominated) spectral zones are acquired for comparison of the difference between the MIG and Laser-MIG hybrid welding processes. The electronic temperature is calculated using the Boltzmann plot method and the electronic density is calculated using the Stark broadening method. The results show that the Laser-MIG hybrid welding processes cause the plasma energy to focus on the center of the welding arc and approach the welding pool. An ionizing duct abundant with Fe ions will be formed near the position of the impinging laser beam, which makes the welding arc stable. The electronic temperature of the Laser-MIG hybrid welding arc is a little higher than that of the MIG. The electronic density of Laser-MIG hybrid welding is higher than that of the MIG.

  15. Demonstration of Coherent Terahertz Transition Radiation from Relativistic Laser-Solid Interactions

    NASA Astrophysics Data System (ADS)

    Liao, Guo-Qian; Li, Yu-Tong; Zhang, Yi-Hang; Liu, Hao; Ge, Xu-Lei; Yang, Su; Wei, Wen-Qing; Yuan, Xiao-Hui; Deng, Yan-Qing; Zhu, Bao-Jun; Zhang, Zhe; Wang, Wei-Min; Sheng, Zheng-Ming; Chen, Li-Ming; Lu, Xin; Ma, Jing-Long; Wang, Xuan; Zhang, Jie

    2016-05-01

    Coherent transition radiation in the terahertz (THz) region with energies of sub-mJ/pulse has been demonstrated by relativistic laser-driven electron beams crossing the solid-vacuum boundary. Targets including mass-limited foils and layered metal-plastic targets are used to verify the radiation mechanism and characterize the radiation properties. Observations of THz emissions as a function of target parameters agree well with the formation-zone and diffraction model of transition radiation. Particle-in-cell simulations also well reproduce the observed characteristics of THz emissions. The present THz transition radiation enables not only a potential tabletop brilliant THz source, but also a novel noninvasive diagnostic for fast electron generation and transport in laser-plasma interactions.

  16. Brain lesion induced by 1319nm laser radiation

    NASA Astrophysics Data System (ADS)

    Yang, Zaifu; Chen, Hongxia; Wang, Jiarui; Chen, Peng; Ma, Ping; Qian, Huanwen

    2010-11-01

    The laser-tissue interaction has not been well defined at the 1319 nm wavelength for brain exposure. The goal of this research effort was to identify the behavioral and histological changes of brain lesion induced by 1319 nm laser. The experiment was performed on China Kunming mice. Unilateral brain lesions were created with a continuous-wave Nd:YAG laser (1319nm). The brain lesions were identified through behavioral observation and histological haematoxylin and eosin (H&E) staining method. The behavior change was observed for a radiant exposure range of 97~773 J/cm2. The histology of the recovery process was identified for radiant exposure of 580 J/cm2. Subjects were sacrificed 1 hour, 1 week, 2 weeks, 3 months, 7 months and 13 months after laser irradiation. Results showed that after laser exposure, behavioral deficits, including kyphosis, tail entasia, or whole body paralysis could be noted right after the animals recovered from anesthesia while gradually disappeared within several days and never recurred again. Histologically, the laser lesion showed a typical architecture dependent on the interval following laser treatment. The central zone of coagulation necrosis is not apparent right after exposure but becomes obvious within several days. The nerotic tissue though may persist for a long time, will finally be completely resorbed. No carbonization granules formed under our exposure condition.

  17. Dynamics of radiation from a wide-aperture laser under conditions of coherent interaction of the radiation with a medium

    SciTech Connect

    Zaikin, A P

    1999-11-30

    The dynamics of the radiation from a wide-aperture laser is investigated taking account of the finite response time of the polarisation of the active medium. This radiation is described by the Maxwell - Bloch equations, which are simplified for the case of fast relaxation of the polarisation. The methods of a qualitative theory of nonlinear dynamics systems are used to find the conditions for instability of the steady-state homogeneous laser radiation field in a Fabry - Perot cavity. It is shown that, as a rule, the system becomes unstable via an Andronov - Hopf bifurcation and the transverse profile of the optical field is modulated by a travelling self-wave. The main parameters of these self-waves are determined and their growth increment is found. It is shown that each of the roots of the characteristic equation of the system can be used to estimate the stability range of the self-wave solutions. The laser equations are also solved numerically and the results obtained are in good agreement with the conclusions of the qualitative theory. The numerical results predict harmonic and quasi-harmonic self-waves (with multiplication of their period) and also behaviour resembling chaos. (lasers)

  18. New technique for feline carbon dioxide laser onychectomy by resection of the redundant epidermis of the ungual crest

    NASA Astrophysics Data System (ADS)

    Young, William P.

    2000-05-01

    A new technique for feline carbon dioxide laser onychectomy can further minimize postoperative pain and complications in any age animal. This procedure is accomplished by resection of the redundant epidermis over the ungual crest. Resection of the redundant epidermis allows complete dissection and removal of the claw from a strictly cranio-dorsal approach, thereby minimizing trauma to the surrounding tissues and post- operative complications. The laser setting is preferred at four to six watts continuous power. The epidermis of the ungual crest is resected in a circumferential manner at its most distal edge. This tissue is pushed proximally over the ungual crest. A second circumferential incision is made 3 mm proximal to the first incision. Deeper subcutaneous fascia is also pushed proximally over the ungual crest. An incision of the extensor tendon is made at its insertion on the ungual crest keeping the redundant epidermis proximal to this incision. The incision through the extensor tendon is continued deeper to the synovium of PII and PIII. Gentle traction in a palmar direction will disarticulate the joint space between PII and PIII. Incisions into the lateral and medial collateral ligaments from a cranio-dorsal origin in palmar direction further disarticulate the joint. Care must be exercised to preserve all epidermal tissue lying immediately adjacent to the collateral ligaments. Continual palmar traction will expose the base of PIII and the insertion of the flexor tendon. A dorsal incision is made into the flexor tendon in a palmar direction. Extreme palmar rotation of PIII will allow the dissection of the subcutaneous tissue of the pad from PIII. The redundant epidermal tissue will now cover the majority of the onychectomy site. No sutures or tissue adhesive are advised.

  19. Laser-plasma SXR/EUV sources: adjustment of radiation parameters for specific applications

    NASA Astrophysics Data System (ADS)

    Bartnik, A.; Fiedorowicz, H.; Fok, T.; Jarocki, R.; Kostecki, J.; Szczurek, A.; Szczurek, M.; Wachulak, P.; Wegrzyński, Ł.

    2014-12-01

    In this work soft X-ray (SXR) and extreme ultraviolet (EUV) laser-produced plasma (LPP) sources employing Nd:YAG laser systems of different parameters are presented. First of them is a 10-Hz EUV source, based on a double-stream gaspuff target, irradiated with the 3-ns/0.8J laser pulse. In the second one a 10 ns/10 J/10 Hz laser system is employed and the third one utilizes the laser system with the pulse shorten to approximately 1 ns. Using various gases in the gas puff targets it is possible to obtain intense radiation in different wavelength ranges. This way intense continuous radiation in a wide spectral range as well as quasi-monochromatic radiation was produced. To obtain high EUV or SXR fluence the radiation was focused using three types of grazing incidence collectors and a multilayer Mo/Si collector. First of them is a multfoil gold plated collector consisted of two orthogonal stacks of ellipsoidal mirrors forming a double-focusing device. The second one is the ellipsoidal collector being part of the axisymmetrical ellipsoidal surface. Third of the collectors is composed of two aligned axisymmetrical paraboloidal mirrors optimized for focusing of SXR radiation. The last collector is an off-axis ellipsoidal multilayer Mo/Si mirror allowing for efficient focusing of the radiation in the spectral region centered at λ = 13.5 ± 0.5 nm. In this paper spectra of unaltered EUV or SXR radiation produced in different LPP source configurations together with spectra and fluence values of focused radiation are presented. Specific configurations of the sources were assigned to various applications.

  20. Modeling of carbon monoxide oxidation kinetics over NASA carbon dioxide laser catalysts

    NASA Technical Reports Server (NTRS)

    Herz, Richard K.

    1989-01-01

    The recombination of CO and O2 formed by the dissociation of CO2 in a sealed CO2 laser discharge zone is examined. Conventional base-metal-oxide catalysts and conventional noble-metal catalysts are not effective in recombining the low O2/CO ratio at the low temperatures used by the lasers. The use of Pt/SnO2 as the noble-metal reducible-oxide (NMRO), or other related materials from Group VIIIA and IB and SnO2 interact synergistically to produce a catalytic activity that is substantially higher than either componet separately. The Pt/SnO2 and Pd/SnO2 were reported to have significant reaction rates at temperatures as low as -27 C, conditions under which conventional catalysts are inactive. The gas temperature range of lasers is 0 + or - 40 C. There are three general ways in which the NMRO composite materials can interact synergistically: one component altering the properties of another component; the two components each providing independent catalytic functions in a complex reaction mechanism; and the formation of catalytic sites through the combination of two components at the atomic level. All three of these interactions may be important in low temperature CO oxidation over NMRO catalysts. The effect of the noble metal on the oxide is discussed first, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials.

  1. Effects induced by XeCl laser radiation and germicidal lamp radiation on E. coli strains survival and mutability

    NASA Astrophysics Data System (ADS)

    Belloni, F.; Alifano, P.; Lorusso, A.; Monaco, C.; Nassisi, V.; Talà, A.; Tredici, M.

    2006-04-01

    In this work the mutagenic effect on Escherichia coli strains induced by UV radiation emitted by a XeCl laser (λ = 308 nm) has been analysed as a function of the exposure dose and compared with the effect induced by 254 nm radiation emitted by a conventional germicidal lamp. E. coli strains, wild-type (recA+) and mutant (recA1, defective in DNA damage repair systems), plated on LB agar, supplemented with rifampicin when requested, were irradiated by means of a germicidal lamp in the dose range 0 - 9 mJ/cm2. Similar strains were exposed to 308 nm pulsed laser radiation (τ = 20 ns FWHM; max. pulse energy: 100 mJ) in the dose range 0-1.0 x 10 4 mJ/cm2. The discrepancy between the results obtained with the lamp and the laser on the mutation frequency, suggested that the biological response to the two radiation sources involves distinct mechanisms. This hypothesis was supported by the evidence that exposure to near-UV 308 nm induced mutagenesis in the recA-defective strain at an extent considerably higher than in the recA-proficient strain.

  2. Managing metabolic model deficiencies for routine radiation protection purposes at a thorium dioxide facility.

    PubMed

    Berger, C D; Kelly, B A; Venezia, C

    1998-02-01

    At a metallurgical facility using thorium dioxide feed materials, a number of conventional direct- and indirect-bioassay methods were potentially suitable monitoring methodologies when industry-standard dose assessment methodologies were based upon ICRP recommendations issued in 1959. When the ICRP recommended a different dose assessment methodology in 1977, the intake limits for thorium dropped significantly, and conventional bioassay methods for routine monitoring were rendered ineffective. While determining the technical basis for its air monitoring program, the facility noted that the radioactive materials used as feed to the process were highly insoluble. Therefore, their solubility in simulated lung fluids was determined. The results of this determination indicated that the facility's materials, if inhaled, dissolve in the lung at a half-time that is significantly longer than that contained in international consensus standards for Y-class compounds. They also indicated that the secondary dose limits, if adjusted to eliminate the dose contribution from translocated radionuclides, should be higher, and that a derived air concentration based upon more recent international recommendations is more appropriate for use in the facility's routine monitoring program. PMID:9450596

  3. Particle track simulation by N2 laser radiation

    NASA Astrophysics Data System (ADS)

    Gushchin, E.; Lebedev, A. N.; Somov, S. V.

    1984-07-01

    The use of N2 high-power pulsed lasers to simulate particle tracks is discussed. In gas-filled detectors, the tracks are attributed to either direct photoionization of the surface of dust particles or to two-photon ionization of unidentified molecular impurities with an ionization potential less than 2 hnu. Two-photon ionization of various saturated organic vapors is investigated and it is found that the addition of these substances to the working gas makes it possible to decrease the laser power and obtain laser tracks with virtually any electron density. It is also shown that the electron density is proportional to the square of the light power. Laser track simulation has applications in spatial and energy calibration of positive-sensitive detectors, the measurement of the drift of particle tracks in streamer, spark, and bubble chambers, and photoionization molecular spectroscopy.

  4. Oxygen assisted interconnection of silver nanoparticles with femtosecond laser radiation

    SciTech Connect

    Huang, H.; Zhou, Y.; Duley, W. W.

    2015-12-14

    Ablation of silver (Ag) nanoparticles in the direction of laser polarization is achieved by utilizing femtosecond laser irradiation in air at laser fluence ranging from ∼2 mJ/cm{sup 2} to ∼14 mJ/cm{sup 2}. This directional ablation is attributed to localized surface plasmon induced localized electric field enhancement. Scanning electron microscopy observations of the irradiated particles in different gases and at different pressures indicate that the ablation is further enhanced by oxygen in the air. This may be due to the external heating via the reactions of its dissociation product, atomic oxygen, with the surface of Ag particles, while the ablated Ag is not oxidized. Further experimental observations show that the ablated material re-deposits near the irradiated particles and results in the extension of the particles in laser polarization direction, facilitating the interconnection of two well-separated nanoparticles.

  5. Infrared radiation and inversion population of CO2 laser levels in Venusian and Martian atmospheres

    NASA Technical Reports Server (NTRS)

    Gordiyets, B. F.; Panchenko, V. Y.

    1983-01-01

    Formation mechanisms of nonequilibrium 10 micron CO2 molecule radiation and the possible existence of a natural laser effect in the upper atmospheres of Venus and Mars are theoretically studied. An analysis is made of the excitation process of CO2 molecule vibrational-band levels (with natural isotropic content) induced by direct solar radiation in bands 10.6, 9.4, 4.3, 2.7 and 2.0 microns. The model of partial vibrational-band temperatures was used in the case. The problem of IR radiation transfer in vibrational-rotational bands was solved in the radiation escape approximation.

  6. Resonant terahertz radiation from warm collisional inhomogeneous plasma irradiated by two Gaussian laser beams

    NASA Astrophysics Data System (ADS)

    Niknam, A. R.; Banjafar, M. R.; Jahangiri, F.; Barzegar, S.; Massudi, R.

    2016-05-01

    Terahertz (THz) radiation generation by the interaction of two co-propagating high intensity laser beams with a warm collisional inhomogeneous plasma is analytically investigated. By presenting the dielectric permittivity of plasma and taking into account the ponderomotive force, the nonlinear current at THz frequency is obtained. A secondary resonant enhancement of THz radiation is observed, in addition to that occurs at the plasma frequency, which can be tuned by plasma density and temperature. Moreover, we show that for each beat frequency, there exists an optimum temperature at which THz radiation is maximized. It is also shown that the power and efficiency of THz radiation decrease by increasing the collision frequency.

  7. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Thermally induced optical damage to barium-sodium niobate crystals

    NASA Astrophysics Data System (ADS)

    Baryshev, S. A.; Goncharova, I. F.; Konvisar, P. G.; Kuznetsov, V. A.

    1990-06-01

    Thermally induced optical damage (TIOD) was observed in undoped barium-sodium niobate (BSN) crystals as a result of changes in their temperature. This damage was deduced from the behavior of YAG:Nd3+ laser radiation when a BSN crystal was inserted in the resonator and also using a helium-neon laser probe beam. The experimental results were satisfactorily explained by the familiar pyroelectric model of TIOD and, in the crystals studied, an inhomogeneity of the conductivity rather than an inhomogeneity of the pyroelectric constant played the main role.

  8. Development and Preliminary Tests of an Open-Path Airborne Diode Laser Absorption Instrument for Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Diskin, G. S.; DiGangi, J. P.; Yang, M. M.; Rana, M.; Slate, T. A.

    2015-12-01

    Carbon dioxide (CO2) is well known for its importance as an atmospheric greenhouse gas, with many sources and sinks around the globe. Understanding the fluxes of carbon into and out of the atmosphere is a complex and daunting challenge. One tool applied by scientists to measure the vertical flux of CO2 near the surface uses the eddy covariance technique, most often from towers but also from aircraft flying specific patterns over the study area. In this technique, variations of constituents of interest are correlated with fluctuations in the local vertical wind velocity. Measurement requirements are stringent, particularly with regard to precision, sensitivity to small changes, and temporal sampling rate. In addition, many aircraft have limited payload capability, so instrument size, weight, and power consumption are also important considerations. We report on the development and preliminary application of an airborne sensor for the measurement of atmospheric CO2. The instrument, modeled on the successful DLH (Diode Laser Hygrometer) series of instruments, has been tested in the laboratory and on the NASA DC-8 aircraft. Performance parameters such as accuracy, precision, sensitivity, specificity, and temporal response are discussed in the context of typical atmospheric variability and suitability for flux measurement applications. On-aircraft, in-flight intercomparison data have been obtained and will be discussed as well. Performance of the instrument has been promising, and continued flight testing is planned during 2016.

  9. Development and Preliminary Tests of an Open-Path Airborne Diode Laser Absorption Instrument for Carbon Dioxide

    NASA Technical Reports Server (NTRS)

    Diskin, Glenn S.; DiGangi, Joshua P.; Yang, Melissa; Slate, Thomas A.; Rana, Mario

    2015-01-01

    Carbon dioxide (CO2) is well known for its importance as an atmospheric greenhouse gas, with many sources and sinks around the globe. Understanding the fluxes of carbon into and out of the atmosphere is a complex and daunting challenge. One tool applied by scientists to measure the vertical flux of CO2 near the surface uses the eddy covariance technique, most often from towers but also from aircraft flying specific patterns over the study area. In this technique, variations of constituents of interest are correlated with fluctuations in the local vertical wind velocity. Measurement requirements are stringent, particularly with regard to precision, sensitivity to small changes, and temporal sampling rate. In addition, many aircraft have limited payload capability, so instrument size, weight, and power consumption are also important considerations. We report on the development and preliminary application of an airborne sensor for the measurement of atmospheric CO2. The instrument, modeled on the successful DLH (Diode Laser Hygrometer) series of instruments, has been tested in the laboratory and on the NASA DC-8 aircraft. Performance parameters such as accuracy, precision, sensitivity, specificity, and temporal response are discussed in the context of typical atmospheric variability and suitability for flux measurement applications. On-aircraft, in-flight data have been obtained and are discussed as well. Performance of the instrument has been promising, and continued flight testing is planned during 2016.

  10. On stochastic heating of electrons by intense laser radiation in the presence of electrostatic potential well

    SciTech Connect

    Krasheninnikov, S. I.

    2014-10-15

    A simple model developed by Paradkar et al. [Phys. Plasmas 19, 060703 (2012)] for the study of synergistic effects of electrostatic potential well and laser radiation is extended for the case where electric field of the well is accelerating electrons moving in the direction of the laser field propagation. It was found that in these cases, the rate of stochastic heating of energetic electrons remains virtually the same as in Paradkar et al. [Phys. Plasmas 19, 060703 (2012)], where electric field in electrostatic potential was slowing down electrons moving in the direction of the laser field propagation. However, the heating of electrons with relatively low energy can be sensitive to the orientation of the electrostatic potential well with respect to the direction of the laser radiation propagation.

  11. Generation of coherent terahertz radiation in ultrafast laser-gas interactions

    SciTech Connect

    Kim, Ki-Yong

    2009-05-15

    The generation of intense terahertz radiation in ultrafast laser-gas interactions is studied on a basis of transient electron current model. When an ultrashort pulse laser's fundamental and its second harmonic fields are mixed to ionize a gas, a nonvanishing, directional photoelectron current can be produced, which simultaneously emits terahertz radiation in the far field. Here, the generation mechanism is examined with an analytic derivation and numerical simulations, in which tunneling ionization and subsequent electron motion in the combined laser field play a key role. In the simulations, three types of laser-gas interactions are considered: (i) mixing the fundamental and its second harmonic fields, (ii) mixing nonharmonic, two-color fields, and (iii) focusing single-color, few-cycle pulses. In these interactions, terahertz generation and other nonlinear effects driven by the transient current are investigated. In particular, anticorrelation between terahertz and second (or third) harmonic generation is observed and analyzed.

  12. Quantum mechanical theory of collisional ionization in the presence of intense laser radiation

    NASA Technical Reports Server (NTRS)

    Bellum, J. C.; George, T. F.

    1978-01-01

    The paper presents a quantum mechanical formalism for treating ionizing collisions occurring in the presence of an intense laser field. Both the intense laser radiation and the internal electronic continuum states associated with the emitted electrons are rigorously taken into account by combining discretization techniques with expansions in terms of electronic-field representations for the quasi-molecule-plus-photon system. The procedure leads to a coupled-channel description of the heavy-particle dynamics which involves effective electronic-field potential surfaces and continua. It is suggested that laser-influenced ionizing collisions can be studied to verify the effects of intense laser radiation on inelastic collisional processes. Calculation procedures for electronic transition dipole matrix elements between discrete and continuum electronic states are outlined.

  13. Interaction of near-IR laser radiation with plasma of a continuous optical discharge

    NASA Astrophysics Data System (ADS)

    Zimakov, V. P.; Kuznetsov, V. A.; Solovyov, N. G.; Shemyakin, A. N.; Shilov, A. O.; Yakimov, M. Yu.

    2016-01-01

    The interaction of 1.07-μm laser radiation with plasma of a continuous optical discharge (COD) in xenon and argon at a pressure of p = 3-25 bar and temperature of T = 15 kK has been studied. The threshold power required to sustain COD is found to decrease with increasing gas pressure to P t < 30 W in xenon at p > 20 bar and to P t < 350 W in argon at p > 15 bar. This effect is explained by an increase in the coefficient of laser radiation absorption to 20-25 cm-1 in Xe and 1-2 cm-1 in Ar due to electronic transitions between the broadened excited atomic levels. The COD characteristics also depend on the laser beam refraction in plasma. This effect can be partially compensated by a tighter focusing of the laser beam. COD is applied as a broadband light source with a high spectral brightness.

  14. Testing astrophysical radiation hydrodynamics codes with hypervelocity jet experiments on the nova laser

    SciTech Connect

    Estabrook, K; Farley, D; Glendinning, S G; Remington, B A; Stone, J; Turner, N

    1999-09-22

    Recent shock tube experiments using the Nova laser facility have demonstrated that strong shocks and highly supersonic flows similar to those encountered in astrophysical jets can be studied in detail through carefully controlled experiment. We propose the use of high power lasers such as Nova, Omega, and NIF to perform experiments on radiation hydrodynamic problems such as jets involving the multidimensional dynamics of strong shocks. High power lasers are the only experimental facilities that can reach the very high Mach number regime. The experiments will serve both as diagnostics of astrophysically interesting gas dynamic problems, and could also form the basis of test problems for numerical algorithms for astrophysical radiation hydrodynamic codes, The potential for experimentally achieving a strongly radiative jet seems very good.

  15. Radiation-induced defects in Pr3+-activated LiYF4 laser host

    NASA Astrophysics Data System (ADS)

    Dhoble, S. J.; Deshpande, S. P.; Pode, R. B.; Dhoble, N. S.; Gundurao, T. K.

    2004-11-01

    Rare earth doped fluorides have been used in laser applications. Not much is known about the effect of ionizing radiation on the lasing and other properties of fluorides. Therefore, in recent years much attention has been paid to the study of radiation-induced defects in laser materials, as they affect the optical and stimulated emission properties. The defect formation by gamma-ray irradiation in Pr3+ activated LiYF4, powder prepared by melt method, have been studied by thermoluminescence and electron spin resonance techniques and are reported in this paper. It is shown that LiYF4:Pr3+ is sensitive to gamma-ray radiation. Characterization of this laser material using ESR and photoluminescence techniques is also described.

  16. Signatures of quantum radiation reaction in laser-electron-beam collisions

    SciTech Connect

    Wang, H. Y.; Yan, X. Q.; Zepf, M.

    2015-09-15

    Electron dynamics in the collision of an electron beam with a high-intensity focused ultrashort laser pulse are investigated using three-dimensional QED particle-in-cell (PIC) simulations, and the results are compared with those calculated by classical Landau and Lifshitz PIC simulations. Significant differences are observed from the angular dependence of the electron energy distribution patterns for the two different approaches, because photon emission is no longer well approximated by a continuous process in the quantum radiation-dominated regime. The stochastic nature of photon emission results in strong signatures of quantum radiation-reaction effects under certain conditions. We show that the laser spot size and duration greatly influence these signatures due to the competition of QED effects and the ponderomotive force, which is well described in the classical approximation. The clearest signatures of quantum radiation reaction are found in the limit of large laser spots and few cycle pulse durations.

  17. Method and apparatus for producing laser radiation following two-photon excitation of a gaseous medium

    DOEpatents

    Bischel, W.K.; Jacobs, R.R.; Prosnitz, D.P.; Rhodes, C.K.; Kelly, P.J.

    1979-02-20

    Method and apparatus are disclosed for producing laser radiation by two-photon optical pumping of an atomic or molecular gaseous medium and subsequent lasing action. A population inversion is created as a result of two-photon absorption of the gaseous species. Stark tuning is utilized, if necessary, in order to tune the two-photon transition into exact resonance. In particular, gaseous ammonia (NH[sub 3]) or methyl fluoride (CH[sub 3]F) is optically pumped by a pair of CO[sub 2] lasers to create a population inversion resulting from simultaneous two-photon excitation of a high-lying vibrational state, and laser radiation is produced by stimulated emission of coherent radiation from the inverted level. 3 figs.

  18. Method and apparatus for producing laser radiation following two-photon excitation of a gaseous medium

    DOEpatents

    Bischel, William K. [Menlo Park, CA; Jacobs, Ralph R. [Livermore, CA; Prosnitz, Donald [Hamden, CT; Rhodes, Charles K. [Palo Alto, CA; Kelly, Patrick J. [Fort Lewis, WA

    1979-02-20

    Method and apparatus for producing laser radiation by two-photon optical pumping of an atomic or molecular gaseous medium and subsequent lasing action. A population inversion is created as a result of two-photon absorption of the gaseous species. Stark tuning is utilized, if necessary, in order to tune the two-photon transition into exact resonance. In particular, gaseous ammonia (NH.sub.3) or methyl fluoride (CH.sub.3 F) is optically pumped by a pair of CO.sub.2 lasers to create a population inversion resulting from simultaneous two-photon excitation of a high-lying vibrational state, and laser radiation is produced by stimulated emission of coherent radiation from the inverted level.

  19. Highly efficient terahertz radiation from a thin foil irradiated by a high-contrast laser pulse

    NASA Astrophysics Data System (ADS)

    Jin, Z.; Zhuo, H. B.; Nakazawa, T.; Shin, J. H.; Wakamatsu, S.; Yugami, N.; Hosokai, T.; Zou, D. B.; Yu, M. Y.; Sheng, Z. M.; Kodama, R.

    2016-09-01

    Radially polarized intense terahertz (THz) radiation behind a thin foil irradiated by ultrahigh-contrast ultrashort relativistic laser pulse is recorded by a single-shot THz time-domain spectroscopy system. As the thickness of the target is reduced from 30 to 2 µm, the duration of the THz emission increases from 5 to over 20 ps and the radiation energy increases dramatically, reaching ˜10.5 mJ per pulse, corresponding to a laser-to-THz radiation energy conversion efficiency of 1.7 % . The efficient THz emission can be attributed to reflection (deceleration and acceleration) of the laser-driven hot electrons by the target-rear sheath electric field. The experimental results are consistent with that of a simple model as well as particle-in-cell simulation.

  20. Terahertz radiation from a laser bunched relativistic electron beam in a magnetic wiggler

    SciTech Connect

    Kumar, Manoj; Tripathi, V. K.

    2012-07-15

    We develop a formalism for tunable coherent terahertz radiation generation from a relativistic electron beam, modulated by two laser beams, as it passes through a magnetic wiggler of wave vector k{sub w}z-caret. The lasers exert a beat frequency ponderomotive force on beam electrons, and modulate their velocity. In the drift space, velocity modulation translates into density modulation. As the beam bunches pass through the wiggler, they acquire a transverse velocity, constituting a transverse current that acts as an antenna to produce coherent THz radiation, when {omega}{sub 1}-{omega}{sub 2}=k{sub w}c/(cos{theta}-v{sub 0b}/c), where {omega}{sub 1}, {omega}{sub 2} are the frequencies of the lasers, v{sub 0b}z-caret is the beam velocity, and {theta} is the direction of maximum radiated intensity with respect to the direction of propagation of the beam.

  1. EFFECTS OF LASER RADIATION ON MATTER: Role of the external photoelectric effect in surface microprocessing

    NASA Astrophysics Data System (ADS)

    Ageev, Vladimir P.; Konov, Vitalii I.; Krechetov, A. I.

    1990-08-01

    An analysis is made of the photoemission of electrons in gases when the surface of a solid is subjected to high-intensity ultraviolet laser radiation which does not cause surface heating. Various situations are considered in which generation of high local electric fields and of a dense cloud of charged particles near the surface may alter and even determine the mechanism of laser-stimulated processes on surfaces of solids.

  2. Laser targeting with C-arm fluoroscopy: effect on radiation exposure for pediatric patients.

    PubMed

    Schenk, Kellie; Johnston, Lynne

    2014-01-01

    The primary purpose of obtaining laser targeting devices for C-arm fluoroscopy was to attempt to reduce radiation to the pediatric population in Connecticut Children's Medical Center's commitment to Imaging Gently. Fluoroscopy times for placing central lines in the operating rooms were documented for two months prior to the installation of the lasers and then for twenty procedures after installation and training on the devices. Fluoroscopy times trended down 25% calculated by a simple mean and standard deviation.

  3. The effect of near-infrared MLS laser radiation on cell membrane structure and radical generation.

    PubMed

    Kujawa, Jolanta; Pasternak, Kamila; Zavodnik, Ilya; Irzmański, Robert; Wróbel, Dominika; Bryszewska, Maria

    2014-09-01

    The therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the biochemical mechanism of the interaction of laser light with living cells is not fully understood. We have investigated the effect of MLS (Multiwave Locked System) laser near-infrared irradiation on cell membrane structure, functional properties, and free radical generation using human red blood cells and breast cancer MCF-4 cells. The cells were irradiated with low-intensity MLS near-infrared (simultaneously 808 nm, continuous emission and 905 nm, pulse emission, pulse-wave frequency, 1,000 or 2,000 Hz) laser light at light doses from 0 to 15 J (average power density 212.5 mW/cm(2), spot size was 3.18 cm(2)) at 22 °C, the activity membrane bound acetylcholinesterase, cell stability, anti-oxidative activity, and free radical generation were the parameters used in characterizing the structural and functional changes of the cell. Near-infrared low-intensity laser radiation changed the acetylcholinesterase activity of the red blood cell membrane in a dose-dependent manner: There was a considerable increase of maximal enzymatic rate and Michaelis constant due to changes in the membrane structure. Integral parameters such as erythrocyte stability, membrane lipid peroxidation, or methemoglobin levels remained unchanged. Anti-oxidative capacity of the red blood cells increased after MLS laser irradiation. This irradiation induced a time-dependent increase in free radical generation in MCF-4 cells. Low-intensity near-infrared MLS laser radiation induces free radical generation and changes enzymatic and anti-oxidative activities of cellular components. Free radical generation may be the mechanism of the biomodulative effect of laser radiation.

  4. He-Ne laser radiation in combined therapy of children's bronchial asthma

    NASA Astrophysics Data System (ADS)

    Zhilnikov, Dmitriy V.; Varavva, Andrey S.; Tarasova, Olga N.; Plaksina, Galina V.; Barybin, Vitaliy F.; Khlutkova, Svetlana N.

    2004-02-01

    In this paper the medical application of He-Ne lasers for the treatment of bronchial asthma is described. Research objective of this work was the development of a treatment method for children with bronchial asthman of heavy and medium-heavy forms, resistant to the base therapy, with the help of low-intensive laser radiation with wave length λ=0,63 μm.

  5. Nano-cones Formed on a Surface of Semiconductors by Laser Radiation: Technology, Model and Properties

    NASA Astrophysics Data System (ADS)

    Medvid', A.; Onufrijevs, P.

    2011-12-01

    The new laser method for nanostructures formation on a surface of semiconductors Si, Ge, GaAs and SiGe, CdZnTe solid solutions is proposed. For the first time was shown the possibility of graded band gap structure formation in elementary semiconductors. Thermogradient effect has a main role in initial stage of nano-cones and graded band gap structure formation by laser radiation in semiconductors.

  6. Effect of laser radiation on living systems: Role of light coherence

    NASA Astrophysics Data System (ADS)

    Ulyanov, S. S.; Ulianova, O. V.

    2010-08-01

    The influence of spatial and temporal coherence, as well as speckle dynamics, on animal organisms is studied in detail. Our theoretical and experimental studies reveal no biophysical evidence of the influence of light coherence on living systems at any level, as well as no specific effects caused by laser radiation. The effects of laser therapy used for treatment of a wide range of diseases of humans require further detailed investigation and possibly a revision of the existing concept.

  7. Interaction of laser radiation with a low-density structured absorber

    NASA Astrophysics Data System (ADS)

    Rozanov, V. B.; Barishpol'tsev, D. V.; Vergunova, G. A.; Demchenko, N. N.; Ivanov, E. M.; Aristova, E. N.; Zmitrenko, N. V.; Limpouch, I.; Ulschmidt, I.

    2016-02-01

    A theoretical model is proposed for computing simulations of laser radiation interaction with inhomogeneous foam materials doped with heavy elements and undoped materials. The model satisfactorily describes many experiments on the interaction of the first and third harmonics of a 200 J pulsed PALS iodine laser with low-density porous cellulose triacetate targets. The model can be used to analyze experimental data and estimate the reality of experimental results.

  8. The absorption and radiation of a tungsten plasma plume during nanosecond laser ablation

    SciTech Connect

    Moscicki, T. Hoffman, J.; Chrzanowska, J.

    2015-10-15

    In this paper, the effect of absorption of the laser beam and subsequent radiation on the dynamics of a tungsten plasma plume during pulsed laser ablation is analyzed. Different laser wavelengths are taken into consideration. The absorption and emission coefficients of tungsten plasma in a pressure range of 0.1–100 MPa and temperature up to 70 000 K are presented. The shielding effects due to the absorption and radiation of plasma may have an impact on the course of ablation. The numerical model that describes the tungsten target heating and the formation of the plasma and its expansion were made for 355 nm and 1064 nm wavelengths of a Nd:YAG laser. The laser beam with a Gaussian profile was focused to a spot size of 0.055 mm{sup 2} with a power density of 1 × 10{sup 9 }W/cm{sup 2} (10 ns full width half maximum pulse duration). The plasma expands into air at ambient pressure of 1 mPa. The use of the shorter wavelength causes faster heating of the target, thus the higher ablation rate. The consequences of a higher ablation rate are slower expansion and smaller dimensions of the plasma plume. The higher plasma temperature in the case of 1064 nm is due to the lower density and lower plasma radiation. In the initial phase of propagation of the plasma plume, when both the temperature and pressure are very high, the dominant radiation is emission due to photo-recombination. However, for a 1064 nm laser wavelength after 100 ns of plasma expansion, the radiation of the spectral lines is up to 46.5% of the total plasma radiation and should not be neglected.

  9. Observation of Low-Frequency Electromagnetic Radiation from Laser-Plasmas

    NASA Astrophysics Data System (ADS)

    Kando, Masaki; Kawase, Keigo; Daito, Izuru; Pirozhkov, Alexander S.; Esirkepov, Timur Zh.; Fukuda, Yuji; Kotaki, Hideyuki; Kameshima, Takashi; Faenov, Anatoly Ya.; Pikuz, Tatiana A.; Bulanov, Sergei V.

    2009-07-01

    When an intense short laser pulse interacts with plasmas, the nonlinear interaction causes various phenomena such as high energy particle generation, strong radiation in the x-ray to THz frequency range. Formation of solitons is one of these interesting topics and has been studied mainly from theoretical aspects. Solitons are formed in an underdense plasma in the process of the laser pulse frequency downshift. They store a portion of the EM wave energy with the polarization inherited from the laser pulse-driver and emit it at the plasma-vacuum interface in the form of low frequency EM bursts. Solitons were observed experimentally by proton-beam imaging and in the visible-near-infrared emissions from the plasma. A low frequency EM radiation emission has also been observed in our experiments. The interpretation invokes the relativistic electromagnetic solitons. We present the results of the polarization-resolved measurements of low frequency radiation from the plasma region irradiated by the intense laser pulse. A dominant component of the observed THz radiation has the same polarization as the driver laser pulse.

  10. Influence of MLS laser radiation on erythrocyte membrane fluidity and secondary structure of human serum albumin.

    PubMed

    Pasternak, Kamila; Nowacka, Olga; Wróbel, Dominika; Pieszyński, Ireneusz; Bryszewska, Maria; Kujawa, Jolanta

    2014-03-01

    The biostimulating activity of low level laser radiation of various wavelengths and energy doses is widely documented in the literature, but the mechanisms of the intracellular reactions involved are not precisely known. The aim of this paper is to evaluate the influence of low level laser radiation from an multiwave locked system (MLS) of two wavelengths (wavelength = 808 nm in continuous emission and 905 nm in pulsed emission) on the human erythrocyte membrane and on the secondary structure of human serum albumin (HSA). Human erythrocytes membranes and HSA were irradiated with laser light of low intensity with surface energy density ranging from 0.46 to 4.9 J cm(-2) and surface energy power density 195 mW cm(-2) (1,000 Hz) and 230 mW cm(-2) (2,000 Hz). Structural and functional changes in the erythrocyte membrane were characterized by its fluidity, while changes in the protein were monitored by its secondary structure. Dose-dependent changes in erythrocyte membrane fluidity were induced by near-infrared laser radiation. Slight changes in the secondary structure of HSA were also noted. MLS laser radiation influences the structure and function of the human erythrocyte membrane resulting in a change in fluidity.

  11. Stereological study of the capillaries in the thyroid gland after IR laser radiation

    NASA Astrophysics Data System (ADS)

    Perez de Vargas, I.; Vidal, Lourdes; Parrado, C.; Carrillo, F.; Pelaez, A.; Rius, F.

    1994-02-01

    We have planned a stereological ultrastructural study of capillaries in the thyroid gland treated with IR laser radiation and quantified 1 day after the last treatment. Wistar rats, 50 days old, were irradiated with IR laser radiation. The rats were perfused with 2.5 percent glutaraldehyde in 0.1 M phosphate buffer (ph equals 7.4). The pieces obtained after sectioning the thyroid gland were placed immediately into the same fixative. A stereological study of the thyroid capillaries was carried out. This analysis revealed an increase of luminal area in irradiated capillaries.

  12. Exposure to laser radiation for creation of metal materials nanoporous structures

    NASA Astrophysics Data System (ADS)

    Murzin, Serguei P.

    2013-06-01

    Exposure to laser radiation for creation of nanoporous structures in the Cu-Zn alloy was investigated. It was established that exposure to laser pulse-periodic radiation with pulse repetition rate up to 5000 Hz makes it possible to form a nanoporous structure in the near-surface layer. The conditions of increase of area depth of such structures formation up to 40-45 μm were ascertained. The temperature and speed conditions which provide predominant channel-type nanopores formation with width of about 100 nm forming a nanoporous net were determined. This patented technology is a perspective for production of catalysts and microfiltration membranes.

  13. Assessment and Mitigation of Radiation, EMP, Debris & Shrapnel Impacts at Megajoule-Class Laser Facilities

    SciTech Connect

    Eder, D C; Anderson, R W; Bailey, D S; Bell, P; Benson, D J; Bertozzi, A L; Bittle, W; Bradley, D; Brown, C G; Clancy, T J; Chen, H; Chevalier, J M; Combis, P; Dauffy, L; Debonnel, C S; Eckart, M J; Fisher, A C; Geille, A; Glebov, V Y; Holder, J; Jadaud, J P; Jones, O; Kaiser, T B; Kalantar, D; Khater, H; Kimbrough, J; Koniges, A E; Landen, O L; MacGowan, B J; Masters, N D; MacPhee, A; Maddox, B R; Meyers, M; Osher, S; Prasad, R; Raffestin, D; Raimbourg, J; Rekow, V; Sangster, C; Song, P; Stoeckl, C; Stowell, M L; Teran, J M; Throop, A; Tommasini, R; Vierne, J; White, D; Whitman, P

    2009-10-05

    The generation of neutron/gamma radiation, electromagnetic pulses (EMP), debris and shrapnel at mega-Joule class laser facilities (NIF and LMJ) impacts experiments conducted at these facilities. The complex 3D numerical codes used to assess these impacts range from an established code that required minor modifications (MCNP - calculates neutron and gamma radiation levels in complex geometries), through a code that required significant modifications to treat new phenomena (EMSolve - calculates EMP from electrons escaping from laser targets), to a new code, ALE-AMR, that is being developed through a joint collaboration between LLNL, CEA, and UC (UCSD, UCLA, and LBL) for debris and shrapnel modelling.

  14. High-order harmonic generation of picosecond radiation of moderate intensity in laser plasma

    SciTech Connect

    Boltaev, G S; Ganeev, Rashid A; Kulagin, I A; Satlikov, N Kh; Usmanov, T

    2012-10-31

    The results of investigations into the generation of highorder harmonics (up to the 21st order) of picosecond ({tau} = 38 ps) Nd : YAG laser radiation in the plasma produced by laser ablation of metal and carbon-containing material surfaces are presented. We demonstrate the feasibility of generating high-order harmonics in the vacuum ultraviolet spectral range (with radiation wavelengths shorter than 120 nm) in plasmas with an efficiency of {approx}0.7 Multiplication-Sign 10{sup -4}. In carbon-containing plasma, the 7th harmonic intensity exceeded that of the 5th one by a factor of seven. (nonlinear optical phenomena)

  15. High-order harmonic generation of picosecond radiation of moderate intensity in laser plasma

    NASA Astrophysics Data System (ADS)

    Boltaev, G. S.; Ganeev, Rashid A.; Kulagin, I. A.; Satlikov, N. Kh; Usmanov, T.

    2012-10-01

    The results of investigations into the generation of highorder harmonics (up to the 21st order) of picosecond (τ = 38 ps) Nd : YAG laser radiation in the plasma produced by laser ablation of metal and carbon-containing material surfaces are presented. We demonstrate the feasibility of generating high-order harmonics in the vacuum ultraviolet spectral range (with radiation wavelengths shorter than 120 nm) in plasmas with an efficiency of ~0.7 × 10-4. In carbon-containing plasma, the 7th harmonic intensity exceeded that of the 5th one by a factor of seven.

  16. Temporal Characterization of Femtosecond Laser-Plasma-AcceleratedElectron Bunches using THz Radiation

    SciTech Connect

    van Tilborg, J.; Schroeder, C.B.; Filip, C.V.; Toth, Cs.; Geddes,C.G.R.; Fubiani, G.; Huber, R.; Kaindl, R.A.; Esarey, E.; Leemans, W.P.

    2005-07-12

    The temporal pro le of relativistic laser-plasma-acceleratedelectron bunches has been characterized. Coherent transition radiation atTHz frequencies, emitted at the plasma-vacuum boundary, is measuredthrough electro-optic sampling. The data indicates that THz radiation isemitted by a skewed bunch with a sub-50 fs rise time and a ~; 600 fs tail(half-width-at-half-maximum), consistent with ballistic debunching of 100percent-energy-spread beams. The measurement demonstrates bothshot-to-shot stability of the laser-plasma accelerator and femtosecondsynchronization between bunch and probe beam.

  17. Experiment and modeling: Ignition of aluminum particles with a carbon dioxide laser

    NASA Astrophysics Data System (ADS)

    Mohan, Salil

    Aluminum is a promising ingredient for high energy density compositions used in propulsion systems, explosives, and pyrotechnics. Aluminum powder fuel additives enable one to achieve higher combustion enthalpies and reaction temperatures. Therefore, to develop aluminum based novel and customized high density energetic materials, understanding of ignition and combustion kinetics of aluminum powders is required. In most practical systems, metal ignition and combustion occur in environments with rapidly changing temperatures and gas compositions. The kinetics of exothermic reactions in related energetic materials is commonly characterized by thermal analysis, where the heating rates are very low, on the order of 1--50 K/min. The extrapolation of the identified kinetics to the high heating rates is difficult and requires direct experimental verification. This difficulty led to development of new experimental approaches to directly characterize ignition kinetics for the heating rates in the range of 103--104 K/s. However, the practically interesting heating rates of 106 K/s range have not been achieved. This work is directed at development of an experimental technique and respective heat transfer model for studying ignition of aluminum and other micron-sized metallic particles at heating rates varied around 106 K/s. The experimental setup uses a focused CO2 laser as a heating source and a plate capacitor aerosolizer to feed the aluminum particles into the laser beam. The setup allows using different environment for particle aerosolization. The velocities of particles in the jet are in the range of 0.1 --0 3 m/s. For each selected jet velocity, the laser power is increased until the particles are observed to ignite. The ignition is detected optically using a digital camera and a photomultiplier. The ignition thresholds for spherical aluminum powder were measured at three different particle jet velocities, in air environment. A single particle heat transfer model was

  18. Flexible Fiber Optic Carbon-Dioxide Laser Assisted Stapedotomy in Otosclerosis

    PubMed Central

    2016-01-01

    Objective. The aim of this study is to analyze the hearing and vestibular outcome of patients with otosclerosis who have been operated on by fiber optic flexible CO2 laser. Study Design. A preliminary and retrospective study was conducted in 30 patients with otosclerosis. Results. Comparative analysis of average air conduction thresholds (53.41 ± 11.81 dB versus 26.37 ± 11.04 dB) and air-bone gaps (34 ± 9.92 dB versus 12.03 ± 6.02 dB) before and after the surgery were statistically significant (<0.001). Air-bone gap closed within 10 dB or less in 50% of the cases and within 20 dB or less in 90% of the cases. Average bone conduction threshold after the surgery (16.68 ± 12.00 dB) was better than that before the surgery (20.13 ± 8.59). However, no statistically significant difference was found (p = 0.213). One patient had tinnitus after surgery. None of the patients had severe sickness or vomiting due to surgery. Eleven patients (36.6%) had very mild nystagmus beating toward the counter-lateral side. All patients were stable at 10 days after surgery. Conclusion. The results indicate that fiber optic flexible CO2 laser provides the surgeon with a very safe and precise surgical instrumentation even in cases with extensive and obliterative otosclerosis. PMID:27725835

  19. Simultaneous Measurements of Leaf and Soil Carbon Dioxide Flux Using a Tunable Diode Laser

    NASA Astrophysics Data System (ADS)

    Hunt, J. E.; Barbour, M. M.

    2007-12-01

    A portable photosynthesis system (Li-6400, Li-Cor, NE) and a through-flow soil chamber were used to continuously measure the gas exchange of leaf and below ground components in pots containing corn, Triticale and a non-planted control. Temperature was kept constant through-out the experiment, and measurements were made at 4 min intervals over a full diurnal light cycle. A tunable diode laser (TGA100A, Campbell Scientific, UT) was used to measure the concentration and stable isotopic composition (δ13C and δ18O) of the air entering and exiting both chambers. End-member isotope values were determined by short-term incubation of component parts in Tedlar bags, and the evolved gas was measured with the laser. These data were used to determine the isotopic signature of CO2 derived from root respiration, microbial respiration of plant derived exudates and soil organic matter (SOM) to allow the partitioning of the total flux into component parts. The δ13C of SOM respiration was identical when measured with the soil chamber on the control pots and when using incubated samples from the same pots. However, incubation of the potting mix in the other treatments was more enriched (corn) and more depleted (Triticale) than the control, indicating that end-member determination of the original SOM was confounded by exudates from the plants. Using a mixing model to partition the soil respiration, and the δ13C of SOM from the control pots, corn roots contributed 25% and Triticale 72% of the below-ground respiration. Incubation of soil with the roots removed allowed non-root respiration to be partitioned into contributions from pre-existing SOM and more recent plant derived exudates for corn (23% recent carbon) and Triticale (36% recent carbon).

  20. On the structure of quasi-stationary laser ablation fronts in strongly radiating plasmas

    SciTech Connect

    Basko, M. M. Novikov, V. G.; Grushin, A. S.

    2015-05-15

    The effect of strong thermal radiation on the structure of quasi-stationary laser ablation fronts is investigated under the assumption that all the laser flux is absorbed at the critical surface. Special attention is paid to adequate formulation of the boundary-value problem for a steady-state planar ablation flow. The dependence of the laser-to-x-ray conversion efficiency ϕ{sub r} on the laser intensity I{sub L} and wavelength λ{sub L} is analyzed within the non-equilibrium diffusion approximation for radiation transfer. The scaling of the main ablation parameters with I{sub L} and λ{sub L} in the strongly radiative regime 1−ϕ{sub r}≪1 is derived. It is demonstrated that strongly radiating ablation fronts develop a characteristic extended cushion of “radiation-soaked” plasma between the condensed ablated material and the critical surface, which can efficiently suppress perturbations from the instabilities at the critical surface.

  1. Ablation and transmission of thin solid targets irradiated by intense extreme ultraviolet laser radiation

    NASA Astrophysics Data System (ADS)

    Aslanyan, V.; Kuznetsov, I.; Bravo, H.; Woolston, M. R.; Rossall, A. K.; Menoni, C. S.; Rocca, J. J.; Tallents, G. J.

    2016-09-01

    The interaction of an extreme ultraviolet (EUV) laser beam with a parylene foil was studied by experiments and simulation. A single EUV laser pulse of nanosecond duration focused to an intensity of 3 × 1010 W cm-2 perforated micrometer thick targets. The same laser pulse was simultaneously used to diagnose the interaction by a transmission measurement. A combination of 2-dimensional radiation-hydrodynamic and diffraction calculations was used to model the ablation, leading to good agreement with experiment. This theoretical approach allows predictive modelling of the interaction with matter of intense EUV beams over a broad range of parameters.

  2. Microprocessing of human hard tooth tissues surface by mid-infrared erbium lasers radiation

    NASA Astrophysics Data System (ADS)

    Belikov, Andrey V.; Shatilova, Ksenia V.; Skrypnik, Alexei V.

    2015-03-01

    A new method of hard tooth tissues laser treatment is described. The method consists in formation of regular microdefects on tissue surface by mid-infrared erbium laser radiation with propagation ratio M2<2 (Er-laser microprocessing). Proposed method was used for preparation of hard tooth tissues surface before filling for improvement of bond strength between tissues surface and restorative materials, microleakage reduction between tissues surface and restorative materials, and for caries prevention as a result of increasing microhardness and acid resistance of tooth enamel.

  3. Shear bond strength after Er:YAG laser radiation conditioning of enamel and dentin

    NASA Astrophysics Data System (ADS)

    Dostalova, Tatjana; Jelinkova, Helena; Dolezalova, Libuse; Kubelka, Jiri; Prochazka, Stanislav; Hamal, Karel; Krejsa, Otakar

    1997-12-01

    This study compares bond shear strength between hard dental tissues and composite resin filling material after a classical acid etching treatment procedure and Er:YAG laser surface conditioning. The retention of composite resin was evaluated for three cases: (1) the flat dental substrate without any conditioning, (2) the classical drilling machine prepared surface with acid etching and (3) the Er:YAG laser conditioning of enamel and dentin. None significant differences between bond shear strength of the classical drilling machine prepared surface with acid etching in comparison with the laser radiation conditioning were found.

  4. Influence of laser radiation on the growth and development of seeds of agricultural plants

    NASA Astrophysics Data System (ADS)

    Grishkanich, Alexander; Zhevlakov, Alexander; Polyakov, Vadim; Kascheev, Sergey; Sidorov, Igor; Ruzankina, Julia; Yakovlev, Alexey; Mak, Andrey

    2016-04-01

    The experimental results presented in this study focused on the study of biological processes caused by exposure to the coating layers of the laser green light seed (λ = 532 nm) range for the larch, violet (λ = 405 nm) and red (λ = 640 nm) for spruce. Spend a series of experiments to study the dependence of crop seed quality (spruce and larch from the pine family) from exposure to laser radiation under different conditions. In all the analyzed groups studied seed germination and growth of seedlings exposed to laser exposure, compared with the control group. The results showed that the higher percentage of germination than seeds of the control group.

  5. 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.

  6. Radiation-Pressure Acceleration of Ion Beams Driven by Circularly Polarized Laser Pulses

    SciTech Connect

    Henig, A.; Hoerlein, R.; Kiefer, D.; Jung, D.; Habs, D.; Steinke, S.; Schnuerer, M.; Sokollik, T.; Nickles, P. V.; Sandner, W.; Schreiber, J.; Hegelich, B. M.; Yan, X. Q.; Meyer-ter-Vehn, J.; Tajima, T.

    2009-12-11

    We present experimental studies on ion acceleration from ultrathin diamondlike carbon foils irradiated by ultrahigh contrast laser pulses of energy 0.7 J focused to peak intensities of 5x10{sup 19} W/cm{sup 2}. A reduction in electron heating is observed when the laser polarization is changed from linear to circular, leading to a pronounced peak in the fully ionized carbon spectrum at the optimum foil thickness of 5.3 nm. Two-dimensional particle-in-cell simulations reveal that those C{sup 6+} ions are for the first time dominantly accelerated in a phase-stable way by the laser radiation pressure.

  7. Electron heating in radiation-pressure-driven proton acceleration with a circularly polarized laser

    NASA Astrophysics Data System (ADS)

    Paradkar, B. S.; Krishnagopal, S.

    2016-02-01

    Dynamics of electron heating in the radiation-pressure-driven acceleration through self-induced transparency (SIT) is investigated with the help of particle-in-cell simulations. The SIT is achieved through laser filamentation which is seeded by the transverse density modulations due to the Rayleigh-Taylor-like instability. We observe stronger SIT induced electron heating for the longer duration laser pulses leading to deterioration of accelerated ion beam quality (mainly energy spread). Such heating can be controlled to obtain a quasimonoenergetic beam by cascaded foils targets where a second foil behind the main accelerating foil acts as a laser reflector to suppress the SIT.

  8. An efficient computational approach for evaluating radiation flux for laser driven inertial confinement fusion targets

    NASA Astrophysics Data System (ADS)

    Li, Haiyan; Huang, Yunbao; Jiang, Shaoen; Jing, Longfei; Ding, Yongkun

    2015-08-01

    Radiation flux computation on the target is very important for laser driven Inertial Confinement Fusion, and view-factor based equation models (MacFarlane, 2003; Srivastava et al., 2000) are often used to compute this radiation flux on the capsule or samples inside the hohlraum. However, the equation models do not lead to sparse matrices and may involve an intensive solution process when discrete mesh elements become smaller and the number of equations increases. An efficient approach for the computation of radiation flux is proposed in this paper, in which, (1) symmetric and positive definite properties are achieved by transformation, and (2) an efficient Cholesky factorization algorithm is applied to significantly accelerate such equations models solving process. Finally, two targets on a laser facility built in China are considered to validate the computing efficiency of present approach. The results show that the radiation flux computation can be accelerated by a factor of 2.

  9. Study of shockwave method for diagnosing the radiation fields of laser-driven gold hohlraums

    NASA Astrophysics Data System (ADS)

    Li, Yongsheng; Lan, Ke; Huo, Wenyi; Lai, Dongxian; Gao, Yaoming; Pei, Wenbing

    2013-11-01

    Besides the routinely used broad-band x-ray spectrometer (Dante or SXS), ablative shock-wave method is often used to diagnose the radiation fields of laser-driven Hohlraums. The x-ray ablation process of Aluminum and Titanium is studied numerically with a 1-D radiation hydrodynamic code RDMG [F. Tinggui et al., Chin. J. Comput. Phys. 16, 199 (1999)], based on which a new scaling relation of the equivalent radiation temperature with the ablative shock velocity in Aluminum plates is proposed, and a novel method is developed for determining simultaneously the radiation temperature and the M-band (2-4 keV) fraction in laser-driven gold Hohlraums.

  10. Effect of laser frequency on a collision-induced radiative process

    NASA Technical Reports Server (NTRS)

    Devries, P. L.; George, T. F.

    1981-01-01

    A review is presented of the principles of collision induced radiative processes, followed by an examination of the effects of laser frequencies on these processes. A one-dimensional problem involving two electron states is considered, and it is found that the Hamiltonian of the radiation field is dominated by electric-dipole interaction which couples states of different parity. Transitions are noted to be dependent on collisions, and the complexities of three-dimensional systems are expressed as considerations of the angular momentum of the photon, the necessity of treating different states simultaneously, and the fact that a radiation field destroys rotational invariance. Changing the radiation frequency alters the crossing point and offers opportunities to study the interplay of potential surfaces with molecular dynamics. Experiments on Na+A systems are outlined for several collision energies and various laser frequencies. Multiple crossings were obtained, although the total cross-section, at all energies, decreased at 18,350/cm.

  11. Dynamically controlled deposition of colloidal nanoparticle suspension in evaporating drops using laser radiation.

    PubMed

    Ta, V D; Carter, R M; Esenturk, E; Connaughton, C; Wasley, T J; Li, J; Kay, R W; Stringer, J; Smith, P J; Shephard, J D

    2016-05-18

    Dynamic control of the distribution of polystyrene suspended nanoparticles in evaporating droplets is investigated using a 2.9 μm high power laser. Under laser radiation a droplet is locally heated and fluid flows are induced that overcome the capillary flow, and thus a reversal of the coffee-stain effect is observed. Suspension particles are accumulated in a localised area, one order of magnitude smaller than the original droplet size. By scanning the laser beam over the droplet, particles can be deposited in an arbitrary pattern. This finding raises the possibility for direct laser writing of suspended particles through a liquid layer. Furthermore, a highly uniform coating is possible by manipulating the laser beam diameter and exposure time. The effect is expected to be universally applicable to aqueous solutions independent of solutes (either particles or molecules) and deposited substrates.

  12. Dynamically controlled deposition of colloidal nanoparticle suspension in evaporating drops using laser radiation.

    PubMed

    Ta, V D; Carter, R M; Esenturk, E; Connaughton, C; Wasley, T J; Li, J; Kay, R W; Stringer, J; Smith, P J; Shephard, J D

    2016-05-18

    Dynamic control of the distribution of polystyrene suspended nanoparticles in evaporating droplets is investigated using a 2.9 μm high power laser. Under laser radiation a droplet is locally heated and fluid flows are induced that overcome the capillary flow, and thus a reversal of the coffee-stain effect is observed. Suspension particles are accumulated in a localised area, one order of magnitude smaller than the original droplet size. By scanning the laser beam over the droplet, particles can be deposited in an arbitrary pattern. This finding raises the possibility for direct laser writing of suspended particles through a liquid layer. Furthermore, a highly uniform coating is possible by manipulating the laser beam diameter and exposure time. The effect is expected to be universally applicable to aqueous solutions independent of solutes (either particles or molecules) and deposited substrates. PMID:27094902

  13. Precision drilling of fused silica with 157-nm excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Temme, Thorsten; Ostendorf, Andreas; Kulik, Christian; Meyer, Klaus

    2003-07-01

    μFor drilling fused silica, mechanical techniques like with diamond drills, ultrasonic machining, sand blasting or water jet machining are used. Also chemical techniques like laser assisted wet etching or thermal drilling with CO2-lasers are established. As an extension of these technologies, the drilling of micro-holes in fused silica with VUV laser radiation is presented here. The high absorption of the 157 nm radiation emitted by the F2 excimer laser and the short pulse duration lead to a material ablation with minimised impact on the surrounding material. Contrary to CO2-laser drilling, a molten and solidified phase around the bore can thus be avoided. The high photon energy of 7.9 eV requires either high purity nitrogen flushing or operation in vacuum, which also effects the processing results. Depending on the required precision, the laser can be used for percussion drilling as well as for excimer laser trepanning, by applying rotating masks. Rotating masks are especially used for high aspect ratio drilling with well defined edges and minimised debris. The technology is suitable particularly for holes with a diameter below 200 μm down to some microns in substrates with less than 200 μm thickness, that can not be achieved with mechanical methods. Drilling times in 200 μm fused silica substrates are in the range of ten seconds, which is sufficient to compete with conventional methods while providing similar or even better accuracy.

  14. Propagation and absorption of high-intensity femtosecond laser radiation in diamond

    SciTech Connect

    Kononenko, V V; Konov, V I; Gololobov, V M; Zavedeev, E V

    2014-12-31

    Femtosecond interferometry has been used to experimentally study the photoexcitation of the electron subsystem of diamond exposed to femtosecond laser pulses of intensity 10{sup 11} to 10{sup 14} W cm{sup -2}. The carrier concentration has been determined as a function of incident intensity for three harmonics of a Ti : sapphire laser (800, 400 and 266 nm). The results demonstrate that, in a wide range of laser fluences (up to those resulting in surface and bulk graphitisation), a well-defined multiphoton absorption prevails. We have estimated nonlinear absorption coefficients for pulsed radiation at λ = 800 nm (four-photon transition) and at 400 and 266 nm (indirect and direct two-photon transitions, respectively). It has also been shown that, at any considerable path length of a femtosecond pulse in diamond (tens of microns or longer), the laser beam experiences a severe nonlinear transformation, determining the amount of energy absorbed by the lattice, which is important for the development of technology for diamond photostructuring by ultrashort pulses. The competition between wave packet self-focusing and the plasma defocusing effect is examined as a major mechanism governing the propagation of intense laser pulses in diamond. (interaction of laser radiation with matter. laser plasma)

  15. Radiation characteristics of a multimode linear Zeeman laser

    NASA Astrophysics Data System (ADS)

    Nikonchuk, M. O.; Pugach, I. P.

    An experimental study is presented of a 3.39-micron multimode linear He-Ne Zeeman laser in a longitudinal magnetic field. Conditions are achieved in which elliptically polarized longitudinal modes of the laser are locked by the modulation of resonator losses at the frequency of intermode beats; modulation is carried out using a germanium acoustooptic modulator. An analysis of the laser-emission spectrum is presented, and the frequency and polarization characteristics are investigated. Experimental data on locking and free-lasing regimes are compared, and the observed effects are explained. It is shown that the frequency splitting of modes with opposite signs of ellipticity (achieved by the superposition of a longitudinal magnetic field on the active medium) in the regime of longitudinal-mode locking is realized over the whole gain line of the active medium.

  16. Combination of erbium and holmium laser radiation for tissue ablation

    NASA Astrophysics Data System (ADS)

    Pratisto, Hans S.; Frenz, Martin; Koenz, Flurin; Altermatt, Hans J.; Weber, Heinz P.

    1996-05-01

    Erbium lasers emitting at 2.94 micrometers and holmium lasers emitting at 2.1 micrometers are interesting tools for cutting, drilling, smoothing and welding of water containing tissues. The high absorption coefficient of water at these wavelengths leads to their good ablation efficiency with controlled thermally altered zones around the ablation sites. Combination of pulses with both wavelengths transmitted through one fiber were used to perform incisions in soft tissue and impacts in bone disks. Histological results and scanning electron microscope evaluations reveal the strong influence of the absorption coefficient on tissue effects, especially on the ablation efficiency and the zone of thermally damaged tissue. It is demonstrated that the combination of high ablation rates and deep coagulation zones can be achieved. The results indicate that this laser system can be considered as a first step towards a multi-functional medical instrument.

  17. CRC handbook of laser science and technology. Volume 3. Optical materials, Part 1 - Nonlinear optical properties/radiation damage

    SciTech Connect

    Weber, M.J.

    1986-01-01

    This book examines the nonlinear optical properties of laser materials. The physical radiation effects on laser materials are also considered. Topics considered include: nonlinear optical properties; nonlinear and harmonic generation materials; two-photon absorption; nonlinear refractive index; stimulated Raman scattering; radiation damage; crystals; and glasses.

  18. Laser-driven beam lines for delivering intensity modulated radiation therapy with particle beams

    SciTech Connect

    Hofmann, K. M.; Schell, S.; Wilkens, J. J.

    2013-07-26

    Laser-accelerated particles can provide a promising opportunity for radiation therapy of cancer. Potential advantages arise from combining a compact, cost-efficient treatment unit with the physical advantages in dose delivery of charged particle beams. We consider different dose delivery schemes and the required devices to design a possible treatment unit. The secondary radiation produced in several beam line elements remains a challenge to be addressed.

  19. Evaluation of depth and profile cavity after laser ablation with different energy of Er:YAG laser radiation

    NASA Astrophysics Data System (ADS)

    Dostalova, Tatjana; Jelinkova, Helena; Hamal, Karel; Krejsa, Otakar; Kubelka, Jiri; Prochazka, Stanislav

    1996-01-01

    Depth and profile cavity were studied after laser ablation with different energy of Er:YAG laser beam. Longitudinal sections of extracted human teeth were cut and polished to the flat surfaces. The thickness of layer of prepared teeth was from 3 to 5 mm. The check group contained glazed samples of ivory with the similar thickness. The Er:YAG laser drilling machine was operating in a free-running mode. For the preparation we used the energy up to 500 mJ. The repetition rate was 1 or 2 Hz. The laser radiation was focused on the tooth surface using CaF2 lens (f equals 55 mm). During the experiment, teeth were steady and the radiation was delivered by the mechanical arm which was fixed in a special holder. The fine water mist (water - 50 ml/min with the pressure to atm, air-pressure three atm) was used. Samples with the flat surfaces from the enamel, dentin and ivory were irradiated with five different energies from 100 to 500 mJ. Quantities of one, five, ten, twenty and thirty pulses were used. The depth of cavity and its profile were observed and measured. It was found that depth of cavity depends on the value of energy, type of hard dental tissue and number of pulses. With increasing energy or number of pulses the saturation effect in depth of holes in dentine or enamel were proved.

  20. Solid-State 2-Micron Laser Transmitter Advancement for Wind and Carbon Dioxide Measurements From Ground, Airborne, and Space-Based Lidar Systems

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Kavaya, Michael J.; Koch, Grady; Yu, Jirong; Ismail, Syed

    2008-01-01

    NASA Langley Research Center has been developing 2-micron lidar technologies over a decade for wind measurements, utilizing coherent Doppler wind lidar technique and carbon dioxide measurements, utilizing Differential Absorption Lidar (DIAL) technique. Significant advancements have been made towards developing state-of-the-art technologies towards laser transmitters, detectors, and receiver systems. These efforts have led to the development of solid-state lasers with high pulse energy, tunablility, wavelength-stability, and double-pulsed operation. This paper will present a review of these technological developments along with examples of high resolution wind and high precision CO2 DIAL measurements in the atmosphere. Plans for the development of compact high power lasers for applications in airborne and future space platforms for wind and regional to global scale measurement of atmospheric CO2 will also be discussed.

  1. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Characteristics of the evolution of a plasma formed by cw and pulse-periodic CO2 laser radiation in various gases

    NASA Astrophysics Data System (ADS)

    Kanevskiĭ, M. F.; Stepanova, M. A.

    1990-06-01

    An investigation was made of the interaction between high-power cw and pulse-periodic CO2 laser radiation and a low-threshold optical breakdown plasma near a metal surface. Characteristics of the breakdown plasma were studied as a function of the experimental conditions. A qualitative analysis was made of the results using a simple one-dimensional model for laser combustion waves.

  2. [Hardening of dental tissue by CO2 laser radiation].

    PubMed

    Aboites, V; Díaz, O; Cuevas, F

    1989-03-01

    A study was conducted to test the effects of CO2 laser irradiation on dental tissue. It was found that hardening of the dental tissue occurs. This was observed qualitatively by direct observation and by X-ray radiography. The hardening produced was also quantitatively measured using a hardness-meter on Rockwell scale.

  3. Quantum radiation reaction in head-on laser-electron beam interaction

    NASA Astrophysics Data System (ADS)

    Vranic, Marija; Grismayer, Thomas; Fonseca, Ricardo A.; Silva, Luis O.

    2016-07-01

    In this paper, we investigate the evolution of the energy spread and the divergence of electron beams while they interact with different laser pulses at intensities where quantum effects and radiation reaction are of relevance. The interaction is modelled with a quantum electrodynamic (QED)-PIC code and the results are compared with those obtained using a standard PIC code with a classical radiation reaction module. In addition, an analytical model is presented that estimates the value of the final electron energy spread after the interaction with the laser has finished. While classical radiation reaction is a continuous process, in QED, radiation emission is stochastic. The two pictures reconcile in the limit when the emitted photons energy is small compared to the energy of the emitting electrons. The energy spread of the electron distribution function always tends to decrease with classical radiation reaction, whereas the stochastic QED emission can also enlarge it. These two tendencies compete in the QED-dominated regime. Our analysis, supported by the QED module, reveals an upper limit to the maximal attainable energy spread due to stochasticity that depends on laser intensity and the electron beam average energy. Beyond this limit, the energy spread decreases. These findings are verified for different laser pulse lengths ranging from short ∼30 fs pulses presently available to the long ∼150 fs pulses expected in the near-future laser facilities, and compared with a theoretical model. Our results also show that near future experiments will be able to probe this transition and to demonstrate the competition between enhanced QED induced energy spread and energy spectrum narrowing from classical radiation reaction.

  4. Facile synthesis of silicon carbide-titanium dioxide semiconducting nanocomposite using pulsed laser ablation technique and its performance in photovoltaic dye sensitized solar cell and photocatalytic water purification

    NASA Astrophysics Data System (ADS)

    Gondal, M. A.; Ilyas, A. M.; Baig, Umair

    2016-08-01

    Separation of photo-generated charge carriers (electron and holes) is a major approach to improve the photovoltaic and photocatalytic performance of metal oxide semiconductors. For harsh environment like high temperature applications, ceramic like silicon carbide is very prominent. In this work, 10%, 20% and 40% by weight of pre-oxidized silicon carbide was coupled with titanium dioxide (TiO2) to form nanocomposite semiconductor via elegant pulsed laser ablation in liquid technique using second harmonic 532 nm wavelength of neodymium-doped yttrium aluminium garnet (Nd-YAG) laser. In addition, the effect of silicon carbide concentration on the performance of silicon carbide-titanium dioxide nanocomposite as photo-anode in dye sensitized solar cell and as photocatalyst in photodegradation of methyl orange dye in water was also studied. The result obtained shows that photo-conversion efficiency of the dye sensitized solar cell was improved from 0.6% to 1.65% and the percentage of methyl orange dye removed was enhanced from 22% to 77% at 24 min under ultraviolet-visible solar spectrum in the nanocomposite with 10% weight of silicon carbide. This remarkable performance enhancement could be due to the improvement in electron transfer phenomenon by the presence of silicon carbide on titanium dioxide.

  5. 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.

  6. Effect of diode laser radiation in root canal wall dentine: a microbiological study

    NASA Astrophysics Data System (ADS)

    Gutknecht, Norbert; Conrads, Georg; Apel, Christian; Schubert, Claus; Lampert, Friedrich

    2000-03-01

    The aim of this study was to investigate the antibacterial effect of a diode laser in deep root canal dentine. The microbial colonization of root canal dentine can lead to failures in conventional endodontic treatment if only an inadequate bacterial reduction is achieved through canal treatment and chemical disinfection. 100 micrometer, 300 micrometer and 500 micrometer bovine dentine slices obtained by longitudinal sections were sterilized and inoculated on one side with an Enterococcus faecalis suspension. Laser radiation was performed on the opposite side with the diode laser, emits light at 810 nm and operates in the continuous wave mode (cw). Radiation was performed using a 400 micrometer tapered fiber tip at an angle of approx. 5 degrees to the surface over a period of 30 s. The output power at the distal end of the tip was 0.6 watt. The bacteria were then eluted through vibration and cultured on blood agar plates. The colony count reflected the antibacterial effect of laser radiation as a function of the layer thickness. A mean bacterial reduction of 74% was achieved even with a 500 micrometer thick slice. This investigation indicates that the diode laser can support the bacterial reduction in endodontic treatment.

  7. Radiation reaction in the interaction of ultraintense laser with matter and gamma ray source

    NASA Astrophysics Data System (ADS)

    Ong, J. F.; Teo, W. R.; Moritaka, Toseo; Takabe, H.

    2016-05-01

    Radiation reaction (RR) force plays an important role in gamma ray production in the interaction of ultraintense laser with relativistic counterpropagating electron at intensity 1022 W/cm2 and beyond. The relationship between emission spectrum and initial kinetic energy of electron at such intensities is yet to be clear experimentally. On the other hand, the energy from both the relativistic electron beam and laser pulse may be converted into the gamma rays. Therefore, the conversion efficiency of energy purely from laser pulse into gamma rays is of great interest. We present simulation results of an electron dynamics in strong laser field by taking into account the RR effects. We investigated how the RR effects influence the emission spectrum and photon number distribution for different laser condition. We showed that the peaks of emission spectra are suppressed if higher initial kinetic energy of electron interacts with long laser pulse duration. We then list the conversion efficiencies of laser pulse energy into gamma ray. We note that an electron with energy of 40 MeV would convert up to 80% of the total of electromagnetic work and initial kinetic energy of electron when interacting with 10 fs laser pulse at intensity 2 ×1023 W/cm2. For a bunch of electron with charge 1 nC would emit around 0.1 J of energy into gamma ray emission.

  8. [Endolacunar laser radiation of the tonsils in conservative treatment of chronic tonsillitis].

    PubMed

    Staroverova, T K; Shul'diakov, V A; Raĭgorodskiĭ, Iu M; Tatarenko, D A

    2007-01-01

    Vegetative and immune system indices, clinical symptoms of chronic tonsillitis exacerbation were compared in laser radiation of the tonsils with two methods - surface pharyngeal and endolacunar. The results show that under endolacunar method the symptoms regress 1.46 times faster, the number of late exacerbations decrease 1.5-2-fold.

  9. Numerical simulation of thermocapillary convection at surface modification by impulse laser radiation

    NASA Astrophysics Data System (ADS)

    Popov, V. N.; Kovalev, O. B.; Smirnova, E. M.

    2012-03-01

    Numerical simulation of metal surface alloying with impulse laser radiation has been performed. Impulse intensity influence on melt hydrodynamics and alloying substance distribution has been evaluated. For substance material, the authors used data on iron including dependence of surface tension on melt temperature and admixture concentration.

  10. Plane-wave-spectrum approach for calculations of radiation pattern of junction lasers

    SciTech Connect

    Sen, T.K.; Datta, A.K.; Basuray, A.

    1986-02-01

    An analytical expression for mode-conversion coefficients at a laser-air interface is derived using plane-wave decomposition of the modal fields. Both the mode-conversion coefficients and the radiation pattern are explicitly expressed as function of Fresnel reflection coefficients of the interface and the incident mode spectrum.

  11. Second harmonic generation of spectrally broadened femtosecond ytterbium laser radiation in a gas-filled capillary

    SciTech Connect

    Didenko, N V; Konyashchenko, Aleksandr V; Kostryukov, P V; Losev, Leonid L; Tenyakov, S Yu

    2011-09-30

    A 300-fs radiation pulse of an ytterbium laser with a wavelength of 1030 nm and energy of 150 {mu}J were converted to a 15-fs pulse with a wavelength of 515 nm by broadening the emission spectrum in a capillary filled with xenon and by generating the second harmonic in a KDP crystal. The energy efficiency of the conversion was 30 %.

  12. Annealing radiation damaged silicon solar cells with a copper halide laser

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.

    1980-01-01

    The use of a multiply pulsed copper halide laser to significantly anneal out the damage to silicon solar cells caused by a simulated space radiation environment is investigated. Preliminary experiments demonstrate that the amount of damage can be decreased by 41% as measured by the maximum power generated.

  13. Accounting for Transverse Inhomogeneity of Radiation Beams in Laser Raman Scattering

    NASA Astrophysics Data System (ADS)

    Apanasevich, P. A.; Dashkevich, V. I.; Timofeeva, G. I.

    2016-05-01

    A simple method of accounting for transverse inhomogeneity of the pump and Stokes radiation beams in the description of stimulated Raman scattering (SRS) using intensity-transfer equations for interacting beams is proposed. Features of the method are illustrated using the calculated dependences of the Raman laser efficiency on the output mirror reflectivity and the pump pulse energy as examples.

  14. Effects of radiation reaction in relativistic laser acceleration

    SciTech Connect

    Hadad, Y.; Labun, L.; Rafelski, J.; Elkina, N.; Klier, C.; Ruhl, H.

    2010-11-01

    The goal of this paper is twofold: to explore the response of classical charges to electromagnetic force at the level of unity in natural units and to establish a criterion that determines physical parameters for which the related radiation-reaction effects are detectable. In pursuit of this goal, the Landau-Lifshitz equation is solved analytically for an arbitrary (transverse) electromagnetic pulse. A comparative study of the radiation emission of an electron in a linearly polarized pulse for the Landau-Lifshitz equation and for the Lorentz force equation reveals the radiation-reaction-dominated regime, in which radiation-reaction effects overcome the influence of the external fields. The case of a relativistic electron that is slowed down by a counterpropagating electromagnetic wave is studied in detail. We further show that when the electron experiences acceleration of order unity, the dynamics of the Lorentz force equation, the Landau-Lifshitz equation and the Lorentz-Abraham-Dirac equation all result in different radiation emission that could be distinguished in experiment. Finally, our analytic and numerical results are compared with those appearing in the literature.

  15. Radiation damage in protein serial femtosecond crystallography using an x-ray free-electron laser

    PubMed Central

    Lomb, Lukas; Barends, Thomas R. M.; Kassemeyer, Stephan; Aquila, Andrew; Epp, Sascha W.; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Rudek, Benedikt; Rolles, Daniel; Rudenko, Artem; Shoeman, Robert L.; Andreasson, Jakob; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J.; Bostedt, Christoph; Bozek, John D.; Caleman, Carl; Coffee, Ryan; Coppola, Nicola; DePonte, Daniel P.; Doak, R. Bruce; Ekeberg, Tomas; Fleckenstein, Holger; Fromme, Petra; Gebhardt, Maike; Graafsma, Heinz; Gumprecht, Lars; Hampton, Christina Y.; Hartmann, Andreas; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Holton, James M.; Hunter, Mark S.; Kabsch, Wolfgang; Kimmel, Nils; Kirian, Richard A.; Liang, Mengning; Maia, Filipe R. N. C.; Meinhart, Anton; Marchesini, Stefano; Martin, Andrew V.; Nass, Karol; Reich, Christian; Schulz, Joachim; Seibert, M. Marvin; Sierra, Raymond; Soltau, Heike; Spence, John C. H.; Steinbrener, Jan; Stellato, Francesco; Stern, Stephan; Timneanu, Nicusor; Wang, Xiaoyu; Weidenspointner, Georg; Weierstall, Uwe; White, Thomas A.; Wunderer, Cornelia; Chapman, Henry N.; Ullrich, Joachim; Strüder, Lothar; Schlichting, Ilme

    2013-01-01

    X-ray free-electron lasers deliver intense femtosecond pulses that promise to yield high resolution diffraction data of nanocrystals before the destruction of the sample by radiation damage. Diffraction intensities of lysozyme nanocrystals collected at the Linac Coherent Light Source using 2 keV photons were used for structure determination by molecular replacement and analyzed for radiation damage as a function of pulse length and fluence. Signatures of radiation damage are observed for pulses as short as 70 fs. Parametric scaling used in conventional crystallography does not account for the observed effects. PMID:24089594

  16. Bidirectional reflection of polarized laser radiation by heat-insulating materials and thermoregulating coatings

    NASA Astrophysics Data System (ADS)

    Voshchula, I. V.; Dlugunovich, V. A.; Zhumar', A. Yu.; Tsaryuk, O. V.

    2012-03-01

    We have investigated the change in the degree of polarization of radiation reflected in the mirror direction by thermoregulating coatings (white, black, and silver paints) sprayed on aluminum, as well as by polymeric composite materials (phenol plastic painted green and bare carbon-filled plastic) illuminated at various angles by linearly polarized radiation from a He-Ne laser. Angular dependences of the bidirectional regular reflectance of the surface of the investigated materials taking into account only the polarized component of reflected radiation have been obtained.

  17. Tunable radiation source by coupling laser-plasma-generated electrons to a periodic structure.

    PubMed

    Jin, Z; Chen, Z L; Zhuo, H B; Kon, A; Nakatsutsumi, M; Wang, H B; Zhang, B H; Gu, Y Q; Wu, Y C; Zhu, B; Wang, L; Yu, M Y; Sheng, Z M; Kodama, R

    2011-12-23

    Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV/m field strength can be achieved by using appropriate grating parameters. PMID:22243162

  18. Radiation damage in protein serial femtosecond crystallography using an x-ray free-electron laser.

    PubMed

    Lomb, Lukas; Barends, Thomas R M; Kassemeyer, Stephan; Aquila, Andrew; Epp, Sascha W; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Rudek, Benedikt; Rolles, Daniel; Rudenko, Artem; Shoeman, Robert L; Andreasson, Jakob; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J; Bostedt, Christoph; Bozek, John D; Caleman, Carl; Coffee, Ryan; Coppola, Nicola; Deponte, Daniel P; Doak, R Bruce; Ekeberg, Tomas; Fleckenstein, Holger; Fromme, Petra; Gebhardt, Maike; Graafsma, Heinz; Gumprecht, Lars; Hampton, Christina Y; Hartmann, Andreas; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Holton, James M; Hunter, Mark S; Kabsch, Wolfgang; Kimmel, Nils; Kirian, Richard A; Liang, Mengning; Maia, Filipe R N C; Meinhart, Anton; Marchesini, Stefano; Martin, Andrew V; Nass, Karol; Reich, Christian; Schulz, Joachim; Seibert, M Marvin; Sierra, Raymond; Soltau, Heike; Spence, John C H; Steinbrener, Jan; Stellato, Francesco; Stern, Stephan; Timneanu, Nicusor; Wang, Xiaoyu; Weidenspointner, Georg; Weierstall, Uwe; White, Thomas A; Wunderer, Cornelia; Chapman, Henry N; Ullrich, Joachim; Strüder, Lothar; Schlichting, Ilme

    2011-12-01

    X-ray free-electron lasers deliver intense femtosecond pulses that promise to yield high resolution diffraction data of nanocrystals before the destruction of the sample by radiation damage. Diffraction intensities of lysozyme nanocrystals collected at the Linac Coherent Light Source using 2 keV photons were used for structure determination by molecular replacement and analyzed for radiation damage as a function of pulse length and fluence. Signatures of radiation damage are observed for pulses as short as 70 fs. Parametric scaling used in conventional crystallography does not account for the observed effects.

  19. Radiation damage in protein serial femtosecond crystallography using an x-ray free-electron laser

    NASA Astrophysics Data System (ADS)

    Lomb, Lukas; Barends, Thomas R. M.; Kassemeyer, Stephan; Aquila, Andrew; Epp, Sascha W.; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Rudek, Benedikt; Rolles, Daniel; Rudenko, Artem; Shoeman, Robert L.; Andreasson, Jakob; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J.; Bostedt, Christoph; Bozek, John D.; Caleman, Carl; Coffee, Ryan; Coppola, Nicola; Deponte, Daniel P.; Doak, R. Bruce; Ekeberg, Tomas; Fleckenstein, Holger; Fromme, Petra; Gebhardt, Maike; Graafsma, Heinz; Gumprecht, Lars; Hampton, Christina Y.; Hartmann, Andreas; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Holton, James M.; Hunter, Mark S.; Kabsch, Wolfgang; Kimmel, Nils; Kirian, Richard A.; Liang, Mengning; Maia, Filipe R. N. C.; Meinhart, Anton; Marchesini, Stefano; Martin, Andrew V.; Nass, Karol; Reich, Christian; Schulz, Joachim; Seibert, M. Marvin; Sierra, Raymond; Soltau, Heike; Spence, John C. H.; Steinbrener, Jan; Stellato, Francesco; Stern, Stephan; Timneanu, Nicusor; Wang, Xiaoyu; Weidenspointner, Georg; Weierstall, Uwe; White, Thomas A.; Wunderer, Cornelia; Chapman, Henry N.; Ullrich, Joachim; Strüder, Lothar; Schlichting, Ilme

    2011-12-01

    X-ray free-electron lasers deliver intense femtosecond pulses that promise to yield high resolution diffraction data of nanocrystals before the destruction of the sample by radiation damage. Diffraction intensities of lysozyme nanocrystals collected at the Linac Coherent Light Source using 2 keV photons were used for structure determination by molecular replacement and analyzed for radiation damage as a function of pulse length and fluence. Signatures of radiation damage are observed for pulses as short as 70 fs. Parametric scaling used in conventional crystallography does not account for the observed effects.

  20. Radiation damage in protein serial femtosecond crystallography using an x-ray free-electron laser.

    PubMed

    Lomb, Lukas; Barends, Thomas R M; Kassemeyer, Stephan; Aquila, Andrew; Epp, Sascha W; Erk, Benjamin; Foucar, Lutz; Hartmann, Robert; Rudek, Benedikt; Rolles, Daniel; Rudenko, Artem; Shoeman, Robert L; Andreasson, Jakob; Bajt, Sasa; Barthelmess, Miriam; Barty, Anton; Bogan, Michael J; Bostedt, Christoph; Bozek, John D; Caleman, Carl; Coffee, Ryan; Coppola, Nicola; Deponte, Daniel P; Doak, R Bruce; Ekeberg, Tomas; Fleckenstein, Holger; Fromme, Petra; Gebhardt, Maike; Graafsma, Heinz; Gumprecht, Lars; Hampton, Christina Y; Hartmann, Andreas; Hauser, Günter; Hirsemann, Helmut; Holl, Peter; Holton, James M; Hunter, Mark S; Kabsch, Wolfgang; Kimmel, Nils; Kirian, Richard A; Liang, Mengning; Maia, Filipe R N C; Meinhart, Anton; Marchesini, Stefano; Martin, Andrew V; Nass, Karol; Reich, Christian; Schulz, Joachim; Seibert, M Marvin; Sierra, Raymond; Soltau, Heike; Spence, John C H; Steinbrener, Jan; Stellato, Francesco; Stern, Stephan; Timneanu, Nicusor; Wang, Xiaoyu; Weidenspointner, Georg; Weierstall, Uwe; White, Thomas A; Wunderer, Cornelia; Chapman, Henry N; Ullrich, Joachim; Strüder, Lothar; Schlichting, Ilme

    2011-12-01

    X-ray free-electron lasers deliver intense femtosecond pulses that promise to yield high resolution diffraction data of nanocrystals before the destruction of the sample by radiation damage. Diffraction intensities of lysozyme nanocrystals collected at the Linac Coherent Light Source using 2 keV photons were used for structure determination by molecular replacement and analyzed for radiation damage as a function of pulse length and fluence. Signatures of radiation damage are observed for pulses as short as 70 fs. Parametric scaling used in conventional crystallography does not account for the observed effects. PMID:24089594

  1. Efficacy of Punch Elevation Combined with Fractional Carbon Dioxide Laser Resurfacing in Facial Atrophic Acne Scarring: A Randomized Split-face Clinical Study

    PubMed Central

    Faghihi, Gita; Nouraei, Saeid; Asilian, Ali; Keyvan, Shima; Abtahi-Naeini, Bahareh; Rakhshanpour, Mehrdad; Nilforoushzadeh, Mohammad Ali; Hosseini, Sayed Mohsen

    2015-01-01

    Background: A number of treatments for reducing the appearance of acne scars are available, but general guidelines for optimizing acne scar treatment do not exist. The aim of this study was to compare the clinical effectiveness and side effects of fractional carbon dioxide (CO2) laser resurfacing combined with punch elevation with fractional CO2 laser resurfacing alone in the treatment of atrophic acne scars. Materials and Methods: Forty-two Iranian subjects (age range 18–55) with Fitzpatrick skin types III to IV and moderate to severe atrophic acne scars on both cheeks received randomized split-face treatments: One side received fractional CO2 laser treatment and the other received one session of punch elevation combined with two sessions of laser fractional CO2 laser treatment, separated by an interval of 1 month. Two dermatologists independently evaluated improvement in acne scars 4 and 16 weeks after the last treatment. Side effects were also recorded after each treatment. Results: The mean ± SD age of patients was 23.4 ± 2.6 years. Clinical improvement of facial acne scarring was assessed by two dermatologists blinded to treatment conditions. No significant difference in evaluation was observed 1 month after treatment (P = 0.56). Their evaluation found that fractional CO2 laser treatment combined with punch elevation had greater efficacy than that with fractional CO2 laser treatment alone, assessed 4 months after treatment (P = 0.02). Among all side effects, coagulated crust formation and pruritus at day 3 after fractional CO2 laser treatment was significant on both treatment sides (P < 0.05). Conclusion: Concurrent use of fractional laser skin resurfacing with punch elevation offers a safe and effective approach for the treatment of acne scarring. PMID:26538695

  2. Radiation effects on DNA content of cervical cancer cells: A rapid evaluation of radiation sensitivity by laser scanning cytometry

    PubMed Central

    FUJIYOSHI, NAOKI; USHIJIMA, KIMIO; KAWANO, KOUICHIRO; FUJIYOSHI, KEIZO; YAMAGUCHI, TOMOHIKO; ARAKI, YUKO; KAKUMA, TATSUYUKI; WATANABE, SUMIKO; KAKU, TSUNEHISA; NISHIDA, TAKASHI; KAMURA, TOSHIHARU

    2015-01-01

    Since uterine cervical cancer is regarded as a radiosensive tumor, ionizing radiation is the most frequently used treatment modality against the disease. Although the crucial end-point is radiation-induced cell death, the tumors are not equally sensitive to radiation. Determining the criteria that may be used to predict tumor radiosensitivity is of importance; however, little success has been achieved thus far. In radioresistant cases the therapeutic strategy should be changed, thereby avoiding ineffective or unnecessary treatment. Furthermore, identification of the underlying molecular processes leading to radioresistance may lead to novel radiosensitising strategies. Cervical smears were obtained from seven patients with locally advanced cervical cancer following each radiotherapy, and the radiation-induced damage of cancer tissue was examined by routine cytology. Since the formation of DNA double-strand breaks is considered critical for the cytocidal effect of radiation therapy, the molecular changes of the neoplastic cells were also assessed by laser scanning cytometry (LSC). Radiation-induced morphological changes of cancer cells were evident at a dose of 7.2 Gy, whereas increased DNA content (or DNA index) was observed prior to the onset of morphological changes. Molecular change was detected earlier than the morphological change of the irradiated cancer cells, indicating the feasibility of LSC in predicting the radiosensitivity of cervical cancer tissue. PMID:25469269

  3. Removal of dental filling materials by Er:YAG laser radiation

    NASA Astrophysics Data System (ADS)

    Hibst, Raimund; Keller, Ulrich

    1991-05-01

    In previous reports it could be shown that pulsed Er:YAG laser radiation is effective for the removal of dental enamel, dentin, and caries. Damage to the adjacent hard substances is minimal. Temperature measurements and animal studies revealed that thermal pulp damage can be avoided. The experimental results make the Er:YAG laser promising for the preparation of dental cavities. In many cases patients already have fillings which have to be removed. In the present work, investigation is made of the effect of Er:YAG laser radiation on various restorative filling materials. The experiments demonstrate that removal is possible for all tested cements, composites and amalgam. Ablation efficiency is comparable to that of enamel and dentin, and thus sufficient for practical applications. Morphology of crater walls indicates greater thermal side effects than for natural dental hard substances.

  4. Enhanced X-ray radiation from laser wakefield acceleration transition to plasma wakefield acceleration

    NASA Astrophysics Data System (ADS)

    Dong, Chuanfei; Thomas, Alexander; Cummings, Paul; Krushelnick, Karl

    2015-11-01

    The electromagnetic fields responsible for Laser Wakefield Acceleration (LWFA) also cause electrons to radiate bright X-ray pulses though betatron oscillations. Using 3-D OSIRIS particle in cell simulations with a Monte Carlo synchrotron X-ray emission algorithm, the X-ray flux was also shown to increase dramatically for interaction distances beyond the dephasing length, where the main electron beams in the first ion bubble catch up the laser pulse front. Subsequently, it forms a secondary beam in the tail of the first bubble. Laser wakefield acceleration transitions to beam driven plasma wakefield acceleration, which results in the onset of the electron-hose instability and thus significantly enhances the X-ray radiation.

  5. In vitro effects of Nd:YAG laser radiation on blood: a quantitative and morphologic analysis

    SciTech Connect

    Borrero, E.; Rosenthal, D.; Otis, J.B.

    1988-01-01

    Use of the Neodymium: yttrium -aluminum -garnet (Nd:YAG) laser to recanalize stenosed arteries may require delivery of the beam through blood. To assess the degree of hemolysis and debris formation, 54 samples of citrated whole blood were exposed to Nd:YAG laser radiation of varying powers (10, 20 and 30 watts) and duration (1, 2.5 and 5 seconds). Compared to control samples which were not subjected to laser light, there was no significant decrease in hematocrit (41 to 40.5 +/- 5%), hemoglobin concentration (13.8 to 13.8 +/- .06 g/1OO ml), or increase in free hemoglobin concentration. Debris weight (from .45 +/- .002 to .45 +/- .002 mg), as well as the white blood cell count, was also not significantly changed (from 5,400 to 5,200 +/- 240 WBC/cm). Light microscopy examination of debris from samples of whole blood, washed erythrocytes, and platelet-rich plasma subjected to the laser at 30 watts for five seconds failed to demonstrate the presence of membrane denaturation of blood elements, as compared with the morphologic changes observed in whole blood samples exposed to a hot tip rather than Nd:YAG laser radiation. Nd:YAG laser can be used intravascularly without fear of hemolysis or debris micro-embolization up to a power of 30 watts for five seconds.

  6. High-Performance Carbon Monoxide Oxidation Catalysts Engineered for Carbon Dioxide Lasers

    NASA Astrophysics Data System (ADS)

    Gardner, Steven Dwayne

    1990-01-01

    The low-temperature CO oxidation activity of numerous materials has been evaluated in order to develop efficient catalysts for use in CO_2 lasers. The materials were screened for activity in small, stoichiometric concentrations of CO and O_2 at temperatures near 55^circC. An Au/MnO_{rm x} catalyst was synthesized which exhibited exceptional CO oxidation activity while maintaining negligible performance decay over a period of at least 70 days. The data suggest that Au/MnO_{rm x} has potential applications in air purification and CO gas sensing as well. Extensive surface characterization data from Pt/SnO _{rm x} and Au/MnO _{rm x} catalysts are reported which relate surface composition and chemical state information to corresponding CO oxidation activity data. Ion scattering spectroscopy (ISS), Auger electron spectroscopy (AES), angle-resolved Auger electron spectroscopy (ARAES) and X-ray photoelectron spectroscopy (XPS) were utilized to observe the behavior of these surfaces as a function of numerous pretreatments which alter their catalytic activity. The results suggest that Pt(OH)_2 and Pt/Sn alloy formation may play a key role in the CO oxidation mechanism on Pt/SnO_{ rm x} surfaces. A Pt_3 Sn alloy was subsequently characterized before and after H_2 reduction to study its surface characteristics. Surface characterization of Au/MnO_ {rm x} and MnO_{ rm x} was performed in order to elucidate the CO oxidation mechanism. The spectral data yield evidence that the enhanced CO oxidation activity of Au/MnO _{rm x} is related to Mn present primarily as Mn_3O _4 with substantial amounts of water or hydroxyl groups. The spectra are consistent with very small Au particles which may exist in an oxidized state. The behavior of Au/MnO_{rm x} and MnO_{rm x} toward an inert pretreatment suggests the possibility of a Au -MnO_{rm x} interaction.

  7. X-ray lasers - the ultimate radiation source?

    SciTech Connect

    Matthews, D.L.

    1995-12-31

    I will review the development of the x-ray laser from its first demonstration in 1984 to today`s systems which operate from 45 to 3.5 nm with output power levels up to GW and linewidths less than 10{sup -4}. At first, these sources required large pump laser facility in order to be produced, but just now new systems are appearing which are much more efficient and are near table-top in size. I will also discuss the future development of this source which should lead to wavelengths as short as 1 nm with a near-diffraction-limited output characteristics and considerable average output power, up to 10{sup 15} ph/sec. Finally, I will discuss some of the interesting applications such as in vitro biological imaging, microsurgery on microorganisms, construction of nanomachines, probing of semiconductors and plasmas, lithographic printing of semiconductor circuits and numerous other potential uses.

  8. Tissue ablation via optical fibre delivery of UV laser radiation

    NASA Astrophysics Data System (ADS)

    Miller, Joseph; Yu, Xiaobo; Yu, Paula K.; Cringle, Stephen J.; Yu, Dao-Yi

    2008-04-01

    We report the use of an ultraviolet (UV) laser and optical fibre arrangement capable of precise and controllable tissue ablation. The 5th (213nm) and 4th (266nm) harmonics of a Nd:YAG laser were launched into optical fibres using a hollow glass taper to concentrate the beam. Standard and modified silica/silica optical fibres were used, all commercially available. The available energy and fluence, as a function of optical fibre length, were evaluated and maximised. Single 5ns pulses were used to ablate both fresh porcine retina and in vivo rat trabecular meshwork. Fluences of 0.4 to 4.0 J/cm2 of 266nm and 0.2 to 1.0 J/cm2 of 213nm were used respectively. Thus demonstrating the potential use of this system for intraocular surgical applications.

  9. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Radiation emitted by a beam of particles crossing an inhomogeneous electromagnetic wave

    NASA Astrophysics Data System (ADS)

    Kol'tsov, A. V.; Serov, Alexander V.

    1995-03-01

    A theoretical investigation is made of the time dependence of the spatial distribution of particles injected perpendicular to the direction of propagation of a linearly polarised inhomogeneous electromagnetic wave and reflected by this wave. It is shown that such reflection modulates the particle density in a beam which is homogeneous at injection. Stimulated emission of radiation from a ribbon electron beam reflected by a wave is considered. The spectral—angular and polarisation characteristics of such radiation are investigated.

  10. Titanium dioxide thin films deposited by pulsed laser deposition and integration in radio frequency devices: Study of structure, optical and dielectric properties

    NASA Astrophysics Data System (ADS)

    Orlianges, Jean-Christophe; Crunteanu, Aurelian; Pothier, Arnaud; Merle-Mejean, Therese; Blondy, Pierre; Champeaux, Corinne

    2012-12-01

    Titanium dioxide presents a wide range of technological application possibilities due to its dielectric, electrochemical, photocatalytic and optical properties. The three TiO2 allotropic forms: anatase, rutile and brookite are also interesting, since they exhibit different properties, stabilities and growth modes. For instance, rutile has a high dielectric permittivity, of particular interest for the integration as dielectric in components such as microelectromechanical systems (MEMS) for radio frequency (RF) devices. In this study, titanium dioxide thin films are deposited by pulsed laser deposition. Characterizations by Raman spectroscopy and X-ray diffraction show the evolution of the structural properties. Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements from UV to IR range. Co-planar waveguide (CPW) devices are fabricated based on these films. Their performances are measured in the RF domain and compared to simulation, leading to relative permittivity values in the range 30-120, showing the potentialities of the deposited material for capacitive switches applications.

  11. Double shock front formation in cylindrical radiative blast waves produced by laser irradiation of krypton gas

    SciTech Connect

    Kim, I.; Quevedo, H. J.; Feldman, S.; Bang, W.; Serratto, K.; McCormick, M.; Aymond, F.; Dyer, G.; Bernstein, A. C.; Ditmire, T.

    2013-12-15

    Radiative blast waves were created by irradiating a krypton cluster source from a supersonic jet with a high intensity femtosecond laser pulse. It was found that the radiation from the shock surface is absorbed in the optically thick upstream medium creating a radiative heat wave that travels supersonically ahead of the main shock. As the blast wave propagates into the heated medium, it slows and loses energy, and the radiative heat wave also slows down. When the radiative heat wave slows down to the transonic regime, a secondary shock in the ionization precursor is produced. This paper presents experimental data characterizing both the initial and secondary shocks and numerical simulations to analyze the double-shock dynamics.

  12. Application of the 2-D discrete-ordinates method to multiple scattering of laser radiation

    SciTech Connect

    Zardecki, A.; Gerstl, S.A.W.; Embury, J.F.

    1983-05-01

    The discrete-ordinates finite-element radiation transport code twotran is applied to describe the multiple scattering of a laser beam from a reflecting target. For a model scenario involving a 99% relative humidity rural aerosol we compute the average intensity of the scattered radiation and correction factors to the Beer-Lambert law arising from multiple scattering. As our results indicate, 2-D x-y and r-z geometry modeling can reliably describe a realistic 3-D scenario. Specific results are presented for the two visual ranges of 1.52 and 0.76 km which show that, for sufficiently high aerosol concentrations (e.g., equivalent to V = 0.76 km), the target signature in a distant detector becomes dominated by multiply scattered radiation from interactions of the laser light with the aerosol environment. The merits of the scaling group and the delta-M approximation for the transfer equation are also explored.

  13. Two-dimensional modeling of multiply scattered laser radiation in optically dense aerosols

    SciTech Connect

    Zardecki, A.; Gerstl, S.A.W.; Embury, J.F.

    1982-01-01

    The discrete ordinates finite element radiation transport code TWOTRAN is applied to describe the multiple scattering of a laser beam from a reflecting target. For a model scenario involving a 99% relative humidity rural aerosol, we compute the average intensity of the scattered radiation and correction factors to the Lambert-Beer law arising from multiple scattering. As our results indicate, two-dimensional x-y and r-z geometry modeling can reliably describe a realistic three-dimensional scenario. Specific results are presented for the two visual ranges of 1.52 and 0.76 km which show that for sufficiently high aerosol concentrations (e.g., equivalent to V = 0.76 km) the target signature in a distant detector becomes dominated by multiply scattered radiation from interactions of the laser light with the aerosol environment.

  14. REVERSE RADIATIVE SHOCK LASER EXPERIMENTS RELEVANT TO ACCRETING STREAM-DISK IMPACT IN INTERACTING BINARIES

    SciTech Connect

    Krauland, C. M.; Drake, R. P.; Kuranz, C. C.; Huntington, C. M.; Kaczala, D. N.; Klein, S.; Sweeney, R.; Young, R. P.; Keiter, P. A.; Loupias, B.; Falize, E.; Villette, B.; Plewa, T. E-mail: rpdrake@umich.edu

    2013-01-01

    We present the first results from high-energy-density laboratory astrophysics experiments that explore the hydrodynamic and radiative properties of a reverse shock relevant to a cataclysmic variable system. A reverse shock is a shock wave that develops when a freely flowing, supersonic plasma is impeded. In our experiments, performed on the Omega Laser Facility, a laser pulse is used to accelerate plasma ejecta into a vacuum. This flow is directed into an Al plate in front of which a shock forms in the rebounding plasma. The plasma flow is moving fast enough that it is shocked to high enough temperatures that radiative cooling affects the shock structure. These are the first experiments to produce a radiative reverse shock wave.

  15. Laser beat wave excitation of terahertz radiation in a plasma slab

    SciTech Connect

    Chauhan, Santosh; Parashar, Jetendra

    2014-10-15

    Terahertz (THz) radiation generation by nonlinear mixing of lasers, obliquely incident on a plasma slab is investigated. Two cases are considered: (i) electron density profile is parabolic but density peak is below the critical density corresponding to the beat frequency, (ii) plasma boundaries are sharp and density is uniform. In both cases, nonlinearity arises through the ponderomotive force that gives rise to electron drift at the beat frequency. In the case of inhomogeneous plasma, non zero curl of the nonlinear current density gives rise to electromagnetic THz generation. In case of uniform plasma, the sharp density variation at the plasma boundaries leads to radiation generation. In a slab width of less than a terahertz wavelength, plasma density one fourth of terahertz critical density, laser intensities ∼10{sup 17 }W/cm{sup 2} at 1 μm, one obtains the THz intensity ∼1 GW/cm{sup 2} at 3 THz radiation frequency.

  16. Systems and methods for imaging using radiation from laser produced plasmas

    DOEpatents

    Renard-Le Galloudec, Nathalie; Cowan, Thomas E.; Sentoku, Yasuhiko; Rassuchine, Jennifer

    2009-06-30

    In particular embodiments, the present disclosure provides systems and methods for imaging a subject using radiation emitted from a laser produced plasma generating by irradiating a target with a laser. In particular examples, the target includes at least one radiation enhancing component, such as a fluor, cap, or wire. In further examples, the target has a metal layer and an internal surface defining an internal apex, the internal apex of less than about 15 .mu.m, such as less than about 1 .mu.m. The targets may take a variety of shapes, including cones, pyramids, and hemispheres. Certain aspects of the present disclosure provide improved imaging of a subject, such as improved medical images of a radiation dose than typical conventional methods and systems.

  17. EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Measurements of laser-induced shock waves in aluminium

    NASA Astrophysics Data System (ADS)

    Werdiger, M.; Arad, B.; Moshe, E.; Eliezer, S.

    1995-02-01

    A simple optical method for measurements of high-irradiance (3×1013 W cm-2) laser-induced shock waves is described. The shock wave velocity (~13 km s-1) was measured with an error not exceeding 5%. The laser-induced one-to-two-dimensional (1D-to-2D) shock wave transition was studied.

  18. Change of electrical conductivity of Ar welding arc under resonant absorption of laser radiation

    NASA Astrophysics Data System (ADS)

    Kozakov, R.; Emde, B.; Pipa, A. V.; Huse, M.; Uhrlandt, D.; Hermsdorf, J.; Wesling, V.

    2015-03-01

    Experimental investigations of the impact of resonant laser absorption by a tungsten inert gas welding arc in argon are presented. The intensity increase of the arc’s radiation between the laser entrance height and the anode are observed, as well as the variation of arc voltage due to the presence of the laser beam. High-speed camera recordings from different directions combined with absolutely calibrated spectroscopic measurements allow the reconstruction of the three-dimensional emission coefficient profiles without the assumption of axial symmetry. The obtained data are evaluated within the framework of local thermodynamic equilibrium. The local increase in the temperature and conductivity due to the influence of the laser is determined. Changes in the electrical conductivity obtained from the optical measurements coincide well with the measured voltage drop, and show significant redistribution of the current density profile near the anode in particular.

  19. 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)

  20. Beam characteristics of a large-bore copper laser with a radiatively cooled plasma

    SciTech Connect

    Chang, J.J.; Boley, C.D.; Molander, W.A.; Warner, B.E.; Martinez, M.W.

    1994-01-18

    In a large-bore copper vapor laser (CVL), excessive gas heating at the axial region of the discharge lowers its efficiency by thermally populating the metastable lower laser levels. The associated lower gas density also lengthens the discharge field-diffusion time, leading to weaker axial pumping and undesired beam characteristics. The authors` laboratory has developed a novel approach to circumvent this obstacle by cooling the plasma radiatively via a series of segmented metal plates (septa) placed vertically along the length of the tube. This improved tube design significantly lowers the average gas temperature and shortens the radial delay. A 27% increase in laser power was observed with the addition of septa. The authors have characterized the beam intensity profile, spatial and temporal pulse variation, and beam polarization through extensive laboratory measurements. A detailed computational model of the laser has been used to characterize and interpret the laboratory results.